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Sample records for santorini greece magma

  1. Forecasting magma-chamber rupture at Santorini volcano, Greece.

    Science.gov (United States)

    Browning, John; Drymoni, Kyriaki; Gudmundsson, Agust

    2015-10-28

    How much magma needs to be added to a shallow magma chamber to cause rupture, dyke injection, and a potential eruption? Models that yield reliable answers to this question are needed in order to facilitate eruption forecasting. Development of a long-lived shallow magma chamber requires periodic influx of magmas from a parental body at depth. This redistribution process does not necessarily cause an eruption but produces a net volume change that can be measured geodetically by inversion techniques. Using continuum-mechanics and fracture-mechanics principles, we calculate the amount of magma contained at shallow depth beneath Santorini volcano, Greece. We demonstrate through structural analysis of dykes exposed within the Santorini caldera, previously published data on the volume of recent eruptions, and geodetic measurements of the 2011-2012 unrest period, that the measured 0.02% increase in volume of Santorini's shallow magma chamber was associated with magmatic excess pressure increase of around 1.1 MPa. This excess pressure was high enough to bring the chamber roof close to rupture and dyke injection. For volcanoes with known typical extrusion and intrusion (dyke) volumes, the new methodology presented here makes it possible to forecast the conditions for magma-chamber failure and dyke injection at any geodetically well-monitored volcano.

  2. Reconstruction of the paleo-coastline of Santorini island (Greece ...

    Indian Academy of Sciences (India)

    history, changing dramatically the life of the people of the Bronze age in the eastern Mediterranean. Basin. It also changed the morphology of the island itself, creating the famous ..... Friedrich W 2001 Fire in the Sea. The Santorini Volcano:.

  3. Living the Volcano: A First-Year Study Abroad Experience to Santorini, Greece

    Science.gov (United States)

    Skinner, L. A.; Miller, M.; Scarnati, B.

    2014-12-01

    Over the last decade, enrollment in Northern Arizona University's (NAU) Geologic Disasters (GLG112) class has grown to its current 840 students in 7 sections per semester (4% of NAU enrollment). Given this large audience composed of >50% freshmen, the course curriculum was re-designed in 2012 using standards set by NAU's First Year Learning Initiative (FYLI), which seeks to increase academic success early in college. FYLI pedagogical principles include active-learning, frequent feedback, low-stakes assessments, and increased guidance from professors & peer teaching assistants (PTAs). As a result of the successes measured in FYLI courses, we launched a FYLI study abroad experience in 2014. We posed the question, "How can an early-career study abroad experience further develop the attitudes, skills, & behaviors necessary for success?" The pioneering program was NAU in Greece: The Cataclysmic Eruption of Santorini Volcano. Enrollment was limited to freshman & sophomore students who have taken GLG112 (or equivalent). The 3-week program took 9 students, 1 PTA, & 1 faculty member to Santorini (via Athens, 2 days). A detailed itinerary addressed a set of disciplinary & non-disciplinary learning outcomes. Student learning about Santorini volcano and the tectonic setting & hazards of the Aegean Sea occurred on the go - on ferries & private boat trips and during hiking, snorkeling, and swimming. Classroom time was limited to 1 hr/day and frequent assessments were employed. Student products included a geologic field notebook, travel journal, and 3 blog posts pertaining to geologic hazards & life on Santorini. Geologic disasters are ideal topics for early career study abroad experiences because the curriculum is place-based. Student learning benefits immensely from interacting with the land & local populations, whose lives are affected daily by the dangers of living in such geologically hazardous environments. The needs of early career students are unique, however, and must be

  4. Olive tree-ring problematic dating: a comparative analysis on Santorini (Greece.

    Directory of Open Access Journals (Sweden)

    Paolo Cherubini

    Full Text Available Olive trees are a classic component of Mediterranean environments and some of them are known historically to be very old. In order to evaluate the possibility to use olive tree-rings for dendrochronology, we examined by various methods the reliability of olive tree-rings identification. Dendrochronological analyses of olive trees growing on the Aegean island Santorini (Greece show that the determination of the number of tree-rings is impossible because of intra-annual wood density fluctuations, variability in tree-ring boundary structure, and restriction of its cambial activity to shifting sectors of the circumference, causing the tree-ring sequences along radii of the same cross section to differ.

  5. Olive tree-ring problematic dating: a comparative analysis on Santorini (Greece).

    Science.gov (United States)

    Cherubini, Paolo; Humbel, Turi; Beeckman, Hans; Gärtner, Holger; Mannes, David; Pearson, Charlotte; Schoch, Werner; Tognetti, Roberto; Lev-Yadun, Simcha

    2013-01-01

    Olive trees are a classic component of Mediterranean environments and some of them are known historically to be very old. In order to evaluate the possibility to use olive tree-rings for dendrochronology, we examined by various methods the reliability of olive tree-rings identification. Dendrochronological analyses of olive trees growing on the Aegean island Santorini (Greece) show that the determination of the number of tree-rings is impossible because of intra-annual wood density fluctuations, variability in tree-ring boundary structure, and restriction of its cambial activity to shifting sectors of the circumference, causing the tree-ring sequences along radii of the same cross section to differ.

  6. The PROTEUS Experiment: Active Source Seismic Imaging of the Crustal Magma Plumbing Structure of the Santorini Arc Volcano

    Science.gov (United States)

    Hooft, E. E. E.; Morgan, J. V.; Nomikou, P.; Toomey, D. R.; Papazachos, C. V.; Warner, M.; Heath, B.; Christopoulou, M. E.; Lampridou, D.; Kementzetzidou, D.

    2016-12-01

    The goal of the PROTEUS seismic experiment (Plumbing Reservoirs Of The Earth Under Santorini) is to examine the entire crustal magma plumbing system beneath a continental arc volcano and determine the magma geometry and connections throughout the crust. These physical parameters control magma migration, storage, and eruption and inform the question of how physical and chemical processing of magma at arc volcanoes forms the andesitic rock compositions that dominate the lower continental crust. These physical parameters are also important to understand volcanic-tectonic interactions and geohazards. Santorini is ideal for these goals because the continental crust has been thinned by extension and so the deep magmatic system is more accessible, also it is geologically well studied. Since the volcano is a semi-submerged, it was possible to collect a unique 3D marine-land active source seismic dataset. During the PROTEUS experiment in November-December of 2015, we recorded 14,300 marine sound sources from the US R/V Langseth on 89 OBSIP short period ocean bottom seismometers and 60 German and 5 Greek land seismometers. The experiment was designed for high-density spatial sampling of the seismic wavefield to allow us to apply two state-of-the-art 3D inversion methods: travel time tomography and full waveform inversion. A preliminary travel time tomography model of the upper crustal seismic velocity structure of the volcano and surrounding region is presented in an accompanying poster. We also made marine geophysical maps of the seafloor using multi-beam bathymetry and of the gravity and magnetic fields. The new seafloor map reveals the detailed structure of the major fault system between Santorini and Amorgos, of associated landslides, and of newly discovered volcanic features. The PROTEUS project will provide new insights into the structure of the whole crustal magmatic system of a continental arc volcano and its evolution within the surrounding tectonic setting.

  7. Evidence from cosmic ray exposure (CRE) dating for the existence of a pre-Minoan caldera on Santorini, Greece

    Science.gov (United States)

    Athanassas, C. D.; Bourlès, D. L.; Braucher, R.; Druitt, T. H.; Nomikou, P.; Léanni, L.

    2016-05-01

    Cosmic ray exposure (CRE) dating was performed on the caldera cliffs of Santorini with the aim of detecting cliff segments predating the Minoan eruption (17th century BCE). The methodology involved the determination of in situ-produced cosmogenic 36Cl concentration in basaltic-to-rhyodacitic whole rocks cropping out in the cliffs. After the samples were processed following the chemical protocol of 36Cl preparation for silicate rocks, 36Cl concentrations were measured by accelerator mass spectrometry (AMS). Important challenges during the implementation procedure were related to large amounts of radiogenic 36Cl, complex modeling of inherited 36Cl, and dominance of the thermal and epithermal (low-energy) neutron capture production pathway. Nevertheless, quantitative assessments on the basis of the contribution of the low-energy neutron capture pathway percent to the total production rate validated the calculated CRE dates. Current CRE ages demonstrate that an ancient caldera existed on pre-Minoan Santorini, occupying at least the northern half of the modern-day caldera.

  8. Expanding extension, subsidence and lateral segmentation within the Santorini - Amorgos basins during Quaternary: Implications for the 1956 Amorgos events, central - south Aegean Sea, Greece

    Science.gov (United States)

    Nomikou, P.; Hübscher, C.; Papanikolaou, D.; Farangitakis, G. P.; Ruhnau, M.; Lampridou, D.

    2018-01-01

    New bathymetric and seismic reflection data from the Santorini-Amorgos Tectonic Zone in the southern Cyclades have been analysed and a description of the morphology and tectonic structure of the area has been presented. The basins of Anhydros, Amorgos and Santorini-Anafi have been distinguished together with the intermediate Anhydros Horst within the NE-SW oriented Santorini-Amorgos Tectonic Zone which has a length of 60-70 km and a width of 20-25 km. The basins represent tectonic grabens or semi-grabens bordered by the active marginal normal faults of Santorini-Anafi, Amorgos, Ios, Anhydros and Astypalaea. The Santorini-Anafi, Amorgos and Ios marginal faults have their footwall towards the NW where Alpine basement occurs in the submarine scarps and their hangingwall towards the southeast, where the Quaternary sediments have been deposited with maximum thickness of 700 m. Six sedimentary Units 1-6 have been distinguished in the stratigraphic successions of the Santorini-Anafi and the western Anhydros Basin whereas in the rest area only the upper four Units 3-6 have been deposited. This shows the expansion of the basin with subsidence during the Quaternary due to ongoing extension in a northwest-southeast direction. Growth structures are characterized by different periods of maximum deformation as this is indicated by the different sedimentary units with maximum thickness next to each fault. Transverse structures of northwest-southeast direction have been identified along the Santorini-Amorgos Tectonic Zone with distinction of the blocks/segments of Santorini, Anhydros/Kolumbo, Anhydros islet and Amorgos. Recent escarpments with 7-9 m offset observed along the Amorgos Fault indicate that this was activated during the first earthquake of the 7.5 magnitude 1956 events whereas no recent landslide was found in the area that could be related to the 1956 tsunami.

  9. 3D upper crustal seismic structure across Santorini volcanic field: Constraints on magmatic and tectonic interactions

    Science.gov (United States)

    Heath, B.; Hooft, E. E. E.; Toomey, D. R.; Papazachos, C. V.; Walls, K.; Paulatto, M.; Morgan, J. V.; Nomikou, P.; Warner, M.

    2017-12-01

    To investigate magmatic-tectonic interactions at an arc volcano, we collected a dense, active-source, seismic dataset across the Santorini Volcano, Greece, with 90 ocean bottom seismometers, 65 land seismometers, and 14,300 marine sound sources. We use over 140,000 travel-time picks to obtain a P-wave tomography model of the upper crustal structure of the Santorini volcano and surrounding tectonically extended region. Regionally, the shallow (Bouguer gravity anomalies and preliminary shallow attenuation results (using waveform amplitudes and t* values). We find regional Pliocene and younger faults bounding basement grabens and horsts to be predominately oriented in a NE-SW direction with Santorini itself located in a graben bounded by faults striking in this direction. In contrast, volcanic vents and dikes expressed at the surface seem to strike about 20° clockwise relative to these regional faults. In the northern caldera of Santorini, a 4-km wide region of anomalously low velocities and high attenuation directly overlies an inferred source of 2011-2012 inflation (4-4.5 km depth), however it is located at shallower depths ( 1-2km). The imaged low-velocity anomaly may correspond to hydrothermal activity (due to increased porosity and alteration) and/or brecciation from a prior episode of caldera collapse. It is bounded by anomalously fast velocities (at 1-2 km depth) that parallel the regional fault orientation and are correspondingly rotated 20° to surface dikes. At 4-5 km depth beneath the northern caldera basin, low-velocity anomalies and attenuated seismic arrivals provide preliminary evidence for a magma body; the low-velocity anomaly is elongated in the same direction as regional volcanic vents. The difference in strike of volcanic and tectonic features indicates oblique extension and potential time-variation in the minimum stress direction.

  10. Perceptions of hazard and risk on Santorini

    Science.gov (United States)

    Dominey-Howes, Dale; Minos-Minopoulos, Despina

    2004-10-01

    Santorini, Greece is a major explosive volcano. The Santorini volcanic complex is composed of two active volcanoes—Nea Kameni and Mt. Columbo. Holocene eruptions have generated a variety of processes and deposits and eruption mechanisms pose significant hazards of various types. It has been recognized that, for major European volcanoes, few studies have focused on the social aspects of volcanic activity and little work has been conducted on public perceptions of hazard, risk and vulnerability. Such assessments are an important element of establishing public education programmes and developing volcano disaster management plans. We investigate perceptions of volcanic hazards on Santorini. We find that most residents know that Nea Kameni is active, but only 60% know that Mt. Columbo is active. Forty percent of residents fear that negative impacts on tourism will have the greatest effect on their community. In the event of an eruption, 43% of residents would try to evacuate the island by plane/ferry. Residents aged >50 have retained a memory of the effects of the last eruption at the island, whereas younger residents have no such knowledge. We find that dignitaries and municipal officers (those responsible for planning and managing disaster response) are informed about the history, hazards and effects of the volcanoes. However, there is no "emergency plan" for the island and there is confusion between various departments (Civil Defense, Fire, Police, etc.) about the emergency decision-making process. The resident population of Santorini is at high risk from the hazards associated with a future eruption.

  11. SANTORINI BEFORE THE MINOAN ERUPTION

    DEFF Research Database (Denmark)

    Friedrich, Walter L.; Sørensen, Annette Højen; Katsipis, Samson

    2014-01-01

    Conclusions Several detailed geological observations in the landscape of Santorini enable us to claim that the two harbour towns were located on the inner side of the caldera wall on the island of Thera prior to the Minoan Eruption. This hypothesis is in agreement with the excavation sites of Bal...... that the fresco shows a joyful scene where the inhabitants of Bronze Age Santorini celebrate the seasonal change in connection with the arrival of life-giving rainwater either at the beginning of spring or at the end of the sailing season in autumn (Pl. CXLVIIc)....

  12. Magma evolution in the Pliocene Pleistocene succession of Kos, South Aegean arc (Greece)

    Science.gov (United States)

    Pe-Piper, Georgia; Moulton, Ben

    2008-11-01

    This study investigates the petrogenesis of Pliocene-Quaternary andesites, dacites and rhyolites of the island of Kos. These volcanic rocks differ from other volcanic centres in the South Aegean arc in the narrow range of Pliocene volcanic products, the abundance of high-silica rhyolite, the lower ɛNd for a given Sr isotope composition, and greater depth to the subducting slab. Pliocene and early Pleistocene dacite stocks and rhyolite domes are succeeded by younger tuffs, notably the 0.16 Ma Kos Plateau Tuff derived from a super-eruption of an andesite stratocone now subsided beneath the sea south of Kos. Volcanic products in tuffs have been sampled from lithic clasts. Andesite, dacite and rhyolite all have ɛNd ˜+ 1.5 to -1.5 and 86Sr/ 87Sr ˜ 0.7042; this unusual composition is argued to be the result of subduction of sediments derived from the River Nile. All rock types show structures indicative of widespread magma mixing, including complexly zoned plagioclase, clinopyroxene and amphibole containing glass inclusions of trachyte and rhyolite compositions. The observed rocks result from fractionation and mixing of three principal magma types: (a) calc-alkaline high-Al basalt that fractionated to andesite at the base of crust; (b) partially melted metabasaltic amphibolite underplated at the base of crust, that fractionated to produce high-SiO 2 rhyolite; and (c) a minor component of trachytic magma from partial melting of enriched subcontinental lithospheric mantle. The complexly zoned phenocrysts with glass inclusions provide specific evidence for mixing of these three components. Specifically, it was the emplacement of the andesite into a voluminous rhyolite magma in a mid-crustal magma chamber that led to the explosive Kos Plateau Tuff super-eruption.

  13. Formation of heterogeneous magmatic series beneath North Santorini, South Aegean island arc

    DEFF Research Database (Denmark)

    Bailey, John C; Jensen, E.S.; Hansen, A.

    2008-01-01

    magma formation beneath North Santorini throughout its 500 ka history is attributed to variable transfer of sedimentary components - either terrigenous or pelagic, as bulk sediments or high-temperature partial melts rather than fluids or low-temperature partial melts - from a rupture zone...... in the subducted slab to the overlying mantle. The three main magmatic series followed independent paths of assimilation of upper crustal materials during fractional crystallization. Assimilation was more pronounced at the basaltic stage. The long-lived histories of the three main magmatic series imply repetitive...... melting of isolated mantle regions, ascent of magmas through independent feeder systems, and their residence in separate crustal magma chambers....

  14. Greece.

    Science.gov (United States)

    1985-04-01

    A brief description of the population characteristics, geographical features, history, current political situation, economy, energy supply, foreign relations of Greece is presented. Greece's population of 9.95 million is 98% Greek, and the official language is Greek. 97% of the population is Greek Orthodox, and 2% is Muslim. Schooling is compulsory for 9 years, and the literacy rate is 89% for women and 96% for men. The infant mortality rate is 13.8, and life expectancy is 72 years for males and 75 years for female. Greece is situated on the southern tip of the Balkan Peninsula and consists of the mainland, the Peleponnesos, and numerous islands including Crete. Most of the land mass is mountainous, large areas are dry, and only 28% of the land is arable. From the earliest time until recently, emigration from Greece to other countries was a common pattern. Since the 1960s, internal migration to urban areas was the dominant migration trend. Currently, 30% of the population lives in Athens. Despite the growing industrialization and urbanization of the population, the Greeks retain many traditional family and social values. Greece was part of the cradle of civilization, and its history is characterized by the rise of the Minoan culture on Crete, the rise and fall of the Myceneans on the Peleponnesos, the development of the city states of Athens and Sparta, the destruction of Athens during the Peloponnesian War, domination by the Macedonians, the creation of the Hellenistic cilivization, conquest by the Roman Empire, the establishment of the Byzantine Empire, and in 1459 conquest by the Ottoman Empire. In the 1820's Greece fought for and finally won its independence, In World War I Greece fought on the side of the Allies. In World War II, the Greeks successfully resisted an invasion from Italy. In 1941, the country was taken over by the Germans, but the Greek resistance movement continued to fight the Germans until liberation. Between 1944-49, there were 2 unsuccessful

  15. Santorini eruption radiocarbon dated to 1627-1600 B.C.

    Science.gov (United States)

    Friedrich, Walter L; Kromer, Bernd; Friedrich, Michael; Heinemeier, Jan; Pfeiffer, Tom; Talamo, Sahra

    2006-04-28

    Precise and direct dating of the Minoan eruption of Santorini (Thera) in Greece, a global Bronze Age time marker, has been made possible by the unique find of an olive tree, buried alive in life position by the tephra (pumice and ashes) on Santorini. We applied so-called radiocarbon wiggle-matching to a carbon-14 sequence of tree-ring segments to constrain the eruption date to the range 1627-1600 B.C. with 95.4% probability. Our result is in the range of previous, less precise, and less direct results of several scientific dating methods, but it is a century earlier than the date derived from traditional Egyptian chronologies.

  16. Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano.

    Science.gov (United States)

    Druitt, T H; Costa, F; Deloule, E; Dungan, M; Scaillet, B

    2012-02-01

    Caldera-forming volcanic eruptions are low-frequency, high-impact events capable of discharging tens to thousands of cubic kilometres of magma explosively on timescales of hours to days, with devastating effects on local and global scales. Because no such eruption has been monitored during its long build-up phase, the precursor phenomena are not well understood. Geophysical signals obtained during recent episodes of unrest at calderas such as Yellowstone, USA, and Campi Flegrei, Italy, are difficult to interpret, and the conditions necessary for large eruptions are poorly constrained. Here we present a study of pre-eruptive magmatic processes and their timescales using chemically zoned crystals from the 'Minoan' caldera-forming eruption of Santorini volcano, Greece, which occurred in the late 1600s BC. The results provide insights into how rapidly large silicic systems may pass from a quiescent state to one on the edge of eruption. Despite the large volume of erupted magma (40-60 cubic kilometres), and the 18,000-year gestation period between the Minoan eruption and the previous major eruption, most crystals in the Minoan magma record processes that occurred less than about 100 years before the eruption. Recharge of the magma reservoir by large volumes of silicic magma (and some mafic magma) occurred during the century before eruption, and mixing between different silicic magma batches was still taking place during the final months. Final assembly of large silicic magma reservoirs may occur on timescales that are geologically very short by comparison with the preceding repose period, with major growth phases immediately before eruption. These observations have implications for the monitoring of long-dormant, but potentially active, caldera systems.

  17. Evolution of silicic magmas in the Kos-Nisyros volcanic center, Greece: a petrological cycle associated with caldera collapse

    Science.gov (United States)

    Bachmann, Olivier; Deering, Chad D.; Ruprecht, Janina S.; Huber, Christian; Skopelitis, Alexandra; Schnyder, Cedric

    2012-01-01

    Multiple eruptions of silicic magma (dacite and rhyolites) occurred over the last ~3 My in the Kos-Nisyros volcanic center (eastern Aegean sea). During this period, magmas have changed from hornblende-biotite-rich units with low eruption temperatures (≤750-800°C; Kefalos and Kos dacites and rhyolites) to hotter, pyroxene-bearing units (>800-850°C; Nisyros rhyodacites) and are transitioning back to cooler magmas (Yali rhyolites). New whole-rock compositions, mineral chemistry, and zircon Hf isotopes show that these three types of silicic magmas followed the same differentiation trend: they all evolved by crystal fractionation and minor crustal assimilation (AFC) from parents with intermediate compositions characterized by high Sr/Y and low Nb content, following a wet, high oxygen fugacity liquid line of descent typical of subduction zones. As the transition between the Kos-Kefalos and Nisyros-type magmas occurred immediately and abruptly after the major caldera collapse in the area (the 161 ka Kos Plateau Tuff; KPT), we suggest that the efficient emptying of the magma chamber during the KPT drew out most of the eruptible, volatile-charged magma and partly solidified the unerupted mush zone in the upper crust due to rapid unloading, decompression, and coincident crystallization. Subsequently, the system reestablished a shallow silicic production zone from more mafic parents, recharged from the mid to lower crust. The first silicic eruptions evolving from these parents after the caldera collapse (Nisyros units) were hotter (up to >100°C) than the caldera-forming event and erupted from reservoirs characterized by different mineral proportions (more plagioclase and less amphibole). We interpret such a change as a reflection of slightly drier conditions in the magmatic column after the caldera collapse due to the decompression event. With time, the upper crustal intermediate mush progressively transitioned into the cold-wet state that prevailed during the Kefalos

  18. Isotope geochemistry of recent magmatism in the Aegean arc: Sr, Nd, Hf, and O isotopic ratios in the lavas of Milos and Santorini-geodynamic implications

    Science.gov (United States)

    Briqueu, L.; Javoy, M.; Lancelot, J.R.; Tatsumoto, M.

    1986-01-01

    In this comparative study of variations in the isotopic compositions (Sr, Nd, O and Hf) of the calc-alkaline magmas of the largest two volcanoes, Milos and Santorini, of the Aegean arc (eastern Mediterranean) we demonstrate the complexity of the processes governing the evolution of the magmas on the scale both of the arc and of each volcano. On Santorini, the crustal contamination processes have been limited, effecting the magma gradually during its differentiation. The most differentiated lavas (rhyodacite and pumice) are also the most contaminated. On Milos, by contrast, these processes are very extensive. They are expressed in the 143Nd/144Nd vs. 87Sr/86Sr diagram as a continuous mixing curve between a mantle and a crustal end member pole defined by schists and metavolcanic rocks outcropping on these volcanoes. In contrast with Santorini, the least differentiated lavas on Milos are the most contaminated. These isotopic singularities can be correlated with the geodynamic evolution of the Aegean subduction zone, consisting of alternating tectonic phases of distension and compression. The genesis of rhyolitic magmas can be linked to the two phases of distension, and the contamination of the calc-alkaline mantle-derived magmas with the intermediate compressive phase. The isotopic characteristics of uncontaminated calc-alkaline primitive magmas of Milos and Santorini are directly comparable to those of magmas generated in subduction zones for which a contribution of subducted sediments to partial melts from the mantle is suggested, such as in the Aleutian, Sunda, and lesser Antilles island arcs. However, in spite of the importance of the sediment pile in the eastern Mediterranen oceanic crust (6-10 km), the contribution of the subducted terrigenous materials remains of limited amplitude. ?? 1986.

  19. A new species of Berinda (Araneae, Gnaphosidae from the eastern Aegean Islands, Greece

    Directory of Open Access Journals (Sweden)

    Lissner, Jørgen

    2016-04-01

    Full Text Available A new ground spider, Berinda idae Lissner spec. nov. is described from material collected in Kalymnos and Nisyros of the Dodecanese Islands, as well as Santorini and Christiani of the Thira island complex, Cyclades, Greece. The affinity of this species to ist congeners is briefly discussed.

  20. Santorini Volcano's 20th Century Eruptions: A Combined Petrogenetical, Volcanological, Sociological and Environmental Study

    Science.gov (United States)

    Drymoni, Kyriaki; Magganas, Andreas; Pomonis, Panagiotis

    2014-05-01

    Santorini, the famous stratovolcano in the Aegean Sea, erupted three time periods during the 20th century (1925-1928, 1939-1941, 1950) and since then remains dormant. This study tried to combine and evaluate new and published volcanological, petrological, geochemical, environmental and sociological data of these three phases of Santorini's activity, which practically restricted to the caldera center on the Nea Kameni Islet. After field work on the formed dacite flows, pyroclastics and domes, representative rock samples and enclaves were collected and investigated for their texture, physical parameters, mineralogy and chemical composition by polarizing light microscope, scanning electron microscope (SEM-EDS), XRD, Raman spectroscopy and ICP-MS. The petrogenetic evaluation of the data obtained suggests slight but significant changes in the solid and aerial phases produced during the three explosion stages, which can be attributed to minor variations in the magmatic differentiation and magma chamber physicochemical conditions. These variations were also expressed by decrease of duration and intensity of the eruptions, as well as in their volume of ejecta and lava. Probably, the subsequent relatively long dormant period of the volcano is also related to this tension of decrease. The first compared results were collected from scientific literature, old photos as well as local and regional press and state documents from the different periods of volcanism, record the past hazard case scenarios and civil defense planning of the individual eruptions. As part of the disaster management a pilot survey, in which personal interviews with aged local islanders that were eye-witnesses of the events and elderly people or tourists that they indirectly experienced or have heard about them, was also conducted. This event-tracing, along with air pollution software models using volcanological data have shown the social impacts and the environmental consequences of the volcanic

  1. Geoarchaeological tsunami deposits at Palaikastro (Crete) and the Late Minoan IA eruption of Santorini

    NARCIS (Netherlands)

    Bruins, Hendrik J.; MacGillivray, J. Alexander; Synolakis, Costas E.; Benjamini, Chaim; Keller, Joerg; Kisch, Hanan J.; Kleugel, Andreas; van der Plicht, Johannes; Klügel, Andreas

    The explosive eruption at Santorini in the Aegean Sea during the second millennium BCE was the largest Holocene volcanic upheaval in the Eastern Mediterranean region. The eruption was disastrous for the Minoan settlements at Santorini, but the effect on human society in the neighbouring islands and

  2. Exploring for geothermal resources in Greece

    Energy Technology Data Exchange (ETDEWEB)

    Mendrinos, Dimitrios; Choropanitis, Ioannis; Polyzou, Olympia; Karytsas, Constantine [Centre for Renewable Energy Sources and Saving (CRES), 19th km Marathon Avenue, 19009 Pikermi (Greece)

    2010-03-15

    In Greece the geothermal areas are located in regions of Quaternary or Miocene volcanism and in continental basins of high heat flow. The existence of high-temperature (>200 C) resources has been proven by deep drilling on the islands of Milos and Nisyros and inferred on the island of Santorini by its active volcanism. Elsewhere, geological investigations, geochemical analyses of thermal springs and shallow drilling have identified many low-temperature (<100 C) reservoirs, utilized for spas and greenhouse/soil heating. Ternary K-Na-Mg geothermometer data suggest deep, medium-temperature resources (100-200 C) in Sousaki, the islands of Samothraki, Chios and Lesvos, in the basins of Nestos River Delta and Alexandroupolis and in the graben of Sperchios River. In the basins of northern Greece these resources are also inferred from deep oil exploration well data. (author)

  3. Film tourism and destination marketing : a case study of Santorini, Greece

    OpenAIRE

    Ραυτοπούλου, Μαρία

    2014-01-01

    Like books and paintings, which are the channels that have inspired us to fantasize on travelling to new and exotic places, films are the modern motivators of today that can through moving image make us value to visit certain places (Beeton 2005, 4). For some it can be a form of escapism or pilgrimage and for many these places are the connection between real and imaginary. By depicting a particular place in a film, we can claim it will certainly stimulate in our interest towards traditional t...

  4. The most direct and precise radiocarbon date for the Minoan eruption of Santorini

    DEFF Research Database (Denmark)

    Friedrich, Walter L.; Heinemeier, Jan

    for the Minoan eruption. Together with a second olive tree, excavated only 9 meters from the first one, it enables us to repeat the earlier measurements of the first tree 2006 (Friedrich, W.L . Kromer, B Friedrich, M. Heinemeier, J. Pfeiffer, T. Talamo, S. Santorini Eruption Radiocarbon Dated to 1627-1600 BC...

  5. A geochemical study of Nea-Kameni hyalodacites (Santorini Volcano, Aegean island arc). Inferences concerning the origin and effects of solfataras and magmatic evolution

    Science.gov (United States)

    Briqueu, Louis; Lancelot, Joël R.

    1984-03-01

    Since the Santorini Volcano (Aegean arc, eastern Mediterranean Sea) collapsed, volcanic activity has been located at the center of the flooded caldera. Over the past 800 years, five lava flows have formed one of the central islets (Nea-Kameni). Since 1951, when the last eruption occurred, a permanent fumarolic activity has remained. We present chemical analyses (major elements, trace-elements and Sr isotopic ratios) of ten samples from the five hyalodacitic lava flows, showing different stages of alteration, from a completely fresh lava up to one bearing native sulfur and other sublimates. Only the macroscopic aspect of these hyalodacites is affected by fumarolic activity. The elements that are mobile as a result of hydrothermal processes, such as the alkaline (K, Rb) or the chalcophile elements (Zn, Pb), show great homogeneity; the same can be said for the Sr isotopic compositions which range from 0.7046 to 0.7049. None of the analyzed samples has an Sr isotopic composition as high as those reported by Puchelt and Hoefs (1971) for rock samples collected in the same lava flows. If we take into account the marine surroundings of Nea-Kameni islet, these observations put severe restraints on the different hypotheses regarding the origin of the halogens (seawater or meteoric water). The contamination processes of these dacitic lavas are clearly less important than assumed by other authors according to previous Sr isotopic data. Finally, the homogeneity of the elements with low partition coefficients is sufficient to show that the magma has not undergone any perceptible evolution during the last 300 years.

  6. The Meaning of "Magma"

    Science.gov (United States)

    Bartley, J. M.; Glazner, A. F.; Coleman, D. S.

    2016-12-01

    Magma is a fundamental constituent of the Earth, and its properties, origin, evolution, and significance bear on issues ranging from volcanic hazards to planetary evolution. Unfortunately, published usages indicate that the term "magma" means distinctly different things to different people and this can lead to miscommunication among Earth scientists and between scientists and the public. Erupting lava clearly is magma; the question is whether partially molten rock imaged at depth and too crystal-rich to flow should also be called magma. At crystal fractions > 50%, flow can only occur via crystal deformation and solution-reprecipitation. As the solid fraction increases to 90% or more, the material becomes a welded crystal framework with melt in dispersed pores and/or along grain boundaries. Seismic images commonly describe such volumes of a few % melt as magma, yet the rheological differences between melt-rich and melt-poor materials make it vital not to confuse a large rock volume that contains a small melt fraction with melt-rich material. To ensure this, we suggest that "magma" be reserved for melt-rich materials that undergo bulk fluid flow on timescales consonant with volcanic eruptions. Other terms should be used for more crystal-rich and largely immobile partially molten rock (e.g., "crystal mush," "rigid sponge"). The distinction is imprecise but useful. For the press, the public, and even earth scientists who do not study magmatic systems, "magma" conjures up flowing lava; reports of a large "magma" body that contains a few percent melt can engender the mistaken perception of a vast amount of eruptible magma. For researchers, physical processes like crystal settling are commonly invoked to account for features in plutonic rocks, but many such processes are only possible in melt-rich materials.

  7. Ancient pests: the season of the Santorini Minoan volcanic eruption and a date from insect chitin

    Science.gov (United States)

    Panagiotakopulu, Eva; Higham, Thomas; Sarpaki, Anaya; Buckland, Paul; Doumas, Christos

    2013-07-01

    Attributing a season and a date to the volcanic eruption of Santorini in the Aegean has become possible by using preserved remains of the bean weevil, Bruchus rufipes, pests of pulses, from the storage jars of the West House, in the Bronze Age settlement at Akrotiri. We have applied an improved pre-treatment methodology for dating the charred insects, and this provides a date of 1744-1538 BC. This date is within the range of others obtained from pulses from the same context and confirms the utility of chitin as a dating material. Based on the nature of the insect material and the life cycle of the species involved, we argue for a summer eruption, which took place after harvest, shortly after this material was transported into the West House storeroom.

  8. Tree ring and ice core time scales around the Santorini eruption

    Science.gov (United States)

    Löfroth, Elin; Muscheler, Raimund; Aldahan, Ala; Possnert, Göran; Berggren, Ann-Marie

    2010-05-01

    When studying cosmogenic radionuclides in ice core and tree ring archives around the Santorini eruption a ~20 year discrepancy was found between the records (Muscheler 2009). In this study a new 10Be dataset from the NGRIP ice core is presented. It has a resolution of 7 years and spans the period 3752-3244 BP (1803-1295 BC). The NGRIP 10Be record and the previously published 10Be GRIP record were compared to the IntCal datasets to further investigate the discrepancy between the ice core and tree ring chronologies. By modelling the 14C production rate based on atmospheric 14C records a comparison could be made to the 10Be flux which is assumed to represent the 10Be production rate. This showed a time shift of ~23 years between the records. The sensitivity of the results to changes in important model parameters was evaluated. Uncertainties in the carbon cycle model cannot explain a substantial part of the timing differences. Potential influences of climate and atmospheric processes on the 10Be deposition were studied using δ18O from the respective cores and GISP2 ice core ion data. The comparison to δ18O revealed a small but significant correlation between 10Be flux and δ18O when the 14C-derived production signal was removed from the 10Be curves. The ion data, as proxies for atmospheric circulation changes, did not show any correlations to the 10Be record or the 10Be/14C difference. When including possible data uncertainties there is still a minimum discrepancy of ~10 years between the 10Be ice core and the 14C tree ring record. Due to lack of alternative explanations it is concluded that the ice core and/or the tree ring chronologies contains unaccounted errors in this range. This also reconciles the radiocarbon 1627-1600 BC (Friedrich et al., 2006) and ice core 1642±5 BC (Vinther et al., 2006) datings of the Santorini eruption. Friedrich, W.L., Kromer, B., Friedrich, M., Heinemeier, J., Pfeiffer, T., & Talamo, S., 2006: Santorini eruption radiocarbon dated to

  9. Post-eruptive flooding of Santorini caldera and implications for tsunami generation

    Science.gov (United States)

    Nomikou, P.; Druitt, T. H.; Hübscher, C.; Mather, T. A.; Paulatto, M.; Kalnins, L. M.; Kelfoun, K.; Papanikolaou, D.; Bejelou, K.; Lampridou, D.; Pyle, D. M.; Carey, S.; Watts, A. B.; Weiß, B.; Parks, M. M.

    2016-01-01

    Caldera-forming eruptions of island volcanoes generate tsunamis by the interaction of different eruptive phenomena with the sea. Such tsunamis are a major hazard, but forward models of their impacts are limited by poor understanding of source mechanisms. The caldera-forming eruption of Santorini in the Late Bronze Age is known to have been tsunamigenic, and caldera collapse has been proposed as a mechanism. Here, we present bathymetric and seismic evidence showing that the caldera was not open to the sea during the main phase of the eruption, but was flooded once the eruption had finished. Inflow of water and associated landsliding cut a deep, 2.0–2.5 km3, submarine channel, thus filling the caldera in less than a couple of days. If, as at most such volcanoes, caldera collapse occurred syn-eruptively, then it cannot have generated tsunamis. Entry of pyroclastic flows into the sea, combined with slumping of submarine pyroclastic accumulations, were the main mechanisms of tsunami production. PMID:27824353

  10. Mush Column Magma Chambers

    Science.gov (United States)

    Marsh, B. D.

    2002-12-01

    Magma chambers are a necessary concept in understanding the chemical and physical evolution of magma. The concept may well be similar to a transfer function in circuit or time series analysis. It does what needs to be done to transform source magma into eruptible magma. In gravity and geodetic interpretations the causative body is (usually of necessity) geometrically simple and of limited vertical extent; it is clearly difficult to `see' through the uppermost manifestation of the concentrated magma. The presence of plutons in the upper crust has reinforced the view that magma chambers are large pots of magma, but as in the physical representation of a transfer function, actual magma chambers are clearly distinct from virtual magma chambers. Two key features to understanding magmatic systems are that they are vertically integrated over large distances (e.g., 30-100 km), and that all local magmatic processes are controlled by solidification fronts. Heat transfer considerations show that any viable volcanic system must be supported by a vertically extensive plumbing system. Field and geophysical studies point to a common theme of an interconnected stack of sill-like structures extending to great depth. This is a magmatic Mush Column. The large-scale (10s of km) structure resembles the vertical structure inferred at large volcanic centers like Hawaii (e.g., Ryan et al.), and the fine scale (10s to 100s of m) structure is exemplified by ophiolites and deeply eroded sill complexes like the Ferrar dolerites of the McMurdo Dry Valleys, Antarctica. The local length scales of the sill reservoirs and interconnecting conduits produce a rich spectrum of crystallization environments with distinct solidification time scales. Extensive horizontal and vertical mushy walls provide conditions conducive to specific processes of differentiation from solidification front instability to sidewall porous flow and wall rock slumping. The size, strength, and time series of eruptive behavior

  11. The Surtsey Magma Series.

    Science.gov (United States)

    Schipper, C Ian; Jakobsson, Sveinn P; White, James D L; Michael Palin, J; Bush-Marcinowski, Tim

    2015-06-26

    The volcanic island of Surtsey (Vestmannaeyjar, Iceland) is the product of a 3.5-year-long eruption that began in November 1963. Observations of magma-water interaction during pyroclastic episodes made Surtsey the type example of shallow-to-emergent phreatomagmatic eruptions. Here, in part to mark the 50(th) anniversary of this canonical eruption, we present previously unpublished major-element whole-rock compositions, and new major and trace-element compositions of sideromelane glasses in tephra collected by observers and retrieved from the 1979 drill core. Compositions became progressively more primitive as the eruption progressed, with abrupt changes corresponding to shifts between the eruption's four edifices. Trace-element ratios indicate that the chemical variation is best explained by mixing of different proportions of depleted ridge-like basalt, with ponded, enriched alkalic basalt similar to that of Iceland's Eastern Volcanic Zone; however, the systematic offset of Surtsey compositions to lower Nb/Zr than other Vestmannaeyjar lavas indicates that these mixing end members are as-yet poorly contained by compositions in the literature. As the southwestern-most volcano in the Vestmannaeyjar, the geochemistry of the Surtsey Magma Series exemplifies processes occurring within ephemeral magma bodies on the extreme leading edge of a propagating off-axis rift in the vicinity of the Iceland plume.

  12. Lunar magma transport phenomena

    Science.gov (United States)

    Spera, Frank J.

    1992-01-01

    An outline of magma transport theory relevant to the evolution of a possible Lunar Magma Ocean and the origin and transport history of the later phase of mare basaltic volcanism is presented. A simple model is proposed to evaluate the extent of fractionation as magma traverses the cold lunar lithosphere. If Apollo green glasses are primitive and have not undergone significant fractionation en route to the surface, then mean ascent rates of 10 m/s and cracks of widths greater than 40 m are indicated. Lunar tephra and vesiculated basalts suggest that a volatile component plays a role in eruption dynamics. The predominant vapor species appear to be CO CO2, and COS. Near the lunar surface, the vapor fraction expands enormously and vapor internal energy is converted to mixture kinetic energy with the concomitant high-speed ejection of vapor and pyroclasts to form lunary fire fountain deposits such as the Apollo 17 orange and black glasses and Apollo 15 green glass.

  13. Comparative Magma Oceanography

    Science.gov (United States)

    Jones, J. H.

    1999-01-01

    The question of whether the Earth ever passed through a magma ocean stage is of considerable interest. Geochemical evidence strongly suggests that the Moon had a magma ocean and the evidence is mounting that the same was true for Mars. Analyses of martian (SNC) meteorites have yielded insights into the differentiation history of Mars, and consequently, it is interesting to compare that planet to the Earth. Three primary features of Mars contrast strongly to those of the Earth: (i) the extremely ancient ages of the martian core, mantle, and crust (about 4.55 b.y.); (ii) the highly depleted nature of the martian mantle; and (iii) the extreme ranges of Nd isotopic compositions that arise within the crust and depleted mantle. The easiest way to explain the ages and diverse isotopic compositions of martian basalts is to postulate that Mars had an early magma ocean. Cumulates of this magma ocean were later remelted to form the SNC meteorite suite and some of these melts assimilated crustal materials enriched in incompatible elements. The REE pattern of the crust assimilated by these SNC magmas was LREE enriched. If this pattern is typical of the crust as a whole, the martian crust is probably similar in composition to melts generated by small degrees of partial melting (about 5%) of a primitive source. Higher degrees of partial melting would cause the crustal LREE pattern to be essentially flat. In the context of a magma ocean model, where large degrees of partial melting presumably prevailed, the crust would have to be dominated by late-stage, LREE-enriched residual liquids. Regardless of the exact physical setting, Nd and W isotopic evidence indicates that martian geochemical reservoirs must have formed early and that they have not been efficiently remixed since. The important point is that in both the Moon and Mars we see evidence of a magma ocean phase and that we recognize it as such. Several lines of theoretical inference point to an early Earth that was also hot

  14. Radon measurements in Greece

    International Nuclear Information System (INIS)

    Georgiou, E.; Ntalles, K.; Molfetas, M.; Athanassiadis, A.; Proukakis, C.

    1988-01-01

    Studies of radon concentration in greek spas, in a cave, in constituents of the greek cement, in building materials in Greece and in greek mines have been published. Some preliminary studies of radon concentration in greek dwellings have been published. In order to get an idea of the problem in Greece we decided to carry out a national survey. Two different sites were selected: Athens, where domicile about 40% of the greek population and Domatia, a small village in northern Greece 600Km from Athens, located in an area known to have soil with increased uranium concentrations

  15. 14C dating of the Early to Late Bronze Age stratigraphic sequence of Aegina Kolonna, Greece

    International Nuclear Information System (INIS)

    Wild, E.M.; Gauss, W.; Forstenpointner, G.; Lindblom, M.; Smetana, R.; Steier, P.; Thanheiser, U.; Weninger, F.

    2010-01-01

    Aegina Kolonna, located in the center of the Saronic Gulf in the Aegean Mediterranean (Greece), is one of the major archaeological sites of the Aegean Bronze Age with a continuous stratigraphic settlement sequence from the Late Neolithic to the Late Bronze Age. Due to its position next to the maritime cross roads between central mainland Greece, the northeast Peloponnese, the Cyclades and Crete, the island played an important role in the trade between these regions. In the course of new excavations, which focused on the exploration of the Early, Middle and Late Bronze Age at Kolonna, several short lived samples from different settlement phases have been 14 C-dated with the AMS method at the VERA laboratory. Bayesian sequencing of the 14 C data according to the stratigraphic position of the samples in the profile was performed to enable estimates of the transition time between the cultural phases. The Aegina Kolonna 14 C sequence is one of the longest existing so far for the Aegean Bronze Age, and therefore of major importance for the absolute Bronze Age chronology in this region. Preliminary results indicate that the Middle Helladic period seems to have started earlier and lasted longer than traditionally assumed. Further, at the present stage of our investigation we can give also a very tentative time frame for the Santorini volcanic eruption which seems to be in agreement with the science derived VDL date.

  16. Superheat in magma oceans

    Science.gov (United States)

    Jakes, Petr

    1992-01-01

    The existence of 'totally molten' planets implies the existence of a superheat (excess of heat) in the magma reservoirs since the heat buffer (i.e., presence of crystals having high latent heat of fusion) does not exist in a large, completely molten reservoir. Any addition of impacting material results in increase of the temperature of the melt and under favorable circumstances heat is stored. The behavior of superheat melts is little understood; therefore, we experimentally examined properties and behavior of excess heat melts at atmospheric pressures and inert gas atmosphere. Highly siliceous melts (70 percent SiO2) were chosen for the experiments because of the possibility of quenching such melts into glasses, the slow rate of reaction in highly siliceous composition, and the fact that such melts are present in terrestrial impact craters and impact-generated glasses. Results from the investigation are presented.

  17. Pathology in Greece.

    Science.gov (United States)

    Sakellariou, S; Patsouris, E

    2015-11-01

    Pathology is the field of medicine that studies diseases. Ancient Greece hosted some of the earliest societies that laid the structural foundations of pathology. Initially, knowledge was based on observations but later on the key elements of pathology were established based on the dissection of animals and the autopsy of human cadavers. Christianized Greece under Ottoman rule (1453-1821) was not conducive to the development of pathology. After liberation, however, a series of events took place that paved the way for the establishment and further development of the specialty. The appointment in 1849 of two Professors of Pathology at the Medical School of Athens for didactical purposes proved to be the most important step in fostering the field of pathology in modern Greece. Presently in Greece there are seven university departments and 74 pathology laboratories in public hospitals, employing 415 specialized pathologists and 90 residents. The First Department of Pathology at the Medical School of Athens University is the oldest (1849) and largest in Greece, encompassing most pathology subspecialties.

  18. Numerical modeling of magma-repository interactions

    NARCIS (Netherlands)

    Bokhove, Onno

    2001-01-01

    This report explains the numerical programs behind a comprehensive modeling effort of magma-repository interactions. Magma-repository interactions occur when a magma dike with high-volatile content magma ascends through surrounding rock and encounters a tunnel or drift filled with either a magmatic

  19. Greece joins IPPOG as member

    CERN Document Server

    Marcelloni, Claudia

    2018-01-01

    Dr. Patricia Kyprianidou, Secretary General for Research and Technology of Greece, signed the IPPOG MOU on behalf of Greece on 24 of May, 2018 in Athens. Christine Kourkoumelis, former representative of Greece in IPPOG handed over the documents to the IPPOG chairs, Hans Peter Beck and Steve Goldfarb and was present during a signature ceremony at CERN on 19 of June 2018. The current representative of Greece in IPPOG is Nicholas Tracas. IPPOG chairs would also like to thank Costas Foudas, delegate of Greece to the CERN council, for his support.

  20. Magma emplacement in 3D

    Science.gov (United States)

    Gorczyk, W.; Vogt, K.

    2017-12-01

    Magma intrusion is a major material transfer process in Earth's continental crust. Yet, the mechanical behavior of the intruding magma and its host are a matter of debate. In this study, we present a series of numerical thermo-mechanical experiments on mafic magma emplacement in 3D.In our model, we place the magmatic source region (40 km diameter) at the base of the mantle lithosphere and connect it to the crust by a 3 km wide channel, which may have evolved at early stages of magmatism during rapid ascent of hot magmatic fluids/melts. Our results demonstrate continental crustal response due to magma intrusion. We observe change in intrusion geometries between dikes, cone-sheets, sills, plutons, ponds, funnels, finger-shaped and stock-like intrusions as well as injection time. The rheology and temperature of the host-rock are the main controlling factors in the transition between these different modes of intrusion. Viscous deformation in the warm and deep crust favours host rock displacement and magma pools along the crust-mantle boundary forming deep-seated plutons or magma ponds in the lower to middle-crust. Brittle deformation in the cool and shallow crust induces cone-shaped fractures in the host rock and enables emplacement of finger- or stock-like intrusions at shallow or intermediate depth. A combination of viscous and brittle deformation forms funnel-shaped intrusions in the middle-crust. Low-density source magma results in T-shaped intrusions in cross-section with magma sheets at the surface.

  1. Ceramic analysis in Greece

    NARCIS (Netherlands)

    Hilditch, J.

    2016-01-01

    Scientific, analytical or ‘archaeometric’ techniques for investigating ceramic material have been used within archaeology for over 50 years and now constitute an indispensable tool for archaeologists in the Aegean world (see Jones 1986 for a detailed summary of early work in Greece and Italy) and

  2. Weak solutions of magma equations

    International Nuclear Information System (INIS)

    Krishnan, E.V.

    1999-01-01

    Periodic solutions in terms of Jacobian cosine elliptic functions have been obtained for a set of values of two physical parameters for the magma equation which do not reduce to solitary-wave solutions. It was also obtained solitary-wave solutions for another set of these parameters as an infinite period limit of periodic solutions in terms of Weierstrass and Jacobian elliptic functions

  3. Magma flow through elastic-walled dikes

    NARCIS (Netherlands)

    Bokhove, Onno; Woods, A.W.; de Boer, A

    2005-01-01

    A convection–diffusion model for the averaged flow of a viscous, incompressible magma through an elastic medium is considered. The magma flows through a dike from a magma reservoir to the Earth’s surface; only changes in dike width and velocity over large vertical length scales relative to the

  4. Caldera resurgence driven by magma viscosity contrasts.

    Science.gov (United States)

    Galetto, Federico; Acocella, Valerio; Caricchi, Luca

    2017-11-24

    Calderas are impressive volcanic depressions commonly produced by major eruptions. Equally impressive is the uplift of the caldera floor that may follow, dubbed caldera resurgence, resulting from magma accumulation and accompanied by minor eruptions. Why magma accumulates, driving resurgence instead of feeding large eruptions, is one of the least understood processes in volcanology. Here we use thermal and experimental models to define the conditions promoting resurgence. Thermal modelling suggests that a magma reservoir develops a growing transition zone with relatively low viscosity contrast with respect to any newly injected magma. Experiments show that this viscosity contrast provides a rheological barrier, impeding the propagation through dikes of the new injected magma, which stagnates and promotes resurgence. In explaining resurgence and its related features, we provide the theoretical background to account for the transition from magma eruption to accumulation, which is essential not only to develop resurgence, but also large magma reservoirs.

  5. Partially molten magma ocean model

    International Nuclear Information System (INIS)

    Shirley, D.N.

    1983-01-01

    The properties of the lunar crust and upper mantle can be explained if the outer 300-400 km of the moon was initially only partially molten rather than fully molten. The top of the partially molten region contained about 20% melt and decreased to 0% at 300-400 km depth. Nuclei of anorthositic crust formed over localized bodies of magma segregated from the partial melt, then grew peripherally until they coverd the moon. Throughout most of its growth period the anorthosite crust floated on a layer of magma a few km thick. The thickness of this layer is regulated by the opposing forces of loss of material by fractional crystallization and addition of magma from the partial melt below. Concentrations of Sr, Eu, and Sm in pristine ferroan anorthosites are found to be consistent with this model, as are trends for the ferroan anorthosites and Mg-rich suites on a diagram of An in plagioclase vs. mg in mafics. Clustering of Eu, Sr, and mg values found among pristine ferroan anorthosites are predicted by this model

  6. Greece Experience of International Tourism

    Directory of Open Access Journals (Sweden)

    Beslan V. Labzhaniya

    2012-05-01

    Full Text Available Tourism offers a real opportunity to invite investments, decline unemployment and increase production, which will help to overcome crisis and come to sustainable development, badly needed for Greece now.

  7. Gender Wage Differentials in Greece

    OpenAIRE

    Evangelia Papapetrou

    2004-01-01

    The paper studies the existence of wage differentials between male and female employees in Greece employing quantile regession analysis techniques and applying a variant of the selection-adjusted Oaxaca and Ransom (1994) decomposition method to explain the components of the wage differentials. The results suggest that, in Greece, differences in wages between men and women can be identified. Decomposing the wage gap between genders, the results show that the difference in wages is attributed m...

  8. Interaction of coeval felsic and mafic magmas from the Kanker ...

    Indian Academy of Sciences (India)

    66

    20 crystallization of the latter, results in hybrid magmas under the influence of thermal and. 21 chemical exchange. The mechanical exchange occurs between the coexisting magmas due to. 22 viscosity contrast, if the mafic magma enters slightly later into the magma chamber, when the. 23 felsic magma started to crystallize.

  9. Depth of origin of magma in eruptions.

    Science.gov (United States)

    Becerril, Laura; Galindo, Ines; Gudmundsson, Agust; Morales, Jose Maria

    2013-09-26

    Many volcanic hazard factors--such as the likelihood and duration of an eruption, the eruption style, and the probability of its triggering large landslides or caldera collapses--relate to the depth of the magma source. Yet, the magma source depths are commonly poorly known, even in frequently erupting volcanoes such as Hekla in Iceland and Etna in Italy. Here we show how the length-thickness ratios of feeder dykes can be used to estimate the depth to the source magma chamber. Using this method, accurately measured volcanic fissures/feeder-dykes in El Hierro (Canary Islands) indicate a source depth of 11-15 km, which coincides with the main cloud of earthquake foci surrounding the magma chamber associated with the 2011-2012 eruption of El Hierro. The method can be used on widely available GPS and InSAR data to calculate the depths to the source magma chambers of active volcanoes worldwide.

  10. Volcanic emission of radionuclides and magma dynamics

    International Nuclear Information System (INIS)

    Lambert, G.; Le Cloarec, M.F.; Ardouin, B.; Le Roulley, J.C.

    1985-01-01

    210 Pb, 210 Bi and 210 Po, the last decay products of the 238 U series, are highly enriched in volcanic plumes, relative to the magma composition. Moreover this enrichment varies over time and from volcano to volcano. A model is proposed to describe 8 years of measurements of Mt. Etna gaseous emissions. The lead and bismuth coefficients of partition between gaseous and condensated phases in the magma are determined by comparing their concentrations in lava flows and condensated volatiles. In the case of volatile radionuclides, an escaping time is calculated which appears to be related to the volcanic activity. Finally, it is shown that that magma which is degassing can already be partly degassed; it should be considered as a mixture of a few to 50% of deep non-degassed magma with a well degassed superficial magma cell. (orig.)

  11. Shear thinning behaviors in magmas

    Science.gov (United States)

    Vetere, F. P.; Cassetta, M.; Perugini, D.

    2017-12-01

    Studies on magma rheology are of fundamental importance to understanding magmatic processes from depth to surface. Since viscosity is one of the most important parameter controlling eruption mechanisms, as well as lava flow emplacement, a comprehensive knowledge on the evolution of magma viscosities during crystallization is required. We present new viscosity data on partly crystalized basalt, andesite and analogue lavas comparable to those erupted on Mercury's northern volcanic plains. High-temperature viscosity measurements were performed using a rotational Anton Paar RheolabQC viscometer head at the PVRG labs, in Perugia (Italy) (http://pvrg.unipg.it). The relative proportion of phases in each experimental run were determined by image analysis on BS-SEM images at different magnifications; phases are glasses, clinopyroxene, spinel, plagioclase for the basalt, plagioclase and spinel for the andesite and pure enstatite and clinopyroxenes, for the analogue Mercury's composition. Glass and crystalline fractions determined by image analysis well correlate with compositions of residual melts. In order to constrain the viscosity (η) variations as a function of crystallinity, shear rate (γ) was varied from 0.1 to 5 s-1. Viscosity vs. time at constant temperature shows a typical S-shape curve. In particular, for basaltic composition η vary from 3.1-3.8 Pa s [log η] at 1493 K and crystallinity of 19 area % as γ vary from 1.0 to 0.1 s-1; the andesite viscosity evolution is 3.2 and 3.7 Pa s [log η] as γ varies from 1 to 0.1 at 1493 K and crystal content of 17 area %; finally, Mercury's analogue composition was investigated at different temperature ranging from 1533 to 1502 K (Vetere et al., 2017). Results, for γ = 0.1, 1.0 and 5.0 s-1, show viscosity variation between 2.7-4.0, 2.5-3.4 and 2.0-3.0 [log η inPa s] respectively while crystallinity vary from 9 to 27 (area %). As viscosity decreases as shear rate increases, these data points to a shear thinning behaviour

  12. Electricity sector reform in Greece

    International Nuclear Information System (INIS)

    Iliadou, Ekaterini N.

    2009-01-01

    This paper provides an outlook of the electricity market reform in Greece which started in 2001 and is still developing slowly. This is related to the persisting dominance of the incumbent company and the specificities of the electricity sector of Greece which is heavily dependent on indigenous lignite firing generation, while being located in the periphery of the EU internal electricity and gas markets. Competition through enhancing electricity trade in the region is limited to date, as the establishment of an internal market in South East Europe also progresses slowly. Development of competition through gas-firing generation by new entrants has been the priority adopted by State and Regulator's policies. However, the gas supply market in Greece and in the region still lags behind. (author)

  13. The Presence of Ancient Greece in Modern Greece

    Science.gov (United States)

    Anton, John P.

    1977-01-01

    The author relates the ways in which a present day visitor to Greece will be reminded of ancient Greek history. The legendary hospitality, Greek statues, the landscape, Greek dances, gestures, and customs are some of the topics discussed. (Author/RM)

  14. Numerical modeling of bubble dynamics in magmas

    Science.gov (United States)

    Huber, Christian; Su, Yanqing; Parmigiani, Andrea

    2014-05-01

    Understanding the complex non-linear physics that governs volcanic eruptions is contingent on our ability to characterize the dynamics of bubbles and its effect on the ascending magma. The exsolution and migration of bubbles has also a great impact on the heat and mass transport in and out of magma bodies stored at shallow depths in the crust. Multiphase systems like magmas are by definition heterogeneous at small scales. Although mixture theory or homogenization methods are convenient to represent multiphase systems as a homogeneous equivalent media, these approaches do not inform us on possible feedbacks at the pore-scale and can be significantly misleading. In this presentation, we discuss the development and application of bubble-scale multiphase flow modeling to address the following questions : How do bubbles impact heat and mass transport in magma chambers ? How efficient are chemical exchanges between the melt and bubbles during magma decompression? What is the role of hydrodynamic interactions on the deformation of bubbles while the magma is sheared? Addressing these questions requires powerful numerical methods that accurately model the balance between viscous, capillary and pressure stresses. We discuss how these bubble-scale models can provide important constraints on the dynamics of magmas stored at shallow depth or ascending to the surface during an eruption.

  15. Evidence for seismogenic fracture of silicic magma.

    Science.gov (United States)

    Tuffen, Hugh; Smith, Rosanna; Sammonds, Peter R

    2008-05-22

    It has long been assumed that seismogenic faulting is confined to cool, brittle rocks, with a temperature upper limit of approximately 600 degrees C (ref. 1). This thinking underpins our understanding of volcanic earthquakes, which are assumed to occur in cold rocks surrounding moving magma. However, the recent discovery of abundant brittle-ductile fault textures in silicic lavas has led to the counter-intuitive hypothesis that seismic events may be triggered by fracture and faulting within the erupting magma itself. This hypothesis is supported by recent observations of growing lava domes, where microearthquake swarms have coincided with the emplacement of gouge-covered lava spines, leading to models of seismogenic stick-slip along shallow shear zones in the magma. But can fracturing or faulting in high-temperature, eruptible magma really generate measurable seismic events? Here we deform high-temperature silica-rich magmas under simulated volcanic conditions in order to test the hypothesis that high-temperature magma fracture is seismogenic. The acoustic emissions recorded during experiments show that seismogenic rupture may occur in both crystal-rich and crystal-free silicic magmas at eruptive temperatures, extending the range of known conditions for seismogenic faulting.

  16. Examining shear processes during magma ascent

    Science.gov (United States)

    Kendrick, J. E.; Wallace, P. A.; Coats, R.; Lamur, A.; Lavallée, Y.

    2017-12-01

    Lava dome eruptions are prone to rapid shifts from effusive to explosive behaviour which reflects the rheology of magma. Magma rheology is governed by composition, porosity and crystal content, which during ascent evolves to yield a rock-like, viscous suspension in the upper conduit. Geophysical monitoring, laboratory experiments and detailed field studies offer the opportunity to explore the complexities associated with the ascent and eruption of such magmas, which rest at a pivotal position with regard to the glass transition, allowing them to either flow or fracture. Crystal interaction during flow results in strain-partitioning and shear-thinning behaviour of the suspension. In a conduit, such characteristics favour the formation of localised shear zones as strain is concentrated along conduit margins, where magma can rupture and heal in repetitive cycles. Sheared magmas often record a history of deformation in the form of: grain size reduction; anisotropic permeable fluid pathways; mineral reactions; injection features; recrystallisation; and magnetic anomalies, providing a signature of the repetitive earthquakes often observed during lava dome eruptions. The repetitive fracture of magma at ( fixed) depth in the conduit and the fault-like products exhumed at spine surfaces indicate that the last hundreds of meters of ascent may be controlled by frictional slip. Experiments on a low-to-high velocity rotary shear apparatus indicate that shear stress on a slip plane is highly velocity dependent, and here we examine how this influences magma ascent and its characteristic geophysical signals.

  17. Environmental radioactivity monitoring in Greece

    International Nuclear Information System (INIS)

    Maltezos, A.; Potiriadis, C.; Aravantinos, A.

    1997-01-01

    Greek Atomic Energy Commission (GAEC) is the national organization responsible for the environmental radioactivity measurements in Greece. In order to monitor the radioactivity, 12 stations were placed all over Greece. Each station is equipped with NaI detector, measuring daily the total gamma dose rates. After the Chernobyl experience many countries have installed dense automatic networks, for measuring environmental radioactivity and serving as an early warning systems. In Greece a small telemetric network of two stations was installed in Athens area as a pilot project. Each station consists of two GM detectors (for low and high dose rate respectively). Data are collected for every ten minutes sampling time. Regration time of one hour is obtained. In case of level one and level two alarm states, the sampling time intervals are ten and one minutes respectively. The measurements are obtained by the above stations using the lines of the telephone network, and stored in the central station. Financial support to upgrade the existing telemetric system was assured by the addition of 25 new telemetric stations which will cover madly the northern part bordering to other states with nuclear power plants.In order to complete the network, we plan to add more stations to measure the gamma dose rates spread all over Greece, and also monitor river water. (authors)

  18. Mass chest radiography in Greece

    International Nuclear Information System (INIS)

    Papavasiliou, C.

    1987-01-01

    In Greece mass chest radiography has been performed regularly on various population groups as a measure to control tuberculosis. Routine chest radiography is performed in most Greek hospitals on admission. In this report available data-admittedly inadequate-directly or indirectly addressing the problem of benefit versus the risk or cost associated with this examination is presented

  19. On some Chiroptera from Greece

    NARCIS (Netherlands)

    Laar, van Vincent; Daan, Serge

    1964-01-01

    On a trip to Greece between the 25th April and the 25th July 1963, the authors collected (on the mainland and some islands in the Aegean) insects, amphibians and reptiles as well as 194 mammals. Among the mammals, mainly rodents and insectivores, there were also 27 bats, belonging to five species.

  20. School Building Organisation in Greece.

    Science.gov (United States)

    PEB Exchange, 2001

    2001-01-01

    Discusses the past and current organizational structure of Greece's School Building Organisation, a body established to work with government agencies in the design and construction of new buildings and the provisioning of educational equipment. Future planning to incorporate culture and creativity, sports, and laboratory learning in modern school…

  1. Comments on 'Generation of Deccan Trap magmas'

    Indian Academy of Sciences (India)

    R.Narasimhan(krishtel emaging)1461 1996 Oct 15 13:05:22

    Comments on 'Generation of Deccan Trap magmas' by Gautam Sen ... Department of Geology & Geophysics, School of Ocean & Earth Science & Technology (SOEST), University of .... Mahoney J J, Sheth H C, Chandrasekharan D and Peng Z.

  2. The Boycott effect in magma chambers

    Science.gov (United States)

    Blanchette, F.; Peacock, T.; Bush, J. W. M.

    2004-03-01

    We investigate the plausibility of the stratified Boycott effect as a source of layering in magma chambers. Crystal settling within the magma chamber will generate buoyant fluid near the sloping sidewalls whose vertical ascent may be limited by the ambient stratification associated with vertical gradients in SiO2. The resulting flow may be marked by a layered structure, each layer taking the form of a convection cell spanning the lateral extent of the magma chamber. Using parameters relevant to magma chambers, we estimate that such convection cells would be established over a timescale of a month and have a depth on the order of 4m, which is roughly consistent with field observations of strata within solidified chambers.

  3. Magma Chambers, Thermal Energy, and the Unsuccessful Search for a Magma Chamber Thermostat

    Science.gov (United States)

    Glazner, A. F.

    2015-12-01

    Although the traditional concept that plutons are the frozen corpses of huge, highly liquid magma chambers ("big red blobs") is losing favor, the related notion that magma bodies can spend long periods of time (~106years) in a mushy, highly crystalline state is widely accepted. However, analysis of the thermal balance of magmatic systems indicates that it is difficult to maintain a significant portion in a simmering, mushy state, whether or not the system is eutectic-like. Magma bodies cool primarily by loss of heat to the Earth's surface. The balance between cooling via energy loss to the surface and heating via magma accretion can be denoted as M = ρLa/q, where ρ is magma density, L is latent heat of crystallization, a is the vertical rate of magma accretion, and q is surface heat flux. If M>1, then magma accretion outpaces cooling and a magma chamber forms. For reasonable values of ρ, L, and q, the rate of accretion amust be > ~15 mm/yr to form a persistent volume above the solidus. This rate is extremely high, an order of magnitude faster than estimated pluton-filling rates, and would produce a body 10 km thick in 700 ka, an order of magnitude faster than geochronology indicates. Regardless of the rate of magma supply, the proportion of crystals in the system must vary dramatically with depth at any given time owing to transfer of heat. Mechanical stirring (e.g., by convection) could serve to homogenize crystal content in a magma body, but this is unachievable in crystal-rich, locked-up magma. Without convection the lower part of the magma body becomes much hotter than the top—a process familiar to anyone who has scorched a pot of oatmeal. Thermal models that succeed in producing persistent, large bodies of magma rely on scenarios that are unrealistic (e.g., omitting heat loss to the planet's surface), self-fulfilling prophecies (e.g., setting unnaturally high temperatures as fixed boundary conditions), or physically unreasonable (e.g., magma is intruded

  4. Silicic magma generation at Askja volcano, Iceland

    Science.gov (United States)

    Sigmarsson, O.

    2009-04-01

    Rate of magma differentiation is an important parameter for hazard assessment at active volcanoes. However, estimates of these rates depend on proper understanding of the underlying magmatic processes and magma generation. Differences in isotope ratios of O, Th and B between silicic and in contemporaneous basaltic magmas have been used to emphasize their origin by partial melting of hydrothermally altered metabasaltic crust in the rift-zones favoured by a strong geothermal gradient. An alternative model for the origin of silicic magmas in the Iceland has been proposed based on U-series results. Young mantle-derived mafic protolith is thought to be metasomatized and partially melted to form the silicic end-member. However, this model underestimates the compositional variations of the hydrothermally-altered basaltic crust. New data on U-Th disequilibria and O-isotopes in basalts and dacites from Askja volcano reveal a strong correlation between (230Th/232Th) and delta 18O. The 1875 AD dacite has the lowest Th- and O isotope ratios (0.94 and -0.24 per mille, respectively) whereas tephra of evolved basaltic composition, erupted 2 months earlier, has significantly higher values (1.03 and 2.8 per mille, respectively). Highest values are observed in the most recent basalts (erupted in 1920 and 1961) inside the Askja caldera complex and out on the associated fissure swarm (Sveinagja basalt). This correlation also holds for older magma such as an early Holocene dacites, which eruption may have been provoked by rapid glacier thinning. Silicic magmas at Askja volcano thus bear geochemical signatures that are best explained by partial melting of extensively hydrothermally altered crust and that the silicic magma source has remained constant during the Holocene at least. Once these silicic magmas are formed they appear to erupt rapidly rather than mixing and mingling with the incoming basalt heat-source that explains lack of icelandites and the bi-modal volcanism at Askja

  5. Historical earthquake investigations in Greece

    Directory of Open Access Journals (Sweden)

    K. Makropoulos

    2004-06-01

    Full Text Available The active tectonics of the area of Greece and its seismic activity have always been present in the country?s history. Many researchers, tempted to work on Greek historical earthquakes, have realized that this is a task not easily fulfilled. The existing catalogues of strong historical earthquakes are useful tools to perform general SHA studies. However, a variety of supporting datasets, non-uniformly distributed in space and time, need to be further investigated. In the present paper, a review of historical earthquake studies in Greece is attempted. The seismic history of the country is divided into four main periods. In each one of them, characteristic examples, studies and approaches are presented.

  6. Greece welcomes CERN Accelerator School

    CERN Multimedia

    CAS School

    2011-01-01

    The CERN Accelerator School (CAS) and the University of the Aegean jointly organised a course on intermediate-level Accelerator Physics in Chios, Greece, from 19 to 30 September, 2011.   CAS Students pose for a group photo in Chios, Greece. This course followed the established format of the intermediate school, with lectures in the mornings and specialised courses in the afternoons. The latter provided “hands-on” education and experience in three topics: “RF Measurement Techniques”, “Beam Instrumentation and Diagnostics” and “Optics Design and Correction”.  Participants selected one of the three courses and followed the chosen topic throughout the school. Guided studies and tutorials on core subjects, seminars and a poster session completed the programme. An excursion included a visit to the Nea Moni monastery, a guided tour of two medieval villages, Pyrgi and Mesta, and finished with a typical Greek me...

  7. Greece: Too Strategic To Fail

    Science.gov (United States)

    2016-02-16

    institutions? According to American sociologist Fred Block, in a capitalist society, business--hoping to maximize profits--acts as a source of inertia for...Dream of the European Union.” 36 Note: The rationale for bringing Greece into the EEC is noteworthy. As the self -appointed “protector of democracy...have historically defined … the ‘Orient’ or ‘East’ … whether as a geographic entity, a 96

  8. Penetration of Photovoltaics in Greece

    OpenAIRE

    Eugenia Giannini; Antonia Moropoulou; Zacharias Maroulis; Glykeria Siouti

    2015-01-01

    Recently, an interesting experiment was completed in Greece concerning photovoltaic penetration into the electricity production sector. Based on the relevant laws and in accordance to the related European directives, an explosive penetration process was completed in less than three years, resulting in a 7% share of photovoltaics in electricity production instead of the previous negligible share. The legislation was based on licensing simplification and generous feed-in-tariffs. This approach ...

  9. Health economic evaluation in Greece.

    Science.gov (United States)

    Rovithis, Dimitrios

    2006-01-01

    There is a growing volume of literature on health economic evaluation, with this form of analysis becoming increasingly influential at the decision-making level worldwide. The purpose of this study was to review the current state of health economic evaluation in Greece, with a view to uncovering reasons why its use in this country is limited. A search of the NHS Economic Evaluation Database was undertaken. The search included cost, cost-of-illness, cost-minimization, cost-effectiveness, cost-consequences, cost-utility, and cost-benefit analyses and was narrowed only to Greek authors undertaking solo or joint health economic evaluation in Greece. The search revealed that, in Greece, very little health economic evaluation has been undertaken. The main reason for the lack of interest is that the current chaotic healthcare system structure and financing does not provide the appropriate incentives to stimulate a powerful interest in this type of research. This condition is a result of the lack of a long-term national health policy and the hesitation of the present and past Greek governments to date to proceed to large-scale reforms because of political considerations. The Greek governments have also been content with the good health indicators being achieved. Even if it is accepted that good health prevails in Greece, slower economic growth rates, an ageing population, and the continuous immigration will place increasing pressure on healthcare resources and will necessitate a more rational use of these resources. Health economic evaluation, by weighing benefits against costs, therefore, has an important role to play.

  10. Radiographic visualization of magma dynamics in an erupting volcano.

    Science.gov (United States)

    Tanaka, Hiroyuki K M; Kusagaya, Taro; Shinohara, Hiroshi

    2014-03-10

    Radiographic imaging of magma dynamics in a volcanic conduit provides detailed information about ascent and descent of magma, the magma flow rate, the conduit diameter and inflation and deflation of magma due to volatile expansion and release. Here we report the first radiographic observation of the ascent and descent of magma along a conduit utilizing atmospheric (cosmic ray) muons (muography) with dynamic radiographic imaging. Time sequential radiographic images show that the top of the magma column ascends right beneath the crater floor through which the eruption column was observed. In addition to the visualization of this magma inflation, we report a sequence of images that show magma descending. We further propose that the monitoring of temporal variations in the gas volume fraction of magma as well as its position in a conduit can be used to support existing eruption prediction procedures.

  11. Rapid Crystallization of the Bishop Magma

    Science.gov (United States)

    Gualda, G. A.; Anderson, A. T.; Sutton, S. R.

    2007-12-01

    Substantial effort has been made to understand the longevity of rhyolitic magmas, and particular attention has been paid to the systems in the Long Valley area (California). Recent geochronological data suggest discrete magma bodies that existed for hundreds of thousands of years. Zircon crystallization ages for the Bishop Tuff span 100-200 ka, and were interpreted to reflect slow crystallization of a liquid-rich magma. Here we use the diffusional relaxation of Ti zoning in quartz to investigate the longevity of the Bishop magma. We have used such an approach to show the short timescales of crystallization of Ti-rich rims on quartz from early- erupted Bishop Tuff. We have now recognized Ti-rich cores in quartz that can be used to derive the timescales of their crystallization. We studied four samples of the early-erupted Bishop. Hand-picked crystals were mounted on glass slides and polished. Cathodoluminescence (CL) images were obtained using the electron microprobe at the University of Chicago. Ti zoning was documented using the GeoSoilEnviroCARS x-ray microprobe at the Advanced Photon Source (Argonne National Lab). Quartz crystals in all 4 samples include up to 3 Ti-bearing zones: a central core (50-100 μm in diameter, ca. 50 ppm Ti), a volumetrically predominant interior (~40 ppm Ti), and in some crystals a 50-100 μm thick rim (50 ppm Ti). Maximum estimates of core residence times were calculated using a 1D diffusion model, as the time needed to smooth an infinitely steep profile to fit the observed profile. Surprisingly, even for the largest crystals studied - ca. 2 mm in diameter - core residence times are less than 1 ka. Calculated growth rates imply that even cm-sized crystals crystallized in less than 10 ka. Crystal size distribution data show that crystals larger than 3 mm are exceedingly rare, such that the important inference is that the bulk of the crystallization of the early-erupted Bishop magma occurred in only a few thousand years. This timescale

  12. Magma wagging and whirling in volcanic conduits

    Science.gov (United States)

    Liao, Yang; Bercovici, David; Jellinek, Mark

    2018-02-01

    Seismic tremor characterized by 0.5-7 Hz ground oscillations commonly occur before and during eruptions at silicic volcanoes with widely ranging vent geometries and edifice structures. The ubiquitous characteristics of this tremor imply that its causes are potentially common to silicic volcanoes. Here we revisit and extend to three dimensions the magma-wagging model for tremor (Jellinek and Bercovici, 2011; Bercovici et al., 2013), wherein a stiff magma column rising in a vertical conduit oscillates against a surrounding foamy annulus of bubbly magma, giving rise to tremor. While prior studies were restricted to two-dimensional lateral oscillations, here we explore three-dimensional motion and additional modes of oscillations. In the absence of viscous damping, the magma column undergoes 'whirling' motion: the center of each horizontal section of the column traces an elliptical trajectory. In the presence of viscous effect we identify new 'coiling' and 'uncoiling' column bending shapes with relatively higher and comparable rates of dissipation to the original two-dimensional magma wagging model. We also calculate the seismic P-wave response of the crustal material around the volcanic conduit to the new whirling motions and propose seismic diagnostics for different wagging patterns using the time-lag between seismic stations. We test our model by analyzing pre-eruptive seismic data from the 2009 eruption of Redoubt Volcano. In addition to suggesting that the occurrence of elliptical whirling motion more than 1 week before the eruption, our analysis of seismic time-lags also implies that the 2009 eruption was accompanied by qualitative changes in the magma wagging behavior including fluctuations in eccentricity and a reversal in the direction of elliptical whirling motion when the eruption was immediately impending.

  13. The History of Adult Education in Greece.

    Science.gov (United States)

    Boucouvalas, Marcie

    Adult education in Greece dates back to the time of Homer. Poetry and Panhellenic festivals were the earliest forms of adult education in Greece. By classical times, however, an entire learning society of human and material resources had been developed. Greek society experienced periods of high levels of culture and learning only to be conquered…

  14. Education Policy in Greece: A Preliminary Assessment

    Science.gov (United States)

    OECD Publishing, 2017

    2017-01-01

    The future of Greece's well-being will depend on improving educational performance to raise employment and social outcomes. The challenges are significant, as public education expenditure in Greece has declined in recent years and learning outcomes are weak. To help the Greek government address these challenges, this report proposes a set of…

  15. Indoor radon measurements in Athens, Greece

    International Nuclear Information System (INIS)

    Proukakis, C.; Molfetas, M.; Ntalles, K.; Georgiou, E.; Serefoglou, A.

    1987-01-01

    A pilot study was carried out in order to measure air concentrations of radon 222 and 220 isotopes in Athenian houses, as a first step of a national survey in Greece. In this paper the authors deal with radon concentration in air and water and will rely on measurements conducted in Greece. (author)

  16. Artificial magma and applications of the blasting technique

    Energy Technology Data Exchange (ETDEWEB)

    Ichioka, K [Chugoku Kaki KK, Japan

    1974-01-01

    Artifical magma is discussed. Solid magma is a high temperature source and fluid magma is also a heat carrier. Iron ores are examples of solid magma, silica-borate is an example of a hydrophobic heat carrier magma assuming a liquid phase at 600/sup 0/C, and S, Ag, Pb, etc. are also examples of heat carrier magma. In addition to these examples, basic salts such as NaNO/sub 3/, KNO/sub 3/, NaCl, CaCl, KCl, BaCl, and Na/sub 4/B/sub 4/O/sub 7/ can be used as artifical magma. These are artifical magmas or heat mediums capable of capturing geothermal heat when circulated inside volcanoes. The blasting technique's applications in geothermal wells are also discussed. The technique can be used to expand a well's diameter, repair the well bottom, regenerate old wells, clean wells, or cut steel pipe. Two figures and one table are provided.

  17. The endemic flora of Greece

    DEFF Research Database (Denmark)

    Tan, Kit

    2007-01-01

    The Balkan Peninsula has a rich endemic flora estimated as between 2600 and 2700 taxa; c. 750 are restricted to Greece. Conservationists consider the endemic flora of a country needs protection for all time; there is a tendency to paint an alarming picture. However, unless one knows something or ...... have been mapped and it is already possible to recognize the hot-spots of biodiversity as these are linked to the centres of endemism. Determining the centres of diversity is an important and significant contribution to further conservation measures at the global level....

  18. Loki Patera: A Magma Sea Story

    Science.gov (United States)

    Veeder, G. J.; Matson, D. L.; Rathbun, A. G.

    2005-01-01

    We consider Loki Patera on Io as the surface expression of a large uniform body of magma. Our model of the Loki magma sea is some 200 km across; larger than a lake but smaller than an ocean. The depth of the magma sea is unknown, but assumed to be deep enough that bottom effects can be ignored. Edge effects at the shore line can be ignored to first order for most of the interior area. In particular, we take the dark material within Loki Patera as a thin solidified lava crust whose hydrostatic shape follows Io's isostatic surface (approx. 1815 km radius of curvature). The dark surface of Loki appears to be very smooth on both regional and local (subresolution) scales. The thermal contrast between the low and high albedo areas within Loki is consistent with the observed global correlation. The composition of the model magma sea is basaltic and saturated with dissolved SO2 at depth. Its average, almost isothermal, temperature is at the liquidus for basalt. Additional information is included in the original extended abstract.

  19. Probing magma reservoirs to improve volcano forecasts

    Science.gov (United States)

    Lowenstern, Jacob B.; Sisson, Thomas W.; Hurwitz, Shaul

    2017-01-01

    When it comes to forecasting eruptions, volcano observatories rely mostly on real-time signals from earthquakes, ground deformation, and gas discharge, combined with probabilistic assessments based on past behavior [Sparks and Cashman, 2017]. There is comparatively less reliance on geophysical and petrological understanding of subsurface magma reservoirs.

  20. Iron Redox Systematics of Martian Magmas

    Science.gov (United States)

    Righter, K.; Danielson, L.; Martin, A.; Pando, K.; Sutton, S.; Newville, M.

    2011-01-01

    Martian magmas are known to be FeO-rich and the dominant FeO-bearing mineral at many sites visited by the Mars Exploration rovers (MER) is magnetite [1]. Morris et al. [1] propose that the magnetite appears to be igneous in origin, rather than of secondary origin. However, magnetite is not typically found in experimental studies of martian magmatic rocks [2,3]. Magnetite stability in terrestrial magmas is well understood, as are the stability of FeO and Fe2O3 in terrestrial magmas [4,5]. In order to better understand the variation of FeO and Fe2O3, and the stability of magnetite (and other FeO-bearing phases) in martian magmas we have undertaken an experimental study with two emphases. First we document the stability of magnetite with temperature and fO2 in a shergottite bulk composition. Second, we determine the FeO and Fe2O3 contents of the same shergottite bulk composition at 1 bar and variable fO2 at 1250 C, and at variable pressure. These two goals will help define not only magnetite stability, but pyroxene-melt equilibria that are also dependent upon fO2.

  1. Unusual Iron Redox Systematics of Martian Magmas

    Science.gov (United States)

    Danielson, L.; Righter, K.; Pando, K.; Morris, R. V.; Graff, T.; Agresti, D.; Martin, A.; Sutton, S.; Newville, M.; Lanzirotti, A.

    2012-01-01

    Martian magmas are known to be FeO-rich and the dominant FeO-bearing mineral at many sites visited by the Mars Exploration rovers (MER) is magnetite. Morris et al. proposed that the magnetite appears to be igneous in origin, rather than of secondary origin. However, magnetite is not typically found in experimental studies of martian magmatic rocks. Magnetite stability in terrestrial magmas is well understood, as are the stabilities of FeO and Fe2O3 in terrestrial magmas. In order to better understand the variation of FeO and Fe2O3, and the stability of magnetite (and other FeO-bearing phases) in martian magmas, we have undertaken an experimental study with two emphases. First, we determine the FeO and Fe2O3 contents of super- and sub-liquidus glasses from a shergottite bulk composition at 1 bar to 4 GPa, and variable fO2. Second, we document the stability of magnetite with temperature and fO2 in a shergottite bulk composition.

  2. Magma-poor vs. magma-rich continental rifting and breakup in the Labrador Sea

    Science.gov (United States)

    Gouiza, M.; Paton, D.

    2017-12-01

    Magma-poor and magma-rich rifted margins show distinct structural and stratigraphic geometries during the rift to breakup period. In magma-poor margins, crustal stretching is accommodated mainly by brittle faulting and the formation of wide rift basins shaped by numerous graben and half-graben structures. Continental breakup and oceanic crust accretion are often preceded by a localised phase of (hyper-) extension where the upper mantle is embrittled, serpentinized, and exhumed to the surface. In magma-rich margins, the rift basin is narrow and extension is accompanied by a large magmatic supply. Continental breakup and oceanic crust accretion is preceded by the emplacement of a thick volcanic crust juxtaposing and underplating a moderately thinned continental crust. Both magma-poor and magma-rich rifting occur in response to lithospheric extension but the driving forces and processes are believed to be different. In the former extension is assumed to be driven by plate boundary forces, while in the latter extension is supposed to be controlled by sublithospheric mantle dynamics. However, this view fails in explaining observations from many Atlantic conjugate margins where magma-poor and magma-rich segments alternate in a relatively abrupt fashion. This is the case of the Labrador margin where the northern segment shows major magmatic supply during most of the syn-rift phase which culminate in the emplacement of a thick volcanic crust in the transitional domain along with high density bodies underplating the thinned continental crust; while the southern segment is characterized mainly by brittle extension, mantle seprentinization and exhumation prior to continental breakup. In this work, we use seismic and potential field data to describe the crustal and structural architectures of the Labrador margin, and investigate the tectonic and mechanical processes of rifting that may have controlled the magmatic supply in the different segments of the margin.

  3. The mechanics of shallow magma reservoir outgassing

    Science.gov (United States)

    Parmigiani, A.; Degruyter, W.; Leclaire, S.; Huber, C.; Bachmann, O.

    2017-08-01

    Magma degassing fundamentally controls the Earth's volatile cycles. The large amount of gas expelled into the atmosphere during volcanic eruptions (i.e., volcanic outgassing) is the most obvious display of magmatic volatile release. However, owing to the large intrusive:extrusive ratio, and considering the paucity of volatiles left in intrusive rocks after final solidification, volcanic outgassing likely constitutes only a small fraction of the overall mass of magmatic volatiles released to the Earth's surface. Therefore, as most magmas stall on their way to the surface, outgassing of uneruptible, crystal-rich magma storage regions will play a dominant role in closing the balance of volatile element cycling between the mantle and the surface. We use a numerical approach to study the migration of a magmatic volatile phase (MVP) in crystal-rich magma bodies ("mush zones") at the pore scale. Our results suggest that buoyancy-driven outgassing is efficient over crystal volume fractions between 0.4 and 0.7 (for mm-sized crystals). We parameterize our pore-scale results for MVP migration in a thermomechanical magma reservoir model to study outgassing under dynamical conditions where cooling controls the evolution of the proportion of crystal, gas, and melt phases and to investigate the role of the reservoir size and the temperature-dependent viscoelastic response of the crust on outgassing efficiency. We find that buoyancy-driven outgassing allows for a maximum of 40-50% volatiles to leave the reservoir over the 0.4-0.7 crystal volume fractions, implying that a significant amount of outgassing must occur at high crystal content (>0.7) through veining and/or capillary fracturing.

  4. Io: Loki Patera as a Magma Sea

    Science.gov (United States)

    Matson, Dennis L.; Davies, Ashley Gerard; Veeder, Glenn J.; Rathbun, Julie A.; Johnson, Torrence V.; Castillo, Julie C.

    2006-01-01

    We develop a physical model for Loki Patera as a magma sea. We calculate the total volume of magma moving through the Loki Patera volcanic system every resurfacing cycle (approx.540 days) and the resulting variation in thermal emission. The rate of magma solidification at times reaches 3 x 10(exp 6) kg per second, with a total solidified volume averaging 100 cu km per year. A simulation of gas physical chemistry evolution yields the crust porosity profile and the timescale when it will become dense enough to founder in a manner consistent with observations. The Loki Patera surface temperature distribution shows that different areas are at different life cycle stages. On a regional scale, however, there can be coordinated activity, indicated by the wave of thermal change which progresses from Loki Patera's SW quadrant toward the NE at a rate of approx.1 km per day. Using the observed surface temperature distribution, we test several mechanisms for resurfacing Loki Patera, finding that resurfacing with lava flows is not realistic. Only the crustal foundering process is consistent with observations. These tests also discovered that sinking crust has a 'heat deficit' which promotes the solidification of additional magma onto the sinking plate ("bulking up"). In the limiting case, the mass of sinking material can increase to a mass of approx.3 times that of the foundering plate. With all this solid matter sinking, there is a compensating upward motion in the liquid magma. This can be in excess of 2 m per year. In this manner, solid-liquid convection is occurring in the sea.

  5. Foreign Guests in Ancient Greece

    Directory of Open Access Journals (Sweden)

    Zora Žbontar

    2013-12-01

    Full Text Available Xenía was a special relationship between a foreign guest and his host in Ancient Greece. The ritual of hosting a foreigner included an exchange of objects, feasting, and the establishment of friendship between people from different social backgrounds. This relationship implied trust, loyalty, friendship, and mutual aid between the people involved. Goods and services were also exchanged without any form of payment. There were no formal laws governing xenía – it was based entirely on a moral appeal. Mutual appreciation between the host and the guest was established during the ritual, but the host did retain a certain level of superiority over the guest. Xenía was one of the most important institutions in Ancient Greece. It had a lot of features and obligations similar to kinship and marriage. In literary sources the word xénos varies in meaning from “enemy stranger”, “friendly stranger”, “foreigner”, “guest”, “host” to “ritual friend”, and it is often hard to tell which usage is appropriate in a given passage. The paper describes the emphasis on hospitality towards foreigners. It presents an example of a depiction indicating xenía is presented, as well as several objects which were traded during the ritual. The paper also addresses the importance of hospitality in Greek drama in general, especially with examples of violations of the hospitality code.

  6. Radon Survey in Kalamata (Greece)

    International Nuclear Information System (INIS)

    Geranios, A.; Kakoulidou, M.; Mavroidi, Ph.; Moschou, M.; Fisher, S.; Burian, I.; Holecek, J.

    2001-01-01

    A national radon survey is still lacking for Greece. Some groups have carried out several more or less local or extended radon surveys and valuable experience has been gained. After the first preliminary survey carried out by our group, where 500 Kodak LR-115 etched track detectors were placed in Greek schools and dwellings for one year, indoor radon measurements were continued by placing the same number of detectors in a restricted area, covering the city of Kalamata (a medium size city with 60,000 inhabitants), situated in the south of Peloponnese. Although Kalamata was not of special radon interest, the local authorities insisted on knowing for their citizens' sake the level of this natural radiation. At first, the intention was to use a different method of organisation and distribution of the etched-track detectors from the previous one, attempting mainly to acquire more reliable results and to collect as many detectors as possible. Secondly, it was of great importance to test the statistics of the indoor radon concentrations for a rather small area, and thirdly, to estimate independently the annual absorbed dose by children, taking into account radon concentrations measured both in their home and at school. The set of detectors' readings (about 370), revealed, in general, lower values for Kalamata, compared to the ones found in the preliminary radon survey in Greece and almost all concentrations were found to be below the NRPB action level (200 Bq.m -3 ) (author)

  7. Deep magma transport at Kilauea volcano, Hawaii

    Science.gov (United States)

    Wright, T.L.; Klein, F.W.

    2006-01-01

    The shallow part of Kilauea's magma system is conceptually well-understood. Long-period and short-period (brittle-failure) earthquake swarms outline a near-vertical magma transport path beneath Kilauea's summit to 20 km depth. A gravity high centered above the magma transport path demonstrates that Kilauea's shallow magma system, established early in the volcano's history, has remained fixed in place. Low seismicity at 4-7 km outlines a storage region from which magma is supplied for eruptions and intrusions. Brittle-failure earthquake swarms shallower than 5 km beneath the rift zones accompany dike emplacement. Sparse earthquakes extend to a decollement at 10-12 km along which the south flank of Kilauea is sliding seaward. This zone below 5 km can sustain aseismic magma transport, consistent with recent tomographic studies. Long-period earthquake clusters deeper than 40 km occur parallel to and offshore of Kilauea's south coast, defining the deepest seismic response to magma transport from the Hawaiian hot spot. A path connecting the shallow and deep long-period earthquakes is defined by mainshock-aftershock locations of brittle-failure earthquakes unique to Kilauea whose hypocenters are deeper than 25 km with magnitudes from 4.4 to 5.2. Separation of deep and shallow long-period clusters occurs as the shallow plumbing moves with the volcanic edifice, while the deep plumbing is centered over the hotspot. Recent GPS data agrees with the volcano-propagation vector from Kauai to Maui, suggesting that Pacific plate motion, azimuth 293.5?? and rate of 7.4 cm/yr, has been constant over Kilauea's lifetime. However, volcano propagation on the island of Hawaii, azimuth 325??, rate 13 cm/yr, requires southwesterly migration of the locus of melting within the broad hotspot. Deep, long-period earthquakes lie west of the extrapolated position of Kilauea backward in time along a plate-motion vector, requiring southwesterly migration of Kilauea's magma source. Assumed ages of 0

  8. Magma Dynamics in Dome-Building Volcanoes

    Science.gov (United States)

    Kendrick, J. E.; Lavallée, Y.; Hornby, A. J.; Schaefer, L. N.; Oommen, T.; Di Toro, G.; Hirose, T.

    2014-12-01

    The frequent and, as yet, unpredictable transition from effusive to explosive volcanic behaviour is common to active composite volcanoes, yet our understanding of the processes which control this evolution is poor. The rheology of magma, dictated by its composition, porosity and crystal content, is integral to eruption behaviour and during ascent magma behaves in an increasingly rock-like manner. This behaviour, on short timescales in the upper conduit, provides exceptionally dynamic conditions that favour strain localisation and failure. Seismicity released by this process can be mimicked by damage accumulation that releases acoustic signals on the laboratory scale, showing that the failure of magma is intrinsically strain-rate dependent. This character aids the development of shear zones in the conduit, which commonly fracture seismogenically, producing fault surfaces that control the last hundreds of meters of ascent by frictional slip. High-velocity rotary shear (HVR) experiments demonstrate that at ambient temperatures, gouge behaves according to Byerlee's rule at low slip velocities. At rock-rock interfaces, mechanical work induces comminution of asperities and heating which, if sufficient, may induce melting and formation of pseudotachylyte. The viscosity of the melt, so generated, controls the subsequent lubrication or resistance to slip along the fault plane thanks to non-Newtonian suspension rheology. The bulk composition, mineralogy and glass content of the magma all influence frictional behaviour, which supersedes buoyancy as the controlling factor in magma ascent. In the conduit of dome-building volcanoes, the fracture and slip processes are further complicated: slip-rate along the conduit margin fluctuates. The shear-thinning frictional melt yields a tendency for extremely unstable slip thanks to its pivotal position with regard to the glass transition. This thermo-kinetic transition bestows the viscoelastic melt with the ability to either flow or

  9. The crustal magma storage system of Volcán Quizapu, Chile, and the effects of magma mixing on magma diversity

    Science.gov (United States)

    Bergantz, George W.; Cooper, Kari M.; Hildreth, Edward; Ruprecht, Phillipp

    2012-01-01

    Crystal zoning as well as temperature and pressure estimates from phenocryst phase equilibria are used to constrain the architecture of the intermediate-sized magmatic system (some tens of km3) of Volcán Quizapu, Chile, and to document the textural and compositional effects of magma mixing. In contrast to most arc magma systems, where multiple episodes of open-system behavior obscure the evidence of major magma chamber events (e.g. melt extraction, magma mixing), the Quizapu magma system shows limited petrographic complexity in two large historical eruptions (1846–1847 and 1932) that have contrasting eruptive styles. Quizapu magmas and peripheral mafic magmas exhibit a simple binary mixing relationship. At the mafic end, basaltic andesite to andesite recharge magmas complement the record from peripheral cones and show the same limited range of compositions. The silicic end-member composition is almost identical in both eruptions of Quizapu. The effusive 1846–1847 eruption records significant mixing between the mafic and silicic end-members, resulting in hybridized andesites and mingled dacites. These two compositionally simple eruptions at Volcán Quizapu present a rare opportunity to isolate particular aspects of magma evolution—formation of homogeneous dacite magma and late-stage magma mixing—from other magma chamber processes. Crystal zoning, trace element compositions, and crystal-size distributions provide evidence for spatial separation of the mafic and silicic magmas. Dacite-derived plagioclase phenocrysts (i.e. An25–40) show a narrow range in composition and limited zonation, suggesting growth from a compositionally restricted melt. Dacite-derived amphibole phenocrysts show similar restricted compositions and furthermore constrain, together with more mafic amphibole phenocrysts, the architecture of the magmatic system at Volcán Quizapu to be compositionally and thermally zoned, in which an andesitic mush is overlain by a homogeneous dacitic

  10. Greece, Milos Island Geothermal Project

    International Nuclear Information System (INIS)

    Delliou, E.E.

    1990-01-01

    On Milos island (Aegean Sea) a high enthalpy, water dominated geothermal field of high salinity exists. At 1985, a 2MW geothermoelectric pilot plant was installed on the island. This plant has been provided by Mitsubishi Heavy Industries of Japan under a contract with Public Power Corporation of Greece. Due to high salinity of the geothermal fluid, unforeseen problems (scaling mainly) arisen in both steam and brine cycles. As a consequence, the operation (trial mainly) of the power plant have been interrupted several times for long periods, in order to identify the arisen, each time, problems and find the most appropriate technical solution. The above fact, as well as, some unfortunate coincidences described in this paper, led Milos people to react against geothermal development in their island. The sequence of the events, technical and non-technical, their approach and the relevant conclusions are reported in this presentation

  11. Penetration of Photovoltaics in Greece

    Directory of Open Access Journals (Sweden)

    Eugenia Giannini

    2015-06-01

    Full Text Available Recently, an interesting experiment was completed in Greece concerning photovoltaic penetration into the electricity production sector. Based on the relevant laws and in accordance to the related European directives, an explosive penetration process was completed in less than three years, resulting in a 7% share of photovoltaics in electricity production instead of the previous negligible share. The legislation was based on licensing simplification and generous feed-in-tariffs. This approach transformed photovoltaic technology from a prohibitively expensive to a competitive one. This work aims to summarize the relevant legislation and illustrate its effect on the resulting penetration. A sigmoid-shape penetration was observed which was explained by a pulse-type driving force. The return on investment indicator was proposed as an appropriate driving force, which incorporates feed-in-tariffs and turnkey-cost. Furthermore, the resulting surcharge on the electricity price due to photovoltaic penetration was also analyzed.

  12. Magma ocean formation due to giant impacts

    Science.gov (United States)

    Tonks, W. B.; Melosh, H. J.

    1993-01-01

    The thermal effects of giant impacts are studied by estimating the melt volume generated by the initial shock wave and corresponding magma ocean depths. Additionally, the effects of the planet's initial temperature on the generated melt volume are examined. The shock pressure required to completely melt the material is determined using the Hugoniot curve plotted in pressure-entropy space. Once the melting pressure is known, an impact melting model is used to estimate the radial distance melting occurred from the impact site. The melt region's geometry then determines the associated melt volume. The model is also used to estimate the partial melt volume. Magma ocean depths resulting from both excavated and retained melt are calculated, and the melt fraction not excavated during the formation of the crater is estimated. The fraction of a planet melted by the initial shock wave is also estimated using the model.

  13. Illuminating magma shearing processes via synchrotron imaging

    Science.gov (United States)

    Lavallée, Yan; Cai, Biao; Coats, Rebecca; Kendrick, Jackie E.; von Aulock, Felix W.; Wallace, Paul A.; Le Gall, Nolwenn; Godinho, Jose; Dobson, Katherine; Atwood, Robert; Holness, Marian; Lee, Peter D.

    2017-04-01

    Our understanding of geomaterial behaviour and processes has long fallen short due to inaccessibility into material as "something" happens. In volcanology, research strategies have increasingly sought to illuminate the subsurface of materials at all scales, from the use of muon tomography to image the inside of volcanoes to the use of seismic tomography to image magmatic bodies in the crust, and most recently, we have added synchrotron-based x-ray tomography to image the inside of material as we test it under controlled conditions. Here, we will explore some of the novel findings made on the evolution of magma during shearing. These will include observations and discussions of magma flow and failure as well as petrological reaction kinetics.

  14. Monitoraggio remoto delle deformazioni nell’isola di Santorini: una procedura integrata di analisi dati GPS presso la Sezione INGV di Bologna

    Directory of Open Access Journals (Sweden)

    Arianna Pesci

    2012-06-01

    Full Text Available Il GPS (Global Positioning System è un noto sistema di posizionamento globale in grado di fornire le coordinate spaziali di unoperatore, se munito di antenna e ricevitore satellitari, in qualunque punto della terra esso si trovi, in qualunque condizionemeteo ed in qualsiasi ora del giorno. Oggi al GPS, che è di proprietà del Dipartimento della Difesa degli Stati Uniti d'America(US DoD, si affiancano il GLONASS (sistema analogo russo e altri sistemi di posizionamento globale basati su tecniche interferometriche spaziali a partire da segnali a microonde, ad esempio i nascenti Galileo (europeo e BeiDou (cinese. Per questo motivo si parla diffusamente di sistemi GNSS cioè Global Navigation Satellite System.   Remote monitoring of deformations in the island of Santorini: an integrated procedure for GPS data analysis at the INGV in Bologna The GPS (Global Positioning System is a well-known global positioning  system  capable  of  providing  the  spatial  coordi-nates of an operator, if equipped with an antenna and a re-ceiver satellite, at any point on the earth , and in any weather conditions and at any time of the day. Today, the GPS, which is owned by the Department of Defense of the United States of America (U.S. DoD, is aided by the GLONASS (the Russian analogue system and other global positioning systems based on interferometry from space microwave signals, for example, the  nascent  Galileo  (European  and  Beidou  (China.  For  this reason we talk at today about GNSS Global Navigation Satel-lite System.

  15. Setting an ecological baseline prior to the bottom-up establishment of a marine protected area in Santorini island, Aegean Sea

    Directory of Open Access Journals (Sweden)

    M. SALOMIDI

    2016-08-01

    Full Text Available Since 2010, a bottom-up initiative has been launched in Santorini Island (Aegean Sea, Eastern Mediterranean for the establishment of the first fully-protected marine protected area in the Cyclades, aiming at improving fisheries and enhancing responsible recreational uses at sea. Following discussions with local small-scale fishers and divers, two sites along the southern and southeastern coasts of the island were suggested as suitable to this end. In 2012, a baseline study was conducted at these areas to assess their state and provide an ecological snapshot that would enable sound designation and monitoring. Several ad hoc indices and metrics were applied, taking into account structural and functional features of the upper infralittoral algae and Posidonia oceanica beds. An integrated assessment of the infralittoral fish assemblages and their associated benthic communities was also performed. Our most important findings were: (i the low total fish biomass and the absence of adult top predators, indicating overfishing; (ii the overgrazing effects of the overabundant alien herbivore spinefoot fishes (Siganus spp., as reflected by the abnormal structure of the algal communities; (iii the scarcity of signs of pollution or other direct anthropogenic pressures, as indicated by the good environmental status of the P. oceanica meadows and the upper infralittoral vegetation; and (iv the presence of a rich diversity of species and habitats, especially along the Akrotiri Peninsula and the wider volcanic Caldera. These findings provide useful insights on strengths and weaknesses of the study area and are discussed together with their implications for protection and management.

  16. Pressure waves in a supersaturated bubbly magma

    Science.gov (United States)

    Kurzon, I.; Lyakhovsky, V.; Navon, O.; Chouet, B.

    2011-01-01

    We study the interaction of acoustic pressure waves with an expanding bubbly magma. The expansion of magma is the result of bubble growth during or following magma decompression and leads to two competing processes that affect pressure waves. On the one hand, growth in vesicularity leads to increased damping and decreased wave amplitudes, and on the other hand, a decrease in the effective bulk modulus of the bubbly mixture reduces wave velocity, which in turn, reduces damping and may lead to wave amplification. The additional acoustic energy originates from the chemical energy released during bubble growth. We examine this phenomenon analytically to identify conditions under which amplification of pressure waves is possible. These conditions are further examined numerically to shed light on the frequency and phase dependencies in relation to the interaction of waves and growing bubbles. Amplification is possible at low frequencies and when the growth rate of bubbles reaches an optimum value for which the wave velocity decreases sufficiently to overcome the increased damping of the vesicular material. We examine two amplification phase-dependent effects: (1) a tensile-phase effect in which the inserted wave adds to the process of bubble growth, utilizing the energy associated with the gas overpressure in the bubble and therefore converting a large proportion of this energy into additional acoustic energy, and (2) a compressive-phase effect in which the pressure wave works against the growing bubbles and a large amount of its acoustic energy is dissipated during the first cycle, but later enough energy is gained to amplify the second cycle. These two effects provide additional new possible mechanisms for the amplification phase seen in Long-Period (LP) and Very-Long-Period (VLP) seismic signals originating in magma-filled cracks.

  17. Yamato 980459: Crystallization of Martian Magnesian Magma

    Science.gov (United States)

    Koizumi, E.; Mikouchi, T.; McKay, G.; Monkawa, A.; Chokai, J.; Miyamoto, M.

    2004-01-01

    Recently, several basaltic shergottites have been found that include magnesian olivines as a major minerals. These have been called olivinephyric shergottites. Yamato 980459, which is a new martian meteorite recovered from the Antarctica by the Japanese Antarctic expedition, is one of them. This meteorite is different from other olivine-phyric shergottites in several key features and will give us important clues to understand crystallization of martian meteorites and the evolution of Martian magma.

  18. Greece and NATO: Problems and Prospects.

    Science.gov (United States)

    1980-06-06

    adept diplomatic maneuvers. Andreas Papandreou, the leader of PASOK (the main opposition party in Greece), maintains that Karamanlis is still pro...at the expense of the center party, was PASOK (Panhellenic Socialist Movement) led by Andreas Papandreou. PASOK polled 25% of the vote, almost double...its 1974 vote. This gave PASOK 93 seats in the Greek parliament. PASOK’s platform advocates the transformation of Greece into a socialist state. It is

  19. The Ancient Greece's roots of Olimpism

    Directory of Open Access Journals (Sweden)

    Bubka Sergej Nazarovich

    2011-10-01

    Full Text Available The paper focused on the phenomena of sport in Ancient Greece along with history, traditions, religion, education, culture and art. Economic and political conditions are analysed which promote or hamper development of Olympic Games in Ancient Greece. Exceptional stability of Ancient Olympic games during more than eleven centuries are noted as well as their influence on the life of Greek polices of those days. Hellenistic period needs of individual consideration.

  20. Greece is the future of Europe

    DEFF Research Database (Denmark)

    Douzinas, Costas; Risager, Bjarke Skærlund

    2014-01-01

    Austerity and popular resistance are essential to a political diagnosis for contemporary Europe. Political developments in Greece will show whether the future of Europe is one of neoliberal restructuring or one of a democratic socialist alternative. An interview with Costas Douzinas.......Austerity and popular resistance are essential to a political diagnosis for contemporary Europe. Political developments in Greece will show whether the future of Europe is one of neoliberal restructuring or one of a democratic socialist alternative. An interview with Costas Douzinas....

  1. Adakitic magmas: modern analogues of Archaean granitoids

    Science.gov (United States)

    Martin, Hervé

    1999-03-01

    Both geochemical and experimental petrological research indicate that Archaean continental crust was generated by partial melting of an Archaean tholeiite transformed into a garnet-bearing amphibolite or eclogite. The geodynamic context of tholeiite melting is the subject of controversy. It is assumed to be either (1) subduction (melting of a hot subducting slab), or (2) hot spot (melting of underplated basalts). These hypotheses are considered in the light of modern adakite genesis. Adakites are intermediate to felsic volcanic rocks, andesitic to rhyolitic in composition (basaltic members are lacking). They have trondhjemitic affinities (high-Na 2O contents and K 2O/Na 2O˜0.5) and their Mg no. (0.5), Ni (20-40 ppm) and Cr (30-50 ppm) contents are higher than in typical calc-alkaline magmas. Sr contents are high (>300 ppm, until 2000 ppm) and REE show strongly fractionated patterns with very low heavy REE (HREE) contents (Yb≤1.8 ppm, Y≤18 ppm). Consequently, high Sr/Y and La/Yb ratios are typical and discriminating features of adakitic magmas, indicative of melting of a mafic source where garnet and/or hornblende are residual phases. Adakitic magmas are only found in subduction zone environments, exclusively where the subduction and/or the subducted slab are young (subducted and where the adakitic character of the lavas correlates well with the young age of the subducting oceanic lithosphere. In typical subduction zones, the subducted lithosphere is older than 20 Ma, it is cool and the geothermal gradient along the Benioff plane is low such that the oceanic crust dehydrates before it reaches the solidus temperature of hydrated tholeiite. Consequently, the basaltic slab cannot melt. The released large ion lithophile element (LILE)-rich fluids rise up into the mantle wedge, inducing both its metasomatism and partial melting. Afterwards, the residue is made up of olivine+clinopyroxene+orthopyroxene, such that the partial melts are HREE-rich (low La/Yb and Sr

  2. The new Hamburg Ocean Bottom Tiltmeter: A First Deployment at Columbo Seamount (Aegean Sea, Greece)

    Science.gov (United States)

    Hensch, M.; Hort, M.; Dahm, T.; Winter, S.; Klawonn, M.

    2009-04-01

    Assessing the state of volcanic activity of seamounts is quite more complicated than for onshore volcanoes, due to the difficulty of deploying instruments. At land, various techniques are applied (seismic networks, deformation studies, gas measurements etc.). At sea, mainly seismological observations are used. However, especially onshore deformation studies using INSAR have proven to be valuable in determining recharge of magmatic systems. We therefore developed a free fall, self leveling Ocean Bottom Tiltmeter (OBT) to observe deformation on the seafloor, using a two component high resolution tilt sensor with a resolution of about 1nrad (0.15μ°) and a maximum signal of about 0.045rad (0.5°). It is mounted inside a 17" glass sphere on a levelling stage, which relevels the instrument between ± 5° down to an accuracy of 0.006°. During the measurement this leveling stage is standing on the bottom of the glass sphere. For releveling, the instrument is pulled up by thin nylon strings and then locked to a gimbal system in order to compensate for tilt >5°. This releveling procedure is done once every 48 hours. Data is recorded on an 18bit data logger at 50Hz sampling rate. Additionally to tilt and seismic signals (using a hydrophone), temperature, absolute pressure to measure uplift or subsidence, and orientation (electronic compass) are monitored. 4 OBT systems were deployed between June 2006 and March 2007 at Columbo seamount, a submarine volcano north-east of Santorini island, Aegean Sea, Greece, on a 3 km long profile perpendicular to the first principal stress axis of the regional stressfield. Three of the instruments operated the whole time, one shut down due to a short circuit. First data processing indicates that small regional earthquakes as well as major tectonic earthquakes are properly recorded by the system. We find small, but permanent short-period deformations associated with local earthquakes and also observe long-period deformation processes

  3. The influence of magma viscosity on convection within a magma chamber

    Science.gov (United States)

    Schubert, M.; Driesner, T.; Ulmer, P.

    2012-12-01

    Magmatic-hydrothermal ore deposits are the most important sources of metals like Cu, Mo, W and Sn and a major resource for Au. It is well accepted that they are formed by the release of magmatic fluids from a batholith-sized magma body. Traditionally, it has been assumed that crystallization-induced volatile saturation (called "second boiling") is the main mechanism for fluid release, typically operating over thousands to tens of thousands of years (Candela, 1991). From an analysis of alteration halo geometries caused by magmatic fluids, Cathles and Shannon (2007) suggested much shorter timescales in the order of hundreds of years. Such rapid release of fluids cannot be explained by second boiling as the rate of solidification scales with the slow conduction of heat away from the system. However, rapid fluid release is possible if convection is assumed within the magma chamber. The magma would degas in the upper part of the magma chamber and volatile poor magma would sink down again. Such, the rates of degassing can be much higher than due to cooling only. We developed a convection model using Navier-Stokes equations provided by the computational fluid dynamics platform OpenFOAM that gives the possibility to use externally derived meshes with complex (natural) geometries. We implemented a temperature, pressure, composition and crystal fraction dependent viscosity (Ardia et al., 2008; Giordano et al., 2008; Moore et al., 1998) and a temperature, pressure, composition dependent density (Lange1994). We found that the new viscosity and density models strongly affect convection within the magma chamber. The dependence of viscosity on crystal fraction has a particularly strong effect as the steep viscosity increase at the critical crystal fraction leads to steep decrease of convection velocity. As the magma chamber is cooling from outside to inside a purely conductive layer is developing along the edges of the magma chamber. Convection continues in the inner part of the

  4. Cost-benefit analyses for the development of magma power

    International Nuclear Information System (INIS)

    Haraden, John

    1992-01-01

    Magma power is the potential generation of electricity from shallow magma bodies in the crust of the Earth. Considerable uncertainty still surrounds the development of magma power, but most of that uncertainty may be eliminated by drilling the first deep magma well. The uncertainty presents no serious impediments to the private drilling of the well. For reasons unrelated to the uncertainty, there may be no private drilling and there may be justification for public drilling. In this paper, we present cost-benefit analyses for private and public drilling of the well. Both analyses indicate there is incentive for drilling. (Author)

  5. Outgassing From Open And Closed Magma Foams

    Science.gov (United States)

    von Aulock, Felix W.; Kennedy, Ben M.; Maksimenko, Anton; Wadsworth, Fabian B.; Lavallée, Yan

    2017-06-01

    During magma ascent, bubbles nucleate, grow, coalesce, and form a variably permeable porous network. The volcanic system opens and closes as bubble walls reorganize, seal or fail. In this contribution we cause obsidian to nucleate and grow bubbles to high gas volume fraction at atmospheric pressure by heating samples to 950 ºC for different times and we image the growth through a furnace. Following the experiment, we imaged the internal pore structure of selected samples in 3D and then dissected for analysis of textures and dissolved water content remnant in the glass. We demonstrate that in these high viscosity systems, during foaming and subsequent foam-maturation, bubbles near a free surface resorb via diffusion to produce an impermeable skin of melt around a foam. The skin thickens nonlinearly through time. The water concentrations at the outer and inner skin margins reflect the solubility of water in the melt at the partial pressure of water in atmospheric and water-rich bubble conditions, respectively. In this regime, mass transfer of water out of the system is diffusion limited and the sample shrinks slowly. In a second set of experiments in which we polished off the skin of the foamed samples and placed them back in the furnace, we observe rapid sample contraction and collapse of the connected pore network under surface tension as the system efficiently outgasses. In this regime, mass transfer of water is permeability limited. The mechanisms described here are relevant to the evolution of pore network heterogeneity in permeable magmas. We conclude that diffusion-driven skin formation can efficiently seal connectivity in foams. When rupture of melt film around gas bubbles (i.e. skin removal) occurs, then rapid outgassing and consequent foam collapse modulate gas pressurisation in the vesiculated magma.

  6. Experimental Constraints on a Vesta Magma Ocean

    Science.gov (United States)

    Hoff, C.; Jones, J. H.; Le, L.

    2014-01-01

    A magma ocean model was devised to relate eucrites (basalts) and diogenites (orthopyroxenites), which are found mixed together as clasts in a suite of polymict breccias known as howardites. The intimate association of eucritic and diogenitic clasts in howardites argues strongly that these three classes of achondritic meteorites all originated from the same planetoid. Reflectance spectral evidence (including that from the DAWN mission) has long suggested that Vesta is indeed the Eucrite Parent Body. Specifically, the magma ocean model was generated as follows: (i) the bulk Vesta composition was taken to be 0.3 CV chondrite + 0.7 L chondrite but using only 10% of the Na2O from this mixture; (ii) this composition is allowed to crystallize at 500 bar until approx. 80% of the system is solid olivine + low-Ca pyroxene; (iii) the remaining 20% liquid crystallizes at one bar from 1250C to 1110C, a temperature slightly above the eucrite solidus. All crystallization calculations were performed using MELTS. In this model, diogenites are produced by cocrystallization of olivine and pyroxene in the >1250C temperature regime, with Main Group eucrite liquids being generated in the 1300-1250C temperature interval. Low-Ca pyroxene reappears at 1210C in the one-bar calculations and fractionates the residual liquid to produce evolved eucrite compositions (Stannern Trend). We have attempted to experimentally reproduce the magma ocean. In the MELTS calculation, the change from 500 bar to one bar results in a shift of the olivine:low-Ca pyroxene boundary so that the 1250C liquid is now in the olivine field and, consequently, olivine should be the first-crystallizing phase, followed by low-Ca pyroxene at 1210C, and plagioclase at 1170C. Because at one bar the olivine:low-Ca pyroxene boundary is a peritectic, fractional crystallization of the 1210C liquid proceeds with only pyroxene crystallization until plagioclase appears. Thus, the predictions of the MELTS calculation are clear and

  7. Outgassing from Open and Closed Magma Foams

    Directory of Open Access Journals (Sweden)

    Felix W. von Aulock

    2017-06-01

    Full Text Available During magma ascent, bubbles nucleate, grow, coalesce, and form a variably permeable porous network. The reorganization, failing and sealing of bubble walls may contribute to the opening and closing of the volcanic system. In this contribution we cause obsidian to nucleate and grow bubbles to high gas volume fraction at atmospheric pressure by heating samples to 950°C for different times and we image the growth through a furnace. Following the experiment, we imaged the internal pore structure of selected samples in 3D and then dissected for analysis of textures and dissolved water content remnant in the glass. We demonstrate that in these high viscosity systems, during foaming and subsequent foam-maturation, bubbles near a free surface resorb via diffusion to produce an impermeable skin of melt around a foam. The skin thickens non-linearly through time. The water concentrations at the outer and inner skin margins reflect the solubility of water in the melt at the partial pressure of water in atmospheric and water-rich bubble conditions, respectively. In this regime, mass transfer of water out of the system is diffusion limited and the sample shrinks slowly. In a second set of experiments in which we polished off the skin of the foamed samples and placed them back in the furnace to allow open system outgassing, we observe rapid sample contraction and collapse of the connected pore network under surface tension as the system efficiently outgasses. In this regime, mass transfer of water is permeability limited. We conclude that diffusion-driven skin formation can efficiently seal connectivity in foams. When rupture of melt film around gas bubbles (i.e., skin removal occurs, then rapid outgassing and consequent foam collapse modulate gas pressurization in the vesiculated magma. The mechanisms described here are relevant to the evolution of pore network heterogeneity in permeable magmas.

  8. Experimental Study of Lunar and SNC Magmas

    Science.gov (United States)

    Rutherford, Malcolm J.

    1998-01-01

    The research described in this progress report involved the study of petrological, geochemical and volcanic processes that occur on the Moon and the SNC parent body, generally accepted to be Mars. The link between these studies is that they focus on two terrestrial-type parent bodies somewhat smaller than earth, and the fact that they focus on the role of volatiles in magmatic processes and on processes of magma evolution on these planets. The work on the lunar volcanic glasses has resulted in some exciting new discoveries over the years of this grant. We discovered small metal blebs initially in the Al5 green glass, and determined the significant importance of this metal in fixing the oxidation state of the parent magma (Fogel and Rutherford, 1995). More recently, we discovered a variety of metal blebs in the Al7 orange glass. Some of these Fe-Ni metal blebs were in the glass; others were in olivine phenocrysts. The importance of these metal spheres is that they fix the oxidation state of the parent magma during the eruption, and also indicate changes during the eruption (Weitz et al., 1997) They also yield important information about the composition of the gas phase present, the gas which drove the lunar fire-fountaining. One of the more exciting and controversial findings in our research over the past year has been the possible fractionation of H from D during shock (experimental) of hornblende bearing samples (Minitti et al., 1997). This research is directed at explaining some of the low H2O and high D/H observed in hydrous phases in the SNC meteorites.

  9. Special relativity derived from spacetime magma.

    Science.gov (United States)

    Greensite, Fred

    2014-01-01

    We present a derivation of relativistic spacetime largely untethered from specific physical considerations, in constrast to the many physically-based derivations that have appeared in the last few decades. The argument proceeds from the inherent magma (groupoid) existing on the union of spacetime frame components [Formula: see text] and Euclidean [Formula: see text] which is consistent with an "inversion symmetry" constraint from which the Minkowski norm results. In this context, the latter is also characterized as one member of a class of "inverse norms" which play major roles with respect to various unital [Formula: see text]-algebras more generally.

  10. Special relativity derived from spacetime magma.

    Directory of Open Access Journals (Sweden)

    Fred Greensite

    Full Text Available We present a derivation of relativistic spacetime largely untethered from specific physical considerations, in constrast to the many physically-based derivations that have appeared in the last few decades. The argument proceeds from the inherent magma (groupoid existing on the union of spacetime frame components [Formula: see text] and Euclidean [Formula: see text] which is consistent with an "inversion symmetry" constraint from which the Minkowski norm results. In this context, the latter is also characterized as one member of a class of "inverse norms" which play major roles with respect to various unital [Formula: see text]-algebras more generally.

  11. Dynamics of differentiation in magma reservoirs

    Science.gov (United States)

    Jaupart, Claude; Tait, Stephen

    1995-09-01

    In large magma chambers, gradients of temperature and composition develop due to cooling and to fractional crystallization. Unstable density differences lead to differential motions between melt and crystals, and a major goal is to explain how this might result in chemical differentiation of magma. Arriving at a full description of the physics of crystallizing magma chambers is a challenge because of the large number of processes potentially involved, the many coupled variables, and the different geometrical shapes. Furthermore, perturbations are caused by the reinjection of melt from a deep source, eruption to the Earth's surface, and the assimilation of country rock. Physical models of increasing complexity have been developed with emphasis on three fundamental approaches. One is, given that large gradients in temperature and composition may occur, to specify how to apply thermodynamic constraints so that coexisting liquid and solid compositions may be calculated. The second is to leave the differentiation trend as the solution to be found, i.e., to specify how cooling occurs and to predict the evolution of the composition of the residual liquid and of the solid forming. The third is to simplify the physics so that the effects of coupled heat and mass transfer may be studied with a reduced set of variables. The complex shapes of magma chambers imply that boundary layers develop with density gradients at various angles to gravity, leading to various convective flows and profiles qf liquid stratification. Early studies were mainly concerned with describing fluid flow in the liquid interior of large reservoirs, due to gradients developed at the margins. More recent work has focused on the internal structure and flow field of boundary layers and in particular on the gradients of solid fraction and interstitial melt composition which develop within them. Crystal settling may occur in a surprisingly diverse range of regimes and may lead to intermittent deposition

  12. Lignite As Contributory Factor to Regional Development of Greece

    OpenAIRE

    Ilias Kordas

    2006-01-01

    Lignite (brown coal) is Greece's most important energy mineral raw material. Lignite exploitation has made a highly significant contribution to the development of energy sector of Greece on past 50 years, and will, according to estimations, continue to supply energy for another 40 years. Greece is very rich in Lignite resources. The two main basins - from where Lignite is extracted by opencast mining - are a) in Western Macedonia (northen Greece) where is generated the 70% of the whole electr...

  13. Magma evolution inside the 1631 Vesuvius magma chamber and eruption triggering

    Science.gov (United States)

    Stoppa, Francesco; Principe, Claudia; Schiazza, Mariangela; Liu, Yu; Giosa, Paola; Crocetti, Sergio

    2017-03-01

    Vesuvius is a high-risk volcano and the 1631 Plinian eruption is a reference event for the next episode of explosive unrest. A complete stratigraphic and petrographic description of 1631 pyroclastics is given in this study. During the 1631 eruption a phonolite was firstly erupted followed by a tephritic phonolite and finally a phonolitic tephrite, indicating a layered magma chamber. We suggest that phonolitic basanite is a good candidate to be the primitive parental-melt of the 1631 eruption. Composition of apatite from the 1631 pyroclastics is different from those of CO2-rich melts indicating negligible CO2 content during magma evolution. Cross checking calculations, using PETROGRAPH and PELE software, accounts for multistage evolution up to phonolite starting from a phonolitic basanite melt similar to the Vesuvius medieval lavas. The model implies crystal settling of clinopyroxene and olivine at 6 kbar and 1220°C, clinopyroxene plus leucite at a pressure ranging from 2.5 to 0.5 kbar and temperature ranging from 1140 to 940°C. Inside the phonolitic magma chamber K-feldspar and leucite would coexist at a temperature ranging from from 940 to 840°C and at a pressure ranging from 2.5 to0.5 kbar. Thus crystal fractionation is certainly a necessary and probably a sufficient condition to evolve the melt from phono tephritic to phonolitic in the 1631 magma chamber. We speculate that phonolitic tephrite magma refilling from deeper levels destabilised the chamber and triggered the eruption, as testified by the seismic precursor phenomena before 1631 unrest.

  14. Magma evolution inside the 1631 Vesuvius magma chamber and eruption triggering

    Directory of Open Access Journals (Sweden)

    Stoppa Francesco

    2017-03-01

    Full Text Available Vesuvius is a high-risk volcano and the 1631 Plinian eruption is a reference event for the next episode of explosive unrest. A complete stratigraphic and petrographic description of 1631 pyroclastics is given in this study. During the 1631 eruption a phonolite was firstly erupted followed by a tephritic phonolite and finally a phonolitic tephrite, indicating a layered magma chamber. We suggest that phonolitic basanite is a good candidate to be the primitive parental-melt of the 1631 eruption. Composition of apatite from the 1631 pyroclastics is different from those of CO2-rich melts indicating negligible CO2 content during magma evolution. Cross checking calculations, using PETROGRAPH and PELE software, accounts for multistage evolution up to phonolite starting from a phonolitic basanite melt similar to the Vesuvius medieval lavas. The model implies crystal settling of clinopyroxene and olivine at 6 kbar and 1220°C, clinopyroxene plus leucite at a pressure ranging from 2.5 to 0.5 kbar and temperature ranging from 1140 to 940°C. Inside the phonolitic magma chamber K-feldspar and leucite would coexist at a temperature ranging from from 940 to 840°C and at a pressure ranging from 2.5 to0.5 kbar. Thus crystal fractionation is certainly a necessary and probably a sufficient condition to evolve the melt from phono tephritic to phonolitic in the 1631 magma chamber. We speculate that phonolitic tephrite magma refilling from deeper levels destabilised the chamber and triggered the eruption, as testified by the seismic precursor phenomena before 1631 unrest.

  15. Harmonic analysis of the precipitation in Greece

    Science.gov (United States)

    Nastos, P. T.; Zerefos, C. S.

    2009-04-01

    Greece is a country with a big variety of climates due to its geographical position, to the many mountain ranges and also to the multifarious and long coastline. The mountainous volumes are of such orientation that influences the distribution of the precipitation, having as a result, Western Greece to present great differentiations from Central and Eastern Greece. The application of harmonic analysis to the annual variability of precipitation is the goal of this study, so that the components, which compose the annual variability, be elicited. For this purpose, the mean monthly precipitation data from 30 meteorological stations of National Meteorological Service were used for the time period 1950-2000. The initial target is to reduce the number of variables and to detect structure in the relationships between variables. The most commonly used technique for this purpose is the application of Factor Analysis to a table having as columns the meteorological stations-variables and rows the monthly mean precipitation, so that 2 main factors were calculated, which explain the 98% of total variability of precipitation in Greece. Factor 1, representing the so-called uniform field and interpreting the most of the total variance, refers in fact to the Mediterranean depressions, affecting mainly the West of Greece and also the East Aegean and the Asia Minor coasts. In the process, the Fourier Analysis was applied to the factor scores extracted from the Factor Analysis, so that 2 harmonic components are resulted, which explain above the 98% of the total variability of each main factor, and are due to different synoptic and thermodynamic processes associated with Greece's precipitation construction. Finally, the calculation of the time of occurrence of the maximum precipitation, for each harmonic component of each one of the two main factors, gives the spatial distribution of appearance of the maximum precipitation in the Hellenic region.

  16. Intrusion of basaltic magma into a crystallizing granitic magma chamber: The Cordillera del Paine pluton in southern Chile

    Science.gov (United States)

    Michael, Peter J.

    1991-10-01

    The Cordillera del Paine pluton in the southernmost Andes of Chile represents a deeply dissected magma chamber where mafic magma intruded into crystallizing granitic magma. Throughout much of the 10x15 km pluton, there is a sharp and continuous boundary at a remarkably constant elevation of 1,100 m that separates granitic rocks (Cordillera del Paine or CP granite: 69 77% SiO2) which make up the upper levels of the pluton from mafic and comingled rocks (Paine Mafic Complex or PMC: 45 60% SiO2) which dominate the lower exposures of the pluton. Chilled, crenulate, disrupted contacts of mafic rock against granite demonstrate that partly crystallized granite was intruded by mafic magma which solidified prior to complete crystallization of the granitic magma. The boundary at 1,100 m was a large and stable density contrast between the denser, hotter mafic magma and cooler granitic magma. The granitic magma was more solidified near the margins of the chamber when mafic intrusion occurred, and the PMC is less disrupted by granites there. Near the pluton margins, the PMC grades upward irregularly from cumulate gabbros to monzodiorites. Mafic magma differentiated largely by fractional crystallization as indicated by the presence of cumulate rocks and by the low levels of compatible elements in most PMC rocks. The compositional gap between the PMC and CP granite indicates that mixing (blending) of granitic magma into the mafic magma was less important, although it is apparent from mineral assemblages in mafic rocks. Granitic magma may have incorporated small amounts of mafic liquid that had evolved to >60% SiO2 by crystallization. Mixing was inhibited by the extent of crystallization of the granite, and by the thermal contrast and the stable density contrast between the magmas. PMC gabbros display disequilibrium mineral assemblages including early formed zoned olivine (with orthopyroxene coronas), clinopyroxene, calcic plagioclase and paragasite and later-formed amphibole

  17. Ants of the Peloponnese, Greece (Hymenoptera: Formicidae

    Directory of Open Access Journals (Sweden)

    Borowiec Lech

    2017-09-01

    Full Text Available This paper relates to material obtained during two field trips to the Peloponnese in 2013 and 2016. With the inclusion of some hitherto unpublished ant material, it gives new records from a total of 92 sampling localities. 129 species (including morphospecies not attributed to any known taxon of ants have been recorded from the Peloponnese (southern Greece, 27 of which have been recorded from this region for the first time. Lasius reginae and 5 other morphospecies attributed only to species complexes are new to Greece.

  18. Pension Systems in Europe. Case of Greece

    Directory of Open Access Journals (Sweden)

    Jarosław Poteraj

    2007-09-01

    Full Text Available The article presents an insight into the old age pension system in Greece. The introduction is followed by four topic paragraphs: 1. the general information about the country, 2. the historical development of its pension system, 3. the present situation, and 4. challenges and foreseen changes. There, the authorís goal was to present both past and present solutions employed by the Greeceís pension system, in search for ideas worth consideration in international comparisons. In the summary, the author highlights as a particular Greek approach, on the background of other countries, the fact of existing in the Greek reality The National Actuary.

  19. Discovering Mathematics with Magma Reducing the Abstract to the Concrete

    CERN Document Server

    Bosma, Wieb

    2006-01-01

    With a design based on the ontology and semantics of algebra, Magma enables users to rapidly formulate and perform calculations in the more abstract parts of mathematics. This book introduces the role Magma plays in advanced mathematical research through 14 case studies which, in most cases, describe computations underpinning theoretical results.

  20. Zircons reveal magma fluxes in the Earth's crust.

    Science.gov (United States)

    Caricchi, Luca; Simpson, Guy; Schaltegger, Urs

    2014-07-24

    Magma fluxes regulate the planetary thermal budget, the growth of continents and the frequency and magnitude of volcanic eruptions, and play a part in the genesis and size of magmatic ore deposits. However, because a large fraction of the magma produced on the Earth does not erupt at the surface, determinations of magma fluxes are rare and this compromises our ability to establish a link between global heat transfer and large-scale geological processes. Here we show that age distributions of zircons, a mineral often present in crustal magmatic rocks, in combination with thermal modelling, provide an accurate means of retrieving magma fluxes. The characteristics of zircon age populations vary significantly and systematically as a function of the flux and total volume of magma accumulated in the Earth's crust. Our approach produces results that are consistent with independent determinations of magma fluxes and volumes of magmatic systems. Analysis of existing age population data sets using our method suggests that porphyry-type deposits, plutons and large eruptions each require magma input over different timescales at different characteristic average fluxes. We anticipate that more extensive and complete magma flux data sets will serve to clarify the control that the global heat flux exerts on the frequency of geological events such as volcanic eruptions, and to determine the main factors controlling the distribution of resources on our planet.

  1. U-series isotopes in arc magma

    Energy Technology Data Exchange (ETDEWEB)

    Hawkesworth, C.; Turner, S.; McDermott, F.; Peate, D.; Van Calsteren, P.

    1997-12-31

    Thorium is not readily mobilized in the fluid component along destructive plate margins. Uranium is mobilized, and the resultant fractionation in U/Th can be used to estimate the rates of transfer slab derived components through the mantle wedge. The variations in Th/Yb, and by implication in the fractionation-corrected Th abundances of arc magmas largely depend on the contributions from subducted sediments. It is inferred that the distinctive high Th/Ta ratios of subduction related magmas primarily reflect the Th/Ta ratios of the subducted sediments, and that such high Th/Ta ratios are generated by processes other than those associated with recent subduction-related magmatism. Uranium and thorium isotopes have also been used to evaluate magma residence times within the crust. Thus, separated minerals and groundmass from six rocks erupted in the last 4,000 years from Soufriere on St. Vincent in the Lesser Antilles, scatter about a 50,000 year errorchron on the U-Th equiline diagram (Heath et al., 1977). Models are currently being developed to investigate how such apparent ages may relate to calculated replenishment times in steady state systems. Bulk continental crust has a lower U/Th ratio (0.25) than at least some estimates for the bulk Earth (0.26) and the depleted upper mantle (0.39). However, the island arc rocks with low U/Th ratios appear to have inherited those from subducted sediments, and arc rocks with a low sediment contribution have significantly higher U/Th. Consequently, the U/Th ratios of new crustal material generated along destructive plate margins are significantly higher than those of bulk continental crust. The low average U/Th of bulk crust may be primarily due to different crust generation processes in the Archaean, when U would be less mobile because conditions were less oxidising, and when residual garnet may have had more of a role in crust generation processes. Extended abstract. 4 figs., 23 refs.

  2. Hydrogen isotopic fractionation during crystallization of the terrestrial magma ocean

    Science.gov (United States)

    Pahlevan, K.; Karato, S. I.

    2016-12-01

    Models of the Moon-forming giant impact extensively melt and partially vaporize the silicate Earth and deliver a substantial mass of metal to the Earth's core. The subsequent evolution of the terrestrial magma ocean and overlying vapor atmosphere over the ensuing 105-6 years has been largely constrained by theoretical models with remnant signatures from this epoch proving somewhat elusive. We have calculated equilibrium hydrogen isotopic fractionation between the magma ocean and overlying steam atmosphere to determine the extent to which H isotopes trace the evolution during this epoch. By analogy with the modern silicate Earth, the magma ocean-steam atmosphere system is often assumed to be chemically oxidized (log fO2 QFM) with the dominant atmospheric vapor species taken to be water vapor. However, the terrestrial magma ocean - having held metallic droplets in suspension - may also exhibit a much more reducing character (log fO2 IW) such that equilibration with the overlying atmosphere renders molecular hydrogen the dominant H-bearing vapor species. This variable - the redox state of the magma ocean - has not been explicitly included in prior models of the coupled evolution of the magma ocean-steam atmosphere system. We find that the redox state of the magma ocean influences not only the vapor speciation and liquid-vapor partitioning of hydrogen but also the equilibrium isotopic fractionation during the crystallization epoch. The liquid-vapor isotopic fractionation of H is substantial under reducing conditions and can generate measurable D/H signatures in the crystallization products but is largely muted in an oxidizing magma ocean and steam atmosphere. We couple equilibrium isotopic fractionation with magma ocean crystallization calculations to forward model the behavior of hydrogen isotopes during this epoch and find that the distribution of H isotopes in the silicate Earth immediately following crystallization represents an oxybarometer for the terrestrial

  3. Magma heating by decompression-driven crystallization beneath andesite volcanoes.

    Science.gov (United States)

    Blundy, Jon; Cashman, Kathy; Humphreys, Madeleine

    2006-09-07

    Explosive volcanic eruptions are driven by exsolution of H2O-rich vapour from silicic magma. Eruption dynamics involve a complex interplay between nucleation and growth of vapour bubbles and crystallization, generating highly nonlinear variation in the physical properties of magma as it ascends beneath a volcano. This makes explosive volcanism difficult to model and, ultimately, to predict. A key unknown is the temperature variation in magma rising through the sub-volcanic system, as it loses gas and crystallizes en route. Thermodynamic modelling of magma that degasses, but does not crystallize, indicates that both cooling and heating are possible. Hitherto it has not been possible to evaluate such alternatives because of the difficulty of tracking temperature variations in moving magma several kilometres below the surface. Here we extend recent work on glassy melt inclusions trapped in plagioclase crystals to develop a method for tracking pressure-temperature-crystallinity paths in magma beneath two active andesite volcanoes. We use dissolved H2O in melt inclusions to constrain the pressure of H2O at the time an inclusion became sealed, incompatible trace element concentrations to calculate the corresponding magma crystallinity and plagioclase-melt geothermometry to determine the temperature. These data are allied to ilmenite-magnetite geothermometry to show that the temperature of ascending magma increases by up to 100 degrees C, owing to the release of latent heat of crystallization. This heating can account for several common textural features of andesitic magmas, which might otherwise be erroneously attributed to pre-eruptive magma mixing.

  4. Longevity of magma in the near subsurface

    International Nuclear Information System (INIS)

    Marsh, B.D.; Resmini, R.G.

    1992-01-01

    Small, sporadic occurrences of basaltic volcanism are particularly difficult to evaluate in terms of long term threat to mankind because of their short overall eruptive history. Insight into future eruptive vigor and possible subsurface magma storage may be furnished by studying the ages of crystals in the eruptive products themselves. In this paper, the authors do this by applying the method of crystal size distribution theory (CSD) to a stack of basaltic lavas within the Nevada test site; namely the Dome Mtn. lavas. Preliminary results suggest a pre-eruptive residence time of 10 - 20 years, decreasing with decreasing age of lava within the sequence. These times are similar to those found by M.T. Mangan for the 1959 Kilauea (Hawaii) eruptions, and may suggest a relatively vigorous magmatic system at this time some 8 m.y. ago. Work is progressing on a greatly expanded CSD analysis of the Dome Mtn. lavas

  5. Permeability During Magma Expansion and Compaction

    Science.gov (United States)

    Gonnermann, Helge. M.; Giachetti, Thomas; Fliedner, Céline; Nguyen, Chinh T.; Houghton, Bruce F.; Crozier, Joshua A.; Carey, Rebecca J.

    2017-12-01

    Plinian lapilli from the 1060 Common Era Glass Mountain rhyolitic eruption of Medicine Lake Volcano, California, were collected and analyzed for vesicularity and permeability. A subset of the samples were deformed at a temperature of 975°, under shear and normal stress, and postdeformation porosities and permeabilities were measured. Almost all undeformed samples fall within a narrow range of vesicularity (0.7-0.9), encompassing permeabilities between approximately 10-15 m2 and 10-10 m2. A percolation threshold of approximately 0.7 is required to fit the data by a power law, whereas a percolation threshold of approximately 0.5 is estimated by fitting connected and total vesicularity using percolation modeling. The Glass Mountain samples completely overlap with a range of explosively erupted silicic samples, and it remains unclear whether the erupting magmas became permeable at porosities of approximately 0.7 or at lower values. Sample deformation resulted in compaction and vesicle connectivity either increased or decreased. At small strains permeability of some samples increased, but at higher strains permeability decreased. Samples remain permeable down to vesicularities of less than 0.2, consistent with a potential hysteresis in permeability-porosity between expansion (vesiculation) and compaction (outgassing). We attribute this to retention of vesicle interconnectivity, albeit at reduced vesicle size, as well as bubble coalescence during shear deformation. We provide an equation that approximates the change in permeability during compaction. Based on a comparison with data from effusively erupted silicic samples, we propose that this equation can be used to model the change in permeability during compaction of effusively erupting magmas.

  6. The Preparation of School Psychologists in Greece

    Science.gov (United States)

    Hatzichristou, Chryse; Polychroni, Fotini

    2014-01-01

    The paper describes the preparation of school psychologists in Greece. It discusses the social and cultural contexts that have influenced the evolution of the discipline of psychology, the beginning of training programs in school psychology, and the current status of school psychological services. The structure of the Graduate Program of School…

  7. Greece - energy situation 1986/87

    International Nuclear Information System (INIS)

    1988-01-01

    The energy situation of Greece is reviewed on the basis of relevant data. Data on the country's national and international energy policy are followed by an outline of trends in energy sources and electric power generation. Key figures are presented on the country's external trade and balance of payments. (UA) [de

  8. Cyanobacteria of Greece: an annotated checklist

    Science.gov (United States)

    Ourailidis, Iordanis; Panou, Manthos; Pappas, Nikos

    2016-01-01

    Abstract Background The checklist of Greek Cyanobacteria was created in the framework of the Greek Taxon Information System (GTIS), an initiative of the LifeWatchGreece Research Infrastructure (ESFRI) that has resumed efforts to compile a complete checklist of species reported from Greece. This list was created from exhaustive search of the scientific literature of the last 60 years. All records of taxa known to occur in Greece were taxonomically updated. New information The checklist of Greek Cyanobacteria comprises 543 species, classified in 130 genera, 41 families, and 8 orders. The orders Synechococcales and Oscillatoriales have the highest number of species (158 and 153 species, respectively), whereas these two orders along with Nostocales and Chroococcales cover 93% of the known Greek cyanobacteria species. It is worth mentioning that 18 species have been initially described from Greek habitats. The marine epilithic Ammatoidea aegea described from Saronikos Gulf is considered endemic to this area. Our bibliographic review shows that Greece hosts a high diversity of cyanobacteria, suggesting that the Mediterranean area is also a hot spot for microbes. PMID:27956851

  9. Cyanobacteria of Greece: an annotated checklist.

    Science.gov (United States)

    Gkelis, Spyros; Ourailidis, Iordanis; Panou, Manthos; Pappas, Nikos

    2016-01-01

    The checklist of Greek Cyanobacteria was created in the framework of the Greek Taxon Information System (GTIS), an initiative of the LifeWatchGreece Research Infrastructure (ESFRI) that has resumed efforts to compile a complete checklist of species reported from Greece. This list was created from exhaustive search of the scientific literature of the last 60 years. All records of taxa known to occur in Greece were taxonomically updated. The checklist of Greek Cyanobacteria comprises 543 species, classified in 130 genera, 41 families, and 8 orders. The orders Synechococcales and Oscillatoriales have the highest number of species (158 and 153 species, respectively), whereas these two orders along with Nostocales and Chroococcales cover 93% of the known Greek cyanobacteria species. It is worth mentioning that 18 species have been initially described from Greek habitats. The marine epilithic Ammatoidea aegea described from Saronikos Gulf is considered endemic to this area. Our bibliographic review shows that Greece hosts a high diversity of cyanobacteria, suggesting that the Mediterranean area is also a hot spot for microbes.

  10. Higher Education in Greece Compared to Canada

    Science.gov (United States)

    Miliotis, Helen

    2014-01-01

    This paper compares and contrasts higher education in Canada and Greece. An overview of the systems in place is followed by an analysis centred on the triad of funding, access and quality. Similarities and differences are highlighted, and the current challenges and issues faced by both nations will be examined, especially in terms of world…

  11. The Cost of Living in Ancient Greece

    Directory of Open Access Journals (Sweden)

    Roberto Morales Harley

    2014-11-01

    Full Text Available The paper focuses on the most relevant economic aspects of Ancient Greece, more specifically, 5th century BC Athens. It explores the Greek notion of economy, the monetary system, the financial administration and the labor market, in order to contextualize the cost of living. The examples on this matter take into account the products’ costs and the people’s wages.

  12. Variations in magma supply rate at Kilauea Volcano, Hawaii

    Science.gov (United States)

    Dvorak, John J.; Dzurisin, Daniel

    1993-01-01

    When an eruption of Kilauea lasts more than 4 months, so that a well-defined conduit has time to develop, magma moves freely through the volcano from a deep source to the eruptive site at a constant rate of 0.09 km3/yr. At other times, the magma supply rate to Kilauea, estimated from geodetic measurements of surface displacements, may be different. For example, after a large withdrawal of magma from the summit reservoir, such as during a rift zone eruption, the magma supply rate is high initially but then lessens and exponentially decays as the reservoir refills. Different episodes of refilling may have different average rates of magma supply. During four year-long episodes in the 1960s, the annual rate of refilling varied from 0.02 to 0.18 km3/yr, bracketing the sustained eruptive rate of 0.09 km3/yr. For decade-long or longer periods, our estimate of magma supply rate is based on long-term changes in eruptive rate. We use eruptive rate because after a few dozen eruptions the volume of magma that passes through the summit reservoir is much larger than the net change of volume of magma stored within Kilauea. The low eruptive rate of 0.009 km3/yr between 1840 and 1950, compared to an average eruptive rate of 0.05 km3/yr since 1950, suggests that the magma supply rate was lower between 1840 and 1950 than it has been since 1950. An obvious difference in activity before and since 1950 was the frequency of rift zone eruptions: eight rift zone eruptions occurred between 1840 and 1950, but more than 20 rift zone eruptions have occurred since 1950. The frequency of rift zone eruptions influences magma supply rate by suddenly lowering pressure of the summit magma reservoir, which feeds magma to rift zone eruptions. A temporary drop of reservoir pressure means a larger-than-normal pressure difference between the reservoir and a deeper source, so magma is forced to move upward into Kilauea at a faster rate.

  13. Drilling Magma for Science, Volcano Monitoring, and Energy

    Science.gov (United States)

    Eichelberger, J. C.; Lavallée, Y.; Blankenship, D.

    2017-12-01

    Magma chambers are central to understanding magma evolution, formation of continental crust, volcanism, and renewal of hydrothermal systems. Information from geology, petrology, laboratory experiments, and geophysical imagery has led to little consensus except a trend to see magma systems as being crystal-dominant (mush) rather than melt dominant. At high melt viscosities, crystal-liquid fractionation may be achieved by separation of melt from mush rather than crystals from liquid suspension. That the dominant volume has properties more akin to solid than liquid might explain the difficulty in detecting magma geophysically. Recently, geothermal drilling has intersected silicic magma at the following depths and SiO2 contents are: Puna, Hawaii, 2.5 km, 67 wt%; Menengai, Kenya 2.1 km, 67 wt%; Krafla, Iceland, 2.1 km, 75 wt%. Some similarities are: 1) Drillers encountered a "soft", sticky formation; 2) Cuttings or chips of clear quenched glass were recovered; 3) The source of the glass flowed up the well; 4) Transition from solid rock to recovering crystal-poor glass occurred in tens of meters, apparently without an intervening mush zone. Near-liquidus magma at the roof despite rapid heat loss there presents a paradox that may be explained by very recent intrusion of magma, rise of liquidus magma to the roof replacing partially crystallized magma, or extremely skewed representation of melt over mush in cuttings (Carrigan et al, this session). The latter is known to occur by filter pressing of ooze into lava lake coreholes (Helz, this session), but cannot be verified in actual magma without coring. Coring to reveal gradients in phase composition and proportions is required for testing any magma chamber model. Success in drilling into and controlling magma at all three locations, in coring lava lakes to over 1100 C, and in numerical modeling of coring at Krafla conditions (Su, this session) show this to be feasible. Other unprecedented experiments are using the known

  14. MAGMA: analysis of two-channel microarrays made easy.

    Science.gov (United States)

    Rehrauer, Hubert; Zoller, Stefan; Schlapbach, Ralph

    2007-07-01

    The web application MAGMA provides a simple and intuitive interface to identify differentially expressed genes from two-channel microarray data. While the underlying algorithms are not superior to those of similar web applications, MAGMA is particularly user friendly and can be used without prior training. The user interface guides the novice user through the most typical microarray analysis workflow consisting of data upload, annotation, normalization and statistical analysis. It automatically generates R-scripts that document MAGMA's entire data processing steps, thereby allowing the user to regenerate all results in his local R installation. The implementation of MAGMA follows the model-view-controller design pattern that strictly separates the R-based statistical data processing, the web-representation and the application logic. This modular design makes the application flexible and easily extendible by experts in one of the fields: statistical microarray analysis, web design or software development. State-of-the-art Java Server Faces technology was used to generate the web interface and to perform user input processing. MAGMA's object-oriented modular framework makes it easily extendible and applicable to other fields and demonstrates that modern Java technology is also suitable for rather small and concise academic projects. MAGMA is freely available at www.magma-fgcz.uzh.ch.

  15. Magnetotelluric Investigation of the South Aegean Volcanic Arc, Greece

    Science.gov (United States)

    Kalisperi, Despina; Romano, Gerardo; Smirnov, Maxim; Kouli, Maria; Perrone, Angela; Makris, John P.; Vallianatos, Filippos

    2014-05-01

    The South Aegean Volcanic Arc (SAVA) is a chain of volcanic islands in the South Aegean resulting from the subduction of the African tectonic plate beneath the Eurasian plate. It extends from Methana, northwest, to the Island of Nisyros southeast (450 km total length). SAVA comprises a series of dormant and historically active volcanoes, with the most prominent to be Aegina, Methana, Milos, Santorini, Kolumbo, Kos and Nisyros. The aim of the ongoing research project "MagnetoTellurics in studying Geodynamics of the hEllenic ARc (MT-GEAR)" is to contribute to the investigation of the geoelectric structure of Southern Aegean, and particularly to attempt to image the Hellenic Subduction Zone. In this context, onshore magnetotelluric (MT) measurements were recently carried out on the central and eastern part of SAVA (Milos, Santorini, Nisyros and Kos Islands). Data were collected using two MT systems running simultaneously plus a remote reference station installed in Omalos plateau (Western Crete). Robust MT data analysis of the broad-band MT soundings and the resulting model of the conductivity structure of the South Aegean Volcanic Arc is presented. The research is co-funded by the European Social Fund (ESF) and National Resources under the Operational Programme 'Education and Lifelong Learning (EdLL) within the context of the Action 'Supporting Postdoctoral Researchers' in the framework of the project title "MagnetoTellurics in studying Geodynamics of the hEllenic ARc (MT-GEAR)".

  16. The marine isotope stage 1-5 cryptotephra record of Tenaghi Philippon, Greece: Towards a detailed tephrostratigraphic framework for the Eastern Mediterranean region

    Science.gov (United States)

    Wulf, Sabine; Hardiman, Mark J.; Staff, Richard A.; Koutsodendris, Andreas; Appelt, Oona; Blockley, Simon P. E.; Lowe, J. John; Manning, Christina J.; Ottolini, Luisa; Schmitt, Axel K.; Smith, Victoria C.; Tomlinson, Emma L.; Vakhrameeva, Polina; Knipping, Maria; Kotthoff, Ulrich; Milner, Alice M.; Müller, Ulrich C.; Christanis, Kimon; Kalaitzidis, Stavros; Tzedakis, Polychronis C.; Schmiedl, Gerhard; Pross, Jörg

    2018-04-01

    The iconic climate archive of Tenaghi Philippon (TP), NE Greece, allows the study of short-term palaeoclimatic and environmental change throughout the past 1.3 Ma. To provide high-quality age control for detailed palaeoclimate reconstructions based on the TP archive, (crypto)tephra studies of a peat core 'TP-2005' have been carried out for the 0-130 ka interval. The results show that the TP basin is ideally positioned to receive tephra fall from both the Italian and Aegean Arc volcanic provinces. Two visible tephra layers, the Santorini Cape Riva/Y-2 (c. 22 ka) and the Campanian Ignimbrite (CI)/Y-5 (c. 39.8 ka) tephras, and six primary cryptotephra layers, namely the early Holocene E1 tephra from the Aeolian Islands (c. 8.3 ka), the Campanian Y-3 (c. 29 ka) and X-6 tephras (c. 109.5 ka), as well as counterpart tephras TM-18-1d (c. 40.4 ka), TM-23-11 (c. 92.4 ka) and TM-33-1a (c. 116.7 ka) from the Lago Grande di Monticchio sequence (southern Italy), were identified along with repeatedly redeposited Y-2 and CI tephra material. Bayesian modelling of the ages of seven of the primary tephra layers, 60 radiocarbon measurements and 20 palynological control points have been applied to markedly improve the chronology of the TP archive. This revised chronology constrains the age of tephra TM-18-1d to 40.90-41.66 cal ka BP (95.4% range). Several tephra layers identified in the TP record form important isochrons for correlating this archive with other terrestrial (e.g., Lago Grande di Monticchio, Sulmona Basin and Lake Ohrid) and marine (e.g., Adriatic Sea core PRAD 1-2 and Aegean Sea core LC21) palaeoclimate records in the Mediterranean region.

  17. Magma paths at Piton de la Fournaise Volcano

    OpenAIRE

    Michon , Laurent; Ferrazzini , Valérie; Di Muro , Andrea

    2016-01-01

    International audience; Several patterns of magma paths have been proposed since the 1980s for Piton de la Fournaise volcano. Given the significant differences, which are presented here, we propose a reappraisal of the magma intrusion paths using a 17-years-long database of volcano-tectonic seismic events and a detailed mapping of the scoria cones. At the edifice scale, the magma propagates along two N120 trending rift zones. They are wide, linear, spotted by small to large scoria cones and r...

  18. Magma Expansion and Fragmentation in a Propagating Dike (Invited)

    Science.gov (United States)

    Jaupart, C. P.; Taisne, B.

    2010-12-01

    The influence of magma expansion due to volatile exsolution and gas dilation on dike propagation is studied using a new numerical code. Many natural magmas contain sufficient amounts of volatiles for fragmentation to occur well below Earth's surface. Magma fragmentation has been studied for volcanic flows through open conduits but it should also occur within dikes that rise towards Earth's surface. We consider the flow of a volatile-rich magma in a hydraulic fracture. The mixture of melt and gas is treated as a compressible viscous fluid below the fragmentation level and as a gas phase carrying melt droplets above it. A numerical code solves for elastic deformation of host rocks, the flow of the magmatic mixture and fracturing at the dike tip. With volatile-free magma, a dike fed at a constant rate in a uniform medium adopts a constant shape and width and rises at a constant velocity. With volatiles involved, magma expands and hence the volume flux of magma increases. With no fragmentation, this enhanced flux leads to acceleration of the dike. Simple scaling laws allow accurate predictions of dike width and ascent rate for a wide range of conditions. With fragmentation, dike behavior is markedly different. Due to the sharp drop of head loss that occurs in gas-rich fragmented material, large internal overpressures develop below the tip and induce swelling of the nose region, leading to deceleration of the dike. Thus, the paradoxical result is that, with no viscous impediment on magma flow and a large buoyancy force, the dike stalls. This process may account for some of the tuffisite veins and intrusions that are found in and around magma conduits, notably in the Unzen drillhole, Japan. We apply these results to the two-month long period of volcanic unrest that preceded the May 1980 eruption of Mount St Helens. An initial phase of rapid earthquake migration from the 7-8 km deep reservoir to shallow levels was followed by very slow progression of magma within the

  19. Short-circuiting magma differentiation from basalt straight to rhyolite?

    Science.gov (United States)

    Ruprecht, P.; Winslow, H.

    2017-12-01

    Silicic magmas are the product of varying degrees of crystal fractionation and crustal assimilation/melting. Both processes lead to differentiation that is step-wise rather than continuous for example during melt separation from a crystal mush (Dufek and Bachmann, 2010). However, differentiation is rarely efficient enough to evolve directly from a basaltic to a rhyolitic magma. At Volcán Puyehue-Cordón Caulle, Chile, the magma series is dominated by crystal fractionation where mixing trends between primitive and felsic end members in the bulk rock compositions are almost absent (e.g. P, FeO, TiO2 vs. SiO2). How effective fraction is in this magmatic system is not well-known. The 2011-12 eruption at Cordón Caulle provides new constraints that rhyolitic melts may be derived directly from a basaltic mush. Minor, but ubiquitous mafic, crystal-rich enclaves co-erupted with the predominantly rhyolitic near-aphyric magma. These enclaves are among the most primitive compositions erupted at Puyehue-Cordón Caulle and geochemically resemble closely basaltic magmas that are >10 ka old (Singer et al. 2008) and that have been identified as a parental tholeiitic mantle-derived magma (Schmidt and Jagoutz, 2017) for the Southern Andean Volcanic Zone. The vesiculated nature, the presence of a microlite-rich groundmass, and a lack of a Eu anomaly in these encalves suggest that they represent recharge magma/mush rather than sub-solidus cumulates and therefore have potentially a direct petrogenetic link to the erupted rhyolites. Our results indicate that under some conditions crystal fractionation can be very effective and the presence of rhyolitic magmas does not require an extensive polybaric plumbing system. Instead, primitive mantle-derived magmas source directly evolved magmas. In the case, of the magma system beneath Puyehue-Cordón Caulle, which had three historic rhyolitic eruptions (1921-22, 1960, 2011-12) these results raise the question whether rhyolite magma extraction

  20. Genesis of felsic plutonic magmas and their igneous enclaves

    DEFF Research Database (Denmark)

    Clemens, John D.; Maas, Roland; Waight, Tod Earle

    2016-01-01

    -type Pyalong pluton was emplaced, apparently along an east-west-orientated fracture zone. Around 367 Ma, the main I-type Baynton pluton intruded as numerous shallow-dipping sheets. The last plutonic event was the intrusion of the broad, thin, flat-lying, and crosscutting sheet of the I-type Beauvallet pluton...... the relatively high abundance of igneous-textured microgranular enclaves (MEs). The MEs show neither chemical nor isotope mixing trends with each other or with the host magmas. Variations in the Baynton magmas were derived from the heterogeneity of the source terrane, with individual magma batches formed from...

  1. Why Is There an Abrupt Transition from Solid Rock to Low Crystallinity Magma in Drilled Magma Bodies?

    Science.gov (United States)

    Eichelberger, J. C.; Carrigan, C. R.; Sun, Y.; Lavallée, Y.

    2017-12-01

    We report on a preliminary evaluation, from basic principles of heat and mass transfer, on the unexpectedly abrupt transition from cuttings of solid rock to fragments of crystal poor glass during drilling into magma bodies. Our analysis is based on conditions determined and inferred for the 2009 IDDP-1 well in Krafla Caldera, which entered apparently liquidus rhyolite magma at about 900oC at a depth of 2104 m. Simple conduction would predict some 30 m of crystallization and partial crystallization since the latest time the magma could have been intruded, approximately 30 years prior to discovery by drilling. Option 1: The expected crystallization of magma has occurred but interstitial melt remains. The pressure difference between lithostatic load of about 50 MPa on the mush and 20 MPa hydrostatic pressure in the well causes pore melt to flow from the permeable mush into the borehole, where it becomes the source of the quenched melt chips. To be viable, this mechanism must work over the time frame of a day. Option 2: The expected crystallization is occurring, but high Rayleigh number thermal convection in the magma chamber continuously displaces crystallizing roof magma by liquidus magma from the interior of the body. To be viable, this mechanism must result in overturning magma in the chamber on a time scale that is much shorter than that of crystallization. Option 3: Flow-induced crystal migration away from zones of high shear created during drilling into magma may preferentially produce low-crystal-content melt at the boundary of the borehole, which is then sampled.

  2. Tsunami disaster risk management capabilities in Greece

    Science.gov (United States)

    Marios Karagiannis, Georgios; Synolakis, Costas

    2015-04-01

    Greece is vulnerable to tsunamis, due to the length of the coastline, its islands and its geographical proximity to the Hellenic Arc, an active subduction zone. Historically, about 10% of all world tsunamis occur in the Mediterranean region. Here we review existing tsunami disaster risk management capabilities in Greece. We analyze capabilities across the disaster management continuum, including prevention, preparedness, response and recovery. Specifically, we focus on issues like legal requirements, stakeholders, hazard mitigation practices, emergency operations plans, public awareness and education, community-based approaches and early-warning systems. Our research is based on a review of existing literature and official documentation, on previous projects, as well as on interviews with civil protection officials in Greece. In terms of tsunami disaster prevention and hazard mitigation, the lack of tsunami inundation maps, except for some areas in Crete, makes it quite difficult to get public support for hazard mitigation practices. Urban and spatial planning tools in Greece allow the planner to take into account hazards and establish buffer zones near hazard areas. However, the application of such ordinances at the local and regional levels is often difficult. Eminent domain is not supported by law and there are no regulatory provisions regarding tax abatement as a disaster prevention tool. Building codes require buildings and other structures to withstand lateral dynamic earthquake loads, but there are no provisions for resistance to impact loading from water born debris Public education about tsunamis has increased during the last half-decade but remains sporadic. In terms of disaster preparedness, Greece does have a National Tsunami Warning Center (NTWC) and is a Member of UNESCO's Tsunami Program for North-eastern Atlantic, the Mediterranean and connected seas (NEAM) region. Several exercises have been organized in the framework of the NEAM Tsunami Warning

  3. Coastal erosion and accretion rates in Greece

    Science.gov (United States)

    Foteinis, Spyros; Papadopoulos, Costas; Koutsogiannaki, Irini; Synolakis, Costas

    2010-05-01

    Erosion threatens many coastal regions of Greece. Anthropogenic changes of landforms such as coastal roads built on even narrow beaches, sand mining for construction, poor design of coastal structures that interfere with sediment, and dams without sediment bypasses have significantly reduced beach widths. We present erosion rates for different beaches, some of which are in sensitive ecosystems, otherwise "protected" by local and EU ordinances. By comparing inferences of beach widths in varying intervals from 1933 to 2006, we infer that the construction of dams in Acheloos river in western Greece, built in a faraonic attempt to partially divert its flows to eastern Greece, this is responsible for up to 20m/year erosion rates observed in certain locales in the Acheloos delta. More characteristic erosion rates in the region are ~ 2m/year. By contrast, there appears rapid accretion of up to 4m/year in the beaches around the Nestos delta in northern Greece (Papadopoulos, 2009). In beaches that are not near large river deltas, erosion rates range from 0.5m/year to 1m/year. While we have not done comprehensive comparisons among coastlines with different levels of coastal development, it does appear that rapid coastal development correlates well with erosion rates. The underlying problem is the complete lack of any semblance of coastal zone management in Greece and substandard design of coastal structures, which are often sited without any measurements of waves and currents offshore (Synolakis et al, 2008). Beach maintenance remains an exotic concept for most local authorities, who invariably prefer to build hard coastal structures to "protect" versus nourish, siting lack of experience with nourishment and "environmental" concerns. In certain cases, choices are dictated by costs, the larger the cost the easier the project gets approved by regulatory authorities, hence the preference for concrete or rubble structures. We conclude that, unless urgent salvage measures are

  4. Water Partitioning in Planetary Embryos and Protoplanets with Magma Oceans

    Science.gov (United States)

    Ikoma, M.; Elkins-Tanton, L.; Hamano, K.; Suckale, J.

    2018-06-01

    The water content of magma oceans is widely accepted as a key factor that determines whether a terrestrial planet is habitable. Water ocean mass is determined as a result not only of water delivery and loss, but also of water partitioning among several reservoirs. Here we review our current understanding of water partitioning among the atmosphere, magma ocean, and solid mantle of accreting planetary embryos and protoplanets just after giant collisions. Magma oceans are readily formed in planetary embryos and protoplanets in their accretion phase. Significant amounts of water are partitioned into magma oceans, provided the planetary building blocks are water-rich enough. Particularly important but still quite uncertain issues are how much water the planetary building blocks contain initially and how water goes out of the solidifying mantle and is finally degassed to the atmosphere. Constraints from both solar-system explorations and exoplanet observations and also from laboratory experiments are needed to resolve these issues.

  5. Understanding the rheology of two and three-phase magmas

    Science.gov (United States)

    Coats, R.; Cai, B.; Kendrick, J. E.; Wallace, P. A.; Hornby, A. J.; Miwa, T.; von Aulock, F. W.; Ashworth, J. D.; Godinho, J.; Atwood, R. C.; Lee, P. D.; Lavallée, Y.

    2017-12-01

    The rheology of magma plays a fundamental role in determining the style of a volcanic eruption, be it explosive or effusive. Understanding how magmas respond to changes in stress/ strain conditions may help to enhance eruption forecast models. The presence of crystals and bubbles in magmas alter the viscosity of suspensions and favor a non-Newtonian response. Thus, with the aim of grasping the rheological behavior of volcanic materials, uniaxial compressive tests were performed on natural and synthetic samples. A suite of variably porous (10-32 vol.%), highly crystalline ( 50 vol.%) dacite from the 1991-95 eruption of Mt Unzen, Japan, was selected as the natural material, while synthetic samples were sintered with desired porosities (Diamond Light Source. Unexpectedly, these observations suggest that fractures nucleate in crystals due to crystal interactions, before propagating through the interstitial melt. This ongoing study promises to uncover the way crystal-bearing magmas flow or fail, necessary to constrain magmatic processes and volcanic hazards.

  6. Implications of magma transfer between multiple reservoirs on eruption cycling.

    Science.gov (United States)

    Elsworth, Derek; Mattioli, Glen; Taron, Joshua; Voight, Barry; Herd, Richard

    2008-10-10

    Volcanic eruptions are episodic despite being supplied by melt at a nearly constant rate. We used histories of magma efflux and surface deformation to geodetically image magma transfer within the deep crustal plumbing of the Soufrière Hills volcano on Montserrat, West Indies. For three cycles of effusion followed by discrete pauses, supply of the system from the deep crust and mantle was continuous. During periods of reinitiated high surface efflux, magma rose quickly and synchronously from a deflating mid-crustal reservoir (at about 12 kilometers) augmented from depth. During repose, the lower reservoir refilled from the deep supply, with only minor discharge transiting the upper chamber to surface. These observations are consistent with a model involving the continuous supply of magma from the deep crust and mantle into a voluminous and compliant mid-crustal reservoir, episodically valved below a shallow reservoir (at about 6 kilometers).

  7. Production and Preservation of Sulfide Layering in Mercury's Magma Ocean

    Science.gov (United States)

    Boukare, C.-E.; Parman, S. W.; Parmentier, E. M.; Anzures, B. A.

    2018-05-01

    Mercury's magma ocean (MMO) would have been sulfur-rich. At some point during MMO solidification, it likely became sulfide saturated. Here we present physiochemical models exploring sulfide layer formation and stability.

  8. Magma chamber processes in central volcanic systems of Iceland

    DEFF Research Database (Denmark)

    Þórarinsson, Sigurjón Böðvar; Tegner, Christian

    2009-01-01

    are composed of 2-10 m thick melanocratic layers rich in clinopyroxene and sometimes olivine, relative to the thicker overlying leucocratic oxide gabbros. While the overall compositional variation is limited (Mg# clinopyroxene 72-84; An% plagioclase 56-85), the melanocratic bases display spikes in Mg# and Cr2O......3 of clinopyroxene and magnetite indicative of magma replenishment. Some macrorhythmic units show mineral trends indicative of up-section fractional crystallisation over up to 100 m, whereas others show little variation. Two populations of plagioclase crystals (large, An-rich and small, less An......-rich) indicate that the recharge magma carried plagioclase xenocrysts (high An-type). The lack of evolved gabbros suggests formation in a dynamic magma chamber with frequent recharge, tapping and fractionation. Modelling of these compositional trends shows that the parent magma was similar to known transitional...

  9. Seismic Tremors and Three-Dimensional Magma Wagging

    Science.gov (United States)

    Liao, Y.; Bercovici, D.

    2015-12-01

    Seismic tremor is a feature shared by many silicic volcanoes and is a precursor of volcanic eruption. Many of the characteristics of tremors, including their frequency band from 0.5 Hz to 7 Hz, are common for volcanoes with very different geophysical and geochemical properties. The ubiquitous characteristics of tremor imply that it results from some generation mechanism that is common to all volcanoes, instead of being unique to each volcano. Here we present new analysis on the magma-wagging mechanism that has been proposed to generate tremor. The model is based on the suggestion given by previous work (Jellinek & Bercovici 2011; Bercovici et.al. 2013) that the magma column is surrounded by a compressible, bubble-rich foam annulus while rising inside the volcanic conduit, and that the lateral oscillation of the magma inside the annulus causes observable tremor. Unlike the previous two-dimensional wagging model where the displacement of the magma column is restricted to one vertical plane, the three-dimensional model we employ allows the magma column to bend in different directions and has angular motion as well. Our preliminary results show that, without damping from viscous deformation of the magma column, the system retains angular momentum and develops elliptical motion (i.e., the horizontal displacement traces an ellipse). In this ''inviscid'' limit, the magma column can also develop instabilities with higher frequencies than what is found in the original two-dimensional model. Lateral motion can also be out of phase for various depths in the magma column leading to a coiled wagging motion. For the viscous-magma model, we predict a similar damping rate for the uncoiled magma column as in the two-dimensional model, and faster damping for the coiled magma column. The higher damping thus requires the existence of a forcing mechanism to sustain the oscillation, for example the gas-driven Bernoulli effect proposed by Bercovici et al (2013). Finally, using our new 3

  10. Magma chamber interaction giving rise to asymmetric oscillations

    Science.gov (United States)

    Walwer, D.; Ghil, M.; Calais, E.

    2017-12-01

    Geodetic time series at four volcanoes (Okmok, Akutan, Shishaldin, and Réunion) are processed using Multi-channel Singular Spectrum Analysis (M-SSA) and reveal sawtooth-shaped oscillations ; the latter are characterized by short intervals of fast inflations followed by longer intervals of slower deflations. At Okmok and Akutan, the oscillations are first damped and then accentuated. At Okmok, the increase in amplitude of the oscillations is followed by an eruption. We first show that the dynamics of these four volcanoes bears similarities with that of a simple nonlinear, dissipative oscillator, indicating that the inflation-deflation episodes are relaxation oscillations. These observations imply that ab initio dynamical models of magma chambers should possess an asymmetric oscillatory regime. Next, based on the work of Whitehead and Helfrich [1991], we show that a model of two magma chambers — connected by a cylindrical conduit in which the magma viscosity depends on temperature — gives rise to asymmetric overpressure oscillations in the magma reservoirs. These oscillations lead to surface deformations that are consistent with those observed at the four volcanoes in this study. This relaxation oscillation regime occurs only when the vertical temperature gradient in the host rock between the two magma chambers is large enough and when the magma flux entering the volcanic system is sufficiently high. The magma being supplied by a deeper source region, the input flux depends on the pressure difference between the source and the deepest reservoir. When this difference is not sufficiently high, the magma flux exponentially decreases, leading to damped oscillations as observed at Akutan and Okmok. The combination of observational and modeling results clearly supports the role of relaxation oscillations in the dynamics of volcanic systems.

  11. Crystalline heterogeneities and instabilities in thermally convecting magma chamber

    Science.gov (United States)

    Culha, C.; Suckale, J.; Qin, Z.

    2016-12-01

    A volcanic vent can supply different densities of crystals over an eruption time period. This has been seen in Hawai'i's Kilauea Iki 1959 eruption; however it is not common for all Kilauea or basaltic eruptions. We ask the question: Under what conditions can homogenous magma chamber cultivate crystalline heterogeneities? In some laboratory experiments and numerical simulations, a horizontal variation is observed. The region where crystals reside is identified as a retention zone: convection velocity balances settling velocity. Simulations and experiments that observe retention zones assume crystals do not alter the convection in the fluid. However, a comparison of experiments and simulations of convecting magma with crystals suggest that large crystal volume densities and crystal sizes alter fluid flow considerably. We introduce a computational method that fully resolves the crystalline phase. To simulate basaltic magma chambers in thermal convection, we built a numerical solver of the Navier-Stoke's equation, continuity equation, and energy equation. The modeled magma is assumed to be a viscous, incompressible fluid with a liquid and solid phase. Crystals are spherical, rigid bodies. We create Rayleigh-Taylor instability through a cool top layer and hot bottom layer and update magma density while keeping crystal temperature and size constant. Our method provides a detailed picture of magma chambers, which we compare to other models and experiments to identify when and how crystals alter magma chamber convection. Alterations include stratification, differential settling and instabilities. These characteristics are dependent on viscosity, convection vigor, crystal volume density and crystal characteristics. We reveal that a volumetric crystal density variation may occur over an eruption time period, if right conditions are met to form stratifications and instabilities in magma chambers. These conditions are realistic for Kilauea Iki's 1959 eruption.

  12. Experimental Fractional Crystallization of the Lunar Magma Ocean

    Science.gov (United States)

    Rapp, J. F.; Draper, D. S.

    2012-01-01

    The current paradigm for lunar evolution is of crystallization of a global scale magma ocean, giving rise to the anorthositic crust and mafic cumulate interior. It is thought that all other lunar rocks have arisen from this differentiated interior. However, until recently this paradigm has remained untested experimentally. Presented here are the first experimental results of fractional crystallization of a Lunar Magma Ocean (LMO) using the Taylor Whole Moon (TWM) bulk lunar composition [1].

  13. Magma Dynamics at Yucca Mountain, Nevada

    International Nuclear Information System (INIS)

    D. Krier

    2005-01-01

    Small-volume basaltic volcanic activity at Yucca Mountain has been identified as one of the potential events that could lead to release of radioactive material from the U.S. Department of Energy (DOE) designated nuclear waste repository at Yucca Mountain. Release of material could occur indirectly as a result of magmatic dike intrusion into the repository (with no associated surface eruption) by changing groundwater flow paths, or as a result of an eruption (dike intrusion of the repository drifts, followed by surface eruption of contaminated ash) or volcanic ejection of material onto the Earth's surface and the redistribution of contaminated volcanic tephra. Either release method includes interaction between emplacement drifts and a magmatic dike or conduit, and natural (geologic) processes that might interrupt or halt igneous activity. This analysis provides summary information on two approaches to evaluate effects of disruption at the repository by basaltic igneous activity: (1) descriptions of the physical geometry of ascending basaltic dikes and their interaction with silicic host rocks similar in composition to the repository host rocks; and (2) a summary of calculations developed to quantify the response of emplacement drifts that have been flooded with magma and repressurized following blockage of an eruptive conduit. The purpose of these analyses is to explore the potential consequences that could occur during the full duration of an igneous event

  14. Magma Dynamics at Yucca Mountain, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    D. Krier

    2005-08-29

    Small-volume basaltic volcanic activity at Yucca Mountain has been identified as one of the potential events that could lead to release of radioactive material from the U.S. Department of Energy (DOE) designated nuclear waste repository at Yucca Mountain. Release of material could occur indirectly as a result of magmatic dike intrusion into the repository (with no associated surface eruption) by changing groundwater flow paths, or as a result of an eruption (dike intrusion of the repository drifts, followed by surface eruption of contaminated ash) or volcanic ejection of material onto the Earth's surface and the redistribution of contaminated volcanic tephra. Either release method includes interaction between emplacement drifts and a magmatic dike or conduit, and natural (geologic) processes that might interrupt or halt igneous activity. This analysis provides summary information on two approaches to evaluate effects of disruption at the repository by basaltic igneous activity: (1) descriptions of the physical geometry of ascending basaltic dikes and their interaction with silicic host rocks similar in composition to the repository host rocks; and (2) a summary of calculations developed to quantify the response of emplacement drifts that have been flooded with magma and repressurized following blockage of an eruptive conduit. The purpose of these analyses is to explore the potential consequences that could occur during the full duration of an igneous event.

  15. The consequences of the Chernobyl nuclear accident in Greece

    International Nuclear Information System (INIS)

    1986-07-01

    In this report the radioactive fallout on Greece from the Chernobyl nuclear accident is described. The flow pattern to Greece of the radioactive materials released, the measurements performed on environmental samples and samples of the food chain, as well as some estimations of the population doses and of the expected consequences of the accident are presented. The analysis has shown that the radiological impact of the accident in Greece can be considered minor. (J.K.)

  16. The fluid dynamics of a basaltic magma chamber replenished by influx of hot, dense ultrabasic magma

    Science.gov (United States)

    Huppert, Herbert E.; Sparks, R. Stephen J.

    1981-09-01

    This paper describes a fluid dynamical investigation of the influx of hot, dense ultrabasic magma into a reservoir containing lighter, fractionated basaltic magma. This situation is compared with that which develops when hot salty water is introduced under cold fresh water. Theoretical and empirical models for salt/water systems are adapted to develop a model for magmatic systems. A feature of the model is that the ultrabasic melt does not immediately mix with the basalt, but spreads out over the floor of the chamber, forming an independent layer. A non-turbulent interface forms between this layer and the overlying magma layer across which heat and mass are transferred by the process of molecular diffusion. Both layers convect vigorously as heat is transferred to the upper layer at a rate which greatly exceeds the heat lost to the surrounding country rock. The convection continues until the two layers have almost the same temperature. The compositions of the layers remain distinct due to the low diffusivity of mass compared to heat. The temperatures of the layers as functions of time and their cooling rate depend on their viscosities, their thermal properties, the density difference between the layers and their thicknesses. For a layer of ultrabasic melt (18% MgO) a few tens of metres thick at the base of a basaltic (10% MgO) magma chamber a few kilometres thick, the temperature of the layers will become nearly identical over a period of between a few months and a few years. During this time the turbulent convective velocities in the ultrabasic layer are far larger than the settling velocity of olivines which crystallise within the layer during cooling. Olivines only settle after the two layers have nearly reached thermal equilibrium. At this stage residual basaltic melt segregates as the olivines sediment in the lower layer. Depending on its density, the released basalt can either mix convectively with the overlying basalt layer, or can continue as a separate

  17. The plight of the beaches of Greece

    Science.gov (United States)

    Ewing, L.; Foteinis, S.; Kalligeris, N.; Palaiologou, A.; Synolakis, C. E.

    2008-12-01

    The coastlines of the Greece are rapidly retreating at a rate that has increased substantially in the past decade. We describe here specific examples of rapid erosion and we speculate as to the causes. In some instances, erosion is advancing at a rate of 1m/year. As in other parts of the Mediterranean, the causes are anthropogenic and include sand mining from the beaches and rivers, poor design of coastal structures that create reflection patterns that focus waves on vulnerable areas, removal of sand dunes to build roads, and coastal construction too close to shoreline. The underlying problem is the complete lack of any semblance of coastal zone management in Greece and antiquated legislation. We conclude that unless urgent salvage measures to protect the beaches and end sand mining and dune removal, several beaches will disappear within the next decade.

  18. Assessing the PV business opportunities in Greece

    International Nuclear Information System (INIS)

    Patlitzianas, Konstantinos D.; Skylogiannis, Georgios K.; Papastefanakis, Dimitrios

    2013-01-01

    Highlights: • An approach of qualitative judgments for the PV opportunities through the assessing of the licenses’ value in Greece. • It can be supplied in other countries by applying different weights to the criteria. • It can be used by everyone in order to find a suitable PV investment without the need of experts in the field. - Abstract: Greece, as a member of the European Union (EU), has undertaken the obligation to meet the expected goals for the penetration of Renewable Energy Sources (RES) in the national energy balance in compliance with “20–20–20” goals (20% of the Gross Energy Consumption and 40% of the Gross Electricity Consumption should be covered by RES). Although the development of RES, and particularly of Photovoltaic (PV), in Greece during the last years has presented a satisfactory growth, the country is still far away from the above goals. The main reason for this delay is that – except the financial crisis – many licenses are inactive and waiting funding in order to be utilized. Additionally, the latest law (L.4152/2013) has forbidden the interconnection of new PV power Plants to the grid until the end of 2013. The above fact determines the significance of the existing PV Licenses in achieving the national goals. The aim of this paper is to present an integrated approach of qualitative judgments for the PV business opportunities through the assessing of the licenses’ value in Greece. The approach, which is based on a Multi Criteria Decision Making (MCDM) theory of quantifying multiple qualitative judgments, takes into account the real factors which can affect the expected production and cost of the PV installation and therefore the RoI (Return of Investment)

  19. Agriculture and Regional Development in Greece

    OpenAIRE

    Kyrkilis, Dimitrios; Semasis, Simeon

    2012-01-01

    This paper attempts to explore the effects of post-war war economic development model followed in Greece. The model is characterized by both the neglect of Greek agriculture and the emphasis on industrialization, mainly around the two major cities, Athens and Thessaloniki. The model has to develop a strong industrial sector but to inflate services and it devastated agriculture. At the regional level the uneven growth path that has been adopted perpetuated between urban and tourist areas on th...

  20. Country policy profile - Greece. December 2015

    International Nuclear Information System (INIS)

    2015-12-01

    In Greece, electricity from renewable sources is promoted through a feed-in tariff, subsidies a tax exemption and a net metering scheme. Renewable energy sources for heating purposes profit from a tax exemption and a subsidy scheme. The main incentive for renewable energy use in transport is a quota system (RES-Legal Europe, 2014). The Greek progress report was released by the EC in March 2014

  1. The new Hamburg Ocean-Bottom-Tiltmeter (OBT): A first deployment at Columbo Seamount (Aegean Sea, Greece)

    Science.gov (United States)

    Huebscher, C.; Hensch, M.; Hort, M.; Dahm, T.; Klawonn, M.; Winter, S.

    2008-12-01

    Assessing the state of volcanic activity of seamounts is quite more complicated than for onshore volcanoes, due to the difficulty of deploying instruments. At land, various techniques are applied (seismic networks, deformation studies, gas measurements etc.). At sea, mainly seismological observations are used. However, especially onshore deformation studies using INSAR have proven to be valuable in determining recharge of magmatic systems. We therefore developed a free fall, self leveling Ocean Bottom Tiltmeter (OBT) to observe deformation on the seafloor, using a two component high resolution tilt sensor with a resolution of about 1nrad (0.15μ°) and a maximum signal of about 0.045rad (0.5°). It is mounted inside a 17~inch glass sphere on a levelling stage, which relevels the instrument between ± 5° down to an accuracy of 0.006°. During the measurement this leveling stage is standing on the bottom of the glass sphere. For releveling, the instrument is pulled up by thin nylon strings and then locked to a gimbal system in order to compensate for tilt. This releveling procedure is done once every 48 hours. Data is recorded on an 18bit data logger at 50Hz sampling rate. Additionally to tilt and seismic signals (using a hydrophone), temperature, absolute pressure to measure uplift or subsidence, and orientation (electronic compass) are monitored. 4 OBT systems were deployed between June 2006 - March 2007 at Columbo seamount, a submarine volcano north-east of Santorini island, Aegean Sea, Greece, on a 3 km long profile perpendicular to the first principal stress axis σ_1 of the regional stressfield. Three of the instruments operated the whole time, one shut down due to a short circuit. First data processing indicates that small regional earthquakes as well as major tectonic earthquakes are properly recorded by the system. We find small, but permanent short- period deformations associated with local earthquakes and also observe long-period deformation processes

  2. Medical Informatics Education & Research in Greece.

    Science.gov (United States)

    Chouvarda, I; Maglaveras, N

    2015-08-13

    This paper aims to present an overview of the medical informatics landscape in Greece, to describe the Greek ehealth background and to highlight the main education and research axes in medical informatics, along with activities, achievements and pitfalls. With respect to research and education, formal and informal sources were investigated and information was collected and presented in a qualitative manner, including also quantitative indicators when possible. Greece has adopted and applied medical informatics education in various ways, including undergraduate courses in health sciences schools as well as multidisciplinary postgraduate courses. There is a continuous research effort, and large participation in EU-wide initiatives, in all the spectrum of medical informatics research, with notable scientific contributions, although technology maturation is not without barriers. Wide-scale deployment of eHealth is anticipated in the healthcare system in the near future. While ePrescription deployment has been an important step, ICT for integrated care and telehealth have a lot of room for further deployment. Greece is a valuable contributor in the European medical informatics arena, and has the potential to offer more as long as the barriers of research and innovation fragmentation are addressed and alleviated.

  3. Electrifying Greece with solar and wind energy

    Directory of Open Access Journals (Sweden)

    Mentis Dimitris

    2014-01-01

    Full Text Available Ensuring energy security, reducing GHG emissions and boosting the competitiveness of a country’s economy by attracting investments and technical knowhow are of paramount importance considering the targets of “20-20-20” set by the European community. Being the cradle of civilization, Greece appears today as a country caught in a prolonged hard economic and social crisis, the way out of which its citizens are looking forward as well as the entire European Union. Establishment of the leading renewable energy sources like solar and wind in Greece will not only increase the independence of its own electrification but will also provide with a foundation for developing the market of international trade of “green” energy. This paper initially highlights the current status of photovoltaics and wind turbines in Greece. Furthermore, this study evaluates whether a higher penetration of the above mentioned green energy sources would have positive impact in the economy of the country or not and in what extent they could decline the CO2 emissions until 2020, comparing to the corresponding levels in 2010.

  4. Problems experienced by haemodialysis patients in Greece.

    Science.gov (United States)

    Kaba, E; Bellou, P; Iordanou, P; Andrea, S; Kyritsi, E; Gerogianni, G; Zetta, S; Swigart, V

    Even though Greece has a disproportionate number of haemodialysis stations for the treatment of end-stage renal disease (ESRD), and a rapidly rising number of patients on dialysis, there has been no study of the lived experience of haemodialysis treatment in Greece. ESRD and dialysis drastically impact patients' everyday life, therefore expectations and desires play a major role in adapting to alterations and restrictions. An understanding of these culturally-influenced expectations and desires is essential for the delivery of holistic nursing care. This study aimed to explore how Greek patients receiving long-term haemodialysis perceived their problems and to describe the impact of haemodialysis on their lives. Using a grounded theory approach, 23 patients with ESRD receiving haemodialysis were purposively recruited from two hospital dialysis centres in Athens, Greece. Data were collected during 2006 by personal interviews. Given a distinctive patient experience of haemodialysis, some insight into their common concerns can facilitate provision of healthcare services that adequately meets their needs. By developing an understanding of the experience of renal illness and therapy for a group of people using dialysis, this study was intended as a contribution towards enabling healthcare professionals to provide more effective support to people who are living with this chronic condition.

  5. Re-appraisal of the Magma-rich versus Magma-poor Paradigm at Rifted Margins: consequences for breakup processes

    Science.gov (United States)

    Tugend, J.; Gillard, M.; Manatschal, G.; Nirrengarten, M.; Harkin, C. J.; Epin, M. E.; Sauter, D.; Autin, J.; Kusznir, N. J.; McDermott, K.

    2017-12-01

    Rifted margins are often classified based on their magmatic budget only. Magma-rich margins are commonly considered to have excess decompression melting at lithospheric breakup compared with steady state seafloor spreading while magma-poor margins have suppressed melting. New observations derived from high quality geophysical data sets and drill-hole data have revealed the diversity of rifted margin architecture and variable distribution of magmatism. Recent studies suggest, however, that rifted margins have more complex and polyphase tectono-magmatic evolutions than previously assumed and cannot be characterized based on the observed volume of magma alone. We compare the magmatic budget related to lithospheric breakup along two high-resolution long-offset deep reflection seismic profiles across the SE-Indian (magma-poor) and Uruguayan (magma-rich) rifted margins. Resolving the volume of magmatic additions is difficult. Interpretations are non-unique and several of them appear plausible for each case involving variable magmatic volumes and mechanisms to achieve lithospheric breakup. A supposedly 'magma-poor' rifted margin (SE-India) may show a 'magma-rich' lithospheric breakup whereas a 'magma-rich' rifted margin (Uruguay) does not necessarily show excess magmatism at lithospheric breakup compared with steady-state seafloor spreading. This questions the paradigm that rifted margins can be subdivided in either magma-poor or magma-rich margins. The Uruguayan and other magma-rich rifted margins appear characterized by an early onset of decompression melting relative to crustal breakup. For the converse, where the onset of decompression melting is late compared with the timing of crustal breakup, mantle exhumation can occur (e.g. SE-India). Our work highlights the difficulty in determining a magmatic budget at rifted margins based on seismic reflection data alone, showing the limitations of margin classification based solely on magmatic volumes. The timing of

  6. Ship emissions and their externalities for Greece

    Science.gov (United States)

    Tzannatos, Ernestos

    2010-06-01

    The existing and emerging international and European policy framework for the reduction of ship exhaust emissions dictates the need to produce reliable national, regional and global inventories in order to monitor emission trends and consequently provide the necessary support for future policy making. Furthermore, the inventories of ship exhaust emissions constitute the basis upon which their external costs are estimated in an attempt to highlight the economic burden they impose upon the society and facilitate the cost-benefit analysis of the proposed emission abatement technologies, operational measures and market-based instruments prior to their implementation. The case of Greece is of particular interest mainly because the dense ship traffic within the Greek seas directly imposes the impact of its exhaust emission pollutants (NO x, SO 2 and PM) upon the highly populated, physically sensitive and culturally precious Greek coastline, as well as upon the land and seas of Greece in general, whereas the contribution of Greece in the global CO 2 inventory at a time of climatic change awareness cannot be ignored. In this context, this paper presents the contribution of Greece in ship exhaust emissions of CO 2, NO x, SO 2 and PM from domestic and international shipping over the last 25 years (1984-2008), utilizing the fuel-based (fuel sales) emission methodology. Furthermore, the ship exhaust emissions generated within the Greek seas and their externalities are estimated for the year 2008, through utilizing the fuel-based (fuel sales) approach for domestic shipping and the activity-based (ship traffic) approach for international shipping. On this basis, it was found that during the 1984 to 2008 period the fuel-based (fuel sales) ship emission inventory for Greece increased at an average annual rate of 2.85%. In 2008, the CO 2, NO x, SO 2 and PM emissions reached 12.9 million tons (of which 12.4 million tons of CO 2) and their externalities were found to be around 3

  7. The Magma Chamber Simulator: Modeling the Impact of Wall Rock Composition on Mafic Magmas during Assimilation-Fractional Crystallization

    Science.gov (United States)

    Creamer, J. B.; Spera, F. J.; Bohrson, W. A.; Ghiorso, M. S.

    2012-12-01

    Although stoichiometric titration is often used to model the process of concurrent Assimilation and Fractional Crystallization (AFC) within a compositionally evolving magma body, a more complete treatment of the problem involves simultaneous and self-consistent determination of stable phase relationships and separately evolving temperatures of both Magma (M) and Wall Rock (WR) that interact as a composite M-WR system. Here we present results of M-WR systems undergoing AFC forward modeled with the Magma Chamber Simulator (MCS), which uses the phase modeling capabilities of MELTS (Ghiorso & Sack 1995) as the thermodynamic basis. Simulations begin with one of a variety of mafic magmas (e.g. HAB, MORB, AOB) intruding a set mass of Wall Rock (e.g. lherzolite, gabbro, diorite, granite, metapelite), and heat is exchanged as the M-WR system proceeds towards thermal equilibrium. Depending on initial conditions, the early part of the evolution can involve closed system FC while the WR heats up. The WR behaves as a closed system until it is heated beyond the solidus to critical limit for melt fraction extraction (fc), ranging between 0.08 and 0.12 depending on WR characteristics including composition and, rheology and stress field. Once fc is exceeded, a portion of the anatectic liquid is assimilated into the Magma. The MCS simultaneously calculates mass and composition of the mineral assemblage (Magma cumulates and WR residue) and melt (anatectic and Magma) at each T along the equilibration trajectory. Sensible and latent heat lost or gained plus mass gained by the Magma are accounted for by the MCS via governing Energy Constrained- Recharge Assimilation Fractional Crystallization (EC-RAFC) equations. In a comparison of two representative MCS results, consider a granitic WR intruded by HAB melt (51 wt. % SiO2) at liquidus T in shallow crust (0.1 GPa) with a WR/M ratio of 1.25, fc of 0.1 and a QFM oxygen buffer. In the first example, the WR begins at a temperature of 100o

  8. Petrology of the 1995/2000 Magma of Copahue, Argentina

    Science.gov (United States)

    Goss, A.; Varekamp, J. C.

    2001-05-01

    Phreatomagmatic eruptions of Copahue in July/August,1995 and July/August 2000 produced mixed juvenile clasts, silica-rich debris from the hydrothermal system, and magmatic scoria with 88 percent SiO2. These high-SiO2 clasts carry an as yet unidentified (crystobalite?), euhedral silica phase in great abundance, which is riddled with tan, primary melt inclusions. The mixed clasts have bands of mafic material with small euhedral olivine, clinopyroxene, and plagioclase that are mixed with an intermediate magma with coarser, resorbed phenocrysts of olivine, plagioclase, clino- and ortho- pyroxene, and rare occurrences of the silica phase. These ejecta are intimate mixtures of a relatively felsic magma similar to Pleistocene Copahue lavas and a mafic basaltic andesite, with minor contributions of a magma contaminated with silica-rich hydrothermal wallrock material. Two-pyroxene geothermometry indicates crystallization temperatures of 1020 deg - 1045 deg C. Glass inclusions (59-63 percent SiO2) in plagioclase and olivine crystals yield very low volatile contents in the melt (0.4-1.5 percent H2O). The 1995/2000 magmas resided at shallow level and degassed into the active volcano-hydrothermal system which discharges acid fluids into the Copahue crater lake and hot springs. More mafic magma intruded this shallow batch and the mixture rose into the hydrothermal system and assimilated siliceous wall rock. A Ti-diffusion profile in a magnetite crystal suggests that the period between magma mixing and eruption was on the order of 4-10 weeks, and the temperature difference between resident and intruding magma was about 50-60 oC.

  9. Conducting Qualitative Research on Desertification in Western Lesvos, Greece

    Science.gov (United States)

    Iosifides, Theodoros; Politidis, Theodoros

    2005-01-01

    The main aim of this article is to present some critical methodological strategies employed in a qualitative research study on local socioeconomic development and desertification in western Lesvos, Greece. Through in-depth qualitative interviews with local producers in western Lesvos, Greece, an effort was made to identify and analyze the links…

  10. Chernobyl radioactivity in grain produced in Greece in 1986

    International Nuclear Information System (INIS)

    Dominici, G.; Malvicini, A.; Panetsos, F.

    1988-01-01

    The Chernobyl radioactive cloud reached Greece in the first days of May 1986. During this period, the gain was in maximum growth; therefore, in absorbing the radionuclides it has become an excellent indicator of the deposited radioactivity. Measurements carried out in grain samples which were obtained from Greece are reported and some conclusions regarding population doses are presented

  11. Academic Libraries in Greece: The Present Situation and Future Prospects.

    Science.gov (United States)

    Keller, Dean H., Ed.

    The purpose of this collection of essays is to examine academic libraries in Greece at a time when the potential for changes and advance in librarianship is great. The 15 papers are as follows: "International Interlibrary Cooperation: Exchanging Goals, Values and Culture" (Don L. Tolliver); "Academic Libraries in Greece" (James…

  12. Genotyping Plasmodium vivax isolates from the 2011 outbreak in Greece

    DEFF Research Database (Denmark)

    Spanakos, Gregory; Alifrangis, Michael; Schousboe, Mette L

    2013-01-01

    Plasmodium vivax malaria was common in Greece until the 1950s with epidemics involving thousands of cases every year. Greece was declared free of malaria by the World Health Organization in 1974. From 1974 to 2010, an average of 39 cases per year were reported, which were mainly imported. However...... during 2011 is described, to elucidate the possible origin and spread of the disease....

  13. Greek Immigrants and Greece: An Introduction to the Multi-Media Package on Greece.

    Science.gov (United States)

    Mowat, Susanne; Witzel, Anne

    This is another of several multi-media packages on ethnic groups in Toronto that attempt to introduce Toronto teachers (especially those who teach English as a second language) to the cultures and societies from which their students came. An introduction to the multi-media package on Greece is given here. Sections included in the document are:…

  14. Carbon dioxide in magmas and implications for hydrothermal systems

    Science.gov (United States)

    Lowenstern, J. B.

    2001-01-01

    This review focuses on the solubility, origin, abundance, and degassing of carbon dioxide (CO2) in magma-hydrothermal systems, with applications for those workers interested in intrusion-related deposits of gold and other metals. The solubility of CO2 increases with pressure and magma alkalinity. Its solubility is low relative to that of H2O, so that fluids exsolved deep in the crust tend to have high CO2/H2O compared with fluids evolved closer to the surface. Similarly, CO2/H2O will typically decrease during progressive decompression- or crystallization-induced degassing. The temperature dependence of solubility is a function of the speciation of CO2, which dissolves in molecular form in rhyolites (retrograde temperature solubility), but exists as dissolved carbonate groups in basalts (prograde). Magnesite and dolomite are stable under a relatively wide range of mantle conditions, but melt just above the solidus, thereby contributing CO2 to mantle magmas. Graphite, diamond, and a free CO2-bearing fluid may be the primary carbon-bearing phases in other mantle source regions. Growing evidence suggests that most CO2 is contributed to arc magmas via recycling of subducted oceanic crust and its overlying sediment blanket. Additional carbon can be added to magmas during magma-wallrock interactions in the crust. Studies of fluid and melt inclusions from intrusive and extrusive igneous rocks yield ample evidence that many magmas are vapor saturated as deep as the mid crust (10-15 km) and that CO2 is an appreciable part of the exsolved vapor. Such is the case in both basaltic and some silicic magmas. Under most conditions, the presence of a CO2-bearing vapor does not hinder, and in fact may promote, the ascent and eruption of the host magma. Carbonic fluids are poorly miscible with aqueous fluids, particularly at high temperature and low pressure, so that the presence of CO2 can induce immiscibility both within the magmatic volatile phase and in hydrothermal systems

  15. Magma Transport from Deep to Shallow Crust and Eruption

    Science.gov (United States)

    White, R. S.; Greenfield, T. S.; Green, R. G.; Brandsdottir, B.; Hudson, T.; Woods, J.; Donaldson, C.; Ágústsdóttir, T.

    2016-12-01

    We have mapped magma transport paths from the deep (20 km) to the shallow (6 km) crust and in two cases to eventual surface eruption under several Icelandic volcanoes (Askja, Bardarbunga, Eyjafjallajokull, Upptyppingar). We use microearthquakes caused by brittle fracture to map magma on the move and tomographic seismic studies of velocity perturbations beneath volcanoes to map the magma storage regions. High-frequency brittle failure earthquakes with magnitudes of typically 0-2 occur where melt is forcing its way through the country rock, or where previously frozen melt is repeatedly re-broken in conduits and dykes. The Icelandic crust on the rift zones where these earthquakes occur is ductile at depths greater than 7 km beneath the surface, so the occurrence of brittle failure seismicity at depths as great as 20 km is indicative of high strain rates, for which magma movement is the most likely explanation. We suggest that high volatile pressures caused by the exsolution of carbon dioxide in the deep crust is driving the magma movement and seismicity at depths of 15-20 km. Eruptions from shallow crustal storage areas are likewise driven by volatile exsolution, though additional volatiles, and in particular water are also involved in the shallow crust.

  16. Renewable Energy Policy Fact sheet - Greece

    International Nuclear Information System (INIS)

    2017-07-01

    The EurObserv'ER policy profiles give a snapshot of the renewable energy policy in the EU Member States. In Greece, electricity from renewable sources is promoted through feed-in premiums, granted through tenders (as from 2017), feed-in tariffs for limited cases, a preferential tax regime (since 2016) and a net metering scheme. Heating and cooling from renewable energy sources is incentivised by way of a preferential tax regime and an investment subsidy scheme. The main instrument for renewable energy use in transport is a bio-fuels quota scheme

  17. Magma storage in a strike-slip caldera.

    Science.gov (United States)

    Saxby, J; Gottsmann, J; Cashman, K; Gutiérrez, E

    2016-07-22

    Silicic calderas form during explosive volcanic eruptions when magma withdrawal triggers collapse along bounding faults. The nature of specific interactions between magmatism and tectonism in caldera-forming systems is, however, unclear. Regional stress patterns may control the location and geometry of magma reservoirs, which in turn may control the spatial and temporal development of faults. Here we provide new insight into strike-slip volcano-tectonic relations by analysing Bouguer gravity data from Ilopango caldera, El Salvador, which has a long history of catastrophic explosive eruptions. The observed low gravity beneath the caldera is aligned along the principal horizontal stress orientations of the El Salvador Fault Zone. Data inversion shows that the causative low-density structure extends to ca. 6 km depth, which we interpret as a shallow plumbing system comprising a fractured hydrothermal reservoir overlying a magmatic reservoir with vol% exsolved vapour. Fault-controlled localization of magma constrains potential vent locations for future eruptions.

  18. What can Fe stable isotopes tell us about magmas?

    DEFF Research Database (Denmark)

    Stausberg, Niklas

    the differentiation of magmas from the perspective of Fe stable isotopes, integrated with petrology, by studying igneous rocks and their constituent phases (minerals and glasses) from the Bushveld Complex, South Africa, Thingmuli, Iceland, Pantelleria, Italy, and the Bishop Tuff, USA. The findings are interpreted......The majority of the Earth’s crust is formed by magmas, and understanding their production and differentiation is important to interpret the geologic rock record. A powerful tool to investigate magmatic processes is the distribution of the stable isotopes of the major redox-sensitive element...... in magmas, Fe. Fe isotope compositions of magmatic rocks exhibit systematic differences, where the heaviest compositions are found in rhyolites and granites. Understanding of these systematics is complicated by a lack of constraints on Fe isotope fractionation among minerals and liquids under magmatic...

  19. The magma ocean as an impediment to lunar plate tectonics

    Science.gov (United States)

    Warren, Paul H.

    1993-01-01

    The primary impediment to plate tectonics on the moon was probably the great thickness of its crust and particularly its high crust/lithosphere thickness ratio. This in turn can be attributed to the preponderance of low-density feldspar over all other Al-compatible phases in the lunar interior. During the magma ocean epoch, the moon's crust/lithosphere thickness ratio was at the maximum theoretical value, approximately 1, and it remained high for a long time afterwards. A few large regions of thin crust were produced by basin-scale cratering approximately contemporaneous with the demise of the magma ocean. However, these regions probably also tend to have uncommonly thin lithosphere, since they were directly heated and indirectly enriched in K, Th, and U by the same cratering process. Thus, plate tectonics on the moon in the form of systematic lithosphere subduction was impeded by the magma ocean.

  20. Phenomena associated with magma expansion into a drift

    International Nuclear Information System (INIS)

    Gaffney, E.S.

    2002-01-01

    One of the significant threats to the proposed Yucca Mountain nuclear waste repository has been identified as the possibility of intersection of the underground structure by a basaltic intrusion. Based on the geology of the region, it is assumed that such an intrusion would consist of an alkali basalt similar to the nearby Lathrop Wells cone, which has been dated at about 78 ka. The threat of radioactive release may be either from eruption through the surface above the repository of basalt that had been contaminated or from migration through ground water of radionucleides released as a result of damage to waste packages that interact with the magma. As part of our study of these threats, we are analyzing the phenomena associated with magma expansion into drifts in tuff. The early phenomena of the encounter of volatile-rich basaltic magma with a drift are discussed here.

  1. Complexities in Shallow Magma Transport at Kilauea (Invited)

    Science.gov (United States)

    Swanson, D. A.

    2013-12-01

    The standard model of Kilauea's shallow plumbing system includes magma storage under the caldera and conduits in the southwest rift zone (SWRZ) and the east rift zone (ERZ). As a field geologist, I find that seemingly aberrant locations and trends of some eruptive vents indicate complexities in shallow magma transport not addressed by the standard model. This model is not wrong but instead incomplete, because it does not account for the development of offshoots from the main plumbing. These offshoots supply magma to the surface at places that tell us much about the complicated stress system within the volcano. Perhaps most readily grasped are fissures peripheral to the north and south sides of the caldera. Somehow magma can apparently be injected into caldera-bounding faults from the summit reservoir complex, but the process and pathways are unclear. Of more importance is the presence of fissures with ENE trends on the east side of the caldera, including Kilauea Iki. Is this a rift zone that forms an acute angle with the ERZ? I think there is another explanation: the main part of the ERZ has migrated ~5 km SSE during the past few tens of thousands of years owing to seaward movement of the south flank, but older parts of the rift zone can be reactivated. The fissures east of the caldera have the ERZ trend and may record such reactivation; this interpretation includes the location of the largest eruption (15th century) known from Kilauea. Whether or not this interpretation has validity, the question remains: what changes in the plumbing system allow magma to erupt east of the caldera? The SWRZ can be divided into two sections, the SWRZ proper and the seismically active part (SASWRZ) southeast of the SWRZ. The total width of both sections is ~4 km. The SWRZ might be migrating SSE, as is the ERZ. Fissures in the SWRZ proper trend SW. Fissures in the SASWRZ, however, have ENE trends like that of the ERZ, although, because of en echelon offsets, the fissure zone itself

  2. Iron Redox Systematics of Shergottites and Martian Magmas

    Science.gov (United States)

    Righter, Kevin; Danielson, L. R.; Martin, A. M.; Newville, M.; Choi, Y.

    2010-01-01

    Martian meteorites record a range of oxygen fugacities from near the IW buffer to above FMQ buffer [1]. In terrestrial magmas, Fe(3+)/ SigmaFe for this fO2 range are between 0 and 0.25 [2]. Such variation will affect the stability of oxides, pyroxenes, and how the melt equilibrates with volatile species. An understanding of the variation of Fe(3+)/SigmaFe for martian magmas is lacking, and previous work has been on FeO-poor and Al2O3-rich terrestrial basalts. We have initiated a study of the iron redox systematics of martian magmas to better understand FeO and Fe2O3 stability, the stability of magnetite, and the low Ca/high Ca pyroxene [3] ratios observed at the surface.

  3. Lunar Magma Ocean Crystallization: Constraints from Fractional Crystallization Experiments

    Science.gov (United States)

    Rapp, J. F.; Draper, D. S.

    2015-01-01

    The currently accepted paradigm of lunar formation is that of accretion from the ejecta of a giant impact, followed by crystallization of a global scale magma ocean. This model accounts for the formation of the anorthosite highlands crust, which is globally distributed and old, and the formation of the younger mare basalts which are derived from a source region that has experienced plagioclase extraction. Several attempts at modelling the crystallization of such a lunar magma ocean (LMO) have been made, but our ever-increasing knowledge of the lunar samples and surface have raised as many questions as these models have answered. Geodynamic models of lunar accretion suggest that shortly following accretion the bulk of the lunar mass was hot, likely at least above the solidus]. Models of LMO crystallization that assume a deep magma ocean are therefore geodynamically favorable, but they have been difficult to reconcile with a thick plagioclase-rich crust. A refractory element enriched bulk composition, a shallow magma ocean, or a combination of the two have been suggested as a way to produce enough plagioclase to account for the assumed thickness of the crust. Recently however, geophysical data from the GRAIL mission have indicated that the lunar anorthositic crust is not as thick as was initially estimated, which allows for both a deeper magma ocean and a bulk composition more similar to the terrestrial upper mantle. We report on experimental simulations of the fractional crystallization of a deep (approximately 100km) LMO with a terrestrial upper mantle-like (LPUM) bulk composition. Our experimental results will help to define the composition of the lunar crust and mantle cumulates, and allow us to consider important questions such as source regions of the mare basalts and Mg-suite, the role of mantle overturn after magma ocean crystallization and the nature of KREEP

  4. Molybdenite saturation in silicic magmas: Occurrence and petrological implications

    Science.gov (United States)

    Audetat, A.; Dolejs, D.; Lowenstern, J. B.

    2011-01-01

    We identified molybdenite (MoS2) as an accessory magmatic phase in 13 out of 27 felsic magma systems examined worldwide. The molybdenite occurs as small (molybdenite-saturated samples reveal 1-13 ppm Mo in the melt and geochemical signatures that imply a strong link to continental rift basalt-rhyolite associations. In contrast, arc-associated rhyolites are rarely molybdenite-saturated, despite similar Mo concentrations. This systematic dependence on tectonic setting seems to reflect the higher oxidation state of arc magmas compared with within-plate magmas. A thermodynamic model devised to investigate the effects of T, f O2 and f S2 on molybdenite solubility reliably predicts measured Mo concentrations in molybdenite-saturated samples if the magmas are assumed to have been saturated also in pyrrhotite. Whereas pyrrhotite microphenocrysts have been observed in some of these samples, they have not been observed from other molybdenite-bearing magmas. Based on the strong influence of f S2 on molybdenite solubility we calculate that also these latter magmas must have been at (or very close to) pyrrhotite saturation. In this case the Mo concentration of molybdenite-saturated melts can be used to constrain both magmatic f O2 and f S2 if temperature is known independently (e.g. by zircon saturation thermometry). Our model thus permits evaluation of magmatic f S2, which is an important variable but is difficult to estimate otherwise, particularly in slowly cooled rocks. ?? The Author 2011. Published by Oxford University Press. All rights reserved.

  5. Failed magmatic eruptions: Late-stage cessation of magma ascent

    Science.gov (United States)

    Moran, S.C.; Newhall, C.; Roman, D.C.

    2011-01-01

    When a volcano becomes restless, a primary question is whether the unrest will lead to an eruption. Here we recognize four possible outcomes of a magmatic intrusion: "deep intrusion", "shallow intrusion", "sluggish/viscous magmatic eruption", and "rapid, often explosive magmatic eruption". We define "failed eruptions" as instances in which magma reaches but does not pass the "shallow intrusion" stage, i. e., when magma gets close to, but does not reach, the surface. Competing factors act to promote or hinder the eventual eruption of a magma intrusion. Fresh intrusion from depth, high magma gas content, rapid ascent rates that leave little time for enroute degassing, opening of pathways, and sudden decompression near the surface all act to promote eruption, whereas decreased magma supply from depth, slow ascent, significant enroute degassing and associated increases in viscosity, and impingement on structural barriers all act to hinder eruption. All of these factors interact in complex ways with variable results, but often cause magma to stall at some depth before reaching the surface. Although certain precursory phenomena, such as rapidly escalating seismic swarms or rates of degassing or deformation, are good indicators that an eruption is likely, such phenomena have also been observed in association with intrusions that have ultimately failed to erupt. A perpetual difficulty with quantifying the probability of eruption is a lack of data, particularly on instances of failed eruptions. This difficulty is being addressed in part through the WOVOdat database. Papers in this volume will be an additional resource for scientists grappling with the issue of whether or not an episode of unrest will lead to a magmatic eruption.

  6. Orientation of the eruption fissures controlled by a shallow magma chamber in Miyakejima

    Directory of Open Access Journals (Sweden)

    Nobuo Geshi

    2016-11-01

    Full Text Available Orientation of the eruption fissures and composition of the lavas of the Miyakejima volcano indicate tectonic influence of a shallow magma chamber on the distribution of eruption fissures. We examined the distributions and magmatic compositions of 23 fissures that formed within the last 2800 years, based on a field survey and a new dataset of 14C ages. The dominant orientation of the eruption fissures in the central portion of the volcano was found to be NE-SW, which is perpendicular to the direction of regional maximum horizontal compressive stress (σHmax. Magmas that show evidences of magma mixing between basaltic and andesitic magmas erupted mainly from the eruption fissures with a higher offset angle from the regional σHmax direction. The presence of a shallow dike-shaped magma chamber controls the distribution of the eruption fissures. The injection of basaltic magma into the shallow andesitic magma chamber caused the temporal rise of internal magmatic pressure in the shallow magma chamber. Dikes extending from the andesitic magma chamber intrude along the local compressive stress field which is generated by the internal excess pressure of the andesitic magma chamber. As the result, the eruption fissures trend parallel to the elongation direction of the shallow magma chamber. Injection of basaltic magma into the shallow andesitic magma chamber caused the magma mixing. Some basaltic dikes from the deep-seated magma chamber reach the ground surface without intersection with the andesitic magma chamber. The patterns of the eruption fissures can be modified in the future as was observed in the case of the destruction of the shallow magma chamber during the 2000 AD eruption.

  7. Isotopic evidence for multiple contributions to felsic magma chambers

    DEFF Research Database (Denmark)

    Waight, Tod Earle; Wiebe, R.A.; Krogstad, E.J.

    2007-01-01

    The Gouldsboro Granite forms part of the Coastal Maine Magmatic Province, a region characterized by granitic plutons that are intimately linked temporally and petrogenetically with abundant co-existing mafic magmas. The pluton is complex and preserves a felsic magma chamber underlain...... with identical isotopic compositions to more mafic dikes suggest that closed system fractionation may be occurring in deeper level chambers prior to injection to shallower levels. The granitic portion of the pluton has the highest Nd isotopic composition (eNd=+3.0) of plutons in the region whereas the mafic...

  8. Silicic magma differentiation in ascent conduits. Experimental constraints

    Science.gov (United States)

    Rodríguez, Carmen; Castro, Antonio

    2017-02-01

    Crystallization of water-bearing silicic magmas in a dynamic thermal boundary layer is reproduced experimentally by using the intrinsic thermal gradient of piston-cylinder assemblies. The standard AGV2 andesite under water-undersaturated conditions is set to crystallize in a dynamic thermal gradient of about 35 °C/mm in 10 mm length capsules. In the hotter area of the capsule, the temperature is initially set at 1200 °C and decreases by programmed cooling at two distinct rates of 0.6 and 9.6 °C/h. Experiments are conducted in horizontally arranged assemblies in a piston cylinder apparatus to avoid any effect of gravity settling and compaction of crystals in long duration runs. The results are conclusive about the effect of water-rich fluids that are expelled out the crystal-rich zone (mush), where water saturation is reached by second boiling in the interstitial liquid. Expelled fluids migrate to the magma ahead of the solidification front contributing to a progressive enrichment in the fluxed components SiO2, K2O and H2O. The composition of water-rich fluids is modelled by mass balance using the chemical composition of glasses (quenched melt). The results are the basis for a model of granite magma differentiation in thermally-zoned conduits with application of in-situ crystallization equations. The intriguing textural and compositional features of the typical autoliths, accompanying granodiorite-tonalite batholiths, can be explained following the results of this study, by critical phenomena leading to splitting of an initially homogeneous magma into two magma systems with sharp boundaries. Magma splitting in thermal boundary layers, formed at the margins of ascent conduits, may operate for several km distances during magma transport from deep sources at the lower crust or upper mantle. Accordingly, conduits may work as chromatographic columns contributing to increase the silica content of ascending magmas and, at the same time, leave behind residual mushes that

  9. Eutectic propeties of primitive Earth's magma ocean

    Science.gov (United States)

    Lo Nigro, G.; Andrault, D.; Bolfan-Casanova, N.; Perillat, J.-P.

    2009-04-01

    It is widely accepted that the early Earth was partially molten (if not completely) due to the high energy dissipated by terrestrial accretion [1]. After core formation, subsequent cooling of the magma ocean has led to fractional crystallization of the primitive mantle. The residual liquid corresponds to what is now called the fertile mantle or pyrolite. Melting relations of silicates have been extensively investigated using the multi-anvil press, for pressures between 3 and 25 GPa [2,3]. Using the quench technique, it has been shown that the pressure affects significantly the solidus and liquidus curves, and most probably the composition of the eutectic liquid. At higher pressures, up to 65 GPa, melting studies were performed on pyrolite starting material using the laser-heated diamond anvil cell (LH-DAC) technique [4]. However, the quench technique is not ideal to define melting criteria, and furthermore these studies were limited in pressure range of investigation. Finally, the use of pyrolite may not be relevant to study the melting eutectic temperature. At the core-mantle boundary conditions, melting temperature is documented by a single data point on (Mg,Fe)2SiO4 olivine, provided by shock wave experiments at around 130-140 GPa [5]. These previous results present large uncertainties of ~1000 K. The aim of this study is to determine the eutectic melting temperature in the chemically simplified system composed of the two major lower mantle phases, the MgSiO3 perovskite and MgO periclase. We investigated melting in-situ using the laser-heated diamond anvil cell coupled with angle dispersive X-ray diffraction at the ID27 beamline of the ESRF [6]. Melting relations were investigated in an extended P-T range comparable to those found in the Earth's lower mantle, i.e. from 25 to 120 GPa and up to more than 5000 K. Melting was evidenced from (a) disappearance of one of the two phases in the diffraction pattern, (b) drastic changes of the diffraction image itself, and

  10. Imaging magma plumbing beneath Askja volcano, Iceland

    Science.gov (United States)

    Greenfield, Tim; White, Robert S.

    2015-04-01

    Volcanoes during repose periods are not commonly monitored by dense instrumentation networks and so activity during periods of unrest is difficult to put in context. We have operated a dense seismic network of 3-component, broadband instruments around Askja, a large central volcano in the Northern Volcanic Zone, Iceland, since 2006. Askja last erupted in 1961, with a relatively small basaltic lava flow. Since 1975 the central caldera has been subsiding and there has been no indication of volcanic activity. Despite this, Askja has been one of the more seismically active volcanoes in Iceland. The majority of these events are due to an extensive geothermal area within the caldera and tectonically induced earthquakes to the northeast which are not related to the magma plumbing system. More intriguing are the less numerous deeper earthquakes at 12-24km depth, situated in three distinct areas within the volcanic system. These earthquakes often show a frequency content which is lower than the shallower activity, but they still show strong P and S wave arrivals indicative of brittle failure, despite their location being well below the brittle-ductile boundary, which, in Askja is ~7km bsl. These earthquakes indicate the presence of melt moving or degassing at depth while the volcano is not inflating, as only high strain rates or increased pore fluid pressures would cause brittle fracture in what is normally an aseismic region in the ductile zone. The lower frequency content must be the result of a slower source time function as earthquakes which are both high frequency and low frequency come from the same cluster, thereby discounting a highly attenuating lower crust. To image the plumbing system beneath Askja, local and regional earthquakes have been used as sources to solve for the velocity structure beneath the volcano. Travel-time tables were created using a finite difference technique and the residuals were used to solve simultaneously for both the earthquake locations

  11. Anciet marble quarries in Lesvos island Greece

    Science.gov (United States)

    Mataragkas, M.; Mataragkas, D.

    2009-04-01

    ANCIENT MARBLE QUARRIES IN LESBOS ISLAND, GREECE Varti- Matarangas M.1 & Matarangas D. 1 Institute of Geological and Mining Exploration (IGME), Olympic Village, Entrance C, ACHARNAE 13677, GREECE myrsini@igme.gr , myrsini@otenet.g r A B S T R A C T Ten ancient marble quarries of Lesbos Island, most of them previously unknown, have been studied, in the frame of the research study on the ancient marble quarries in the Aegean Sea. In the present paper the geological, petrological and morphological features of the aforementioned quarries are examined. Concerning the six ancient quarries located in the areas of Tarti, Agia Paraskevi (Tsaf), Mageiras, Loutra, Latomi (Plomari) and Thermi, the authochthonous neopaleozoic unit constitutes their geological formation, while their hosting lithological formations are the included crystalline limestone lens like beds. In two ancient quarries in the areas Moria and Alyfanta, the geological formation is the authochthonous upper Triassic series and the hosting lithological formation the upper Triassic carbonate sequence, while in the areas of Akrasi-Abeliko and Karyni, the geological formation is the thrust Triassic unit and the lithological hosting formations are the included strongly deformed or not crystalline limestone lenticular beds. Furthermore, the petrographic features were also determined permitting the identification of the building stones that have been used.

  12. Motivating Public Sector Employees: Evidence from Greece

    Directory of Open Access Journals (Sweden)

    Koronios, K.

    2017-03-01

    Full Text Available Purpose: The object of this research is to investigate work motivating factors in the public sector in Greece, as well as to study demographic attributes, placing emphasis on age and gender as determinants of employee motives. Design/methodology/approach: To answer our research questions, a questionnaire was distributed at the beginning of 2015 to a public - sector organization in central Greece. A total of 318 anonymous survey responses were collected and analysed with SPSS. Findings: In the public organization under survey, the leading employee motives are an increase in salaries, opportunities for hierarchical advancement in the organization, as well as the development of personal skills. Moreover, motivational differences are noted among Baby Boomers, Generation X and Generation Y. Research limitations/implications: As the present study has been conducted on a single public organization, awareness should be raised as far as the generalizability of the results providing useful insights for further exploration. Originality/value: Limited research has been conducted in the Greek public sector comparing motives among generations.

  13. Thermally-assisted Magma Emplacement Explains Restless Calderas.

    Science.gov (United States)

    Amoruso, Antonella; Crescentini, Luca; D'Antonio, Massimo; Acocella, Valerio

    2017-08-11

    Many calderas show repeated unrest over centuries. Though probably induced by magma, this unique behaviour is not understood and its dynamics remains elusive. To better understand these restless calderas, we interpret deformation data and build thermal models of Campi Flegrei caldera, Italy. Campi Flegrei experienced at least 4 major unrest episodes in the last decades. Our results indicate that the inflation and deflation of magmatic sources at the same location explain most deformation, at least since the build-up of the last 1538 AD eruption. However, such a repeated magma emplacement requires a persistently hot crust. Our thermal models show that this repeated emplacement was assisted by the thermal anomaly created by magma that was intruded at shallow depth ~3 ka before the last eruption. This may explain the persistence of the magmatic sources promoting the restless behaviour of the Campi Flegrei caldera; moreover, it explains the crystallization, re-melting and mixing among compositionally distinct magmas recorded in young volcanic rocks. Our model of thermally-assisted unrest may have a wider applicability, possibly explaining also the dynamics of other restless calderas.

  14. Automatic Compound Annotation from Mass Spectrometry Data Using MAGMa.

    NARCIS (Netherlands)

    Ridder, L.O.; Hooft, van der J.J.J.; Verhoeven, S.

    2014-01-01

    The MAGMa software for automatic annotation of mass spectrometry based fragmentation data was applied to 16 MS/MS datasets of the CASMI 2013 contest. Eight solutions were submitted in category 1 (molecular formula assignments) and twelve in category 2 (molecular structure assignment). The MS/MS

  15. Crystallization of Magma. CEGS Programs Publication Number 14.

    Science.gov (United States)

    Berry, R. W.

    Crystallization of Magma is one of a series of single-topic problem modules intended for use in undergraduate geology and earth science courses. Through problems and observations based on two sets of experiments, this module leads to an understanding of how an igneous rock can form from molten material. Environmental factors responsible for…

  16. Loki Patera as the Surface of a Magma Sea

    Science.gov (United States)

    Matson, D. L.; Davies, A. G.; Veeder, G. J.; Rathbun, J. A.; Johnson, T. V.

    2004-01-01

    Inspired by the finding of Schubert et al that Io's figure is consistent with a hydrostatic shape, we explore the consequences of modeling Loki Patera as the surface of a large magma sea. This model is attractive because of its sheer simplicity and its usefulness in interpreting and predicting observations. Here, we report on that work.

  17. Shallow magma diversions during explosive diatreme-forming eruptions.

    Science.gov (United States)

    Le Corvec, Nicolas; Muirhead, James D; White, James D L

    2018-04-13

    The diversion of magma is an important mechanism that may lead to the relocation of a volcanic vent. Magma diversion is known to occur during explosive volcanic eruptions generating subterranean excavation and remobilization of country and volcanic rocks. However, feedbacks between explosive crater formation and intrusion processes have not been considered previously, despite their importance for understanding evolving hazards during volcanic eruptions. Here, we apply numerical modeling to test the impacts of excavation and subsequent infilling of diatreme structures on stress states and intrusion geometries during the formation of maar-diatreme complexes. Explosive excavation and infilling of diatremes affects local stress states which inhibits magma ascent and drives lateral diversion at various depths, which are expected to promote intra-diatreme explosions, host rock mixing, and vent migration. Our models demonstrate novel mechanisms explaining the generation of saucer-shaped sills, linked with magma diversion and enhanced intra-diatreme explosive fragmentation during maar-diatreme volcanism. Similar mechanisms will occur at other volcanic vents producing crater-forming eruptions.

  18. 75 FR 28778 - Magma Flood Retarding Structure (FRS) Supplemental Watershed Plan, Pinal County, AZ

    Science.gov (United States)

    2010-05-24

    ... DEPARTMENT OF AGRICULTURE Natural Resources Conservation Service Magma Flood Retarding Structure... statement is not being prepared for the Magma Flood Retarding Structure (FRS) Supplemental Watershed Plan... rehabilitate the Magma FRS to provide for continued flood protection for a portion of the Town of Florence and...

  19. Extensive, water-rich magma reservoir beneath southern Montserrat

    Science.gov (United States)

    Edmonds, M.; Kohn, S. C.; Hauri, E. H.; Humphreys, M. C. S.; Cassidy, M.

    2016-05-01

    South Soufrière Hills and Soufrière Hills volcanoes are 2 km apart at the southern end of the island of Montserrat, West Indies. Their magmas are distinct geochemically, despite these volcanoes having been active contemporaneously at 131-129 ka. We use the water content of pyroxenes and melt inclusion data to reconstruct the bulk water contents of magmas and their depth of storage prior to eruption. Pyroxenes contain up to 281 ppm H2O, with significant variability between crystals and from core to rim in individual crystals. The Al content of the enstatites from Soufrière Hills Volcano (SHV) is used to constrain melt-pyroxene partitioning for H2O. The SHV enstatite cores record melt water contents of 6-9 wt%. Pyroxene and melt inclusion water concentration pairs from South Soufriere Hills basalts independently constrain pyroxene-melt partitioning of water and produces a comparable range in melt water concentrations. Melt inclusions recorded in plagioclase and in pyroxene contain up to 6.3 wt% H2O. When combined with realistic melt CO2 contents, the depth of magma storage for both volcanoes ranges from 5 to 16 km. The data are consistent with a vertically protracted crystal mush in the upper crust beneath the southern part of Montserrat which contains heterogeneous bodies of eruptible magma. The high water contents of the magmas suggest that they contain a high proportion of exsolved fluids, which has implications for the rheology of the mush and timescales for mush reorganisation prior to eruption. A depletion in water in the outer 50-100 μm of a subset of pyroxenes from pumices from a Vulcanian explosion at Soufrière Hills in 2003 is consistent with diffusive loss of hydrogen during magma ascent over 5-13 h. These timescales are similar to the mean time periods between explosions in 1997 and in 2003, raising the possibility that the driving force for this repetitive explosive behaviour lies not in the shallow system, but in the deeper parts of a vertically

  20. Magma Reservoirs Feeding Giant Radiating Dike Swarms: Insights from Venus

    Science.gov (United States)

    Grosfils, E. B.; Ernst, R. E.

    2003-01-01

    Evidence of lateral dike propagation from shallow magma reservoirs is quite common on the terrestrial planets, and examination of the giant radiating dike swarm population on Venus continues to provide new insight into the way these complex magmatic systems form and evolve. For example, it is becoming clear that many swarms are an amalgamation of multiple discrete phases of dike intrusion. This is not surprising in and of itself, as on Earth there is clear evidence that formation of both magma reservoirs and individual giant radiating dikes often involves periodic magma injection. Similarly, giant radiating swarms on Earth can contain temporally discrete subswarms defined on the basis of geometry, crosscutting relationships, and geochemical or paleomagnetic signatures. The Venus data are important, however, because erosion, sedimentation, plate tectonic disruption, etc. on Earth have destroyed most giant radiating dike swarm's source regions, and thus we remain uncertain about the geometry and temporal evolution of the magma sources from which the dikes are fed. Are the reservoirs which feed the dikes large or small, and what are the implications for how the dikes themselves form? Does each subswarm originate from a single, periodically reactivated reservoir, or do subswarms emerge from multiple discrete geographic foci? If the latter, are these discrete foci located at the margins of a single large magma body, or do multiple smaller reservoirs define the character of the magmatic center as a whole? Similarly, does the locus of magmatic activity change with time, or are all the foci active simultaneously? Careful study of giant radiating dike swarms on Venus is yielding the data necessary to address these questions and constrain future modeling efforts. Here, using giant radiating dike swarms from the Nemesis Tessera (V14) and Carson (V43) quadrangles as examples, we illustrate some of the dike swarm focal region diversity observed on Venus and briefly explore some

  1. Seismic tremors and magma wagging during explosive volcanism.

    Science.gov (United States)

    Jellinek, A Mark; Bercovici, David

    2011-02-24

    Volcanic tremor is a ubiquitous feature of explosive eruptions. This oscillation persists for minutes to weeks and is characterized by a remarkably narrow band of frequencies from about 0.5 Hz to 7 Hz (refs 1-4). Before major eruptions, tremor can occur in concert with increased gas flux and related ground deformation. Volcanic tremor is thus of particular value for eruption forecasting. Most models for volcanic tremor rely on specific properties of the geometry, structure and constitution of volcanic conduits as well as the gas content of the erupting magma. Because neither the initial structure nor the evolution of the magma-conduit system will be the same from one volcano to the next, it is surprising that tremor characteristics are so consistent among different volcanoes. Indeed, this universality of tremor properties remains a major enigma. Here we employ the contemporary view that silicic magma rises in the conduit as a columnar plug surrounded by a highly vesicular annulus of sheared bubbles. We demonstrate that, for most geologically relevant conditions, the magma column will oscillate or 'wag' against the restoring 'gas-spring' force of the annulus at observed tremor frequencies. In contrast to previous models, the magma-wagging oscillation is relatively insensitive to the conduit structure and geometry, which explains the narrow band of tremor frequencies observed around the world. Moreover, the model predicts that as an eruption proceeds there will be an upward drift in both the maximum frequency and the total signal frequency bandwidth, the nature of which depends on the explosivity of the eruption, as is often observed.

  2. Mezcla de magmas en Vulcanello (Isla Vulcano, Italia

    Directory of Open Access Journals (Sweden)

    Aparicio, A.

    2008-06-01

    Full Text Available Volcanic activity in Vulcano starts about 350 ka ago and continues up to present day with the development of thre main episodes corresponding to the calderas of Piano and La Fossa, and Vulcanello. These cover a compositional range from rhyolitic to trachybasaltic rocks. This lithological diversity is produced by different petrogenetic processes such as fractional crystallization, assimilation coupled to fractional crystallization (AFC, mixing, etc.The eruption of Vulcanello area emitted trachyandesitic materials, including shoshonites and latites. A magma-mixing process is established between trachytes and shoshonites to origine latites. Trachytes and rhyolites are produced by fractional crystallization and by ACF processes (assimilation of sedimentary rocks from trachyandesitic magmas.La actividad volcánica de Isla Vulcano comienzó aproximadamente hace 350.000 años y continúa hasta la actualidad con el desarrollo de tres grandes episodios correspondientes a las caldera de Piano, caldera de Fossa y a Vulcanello, que han emitido piroclastos y coladas de composiciones muy variadas, desde riolitas a traquibasaltos. Esta variedad litológica ha sido relacionada con procesos petrogenéticos tan diversos como cristalización fraccionada, asimilación simultánea con cristalización (ACF, mezcla de magmas, etc.El episodio de Vulcanello emite rocas traquiandesíticas, con composiciones shoshoníticas y latíticas. Un proceso de mezcla de magmas es reconocido entre traquitas y shoshonitas para generar latitas. Traquitas y riolitas son producidas por procesos de cristalización fraccionada simple y por ACF con asimilación de rocas sedimentarias a partir de magmas traquiandesíticos.

  3. Twins in Ancient Greece: a synopsis.

    Science.gov (United States)

    Malamitsi-Puchner, Ariadne

    2016-01-01

    This brief outline associates twins with several aspects of life in Ancient Greece. In Greek mythology twins caused ambivalent reactions and were believed to have ambivalent feelings for each other. Very often, they were viewed as the representatives of the dualistic nature of the universe. Heteropaternal superfecundation, which dominates in ancient myths, explains on one hand, the god-like qualities and, on the other hand, the mortal nature of many twins. An assumption is presented that legends referring to twins might reflect the territorial expansions of Ancient Greeks in Northern Mediterranean, around the Black Sea, in Asia Minor, as well as North East Africa. In conclusion, in Greek antiquity, twins have been used as transitional figures between myth and reality.

  4. European Patient Summary Guideline: Focus on Greece.

    Science.gov (United States)

    Berler, Alexander; Tagaris, Anastassios; Chronaki, Catherine

    2016-01-01

    The European Patient Summary (PS) guideline specifies a minimal dataset of essential and important information for unplanned or emergency care initially defined in the epSOS project with aim to improve patients' safety and quality of Care. The eHealth Network of European Union (EU) Member State (MS) representatives established under Article 14 of the EU directive 2011/24 on patient rights to cross-border healthcare adopted PS guideline in November 2013 and since then the guideline has been part of MS strategic eHealth implementation plans, standardization efforts, and concrete regional, national, European and international projects. This paper reviews implementation efforts for the implementation of an operational patient summary service in Greece drawing on challenges and lessons learned for sustainable standards-based large scale eHealth deployment in Europe and abroad, as well as the reuse of best practices from international standards and integration profiles.

  5. Country policy profile - Greece. August 2015

    International Nuclear Information System (INIS)

    2015-08-01

    In Greece, electricity from renewable sources is promoted through a feed-in tariff, subsidies a tax exemption and a net metering scheme. Renewable energy sources for heating purposes profit from a tax exemption and a subsidy scheme. The main incentive for renewable energy use in transport is a quota system (RES-Legal Europe, 2014). The Greek progress report was released by the EC in March 2014. This EurObserv'ER report reports on a new Greek law: 'Measures for the support and development of Greek economy within the scope of application of Law 4046/2012 and other provisions', published in the Government Gazette on 7 April 2014, introducing various new elements in the Greek RES policy

  6. ETHICAL CONSUMERS IN GREECE: WHO ARE THEY?

    Directory of Open Access Journals (Sweden)

    Antonia Delistavrou

    2017-09-01

    Full Text Available Presents a segmentation on the basis of the overall ethical consumption concept for the first time in Greece. Four segments were identified: Ethical Consumers (18.09%, Boycotters (20.48%, Ecological Consumers (27.86% and Conventional Consumers (33.57%. The Ethical Consumers’ segment consists of well educated citizens, who adopt all ethical behaviours more frequently. These consumers were found to be more confident they can control politics, less materialists, most attracted by post-materialist goals as well as less sceptical towards ethical products and less indifferent about ethical consumption issues. This segment may be considered as attractive enough to be targeted by business and non for profit organisations.

  7. Study of the pollution exchange between Bulgaria and Northern Greece

    International Nuclear Information System (INIS)

    Zerefos, C.; Vasaras, A.; Syrakov, D.; Ganev, K.

    2000-01-01

    The present work aims at a detailed study and explanation of the pollution transport in the air basin over South-Western Bulgaria and Northern Greece and assessment of the air pollution exchange between Bulgaria and Greece. Some well known specific climatic air pollution effects were studied and explained. Calculations were made of the S0 2 pollution of the Balkan peninsula from both Greek and Bulgarian sources for 1995 and the country to country pollution budget diagrams were build. Days with extreme mean concentration for Bulgaria and Northern Greece were picked out and some further specification of the contribution of the different sources in both the countries to these cases of extreme pollution was made. Some preliminary studies of possible mesoscale effects on the pollution exchange between Bulgaria and northern Greece were carried out. A three-layer pollution transport model with more complex chemistry block was introduced and some preliminary simulations of Sulfur and Nitrogen compounds transport were performed. (author)

  8. First confirmed record of Elodea canadensis Michx. (Hydrocharitaceae in Greece

    Directory of Open Access Journals (Sweden)

    Poulis Georgios

    2017-12-01

    Full Text Available The paper confirms the presence of Elodea canadensis Michx. in Greece and outlines the history of contradictory relevant reports. This is also the first report of the species′ presence in the transboundary lake Great Prespa.

  9. Characterization of Canine parvovirus 2 variants circulating in Greece.

    Science.gov (United States)

    Ntafis, Vasileios; Xylouri, Eftychia; Kalli, Iris; Desario, Costantina; Mari, Viviana; Decaro, Nicola; Buonavoglia, Canio

    2010-09-01

    The aim of the present study was to characterize Canine parvovirus 2 (CPV-2) variants currently circulating in Greece. Between March 2008 and March 2009, 167 fecal samples were collected from diarrheic dogs from different regions of Greece. Canine parvovirus 2 was detected by standard polymerase chain reaction, whereas minor groove binder probe assays were used to distinguish genetic variants and discriminate between vaccine and field strains. Of 84 CPV-2-positive samples, 81 CPV-2a, 1 CPV-2b, and 2 CPV-2c were detected. Vaccine strains were not detected in any sample. Sequence analysis of the VP2 gene of the 2 CPV-2c viruses revealed up to 100% amino acid identity with the CPV-2c strains previously detected in Europe. The results indicated that, unlike other European countries, CPV-2a remains the most common variant in Greece, and that the CPV-2c variant found in Europe is also present in Greece.

  10. Lead exposure of the child population in Greece.

    Science.gov (United States)

    Maravelias, C; Athanaselis, S; Poulos, L; Alevisopoulos, G; Ewers, U; Koutselinis, A

    1994-12-18

    Lead exposure of the child population was studied in three different areas in Greece: Kalamata which is a rural area of Southern Greece; Tavros, a district of Athens with a considerable industrial activity; and Lavrion, a small city near Athens where a lead-zinc mining and smelting industrial complex has existed for more than 90 years. The results were evaluated with respect to a number of individual, social and environmental variables (i.e. smelter, occupation of the father) especially those concerning the area of Lavrion which is the most heavily polluted area in Greece. The results of this study can be considered as an index for the extent of the lead pollution problem in the named areas of Greece.

  11. The triviality of abortion in Greece.

    Science.gov (United States)

    Naziri, D

    1991-09-01

    In Greece modern contraceptive methods are used only in a very limited manner and abortion is the primary form of birth control. There are several social and psychological issues that are considered to be responsible. A 1985 study done for the Family Planning Center of Thessaloniki found that the ratio of live births is 1.3 and the ratio of abortion is 1.8/woman. 88% of women in the study had had an abortion while practicing coitus interruptus. 90% of the women never bought condoms. In a 1989 study only 6% of women had a positive attitude about condoms. Abortion is used as the primary method of birth control regardless of a woman's socioeconomic status. Further it was found that abortion did not correlate with other modern attitudes or the emancipation of women. The decision to abort was related to difficulties and constraints inherent in bring up a child. However positive attitudes toward contraception were related to educational and occupational levels. To complicate matters the information concerning contraceptives was problematic and related to the women's own lack of initiative to find out, and a lack of correct information offered from gynecologists. A 1990 study on knowledge, attitudes, beliefs and practices in relation to HIV infection indicated that the most favored method of contraception was condoms, but 60.8% of the men reported use versus 33.7% of the women. However these figures are not very representative because the survey was given in the context of HIV prevention and no attempt was made to distinguish between regular and irregular use patterns. Abortions is not a moral issue in Greece. It was legalized in 1986 only because it came to the attention of the government that the previous prohibition was being completely ignored. Abortion is strongly affected by social and psychological factors that are complex and result from cultural view points about fertility, maternal value, and life itself that are unique to the Greek culture.

  12. The practice of electroconvulsive therapy in Greece.

    Science.gov (United States)

    Kaliora, Styliani C; Braga, Raphael J; Petrides, Georgios; Chatzimanolis, John; Papadimitriou, George N; Zervas, Iannis M

    2013-09-01

    To describe the practice of electroconvulsive therapy (ECT) in Greece. A survey was conducted during the academic year 2008-2009. Electroconvulsive therapy use was investigated for 2007. All civilian institutions providing inpatient care were included. Centers that provided ECT completed a 57-item questionnaire. Centers that did not offer ECT completed a 13-item questionnaire. Fifty-five (82.1%) of 67 institutions responded. Electroconvulsive therapy was offered in 18 hospitals. Only 2 of 10 university hospitals offered ECT. Overall, 137 patients were treated with 1271 sessions in 2007. Only 1.47% discontinued treatment owing to adverse events. There were no deaths. Schizophrenia was the most common diagnosis (41.3%) among those receiving ECT, followed by major depression (28.9%), bipolar depression (9.1%), catatonia (4.1%), suicidal ideation (3.3%), and schizoaffective disorder (2.5%). Physicians considered major depression (93.8%), catatonia (86.5%), schizophrenia (56.3%), and mania (50%) the most appropriate indications. Written informed consent was required in 77.8% of the institutions, whereas the rest required verbal consent. Bilateral ECT was the preferred electrode placement (88.9%). Modified ECT was used exclusively. Propofol was the preferred anesthetic (44.4%), followed by thiopental (38.9%). Seven (38.9%) of 18 hospitals used a fixed stimulus dose at first treatment. Five (27.8%) of 18 hospitals used the half-age method. Continuation/maintenance ECT was used in 33.3% of the hospitals. Outpatient ECT was seldom used. Lack of training, difficult access to anesthesiology, billing issues, and stigma were cited as the main impediments to the practice of ECT. Electroconvulsive therapy is practiced in moderate numbers in Greece and almost exclusively on an inpatient basis. Lack of training and lack of availability of anesthesiologists were cited as the most common obstacles to providing ECT.

  13. Ground surface deformation patterns, magma supply, and magma storage at Okmok volcano, Alaska, from InSAR analysis: 1. Intereruption deformation, 1997–2008

    Science.gov (United States)

    Lu, Zhong; Dzurisin, Daniel; Biggs, Juliet; Wicks, Charles; McNutt, Steve

    2010-01-01

    Starting soon after the 1997 eruption at Okmok volcano and continuing until the start of the 2008 eruption, magma accumulated in a storage zone centered ~3.5 km beneath the caldera floor at a rate that varied with time. A Mogi-type point pressure source or finite sphere with a radius of 1 km provides an adequate fit to the deformation field portrayed in time-sequential interferometric synthetic aperture radar images. From the end of the 1997 eruption through summer 2004, magma storage increased by 3.2–4.5 × 107 m3, which corresponds to 75–85% of the magma volume erupted in 1997. Thereafter, the average magma supply rate decreased such that by 10 July 2008, 2 days before the start of the 2008 eruption, magma storage had increased by 3.7–5.2 × 107 m3 or 85–100% of the 1997 eruption volume. We propose that the supply rate decreased in response to the diminishing pressure gradient between the shallow storage zone and a deeper magma source region. Eventually the effects of continuing magma supply and vesiculation of stored magma caused a critical pressure threshold to be exceeded, triggering the 2008 eruption. A similar pattern of initially rapid inflation followed by oscillatory but generally slowing inflation was observed prior to the 1997 eruption. In both cases, withdrawal of magma during the eruptions depressurized the shallow storage zone, causing significant volcano-wide subsidence and initiating a new intereruption deformation cycle.

  14. Pressure effect on Fe3+/FeT in silicate melts and applications to magma redox, particularly in magma oceans

    Science.gov (United States)

    Zhang, H.; Hirschmann, M. M.

    2014-12-01

    The proportions of Fe3+ and Fe2+ in magmas reflect the redox conditions of their origin and influence the chemical and physical properties of natural silicate liquids, but the relationship between Fe3+/FeT and oxygen fugacity depends on pressure owing to different molar volumes and compressibilities of Fe3+ and Fe2+ in silicates. An important case where the effect of pressure effect may be important is in magma oceans, where well mixed (and therefore potentially uniform Fe3+/FeT) experiencses a wide range of pressures, and therefore can impart different ƒO2 at different depths, influencing magma ocean degassing and early atmospheres, as well as chemical gradients within magma oceans. To investigate the effect of pressure on magmatic Fe3+/FeT we conducted high pressure expeirments on ƒO2-buffered andestic liquids. Quenched glasses were analyzed by Mössbauer spectroscopy. To verify the accuracy of Mössbauer determinations of Fe3+/FeT in glasses, we also conducted low temperature Mössbauer studies to determine differences in the recoilless fraction (ƒ) of Fe2+ and Fe3. These indicate that room temperature Mössbauer determinations of on Fe3+/FeT glasses are systematically high by 4% compared to recoilless-fraction corrected ratios. Up to 7 GPa, pressure decreases Fe3+/FeT, at fixed ƒO2 relative to metal-oxide buffers, meaning that an isochemical magma will become more reduced with decreasing pressure. Consequently, for small planetary bodies such as the Moon or Mercury, atmospheres overlying their MO will be highly reducing, consisting chiefly of H2 and CO. The same may also be true for Mars. The trend may reverse at higher pressure, as is the case for solid peridotite, and so for Earth, Venus, and possibly Mars, more oxidized atmospheres above MO are possible. Diamond anvil experiments are underway to examine this hypothesis.

  15. The incomplete trajectory of Albanian migration in Greece

    OpenAIRE

    GEMI, Eda

    2015-01-01

    Proceedings from the conference "Governing Irregular Migration : States, Actors and Intermediaries", Athens 8-9 July 2015 The study addresses the irregular migration of Albanians to Greece. In particular, it analyses the key findings of the fieldwork with 87 Albanian migrants, the dynamic of irregular migration from Albania to Greece, the factors and the actors who affect them as well as the success or failure of the relevant migration policies. The report shows that the expanding possibil...

  16. Moldovan Perception of Greece as a Tourism Destination

    OpenAIRE

    Stela Cazacu

    2017-01-01

    Purpose: This research study analyzes Moldovans' intentions to visit Greece, and their perceptions of Greece's image as a tourism destination, according to the following dimensions: (1) environmental beauty and convenience, (2) country's citizens, (3) place and architectural structure, (4) shopping and tourist accommodation and (5) similarity of the local culture and cuisine with the Moldovan one. The goal is split into four objectives. Design/methodology/approach: For attaining the goal,...

  17. Isolation of Legionella pneumophila from hotels of Greece.

    Science.gov (United States)

    Alexiou, S D; Antoniadis, A; Papapaganagiotou, J; Stefanou, T

    1989-03-01

    Twenty water samples collected from 6 hotels situated in various areas of Greece were examined for the presence of Legionella pneumophila and Legionella-like organisms. Five of the six hotels included in this investigation were associated with cases of legionellosis. Legionella pneumophila serogroups 1 and 8 were isolated from four of six hotels, mainly from the hot water supply system. This is the first isolation and identification of L. pneumophila in Greece.

  18. Developing Youth Football Academies in Greece: Managing Issues and Challenges

    OpenAIRE

    Chris Trikalis; Zisis Papanikolaou; Sofia Trikali

    2014-01-01

    Present study firstly investigated the goals and objectives of youth football academies in Greece, according to the different sector that they operate (public, private, voluntary) and secondly created proposals for future youth football academies development. Research was conducted in Greece, at the period of 2010-2011. Fourteen youth football academies participated in this study and divided into three categories (five academies in commercial sector, four academies in public sector, and five ...

  19. The expected greenhouse benefits from developing magma power at Long Valley, California

    International Nuclear Information System (INIS)

    Haraden, John.

    1995-01-01

    Magma power is the production of electricity from shallow magma bodies. Before magma becomes a practical source of power, many engineering problems must still be solved. When they are solved, the most likely site for the first magma power plant is Long Valley, California, USA. In this paper, we examine the greenhouse benefits from developing Long Valley. By generating magma power and by curtailing an equal amount of fossil power, we estimate the expected mass and the expected discounted value of reduced CO 2 emissions. For both measures, the expected benefits seem to be substantial. (author)

  20. Tube pumices as strain markers of the ductile-brittle transition during magma fragmentation

    Science.gov (United States)

    Martí, J.; Soriano, C.; Dingwell, D. B.

    1999-12-01

    Magma fragmentation-the process by which relatively slow-moving magma transforms into a violent gas flow carrying fragments of magma-is the defining feature of explosive volcanism. Yet of all the processes involved in explosively erupting systems, fragmentation is possibly the least understood. Several theoretical and laboratory studies on magma degassing and fragmentation have produced a general picture of the sequence of events leading to the fragmentation of silicic magma. But there remains a debate over whether magma fragmentation is a consequence of the textural evolution of magma to a foamed state where disintegration of walls separating bubbles becomes inevitable due to a foam-collapse criterion, or whether magma is fragmented purely by stresses that exceed its tensile strength. Here we show that tube pumice-where extreme bubble elongation is observed-is a well-preserved magmatic `strain marker' of the stress state immediately before and during fragmentation. Structural elements in the pumice record the evolution of the magma's mechanical response from viscous behaviour (foaming and foam elongation) through the plastic or viscoelastic stage, and finally to brittle behaviour. These observations directly support the hypothesis that fragmentation occurs when magma undergoes a ductile-brittle transition and stresses exceed the magma's tensile strength.

  1. Terrestrial magma ocean and core segregation in the earth

    Science.gov (United States)

    Ohtani, Eiji; Yurimoto, Naoyoshi

    1992-01-01

    According to the recent theories of formation of the earth, the outer layer of the proto-earth was molten and the terrestrial magma ocean was formed when its radius exceeded 3000 km. Core formation should have started in this magma ocean stage, since segregation of metallic iron occurs effectively by melting of the proto-earth. Therefore, interactions between magma, mantle minerals, and metallic iron in the magma ocean stage controlled the geochemistry of the mantle and core. We have studied the partitioning behaviors of elements into the silicate melt, high pressure minerals, and metallic iron under the deep upper mantle and lower mantle conditions. We employed the multi-anvil apparatus for preparing the equilibrating samples in the ranges from 16 to 27 GPa and 1700-2400 C. Both the electron probe microanalyzer (EPMA) and the Secondary Ion Mass spectrometer (SIMS) were used for analyzing the run products. We obtained the partition coefficients of various trace elements between majorite, Mg-perovskite, and liquid, and magnesiowustite, Mg-perovskite, and metallic iron. The examples of the partition coefficients of some key elements are summarized in figures, together with the previous data. We may be able to assess the origin of the mantle abundances of the elements such as transition metals by using the partitioning data obtained above. The mantle abundances of some transition metals expected by the core-mantle equilibrium under the lower mantle conditions cannot explain the observed abundance of some elements such as Mn and Ge in the mantle. Estimations of the densities of the ultrabasic magma Mg-perovskite at high pressure suggest existence of a density crossover in the deep lower mantle; flotation of Mg-perovskite occurs in the deep magma ocean under the lower mantle conditions. The observed depletion of some transition metals such as V, Cr, Mn, Fe, Co, and Ni in the mantle may be explained by the two stage process, the core-mantle equilibrium under the lower

  2. Depths of Magma Chambers in the Icelandic Crust

    Science.gov (United States)

    Kelley, D. F.; Kapostasy, D. D.; Barton, M.

    2004-05-01

    There is considerable interest in the structure and thermal state of the crust in Iceland, which lies across the Mid Atlantic Ridge. However, interpretations of seismic and gravity data yield conflicting views of the nature of the lower crust. Some interpretations prefer a model in which the lower crust (15-25 km) is relatively cool and solid, whereas other interpretations, based largely on gravity data, prefer a model in which the lower crust is relatively warm and possibly partially molten. Knowledge of the depth of magma chambers is critical to constrain the geothermal gradient in Icelandic crust and to resolve discrepancies in interpretation of geophysical data. Analyses of aphyric lavas and of glasses in Icelandic lavas erupted from 11 volcanic centers have been compiled. The compositions are picritic and basaltic with SiO2 - 47 to 50 wt%, MgO - 6 to 15wt%, FeO - 8 to 14wt%, to, Na2O - 1.3 to 3.3 wt%, and K2O - 0.03-46 wt%. The pressures of equilibration of these liquids with ol, high-Ca pyx and plag were estimated qualitatively from projections into the pseudoternary system Ol-Di-Silica using methods described by Walker and coworkers and Grove and coworkers. The results (ca. 0.5 GPa) indicate crystallization in magma chambers located at about 16 km depth. Equilibration pressures were also calculated using the method described by Yang and coworkers and by a modified version of this method. Calculated pressures (0.45±0.15 GPa) indicate magma chambers located at 15±4 km depth. Equilibration pressures for Rekjanes Ridge glasses determined using the same techniques are 0.2±0.1 GPa, corresponding to depths of 7.6±3 km. The results indicate the presence of magma chambers in the deep Icelandic crust and that the latter is relatively warm. Shallower chambers (3-7 km) have been identified from seismic studies suggesting a complex magma plumbing system. The results also confirm that magma chambers beneath Iceland are located at greater depths than those beneath the

  3. When Magma Meets Carbonate: Explosive Criminals of Climate Change?

    Science.gov (United States)

    Carter, L. B.

    2017-12-01

    The natural carbon cycle is a key component of global climate change. Identifying and quantifying all processes in the cycle is essential to determine the effects of human greenhouse gas contributions and make future predictions. Volcanoes are the main natural source of carbon dioxide to the atmosphere [1]. In settings where carbonate rocks underlie the edifice, they can be consumed by magma passing through, which can release extra CO2, potentially explaining the extremely high emissions at Mount Etna in Italy [2-4]. We conduct laboratory experiments, mimicking conditions in the crust, to study how different carbonate rocks interact with hot magmas at pressure, and determine the amount of CO2 generated. We find that some types of magma can raise volcanic gas output and cause more explosive and dangerous eruptions [5-6]. Others are more likely to release hot fluids to the surrounding rocks, releasing CO2 by skarnification, which leaves economically important ores like in the western US [3,7] but can weaken the subsurface, potentially leading to landslides. Gas can also be released on the flanks of a volcano or in regions lacking an active volcano, due to the breakdown of certain carbonate rocks by heat [7], seen as bubbling springs in Yellowstone [8]. Our experiments indicate that if dolostone, not limestone, surrounds a magma chamber, over half the CO2 that was locked in the crust can escape even at lower temperatures a distance away. These processes are perhaps pertinent to why the Earth's climate was warm >50 million years ago, when more magma-carbonate interaction likely occurred than today [3] and thus contributed several times the current volcanic output [4] to the atmosphere. As significant parts of the long-term carbon cycle, it is necessary to include magma-carbonate reactions when considering climate changes before taking into account human input. [1] Aiuppa et al 2017 ESciRev (168) 24-47; [2] Ganino and Arndt 2009 Geol (37) 323-326; [3] Lee et al. 2013

  4. Degassing during magma ascent in the Mule Creek vent (USA)

    Science.gov (United States)

    Stasiuk, M.V.; Barclay, J.; Carroll, M.R.; Jaupart, Claude; Ratte, J.C.; Sparks, R.S.J.; Tait, S.R.

    1996-01-01

    The structures and textures of the rhyolite in the Mule Creek vent (New Mexico, USA) indicate mechanisms by which volatiles escape from silicic magma during eruption. The vent outcrop is a 300-m-high canyon wall comprising a section through the top of a feeder conduit, vent and the base of an extrusive lava dome. Field relations show that eruption began with an explosive phase and ended with lava extrusion. Analyses of glass inclusions in quartz phenocrysts from the lava indicate that the magma had a pre-eruptive dissolved water content of 2.5-3.0 wt% and, during eruption, the magma would have been water-saturated over the vertical extent of the present outcrop. However, the vesicularity of the rhyolite is substantially lower than that predicted from closed-system models of vesiculation under equilibrium conditions. At a given elevation in the vent, the volume fraction of primary vesicles in the rhyolite increases from zero close to the vent margin to values of 20-40 vol.% in the central part. In the centre the vesicularity increases upward from approximately 20 vol.% at 300 m below the canyon rim to approximately 40 vol.% at 200 m, above which it shows little increase. To account for the discrepancy between observed vesicularity and measured water content, we conclude that gas escaped during ascent, probably beginning at depths greater than exposed, by flow through the vesicular magma. Gas escape was most efficient near the vent margin, and we postulate that this is due both to the slow ascent of magma there, giving the most time for gas to escape, and to shear, favouring bubble coalescence. Such shear-related permeability in erupting magma is supported by the preserved distribution of textures and vesicularity in the rhyolite: Vesicles are flattened and overlapping near the dense margins and become progressively more isolated and less deformed toward the porous centre. Local zones have textures which suggest the coalescence of bubbles to form permeable

  5. Finite automata over magmas: models and some applications in Cryptography

    Directory of Open Access Journals (Sweden)

    Volodymyr V. Skobelev

    2018-05-01

    Full Text Available In the paper the families of finite semi-automata and reversible finite Mealy and Moore automata over finite magmas are defined and analyzed in detail. On the base of these models it is established that the set of finite quasigroups is the most acceptable subset of the set of finite magmas at resolving model problems in Cryptography, such as design of iterated hash functions and stream ciphers. Defined families of finite semi-automata and reversible finite automata over finite $T$-quasigroups are investigated in detail. It is established that in this case models time and space complexity for simulation of the functioning during one instant of automaton time can be much lower than in general case.

  6. A magma ocean and the Earth's internal water budget

    Science.gov (United States)

    Ahrens, Thomas J.

    1992-01-01

    There are lines of evidence which relate bounds on the primordial water content of the Earth's mantle to a magma ocean and the accompanying Earth accretion process. We assume initially (before a magma ocean could form) that as the Earth accreted, it grew from volatile- (H2O, CO2, NH3, CH4, SO2, plus noble) gas-rich planetesimals, which accreted to form an initial 'primitive accretion core' (PAC). The PAC retained the initial complement of planetesimal gaseous components. Shock wave experiments in which both solid, and more recently, the gaseous components of materials such as serpentine and the Murchison meteorite have demonstrated that planetesimal infall velocities of less than 0.5 km/sec, induce shock pressures of less than 0.5 GPa and result in virtually complete retention of planetary gases.

  7. Evidence of a global magma ocean in Io's interior.

    Science.gov (United States)

    Khurana, Krishan K; Jia, Xianzhe; Kivelson, Margaret G; Nimmo, Francis; Schubert, Gerald; Russell, Christopher T

    2011-06-03

    Extensive volcanism and high-temperature lavas hint at a global magma reservoir in Io, but no direct evidence has been available. We exploited Jupiter's rotating magnetic field as a sounding signal and show that the magnetometer data collected by the Galileo spacecraft near Io provide evidence of electromagnetic induction from a global conducting layer. We demonstrate that a completely solid mantle provides insufficient response to explain the magnetometer observations, but a global subsurface magma layer with a thickness of over 50 kilometers and a rock melt fraction of 20% or more is fully consistent with the observations. We also place a stronger upper limit of about 110 nanoteslas (surface equatorial field) on the dynamo dipolar field generated inside Io.

  8. Thermally-assisted Magma Emplacement Explains Restless Calderas

    Science.gov (United States)

    Amoruso, A.; Crescentini, L.; D'Antonio, M.; Acocella, V.

    2017-12-01

    Many calderas show repeated unrest over centuries. Though probably induced by magma, this unique behaviour is not understood and its dynamics remains elusive. To better understand these restless calderas, we interpret deformation data and build thermal models of Campi Flegrei, Italy, which is the best-known, yet most dangerous calderas, lying to the west of Naples and restless since the 1950s at least.Our elaboration of the geodetic data indicates that the inflation and deflation of magmatic sources at the same location explain most deformation, at least since the build-up of the last 1538 AD eruption. However, such a repeated magma emplacement requires a persistently hot crust.Our thermal models show that the repeated emplacement was assisted by the thermal anomaly created by magma that was intruded at shallow depth 3 ka before the last eruption and, in turn, contributed to maintain the thermal anomaly itself. This may explain the persistence of the magmatic sources promoting the restless behaviour of the Campi Flegrei caldera; moreover, it explains the crystallization, re-melting and mixing among compositionally distinct magmas recorded in young volcanic rocks.Available information at other calderas highlights similarities to Campi Flegrei, in the pattern and cause of unrest. All monitored restless calderas have either geodetically (Yellowstone, Aira Iwo-Jima, Askja, Fernandina and, partly, Long Valley) or geophysically (Rabaul, Okmok) detected sill-like intrusions inducing repeated unrest. Some calderas (Yellowstone, Long Valley) also show stable deformation pattern, where inflation insists on and mimics the resurgence uplift. The common existence of sill-like sources, also responsible for stable deformation patterns, in restless calderas suggests close similarities to Campi Flegrei. This suggests a wider applicability of our model of thermally-assisted sill emplacement, to be tested by future studies to better understand not only the dynamics of restless

  9. MAGMA: generalized gene-set analysis of GWAS data.

    Science.gov (United States)

    de Leeuw, Christiaan A; Mooij, Joris M; Heskes, Tom; Posthuma, Danielle

    2015-04-01

    By aggregating data for complex traits in a biologically meaningful way, gene and gene-set analysis constitute a valuable addition to single-marker analysis. However, although various methods for gene and gene-set analysis currently exist, they generally suffer from a number of issues. Statistical power for most methods is strongly affected by linkage disequilibrium between markers, multi-marker associations are often hard to detect, and the reliance on permutation to compute p-values tends to make the analysis computationally very expensive. To address these issues we have developed MAGMA, a novel tool for gene and gene-set analysis. The gene analysis is based on a multiple regression model, to provide better statistical performance. The gene-set analysis is built as a separate layer around the gene analysis for additional flexibility. This gene-set analysis also uses a regression structure to allow generalization to analysis of continuous properties of genes and simultaneous analysis of multiple gene sets and other gene properties. Simulations and an analysis of Crohn's Disease data are used to evaluate the performance of MAGMA and to compare it to a number of other gene and gene-set analysis tools. The results show that MAGMA has significantly more power than other tools for both the gene and the gene-set analysis, identifying more genes and gene sets associated with Crohn's Disease while maintaining a correct type 1 error rate. Moreover, the MAGMA analysis of the Crohn's Disease data was found to be considerably faster as well.

  10. The chlorine isotope fingerprint of the lunar magma ocean.

    Science.gov (United States)

    Boyce, Jeremy W; Treiman, Allan H; Guan, Yunbin; Ma, Chi; Eiler, John M; Gross, Juliane; Greenwood, James P; Stolper, Edward M

    2015-09-01

    The Moon contains chlorine that is isotopically unlike that of any other body yet studied in the Solar System, an observation that has been interpreted to support traditional models of the formation of a nominally hydrogen-free ("dry") Moon. We have analyzed abundances and isotopic compositions of Cl and H in lunar mare basalts, and find little evidence that anhydrous lava outgassing was important in generating chlorine isotope anomalies, because (37)Cl/(35)Cl ratios are not related to Cl abundance, H abundance, or D/H ratios in a manner consistent with the lava-outgassing hypothesis. Instead, (37)Cl/(35)Cl correlates positively with Cl abundance in apatite, as well as with whole-rock Th abundances and La/Lu ratios, suggesting that the high (37)Cl/(35)Cl in lunar basalts is inherited from urKREEP, the last dregs of the lunar magma ocean. These new data suggest that the high chlorine isotope ratios of lunar basalts result not from the degassing of their lavas but from degassing of the lunar magma ocean early in the Moon's history. Chlorine isotope variability is therefore an indicator of planetary magma ocean degassing, an important stage in the formation of terrestrial planets.

  11. Isotopic abundances relevant to the identification of magma sources

    International Nuclear Information System (INIS)

    O'Nions, R.K.

    1984-01-01

    The behaviour of natural radiogenic isotope tracers in the Earth that have lithophile and atmophile geochemical affinity is reviewed. The isotope tracer signature of oceanic and continental crust may in favourable circumstances by sufficiently distinct from that of the mantle to render a contribution from these sources resolvable within the isotopic composition of the magma. Components derived from the sedimentary and altered basaltic portion of oceanic crust are recognized in some island arc magmas from their Sr, Nd and Pb isotopic signatures. The rare-gas isotope tracers (He, Ar, Xe in particular) are not readily recycled into the mantle and thus provide the basis of an approach that is complementary to that based on the lithophile tracers. In particular, a small mantle-derived helium component may be readily recognized in the presence of a predominant radiogenic component generated in the continents. The importance of assessing the mass balance of these interactions rather than merely a qualitative recognition is emphasized. The question of the relative, contribution of continental-oceanic crust and mantle to magma sources is an essential part of the problem of generation and evolution of continental crust. An approach to this problem through consideration of the isotopic composition of sediments is briefly discussed. (author)

  12. Parental magmas of Mare Fecunditatis - Evidence from pristine glasses

    International Nuclear Information System (INIS)

    Jin, Y.; Taylor, L.A.

    1990-01-01

    Results are presented on the petrography and electron microprobe analyses of 14 discrete glass beads from the Luna 16 core sample (21036,15) from Mare Fecunditatis regolith, that were previously characterized as representing pristine glasses. Compared to Apollo pristine glasses analyzed by Delano (1986), the Luna 16 pristine glasses have higher CaO and Al2O3 contents but lower MgO and Ni. On the basis of their contents of MgO, FeO, Al2O3, and CaO, these pristine glasses could be divided into two groups, A and B. It is suggested that at least two parental magmas are needed to explain the chemical variations among these glasses. The Group B glasses appear to represent primitive parental magma that evolved by olivine fractionation to the compositions of the Luna 16 aluminous mare basalts, whereas the Group A volcanic glasses may represent an unusual new basalt magma type that contains a high plagioclase component. 14 refs

  13. Automatic Compound Annotation from Mass Spectrometry Data Using MAGMa.

    Science.gov (United States)

    Ridder, Lars; van der Hooft, Justin J J; Verhoeven, Stefan

    2014-01-01

    The MAGMa software for automatic annotation of mass spectrometry based fragmentation data was applied to 16 MS/MS datasets of the CASMI 2013 contest. Eight solutions were submitted in category 1 (molecular formula assignments) and twelve in category 2 (molecular structure assignment). The MS/MS peaks of each challenge were matched with in silico generated substructures of candidate molecules from PubChem, resulting in penalty scores that were used for candidate ranking. In 6 of the 12 submitted solutions in category 2, the correct chemical structure obtained the best score, whereas 3 molecules were ranked outside the top 5. All top ranked molecular formulas submitted in category 1 were correct. In addition, we present MAGMa results generated retrospectively for the remaining challenges. Successful application of the MAGMa algorithm required inclusion of the relevant candidate molecules, application of the appropriate mass tolerance and a sufficient degree of in silico fragmentation of the candidate molecules. Furthermore, the effect of the exhaustiveness of the candidate lists and limitations of substructure based scoring are discussed.

  14. Concentration variance decay during magma mixing: a volcanic chronometer.

    Science.gov (United States)

    Perugini, Diego; De Campos, Cristina P; Petrelli, Maurizio; Dingwell, Donald B

    2015-09-21

    The mixing of magmas is a common phenomenon in explosive eruptions. Concentration variance is a useful metric of this process and its decay (CVD) with time is an inevitable consequence during the progress of magma mixing. In order to calibrate this petrological/volcanological clock we have performed a time-series of high temperature experiments of magma mixing. The results of these experiments demonstrate that compositional variance decays exponentially with time. With this calibration the CVD rate (CVD-R) becomes a new geochronometer for the time lapse from initiation of mixing to eruption. The resultant novel technique is fully independent of the typically unknown advective history of mixing - a notorious uncertainty which plagues the application of many diffusional analyses of magmatic history. Using the calibrated CVD-R technique we have obtained mingling-to-eruption times for three explosive volcanic eruptions from Campi Flegrei (Italy) in the range of tens of minutes. These in turn imply ascent velocities of 5-8 meters per second. We anticipate the routine application of the CVD-R geochronometer to the eruptive products of active volcanoes in future in order to constrain typical "mixing to eruption" time lapses such that monitoring activities can be targeted at relevant timescales and signals during volcanic unrest.

  15. Immigrants: A Study Case for N. Greece

    Directory of Open Access Journals (Sweden)

    Maria Vlachadi

    2014-05-01

    Full Text Available It is a fact that the phenomenon of immigration constitutes, during the last years, the view of a new social and economic reality for the societies of most western European countries. Greece has received for the first time, during the 1990s, thousands of economic immigrants who appear not only in the big city centers but also in small country towns. Immigrants probably constitute the most discussed issue in the Modern Greek society, in an economic conjuncture in which the economic crisis has functioned in a catalytic way for the diffusion of insecurity in the native population (Biblionet, 2012. The Greek state was not ready to accept such a large number of immigrants in so little time. It showed hesitance and could not keep a steady position as far as the promotion of a necessary institutional framework for their integration in the Greek society was concerned. This initial surprise has never been overcome. In Greece, as well as in the rest of the European South, the majority of the immigrants entering the country illegally have supplied the informal working market. Even when they become legal, the available working positions for them presuppose low specialization with low payments, hard work and limited opportunities of improvement of their social and occupational status. Although the immigration phenomenon is usually approached in a national level, the local level is considered the most suitable one to deal with the interaction of its economic, social, political and cultural dimensions. Recent studies have shown their positive contribution in the revival of Greek agriculture and Greek agricultural districts in general. Within the scale of the Greek community and the degree in which it constitutes a place of constant flow of human resources, it is inevitable the general presence of immigrants to raise issues of mutual infiltrations among different national populations within which there arise interaction issues and intercultural interdependence

  16. Moldovan Perception of Greece as a Tourism Destination

    Directory of Open Access Journals (Sweden)

    Stela Cazacu

    2017-06-01

    Full Text Available Purpose: This research study analyzes Moldovans' intentions to visit Greece, and their perceptions of Greece's image as a tourism destination, according to the following dimensions: (1 environmental beauty and convenience, (2 country's citizens, (3 place and architectural structure, (4 shopping and tourist accommodation and (5 similarity of the local culture and cuisine with the Moldovan one. The goal is split into four objectives. Design/methodology/approach: For attaining the goal, a self-administered questionnaire was delivered. The empirical study was conducted in the capital of Moldova. The findings are based upon a sample of 139 respondents. Findings: The findings reveal that, overall, Greece's image as a tourist destination among Moldovan consumers is partially positive. The perceptions of the tourism dimensions were evaluated in the descending order as follows: place and architectural structure, shopping and tourist accommodation, environmental beauty and convenience, country's citizens and similarity of the local culture and cuisine with the Moldovan one. Research limitations/implications: As it was undertaken only in the capital of Republic of Moldova and because most respondents are young people and females, the findings of this investigation do not absolutely reflect the perceptions of all Moldovans. Also, because the number of respondents is small, it is not representative of the whole Moldovan population. Hence, the results might not be very realistic and accurate. Originality/value: This study provides insightful theoretical implications and practical recommendations in creating marketing strategies that would help in managing and improving Greece's image as a destination among Moldovan tourists. Also, no study, at least to the researcher's knowledge, has evaluated Greece's image as a destination among Moldovan consumers. Finally, due to the increasing number of Moldovan tourists in Greece, it is important that Greece grasps this

  17. Making mushy magma chambers in the lower continental crust: Cold storage and compositional bimodality

    Science.gov (United States)

    Jackson, Matthew; Blundy, Jon; Sparks, Steve

    2017-04-01

    Increasing geological and geophysical evidence suggests that crustal magma reservoirs are normally low melt fraction 'mushes' rather than high melt fraction 'magma chambers'. Yet high melt fractions must form within these mush reservoirs to explain the observed flow and eruption of low crystallinity magmas. In many models, crystallinity is linked directly to temperature, with higher temperature corresponding to lower crystallinity (higher melt fraction). However, increasing temperature yields less evolved (silicic) melt composition for a given starting material. If mobile, low crystallinity magmas require high temperature, it is difficult to explain how they can have evolved composition. Here we use numerical modelling to show that reactive melt flow in a porous and permeable mush reservoir formed by the intrusion of numerous basaltic sills into the lower continental crust produces magma in high melt fraction (> 0.5) layers akin to conventional magma chambers. These magma-chamber-like layers contain evolved (silicic) melt compositions and form at low (close to solidus) temperatures near the top of the mush reservoir. Evolved magma is therefore kept in 'cold storage' at low temperature, but also at low crystallinity so the magma is mobile and can leave the mush reservoir. Buoyancy-driven reactive flow and accumulation of melt in the mush reservoir controls the temperature and composition of magma that can leave the reservoir. The modelling also shows that processes in lower crustal mush reservoirs produce mobile magmas that contain melt of either silicic or mafic composition. Intermediate melt compositions are present but are not within mobile magmas. Silicic melt compositions are found at high melt fraction within the magma-chamber like layers near the top of the mush reservoir. Mafic melt compositions are found at high melt fraction within the cooling sills. Melt elsewhere in the reservoir has intermediate composition, but remains trapped in the reservoir because

  18. Oxygen isotope study of the Long Valley magma system, California: isotope thermometry and convection in large silicic magma bodies

    Science.gov (United States)

    Bindeman, Ilya; Valley, John

    2002-07-01

    Products of voluminous pyroclastic eruptions with eruptive draw-down of several kilometers provide a snap-shot view of batholith-scale magma chambers, and quench pre-eruptive isotopic fractionations (i.e., temperatures) between minerals. We report analyses of oxygen isotope ratio in individual quartz phenocrysts and concentrates of magnetite, pyroxene, and zircon from individual pumice clasts of ignimbrite and fall units of caldera-forming 0.76 Ma Bishop Tuff (BT), pre-caldera Glass Mountain (2.1-0.78 Ma), and post-caldera rhyolites (0.65-0.04 Ma) to characterize the long-lived, batholith-scale magma chamber beneath Long Valley Caldera in California. Values of δ18O show a subtle 1‰ decrease from the oldest Glass Mountain lavas to the youngest post-caldera rhyolites. Older Glass Mountain lavas exhibit larger ( 1‰) variability of δ18O(quartz). The youngest domes of Glass Mountain are similar to BT in δ18O(quartz) values and reflect convective homogenization during formation of BT magma chamber surrounded by extremely heterogeneous country rocks (ranging from 2 to +29‰). Oxygen isotope thermometry of BT confirms a temperature gradient between "Late" (815 °C) and "Early" (715 °C) BT. The δ18O(quartz) values of "Early" and "Late" BT are +8.33 and 8.21‰, consistent with a constant δ18O(melt)=7.8+/-0.1‰ and 100 °C temperature difference. Zircon-melt saturation equilibria gives a similar temperature range. Values of δ18O(quartz) for different stratigraphic units of BT, and in pumice clasts ranging in pre-eruptive depths from 6 to 11 km (based on melt inclusions), and document vertical and lateral homogeneity of δ18O(melt). Worldwide, five other large-volume rhyolites, Lava Creek, Lower Bandelier, Fish Canyon, Cerro Galan, and Toba, exhibit equal δ18O(melt) values of earlier and later erupted portions in each of the these climactic caldera-forming eruptions. We interpret the large-scale δ18O homogeneity of BT and other large magma chambers as evidence

  19. Buffered and unbuffered dike emplacement on Earth and Venus - Implications for magma reservoir size, depth, and rate of magma replenishment

    Science.gov (United States)

    Parfitt, E. A.; Head, J. W., III

    1993-01-01

    Models of the emplacement of lateral dikes from magma chambers under constant (buffered) driving pressure conditions and declining (unbuffered) driving pressure conditions indicate that the two pressure scenarios lead to distinctly different styles of dike emplacement. In the unbuffered case, the lengths and widths of laterally emplaced dikes will be severely limited and the dike lengths will be highly dependent on chamber size; this dependence suggests that average dike length can be used to infer the dimensions of the source magma reservoir. On Earth, the characteristics of many mafic-dike swarms suggest that they were emplaced in buffered conditions (e.g., the Mackenzie dike swarm in Canada and some dikes within the Scottish Tertiary). On Venus, the distinctive radial fractures and graben surrounding circular to oval features and edifices on many size scales and extending for hundreds to over a thousand km are candidates for dike emplacement in buffered conditions.

  20. Geochemical evidences of magma dynamics at Campi Flegrei (Italy)

    Science.gov (United States)

    Caliro, S.; Chiodini, G.; Paonita, A.

    2014-05-01

    Campi Flegrei caldera, within the Neapolitan area of Italy, is potentially one of the most dangerous volcanoes in the world, and during the last decade it has shown clear signs of reactivation, marked by the onset of uplift and changes in the geochemistry of gas emissions. We describe a 30-year-long data set of the CO2-He-Ar-N2 compositions of fumarolic emissions from La Solfatara crater, which is located in the center of the caldera. The data display continuous decreases in both the N2/He and N2/CO2 ratios since 1985, paralleled by an increase in He/CO2. These variations cannot be explained by either processes of boiling/condensation in the local hydrothermal system or with changes in the mixing proportions between a magmatic vapor and hydrothermal fluids. We applied the magma degassing model of Nuccio and Paonita (2001, Earth Planet. Sci. Lett. 193, 467-481) using the most recent inert-gas solubilities in order to interpret these peculiar features in accordance with petrologic constraints derived from the ranges of the melt compositions and reservoir pressures at Campi Flegrei. The model simulations for mafic melts (trachybasalt and shoshonite) show a remarkably good agreement with the measured data. Both decompressive degassing of an ascending magma and mixing between magmatic fluids exsolved at various levels along the ascent path can explain the long-term geochemical changes. Recalling that (i) a sill-like reservoir of gases at a depth of 3-4 km seems to be the main source of ground inflation and (ii) there is petrologic and geophysical evidence for a reservoir of magma at about 8 km below Campi Flegrei, we suggest that the most-intense episodes of inflation occur when the gas supply to the sill-like reservoir comes from the 8 km-deep magma, although fluids exsolved by magma bodies at shallower depths also contribute to the gas budget. Our work highlights that, in caldera systems where the presence of hydrothermal aquifers commonly masks the magmatic signature

  1. Computer Simulation To Assess The Feasibility Of Coring Magma

    Science.gov (United States)

    Su, J.; Eichelberger, J. C.

    2017-12-01

    Lava lakes on Kilauea Volcano, Hawaii have been successfully cored many times, often with nearly complete recovery and at temperatures exceeding 1100oC. Water exiting nozzles on the diamond core bit face quenches melt to glass just ahead of the advancing bit. The bit readily cuts a clean annulus and the core, fully quenched lava, passes smoothly into the core barrel. The core remains intact after recovery, even when there are comparable amounts of glass and crystals with different coefficients of thermal expansion. The unique resulting data reveal the rate and sequence of crystal growth in cooling basaltic lava and the continuous liquid line of descent as a function of temperature from basalt to rhyolite. Now that magma bodies, rather than lava pooled at the surface, have been penetrated by geothermal drilling, the question arises as to whether similar coring could be conducted at depth, providing fundamentally new insights into behavior of magma. This situation is considerably more complex because the coring would be conducted at depths exceeding 2 km and drilling fluid pressures of 20 MPa or more. Criteria that must be satisfied include: 1) melt is quenched ahead of the bit and the core itself must be quenched before it enters the barrel; 2) circulating drilling fluid must keep the temperature of the coring assembling cooled to within operational limits; 3) the drilling fluid column must nowhere exceed the local boiling point. A fluid flow simulation was conducted to estimate the process parameters necessary to maintain workable temperatures during the coring operation. SolidWorks Flow Simulation was used to estimate the effect of process parameters on the temperature distribution of the magma immediately surrounding the borehole and of drilling fluid within the bottom-hole assembly (BHA). A solid model of the BHA was created in SolidWorks to capture the flow behavior around the BHA components. Process parameters used in the model include the fluid properties and

  2. Magma Mixing: Magmatic Enclaves in Morne Micotrin, Dominica

    Science.gov (United States)

    Hickernell, S.; Frey, H. M.; Manon, M. R. F.; Waters, L. E.

    2017-12-01

    Magmatic enclaves in volcanic rocks provide direct evidence of magma mingling/mixing within a magma reservoir and may reinvigorate the system and trigger eruption, as documented at the Soufriere Hills in Montserrat. Lava domes on the neighboring island of Dominica also contain multiple enclave populations and may be evidence for similar magma chamber processes. The central dome of Micotrin is at the head of the Roseau Valley, which was filled with 3 km3 of pyroclastic deposits from eruptions spanning 65 - 25 ka. There appear to be two distinct types of enclaves in the crystal-rich Micotrin andesites (60 wt% SiO2), fine-grained and coarse-grained. Fine-grained mafic enclaves (52 wt% SiO2) vary in size from 1 to 15 cm in diameter, whereas the coarse-grained enclaves are generally larger and range from 3-20 cm. Fine-grained enclaves are saturated in plag (35%) + opx (35%) + cpx (20%) + oxides (10%). Average pyroxenes are 0.01 to 0.02 cm in size, whereas plagioclase averages 0.05 cm and up to 0.1 cm. The texture of the fine-grained enclaves is cumulate-like, devoid of microlites and matrix glass. Coarse-grained enclaves lack cpx and have different modal abundances and textures: plag (75%) + opx (10%) + oxides (5%) + plag microlites (10%). Plagioclase are 0.1 cm in size and orthopyroxenes average 0.05 cm. The coarse-grained enclaves are highly vesicular, a notable difference from the host as well as the fine-grained enclaves. The boundaries of both the fine- and coarse-grained enclaves are quite sharp and distinct and there do not appear to be enclave minerals disaggregated in the host rock. Temperatures were determined by two oxides. The fine-grained enclaves had two populations of magnetite, yielding 847 + 21° and 920 + 17°C. The coarse-grained enclave was 890 + 42 °C, but the oxides were extensively exsolved. Plagioclase composition in both coarse and fine-grained samples was comparable, ranging from An50 to An80. Despite compositional similarity the textures of

  3. [Financial crisis and mental health in Greece].

    Science.gov (United States)

    Giotakos, O; Karabelas, D; Kafkas, A

    2011-01-01

    Several studies indicate an association between economic crises and psychological burden. To investigate the possible impact of the current economic crisis on mental health in Greece, the association between two economic indicators (unemployment and average income) and mental health variables (psychiatric clinic admittance, visits to outpatients' departments and emergency units, suicides, homicides, mortality rates and divorces) was studied. The data were gathered by the Greek Statistical Service and some others were provided by the following hospitals: Eginition Hospital, Psychiatric Hospital of Attica, Athens General Hospital and Evaggelismos Hospital. Simple and multiple regression analyses were performed on the data. There was no significant correlation between the level of unemployment, as well as the average income, and admittance to the psychiatric clinics. A significant correlation was isolated between unemployment and visits to outpatients' department (R2 = 0.40, p = 0.001) and emergency unit (R2 = 0.49, p = 0.0002) of Eginition Hospital. The unemployment rate during the period 1981-2008 was positively associated with the number of homicides (R2 = 0.16, beta = 0.000049, p = 0.03), as well as the number of divorces (R2 = 0.20, beta = 0.005, p = 0.02) during the same period. The average income showed positive association with the visits to both outpatients' department (R2 = 0.55, p positive correlation between the average income and divorce rates (R2 = 0.73, p impact of economic crisis on citizens' mental health.

  4. Heterosexual transmission of HIV in Greece.

    Science.gov (United States)

    Roumelioutou-Karayannis, A; Nestoridou, K; Mandalaki, T; Stefanou, T; Papaevangelou, G

    1988-06-01

    To provide further evidence for the heterosexual transmission of the acquired immunodeficiency syndrome (AIDS) in Greece we examined 53 Greek female steady heterosexual partners of 53 anti-HIV-positive men. Human immunodeficiency virus (HIV) transmission was estimated by the detection of anti-HIV antibodies. Our results showed that 27.8% (5 of 18) of the female partners of bisexuals, 33.3% (2 of 6) of intravenous drug abusers (IVDA), and 100% (4 of 4) of those who had lived for a long time in Africa were found anti-HIV positive. In contrast, only 4% (1 of 25) of the studied sexual partners of hemophiliac carriers were found to be HIV seropositive. The use of condoms seemed to be the most important factor in reducing HIV transmission. According to our results the duration of sexual relationships and the practice of anal intercourse did not increase the possibility of seroconversion. These results confirm the heterosexual transmission of HIV. However, further studies should be conducted to evaluate the relative role of various risk factors and the overall importance of heterosexual spread of HIV infections.

  5. Update of geothermal energy development in Greece

    International Nuclear Information System (INIS)

    Koutroupis, N.

    1992-01-01

    Following the completion of the Geothermal Reconnaissance Study in Greece and the successful drilling of seven deep geothermal wells in the Aegean islands of Milos and Nisyros, PPC started the first step towards geothermal development for electricity production as follows: A geothermal electric pilot plant of 2 MW e nominal capacity was installed on the Zephyria plain in Milos island (1985). During a nine month operation of the plant, problems connected with its long term operation were solved (hot reinjection of the high salinity brine, turbine washing etc). A feasibility study regarding exploitation of the Nisyros geothermal resources was completed and PPC connected Nisyros island electrically to Kos island via submarine cables. As consequence of the reaction against geothermal development by the people of Milos in early 1989, the power plant is still out of operation and the feasibility study planned for Milos has been postponed. For similar reasons the Nisyros drilling contract for five new geothermal deep wells has not come into force as yet. This paper summarizes the main PPC geothermal activities to date, the problems caused by the reactions of the Milos and Nisyros population and the relevant PPC countermeasures, as well as outlining the PPC development program for the near future

  6. Laron syndrome. First report from Greece.

    Science.gov (United States)

    Galli-Tsinopoulou, Assimina; Nousia-Arvanitakis, Sanda; Tsinopoulos, Ioannis; Bechlivanides, Christos; Shevah, Orit; Laron, Zvi

    2003-01-01

    Laron-type dwarfism is an autosomal recessive disorder caused by deletions or mutations of the growth hormone receptor gene. It is characterized by high circulating levels of growth hormone (GH) and low levels of insulin-like growth factor I (IGF-I). Patients are refractory to both endogenous and exogenous GH, and present severe growth retardation and obesity. Therapy with recombinant human insulin-like growth factor-I (rhIGF-I) accelerates linear growth. We describe a 2-year old girl with Laron syndrome, who presented with postnatal growth failure and hypoglycaemic seizures. Her evaluation disclosed high GH values during a glucagon test (peak GH value 170 ng/ml) and very low IGF I value (0.1 ng/ml) with no rise following GH administration. The growth velocity improved considerably with the administration of IGF I. Molecular analysis showed a heterozygous mutation on exon 4 of the GH receptor gene, inherited from the mother, a rather puzzling finding considering the clinical findings in mother and infant. This case constitutes the first report of Laron syndrome from Greece.

  7. Sport and medicine in ancient Greece.

    Science.gov (United States)

    Appelboom, T; Rouffin, C; Fierens, E

    1988-01-01

    Sport and medicine in ancient Greece were the result of a widespread tradition of liberty, which was at the heart of one of the most brilliant civilizations in history. Whereas war encouraged the development of surgical knowledge springing out of medical experience on the battlefield, peace promoted the burgeoning of sport as an integral part of Greek upbringing, allowing the channeling of young people's aggressiveness into physical competition. Medicine was magical and mythological, especially in the time of Homer (9th century BC); Aesculapius, the mythical god of healing, was its reference point. With Hippocrates (5th century BC), the body of medical experience was to be codified and built up, and was to undergo a novel evolution based on the theory of the balance of the four humors. The athlete's mentality, faced with trauma in the sports ground, underwent a change; injury was no longer considered a punishment by the gods. At the same time, temple offerings tendered in the hope of victory gave way to the athlete's personal preparation based on a specifically modified lifestyle, diet, and training. The resulting progress in medicine and public health, especially from the 5th century BC onward, was not only to favor athletic performances of high quality but also surgical techniques that were very advanced for their time. Thus it can be seen that the medical knowledge associated with the practice of sport progressed during antiquity because of its obligation to follow the warrior and then the athlete.

  8. Neutron activation analysis of arsenic in Greece

    International Nuclear Information System (INIS)

    Grimanis, A.P.

    1989-01-01

    Arsenic is considered a toxic trace element for plant, animal, and human organisms. Arsenic and certain arsenic compounds have been listed as carcinogens by the U.S. Environmental Protection Agency. Arsenic is emitted in appreciable quantities into the atmosphere by coal combustion and the production of cement. Arsenic enters the aquatic environment through industrial activities such as smelting of metallic ores, metallurgical glassware, and ceramics as well as insecticide production and use. Neutron activation analysis (NAA) is a very sensitive, precise, and accurate method for determining arsenic. This paper is a review of research studies of arsenic in the Greek environment by NAA performed at our radioanalytical laboratory. The objectives of these studies were (a) to determine levels of arsenic concentrations in environmental materials, (b) to pinpoint arsenic pollution sources and estimate the extent of arsenic pollution, and (c) to find out whether edible marine organisms from the gulfs of Greece receiving domestic, industrial, and agricultural wastes have elevated concentrations of arsenic in their tissues that could render them dangerous for human consumption

  9. Burns during Easter festivities in Greece.

    Science.gov (United States)

    Pallantzas, A; Kourakos, P; Stampolidis, N; Papagianni, E; Balagoura, A; Stathopoulos, A; Polizoi, A; Emvalomata, A; Evaggelopoulou, M; Castana, O

    2012-12-31

    Easter is the most important holiday for the Greek Church. It is rich in traditions and rituals but during the Greek Easter festivities, especially at midnight Mass on Easter Saturday night, it is customary to throw fireworks around. These fireworks are not part of the true Easter tradition and they are potentially fatal. Unfortunately, in the past few years, the custom has become more and more popular in Greece. There are some local variations, mainly in the Aegean islands, where homemade rockets are used to have a "rocket war". The rockets consist of wooden sticks loaded with an explosive mixture containing gunpowder and launched from special platforms. Many severe injuries involving loss of sight and limbs as well as major burns are also caused by the use of illegal fireworks at Easter. Every year numerous burn victims are hospitalized. The most affected areas are the face, the upper extremities, and the chest, often in association with slight or severe wounds and injuries. This study presents our department's experience with incidents due to the use of fireworks during Easter festivities.

  10. Magma Mixing: Why Picrites are Not So Hot

    Science.gov (United States)

    Natland, J. H.

    2010-12-01

    Oxide gabbros or ferrogabbros are the late, low-temperature differentiates of tholeiitic magma and usually form as cumulates that can have 2-30% of the magmatic oxides, ilmenite and magnetite. They are common in the ocean crust and are likely ubiquitous wherever extensive tholeiitic magmatism has occurred, especially beneath thick lava piles such as at Hawaii, Iceland, oceanic plateaus, island arcs and ancient continental crust. When intruded by hot primitive magma including picrite, the oxide-bearing portions of these rocks are readily partially melted or assimilated into the magma and contribute to it a degree of iron and titanium enrichment that is not reflective of the mantle source of the primitive magma. The most extreme examples of such mixing are meimechites and ferropicrites, but this type of end-member mixing is even common in MORB. To the extent this process occurs, the eruptive picrite cannot be used to estimate compositions of partial melts of mantle rocks, nor their eruptive or potential temperatures, using olivine-liquid FeO-MgO backtrack procedures. Most picrites have glasses with compositions approximating those expected from low-pressure multiphase cotectic crystallization, and olivine that on average crystallized from liquids of nearly those compositions. The hallmark of such rocks is the presence of minerals other than olivine among phenocrysts (plagioclase at Iceland, clinopyroxene at many oceanic islands), Fe- and Ti-rich chromian spinel (ankaramites, ferropicrites and meimichites), and in some cases the presence of iron-rich olivine (hortonolite ~Fo65 in ferropicrites), Ti-rich kaersutitic amphibole and even apatite (meimechites); the latter two derive from late-stage, hydrous and geochemically enriched metamorphic or alkalic assimilants. This type of mixing, however, does not necessarily involve depleted and enriched mixing components. To avoid such mixing, primitive melts have to rise primarily through upper mantle rocks of near-zero melt

  11. Eruptive dynamics during magma decompression: a laboratory approach

    Science.gov (United States)

    Spina, L.; Cimarelli, C.; Scheu, B.; Wadsworth, F.; Dingwell, D. B.

    2013-12-01

    A variety of eruptive styles characterizes the activity of a given volcano. Indeed, eruptive styles can range from effusive phenomena to explosive eruptions, with related implications for hazard management. Rapid changes in eruptive style can occur during an ongoing eruption. These changes are, amongst other, related to variations in the magma ascent rate, a key parameter affecting the eruptive style. Ascent rate is in turn dependent on several factors such as the pressure in the magma chamber, the physical properties of the magma and the rate at which these properties change. According to the high number of involved parameters, laboratory decompression experiments are the best way to achieve quantitative information on the interplay of each of those factors and the related impact on the eruption style, i.e. by analyzing the flow and deformation behavior of the transparent volatile-bearing analogue fluid. We carried out decompression experiments following different decompression paths and using silicone oil as an analogue for the melt, with which we can simulate a range of melt viscosity values. For a set of experiments we added rigid particles to simulate the presence of crystals in the magma. The pure liquid or suspension was mounted into a transparent autoclave and pressurized to different final pressures. Then the sample was saturated with argon for a fixed amount of time. The decompression path consists of a slow decompression from the initial pressure to the atmospheric condition. Alternatively, samples were decompressed almost instantaneously, after established steps of slow decompression. The decompression path was monitored with pressure transducers and a high-speed video camera. Image analysis of the videos gives quantitative information on the bubble distribution with respect to depth in the liquid, pressure and time of nucleation and on their characteristics and behavior during the ongoing magma ascent. Furthermore, we also monitored the evolution of

  12. THE ECONOMIC IMPACT OF FOREIGN DEBT IN GREECE

    Directory of Open Access Journals (Sweden)

    Olga Korol

    2015-11-01

    Full Text Available The purpose. The impact of foreign debt growth on the social and economic performance of Greece was shown. The parameters of GDP, consumption, interest rates, unemployment and government spendings were analyzed. Methodology. Data obtained for 2001-2014 was used for regression analysis, vector autoregression and as well as Kalman filter. Results. A multi-faced analysis of the debt for EU-member states and Greece in particular was performed. The events and decisions of Greek authorities leading to the crisis were summarized in structural and logical scheme. The recommendations for the economic policy of Greece, based on the performed analysis were suggested. The practical applications. Establishment of all weaknesses and empirical testing of the necessary indicators in this study was the basis for the justification of measures to stabilize the economic situation in Ukraine and Greece. Value/originality. The Mandel-Fleming model and the model of balance of savings-investments was used for the first time for the theoretical interpretation of the nature of the debt crisis in Greece, that under the influence of capital inflows caused by the deterioration of the current account balance and interest rate cuts. The increase in foreign borrowings has led to an increase in the budget deficit and reduction in savings. Also for the first time performed regression-correlation analysis, in particular the Kalman filter is used to study the effect of debt on macroeconomic performance of the Greek economy.

  13. Spatial analysis of the electrical energy demand in Greece

    International Nuclear Information System (INIS)

    Tyralis, Hristos; Mamassis, Nikos; Photis, Yorgos N.

    2017-01-01

    The Electrical Energy Demand (EED) of the agricultural, commercial and industrial sector in Greece, as well as its use for domestic activities, public and municipal authorities and street lighting are analysed spatially using Geographical Information System and spatial statistical methods. The analysis is performed on data which span from 2008 to 2012 and have annual temporal resolution and spatial resolution down to the NUTS (Nomenclature of Territorial Units for Statistics) level 3. The aim is to identify spatial patterns of the EED and its transformations such as the ratios of the EED to socioeconomic variables, i.e. the population, the total area, the population density and the Gross Domestic Product (GDP). Based on the analysis, Greece is divided in five regions, each one with a different development model, i.e. Attica and Thessaloniki which are two heavily populated major poles, Thessaly and Central Greece which form a connected geographical region with important agricultural and industrial sector, the islands and some coastal areas which are characterized by an important commercial sector and the rest Greek areas. The spatial patterns can provide additional information for policy decision about the electrical energy management and better representation of the regional socioeconomic conditions. - Highlights: • We visualize spatially the Electrical Energy Demand (EED) in Greece. • We apply spatial analysis methods to the EED data. • Spatial patterns of the EED are identified. • Greece is classified in five distinct groups, based on the analysis. • The results can be used for optimal planning of the electric system.

  14. The electricity consumption and economic growth nexus: Evidence from Greece

    International Nuclear Information System (INIS)

    Polemis, Michael L.; Dagoumas, Athanasios S.

    2013-01-01

    This paper attempts to cast light into the relationship between electricity consumption and economic growth in Greece in a multivariate framework. For this purpose we used cointegration techniques and the vector error correction model in order to capture short-run and long-run dynamics over the sample period 1970–2011. The empirical results reveal that in the long-run electricity demand appears to be price inelastic and income elastic, while in the short-run the relevant elasticities are below unity. We also argue that the causal relationship between electricity consumption and economic growth in Greece is bi-directional. Our results strengthen the notion that Greece is an energy dependent country and well directed energy conservation policies could even boost economic growth. Furthermore, the implementation of renewable energy sources should provide significant benefits ensuring sufficient security of supply in the Greek energy system. This evidence can provide a new basis for discussion on the appropriate design and implementation of environmental and energy policies for Greece and other medium sized economies with similar characteristics. -- Highlights: •We examine the causality between electricity consumption and economic growth. •We used cointegration techniques to capture short-run and long-run dynamics. •The relationship between electricity consumption and GDP is bi-directional. •Residential energy switching in Greece is still limited. •The implementation of renewable energy sources should ensure security of supply

  15. Radon concentration measurements in waters in Greece and Cyprus

    International Nuclear Information System (INIS)

    Louizi, A.; Nikolopoulos, D.; Tzortzi, A.; Thanassas, D.; Serefoglou, A.; Georgiou, E.; Vogiannis, E.; Koukouliou, V.

    2004-01-01

    A total of 35 measurements in Greece and 15 in Cyprus were performed. Radon concentrations in drinking water in Greece were from (1.1±0.5) to (410±50) Bq/L. The corresponding concentrations in underground potable waters in Cyprus ranged between (0.4±0.3) Bq/L and (15±4) Bq/L. High concentrations, viz. (120±20), (320±40) and (410±50) Bq/L, were observed in three samples collected from the city of Arnea Chalkidekis in northern Greece. One water sample from Lesvos Island (north-eastern part of Greece) exhibited a radon concentration of (140±20) Bq/L. Six samples of hot spring water from the city of Loutraki (Attica prefecture), characterized as 'medicinal drinking water', contained concentrations of radon between (220±10) and (340±20) Bq/L. Radon concentrations in potable and non-potable underground water in Greece and Cyprus ranged between (0.4±0.3) and (15±4) Bq/L, whereas in surface water the range was from (2.7±0.8) to (24±6) Bq/L. (P.A.)

  16. Magma viscosity estimation based on analysis of erupted products. Potential assessment for large-scale pyroclastic eruptions

    International Nuclear Information System (INIS)

    Takeuchi, Shingo

    2010-01-01

    After the formulation of guidelines for volcanic hazards in site evaluation for nuclear installations (e.g. JEAG4625-2009), it is required to establish appropriate methods to assess potential of large-scale pyroclastic eruptions at long-dormant volcanoes, which is one of the most hazardous volcanic phenomena on the safety of the installations. In considering the volcanic dormancy, magma eruptability is an important concept. The magma eruptability is dominantly controlled by magma viscosity, which can be estimated from petrological analysis of erupted materials. Therefore, viscosity estimation of magmas erupted in past eruptions should provide important information to assess future activities at hazardous volcanoes. In order to show the importance of magma viscosity in the concept of magma eruptability, this report overviews dike propagation processes from a magma chamber and nature of magma viscosity. Magma viscosity at pre-eruptive conditions of magma chambers were compiled based on previous petrological studies on past eruptions in Japan. There are only 16 examples of eruptions at 9 volcanoes satisfying data requirement for magma viscosity estimation. Estimated magma viscosities range from 10 2 to 10 7 Pa·s for basaltic to rhyolitic magmas. Most of examples fall below dike propagation limit of magma viscosity (ca. 10 6 Pa·s) estimated based on a dike propagation model. Highly viscous magmas (ca. 10 7 Pa·s) than the dike propagation limit are considered to lose eruptability which is the ability to form dikes and initiate eruptions. However, in some cases, small precursory eruptions of less viscous magmas commonly occurred just before climactic eruptions of the highly viscous magmas, suggesting that the precursory dike propagation by the less viscous magmas induced the following eruptions of highly viscous magmas (ca. 10 7 Pa·s). (author)

  17. Characteristics of low-enthalpy geothermal applications in Greece

    International Nuclear Information System (INIS)

    Andritsos, N.; Dalabakis, P.; Karydakis, G.; Kolios, N.; Fytikas, M.

    2011-01-01

    The paper offers a brief overview of the current direct geothermal uses in Greece and discusses their characteristics, with emphasis to the economical and technical problems encountered. Greece holds a prominent place in Europe regarding the existence of promising geothermal resources (both high and low-enthalpy), which can be economically exploited. Currently, no geothermal electricity is produced in Greece. The installed capacity of direct uses at the end of 2009 is estimated at about 155 MW t , exhibiting an increase of more than 100% compared to the figures reported at the World Geothermal Congress 2005. The main uses, in decreasing share, are geothermal heat pumps, swimming and balneology, greenhouse heating and soil warming. Earth-coupled and groundwater (or seawater) heat pumps have shown a drastic expansion during the past 2-3 years, mainly due to high oil prices two years ago and easing of the license requirements for drilling shallow wells. (author)

  18. An annotated checklist of earthworms of Greece (Clitellata: Megadrili).

    Science.gov (United States)

    Szederjesi, Tímea; Vavoulidou, Evangelia; Chalkia, Christina; Dányi, László; Csuzdi, Csaba

    2017-05-26

    The earthworm fauna of Greece is reviewed. According to the up-to-date checklist, the earthworm fauna of Greece consists of 67 species and subspecies, of which 59 taxa belong to the family Lumbricidae, three to Megascolecidae, two to Acanthodrilidae and to Ocnerodrilidae and one taxon to the family Criodrilidae. Three species are recorded for the first time from the country: Allolobophora kosowensis kosowensis Karaman, 1968, Amynthas gracilis (Kinberg, 1867) and Eukerria saltensis (Beddard, 1895). Eisenia spelaea var. athenica Černosvitov, 1938 is proposed to be a synonym of Aporrectodea rosea (Savigny, 1826). The earthworm fauna of Greece is characterized by a large number of strict endemic species belonging to the family Lumbricidae (9 taxa), together with the occurrence of another 10 Balkanic endemic species.

  19. Environmental tobacco smoke in hospitality venues in Greece.

    Science.gov (United States)

    Vardavas, Constantine I; Kondilis, Barbara; Travers, Mark J; Petsetaki, Elisabeth; Tountas, Yiannis; Kafatos, Anthony G

    2007-10-23

    Exposure to environmental tobacco smoke is a major threat to public health. Greece, having the highest smoking prevalence in the European Union is seriously affected by passive smoking. The purpose of this study was to measure environmental tobacco smoke (ETS) exposure in the non smoking areas of hospitality venues and offices in Greece and to compare the levels of exposure to levels in the US, UK and Ireland before and after the implementation of a smoking ban. Experimental measurements of particulate matter 2.5 microm (PM2.5), performed during a cross sectional study of 49 hospitality venues and offices in Athens and Crete, Greece during February - March 2006. Levels of ETS ranged from 19 microg/m3 to 612 microg/m3, differing according to the place of measurement. The average exposure in hospitality venues was 268 microg/m3 with ETS levels found to be highest in restaurants with a mean value of 298 microg/m3 followed by bars and cafes with 271 microg/m3. ETS levels were 76% lower in venues in which smoking was not observed compared to all other venues (p hospitality venues while levels in Ireland with a total smoking ban are 89% lower and smoke-free communities in the US are 91 - 96% lower than levels in Greece. Designated non-smoking areas of hospitality venues in Greece are significantly more polluted with ETS than outdoor air and similar venues in Europe and the United States. The implementation of a total indoor smoking ban in hospitality venues has been shown to have a positive effect on workers and patrons' health. The necessity of such legislation in Greece is thus warranted.

  20. Radioactive equilibria and disequilibria of U-series nuclides in erupting magmas from Izu arc volcanoes

    International Nuclear Information System (INIS)

    Sato, Jun; Kurihara, Yuichi; Takahashi, Masaomi

    2009-01-01

    Radioactive disequilibria among U-series nuclides are observed in the magmas from volcanoes in the world. Basaltic products from Izu arc volcanoes, including Izu-Oshima and Fuji volcanoes, show 230 Th 238 U and 226 Ra> 230 Th disequilibria, indicating that the addition of U-and Ra-rich fluid from the subducting slab to the mantle wedge at the magma genesis. The disequilibria of 226 Ra> 230 Th in the erupting magmas suggest that the timescale from magma genesis to the eruption may be less than 8000 years. (author)

  1. Geology and radiometry of West Macedonia (Greece)

    International Nuclear Information System (INIS)

    Minatidis, Demetrios G.

    1984-10-01

    Car borne scintillometry survey in W. Macedonia (Greece) showed that the granitic rocks of the area, the zone centered on the Tertiary volcanic rocks of Almopia zone and a large part of adjacent sediments constitute the most promising geological formations for further uranium exploration. Some Tertiary volcanic rocks in the general area centered on the Aegean plate are associated with uranium mineralization and high radioactivity. An attempt has been made to evaluate young Alpine volcanic rocks from uranium exploration point of view on a regional scale by using arithmetic mean radioactivity data from the car borne survey coverage of W. Macedonia, as well as other geological and geochemical data from numerous similar volcanic rocks of the area and other neighbouring areas. In connection with this further exploration of the Tertiary volcanic rocks of W. Macedonia is expected to reveal new uranium deposits in the area. Horizontal or gently dipping sedimentary rocks adjacent to the above mentioned volcanics have a statistical radioactivity higher than that in normal sediments, a fact that may give evidence of the existence or uranium mineralization in deeper horizons in these sediments. To make a comparison with this the existence of 134 ppm of leachable U in sediments of W. Crete Island, 20 to 30 meters below the surface, is reported where the overlying sediments exhibit also a radioactivity higher than in normal sediments. Some structural contacts, in particular the contact between the granite of Florina and the limestones of Krystallopigi (west of Florina), have locally a very high radioactivity. Also an open fault in the Achlada-Papadia area (Florina) exhibits locally a high radioactivity and a high U content. All the above mentioned geological formations are, therefore, proposed for further U exploration. (author)

  2. Development of a Coastal Inventory in Greece

    Science.gov (United States)

    Karditsa, Aikaterini; Poulos, Serafim; Velegrakis, Adonis; Ghionis, George; Petrakis, Stelios; Alexandrakis, George; Andreadis, Olympos; Monioudi, Isavella

    2015-04-01

    Greek coastline that accounts more than 16.000 km hosts hundreds of beaches, which constitute a great touristic destination. However, no gathered information exists relative to its qualitative and quantitative characteristics (e.g. physicogeographical characteristics, artificial structures, nearby land use). Therefore, the development of a coastal database that would successfully concentrate all relative data, in the form of a National Inventory, could be a valuable tool for the management and the sustainable use and exploitation of beaches and the coastal zone. This work presents an example of the development of a beach inventory in the case of the beach zones of Heraklion and Lassithi counties in the Island of Crete, which is one of the most touristic areas in Greece. Data were initially abstracted from satellite images and combined with in situ observations carried out along 98 beaches with shoreline length >100 m. The collected data included geomorphological, topographic and bathymetric mapping, sediment sampling from the subaerial and underwater part and recording of artificial structures. The initial mapping showed that beaches represent only the 18%, with 74% of the total coastline to be rocky while 8% of the coastline host some kind of artificial intervention. The combination of satellite and in situ mapping led to the development of a coastal geomorphological map. Beach widths were found to be limited with the majority of beaches (59%) to have maximum widths less than 25 m, 35% to range between 25 and 50m and about 6% with maximum widths >50m. Concerning beach length, the threshold of 1000 m is overcome only by the 46% of the beaches. Beaches with very smooth slopes (Entrepreneurship" co-funded by the European Regional Development Fund (ERDF) and the Ministry of Education and Relegious Affairs.

  3. Epidemiology of Dermatophytoses in Crete, Greece.

    Science.gov (United States)

    Maraki, Sofia; Mavromanolaki, Viktoria Eirini

    2016-01-01

    Dermatophytoses are among the most frequently diagnosed skin infections worldwide. However, the distribution of pathogenic species and the predominating anatomical sites of infection vary with geographical location and change over time. The aim of this study was to determine the epidemiological and aetiological factors of dermatophytoses in Crete, Greece over the last 5-year period (2011-2015) and their incidence in relation to the gender and the age of the patients. We compared our findings with those previously reported from the same area and from other parts of the world. A total of 2,910 clinical specimens (skin scrapings, nail clippings, and hair specimens) obtained from 2,751 patients with signs of dermatomycoses were examined using direct microscopy and culture. Overall, 294 specimens (10.1%) were proved mycologically positive for dermatophytes. The age of the patients ranged from 2 to 86 years (mean age, 37 years). Tinea corporis was the predominant clinical type of infection, followed by tinea unguium, tinea pedis, tinea capitis, tinea faciei, tinea cruris and tinea manuum. Among dermatophytes, eight species were isolated: Microsporum canis (35.8%), Trichophyton rubrum (35.1%), Trichophyton mentagrophytes (23.3%), Epidermophyton floccosum (2.5%), Microsporum gypseum (1.8%), Trichophyton violaceum (0.7%), Trichophyton verrucosum (0.4%), and Trichophyton tonsurans (0.4%). In our area, the most common dermatophyte was M. canis followed by T. rubrum. Increased migration, mass tourism, and climate changes will contribute to further changes in the epidemiology of dermatophytoses in our area. Continuing studies are necessary for determining the new epidemiological trends and to implement the appropriate control measures.

  4. The Miocene carnivore assemblage of Greece

    Directory of Open Access Journals (Sweden)

    Koufos, G. D.

    2011-12-01

    Full Text Available The Miocene carnivore assemblage of Greece includes a great number of taxa, described in numerous articles since the first decades of the 19th Century. The present article is a revision of all these taxa, providing information about their history, localities, age, as well as their stratigraphic distribution and palaeoenvironment. The Early/Middle Miocene carnivore record of Greece is poor as the available fossiliferous sites and material are rare. However, the Late Miocene one is quite rich, including numerous taxa. The Miocene localities with carnivores and their age are given in a stratigraphic table covering the European Mammal zones from MN 4 to MN 13. The type locality, holotype, and some historical and morphological remarks are given for each taxon. Several carnivore taxa were erected from Greek material and new photos of their holotypes are given. The stratigraphic distribution of the Greek carnivore taxa indicates that they are covering the time span from ~19.0-5.3Ma. The majority of the Miocene taxa (Adcrocuta, Hyaenictitherium, Plioviverrops, Protictitherium, Ictitherium, Indarctos, Dinocrocuta, Promephitis disappeared at the end of Miocene. The composition of the Early/Middle Miocene carnivore assemblage of Greece includes mainly viverrids (Lophocyon, Euboictis, while the hyaenids, percrocutids, felids and mustelids are very few. On the contrary the Late Miocene assemblage is richer, including more subfamilies and species; the hyaenids and mustelids dominate, while the viverrids are absent. The Late Miocene carnivore guild structure is similar to that of the modern Serengeti, indicating a relatively open, savannah-like environment.

    La asociación de carnívoros miocenos de Grecia incluye un gran número de taxones, descritos en numerosos artículos desde las primeras décadas del siglo XIX. El presente artículo supone un esfuerzo de síntesis de todos estos taxones, suministrando información sobre su

  5. The structure of residential energy demand in Greece

    International Nuclear Information System (INIS)

    Rapanos, Vassilis T.; Polemis, Michael L.

    2006-01-01

    This paper attempts to shed light on the determinants of residential energy demand in Greece, and to compare it with some other OECD countries. From the estimates of the short-run and long-run elasticities of energy demand for the period 1965-1999, we find that residential energy demand appears to be price inelastic. Also, we do not find evidence of a structural change probably because of the low efficiency of the energy sector. We find, however, that the magnitude of the income elasticity varies substantially between Greece and other OECD countries

  6. Aid for the victims of the forest fires in Greece

    CERN Multimedia

    2007-01-01

    To support the victims of the fires which devastated the Peloponnese at the end of August, the Permanent Mission of Greece in Geneva has informed us that the Greek government has opened an account into which donations may be paid. The funds collected will be used to assist the many victims of these fires. Bank of Greece Account name: Logariasmos Arogis Pyropathon (Hellenic Republic) (account reserved for aid for the victims of the forest fires) SWIFT : BNGRGRAA IBAN : GR 98 0100 0230 0000 0234 1103 053

  7. Long-Term Volumetric Eruption Rates and Magma Budgets

    Energy Technology Data Exchange (ETDEWEB)

    Scott M. White Dept. Geological Sciences University of South Carolina Columbia, SC 29208; Joy A. Crisp Jet Propulsion Laboratory, California Institute of Technology Pasadena, CA 91109; Frank J. Spera Dept. Earth Science University of California, Santa Barbara Santa Barbara, CA 93106

    2005-01-01

    A global compilation of 170 time-averaged volumetric volcanic output rates (Qe) is evaluated in terms of composition and petrotectonic setting to advance the understanding of long-term rates of magma generation and eruption on Earth. Repose periods between successive eruptions at a given site and intrusive:extrusive ratios were compiled for selected volcanic centers where long-term (>104 years) data were available. More silicic compositions, rhyolites and andesites, have a more limited range of eruption rates than basalts. Even when high Qe values contributed by flood basalts (9 ± 2 Å~ 10-1 km3/yr) are removed, there is a trend in decreasing average Qe with lava composition from basaltic eruptions (2.6 ± 1.0 Å~ 10-2 km3/yr) to andesites (2.3 ± 0.8 Å~ 10-3 km3/yr) and rhyolites (4.0 ± 1.4 Å~ 10-3 km3/yr). This trend is also seen in the difference between oceanic and continental settings, as eruptions on oceanic crust tend to be predominately basaltic. All of the volcanoes occurring in oceanic settings fail to have statistically different mean Qe and have an overall average of 2.8 ± 0.4 Å~ 10-2 km3/yr, excluding flood basalts. Likewise, all of the volcanoes on continental crust also fail to have statistically different mean Qe and have an overall average of 4.4 ± 0.8 Å~ 10-3 km3/yr. Flood basalts also form a distinctive class with an average Qe nearly two orders of magnitude higher than any other class. However, we have found no systematic evidence linking increased intrusive:extrusive ratios with lower volcanic rates. A simple heat balance analysis suggests that the preponderance of volcanic systems must be open magmatic systems with respect to heat and matter transport in order to maintain eruptible magma at shallow depth throughout the observed lifetime of the volcano. The empirical upper limit of Å`10-2 km3/yr for magma eruption rate in systems with relatively high intrusive:extrusive ratios may be a consequence of the fundamental parameters

  8. Grain to outcrop-scale frozen moments of dynamic magma mixing in the syenite magma chamber, Yelagiri Alkaline Complex, South India

    Directory of Open Access Journals (Sweden)

    M.L. Renjith

    2014-11-01

    Full Text Available Magma mixing process is unusual in the petrogenesis of felsic rocks associated with alkaline complex worldwide. Here we present a rare example of magma mixing in syenite from the Yelagiri Alkaline Complex, South India. Yelagiri syenite is a reversely zoned massif with shoshonitic (Na2O + K2O=5–10 wt.%, Na2O/K2O = 0.5–2, TiO2 <0.7 wt.% and metaluminous character. Systematic modal variation of plagioclase (An11–16 Ab82–88, K-feldspar (Or27–95 Ab5–61, diopside (En34–40Fs11–18Wo46–49, biotite, and Ca-amphibole (edenite build up three syenite facies within it and imply the role of in-situ fractional crystallization (FC. Evidences such as (1 disequilibrium micro-textures in feldspars, (2 microgranular mafic enclaves (MME and (3 synplutonic dykes signify mixing of shoshonitic mafic magma (MgO = 4–5 wt.%, SiO2 = 54–59 wt.%, K2O/Na2O = 0.4–0.9 with syenite. Molecular-scale mixing of mafic magma resulted disequilibrium growth of feldspars in syenite. Physical entity of mafic magma preserved as MME due to high thermal-rheological contrast with syenite magma show various hybridization through chemical exchange, mechanical dilution enhanced by chaotic advection and phenocryst migration. In synplutonic dykes, disaggregation and mixing of mafic magma was confined within the conduit of injection. Major-oxides mass balance test quantified that approximately 0.6 portions of mafic magma had interacted with most evolved syenite magma and generated most hybridized MME and dyke samples. It is unique that all the rock types (syenite, MME and synplutonic dykes share similar shoshonitic and metaluminous character; mineral chemistry, REE content, coherent geochemical variation in Harker diagram suggest that mixing of magma between similar composition. Outcrop-scale features of crystal accumulation and flow fabrics also significant along with MME and synplutonic dykes in syenite suggesting that Yelagiri syenite magma chamber had evolved

  9. Why has Greece not defaulted, yet? - A macroeconomic and historical institutionalist perspective on why Greece has not followed in Argentine footsteps and defaulted.

    OpenAIRE

    Afranie, Lenny Matthew; Rauff Hansen, Tina; Dalgaard Steffensen, Ida

    2012-01-01

    This projects sets out to explore the reasons why Greece, in the light of the current sovereign debt crisis, has not done as Argentina did in 2001 and defaulted. It uses a historical institutionalist framework, drawing on path dependency and critical junctures in the analysis of 1. how the European Union (EU) imposes restrictions on Greece, and 2. how Greece's and Argentina's situations correspond and differ. The project concludes that the main difference lies in the restrictions imposed on G...

  10. Magma interaction in the root of an arc batholith

    Science.gov (United States)

    Chapman, T.; Robbins, V.; Clarke, G. L.; Daczko, N. R.; Piazolo, S.

    2016-12-01

    Fiordland, New Zealand, preserves extensive Cretaceous arc plutons, emplaced into parts of the Delamerian/Ross Orogen. Dioritic to gabbroic material emplaced at mid to lower crustal levels are exposed in the Malaspina Pluton (c. 1.2 GPa) and the Breaksea Orthogneiss (c. 1.8 GPa). Distinct magmatic pulses can be mapped in both of these plutons consistent with cycles of melt advection. Relationships are consistent with predictions from lower crustal processing zones (MASH and hot zones) considered important in the formation of Cordilleran margins. Metamorphic garnet growth is enhanced along magmatic contacts, such as where hornblende gabbronorite is cut by garnet-clinopyroxene-bearing diorite. Such features are consistent with cycles of incremental emplacement, younger magma having induced localised garnet granulite metamorphism in wall rock of older material. Temperature estimates and microstructures preserved in garnet granulite are consistent with sub-solidus, water-poor conditions in both the Malaspina and Breaksea Orthogneiss. The extent and conditions of the metamorphism implies conditions and duration was incapable of partially melting older wall rock material. The nature of interactions in intermediate to basic compositions are assessed in terms of magma genesis in the Cretaceous batholith. Most of the upper crustal felsic I-type magmatism along the margin being controlled by high-pressure garnet-clinopyroxene fractionation.

  11. Boron isotope fractionation in magma via crustal carbonate dissolution.

    Science.gov (United States)

    Deegan, Frances M; Troll, Valentin R; Whitehouse, Martin J; Jolis, Ester M; Freda, Carmela

    2016-08-04

    Carbon dioxide released by arc volcanoes is widely considered to originate from the mantle and from subducted sediments. Fluids released from upper arc carbonates, however, have recently been proposed to help modulate arc CO2 fluxes. Here we use boron as a tracer, which substitutes for carbon in limestone, to further investigate crustal carbonate degassing in volcanic arcs. We performed laboratory experiments replicating limestone assimilation into magma at crustal pressure-temperature conditions and analysed boron isotope ratios in the resulting experimental glasses. Limestone dissolution and assimilation generates CaO-enriched glass near the reaction site and a CO2-dominated vapour phase. The CaO-rich glasses have extremely low δ(11)B values down to -41.5‰, reflecting preferential partitioning of (10)B into the assimilating melt. Loss of (11)B from the reaction site occurs via the CO2 vapour phase generated during carbonate dissolution, which transports (11)B away from the reaction site as a boron-rich fluid phase. Our results demonstrate the efficacy of boron isotope fractionation during crustal carbonate assimilation and suggest that low δ(11)B melt values in arc magmas could flag shallow-level additions to the subduction cycle.

  12. MAGMA-SMC: The Molecular Cloud Survey of the SMC

    Science.gov (United States)

    Muller, Erik; Wong, Tony; Hughes, Annie; Ott, Jürgen; Pineda, Jorge L.; MAGMA Collaboration

    2013-03-01

    We present a brief summary and description of the upcoming 12CO(1-0) Magellanic Mopra Assesment (MAGMA) SMC survey data release. The MAGMA-SMC survey has sampled 100% of the known CO in the SMC (at ˜33″ resolution; 12 pc at D = 60 kpc). Having explored 522 × 103 square parsecs throughout the SMC with 69 5' × 5' fields, to a sensitivity of ˜150 mK, we apply the cloudprops (Rosolowsky & Leroy 2006) cloud-search algorithm optimized for low S/N data, to detect more than 30 CO clouds with virial masses between 103-104 M⊙, mean radii ˜5 pc and 0.3-0.9 km s-1 velocity width. Typical brightness temperatures are ˜1 K T mb . All detected molecular regions are associated with at least one 24 μm compact emission source. Smoothing rarely increases the total detected CO flux, implying the CO emission is typically confined to small spatial scales. As recent dust maps of the SMC imply extended H2 mass, the apparent compact nature of the CO population indicates some departures from the canonical Galactic X CO-factor in the low-metallicity and relatively un-evolved ISM of the SMC.

  13. Boron isotope fractionation in magma via crustal carbonate dissolution

    Science.gov (United States)

    Deegan, Frances M.; Troll, Valentin R.; Whitehouse, Martin J.; Jolis, Ester M.; Freda, Carmela

    2016-08-01

    Carbon dioxide released by arc volcanoes is widely considered to originate from the mantle and from subducted sediments. Fluids released from upper arc carbonates, however, have recently been proposed to help modulate arc CO2 fluxes. Here we use boron as a tracer, which substitutes for carbon in limestone, to further investigate crustal carbonate degassing in volcanic arcs. We performed laboratory experiments replicating limestone assimilation into magma at crustal pressure-temperature conditions and analysed boron isotope ratios in the resulting experimental glasses. Limestone dissolution and assimilation generates CaO-enriched glass near the reaction site and a CO2-dominated vapour phase. The CaO-rich glasses have extremely low δ11B values down to -41.5‰, reflecting preferential partitioning of 10B into the assimilating melt. Loss of 11B from the reaction site occurs via the CO2 vapour phase generated during carbonate dissolution, which transports 11B away from the reaction site as a boron-rich fluid phase. Our results demonstrate the efficacy of boron isotope fractionation during crustal carbonate assimilation and suggest that low δ11B melt values in arc magmas could flag shallow-level additions to the subduction cycle.

  14. Advancing dynamic and thermodynamic modelling of magma oceans

    Science.gov (United States)

    Bower, Dan; Wolf, Aaron; Sanan, Patrick; Tackley, Paul

    2017-04-01

    The techniques for modelling low melt-fraction dynamics in planetary interiors are well-established by supplementing the Stokes equations with Darcy's Law. But modelling high-melt fraction phenomena, relevant to the earliest phase of magma ocean cooling, necessitates parameterisations to capture the dynamics of turbulent flow that are otherwise unresolvable in numerical models. Furthermore, it requires knowledge about the material properties of both solid and melt mantle phases, the latter of which are poorly described by typical equations of state. To address these challenges, we present (1) a new interior evolution model that, in a single formulation, captures both solid and melt dynamics and hence charts the complete cooling trajectory of a planetary mantle, and (2) a physical and intuitive extension of a "Hard Sphere" liquid equation of state (EOS) to describe silicate melt properties for the pressure-temperature (P-T) range of Earth's mantle. Together, these two advancements provide a comprehensive and versatile modelling framework for probing the far-reaching consequences of magma ocean cooling and crystallisation for Earth and other rocky planets. The interior evolution model accounts for heat transfer by conduction, convection, latent heat, and gravitational separation. It uses the finite volume method to ensure energy conservation at each time-step and accesses advanced time integration algorithms by interfacing with PETSc. This ensures it accurately and efficiently computes the dynamics throughout the magma ocean, including within the ultra-thin thermal boundary layers (modelling capabilities. The thermodynamics of mantle melting are represented using a pseudo-one-component model, which retains the simplicity of a standard one-component model while introducing a finite temperature interval for melting (important for multi-component systems). Our new high P-T liquid EOS accurately captures the energetics and physical properties of the partially molten

  15. School Psychology in Greece: A System of Change.

    Science.gov (United States)

    Theodore, Lea A.; Bray, Melissa A.; Kehle, Thomas J.; Dioguardi, Richard J.

    2002-01-01

    Discusses origin of school psychology in Greece which emerged with services for mentally disabled in 1937. Explains how laws were instituted with the growing demand for educational services for students with social and emotional needs. Includes discussions on diverse roles of school psychologists, present status of special education, and influence…

  16. The History of Teaching Quantum Mechanics in Greece

    Science.gov (United States)

    Tampakis, Constantin; Skordoulis, Constantin

    2007-01-01

    In this work, our goal is to examine the attitude of the Greek scientific community towards Quantum Mechanics and establish the history of teaching of this theory in Greece. We have examined Physics textbooks written by professors of the University of Athens, as well as records of public speeches, university yearbooks from 1923 to 1970, articles…

  17. Plato and Play: Taking Education Seriously in Ancient Greece

    Science.gov (United States)

    D'Angour, Armand

    2013-01-01

    In this article, the author outlines Plato's notions of play in ancient Greek culture and shows how the philosopher's views on play can be best appreciated against the background of shifting meanings and evaluations of play in classical Greece. Play--in various forms such as word play, ritual, and music--proved central to the development of…

  18. Knowledge and attitude towards smoking of pregnant women in Greece

    Directory of Open Access Journals (Sweden)

    Athina Diamanti

    2017-05-01

    Having not being informed and helped adequately, a significant percentage of pregnant women continued to smoke throughout their pregnancy. The failure in imposing the clean indoor air law in public places in Greece has also contributed to the increased passive smoking exposure.

  19. Energy policies of IEA countries: Greece 2006 review

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2006-07-01

    The report provides an in-depth assessment of the energy policies of Greece and makes recommendations on future policy. Lignite, the main domestic fossil fuel resource of Greece, will continue to play a major role in the country's fuel mix in the future. The government and the regulator should consider introducing more advanced generation technology through retrofits or into new lignite power stations. It may be an option to construct a power station using lignite from unopened deposits, for the exploitation of which a new bidding procedure is currently open. Since the previous review in 2002, Greece has also made significant progress in setting the course for reforming its electricity and gas markets. Energy diversification has improved, with natural gas becoming increasingly important. Significant challenges, however, remain. The market power of the incumbent energy suppliers continues to restrict competition. Unless this issue is addressed, a fully competitive energy market is inconceivable. Of particular concern are the arrangements for ownership of the electricity and gas transmission systems. The review suggests various options to overcome these obstacles. Greece is getting close to missing its target set under the Kyoto Protocol and the government is urged to closely monitor the situation. The supply and demand situation is addressed.. Recommendations are made on how to reduce the country's high oil dependence and advice offered to policy makers on steps to develop a long-term energy efficiency policy with measurable targets that tackle the demand side of the Greek energy sector.

  20. Pedagogical Beliefs and Attitudes of Computer Science Teachers in Greece

    Science.gov (United States)

    Fessakis, Georgios; Karakiza, Tsampika

    2011-01-01

    Pedagogical beliefs and attitudes significantly determine the professional skills and practice of teachers. Many professional development programs for teachers aim to the elaboration of the pedagogical knowledge in order to improve teaching quality. This paper presents the study of pedagogical beliefs of computer science teachers in Greece. The…

  1. Notions of "Rhetoric as Epistemic" in Ancient Greece.

    Science.gov (United States)

    Benoit, William L.

    The notion that rhetoric (and to a lesser extent, argument) is epistemic is an increasingly popular one today, although it can be traced to ancient Greece. The notion holds that rhetoric, or the art of persuasion, creates and shapes knowledge. Two ancient authors--Aristophanes and Plato--provide evidence that others had notions of rhetoric as…

  2. Duality of roles and corporate governance in Greece

    Directory of Open Access Journals (Sweden)

    Themistokles Lazarides

    2009-01-01

    Full Text Available Duality of the role of President of the Board of Directors (BoD and CEO has been regarded as a good practice of corporate governance. These two roles are the ones with the most power an authority within the corporation. The paper depicts the formulating factors of duality of roles in Greece. Literature has linked duality with performance, organizational stability, ownership concentration and balance of power and control within the firm. The paper, using a Probit regression analysis, examines whether these relationships are valid in Greece. Statistical – econometric analysis has shown that financial performance is not related with concentration of power and control. The same conclusion is can be drawn for ownership concentration. There is a trend of change but this trend hasn’t the same dynamic or driving factors as the ones that are reported by Kirkbride and Letza (2002 and Muth and Donaldson (1998. The hypothesis posed by Heracleous (2001 and Baliga, 6oyer and Rao (1996 are more likely to be true in the case of Greece. Overall, duality in Greece is affected by the historical development of the firm, its organizational scheme and even more by the balance of power and control within the firm.

  3. Energy performance of buildings—EPBD in Greece

    International Nuclear Information System (INIS)

    Dascalaki, E.G.; Balaras, C.A.; Gaglia, A.G.; Droutsa, K.G.; Kontoyiannidis, S.

    2012-01-01

    Transposition of the European Directive on the energy performance of buildings (EPBD) in Greece was enacted in 2008 by a national law. A follow-up regulation on the energy performance in the building sector—KENAK released in 2010, outlines the overall approach in accordance to European standards and EPBD mandates. All necessary technical specifications and detailed information for the implementation of KENAK are included in four new technical guidelines prepared in 2010, which are supported by an official national software. Issues related to the energy experts are handled by presidential decrees published in 2010; over 5400 temporary energy inspectors are already in place, while permanent accreditation is in progress. Energy performance design study of new buildings for obtaining a building permit is in place since October 2010 and issuing energy performance certificates as of January 2011. This paper presents an overview of the development and current EPBD stage of implementation in Greece, along with a first assessment of the lessons learned and experiences gained. - Highlights: ► EPBD transposition in Greece is a reality. ► KENAK is the main legislative instrument for improving building energy efficiency in Greece. ► Four new technical guidelines have been published to support KENAK. ► A national software was also prepared to support implementation of KENAK. ► Temporary accreditation of 5300 energy inspectors. ► Over 20,000 energy performance certificates issued in the first five months of implementation.

  4. A Report on Educational Developments in 1975-1976. Greece.

    Science.gov (United States)

    Ministry of National Education and Religion, Athens (Greece).

    Examining the educational system of Greece, this publication discusses the reorientation of policy, organization, and curriculum after overthrow of the military regime in July 1974. In accordance with the broader democratic principles set forth in the Greek Constitution of 1975, education is now compulsory for six years, free to everyone on all…

  5. Attitude of elderly patients towards cardiopulmonary resuscitation in Greece.

    Science.gov (United States)

    Chliara, Daphne; Chalkias, Athanasios; Horopanitis, Evaggelos E; Papadimitriou, Lila; Xanthos, Theodoros

    2014-10-01

    Although researchers in several countries have investigated patients' points of view regarding cardiopulmonary resuscitation, there has been no research investigating this issue in Greece. The present study aimed at identifying the attitude of older Greek patients regarding cardiopulmonary resuscitation. One basic questionnaire consisting of 34 questions was used in order to identify patients' opinions regarding cardiopulmonary resuscitation in five different hospitals from June to November 2011. In total, 300 questionnaires were collected. Although patients' knowledge regarding cardiopulmonary resuscitation was poor, most of them would like to be resuscitated in case they suffered an in-hospital cardiac arrest. Also, they believe that they should have the right to accept or refuse treatment. However, the legal and sociocultural norms in Greece do not support patients' choice for the decision to refuse resuscitation. The influence of several factors, such as their general health status or the underlying pathology, could lead patients to give a "do not attempt resuscitation" order. The attitudes of older Greek patients regarding resuscitation are not different from others', whereas the legal and sociocultural norms in Greece do not support patient choice in end-of-life decisions, namely the decision to refuse resuscitation. We advocate the introduction of advanced directives, as well as the establishment and implementation of specific legislation regarding the ethics of resuscitation in Greece. © 2013 Japan Geriatrics Society.

  6. Paronychia manfrediana (Caryophyllaceae), a new species from northeast Greece

    DEFF Research Database (Denmark)

    Tan, Kit; Strid, Arne

    2008-01-01

    Paronychia manfrediana (Caryophyllaceae) is decribed as a species new to science based on material collected near the Turkish border in northeastern Greece; it is illustrated by a photograph. Although belonging to Paronychia sect. Heterosepalae it bears a strong resemblance to P.macedonica (Paron...

  7. Literacy in Ancient Greece: The Evidence from History and Archaeology.

    Science.gov (United States)

    Hollis, Karyn

    In examining the nature of literacy in ancient Athens, this paper reviews the work of key modern scholars and their positions in the debates concerning the development of literacy in Greece, the oral culture preceeding this, and the technology that enabled it to occur. Following an introduction surveying the viewpoints of Rhys Carpenter, L. H.…

  8. Isolation of Dobrava Virus from Apodemus flavicollis in Greece

    Science.gov (United States)

    Papa, Anna; Nemirov, Kirill; Henttonen, Heikki; Niemimaa, Jukka; Antoniadis, Antonis; Vaheri, Antti; Plyusnin, Alexander; Vapalahti, Olli

    2001-01-01

    Dobrava virus (DOBV) carried by Apodemus flavicollis is the causative agent of severe hemorrhagic fever with renal syndrome (HFRS). DOBV was isolated from an A. flavicollis mouse trapped in northeastern Greece. This is the third DOBV cell culture isolate in the world, clustering together with other Greek DOBV sequences from HFRS patients and rodents. PMID:11376073

  9. Vocational Training in the Textiles and Clothing Industries in Greece.

    Science.gov (United States)

    Drimousis, I.; Zisimopoulos, A.

    This document examines the circumstances under which vocational training in Greece is provided for jobs in the textile and clothing industries. Its objective is to identify guidelines for vocational training for a skilled work force at regional and national levels and to contribute to job mobility between industries. Statistical data,…

  10. Gold and gold working in Late Bronze Age Northern Greece

    Science.gov (United States)

    Vavelidis, M.; Andreou, S.

    2008-04-01

    Numerous objects of gold displaying an impressive variety of types and manufacturing techniques are known from the Late Bronze Age (LBA) contexts of Mycenaean Greece, but very little is known about the origin and processing of gold during the second millennium b.c. Ancient literature and recent research indicate that northern Greece is probably the richest gold-bearing region in Greece, and yet, very little evidence exists regarding the exploitation of its deposits and the production as well as use of gold in the area during prehistory. The unusual find of a group of small stone crucibles at the prehistoric settlement of Thessaloniki Toumba, one with visible traces of gold melting, proves local production and offers a rare opportunity to examine the process of on-site gold working. Furthermore, the comparison of the chemical composition of prehistoric artefacts from two settlements with those of gold deposits in their immediate areas supports the local extraction of gold and opens up the prospect for some of the Mycenaean gold to have originated in northern Greece. The scarcity of gold items in northern Greek LBA contexts may not represent the actual amount of gold produced and consumed, but could be a result of the local social attitudes towards the circulation and deposition of artefacts from precious metals.

  11. Gender Equality in Employment Utilizing Female Social Entrepreneurship in Greece

    NARCIS (Netherlands)

    Argyrou, A.|info:eu-repo/dai/nl/407629459; Charitakis, Stelios

    2017-01-01

    Greek women are severely affected by the on-going financial crisis. They deal with the effects of unemployment and they experience a marginalised position in the Greek labour market due to deep-rooted stereotypes which result in inequality of employment opportunities. Greece has ratified the CEDAW

  12. The first description of snow algae on Mount Olympus (Greece).

    Czech Academy of Sciences Publication Activity Database

    Cepák, Vladislav; Kvíderová, Jana; Lukavský, Jaromír

    2016-01-01

    Roč. 103, 3-4 (2016), s. 457-473 ISSN 0029-5035 R&D Projects: GA TA ČR TE01020080 Institutional support: RVO:67985939 Keywords : cryoseston * Olymp Mt. * Greece Subject RIV: EF - Botanics Impact factor: 0.941, year: 2016

  13. Scanning the Business External Environment for Information: Evidence from Greece

    Science.gov (United States)

    Kourteli, Liana

    2005-01-01

    Introduction: This paper examines the business external environment scanning theory for information in the context of Greece. Method. A questionnaire was developed to explore the relationships between general and task business environment, perceived uncertainty, scanning strategy, and sources of information with respect to type of environment,…

  14. Huntington's disease in Greece: the experience of 14 years.

    Science.gov (United States)

    Panas, M; Karadima, G; Vassos, E; Kalfakis, N; Kladi, A; Christodoulou, K; Vassilopoulos, D

    2011-12-01

    A large scale genetic and epidemiological study of Huntington's disease (HD) was carried out in Greece from January 1995 to December 2008. Diagnostic testing was carried out in 461 symptomatic individuals, while 256 were tested for presymptomatic purposes. The diagnosis of HD with a CAG expansion ≥ 36 was confirmed in 278 symptomatic individuals. The prevalence of HD in Greece was estimated at approximately 2.5 to 5.4:100,000, while the mean minimum incidence was estimated at 2.2 to 4.4 per million per year. The molecular diagnosis of HD was confirmed in the majority of patients (84.4%) sent for confirmation. The false-positive cases 15.6% were characterized by the absence of a family history of HD and the presence of an atypical clinical picture. The uptake of predictive testing for HD was 8.6%. A prenatal test was requested in six pregnancies. The findings of our study do not differ significantly from those of similar studies from other European countries despite the relative genetic isolation of Greece. Of interest is the identification of clusters of HD in Greece. The presence or absence of a family history of HD should be interpreted cautiously, during the diagnostic process. © 2010 John Wiley & Sons A/S.

  15. Timescales of Quartz Crystallization and the Longevity of the Bishop Giant Magma Body

    Energy Technology Data Exchange (ETDEWEB)

    Gualda, Guilherme A.R.; Pamukcu, Ayla S.; Ghiorso, Mark S.; Anderson, Jr. , Alfred T.; Sutton, Stephen R.; Rivers, Mark L. (OFM Res.); (Vanderbilt); (UC)

    2013-04-08

    Supereruptions violently transfer huge amounts (100 s-1000 s km{sup 3}) of magma to the surface in a matter of days and testify to the existence of giant pools of magma at depth. The longevity of these giant magma bodies is of significant scientific and societal interest. Radiometric data on whole rocks, glasses, feldspar and zircon crystals have been used to suggest that the Bishop Tuff giant magma body, which erupted {approx}760,000 years ago and created the Long Valley caldera (California), was long-lived (>100,000 years) and evolved rather slowly. In this work, we present four lines of evidence to constrain the timescales of crystallization of the Bishop magma body: (1) quartz residence times based on diffusional relaxation of Ti profiles, (2) quartz residence times based on the kinetics of faceting of melt inclusions, (3) quartz and feldspar crystallization times derived using quartz+feldspar crystal size distributions, and (4) timescales of cooling and crystallization based on thermodynamic and heat flow modeling. All of our estimates suggest quartz crystallization on timescales of <10,000 years, more typically within 500-3,000 years before eruption. We conclude that large-volume, crystal-poor magma bodies are ephemeral features that, once established, evolve on millennial timescales. We also suggest that zircon crystals, rather than recording the timescales of crystallization of a large pool of crystal-poor magma, record the extended periods of time necessary for maturation of the crust and establishment of these giant magma bodies.

  16. Zircon reveals protracted magma storage and recycling beneath Mount St. Helens

    Science.gov (United States)

    Claiborne, L.L.; Miller, C.F.; Flanagan, D.M.; Clynne, M.A.; Wooden, J.L.

    2010-01-01

    Current data and models for Mount St. Helens volcano (Washington, United States) suggest relatively rapid transport from magma genesis to eruption, with no evidence for protracted storage or recycling of magmas. However, we show here that complex zircon age populations extending back hundreds of thousands of years from eruption age indicate that magmas regularly stall in the crust, cool and crystallize beneath the volcano, and are then rejuvenated and incorporated by hotter, young magmas on their way to the surface. Estimated dissolution times suggest that entrained zircon generally resided in rejuvenating magmas for no more than about a century. Zircon elemental compositions reflect the increasing influence of mafic input into the system through time, recording growth from hotter, less evolved magmas tens of thousands of years prior to the appearance of mafic magmas at the surface, or changes in whole-rock geochemistry and petrology, and providing a new, time-correlated record of this evolution independent of the eruption history. Zircon data thus reveal the history of the hidden, long-lived intrusive portion of the Mount St. Helens system, where melt and crystals are stored for as long as hundreds of thousands of years and interact with fresh influxes of magmas that traverse the intrusive reservoir before erupting. ?? 2010 Geological Society of America.

  17. Continental rift architecture and patterns of magma migration: a dynamic analysis based on centrifuge models.

    NARCIS (Netherlands)

    Corti, G.; Bonini, M.; Sokoutis, D.; Innocenti, F.; Manetti, P.; Cloetingh, S.A.P.L.; Mulugeta, G.

    2004-01-01

    Small-scale centrifuge models were used to investigate the role of continental rift structure in controlling patterns of magma migration and emplacement. Experiments considered the reactivation of weakness zones in the lower crust and the presence of magma at Moho depths. Results suggest that

  18. Rapid heterogeneous assembly of multiple magma reservoirs prior to Yellowstone supereruptions.

    Science.gov (United States)

    Wotzlaw, Jörn-Frederik; Bindeman, Ilya N; Stern, Richard A; D'Abzac, Francois-Xavier; Schaltegger, Urs

    2015-09-10

    Large-volume caldera-forming eruptions of silicic magmas are an important feature of continental volcanism. The timescales and mechanisms of assembly of the magma reservoirs that feed such eruptions as well as the durations and physical conditions of upper-crustal storage remain highly debated topics in volcanology. Here we explore a comprehensive data set of isotopic (O, Hf) and chemical proxies in precisely U-Pb dated zircon crystals from all caldera-forming eruptions of Yellowstone supervolcano. Analysed zircons record rapid assembly of multiple magma reservoirs by repeated injections of isotopically heterogeneous magma batches and short pre-eruption storage times of 10(3) to 10(4) years. Decoupled oxygen-hafnium isotope systematics suggest a complex source for these magmas involving variable amounts of differentiated mantle-derived melt, Archean crust and hydrothermally altered shallow-crustal rocks. These data demonstrate that complex magma reservoirs with multiple sub-chambers are a common feature of rift- and hotspot related supervolcanoes. The short duration of reservoir assembly documents rapid crustal remelting and two to three orders of magnitude higher magma production rates beneath Yellowstone compared to continental arc volcanoes. The short pre-eruption storage times further suggest that the detection of voluminous reservoirs of eruptible magma beneath active supervolcanoes may only be possible prior to an impending eruption.

  19. Timescales of quartz crystallization and the longevity of the Bishop giant magma body.

    Science.gov (United States)

    Gualda, Guilherme A R; Pamukcu, Ayla S; Ghiorso, Mark S; Anderson, Alfred T; Sutton, Stephen R; Rivers, Mark L

    2012-01-01

    Supereruptions violently transfer huge amounts (100 s-1000 s km(3)) of magma to the surface in a matter of days and testify to the existence of giant pools of magma at depth. The longevity of these giant magma bodies is of significant scientific and societal interest. Radiometric data on whole rocks, glasses, feldspar and zircon crystals have been used to suggest that the Bishop Tuff giant magma body, which erupted ~760,000 years ago and created the Long Valley caldera (California), was long-lived (>100,000 years) and evolved rather slowly. In this work, we present four lines of evidence to constrain the timescales of crystallization of the Bishop magma body: (1) quartz residence times based on diffusional relaxation of Ti profiles, (2) quartz residence times based on the kinetics of faceting of melt inclusions, (3) quartz and feldspar crystallization times derived using quartz+feldspar crystal size distributions, and (4) timescales of cooling and crystallization based on thermodynamic and heat flow modeling. All of our estimates suggest quartz crystallization on timescales of magma bodies are ephemeral features that, once established, evolve on millennial timescales. We also suggest that zircon crystals, rather than recording the timescales of crystallization of a large pool of crystal-poor magma, record the extended periods of time necessary for maturation of the crust and establishment of these giant magma bodies.

  20. Compressible magma flow in a two-dimensional elastic-walled dike

    NARCIS (Netherlands)

    Woods, A.W.; Bokhove, Onno; de Boer, A; Hill, B.E.

    2006-01-01

    The ascent of magma to the Earth's surface is commonly modeled by assuming a fixed dike or flow geometry from a deep subsurface reservoir to the surface. In practice, however, this flow geometry is produced by deformation of the crust by ascending overpressured magma. Here, we explore how this

  1. Environmental tobacco smoke in hospitality venues in Greece

    Directory of Open Access Journals (Sweden)

    Tountas Yiannis

    2007-10-01

    Full Text Available Abstract Background Exposure to environmental tobacco smoke is a major threat to public health. Greece, having the highest smoking prevalence in the European Union is seriously affected by passive smoking. The purpose of this study was to measure environmental tobacco smoke (ETS exposure in the non smoking areas of hospitality venues and offices in Greece and to compare the levels of exposure to levels in the US, UK and Ireland before and after the implementation of a smoking ban. Methods Experimental measurements of particulate matter 2.5 μm (PM2.5, performed during a cross sectional study of 49 hospitality venues and offices in Athens and Crete, Greece during February – March 2006. Results Levels of ETS ranged from 19 μg/m3 to 612 μg/m3, differing according to the place of measurement. The average exposure in hospitality venues was 268 μg/m3 with ETS levels found to be highest in restaurants with a mean value of 298 μg/m3 followed by bars and cafes with 271 μg/m3. ETS levels were 76% lower in venues in which smoking was not observed compared to all other venues (p Conclusion Designated non-smoking areas of hospitality venues in Greece are significantly more polluted with ETS than outdoor air and similar venues in Europe and the United States. The implementation of a total indoor smoking ban in hospitality venues has been shown to have a positive effect on workers and patrons' health. The necessity of such legislation in Greece is thus warranted.

  2. Current Trends in the Transhumant Cattle Sector in Greece

    Directory of Open Access Journals (Sweden)

    Athanasios Ragkos

    2013-05-01

    Full Text Available Bovine transhumance is characterized by the seasonal movement of livestock between winter and summer pastures. The system is well-known for Mediterranean countries, including Greece, where its role is multifunctional, because of its complex interactions with the environments and local societies. Unlike the dairy farming sector in Greece, whose salient features are the emergence of large-sized farms which are heavily dependent on fixed capital endowments and the provision of feedstuff, the transhumant system is much more flexible, by taking advantage of excessive family labor and by reducing feeding costs through grazing. The total number of transhumant farms in Greece has diminished during the last decades this farming system remains an essential activity in less favored areas of the country; the bovine cattle transhumant system, in particular, provides an efficient alternative to the capital-intensive dairy farming system. The purpose of this study is to provide a presentation of the current condition of the transhumant bovine cattle farming system in Greece. Through a survey of all relevant public services, data concerning the number of transhumant farms and animals as well as their movements in 2011 are presented. The survey reveals that the larger amount of transhumant farms is present in the lowlands of Thessaly and of East Macedonia-Thrace and move towards the mountainous rangelands of less favored areas, particularly those of West Macedonia. The mean transhumant bovine farm size does not exceed 100 animals, as nearly 76.1%, of the total rear less than 100 cattle. Thessaly is the region which accommodates the major part of transhumant farming in Greece; this is also the case for transhumant cattle, as 51.4% of all transhumant farms in the country have their winter domiciles in Thessaly.

  3. On the conditions of magma mixing and its bearing on andesite production in the crust.

    Science.gov (United States)

    Laumonier, Mickael; Scaillet, Bruno; Pichavant, Michel; Champallier, Rémi; Andujar, Joan; Arbaret, Laurent

    2014-12-15

    Mixing between magmas is thought to affect a variety of processes, from the growth of continental crust to the triggering of volcanic eruptions, but its thermophysical viability remains unclear. Here, by using high-pressure mixing experiments and thermal calculations, we show that hybridization during single-intrusive events requires injection of high proportions of the replenishing magma during short periods, producing magmas with 55-58 wt% SiO2 when the mafic end-member is basaltic. High strain rates and gas-rich conditions may produce more felsic hybrids. The incremental growth of crustal reservoirs limits the production of hybrids to the waning stage of pluton assembly and to small portions of it. Large-scale mixing appears to be more efficient at lower crustal conditions, but requires higher proportions of mafic melt, producing more mafic hybrids than in shallow reservoirs. Altogether, our results show that hybrid arc magmas correspond to periods of enhanced magma production at depth.

  4. Evidence for crustal recycling during the Archean: the parental magmas of the stillwater complex

    International Nuclear Information System (INIS)

    McCallum, I.S.

    1988-01-01

    The petrology and geochemistry of the Stillwater Complex, an Archean (2.7 Ga) layered mafic intrusion in the Beartooth Mountains of Montana, is discussed. Efforts to reconstruct the compositions of possible parental magmas and thereby place some constraints on the composition and history of their mantle source regions was studied. A high-Mg andesite or boninite magma best matches the crystallization sequences and mineral compositions of Stillwater cumulates, and represents either a primary magma composition or a secondary magma formed, for example, by assimilation of crustal material by a very Mg-rich melt such as komatiite. Isotopic data do not support the extensive amounts of assimilation required by the komatiite parent hypothesis, and it is argued that the Stillwater magma was generated from a mantle source that had been enriched by recycling and homogenization of older crustal material over a large area

  5. «Magma»: as origens de Guimarães Rosa

    Directory of Open Access Journals (Sweden)

    Luiz Cláudio Vieira de Oliveira

    2011-10-01

    Full Text Available Resumo: Leitura de Magma, de Guimarães Rosa, com o objetivo de indicar a presença de temas, fragmentos, personagens, expressões e recursos estilísticos ali existentes, em outros textos do autor, cronologicamente posteriores.Palavras-chave: Literatura brasileira; Guimarães Rosa; Magma.Résumé: Lecture de Magma, de Guimarães Rosa, ayant l’objectif de montrer la présence de quelques sujets, fragments, personnages, expressions et traits stylistiques, que y sont présents, et aussi dans autres textes du même auteur, chronologiquement postérieurs.Mots-clés: Littérature brésilienne; Guimarães Rosa; Magma.Keywords: Brazilian literature; Guimarães Rosa; Magma.

  6. The Effect of Thermal Cycling on Crystal-Liquid Separation During Lunar Magma Ocean Differentiation

    Science.gov (United States)

    Mills, Ryan D.

    2013-01-01

    Differentiation of magma oceans likely involves a mixture of fractional and equilibrium crystallization [1]. The existence of: 1) large volumes of anorthosite in the lunar highlands and 2) the incompatible- rich (KREEP) reservoir suggests that fractional crystallization may have dominated during differentiation of the Moon. For this to have occurred, crystal fractionation must have been remarkably efficient. Several authors [e.g. 2, 3] have hypothesized that equilibrium crystallization would have dominated early in differentiation of magma oceans because of crystal entrainment during turbulent convection. However, recent numerical modeling [4] suggests that crystal settling could have occurred throughout the entire solidification history of the lunar magma ocean if crystals were large and crystal fraction was low. These results indicate that the crystal size distribution could have played an important role in differentiation of the lunar magma ocean. Here, I suggest that thermal cycling from tidal heating during lunar magma ocean crystallization caused crystals to coarsen, leading to efficient crystal-liquid separation.

  7. Rapid mixing and short storage timescale in the magma dynamics of a steady-state volcano

    Science.gov (United States)

    Petrone, Chiara Maria; Braschi, Eleonora; Francalanci, Lorella; Casalini, Martina; Tommasini, Simone

    2018-06-01

    Steady-state volcanic activity implies equilibrium between the rate of magma replenishment and eruption of compositionally homogeneous magmas, lasting for tens to thousands of years in an open conduit system. The Present-day activity of Stromboli volcano (Aeolian Islands, Southern Italy) has long been recognised as typical of a steady-state volcano, with a shallow magmatic reservoir (highly porphyritic or hp-magma) continuously refilled by more mafic magma (with low phenocryst content or lp-magma) at a constant rate and accompanied by mixing, crystallisation and eruption. Our aim is to clarify the timescale and dynamics of the plumbing system at the establishment of the Present-day steady-state activity (volcanoes.

  8. Magma genesis at Gale Crater: Evidence for Pervasive Mantle Metasomatism

    Science.gov (United States)

    Filiberto, J.

    2017-12-01

    Basaltic rocks have been analyzed at Gale Crater with a larger range in bulk chemistry than at any other landing site [1]. Therefore, the rocks may have experienced significantly different formation conditions than those experienced by magmas at Gusev Crater or Meridiani Planum. Specifically, the rocks at Gale Crater have higher potassium than other Martian rocks, with a potential analog of the Nakhlite parental magma, and are consistent with forming from a metasomatized mantle source [2-4]. Mantle metasomatism would not only affect the bulk chemistry but mantle melting conditions, as metasomatism fluxes fluids into the source region. Here I will combine differences in bulk chemistry between Martian basalts to calculate formation conditions in the interior and investigate if the rocks at Gale Crater experienced magma genesis conditions consistent with metasomatism - lower temperatures and pressures of formation. To calculate average formation conditions, I rely on experimental results, where available, and silica-activity and Mg-exchange thermometry calculations for all other compositions following [5, 6]. The results show that there is a direct correlation between the calculated mantle potential temperature and the K/Ti ratio of Gale Crater rocks. This is consistent with fluid fluxed metasomatism introducing fluids to the system, which depressed the melting temperature and fluxed K but not Ti to the system. Therefore, all basalts at Gale Crater are consistent with forming from a metasomatized mantle source, which affected not only the chemistry of the basalts but also the formation conditions. References: [1] Cousin A. et al. (2017) Icarus. 288: 265-283. [2] Treiman A.H. et al. (2016) Journal of Geophysical Research: Planets. 121: 75-106. [3] Treiman A.H. and Medard E. (2016) Geological Society of America Abstracts with Programs. 48: doi: 10.1130/abs/2016AM-285851. [4] Schmidt M.E. et al. (2016) Geological Society of America Abstracts with Programs. 48: doi: 10

  9. Volcanic systems of Iceland and their magma source

    Science.gov (United States)

    Sigmarsson, Olgeir

    2017-04-01

    Several active hot-spot volcanoes produce magma from mantle sources which composition varies on decadal time scale. This is probably best demonstrated by the recent work of Pietruszka and collaborators on Kilauea, Hawaii. In marked contrast, basalt lavas from volcanic system in Iceland located above the presumed centre of the Iceland mantle plume have uniform isotope composition over the last 10 thousand years. Volcanic systems are composed of a central volcano and a fissure swarm, or a combination of both and they represent a fundamental component of the neovolcanic zones in Iceland. Four such systems, those of Askja, Bárðarbunga, Kverkfjöll and Grímsvötn in central Iceland were chosen for investigation. The last three have central volcanoes covered by the Vatnajökull ice-sheet whereas part of their fissure swarms is ice-free. Tephra produced during subglacial eruptions together with lavas from the fissure swarms of Holocene age have been collected and analysed for Sr, Nd and Th isotope ratios. Those volcanic formations that can be univocally correlated to a given volcanic system display uniform isotope ratio but different from one volcanic system to another. An exception to this regularity is that Askja products have isotope ratios indistinguishable from those of Gímsvötn, but since these volcanic systems lies far apart their lava fields do not overlap. A practical aspect of these findings was demonstrated during the rifting event of Bárðarbunga and fissure eruption forming the Holuhraun lava field. Relatively low, O isotope ratios in these basalts and heterogeneous macrocrystal composition have been ascribed to important metabasaltic crustal contamination with or without crystal mush recycling. In that case a surprisingly efficient magma mixing and melt homogenization must have occurred in the past beneath the volcanic systems. One possibility is that during the rapid deglaciation much mantle melting occurred and melts accumulated at the mantle

  10. Slab melting and magma formation beneath the southern Cascade arc

    Science.gov (United States)

    Walowski, Kristina J.; Wallace, Paul J.; Clynne, Michael A.; Rasmussen, D.J.; Weis, D.

    2016-01-01

    The processes that drive magma formation beneath the Cascade arc and other warm-slab subduction zones have been debated because young oceanic crust is predicted to largely dehydrate beneath the forearc during subduction. In addition, geochemical variability along strike in the Cascades has led to contrasting interpretations about the role of volatiles in magma generation. Here, we focus on the Lassen segment of the Cascade arc, where previous work has demonstrated across-arc geochemical variations related to subduction enrichment, and H-isotope data suggest that H2O in basaltic magmas is derived from the final breakdown of chlorite in the mantle portion of the slab. We use naturally glassy, olivine-hosted melt inclusions (MI) from the tephra deposits of eight primitive (MgO>7 wt%) basaltic cinder cones to quantify the pre-eruptive volatile contents of mantle-derived melts in this region. The melt inclusions have B concentrations and isotope ratios that are similar to mid-ocean ridge basalt (MORB), suggesting extensive dehydration of the downgoing plate prior to reaching sub-arc depths and little input of slab-derived B into the mantle wedge. However, correlations of volatile and trace element ratios (H2O/Ce, Cl/Nb, Sr/Nd) in the melt inclusions demonstrate that geochemical variability is the result of variable addition of a hydrous subduction component to the mantle wedge. Furthermore, correlations between subduction component tracers and radiogenic isotope ratios show that the subduction component has less radiogenic Sr and Pb than the Lassen sub-arc mantle, which can be explained by melting of subducted Gorda MORB beneath the arc. Agreement between pMELTS melting models and melt inclusion volatile, major, and trace element data suggests that hydrous slab melt addition to the mantle wedge can produce the range in primitive compositions erupted in the Lassen region. Our results provide further evidence that chlorite-derived fluids from the mantle portion of the

  11. [Medical myths and notions in Ancient Greece].

    Science.gov (United States)

    Boulogne, J

    2001-01-01

    The article deals with the views on health and disease prevalent in Ancient Greece, the cradle of modern European medicine, focusing on the ever-present myths functioning in that realm despite attempts to rationally explain medical phenomena. On the basis of the works of Hippocrates and Galen, the author has distinguished five different epistemological attitudes towards those phenomena: the holistic, macrocosmological, monistic, anti-hypothetical and eclectic. The first was based on the idea of mechanical and logical causes. In medicine it is marked by determinism connected with climatic conditions. Hippocrates believed that health depended on the weather, in particular on the effects of winds, types of water and properties of soil. Myth emerged in this conception in the way matter - earth, water, air and fire - was conceived, particular in the properties ascribed to them: cold, humidity, aridity and warmth. The author charges that this conception was permeated with ethnocentrism and cites examples invoked by Hippocrates on the basis of his observations on the Scythians. The macrocosmological attitude involves subordinating medicine to cosmology. Man's body is a microcosm. The author cites the treatise 'On Diets', in which the greatest importance both in the universe and in processes taking place in the human body as ascribed to two factors - fire and water. Their combination was said to have played a crucial role in the typology of corporal and mental constitutions. Those features, together with the seasons of the year, mode of behaviour and food, constitute the four forces guiding vital processes. The author then presents the embryogenic conception contained in the cosmological treatise. It was based on such things as numerological speculations, hence - despite its rationalistic assumptions, consigns it to the mythic. The third attitude, the monistic approach, presents a treatise ascribed to Hippocrates 'On the Sacred Disease' and dealing with epilepsy. The

  12. Experimental interaction of magma and “dirty” coolants

    Science.gov (United States)

    Schipper, C. Ian; White, James D. L.; Zimanowski, Bernd; Büttner, Ralf; Sonder, Ingo; Schmid, Andrea

    2011-03-01

    The presence of water at volcanic vents can have dramatic effects on fragmentation and eruption dynamics, but little is known about how the presence of particulate matter in external water will further alter eruptions. Volcanic edifices are inherently “dirty” places, where particulate matter of multiple origins and grainsizes typically abounds. We present the results of experiments designed to simulate non-explosive interactions between molten basalt and various “coolants,” ranging from homogeneous suspensions of 0 to 30 mass% bentonite clay in pure water, to heterogeneous and/or stratified suspensions including bentonite, sand, synthetic glass beads and/or naturally-sorted pumice. Four types of data are used to characterise the interactions: (1) visual/video observations; (2) grainsize and morphology of resulting particles; (3) heat-transfer data from a network of eight thermocouples; and (4) acoustic data from three force sensors. In homogeneous coolants with ~20% sediment, heat transfer is by forced convection and conduction, and thermal granulation is less efficient, resulting in fewer blocky particles, larger grainsizes, and weaker acoustic signals. Many particles are droplet-shaped or/and “vesicular,” containing bubbles filled with coolant. Both of these particle types indicate significant hydrodynamic magma-coolant mingling, and many of them are rewelded into compound particles. The addition of coarse material to heterogeneous suspensions further slows heat transfer thus reducing thermal granulation, and variable interlocking of large particles prevents efficient hydrodynamic mingling. This results primarily in rewelded melt piles and inefficient distribution of melt and heat throughout the coolant volume. Our results indicate that even modest concentrations of sediment in water will significantly limit heat transfer during non-explosive magma-water interactions. At high concentrations, the dramatic reduction in cooling efficiency and increase in

  13. Mechanisms of differentiation in the Skaergaard magma chamber

    Science.gov (United States)

    Tegner, C.; Lesher, C. E.; Holness, M. B.; Jakobsen, J. K.; Salmonsen, L. P.; Humphreys, M. C. S.; Thy, P.

    2012-04-01

    The Skaergaard intrusion is a superb natural laboratory for studying mechanisms of magma chamber differentiation. The magnificent exposures and new systematic sample sets of rocks that solidified inwards from the roof, walls and floor of the chamber provide means to test the relative roles of crystal settling, diffusion, convection, liquid immiscibility and compaction in different regions of the chamber and in opposite positions relative to gravity. Examination of the melt inclusions and interstitial pockets has demonstrated that a large portion of intrusion crystallized from an emulsified magma chamber composed of immiscible silica- and iron-rich melts. The similarity of ratios of elements with opposite partitioning between the immiscible melts (e.g. P and Rb) in wall, floor and roof rocks, however, indicate that large-scale separation did not occur. Yet, on a smaller scale of metres to hundred of metres and close to the interface between the roof and floor rocks (the Sandwich Horizon), irregular layers and pods of granophyre hosted by extremely iron-rich cumulates point to some separation of the two liquid phases. Similar proportions of the primocryst (cumulus) minerals in roof, wall and floor rocks indicate that crystal settling was not an important mechanism. Likewise, the lack of fractionation of elements with different behavior indicate that diffusion and fluid-driven metasomatism played relatively minor roles. Compositional convection and/or compaction within the solidifying crystal mush boundary layer are likely the most important mechanisms. A correlation of low trapped liquid fractions (calculated from strongly incompatible elements) in floor rocks with high fractionation density (the density difference between the crystal framework and the liquid) indicate that compaction is the dominating process in expelling evolved liquid from the crystal mush layer. This is supported by high and variable trapped liquid contents in the roof rocks, where gravity

  14. Eruption Depths, Magma Storage and Magma Degassing at Sumisu Caldera, Izu-Bonin Arc: Evidence from Glasses and Melt Inclusions

    Science.gov (United States)

    Johnson, E. R.

    2015-12-01

    Island arc volcanoes can become submarine during cataclysmal caldera collapse. The passage of a volcanic vent from atmospheric to under water environment involves complex modifications of the eruption style and subsequent transport of the pyroclasts. Here, we use FTIR measurements of the volatile contents of glass and melt inclusions in the juvenile pumice clasts in the Sumisu basin and its surroundings (Izu-Bonin arc) to investigate changes in eruption depths, magma storage and degassing over time. This study is based on legacy cores from ODP 126, where numerous unconsolidated (250 m), massive to normally graded pumice lapilli-tuffs were recovered over four cores (788C, 790A, 790B and 791A). Glass and clast geochemistry indicate the submarine Sumisu caldera as the source of several of these pumice lapilli-tuffs. Glass chips and melt inclusions from these samples were analyzed using FTIR for H2O and CO2 contents. Glass chips record variable H2O contents; most chips contain 0.6-1.6 wt% H2O, corresponding to eruption depths of 320-2100 mbsl. Variations in glass H2O and pressure estimates suggest that edifice collapse occurred prior-to or during eruption of the oldest of these samples, and that the edifice may have subsequently grown over time. Sanidine-hosted melt inclusions from two units record variably degassed but H2O-rich melts (1.1-5.6 wt% H2O). The lowest H2O contents overlap with glass chips, consistent with degassing and crystallization of melts until eruption, and the highest H2O contents suggest that large amounts of degassing accompanied likely explosive eruptions. Most inclusions, from both units, contain 2-4 wt% H2O, which further indicates that the magmas crystallized at pressures of ~50-100 MPa, or depths ~400-2800 m below the seafloor. Further glass and melt inclusion analyses, including major element compositions, will elucidate changes in magma storage, degassing and evolution over time.

  15. Spatial and temporal variability of the Aridity Index in Greece

    Science.gov (United States)

    Nastos, Panagiotis T.; Politi, Nadia; Kapsomenakis, John

    2013-01-01

    The objective of this paper is to study the spatial and temporal variability of the Aridity Index (AI) in Greece, per decade, during the 50-year period (1951-2000). Besides, the projected changes in ensemble mean AI between the period 1961-1990 (reference period) and the periods 2021-2050 (near future) and 2071-2100 (far future) along with the inter-model standard deviations were presented, based on the simulation results, derived from a number of Regional Climatic Models (RCMs), within the ENSEMBLE European Project. The projection of the future climate was done under SRES A1B. The climatic data used, concern monthly precipitation totals and air temperature from 28 meteorological stations (22 stations from the Hellenic National Meteorological Service and 6 stations from neighboring countries, taken from the Monthly Climatic Data for the World). The estimation of the AI was carried out based on the potential evapotranspiration (PET) defined by Thornthwaite (1948). The data processing was done by the application of the statistical package R-project and the Geographical Information Systems (GIS). The results of the analysis showed that, within the examined period (1951-2000), a progressive shift from the "humid" class, which characterized the wider area of Greece, towards the "sub-humid" and "semi-arid" classes appeared in the eastern Crete Island, the Cyclades complex, the Evia and Attica, that is mainly the eastern Greece. The most significant change appears during the period 1991-2000. The future projections at the end of twentieth century, using ensemble mean simulations from 8 RCMs, show that drier conditions are expected to establish in regions of Greece (Attica, eastern continental Greece, Cyclades, Dodecanese, eastern Crete Island and northern Aegean). The inter-model standard deviation over these regions ranges from 0.02 to 0.05 against high values (0.09-0.15) illustrated in western mountainous continental Greece, during 2021-2050. Higher values of inter

  16. Radon concentration measurements in waters in Greece and Cyprus

    International Nuclear Information System (INIS)

    Louizi, A.; Nikolopoulos, D.; Tzortzi, A.; Thanassas, D.; Serefoglou, A.; Georgiou, E.; Vogiannis, E.; Koukouliou, V.

    2004-01-01

    The radon content of drinking water samples was determined with Alpha Guard Pro equipped with an appropriate unit (Aqua Kit). The samples were collected from water taps in dwellings located at various cities in Greece and Cyprus. In addition, surface water samples from rivers, lakes and seas as well as potable underground and hot spring water samples from Greece and Cyprus were also collected. For a precise determination of radon concentration in water samples, special procedures were followed both for sampling and transportation, as well as for measurement. Intercomparison experiments were designed and implemented before and during the study. Radon concentrations in drinking water samples in Greece ranged between 1.1 ± 0.5 Bq/L and 410±50 Bq/L. The corresponding concentrations in Cyprus ranged between 1.3 ± 0.8 Bq/L and 15±4 Bq/L. Three samples collected from the city of Arnea Chalkidikis (Northern Greece) exhibited high concentrations of 120±20 Bq/L, 320±40 Bq/L and 410±50 Bq/L. This city is identified as a high radon potential area. One water sample located in Lesvos Island (North-East part of Greece) exhibited radon concentration 140±20 Bq/L. Additional six samples displayed high concentrations in potable hot spring water samples. These samples which were collected from the city of Loutraki (Peloponnesus) ranged between 220-230 Bq/L. In addition, two samples characterized as 'medicinal drinking water' gave concentrations between 320 Bq/L and 340 Bq/L. For underground water samples the radon concentrations ranged between 1.2±0.7 Bq/L and 15±4 Bq/L, while for surface water samples the range was 2.7±0.8 Bq/L to 24±6 Bq/L. The observed concentrations of radon gas in potable water samples in Greece were found to be largely low. In Cyprus, they were all well below 15 Bq/L

  17. Magma transfer at Campi Flegrei caldera (Italy) before the 1538 AD eruption.

    Science.gov (United States)

    Di Vito, Mauro A; Acocella, Valerio; Aiello, Giuseppe; Barra, Diana; Battaglia, Maurizio; Carandente, Antonio; Del Gaudio, Carlo; de Vita, Sandro; Ricciardi, Giovanni P; Ricco, Ciro; Scandone, Roberto; Terrasi, Filippo

    2016-08-25

    Calderas are collapse structures related to the emptying of magmatic reservoirs, often associated with large eruptions from long-lived magmatic systems. Understanding how magma is transferred from a magma reservoir to the surface before eruptions is a major challenge. Here we exploit the historical, archaeological and geological record of Campi Flegrei caldera to estimate the surface deformation preceding the Monte Nuovo eruption and investigate the shallow magma transfer. Our data suggest a progressive magma accumulation from ~1251 to 1536 in a 4.6 ± 0.9 km deep source below the caldera centre, and its transfer, between 1536 and 1538, to a 3.8 ± 0.6 km deep magmatic source ~4 km NW of the caldera centre, below Monte Nuovo; this peripheral source fed the eruption through a shallower source, 0.4 ± 0.3 km deep. This is the first reconstruction of pre-eruptive magma transfer at Campi Flegrei and corroborates the existence of a stationary oblate source, below the caldera centre, that has been feeding lateral eruptions for the last ~5 ka. Our results suggest: 1) repeated emplacement of magma through intrusions below the caldera centre; 2) occasional lateral transfer of magma feeding non-central eruptions within the caldera. Comparison with historical unrest at calderas worldwide suggests that this behavior is common.

  18. Reconstructing modalities of magma storage in the crust by thermo-rheological modelling

    Science.gov (United States)

    Caricchi, L.; Annen, C.; Rust, A.; Blundy, J.

    2012-04-01

    During my PhD I worked under the supervision of Luigi Burlini studying the rheological behaviour of magma. Luigi was not only a great teacher and friend but he was also able to project the science he was performing beyond the obvious applications. This aspect of Luigi's approach shaped my approach to research and brought me to think to ways of applying the studies we performed together to unravel the complexity of nature that impassioned and inspired him. This contribution comes from the motivation and interest that Luigi created in me during the short, but truly memorable journey we shared together. This study combines petrology, thermal modelling and magma rheology to characterise timescales and modalities of magma emplacement in the Earth's crust. Thermal modelling was performed to determine the influence of magma injection rates in the crust on the temperature evolution of a magmatic body. The injected tonalitic magma was considered to contain dioritic enclaves, common in plutons. The contrast in chemical composition between host and enclaves leads to different crystallinities of these magmas during cooling and produce a rheological contrast that permits reciprocal deformation only in restricted temperature ranges. Characterising the thermal and rheological evolution of host magma and enclaves, we traced the evolution of strain recorded by these inclusions during the construction of an intrusion, showing that the strain recorded by enclaves distributed in different portions of a pluton can be used to constrain thermal evolution in time, magmatic fluxes and timescale of assemblage of magmatic bodies in the crust.

  19. Magma buoyancy and volatile ascent driving autocyclic eruptivity at Hekla Volcano (Iceland)

    Science.gov (United States)

    Hautmann, Stefanie; Sacks, I. Selwyn; Linde, Alan T.; Roberts, Matthew J.

    2017-09-01

    Volcanic eruptions are typically accompanied by ground deflation due to the withdrawal of magma from depth and its effusion at the surface. Here, based on continuous high-resolution borehole strain data, we show that ground deformation was absent during the major effusion phases of the 1991 and 2000 eruptions of Hekla Volcano, Iceland. This lack of surface deformation challenges the classic model of magma intrusion/withdrawal as source for volcanic ground uplift/subsidence. We incorporate geodetic and geochemical observables into theoretical models of magma chamber dynamics in order to constrain quantitatively alternative co- and intereruptive physical mechanisms that govern magma propagation and system pressurization. We find the lack of surface deformation during lava effusion to be linked to chamber replenishment from below whilst magma migrates as a buoyancy-driven flow from the magma chamber towards the surface. We further demonstrate that intereruptive pressure build-up is likely to be generated by volatile ascent within the chamber rather than magma injection. Our model explains the persistent periodic eruptivity at Hekla throughout historic times with self-initiating cycles and is conceptually relevant to other volcanic systems.

  20. The magma plumbing system in the Mariana Trough back-arc basin at 18° N

    Science.gov (United States)

    Lai, Zhiqing; Zhao, Guangtao; Han, Zongzhu; Huang, Bo; Li, Min; Tian, Liyan; Liu, Bo; Bu, Xuejiao

    2018-04-01

    Mafic magmas are common in back-arc basin, once stalled in the crust, these magmas may undergo different evolution. In this paper, compositional and textural variations of plagioclase as well as mineral-melt geothermobarometry are presented for basalts erupted from the central Mariana Trough (CMT). These data reveal crystallization conditions and we attempt a reconstruction of the magma plumbing system of the CMT. Plagioclase megacrysts, phenocrysts, microphenocrysts, microlites, olivine, spinel, and clinopyroxene have been recognized in basalt samples, using BSE images and compositional features. The last three minerals are homogeneous as microphenocrysts. Mineral-melt barometry indicates that plagioclase crystals crystallized and eventually grew into phenocrysts and megacrysts in mush zone with depth of 5-9 km, in which the normal zoning plagioclases crystallized in the interval of various batches of basic magma recharging. Plagioclase megacrysts and phenocrysts were dissolved and/or resorbed, when new basic magmas injected into the mush zone near Moho depth. It is inferred that magma extracted from the mush zone, and adiabatically ascended via different pathways. Some basaltic magmas underwent plagioclase and clinopyroxene microphenocrysts crystallization in low-pressure before eruption. Plagioclase microlites and outermost rims probably crystallized after eruption.

  1. Locating the depth of magma supply for volcanic eruptions, insights from Mt. Cameroon.

    Science.gov (United States)

    Geiger, Harri; Barker, Abigail K; Troll, Valentin R

    2016-10-07

    Mt. Cameroon is one of the most active volcanoes in Africa and poses a possible threat to about half a million people in the area, yet knowledge of the volcano's underlying magma supply system is sparse. To characterize Mt. Cameroon's magma plumbing system, we employed mineral-melt equilibrium thermobarometry on the products of the volcano's two most recent eruptions of 1999 and 2000. Our results suggest pre-eruptive magma storage between 20 and 39 km beneath Mt. Cameroon, which corresponds to the Moho level and below. Additionally, the 1999 eruption products reveal several shallow magma pockets between 3 and 12 km depth, which are not detected in the 2000 lavas. This implies that small-volume magma batches actively migrate through the plumbing system during repose intervals. Evolving and migrating magma parcels potentially cause temporary unrest and short-lived explosive outbursts, and may be remobilized during major eruptions that are fed from sub-Moho magma reservoirs.

  2. Degassing during quiescence as a trigger of magma ascent and volcanic eruptions.

    Science.gov (United States)

    Girona, Társilo; Costa, Fidel; Schubert, Gerald

    2015-12-15

    Understanding the mechanisms that control the start-up of volcanic unrest is crucial to improve the forecasting of eruptions at active volcanoes. Among the most active volcanoes in the world are the so-called persistently degassing ones (e.g., Etna, Italy; Merapi, Indonesia), which emit massive amounts of gas during quiescence (several kilotonnes per day) and erupt every few months or years. The hyperactivity of these volcanoes results from frequent pressurizations of the shallow magma plumbing system, which in most cases are thought to occur by the ascent of magma from deep to shallow reservoirs. However, the driving force that causes magma ascent from depth remains unknown. Here we demonstrate that magma ascent can be triggered by the passive release of gas during quiescence, which induces the opening of pathways connecting deep and shallow magma reservoirs. This top-down mechanism for volcanic eruptions contrasts with the more common bottom-up mechanisms in which magma ascent is only driven by processes occurring at depth. A cause-effect relationship between passive degassing and magma ascent can explain the fact that repose times are typically much longer than unrest times preceding eruptions, and may account for the so frequent unrest episodes of persistently degassing volcanoes.

  3. Drilling into Rhyolitic Magma at Shallow depth at Krafla Volcanic Complex, NE-Iceland

    Science.gov (United States)

    Mortensen, A. K.; Markússon, S. H.; Gudmundsson, Á.; Pálsson, B.

    2017-12-01

    Krafla volcanic complex in NE-Iceland is an active volcano but the latest eruption was the Krafla Fires in 1975-1984. Though recent volcanic activity has consisted of basaltic fissure eruptions, then it is rhyolitic magma that has been intercepted on at least two occasions while drilling geothermal production wells in the geothermal field suggesting a layered magma plumbing system beneath the Krafla volcanic complex. In 2008 quenched rhyolitic glass was retrieved from the bottom of well KJ-39, which is 2865 m deep ( 2571 m true vertical depth). In 2009 magma was again encountered at an even shallower depth and in more than 2,5 km distance from the bottom of well KJ-39, but in 2009 well IDDP-1 was drilled into magma three times just below 2100 m depth. Only on the last occasion was quenched glass retrieved to confirm that magma had been encountered. In well KJ-39 the quenched glass was rhyolitic in composition. The glass contained resorbed minerals of plagioclase, clinopyroxene and titanomagnetite, but the composition of the glass resembles magma that has formed by partial melting of hydrated basalt. The melt was encountered among cuttings from impermeable, coarse basaltic intrusives at a depth, where the well was anticipated to penetrate the Hólseldar volcanic fissure. In IDDP-1 the quenched glass was also rhyolitic in composition. The glass contained less than 5% of phenocrysts, but the phenocryst assemblage included andesine plagioclase, augite, pigeonite, and titanomagnetite. At IDDP-1 the melt was encountered below a permeable zone composed of fine to coarse grained felsite and granophyre. The disclosure of magma in two wells at Krafla volcanic complex verify that rhyolitic magma can be encountered at shallow depth across a larger area within the caldera. The encounter of magma at shallow depth conforms with that superheated conditions have been found at >2000 m depth in large parts of Krafla geothermal field.

  4. The parent magma of the Nakhla (SNC) meteorite: Reconciliation of composition estimates from magmatic inclusions and element partitioning

    Science.gov (United States)

    Treiman, A. H.

    1993-01-01

    The composition of the parent magma of the Nakhla meteorite was difficult to determine, because it is accumulate rock, enriched in olivine and augite relative to a basalt magma. A parent magma composition is estimated from electron microprobe area analyses of magmatic inclusions in olivine. This composition is consistent with an independent estimate based on the same inclusions, and with chemical equilibria with the cores of Nakhla's augites. This composition reconciles most of the previous estimates of Nakhla's magma composition, and obviates the need for complex magmatic processes. Inconsistency between this composition and those calculated previously suggests that magma flowed through and crystallized into Nakhla as it cooled.

  5. The parent magma of xenoliths in shergottite EETA79001: Bulk and trace element composition inferred from magmatic inclusions

    Science.gov (United States)

    Treiman, Allan H.; Lindstrom, David J.; Martinez, Rene R.

    1994-01-01

    The SNC meteorites are samples of the Martian crust, so inferences about their origins and parent magmas are of wide planetologic significance. The EETA79001 shergottite, a basalt, contains xenoliths of pyroxene-olivine cumulate rocks which are possibly related to the ALHA77005 and LEW88516 SNC lherzolites. Olivines in the xenoliths contain magmatic inclusions, relics of magma trapped within the growing crystals. The magmatic inclusions allow a parent magma composition to be retrieved; it is similar to the composition reconstructed from xenolith pyroxenes by element distribution coefficients. The xenolith parent magma is similar but not identical to parent magmas for the shergottite lherzolites.

  6. Growing out of the Crisis: Hidden Assets to Greece's Transition to an Innovation Economy

    OpenAIRE

    Herrmann, Benedikt; Kritikos, Alexander S.

    2013-01-01

    Greece's currently planned institutional reforms will help to get the country going with limited economic growth. With an economy based primarily on tourism, trade, and agriculture, Greece lacks an established competitive industry and an innovation-friendly environment, resulting in a low export ratio given the small size of the country and its long-time EU-membership. Instead, Greece exports only its nation's talent, with low returns. To become prosperous, the country must better capitalize ...

  7. Developments in the utilisation of wind energy in Greece

    International Nuclear Information System (INIS)

    Papadopoulos, A.M.; Glinou, G.L.; Papachristos, D.

    2008-01-01

    The utilisation of renewable energy sources, and wind energy in particular, can be described in Greece as a story of high expectations, intense initial entrepreneurial interest, delays in the start-up phase of projects and, some times, disappointments during the implementation procedure. Still, the current situation gives reasons for some optimism. This paper provides a review of the present technological background in wind generators, as found in the Greek market, as well as a detailed analysis of the legislative framework. Moreover, it aims to analyse the development of the process of granting investment and production permissions and their implementation since 1999. Thus, it is possible to identify the main reasons for the problems that occurred since the liberalisation of the electricity market and to account for the interest in wind energy. Finally, comments and proposals are formulated concerning the hidden barriers, the pertinent problems and the promising perspectives of the use of wind energy in Greece. (author)

  8. An overview of solar energy applications in buildings in Greece

    Science.gov (United States)

    Papamanolis, Nikos

    2016-09-01

    This work classifies and describes the main fields of solar energy exploitation in buildings in Greece, a country with high solar energy capacities. The study focuses on systems and technologies that apply to residential and commercial buildings following the prevailing design and construction practices (conventional buildings) and investigates the effects of the architectural and constructional characteristics of these buildings on the respective applications. In addition, it examines relevant applications in other building categories and in buildings with increased ecological sensitivity in their design and construction (green buildings). Through its findings, the study seeks to improve the efficiency and broaden the scope of solar energy applications in buildings in Greece to the benefit of their energy and environmental performance.

  9. From Asia Minor to Greece: History, Memory and Migration

    Directory of Open Access Journals (Sweden)

    Emine Yeşim Bedlek

    2017-08-01

    Full Text Available History and memory studies are among the most controversial topics of our era. While the official history is made up of state discourse, personal history reaches the reader through the memories of the individuals. The events that leave traces in memory are passed on to future generations by oral history studies. The pasts of individuals whose individual experiences are unpacked by the oral historians give us more detailed information about the traumas individuals. Yiannis Karatzoglou also documents his past in order to pass the traumas of migration due to the Lausanne Convention signed in 1923 between Greece and Turkey. This study examines the impact of the social, cultural and political decisions of Turkey and Greece on individuals through the life story of Yiannis in the light of history and memory.

  10. Pyrolysis of forestry biomass by-products in Greece

    Energy Technology Data Exchange (ETDEWEB)

    Zabaniotou, A.A.

    1999-06-01

    This article summarizes the technical characteristics of a biomass pyrolysis pilot plant recently constructed in central Greece. It highlights the considerations involved in achieving successful pyrolysis technology and environmental and developmental goals, by reviewing technical and nontechnical barriers associated with biomass treatment technology in Greece. Data from the start-up phase of the plant operation are presented and some aspects of the process are outlined. The capacity of the plant is 1200 1450 kg hr, based on wet biomass (Arbutus Unedo) and the pyrolysis temperature is approximately 400{sup o}C. Char yield is 1418 % weight on dry basis and is of good quality consisting of 76{sup o}C with heat content 6760 kcal kg. Bio-oil includes 63% C and its heat content is 6250 kcal kg. (author)

  11. Pyrolysis of forestry biomass by-products in Greece

    Energy Technology Data Exchange (ETDEWEB)

    Zabaniotou, A.A. [Aristotle Univ. of Thessaloniki (Greece). Dept. of Chemical Engineering

    1999-06-01

    This article summarizes the technical characteristics of a biomass pyrolysis pilot plant recently constructed in central Greece. It highlights the considerations involved in achieving successful pyrolysis technology and environmental and developmental goals, by reviewing technical and nontechnical barriers associated with biomass treatment technology in Greece. Data from the start-up phase of the plant operation are presented and some aspects of the process are outlined. The capacity of the plant is 1200--1450 kg/hr, based on wet biomass (Arbutus Unedo) and the pyrolysis temperature is approximately 400 C. Char yield is 14--18% weight on dry basis and is of good quality consisting of 76% C with heat content 6760 kcal/kg. Bio-oil includes 64% C and its heat content is 6250 kcal/kg.

  12. Adoption and use of e-invoicing in Greece

    Energy Technology Data Exchange (ETDEWEB)

    Marinagi, C., E-mail: marinagi@teihal.gr, E-mail: ptrivel@yahoo.com, E-mail: preklitis@yahoo.com; Trivellas, P., E-mail: marinagi@teihal.gr, E-mail: ptrivel@yahoo.com, E-mail: preklitis@yahoo.com; Reklitis, Panagiotis, E-mail: marinagi@teihal.gr, E-mail: ptrivel@yahoo.com, E-mail: preklitis@yahoo.com [Technological Educational Institute of Sterea Ellada, Department of Logistics Management, 1st km of Old National Roal Thiva-Elefsis-32200, Thiva (Greece); Skourlas, C., E-mail: cskourlas@teiath.gr [Technological Educational Institute of Athens, Department of Informatics, Ag. Spyridonos, Aigaleo-12210, Athens (Greece)

    2015-02-09

    This paper investigates the adoption and use of electronic invoices (e-invoices) in Greek organizations. The study attempts to evaluate current practices applied in implementing e-invoicing. A field research has been conducted, which is based on a structured questionnaire. The target sample consisted of 42 Greek enterprises. The main issues of the investigation include the existing invoice processing practices, the barriers that prevent the extended adoption and use of e-invoicing, the observed benefits from e-invoicing implementation, and the strategic drivers for transition to e-invoicing. Currently, the use of e-invoicing in Greece is low. However, the research results testify that the adoption of e-invoicing in Greece is promising. Even though, a number of enterprises state that benefits of e-invoicing are not clear yet, the majority of enterprises agree that there are crucial financial priorities that e-invoicing is expected to support.

  13. Sludge utilisation in agriculture: possibilities and prospects in Greece.

    Science.gov (United States)

    Andreadakis, A D; Mamals, D; Gavalaki, E; Kampylafka, S

    2002-01-01

    The paper presents the prospects for agricultural utilisation of the sludge produced from wastewater treatment plants in Greece and more specifically focuses on a critical review of the legislatory framework, determination of the quantitative and qualitative characteristics of the produced sludges, examination of possible sludge treatment methods and evaluation of the possibilities and prospects of sludge utilisation on the basis of the above considerations. Landfilling is practically the only route to sludge disposal in Greece. However, in view of the anticipated future restrictions for landfilling within the European Union, this method is clearly a short-term solution and alternative options, including agricultural reuse, must be implemented. The results of a recent survey are presented and discussed in relation to this need.

  14. The medical social centres in support of Roma in Greece

    DEFF Research Database (Denmark)

    Andrioti, Despena; Kotrotsou, Christina; Tsakatara, Vanta

    2013-01-01

    . Medical social centres operate in 33 Roma settlements all over the country. These centres provide vaccination, health promotion, disease prevention and health education services, as well as support in issuing documents and making appointments with health and social services. We recommend that the National......Roma people form the largest ethnic-minority group in Europe. They account for around 10 to 12 million people, and they face racism, discrimination and social exclusion in most countries. The Roma population of Greece currently numbers around 250 000 individuals. They have Greek nationality...... and enjoy the same rights, privileges and responsibilities as any other Greek citizens. Nevertheless, Roma in Greece face multiple inequalities and social exclusion in terms of housing, employment, education, and health and social services. In this report we present the outcome of a bestpractice initiative...

  15. Tax wedge in Croatia, Austria, Hungary, Poland and Greece

    Directory of Open Access Journals (Sweden)

    Marin Onorato

    2016-06-01

    Full Text Available The aim of this paper is to compare the tax burden on labour income in Croatia, Austria, Greece, Hungary and Poland in 2013. The Taxing Wages methodology has been applied to hypothetical units across a range of gross wages in order to calculate net average tax wedge, net average tax rate, as well as other relevant indicators. When it comes to single workers without children, the smallest tax wedge for workers earning less than the average gross wage was found in Croatia, while Poland had the smallest tax wedge for above-average wages. Due to a progressive PIT system, the tax wedge for a single worker in Croatia reaches 50% at 400% of the average gross wage, equalling that of Austria, Greece and Hungary. Tax wedges for couples with two children show a similar trend.

  16. Historical overview of spinal deformities in ancient Greece

    Science.gov (United States)

    Vasiliadis, Elias S; Grivas, Theodoros B; Kaspiris, Angelos

    2009-01-01

    Little is known about the history of spinal deformities in ancient Greece. The present study summarizes what we know today for diagnosis and management of spinal deformities in ancient Greece, mainly from the medical treatises of Hippocrates and Galen. Hippocrates, through accurate observation and logical reasoning was led to accurate conclusions firstly for the structure of the spine and secondly for its diseases. He introduced the terms kyphosis and scoliosis and wrote in depth about diagnosis and treatment of kyphosis and less about scoliosis. The innovation of the board, the application of axial traction and even the principle of trans-abdominal correction for correction of spinal deformities have their origin in Hippocrates. Galen, who lived nearly five centuries later impressively described scoliosis, lordosis and kyphosis, provided aetiologic implications and used the same principles with Hippocrates for their management, while his studies influenced medical practice on spinal deformities for more than 1500 years. PMID:19243609

  17. Historical overview of spinal deformities in ancient Greece

    Directory of Open Access Journals (Sweden)

    Kaspiris Angelos

    2009-02-01

    Full Text Available Abstract Little is known about the history of spinal deformities in ancient Greece. The present study summarizes what we know today for diagnosis and management of spinal deformities in ancient Greece, mainly from the medical treatises of Hippocrates and Galen. Hippocrates, through accurate observation and logical reasoning was led to accurate conclusions firstly for the structure of the spine and secondly for its diseases. He introduced the terms kyphosis and scoliosis and wrote in depth about diagnosis and treatment of kyphosis and less about scoliosis. The innovation of the board, the application of axial traction and even the principle of trans-abdominal correction for correction of spinal deformities have their origin in Hippocrates. Galen, who lived nearly five centuries later impressively described scoliosis, lordosis and kyphosis, provided aetiologic implications and used the same principles with Hippocrates for their management, while his studies influenced medical practice on spinal deformities for more than 1500 years.

  18. Energy consumption and economic growth: A causality analysis for Greece

    International Nuclear Information System (INIS)

    Tsani, Stela Z.

    2010-01-01

    This paper investigates the causal relationship between aggregated and disaggregated levels of energy consumption and economic growth for Greece for the period 1960-2006 through the application of a later development in the methodology of time series proposed by Toda and Yamamoto (1995). At aggregated levels of energy consumption empirical findings suggest the presence of a uni-directional causal relationship running from total energy consumption to real GDP. At disaggregated levels empirical evidence suggests that there is a bi-directional causal relationship between industrial and residential energy consumption to real GDP but this is not the case for the transport energy consumption with causal relationship being identified in neither direction. The importance of these findings lies on their policy implications and their adoption on structural policies affecting energy consumption in Greece suggesting that in order to address energy import dependence and environmental concerns without hindering economic growth emphasis should be put on the demand side and energy efficiency improvements.

  19. Online Communities: The Case of Immigrants in Greece

    Science.gov (United States)

    Panaretou, Ioannis; Karousos, Nikos; Kostopoulos, Ioannis; Foteinou, Georgia-Barbara; Pavlidis, Giorgos

    Immigrants in Greece are an increasing population, very often threatened by poverty and social exclusion. At the same time Greek government has no formal policy concerning their assimilation in Greek society and this situation generates multiple problems in both immigrants and native population. In this work we suggest that new technology can alleviate these effects and we present specific tools and methodologies adopted by ANCE, in order to support online communities and specifically immigrant communities in Greece. This approach has the potential to support immigrant communities' in terms of the organization of personal data, communication, and provision of a working space for dedicated use. The Information System's operational features are also presented, along with other characteristics and state-of-the-art features in order to propose a general direction to the design of online communities' mechanisms.

  20. Development of the Social Capital Questionnaire in Greece.

    Science.gov (United States)

    Kritsotakis, George; Koutis, Antonis D; Alegakis, Athanassios K; Philalithis, Anastas E

    2008-06-01

    The Greek version of the social capital questionnaire (SCQ-G) was evaluated in a sample of 521 adults drawn from three different urban areas in Greece. Exploratory factor analysis followed by multi-trait scaling yielded six factors: Participation in the Community, Feelings of Safety, Family/Friends Connections, Value of Life and Social Agency, Tolerance of Diversity, and Work Connections. The factor solution is similar to the patterns identified originally in Australia and the US. Variations suggest that social capital does not share the same structure in different countries. The SCQ-G is a useful scale to measure individual-level social capital in Greece. Social capital measurement tools should be validated in each cultural or national setting in which they are used.

  1. Urban wastewater and stormwater technologies in ancient Greece.

    Science.gov (United States)

    Angelakis, A N; Koutsoyiannis, D; Tchobanoglous, G

    2005-01-01

    The status of urban sewerage and stormwater drainage systems in ancient Greece is reviewed, based on the results of archaeological studies of the 20th century. Emphasis is given to the construction, operation, and management of sewerage and stormwater drainage systems during the Minoan period (2nd millennium B.C.). The achievements of this period in dealing with the hygienic and the functional requirements of palaces and cities, were so advanced that they can only be compared to modern urban water systems, developed in Europe and North America in the second half of the 19th century A.D. The advanced Minoan technologies were exported to all parts of Greece in later periods of the Greek civilization, i.e. in Mycenaean, Archaic, Classical, and Hellenistic periods.

  2. Adoption and use of e-invoicing in Greece

    International Nuclear Information System (INIS)

    Marinagi, C.; Trivellas, P.; Reklitis, Panagiotis; Skourlas, C.

    2015-01-01

    This paper investigates the adoption and use of electronic invoices (e-invoices) in Greek organizations. The study attempts to evaluate current practices applied in implementing e-invoicing. A field research has been conducted, which is based on a structured questionnaire. The target sample consisted of 42 Greek enterprises. The main issues of the investigation include the existing invoice processing practices, the barriers that prevent the extended adoption and use of e-invoicing, the observed benefits from e-invoicing implementation, and the strategic drivers for transition to e-invoicing. Currently, the use of e-invoicing in Greece is low. However, the research results testify that the adoption of e-invoicing in Greece is promising. Even though, a number of enterprises state that benefits of e-invoicing are not clear yet, the majority of enterprises agree that there are crucial financial priorities that e-invoicing is expected to support

  3. Implementation of the e-Bug Project in Greece.

    Science.gov (United States)

    Gennimata, Dimitra; Merakou, Kyriakoula; Barbouni, Anastasia; Kremastinou, Jenny

    2011-06-01

    The e-Bug pack and web site educational material has been translated and adapted to the Greek language and educational background, and implemented throughout Greece as a supplementary educational resource in elementary and junior high schools. Elementary and junior high school teachers in Greece have actively participated in the development of the e-Bug educational resource and supported the implementation of all e-Bug activities. Dissemination to all key national stakeholders has been undertaken, and endorsement has been obtained from educational and medical associations, societies and institutions. Independent evaluation has been carried out, as part of dissertation thesis projects, for postgraduate studies. The e-Bug educational resource provides all the essentials for the dissemination of good health behaviours in hygiene, monitoring the spread of infection and the prudent use of antibiotics, to the youth of this country. Its contribution is expected to be evident in the next adult generation.

  4. The 2006-2009 activity of the Ubinas volcano (Peru): Petrology of the 2006 eruptive products and insights into genesis of andesite magmas, magma recharge and plumbing system

    Science.gov (United States)

    Rivera, Marco; Thouret, Jean-Claude; Samaniego, Pablo; Le Pennec, Jean-Luc

    2014-01-01

    Following a fumarolic episode that started six months earlier, the most recent eruptive activity of the Ubinas volcano (south Peru) began on 27 March 2006, intensified between April and October 2006 and slowly declined until December 2009. The chronology of the explosive episode and the extent and composition of the erupted material are documented with an emphasis on ballistic ejecta. A petrological study of the juvenile products allows us to infer the magmatic processes related to the 2006-2009 eruptions of the andesitic Ubinas volcano. The juvenile magma erupted during the 2006 activity shows a homogeneous bulk-rock andesitic composition (56.7-57.6 wt.% SiO2), which belongs to a medium- to high-K calc-alkaline series. The mineral assemblage of the ballistic blocks and tephra consists of plagioclase > two-pyroxenes > Fe-Ti oxide and rare olivine and amphibole set in a groundmass of the same minerals with a dacitic composition (66-67 wt.% SiO2). Thermo-barometric data, based on two-pyroxene and amphibole stability, records a magma temperature of 998 ± 14 °C and a pressure of 476 ± 36 MPa. Widespread mineralogical and textural features point to a disequilibrium process in the erupted andesite magma. These features include inversely zoned "sieve textures" in plagioclase, inversely zoned clinopyroxene, and olivine crystals with reaction and thin overgrowth rims. They indicate that the pre-eruptive magmatic processes were dominated by recharge of a hotter mafic magma into a shallow reservoir, where magma mingling occurred and triggered the eruption. Prior to 2006, a probable recharge of a mafic magma produced strong convection and partial homogenization in the reservoir, as well as a pressure increase and higher magma ascent rate after four years of fumarolic activity. Mafic magmas do not prevail in the Ubinas pre-historical lavas and tephras. However, mafic andesites have been erupted during historical times (e.g. AD 1667 and 2006-2009 vulcanian eruptions). Hence

  5. A dynamic balance between magma supply and eruption rate at Kilauea volcano, Hawaii

    Science.gov (United States)

    Denlinger, R.P.

    1997-01-01

    The dynamic balance between magma supply and vent output at Kilauea volcano is used to estimate both the volume of magma stored within Kilauea volcano and its magma supply rate. Throughout most of 1991 a linear decline in volume flux from the Kupaianaha vent on Kilauea's east rift zone was associated with a parabolic variation in the elevation of Kilauea's summit as vent output initially exceeded then lagged behind the magma supply to the volcano. The correspondence between summit elevation and tilt established with over 30 years of data provided daily estimates of summit elevation in terms of summit tilt. The minimum in the parabolic variation in summit tilt and elevation (or zero elevation change) occurs when the magma supply to the reservoir from below the volcano equals the magma output from the reservoir to the surface, so that the magma supply rate is given by vent flux on that day. The measurements of vent flux and tilt establish that the magma supply rate to Kilauea volcano on June 19, 1991, was 217,000 ?? 10,000 m3/d (or 0.079 ?? 0.004 km3/yr). This is close to the average eruptive rate of 0.08 km3/yr between 1958 and 1984. In addition, the predictable response of summit elevation and tilt to each east rift zone eruption near Puu Oo since 1983 shows that summit deformation is also a measure of magma reservoir pressure. Given this, the correlation between the elevation of the Puu Oo lava lake (4 km uprift of Kupaianaha and 18 km from the summit) and summit tilt provides an estimate for magma pressure changes corresponding to summit tilt changes. The ratio of the change in volume to the change in reservoir pressure (dV/dP) during vent activity may be determined by dividing the ratio of volume erupted to change in summit tilt (dV/dtilt) by the ratio of pressure change to change in summit tilt (dP/dtilt). This measure of dV/dP, when combined with laboratory measurements of the bulk modulus of tholeitic melt, provides an estimate of 240 ?? 50 km3 for the volume

  6. Enhancement of eruption explosivity by heterogeneous bubble nucleation triggered by magma mingling.

    Science.gov (United States)

    Paredes-Mariño, Joali; Dobson, Katherine J; Ortenzi, Gianluigi; Kueppers, Ulrich; Morgavi, Daniele; Petrelli, Maurizio; Hess, Kai-Uwe; Laeger, Kathrin; Porreca, Massimiliano; Pimentel, Adriano; Perugini, Diego

    2017-12-04

    We present new evidence that shows magma mingling can be a key process during highly explosive eruptions. Using fractal analysis of the size distribution of trachybasaltic fragments found on the inner walls of bubbles in trachytic pumices, we show that the more mafic component underwent fracturing during quenching against the trachyte. We propose a new mechanism for how this magmatic interaction at depth triggered rapid heterogeneous bubble nucleation and growth and could have enhanced eruption explosivity. We argue that the data support a further, and hitherto unreported contribution of magma mingling to highly explosive eruptions. This has implications for hazard assessment for those volcanoes in which evidence of magma mingling exists.

  7. [The health of migrants at the Greece-Macedonia border].

    Science.gov (United States)

    Moutamalle, Raphaël

    2016-01-01

    At the border between Greece and Macedonia, a transit camp for refugees is turning into a permanent camp. The management of the health emergency is assured by international teams from several humanitarian organisations, including the French Red Cross. The organisation of the care team, the cultural differences and the lack of resources are just some of the factors to be considered. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  8. Evaluating Renewable Groundwater Stress with GRACE data in Greece

    Science.gov (United States)

    Lakshmi, V.; Gemitzi, A.

    2016-12-01

    Groundwater is a resilient water source and its importance as a fundamental resource is even greater in times of drought where groundwater stress conditions are greatest for areas like Mediterranean and adverse climate change effects are expected. The present study evaluates Renewable Groundwater Stress (RGS) as the ratio of groundwater use to groundwater availability, quantifying use as the trend in GRACE-derived subsurface anomalies (ΔGWtrend) and renewable groundwater availability as mean annual recharge. Estimates for mean annual recharge were used from groundwater studies conducted for the various regions in Greece, mainly in the form of numerical models. Our results highlighted two RGS regimes in Greece out of the four characteristic stress regimes, i.e. Overstressed, Variable Stress, Human-Dominated Stress and Unstressed, defined as a function of the sign of use and the sign of groundwater availability (positive or negative). Variable Stress areas are found in central Greece (Thessaly region), where intense agricultural activities take place, with negative ΔGWtrend values combined with positive mean annual recharge rates. RGS values range from -0.05 - 0, indicating however a low impact area. Within this region, adverse effects of groundwater overexploitation are already evident, based on the negative GRACE anomalies, recharge however still remains positive, amending the adverse over pumping impacts. The rest of Greek aquifers fall within the unstressed category, with RGS values from 0.02 - 0.05, indicating that the rate of use is less than the natural recharge rate. The highest Unstressed RGS values are observed in Crete Island and in Northeastern Greece. However, the case of Crete is highly uncertain, as precipitation and recharge in this area demonstrate exceptionally high variability and the coarse resolution of GRACE results does not allow for reliable estimates.

  9. Periodontal Reasons for Tooth Extraction in Adult Population in Greece

    OpenAIRE

    Chrysanthakopoulos, Nikolaos A.

    2010-01-01

    Aim: The aim of this study was to investigate the prevalence of permanent teeth extracted due to periodontal disease and its relation to several aspects such as age, gender and type of extracted teeth due to periodontal and non-periodontal reasons, among patients attending a private practice. Material and Methods: Study population consisted of 600 patients, 270 males and 330 females, aged 18 to 74 years from a private practice in Greece. The reasons for extractions of teeth in the sample for ...

  10. The interdependence of major european stock markets: evidence for Greece

    OpenAIRE

    Καινούργιος, Δημήτριος Φ.; Σαμίτας, Αριστείδης Γ.

    2003-01-01

    This paper provides new evidence on the relationship between the Greek "blue chip" stock market and the six relative European markets by applying cointegration tests. The time period examined is 1998 to 2000, which marks the entry of Greece to the European Exchange Rates Mechanism II. The empirical results indicate that the Athens Stock Exchange has no considerable links, except for one case, with any other European developed markets examined. These findings have some significa...

  11. Chewing lice from wild birds in northern Greece.

    Science.gov (United States)

    Diakou, Anastasia; Pedroso Couto Soares, José Bernardo; Alivizatos, Haralambos; Panagiotopoulou, Maria; Kazantzidis, Savas; Literák, Ivan; Sychra, Oldřich

    2017-10-01

    Greece represents an important area for wild birds due to its geographical position and habitat diversity. Although the bird species in Greece are well recorded, the information about the chewing lice that infest them is practically non-existent. Thus, the aim of the present study was to record the species of lice infesting wild birds in northern Greece and furthermore, to associate the infestation prevalence with factors such as the age, sex, migration and social behaviour of the host as well as the time of the year. In total 729 birds, (belonging to 9 orders, 32 families and 68 species) were examined in 7 localities of northern Greece, during 9 ringing sessions from June 2013 until October 2015. Eighty (11%) of the birds were found to be infested with lice. In 31 different bird species, 560 specimens of lice, belonging to 33 species were recorded. Mixed infestations were recorded in 11 cases where birds were infested with 2-3 different lice species. Four new host-parasite associations were recorded i.e. Menacanthus curuccae from Acrocephalus melanopogon, Menacanthus agilis from Cettia cetti, Myrsidea sp. from Acrocephalus schoenobaenus, and Philopretus citrinellae from Spinus spinus. Moreover, Menacanthus sinuatus was detected on Poecile lugubris, rendering this report the first record of louse infestation in this bird species. The statistical analysis of the data collected showed no association between parasitological parameters (prevalence, mean and median intensity and mean abundance) in two different periods of the year (breeding vs post-breeding season). However, there was a statistically significant difference in the prevalence of infestation between a) migrating and sedentary passerine birds (7.4% vs 13.2%), b) colonial and territorial birds (54.5% vs 9.6%), and c) female and male birds in breeding period (2.6% vs 15.6%). Copyright © 2017. Published by Elsevier B.V.

  12. Capital mobility and macroeconomic volatility: evidence from Greece

    OpenAIRE

    Anastasios, Pappas

    2010-01-01

    This paper focuses on the impact of full capital account liberalization on macroeconomic volatility in Greece. According to the standard neoclassical model, such liberalization is to be desired because, among other advantages, it may reduce macroeconomic volatility. The link between macroeconomic volatility and capital account openness in the Greek economy is investigated by applying a simple three-month rolling standard deviation of real GDP growth and real final (total) consumption growth c...

  13. Smoking cessation delivery by general practitioners in Crete, Greece.

    Science.gov (United States)

    Girvalaki, Charis; Papadakis, Sophia; Vardavas, Constantine; Petridou, Eleni; Pipe, Andrew; Lionis, Christos

    2018-06-01

    Tobacco dependence treatment in clinical settings is of prime public health importance, especially in Greece, a country experiencing one of the highest rates of tobacco use in Europe. Our study aimed to examine the characteristics of tobacco users and document rates of tobacco treatment delivery in general practice settings in Crete, Greece. A cross-sectional sample of patients (n = 2, 261) was screened for current tobacco use in 25 general practices in Crete, Greece in 2015/16. Current tobacco users completed a survey following their clinic appointment that collected information on patient characteristics and rates at which the primary care physician delivered tobacco treatment using the evidence-based 4 A's (Ask, Advise, Assist, Arrange) model during their medical appointment and over the previous 12-month period. Multi-level modeling was used to analyze data and examine predictors of 4 A's delivery. Tobacco use prevalence was 38% among all patients screened. A total of 840 tobacco users completed the study survey [mean age 48.0 (SD 14.5) years, 57.6% male]. Approximately, half of the tobacco users reported their general practitioner 'asked' about their tobacco use and 'advised' them to quit smoking. Receiving 'assistance' with quitting (15.7%) and 'arranging' follow-up support (<3%) was infrequent. Patient education, presence of smoking-related illness, a positive screen for anxiety or depression and the type of medical appointment were associated with 4 A's delivery. Given the fundamental importance of addressing tobacco treatment, increasing the rates of 4 A's treatment in primary care settings in Greece is an important target for improving patient care.

  14. Educational segregation and the gender wage gap in Greece

    OpenAIRE

    Livanos, Ilias; Pouliakas, Konstantinos

    2012-01-01

    Purpose\\ud To investigate the extent to which differences in the subject of degree studied by male and female university graduates contributes to the gender pay gap in Greece, an EU country with historically large gender discrepancies in earnings and occupational segregation. In addition, to explore the reasons underlying the distinct educational choices of men and women, with particular emphasis on the role of wage uncertainty.\\ud \\ud Design/methodology/approach\\ud Using micro-data from the ...

  15. Possible Rickettsia massiliae Infection in Greece: an Imported Case.

    Science.gov (United States)

    Chochlakis, Dimosthenis; Bongiorni, Christine; Partalis, Nikolaos; Tselentis, Yannis; Psaroulaki, Anna

    2016-07-22

    Tick-borne rickettsioses are endemic in Greece; however, until recently, only Rickettsia typhi and R. conorii were tested routinely in human samples arriving at the National Reference Center. During the last few years, the identification of different rickettsia species in ticks led to the introduction of other spotted fever group rickettsiae in routine analysis. Under the new scheme, R. massiliae is now tested routinely in human samples; herein, we describe a human case of this infection.

  16. Exergy analysis of the energy use in Greece

    DEFF Research Database (Denmark)

    Koroneos, C.J.; Nanaki, E.A.; Xydis, George

    2011-01-01

    In this work, an analysis is being done on the concept of energy and exergy utilization and an application to the residential and industrial sector of Greece. The energy and exergy flows over the period from 1990 to 2004 were taken into consideration. This period was chosen based on the data...... of the energy use in various economy sectors. These standards could be utilized by energy policy makers....

  17. Carbon Footprint Analysis of Municipalities – Evidence from Greece

    Directory of Open Access Journals (Sweden)

    K. Angelakoglou

    2015-11-01

    Full Text Available The economical crisis that hit Greece after 2009, significantly affected its energy consumption profile due to the increased price of domestic heating oil and gasoline. The specific study aims at the quantification of the carbon dioxide emissions in municipal level due to energy and fuel consumption. Three different municipalities in North Greece (Kavala, Alexandroupolis and Drama were assessed with the application of three different carbon footprint estimation approaches in each one of them, including two life cycle assessment methods. Results ranged from 511,799 to 571,000, 435,250 to 489,000 and 355,207 to 398,000 tons CO2 and tons CO2-eq. for Kavala, Alexandroupolis and Drama respectively. The analysis per energy type indicated the electrical energy consumption as the key factor affecting the results due to the relatively high CO2 emission coefficient of the electricity produced in Greece. The analysis per sector indicated that a percentage of nearly 75% of the total carbon footprint is assigned to the building sector whereas the private and commercial transport is accountable for the rest. Municipal activities (buildings, facilities, lighting and fleet contributed to a small percentage to the total carbon footprint (approx. 3-8%.

  18. Spatial variability and trends of the rain intensity over Greece

    Science.gov (United States)

    Kambezidis, H. D.; Larissi, I. K.; Nastos, P. T.; Paliatsos, A. G.

    2010-07-01

    In this study, the spatial and temporal variability of the mean annual rain intensity in Greece are examined during a 41-year period (1962-2002). The meteorological datasets concern monthly rain amounts (mm) and the respective monthly durations (h) recorded at thirty two meteorological stations of the Hellenic National Meteorological Service, which are uniformly distributed on Greek territory, in order to calculate the mean monthly rain intensity. All the rain time series used in the analysis were tested by the application of the short-cut Bartlett test of homogeneity. The spatial distribution of the mean annual rain intensity is studied using the Kriging interpolation method, while the temporal variability, concerning the mean annual rain intensity trends along with their significance (Mann-Kendall test), is analysed. The findings of the analysis show that statistically significant negative trends (95% confidence level) appear mainly in the west sub-regions of Greece, while statistically significant positive trends (95% confidence level) appear in the wider area of Athens and the complex of Cyclades Islands. Further analysis concerning the seasonal rain intensity is needed, because there are different seasonal patterns, taking into account that, convective rain in Greece occurs mainly within the summer season.

  19. Application of the Standardized Precipitation Index (SPI in Greece

    Directory of Open Access Journals (Sweden)

    Christos A. Karavitis

    2011-08-01

    Full Text Available The main premise of the current effort is that the use of a drought index, such as Standardized Precipitation Index (SPI, may lead to a more appropriate understanding of drought duration, magnitude and spatial extent in semi-arid areas like Greece. The importance of the Index may be marked in its simplicity and its ability to identify the beginning and end of a drought event. Thus, it may point towards drought contingency planning and through it to drought alert mechanisms. In this context, Greece, as it very often faces the hazardous impacts of droughts, presents an almost ideal case for the SPI application. The present approach examines the SPI drought index application for all of Greece and it is evaluated accordingly by historical precipitation data. Different time series of data from 46 precipitation stations, covering the period 1947–2004, and for time scales of 1, 3, 6, 12 and 24 months, were used. The computation of the index was achieved by the appropriate usage of a pertinent software tool. Then, spatial representation of the SPI values was carried out with geo-statistical methods using the SURFER 9 software package. The results underline the potential that the SPI usage exhibits in a drought alert and forecasting effort as part of a drought contingency planning posture.

  20. Genetic characterisation of Taenia multiceps cysts from ruminants in Greece.

    Science.gov (United States)

    Al-Riyami, Shumoos; Ioannidou, Evi; Koehler, Anson V; Hussain, Muhammad H; Al-Rawahi, Abdulmajeed H; Giadinis, Nektarios D; Lafi, Shawkat Q; Papadopoulos, Elias; Jabbar, Abdul

    2016-03-01

    This study was designed to genetically characterise the larval stage (coenurus) of Taenia multiceps from ruminants in Greece, utilising DNA regions within the cytochrome c oxidase subunit 1 (partial cox1) and NADH dehydrogenase 1 (pnad1) mitochondrial (mt) genes, respectively. A molecular-phylogenetic approach was used to analyse the pcox1 and pnad1 amplicons derived from genomic DNA samples from individual cysts (n=105) from cattle (n=3), goats (n=5) and sheep (n=97). Results revealed five and six distinct electrophoretic profiles for pcox1 and pnad1, respectively, using single-strand conformation polymorphism. Direct sequencing of selected amplicons representing each of these profiles defined five haplotypes each for pcox1 and pnad1, among all 105 isolates. Phylogenetic analysis of individual sequence data for each locus, including a range of well-defined reference sequences, inferred that all isolates of T. multiceps cysts from ruminants in Greece clustered with previously published sequences from different continents. The present study provides a foundation for future large-scale studies on the epidemiology of T. multiceps in ruminants as well as dogs in Greece. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Political determinants of social expenditures in Greece: an empirical analysis

    Directory of Open Access Journals (Sweden)

    Ebru Canikalp

    2017-09-01

    Full Text Available A view prominently expounded is that the interaction between the composition and the volume of public expenditures is directly affected by political, institutional, psephological and ideological indicators. A crucial component of public expenditures, social expenditures play an important role in the economy as they directly and indirectly affect the distribution of income and wealth. Social expenditures aim at reallocating income and wealth unequal distribution. These expenditures comprise cash benefits, direct in-kind provision of goods and services, and tax breaks with social purposes.The aim of this study is to determine the relationship between political structure, i.e. government fragmentation, ideological composition, elections and so on, and the social expenditures in Greece. Employing data from the Comparative Political Dataset (CPDS and the OECD Social Expenditure Database (SOCX, a time series analysis was conducted for Greece for the 1980-2014 period. The findings of the study indicate that voter turnout, spending on the elderly population and the number of government changes have positive and statistically significant effects on social expenditures in Greece while debt stock and cabinet composition have negative effects.

  2. CURRENT ENVIRONMENT FOR INTRODUCING HEALTH TECHNOLOGY ASSESSMENT IN GREECE.

    Science.gov (United States)

    Kani, Chara; Kourafalos, Vasilios; Litsa, Panagiota

    2017-01-01

    The aim of this study was to describe the current regulatory environment in Greece to evaluate the potential introduction of health technology assessment (HTA) for medicinal products for human use. Data sources consist of national legislation on pricing and reimbursement of health technologies to identify the potential need of establishing HTA and its relevant structure. The pricing procedure regarding medicinal products for human use is based on an external reference pricing mechanism which considers the average of the three lowest Euorpean Union prices. Currently, a formal HTA procedure has not been applied in Greece, and the only prerequisite used for the reimbursement of medicinal products for human use is their inclusion in the Positive Reimbursement List. To restrict pharmaceutical expenditure, a variety of measures-such as clawback mechanisms, rebates, monthly budget caps per physician, generics penetration targeting-have been imposed, aiming mainly to regulate the price level rather than control the introduction of medicinal products for human use in the Greek pharmaceutical market. Greece has the opportunity to rapidly build capacity, implement, and take advantage of the application of HTA mechanisms by clearly defining the goals, scope, systems, context, stakeholders, and methods that will be involved in the local HTA processes, taking into account the country's established e-prescription system and the recently adapted legislative framework.

  3. Wastewater Recycling in Greece: The Case of Thessaloniki

    Directory of Open Access Journals (Sweden)

    Andreas Ilias

    2014-05-01

    Full Text Available In Greece, and particularly in many southeastern and island areas, there is severe pressure on water resources, further exacerbated by the high demand of water for tourism and irrigation in summertime. The integration of treated wastewater into water resources management is of paramount importance to meet future demands. Despite this need, only a few projects of effluent reuse have been implemented, most of them being pilot projects of crop or landscape irrigation. The most important projects which are currently in practice are those of Thessaloniki, Chalkida, Malia, Livadia, Amfisa, Kalikratia, and Chersonissos. In Thessaloniki, at the most important wastewater reuse site, the secondary effluent of the city’s Waste Water Treatment Plant (WWTP (165,000 m3/day is used for agricultural irrigation after mixing with freshwater at a 1:5 ratio. The main crops irrigated are rice, corn, alfalfa and cotton. A few other projects are under planning, such as that at Iraklion, Agios Nikolaos and several island regions. Finally, it should be mentioned that there are several cases of indirect reuse, especially in central Greece. However, the reuse potential in Greece is limited, since effluent from Athens’s WWTP, serving approximately half of the country’s population, is not economically feasible due to the location of the plant.

  4. Rickettsia species in human-parasitizing ticks in Greece.

    Science.gov (United States)

    Papa, Anna; Xanthopoulou, Kyriaki; Kotriotsiou, Tzimoula; Papaioakim, Miltiadis; Sotiraki, Smaragda; Chaligiannis, Ilias; Maltezos, Efstratios

    2016-05-01

    Ticks serve as vectors and reservoirs for a variety of bacterial, viral and protozoan pathogens affecting humans and animals. Unusual increased tick aggressiveness was observed in 2008-2009 in northeastern Greece. The aim of the study was to check ticks removed from persons during 2009 for infection with Rickettsia species. A total of 159 ticks were removed from 147 persons who sought medical advice in a hospital. Tick identification was performed morphologically using taxonomic keys. DNA was extracted from each individual tick and a PCR assay targeting the rickettsial outer membrane protein A gene of Rickettsia spp. was applied. Most of the adult ticks (132/153, 86.3%) were Rhipicephalus sanguineus. Rickettsiae were detected in 23 of the 153 (15.0%) adult ticks. Five Rickettsiae species were identified: R. aeschlimannii, R. africae (n=6), R. massilae (4), R. monacensis (1), and Candidatus R. barbariae (1). To our knowledge, this is the first report of R. africae, R. monacensis, and Candidatus R. barbariae in Greece. Several Rickettsia species were identified in ticks removed from humans in Greece, including those that are prevalent in northern and southern latitudes. © The Author 2016. Published by Oxford University Press on behalf of Royal Society of Tropical Medicine and Hygiene. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  5. Bioenergy in Greece: Policies, diffusion framework and stakeholder interactions

    International Nuclear Information System (INIS)

    Panoutsou, Calliope

    2008-01-01

    The paper provides a high-level scene setting analysis to understand the policy context in which the diffusion of bioenergy takes place in Greece and analysis of the perceptions of the key stakeholders at local and national levels. It is divided into six sections. Firstly the framework conditions for biomass heat and electricity generation in Greece are presented. In the second section, the policy context is set in order to identify the key support mechanisms for bioenergy in the country. The third section presents an outline of the diffusion of bioenergy in terms of key groups involved as well as key factors affecting the planning and implementation of a bioenergy scheme at local/regional and national levels. The fourth section reviews the perception of key stakeholders towards bioenergy/biofuels schemes at national level based on national networks. The fifth section focuses on a case study region (Rodopi, northern Greece) and provides an in-depth analysis for the perception of the main local actors (farmers and end users) based on structured questionnaire interviews. The final section provides the main conclusions from the surveys and draws a set of recommendations for the integration of bioenergy schemes into the Greek energy system

  6. Volatile element loss during planetary magma ocean phases

    Science.gov (United States)

    Dhaliwal, Jasmeet K.; Day, James M. D.; Moynier, Frédéric

    2018-01-01

    Moderately volatile elements (MVE) are key tracers of volatile depletion in planetary bodies. Zinc is an especially useful MVE because of its generally elevated abundances in planetary basalts, relative to other MVE, and limited evidence for mass-dependent isotopic fractionation under high-temperature igneous processes. Compared with terrestrial basalts, which have δ66Zn values (per mille deviation of the 66Zn/64Zn ratio from the JMC-Lyon standard) similar to some chondrite meteorites (∼+0.3‰), lunar mare basalts yield a mean δ66Zn value of +1.4 ± 0.5‰ (2 st. dev.). Furthermore, mare basalts have average Zn concentrations ∼50 times lower than in typical terrestrial basaltic rocks. Late-stage lunar magmatic products, including ferroan anorthosite, Mg- and Alkali-suite rocks have even higher δ66Zn values (+3 to +6‰). Differences in Zn abundance and isotopic compositions between lunar and terrestrial rocks have previously been interpreted to reflect evaporative loss of Zn, either during the Earth-Moon forming Giant Impact, or in a lunar magma ocean (LMO) phase. To explore the mechanisms and processes under which volatile element loss may have occurred during a LMO phase, we developed models of Zn isotopic fractionation that are generally applicable to planetary magma oceans. Our objective was to identify conditions that would yield a δ66Zn signature of ∼+1.4‰ within the lunar mantle. For the sake of simplicity, we neglect possible Zn isotopic fractionation during the Giant Impact, and assumed a starting composition equal to the composition of the present-day terrestrial mantle, assuming both the Earth and Moon had zinc 'consanguinity' following their formation. We developed two models: the first simulates evaporative fractionation of Zn only prior to LMO mixing and crystallization; the second simulates continued evaporative fractionation of Zn that persists until ∼75% LMO crystallization. The first model yields a relatively homogenous bulk solid

  7. NVP melt/magma viscosity: insight on Mercury lava flows

    Science.gov (United States)

    Rossi, Stefano; Morgavi, Daniele; Namur, Olivier; Vetere, Francesco; Perugini, Diego; Mancinelli, Paolo; Pauselli, Cristina

    2016-04-01

    After more than four years of orbiting Mercury, NASA's MESSENGER spacecraft came to an end in late April 2015. MESSENGER has provided many new and surprising results. This session will again highlight the latest results on Mercury based on MESSENGER observations or updated modelling. The session will further address instrument calibration and science performance both retrospective on MESSENGER and on the ESA/JAXA BepiColombo mission. Papers covering additional themes related to Mercury are also welcomed. Please be aware that this session will be held as a PICO session. This will allow an intensive exchange of expertise and experience between the individual instruments and mission. NVP melt/magma viscosity: insight on Mercury lava flows S. Rossi1, D. Morgavi1, O. Namur2, D. Perugini1, F.Vetere1, P. Mancinelli1 and C. Pauselli1 1 Dipartimento di Fisica e Geologia, Università di Perugia, piazza Università 1, 06123 Perugia, Italy 2 Uni Hannover Institut für Mineralogie, Leibniz Universität Hannover, Callinstraβe 3, 30167 Hannover, Germany In this contribution we report new measurements of viscosity of synthetic komatitic melts, used the behaviour of silicate melts erupted at the surface of Mercury. Composition of Mercurian surface magmas was calculated using the most recent maps produced from MESSENGER XRS data (Weider et al., 2015). We focused on the northern hemisphere (Northern Volcanic Province, NVP, the largest lava flow on Mercury and possibly in the Solar System) for which the spatial resolution of MESSENGER measurements is high and individual maps of Mg/Si, Ca/Si, Al/Si and S/Si were combined. The experimental starting material contains high Na2O content (≈7 wt.%) that strongly influences viscosity. High temperature viscosity measurements were carried out at 1 atm using a concentric cylinder apparatus equipped with an Anton Paar RheolabQC viscometer head at the Department of Physics and Geology (PVRG_lab) at the University of Perugia (Perugia, Italy

  8. Barium isotope geochemistry of subduction-zone magmas

    Science.gov (United States)

    Yu, H.; Nan, X.; Huang, J.; Wörner, G.; Huang, F.

    2017-12-01

    Subduction zones are crucial tectonic setting to study material exchange between crust and mantle, mantle partial melting with fluid addition, and formation of ore-deposits1-3. The geochemical characteristics of arc lavas from subduction zones are different from magmas erupted at mid-ocean ridges4, because there are addition of fluids/melts from subducted AOC and its overlying sediments into their source regions in the sub-arc mantle4. Ba is highly incompatible during mantle melting5, and it is enriched in crust (456 ppm)6 relative to the mantle (7.0 ppm)7. The subducted sediments are also enriched in Ba (776 ppm of GLOSS)8. Moreover, because Ba is fluid soluble during subduction, it has been used to track contributions of subduction-related fluids to arc magmas9 or recycled sediments to the mantle10-11. To study the Ba isotope fractionation behavior during subduction process, we analyzed well-characterized, chemically-diverse arc lavas from Central American, Kamchatka, Central-Eastern Aleutian, and Southern Lesser Antilles. The δ137/134Ba of Central American arc lavas range from -0.13 to 0.24‰, and have larger variation than the arc samples from other locations. Except one sample from Central-Eastern Aleutian arc with obviously heavy δ137/134Ba values (0.27‰), all other samples from Kamchatka, Central-Eastern Aleutian, Southern Lesser Antilles arcs are within the range of OIB. The δ137/134Ba is not correlated with the distance to trench, partial melting degrees (Mg#), or subducting slab-derived components. The samples enriched with heavy Ba isotopes have low Ba contents, indicating that Ba isotopes can be fractionated at the beginning of dehydration process with small amount of Ba releasing to the mantle wedge. With the dehydration degree increasing, more Ba of the subducted slab can be added to the source of arc lavas, likely homogenizing the Ba isotope signatures. 1. Rudnick, R., 1995 Nature; 2. Tatsumi, Y. & Kogiso, T., 2003; 3. Sun, W., et al., 2015 Ore

  9. His Excellency Mr Alexandros Alexandris Ambassador, Permanent Representative of Greece to the United Nations Office at Geneva and other international organizations in Switzerland and Officials from the East Macedonia and Thrace Region Greece

    CERN Multimedia

    Jean-Claude Gadmer

    2013-01-01

    His Excellency Mr Alexandros Alexandris Ambassador, Permanent Representative of Greece to the United Nations Office at Geneva and other international organizations in Switzerland and Officials from the East Macedonia and Thrace Region Greece

  10. A heuristic expert system for forest fire guidance in Greece.

    Science.gov (United States)

    Iliadis, Lazaros S; Papastavrou, Anastasios K; Lefakis, Panagiotis D

    2002-07-01

    Forests and forestlands are common inheritance for all Greeks and a piece of the national wealth that must be handed over to the next generations in the best possible condition. After 1974, Greece faces a severe forest fire problem and forest fire forecasting is the process that will enable the Greek ministry of Agriculture to reduce the destruction. This paper describes the basic design principles of an Expert System that performs forest fire forecasting (for the following fire season) and classification of the prefectures of Greece into forest fire risk zones. The Expert system handles uncertainty and uses heuristics in order to produce scenarios based on the presence or absence of various qualitative factors. The initial research focused on the construction of a mathematical model which attempted to describe the annual number of forest fires and burnt area in Greece based on historical data. However this has proven to be impossible using regression analysis and time series. A closer analysis of the fire data revealed that two qualitative factors dramatically affect the number of forest fires and the hectares of burnt areas annually. The first is political stability and national elections and the other is drought cycles. Heuristics were constructed that use political stability and drought cycles, to provide forest fire guidance. Fuzzy logic was applied to produce a fuzzy expected interval for each prefecture of Greece. A fuzzy expected interval is a narrow interval of values that best describes the situation in the country or a part of the country for a certain time period. A successful classification of the prefectures of Greece in forest fire risk zones was done by the system, by comparing the fuzzy expected intervals to each other. The system was tested for the years 1994 and 1995. The testing has clearly shown that the system can predict accurately, the number of forest fires for each prefecture for the following year. The average accuracy was as high as 85

  11. Magma degassing triggered by static decompression at Kīlauea Volcano, Hawai‘i

    Science.gov (United States)

    Poland, Michael P.; Jeff, Sutton A.; Gerlach, Terrence M.

    2009-01-01

    During mid-June 2007, the summit of Kīlauea Volcano, Hawai‘i, deflated rapidly as magma drained from the subsurface to feed an east rift zone intrusion and eruption. Coincident with the deflation, summit SO2 emission rates rose by a factor of four before decaying to background levels over several weeks. We propose that SO2 release was triggered by static decompression caused by magma withdrawal from Kīlauea's shallow summit reservoir. Models of the deflation suggest a pressure drop of 0.5–3 MPa, which is sufficient to trigger exsolution of the observed excess SO2 from a relatively small volume of magma at the modeled source depth beneath Kīlauea's summit. Static decompression may also explain other episodes of deflation accompanied by heightened gas emission, including the precursory phases of Kīlauea's 2008 summit eruption. Hazards associated with unexpected volcanic gas emission argue for increased awareness of magma reservoir pressure fluctuations.

  12. A basal magma ocean dynamo to explain the early lunar magnetic field

    Science.gov (United States)

    Scheinberg, Aaron L.; Soderlund, Krista M.; Elkins-Tanton, Linda T.

    2018-06-01

    The source of the ancient lunar magnetic field is an unsolved problem in the Moon's evolution. Theoretical work invoking a core dynamo has been unable to explain the magnitude of the observed field, falling instead one to two orders of magnitude below it. Since surface magnetic field strength is highly sensitive to the depth and size of the dynamo region, we instead hypothesize that the early lunar dynamo was driven by convection in a basal magma ocean formed from the final stages of an early lunar magma ocean; this material is expected to be dense, radioactive, and metalliferous. Here we use numerical convection models to predict the longevity and heat flow of such a basal magma ocean and use scaling laws to estimate the resulting magnetic field strength. We show that, if sufficiently electrically conducting, a magma ocean could have produced an early dynamo with surface fields consistent with the paleomagnetic observations.

  13. The Lunar Magma Ocean (LMO) Paradigm Versus the Realities of Lunar Anorthosites

    Science.gov (United States)

    Treiman, A. H.; Gross, J.

    2018-05-01

    The paradigm of the Lunar Magma Ocean (LMO) is inconsistent with much chemical and compositional data on lunar anorthosites. The paradigm of serial anorthosite diapirism is more consistent, though not a panacea.

  14. Magma flow instability and cyclic activity at soufriere hills volcano, montserrat, british west indies

    Science.gov (United States)

    Voight; Sparks; Miller; Stewart; Hoblitt; Clarke; Ewart; Aspinall; Baptie; Calder; Cole; Druitt; Hartford; Herd; Jackson; Lejeune; Lockhart; Loughlin; Luckett; Lynch; Norton; Robertson; Watson; Watts; Young

    1999-02-19

    Dome growth at the Soufriere Hills volcano (1996 to 1998) was frequently accompanied by repetitive cycles of earthquakes, ground deformation, degassing, and explosive eruptions. The cycles reflected unsteady conduit flow of volatile-charged magma resulting from gas exsolution, rheological stiffening, and pressurization. The cycles, over hours to days, initiated when degassed stiff magma retarded flow in the upper conduit. Conduit pressure built with gas exsolution, causing shallow seismicity and edifice inflation. Magma and gas were then expelled and the edifice deflated. The repeat time-scale is controlled by magma ascent rates, degassing, and microlite crystallization kinetics. Cyclic behavior allows short-term forecasting of timing, and of eruption style related to explosivity potential.

  15. Role of syn-eruptive plagioclase disequilibrium crystallization in basaltic magma ascent dynamics.

    Science.gov (United States)

    La Spina, G; Burton, M; De' Michieli Vitturi, M; Arzilli, F

    2016-12-12

    Timescales of magma ascent in conduit models are typically assumed to be much longer than crystallization and gas exsolution for basaltic eruptions. However, it is now recognized that basaltic magmas may rise fast enough for disequilibrium processes to play a key role on the ascent dynamics. The quantification of the characteristic times for crystallization and exsolution processes are fundamental to our understanding of such disequilibria and ascent dynamics. Here we use observations from Mount Etna's 2001 eruption and a magma ascent model to constrain timescales for crystallization and exsolution processes. Our results show that plagioclase reaches equilibrium in 1-2 h, whereas ascent times were magma ascent rate and disequilibrium crystallization and exsolution plays a key role in controlling eruption dynamics in basaltic volcanism.

  16. Sensitivity of seafloor bathymetry to climate-driven fluctuations in mid-ocean ridge magma supply.

    Science.gov (United States)

    Olive, J-A; Behn, M D; Ito, G; Buck, W R; Escartín, J; Howell, S

    2015-10-16

    Recent studies have proposed that the bathymetric fabric of the seafloor formed at mid-ocean ridges records rapid (23,000 to 100,000 years) fluctuations in ridge magma supply caused by sealevel changes that modulate melt production in the underlying mantle. Using quantitative models of faulting and magma emplacement, we demonstrate that, in fact, seafloor-shaping processes act as a low-pass filter on variations in magma supply, strongly damping fluctuations shorter than about 100,000 years. We show that the systematic decrease in dominant seafloor wavelengths with increasing spreading rate is best explained by a model of fault growth and abandonment under a steady magma input. This provides a robust framework for deciphering the footprint of mantle melting in the fabric of abyssal hills, the most common topographic feature on Earth. Copyright © 2015, American Association for the Advancement of Science.

  17. Earthquake swarms reveal submarine magma unrest induced by distant mega-earthquakes: Andaman Sea region

    Czech Academy of Sciences Publication Activity Database

    Špičák, Aleš; Vaněk, Jiří

    2016-01-01

    Roč. 116, February (2016), s. 155-163 ISSN 1367-9120 Institutional support: RVO:67985530 Keywords : earthquake swarms * magma migration * submarine volcanic arc Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 2.335, year: 2016

  18. Investigation of orography impact on extreme dry spells over Greece

    Science.gov (United States)

    Oikonomou, C.; Flocas, H.; Manola, I.; Hatzaki, M.; Asimakopoulos, D. N.

    2009-04-01

    Precipitation regime over Greece is controlled by the atmospheric circulation, orography sea surface temperature distribution and land/sea interaction. Previous studies have shown that the precipitation amounts are increased in Western Greece, which is located in the upstream side of the largest mountain range of the central mainland. Furthermore, the longest dry spells were identified in south eastern part of Greece during summer and in northern Greek area during winter. The objective of this study is to investigate the impact of topography on prolonged dry periods over Greece, using the third generation hydrostatic Regional Climate Model RegCM3, which shows a noticeable improvement in the representation of the surface hydrological cycle in mountainous regions. More specifically, an attempt is made to study the distribution of prolonged dry spells during two seasons, summer of 1993 and winter of 1989, over the Greek area, under two different simulation scenarios: the first employs the real orography of the Greek area while in the second one the orography is eliminated, by transforming the models terrain code. Both simulation experiments were conducted with the high spatial resolution of 10 Km, while the MIT-Emanuel Convective Precipitation Scheme was selected for the computation of convective precipitation, as it offers more physical representation of convection compared to the other oldest schemes of RegCM. The model was firstly validated through comparisons of the model outputs with observed precipitation amount data, employing 20 stations over Greece for the two selected seasons. The validation demonstrated that the model can simulate precipitation amount quite well over the Greek area, except for the south Dodecanese Islands, where precipitation is underestimated, and the eastern continental Greece, where the daily precipitation is overestimated. For the identification of the extreme dry spells, the climatic index CDD (Maximum number of consecutive dry days

  19. Disclosing Multiple Magma Degassing Sources Offers Unique Insights of What's Behind the Campi Flegrei Caldera Unrest

    Science.gov (United States)

    Moretti, R.; Civetta, L.; Orsi, G.; Arienzo, I.; D'Antonio, M.; Di Renzo, V.

    2013-12-01

    The definition of the structure and evolution of the magmatic system of Campi Flegrei caldera (CFc), Southern Italy, has been a fundamental tool for the assessment of the short-term volcanic hazard. The ensemble of geophysical and petrologic data show that the CFc magmatic system has been -and still is- characterized by two major reservoirs at different depths. From the deep one (around 8 km), less evolved magmas crystallize and degas, supplying fluids and magmas to the shallow (3-4 km) reservoirs. A thorough reconstruction of processes occurring in magma chamber/s prior and/or during the CFc eruptions has shown that magmas entering shallow reservoirs mixed with resident and crystallized batches. Also the 1982-85 unrest episode has been related to a magma intrusion of 2.1 x 10^7 m^3 at 3-4 km depth, on the basis of geophysical data (ground deformation, gravimetry, seismic imaging) and their interpretation. Thermodynamic evaluation of magma properties, at the time of emplacement, suggests for such an intrusion a bulk density of 2.000 kg/m^3 . Such a value testifies the high amount of exsolved volatiles within the system. The available record of geochemical and isotopic data on surface fumaroles, coupled with melt inclusion data, has already shown that dual (deep and shallow) magma degassing from such two reservoirs, as well as their interaction with the hydrothermal system, allows explaining the relevant fluctuations observed at crater fumaroles after the 1982-85 magma intrusion. An important role was played by the rapid crystallization (around 30 years) of the shallow magma, such that in the recent years gas discharges should be fuelled mostly by the deep magma. Such a process is well recorded in the fumarolic gas composition of the last ~10 years, but has to be reconciled with the unrest dynamics which took place after year 2000, characterized by a slow but continuous ground uplift. All geochemical indicators (major species and noble gases) point to three possible

  20. Thermal evolution of magma reservoirs in the shallow crust and incidence on magma differentiation: the St-Jean-du-Doigt layered intrusion (Brittany, France)

    Science.gov (United States)

    Barboni, M.; Bussy, F.; Ovtcharova, M.; Schoene, B.

    2009-12-01

    Understanding the emplacement and growth of intrusive bodies in terms of mechanism, duration, thermal evolution and rates are fundamental aspects of crustal evolution. Recent studies show that many plutons grow in several Ma by in situ accretion of discrete magma pulses, which constitute small-scale magmatic reservoirs. The residence time of magmas, and hence their capacities to interact and differentiate, are controlled by the local thermal environment. The latter is highly dependant on 1) the emplacement depth, 2) the magmas and country rock composition, 3) the country rock thermal conductivity, 4) the rate of magma injection and 5) the geometry of the intrusion. In shallow level plutons, where magmas solidify quickly, evidence for magma mixing and/or differentiation processes is considered by many authors to be inherited from deeper levels. We show however that in-situ differentiation and magma interactions occurred within basaltic and felsic sills at shallow depth (0.3 GPa) in the St-Jean-du-Doigt bimodal intrusion, France. Field evidence coupled to high precision zircon U-Pb dating document progressive thermal maturation within the incrementally built laccolith. Early m-thick mafic sills are homogeneous and fine-grained with planar contacts with neighbouring felsic sills; within a minimal 0.5 Ma time span, the system gets warmer, adjacent sills interact and mingle, and mafic sills are differentiating in the top 40 cm of the layer. Rheological and thermal modelling show that observed in-situ differentiation-accumulation processes may be achieved in less than 10 years at shallow depth, provided that (1) the differentiating sills are injected beneath consolidated, yet still warm basalt sills, which act as low conductive insulating screens, (2) the early mafic sills accreted under the roof of the laccolith as a 100m thick top layer within 0.5 My, and (3) subsequent and sustained magmatic activity occurred on a short time scale (years) at an injection rate of ca. 0

  1. Effects of Rotation on the Differentiation of a terrestrial Magma Ocean

    Science.gov (United States)

    Maas, C.; Hansen, U.

    2014-12-01

    It is widely accepted that the Earth experienced several large impacts during its early evolution which led to the formation of one or more magma oceans. Differentiation processes in such a magma ocean are of great importance for the initial conditions of mantle convection and for the subsequent mantle structure. Convection in a magma ocean is most likely very vigorous. Further, rotation of the early Earth is supposed to be very fast. Therefore, and due to the small viscosity, it can be assumed that differentiation is strongly affected by rotation.To study the influence of rotation on the crystallization of a magma ocean, we employed a 3D Cartesian numerical model with low Prandtl number and used a discrete element method to describe silicate crystals.Our results show a crucial dependence on crystal density, rotation rate and latitude. Low rotation at the pole leads to a large fraction of suspended particles. With increasing rotation the particles settle at the bottom and form a stable stratified layer. In contrast to that at the equator at low rotation all particles settle at the bottom, at higher rotation they form a layer of significant thickness and at the highest rotation rate the particles accumulate in the middle of the magma ocean. In addition to that, we observe that due to the Coriolis force silicate crystals with different densities separate from each other. While lighter particles are at the bottom, denser particles accumulate at mid-depth at the same rotation rate. This could result in an unstable stratified mantle in the equatorial region after magma ocean solidification.All in all, rotation could lead to an asymmetrical crystallization of the magma ocean, with a contrary layering at the pole and the equator. This affects the composition of the early mantle and could explain the development of a localized magma ocean at the core-mantle boundary and the development of phase transitions observed in seismology, like the mantle transition zone.

  2. Melt zones beneath five volcanic complexes in California: an assessment of shallow magma occurrences

    Energy Technology Data Exchange (ETDEWEB)

    Goldstein, N.E.; Flexser, S.

    1984-12-01

    Recent geological and geophysical data for five magma-hydrothermal systems were studied for the purpose of developing estimates for the depth, volume and location of magma beneath each area. The areas studied were: (1) Salton Trough, (2) The Geysers-Clear Lake, (3) Long Valley caldera, (4) Coso volcanic field, and (5) Medicine Lake volcano, all located in California and all selected on the basis of recent volcanic activity and published indications of crustal melt zones. 23 figs.

  3. Bubble accumulation and its role in the evolution of magma reservoirs in the upper crust.

    Science.gov (United States)

    Parmigiani, A; Faroughi, S; Huber, C; Bachmann, O; Su, Y

    2016-04-28

    Volcanic eruptions transfer huge amounts of gas to the atmosphere. In particular, the sulfur released during large silicic explosive eruptions can induce global cooling. A fundamental goal in volcanology, therefore, is to assess the potential for eruption of the large volumes of crystal-poor, silicic magma that are stored at shallow depths in the crust, and to obtain theoretical bounds for the amount of volatiles that can be released during these eruptions. It is puzzling that highly evolved, crystal-poor silicic magmas are more likely to generate volcanic rocks than plutonic rocks. This observation suggests that such magmas are more prone to erupting than are their crystal-rich counterparts. Moreover, well studied examples of largely crystal-poor eruptions (for example, Katmai, Taupo and Minoan) often exhibit a release of sulfur that is 10 to 20 times higher than the amount of sulfur estimated to be stored in the melt. Here we argue that these two observations rest on how the magmatic volatile phase (MVP) behaves as it rises buoyantly in zoned magma reservoirs. By investigating the fluid dynamics that controls the transport of the MVP in crystal-rich and crystal-poor magmas, we show how the interplay between capillary stresses and the viscosity contrast between the MVP and the host melt results in a counterintuitive dynamics, whereby the MVP tends to migrate efficiently in crystal-rich parts of a magma reservoir and accumulate in crystal-poor regions. The accumulation of low-density bubbles of MVP in crystal-poor magmas has implications for the eruptive potential of such magmas, and is the likely source of the excess sulfur released during explosive eruptions.

  4. Aleutian tholeiitic and calc-alkaline magma series I: The mafic phenocrysts

    Science.gov (United States)

    Kay, S. Mahlburg; Kay, Robert W.

    1985-07-01

    Diagnostic mafic silicate assemblages in a continuous spectrum of Aleutian volcanic rocks provide evidence for contrasts in magmatic processes in the Aleutian arc crust. Tectonic segmentation of the arc exerts a primary control on the variable mixing, fractional crystallization and possible assimilation undergone by the magmas. End members of the continuum are termed calc-alkaline (CA) and tholeiitic (TH). CA volcanic rocks (e.g., Buldir and Moffett volcanoes) have low FeO/MgO ratios and contain compositionally diverse phenocryst populations, indicating magma mixing. Their Ni and Cr-rich magnesian olivine and clinopyroxene come from mantle-derived mafic olivine basalts that have mixed with more fractionated magmas at mid-to lower-crustal levels immediately preceding eruption. High-Al amphibole is associated with the mafic end member. In contrast, TH lavas (e.g., Okmok and Westdahl volcanoes) have high FeO/MgO ratios and contain little evidence for mixing. Evolved lavas represent advanced stages of low pressure crystallization from a basaltic magma. These lavas contain groundmass olivine (FO 40 50) and lack Ca-poor pyroxene. Aleutian volcanic rocks with intermediate FeO/MgO ratios are termed transitional tholeiitic (TTH) and calc-alkaline (TCA). TCA magmas are common (e.g., Moffett, Adagdak, Great Sitkin, and Kasatochi volcanoes) and have resulted from mixing of high-Al basalt with more evolved magmas. They contain amphibole (high and low-Al) or orthopyroxene or both and are similar to the Japanese hypersthene-series. TTH magmas (e.g., Okmok and Westdahl) contain orthopyroxene or pigeonite or both, and show some indication of upper crustal mixing. They are mineralogically similar to the Japanese pigeonite-series. High-Al basalt lacks Mg-rich mafic phases and is a derivative magma produced by high pressure fractionation of an olivine tholeiite. The low pressure mineral assemblage of high-Al basalt results from crystallization at higher crustal levels.

  5. Crystallization of a compositionally stratified basal magma ocean

    Science.gov (United States)

    Laneuville, Matthieu; Hernlund, John; Labrosse, Stéphane; Guttenberg, Nicholas

    2018-03-01

    Earth's ∼3.45 billion year old magnetic field is regenerated by dynamo action in its convecting liquid metal outer core. However, convection induces an isentropic thermal gradient which, coupled with a high core thermal conductivity, results in rapid conducted heat loss. In the absence of implausibly high radioactivity or alternate sources of motion to drive the geodynamo, the Earth's early core had to be significantly hotter than the melting point of the lower mantle. While the existence of a dense convecting basal magma ocean (BMO) has been proposed to account for high early core temperatures, the requisite physical and chemical properties for a BMO remain controversial. Here we relax the assumption of a well-mixed convecting BMO and instead consider a BMO that is initially gravitationally stratified owing to processes such as mixing between metals and silicates at high temperatures in the core-mantle boundary region during Earth's accretion. Using coupled models of crystallization and heat transfer through a stratified BMO, we show that very high temperatures could have been trapped inside the early core, sequestering enough heat energy to run an ancient geodynamo on cooling power alone.

  6. Magma reservoir at Mt. Vesuvius: Deeper than 10 km

    International Nuclear Information System (INIS)

    Natale, M.; Luongo, G.; Nunziata, C.; Panza, G.F.

    2005-07-01

    One- and two-dimensional Vp models were obtained by TomoVes experiment, all characterized by low Vp in the uppermost 500 m and a sharp discontinuity at about 2-3 km beneath the volcano. Large amplitude late arrivals were identified as P- to S-phases converted at the top, between 8 and 10 km deep, of a low velocity layer with a dramatic drop of Vs, from approximately 3.6 km/s to less than 1.0 km/s. Here we synthesize the interpretation of Rayleigh wave dispersion measurements, made by several authors, to delineate the extent of such anomalous layer of hot, partially molten, crust material. Our non-linear inversion of broad-band dispersion measurements, gives a thickness not greater than 0.35 km, if we assume Vs equal to 1.0 km/s. The volume occupied by this very low velocity layer, sill shaped, is compatible with the size of Mt. Vesuvius cone, but it develops above a much larger hot mass which could be the parental source as the erupted products are only few percent of magma chamber. (author)

  7. Advancement of magma fragmentation by inhomogeneous bubble distribution.

    Science.gov (United States)

    Kameda, M; Ichihara, M; Maruyama, S; Kurokawa, N; Aoki, Y; Okumura, S; Uesugi, K

    2017-12-01

    Decompression times reported in previous studies suggest that thoroughly brittle fragmentation is unlikely in actual explosive volcanic eruptions. What occurs in practice is brittle-like fragmentation, which is defined as the solid-like fracture of a material whose bulk rheological properties are close to those of a fluid. Through laboratory experiments and numerical simulation, the link between the inhomogeneous structure of bubbles and the development of cracks that may lead to brittle-like fragmentation was clearly demonstrated here. A rapid decompression test was conducted to simulate the fragmentation of a specimen whose pore morphology was revealed by X-ray microtomography. The dynamic response during decompression was observed by high-speed photography. Large variation was observed in the responses of the specimens even among specimens with equal bulk rheological properties. The stress fields of the specimens under decompression computed by finite element analysis shows that the presence of satellite bubbles beneath a large bubble induced the stress concentration. On the basis of the obtained results, a new mechanism for brittle-like fragmentation is proposed. In the proposed scenario, the second nucleation of bubbles near the fragmentation surface is an essential process for the advancement of fragmentation in an upward magma flow in a volcanic conduit.

  8. Are Ferroan Anorthosites Direct Products of the Lunar Magma Ocean?

    Science.gov (United States)

    Neal, C. R.; Draper, D. S.

    2016-01-01

    According to Lunar Magma Ocean (LMO) theory, lunar samples that fall into the ferroan anorthosite (FAN) category represent the only samples we have of of the primordial crust of the Moon. Modeling indicates that plagioclase crystallizes after >70% LMO crystallization and formed a flotation crust, depending upon starting composition. The FAN group of highlands materials has been subdivided into mafic-magnesian, mafic-ferroan, anorthositic- sodic, and anorthositic-ferroan, although it is not clear how these subgroups are related. Recent radiogenic isotope work has suggested the range in FAN ages and isotopic systematics are inconsistent with formation of all FANs from the LMO. While an insulating lid could have theoretically extend the life of the LMO to explain the range of the published ages, are the FAN compositions consistent with crystallization from the LMO? As part of a funded Emerging Worlds proposal (NNX15AH76G), we examine this question through analysis of FAN samples. We compare the results with various LMO crystallization models, including those that incorporate the influence of garnet.

  9. Thermomechanical controls on magma supply and volcanic deformation: application to Aira caldera, Japan

    Science.gov (United States)

    Hickey, James; Gottsmann, Joachim; Nakamichi, Haruhisa; Iguchi, Masato

    2016-01-01

    Ground deformation often precedes volcanic eruptions, and results from complex interactions between source processes and the thermomechanical behaviour of surrounding rocks. Previous models aiming to constrain source processes were unable to include realistic mechanical and thermal rock properties, and the role of thermomechanical heterogeneity in magma accumulation was unclear. Here we show how spatio-temporal deformation and magma reservoir evolution are fundamentally controlled by three-dimensional thermomechanical heterogeneity. Using the example of continued inflation at Aira caldera, Japan, we demonstrate that magma is accumulating faster than it can be erupted, and the current uplift is approaching the level inferred prior to the violent 1914 Plinian eruption. Magma storage conditions coincide with estimates for the caldera-forming reservoir ~29,000 years ago, and the inferred magma supply rate indicates a ~130-year timeframe to amass enough magma to feed a future 1914-sized eruption. These new inferences are important for eruption forecasting and risk mitigation, and have significant implications for the interpretations of volcanic deformation worldwide. PMID:27619897

  10. Magma mixing in granitic rocks of the central Sierra Nevada, California

    Science.gov (United States)

    Reid, John B.; Evans, Owen C.; Fates, Dailey G.

    1983-12-01

    The El Capitan alaskite exposed in the North American Wall, Yosemite National Park, was intruded by two sets of mafic dikes that interacted thermally and chemically with the host alaskite. Comparisons of petrographic and compositional data for these dikes and alaskite with published data for Sierra Nevada plutons lead us to suggest that mafic magmas were important in the generation of the Sierra Nevada batholith. Specifically, we conclude that: (1) intrusion of mafic magmas in the lower crust caused partial melting and generation of alaskite (rhyolitic) magmas; (2) interaction between the mafic and felsic magmas lead to the observed linear variation diagrams for major elements; (3) most mafic inclusions in Sierra Nevada plutons represent chilled pillows of mafic magmas, related by fractional crystallization and granitoid assimilation, that dissolve into their felsic host and contaminate it to intermediate (granodioritic) compositions; (4) vesiculation of hydrous mafic magma upon chilling may allow buoyant mafic inclusions and their disaggregation products to collect beneath a pluton's domed ceiling causing the zoning (mafic margins-to-felsic core) that these plutons exhibit.

  11. Rapid ascent of rhyolitic magma at Chaitén volcano, Chile.

    Science.gov (United States)

    Castro, Jonathan M; Dingwell, Donald B

    2009-10-08

    Rhyolite magma has fuelled some of the Earth's largest explosive volcanic eruptions. Our understanding of these events is incomplete, however, owing to the previous lack of directly observed eruptions. Chaitén volcano, in Chile's northern Patagonia, erupted rhyolite magma unexpectedly and explosively on 1 May 2008 (ref. 2). Chaitén residents felt earthquakes about 24 hours before ash fell in their town and the eruption escalated into a Plinian column. Although such brief seismic forewarning of a major explosive basaltic eruption has been documented, it is unprecedented for silicic magmas. As precursory volcanic unrest relates to magma migration from the storage region to the surface, the very short pre-eruptive warning at Chaitén probably reflects very rapid magma ascent through the sub-volcanic system. Here we present petrological and experimental data that indicate that the hydrous rhyolite magma at Chaitén ascended very rapidly, with velocities of the order of one metre per second. Such rapid ascent implies a transit time from storage depths greater than five kilometres to the near surface in about four hours. This result has implications for hazard mitigation because the rapidity of ascending rhyolite means that future eruptions may provide little warning.

  12. Temperatures and isotopic evolution of silicic magmas, Taupo Volcanic Zone and Coromandel, New Zealand

    International Nuclear Information System (INIS)

    Blattner, P.; Rui-Zhong H.; Graham, I.J.; Houston-Eleftheriadis, C.

    1996-01-01

    A new set of oxygen and strontium isotope data on rhyolitic lavas and ignimbrites of the Taupo Volcanic Zone (TVZ) and the Coromandel Peninsula provides new limits for petrogenic models. For oxygen isotopes, the rock matrix is frequently altered, so that values for magma need to be phenocryst based. Within TVZ a trend towards more negative δ 1 8O values for more recent magmas appears likely (average before about 1 Ma and for Coromandel near 8.0 per mille; after 1 Ma near 7.5 per mille). This could indicate the gradual removal of supracrustal contaminants from the zones of magma accumulation and extrusion. Similar trends within Coromandel cannot yet be resolved. A generally positive correlation is found for oxygen and strontium isotopes of magmas. Most magmas have a limited range of isotopic values, which then becomes a fingerprint (e.g., the Mamaku, Matahina, and Waiotapu Ignimbrites). A narrow range of eruption temperatures of 880 ± 60 o C is derived from quartz-plagioclase fractionations of 0.98 ± 0.25 per mille δ 1 8O values of quartz and feldspar phenocrysts are sufficiently low to suggest interaction between surface water and magma. However, large negative oxygen isotope anomalies (such as known from Yellowstone), could be no more than partially concealed by the isotopically less depleted meteoric water of New Zealand, and have not yet been found in New Zealand. (authors). 45 refs., 6 figs., 3 tabs

  13. Trace element and isotopic effects arising from magma migration beneath mid-ocean ridges

    International Nuclear Information System (INIS)

    Kenyon, P.M.

    1990-01-01

    The trace element concentrations and isotopic ratios in the magma erupted on mid-ocean ridges may differ from those in the source material due to physical effects such as porous flow dispersion, exchange of trace elements between the fluid and solid phases during magma migration, and convective mixing in magma chambers. These differences are in addition to those produced by better known processes such as fractional crystallization and partial melting. The effects of the three former processes are described. It is predicted that magma typically reaches the sub-ridge magma chambers with a spatial heterogeneity only slightly reduced from that of the source material, but with a subdued variation in time. Convective mixing then further reduces the spatial heterogeneity. Application of the results for convective mixing to a recent Fourier analysis of 87 Sr/ 86 Sr variations along the Mid-Atlantic Ridge suggests that the falloff in amplitude of variation observed with decreasing wavelength in the Mid-Atlantic Ridge data cannot be explained by convective mixing in magma chambers. Instead, it is postulated that this falloff is due to the mechanics of the production and/or the solid-state convective mixing of chemical and isotopic heterogeneities in the solid mantle. (orig.)

  14. Thermomechanical controls on magma supply and volcanic deformation: application to Aira caldera, Japan.

    Science.gov (United States)

    Hickey, James; Gottsmann, Joachim; Nakamichi, Haruhisa; Iguchi, Masato

    2016-09-13

    Ground deformation often precedes volcanic eruptions, and results from complex interactions between source processes and the thermomechanical behaviour of surrounding rocks. Previous models aiming to constrain source processes were unable to include realistic mechanical and thermal rock properties, and the role of thermomechanical heterogeneity in magma accumulation was unclear. Here we show how spatio-temporal deformation and magma reservoir evolution are fundamentally controlled by three-dimensional thermomechanical heterogeneity. Using the example of continued inflation at Aira caldera, Japan, we demonstrate that magma is accumulating faster than it can be erupted, and the current uplift is approaching the level inferred prior to the violent 1914 Plinian eruption. Magma storage conditions coincide with estimates for the caldera-forming reservoir ~29,000 years ago, and the inferred magma supply rate indicates a ~130-year timeframe to amass enough magma to feed a future 1914-sized eruption. These new inferences are important for eruption forecasting and risk mitigation, and have significant implications for the interpretations of volcanic deformation worldwide.

  15. The Krafla International Testbed (KMT): Ground Truth for the New Magma Geophysics

    Science.gov (United States)

    Brown, L. D.; Kim, D.; Malin, P. E.; Eichelberger, J. C.

    2017-12-01

    Recent developments in geophysics such as large N seismic arrays , 4D (time lapse) subsurface imaging and joint inversion algorithms represent fresh approaches to delineating and monitoring magma in the subsurface. Drilling at Krafla, both past and proposed, are unique opportunities to quantitatively corroborate and calibrate these new technologies. For example, dense seismic arrays are capable of passive imaging of magma systems with resolutions comparable to that achieved by more expensive (and often logistically impractical) controlled source surveys such as those used in oil exploration. Fine details of the geometry of magma lenses, feeders and associated fluid bearing fracture systems on the scale of meters to tens of meters are now realistic targets for surface seismic surveys using ambient energy sources, as are detection of their temporal variations. Joint inversions, for example of seismic and MT measurements, offer the promise of tighter quantitative constraints on the physical properties of the various components of magma and related geothermal systems imaged by geophysics. However, the accuracy of such techniques will remain captive to academic debate without testing against real world targets that have been directly sampled. Thus application of these new techniques to both guide future drilling at Krafla and to be calibrated against the resulting borehole observations of magma are an important step forward in validating geophysics for magma studies in general.

  16. The Effect of Education on Economic Growth in Greece over the 1960-2000 Period

    Science.gov (United States)

    Tsamadias, Constantinos; Prontzas, Panagiotis

    2012-01-01

    This paper examines the impact of education on economic growth in Greece over the period 1960-2000 by applying the model introduced by Mankiw, Romer, and Weil. The findings of the empirical analysis reveal that education had a positive and statistically significant effect on economic growth in Greece over the period 1960-2000. The econometric…

  17. A Review of the Library and Information Services In Greece: Current Developments that Shape LIS Education

    Science.gov (United States)

    Garoufallou, Emmanouel; Siatri, Rania; Hartley, R. J.

    2008-01-01

    This paper sets the context for this special issue on LIS education in Greece by explaining the Greek higher education system both in organisational terms and in the approaches to teaching and learning. In addition it briefly outlines the current state of development in libraries in Greece. Taken together they provide the background to the…

  18. Tracking the vector of Onchocerca lupi in a rural area of Greece.

    Science.gov (United States)

    Otranto, Domenico; Dantas-Torres, Filipe; Papadopoulos, Elias; Petrić, Dušan; Ćupina, Aleksandra Ignjatović; Bain, Odile

    2012-07-01

    During a hot Mediterranean summer, an expedition brought parasitologists from Brazil, France, Greece, Italy, and Serbia to a wooded area near Xanthi, Thrace, northeastern Greece, near the Turkish border, on the track of the vector of the little-known nematode Onchocerca lupi. The scientific purposes of the expedition blended then with stories of humans, animals, and parasites in this rural area.

  19. The urban roots of anti-neoliberal social movements: the case of Athens, Greece

    NARCIS (Netherlands)

    Arampatzi, A.; Nicholls, W.J.

    2012-01-01

    The recent rounds of anti-neoliberal mobilizations in Europe have shown to be rooted in cities. Whereas Madrid has become a central hub in Spain’s social movement, Athens has assumed a central and centralizing role in Greece. Through a case study on Athens, Greece, this paper aims to show how cities

  20. Historical and Contemporary Aspects of the Relationship between the State and Adult Education in Greece.

    Science.gov (United States)

    Boucouvalas, Marcie

    An outgrowth of earlier research on historical and contemporary adult education in Greece, this paper provides highlights of the relationship between the state and adult education in that country. The highlights are organized by the following historical periods: prehistory (c. 3000-1100 B.C.); early and archaic Greece (c. 1100-700 B.C.);…

  1. The outstanding synergy between drought, heatwaves and fuel on the 2007 Southern Greece exceptional fire season

    NARCIS (Netherlands)

    Gouveia, Célia M.; Bistinas, Ioannis; Liberato, Margarida L.R.; Bastos, Ana; Koutsias, Nikos; Trigo, Ricardo

    2016-01-01

    The fire season of 2007 was particularly devastating for Greece, achieving the new all-time record of estimated burnt area (225,734. ha) since 1980. The season was remarkably severe in Peloponnese Peninsula, in southern continental Greece, being considered the most extreme natural disaster in the

  2. Interactions between wall rocks around magma and hot water. Magma shuhen no hekigan/nessui sogo sayo

    Energy Technology Data Exchange (ETDEWEB)

    Fujimoto, K.

    1992-12-01

    This paper describes interactions between wall rocks around magma and hot water. The paper discusses effects of hydrothermal environments on dynamic properties of rock minerals with respect to hydrolytic weakening (decrease in dynamic strength of a mineral under presence of water) and reaction enhanced deformation (deformation accelerated by chemical change occurring in a mineral itself). It also explains chemical reactivity of minerals under hydrothermal enviroments with respect to four types of chemical changes in minerals, factors governing mineral dissolution rates, and importance of equilibrium and non-equilibrium in main components in reactions between minerals and waters. These statements quote mainly results of indoor experiments. The paper indicates the following matters as problems to be discussed on interactions between wall rocks around intrusive rocks and hot waters: Deviation from chemical equilibrium in reactions between rocks and waters; change in permeability as a result of reactions between rocks and waters; and possibilities of hydrolytic weakening in rocks around intrusive rock bodies. 52 refs., 6 figs.

  3. The change of magma chamber depth in and around the Baekdu Volcanic area from late Cenozoic

    Science.gov (United States)

    Lee, S. H.; Oh, C. W.; Lee, Y. S.; Lee, S. G.; Liu, J.

    2016-12-01

    The Baekdu Volcano is a 2750m high stratovolcanic cone resting on a basaltic shield and plateau and locates on the North Korea-China border. Its volcanic history can be divided into four stages (from the oldest to the youngest): (i) preshield plateau-forming eruptions, (ii) basalt shield formation, (iii) construction of a trachytic composite cone, and (iv) explosive ignimbrite forming eruptions. In the First stage, a fissure eruption produced basalts from the Oligocene to the Miocene (28-13 Ma) forming preshield plateau. Fissure and central eruptions occurred together during the shield-forming eruptions (4.21-1.70 Ma). In the third stage, the trachytic composite volcano formed during the Pleistocene (0.61-0.09 Ma). In this stage, magma changed to an acidic melt. The latest stage has been characterized by explosive ignimbrite-forming eruptions during the Holocene. The composite volcanic part consists of the Xiaobaishan, Lower, Middle and Upper Trachytes with rhyolites. The whole rock and clinopyroxene in basalts, trachytic and rhyolite, are analyzed to study the depth of magma chambers under the Baekdu Volcano. From the rhyolite, 9.8-12.7kbar is obtained for the depth of magma chamber. 3.7-4.1, 8.9-10.5 and 8.7 kbar are obtained from the middle, lower and Xiaobaishan trachytes. From the first and second stage basalts, 16.9-17.0 kbar and 14-14.4kbar are obtained respectively. The first stage basalt give extrusive age of 11.98 Ma whereas 1.12 and 1.09 Ma are obtained from the feldspar and groundmass in the second stage basalt. The Xiaobaishan trachyte and rhyolite give 0.25 and 0.21 Ma whereas the Middle trachyte gives 0.07-0.06 Ma. These data indicate that the magma chambers of the first and second stage basalts were located in the mantle and the magma chamber for the second stage basalt may have been underplated below continental crust. The Xiaobisan trachyte and rhyolite originated from the magma chamber in the depth of ca. 30-40 km and the Middle trachyte

  4. Reconciling Gases With Glasses: Magma Degassing, Overturn and Mixing at Kilauea Volcano, Hawai`i

    Science.gov (United States)

    Edmonds, M.; Gerlach, T. M.

    2006-12-01

    Our understanding of the volatile budget at Kilauea Volcano is based on measurements of the abundance of volatile elements in volcanic glasses and gases. Observations of volcanic gases gave rise to a fundamental model describing volatile fractionation between the summit and rift zone during the current eruption [Gerlach and Graeber, 1985]. Other workers' analysis of glasses from the Puna Ridge, Kilauea Iki and Pu`u `O`o indicate that magma degassing, drain-back, mixing and assimilation are important processes at Kilauea Volcano. Volcanic gases have not illustrated these kinds of processes clearly in the past, owing to infrequent and poorly resolved data. New, detailed studies of volcanic gas emissions have refined our understanding of volatile degassing and magma budgets at Kilauea Volcano. Open Path Fourier Transform Infra-Red spectroscopy measurements carried out during 2004-2005 allow retrieval of the relative abundances of the major volatile species H2O, CO2 and SO2, which together make up >99 vol% of the magmatic vapor phase. The proportions of these gases vary over time and space and can be used to infer magma transport, ascent, degassing, overturn and mixing and gas segregation processes within the plumbing system of Kilauea Volcano. Gases from Pu`u `O`o in 2004-2005 display a range in composition. A trend relates molar C/S to the total H2O content of the gases over time and space; total H2O ranges from 60-98 mol %, while molar C/S ranges from 50. The range in volcanic gas composition over time and space is caused by magma degassing, overturn and mixing of partially degassed magma with fresh primary magma beneath Pu`u `O`o. Measurements of the mean rate of magma degassing (from SO2 emissions) and mean lava effusion rate (from geophysical measurements of lava tube flux) suggest that a larger volume (DRE) of magma is degassing than is being erupted, on average. This analysis suggests that magma storage in the Rift Zone might be important during eruptions as

  5. Gender and migration in Greece: the position and status of Albanian women in Patras

    Directory of Open Access Journals (Sweden)

    Dimitra Charalampopoulu

    2004-06-01

    Full Text Available Greece has experienced major changes in its migration patterns.After a century or so of emigration, it has now become a country of immigration. Much academic research has concentrated on the impact this change has on Greek society. However, there is a tendency to ignore the role that gender plays in the migration process. This article addresses the issue of Albanian immigration to Greece, focusing on the aspect of gender. It presents the living and working conditions of Albanian women who migrate to Greece, especially to one of its cities, Patras. It examines the new migration process through the eyes of women migrants. It is centred on their narration about their journey to Greece, their decision to migrate, the problems that they face, their experiences and plans for the future: in short, their life stories. Finally, the article draws attention to the need for further research on issues concerning migrant women in Greece.

  6. Augustan Greece in Strabo’s Geography: A Short Survey

    Directory of Open Access Journals (Sweden)

    Marjeta Šašel Kos

    2010-07-01

    Full Text Available Strabo dedicated books 8 and 9 of his Geography to Greece, which he describes in great detail. While the greater part of his narrative reads like the description of an earlier Greece, he does include some interesting notes on his own period. His descriptions largely refer to passages in Homer, whom he considers the ultimate authority, since the Iliad and Odyssey formed an important part of the then school curriculum. A recurring observation is that a number of Greek settlements, once densely populated, were in his day deserted. There is no doubt that much of Greece was left waste in the Hellenistic period, especially in the period from Polybius (2nd century B.C. to Strabo (the beginning of the Christian era. While the information from Strabo’s own time represents a very small portion of the two books, it is often of great historical interest. He mentions, for example, the rule of Gaius Iulius Eurycles in Sparta; Eurycles came into conflict with Rome because he allegedly abused his friendship with Augustus, appropriating the island of Cythera and tyrannically extending his power through Laconia. Certainly one of the most influential personages in the Greece of his day, he had inscriptions set up in his honour throughout Laconia and elsewhere in the Peloponnese.  Somewhat more attention is devoted by Strabo to Corinth, which he visited personally. According to him, the city’s affluence was due to trade: lying on the Isthmus, it controlled two ports, Cenchreae, from which ships sailed for Asia, and Lechaeum, which was its link to Greece. Strabo describes the dramatic fall of Corinth: in 146 B.C. it was burnt down by the Roman consul, Lucius Mummius, and robbed of practically all its art works, which were then used to adorn the temples in Rome, in other Italian towns and elsewhere in the Mediterranean, since many were sold as war booty. Strabo mentions that Polybius, who was in Corinth at the time, was particularly saddened by the Roman

  7. Bonding of xenon to oxygen in magmas at depth

    Science.gov (United States)

    Leroy, Clémence; Sanloup, Chrystèle; Bureau, Hélène; Schmidt, Burkhard C.; Konôpková, Zuzana; Raepsaet, Caroline

    2018-02-01

    The field of noble gases chemistry has witnessed amazing advances in the last decade with over 100 compounds reported including Xe oxides and Xe-Fe alloys stable at the pressure-temperature conditions of planetary interiors. The chemistry of Xe with planetary materials is nonetheless still mostly ignored, while Xe isotopes are used to trace a variety of key planetary processes from atmosphere formation to underground nuclear tests. It is indeed difficult to incorporate the possibility of Xe reactivity at depth in isotopic geochemical models without a precise knowledge of its chemical environment. The structure of Xe doped hydrous silica-rich melts is investigated by in situ high energy synchrotron X-ray diffraction using resistive heating diamond anvil cells. Obtained pair distribution functions reveal the oxidation of Xe between 0.2 GPa and 4 GPa at high T up to 1000 K. In addition to the usual interatomic distances, a contribution at 2.05 ± 0.05 Å is observed. This contribution is not observed in the undoped melt, and is interpreted as the Xe-O bond, with a coordination number of about 12 consistent with Xe insertion in rings of the melt structure. Xe solubility measurements by electron microprobe and particle induced X-rays emission analysis confirm that Xe and Ar have similar solubility values in wt% in silicate melts. These values are nonetheless an order of magnitude higher than those theoretically calculated for Xe. The formation of Xe-O bonds explains the enhanced solubility of Xe in deep continental crust magmas, revealing a mechanism that could store Xe and fractionate its isotopes. Xenon is indeed atypical among noble gases, the atmosphere being notably depleted in elemental Xe, and very strongly depleted in Xe light isotopes. These observations are known as the 'missing' Xe paradox, and could be solved by the present findings.

  8. On the Role of Mantle Overturn during Magma Ocean Solidification

    Science.gov (United States)

    Boukaré, C. E.; Parmentier, E.; Parman, S. W.

    2017-12-01

    Solidification of potential global magma ocean(s) (MO) early in the history of terrestrial planets may play a key role in the evolution of planetary interiors by setting initial conditions for their long-term evolution. Constraining this initial structure of solid mantles is thus crucial but remains poorly understood. MO fractional crystallization has been proposed to generate gravitationally unstable Fe-Mg chemical stratification capable of driving solid-state mantle overturn. Fractional solidification and overturn hypothesis, while only an ideal limiting case, can explain important geochemical features of both the Moon and Mars. Current overturn models consider generally post-MO overturn where the cumulate pile remains immobile until the end of MO solidification. However, if the cumulate pile overturns during MO solidification, the general picture of early planet evolution might differ significantly from the static crystallization models. We show that the timing of mantle overturn can be characterized with a dimensionless number measuring the ratio of the MO solidification time and the purely compositional overturn timescale. Syn-solidification overturn occurs if this dimensionless parameter, Rc, exceeds a critical value. Rc is mostly affected by the competition between the MO solidification time and mantle viscosity. Overturn that occurs during solidification can result in smaller scales of mantle chemical heterogeneity that could persist for long times thus influencing the whole evolution of a planetary body. We will discuss the effects of compaction/percolation on mantle viscosity. If partially molten cumulate do not have time to compact during MO solidification, viscosity of cumulates would be significantly lower as the interstitcial melt fraction would be large. Both solid mantle remelting during syn-solidification overturn and porous convection of melt retained with the cumulates are expected to reduce the degree of fractional crystallization. Syn

  9. Primary and secondary fragmentation of crystal-bearing intermediate magma

    Science.gov (United States)

    Jones, Thomas J.; McNamara, Keri; Eychenne, Julia; Rust, Alison C.; Cashman, Katharine V.; Scheu, Bettina; Edwards, Robyn

    2016-11-01

    Crystal-rich intermediate magmas are subjected to both primary and secondary fragmentation processes, each of which may produce texturally distinct tephra. Of particular interest for volcanic hazards is the extent to which each process contributes ash to volcanic plumes. One way to address this question is by fragmenting pyroclasts under controlled conditions. We fragmented pumice samples from Soufriere Hills Volcano (SHV), Montserrat, by three methods: rapid decompression in a shock tube-like apparatus, impact by a falling piston, and milling in a ball mill. Grain size distributions of the products reveal that all three mechanisms produce fractal breakage patterns, and that the fractal dimension increases from a minimum of 2.1 for decompression fragmentation (primary fragmentation) to a maximum of 2.7 by repeated impact (secondary fragmentation). To assess the details of the fragmentation process, we quantified the shape, texture and components of constituent ash particles. Ash shape analysis shows that the axial ratio increases during milling and that particle convexity increases with repeated impacts. We also quantify the extent to which the matrix is separated from the crystals, which shows that secondary processes efficiently remove adhering matrix from crystals, particularly during milling (abrasion). Furthermore, measurements of crystal size distributions before (using x-ray computed tomography) and after (by componentry of individual grain size classes) decompression-driven fragmentation show not only that crystals influence particular size fractions across the total grain size distribution, but also that free crystals are smaller in the fragmented material than in the original pumice clast. Taken together, our results confirm previous work showing both the control of initial texture on the primary fragmentation process and the contributions of secondary processes to ash formation. Critically, however, our extension of previous analyses to characterisation

  10. Estimating a corporate governance index for companies in Greece

    Directory of Open Access Journals (Sweden)

    Ramona Iulia Țarțavulea (Dieaconescu

    2015-12-01

    Full Text Available European countries have gone through serious efforts to overcome the financial crisis and special measures had to be taken in order to limit the negative impact on businesses and stabilize a healthy economic environment for the single market. The specific governmental policies aimed to keep under control the effects of the crisis and relaunch the economic growth, but they were unpopular among a part of the European citizens. The economic situation forced most managers of private companies to rethink the business strategy and restructure the activity. Lately, Greece has been going through a difficult period, as the crisis worsened the economic situation of the country. The population did not welcome the drastic economic measures which were proposed by IMF and institutional creditors and this conflict almost lead to national insolvency. The problems of Greece are deeply rooted in the business models and economic philosophy. This paper has the purpose of analyzing the corporate governance regulation and practices in Greece and to determine whether it is possible to enhance business profitability and stability by enforcing a better legal framework in the area of corporate governance. The research focuses on the calculation of a corporate governance index for a selection of Greek companies form different sectors of activity (oil &gas, telecommunications, beverages and the analysis of the results may lead to the identification of weaknesses in this domain. Improvements in the corporate governance practices are considered to lead to enhancing business stability and sustainability. The methodology for calculating the corporate governance index is adapted for Greek companies and is in accordance with the provisions of the Hellenic Corporate Governance Code.

  11. Critical evaluation of the hydropower applications in Greece

    Energy Technology Data Exchange (ETDEWEB)

    Kaldellis, J.K. [Laboratory of Soft Energy Applications and Environmental Protection, TEI Piraeus, P.O. Box 41046, Athens 12201 (Greece)

    2008-01-15

    Hydropower is a proven technology for electricity generation, contributing with almost 20% to the fulfilment of the planet electricity demand. Hydropower is also renewable because it draws its essential energy from the sun and particularly from the hydrological cycle. Greece and more precisely the west and north part of the mainland possesses significant hydropower potential that is up to now partially exploited. In the present survey, one investigates the existing situation concerning the applications of hydropower plants in Greece, while the results obtained are compared with the corresponding international and European situation. Subsequently, emphasis is laid on estimating the electricity-generation utilization degree of the existing large hydropower stations, using 25-year long official data. The results obtained underline the fact that the electricity generation is not a priority for the national water management policy and most Greek hydropower stations are used mainly to meet the corresponding peak load demand. On the other hand, increased interest to create numerous new small hydropower plants throughout Greece has been expressed during the last 5 years. According to the information gathered and analyzed, one may state that the available local hydropower potential is quite promising and can substantially contribute to the accomplishment of the national-EU target to cover the 21% of the corresponding electricity consumption from renewable resources. For this purpose one should first define an approved and rational water resources management plan and secondly support the increased utilization of large and small hydropower plants for electricity generation. In this case, properly designed hydropower plants should lead to considerable profits, contributing also in the country's independency from imported oil and accomplishing the Kyoto protocol obligations. (author)

  12. Gravity and isostatic anomaly maps of Greece produced

    Science.gov (United States)

    Lagios, E.; Chailas, S.; Hipkin, R. G.

    A gravity anomaly map of Greece was first compiled in the early 1970s [Makris and Stavrou, 1984] from all available gravity data collected by different Hellenic institutions. However, to compose this map the data had to be smoothed to the point that many of the smaller-wavelength gravity anomalies were lost. New work begun in 1987 has resulted in the publication of an updated map [Lagios et al., 1994] and an isostatic anomaly map derived from it.The gravity data cover the area between east longitudes 19° and 27° and north latitudes 32° and 42°, organized in files of 100-km squares and grouped in 10-km squares using UTM zone 34 coordinates. Most of the data on land come from the gravity observations of Makris and Stavrou [1984] with additional data from the Institute of Geology and Mining Exploration, the Public Oil Corporation of Greece, and Athens University. These data were checked using techniques similar to those used in compiling the gravity anomaly map of the United States, but the horizontal gradient was used as a check rather than the gravity difference. Marine data were digitized from the maps of Morelli et al. [1975a, 1975b]. All gravity anomaly values are referred to the IGSN-71 system, reduced with the standard Bouger density of 2.67 Mg/m3. We estimate the errors of the anomalies in the continental part of Greece to be ±0.9 mGal; this is expected to be smaller over fairly flat regions. For stations whose height has been determined by leveling, the error is only ±0.3 mGal. For the marine areas, the errors are about ±5 mGal [Morelli, 1990].

  13. Results of a QC program on dental radiography in Greece

    Energy Technology Data Exchange (ETDEWEB)

    Pappous, George; Kolitsi, Zoi; Pallikarakis, Nikolas [Medical Physics Department, Patras University, 26 500 Patras (Greece); Arvanitakis, Gerasimos [Achaia branch of Hellenic Dental Association, Pantanasis 70-72, 262 21 (Greece)

    1999-12-31

    Quality Control (QC) performed on 99 intraoral dental X-Ray units, installed in equal in number dental offices, at the Achaia prefecture, a region of south west Greece. The QC procedure includes collection of general information, radiation safety checks, beam qualitative and quantitative characteristic checks, and film processing checks, according to international established protocols. The collected data are characterised by a non-uniformity and in some cases indicate a poor performance level. The results of the study on a representative sample of dental X-Ray units helps to map the existing situation and may be useful in the reviewing and optimisation of the applied process. (authors) 10 refs., 11 figs.

  14. Style and ideology: The cold war 'blend' in Greece

    Directory of Open Access Journals (Sweden)

    Romanu Keti

    2008-01-01

    Full Text Available This paper describes cultural policy in Greece from the end of World War II up to the fall of the junta of colonels in 1974. The writer's object is to show how the Cold War favoured defeated Western countries, which participated effectively in the globalisation of American culture, as in the Western world de-nazification was transformed into a purge of communism. Using the careers of three composers active in communist resistance organizations as examples (Iannis Xenakis, Mikis Theodorakis and Alecos Xenos, the writer describes the repercussions of this phenomenon in Greek musical life and creativity.

  15. Landscape and Early Farming Settlement Dynamics in Central Greece

    DEFF Research Database (Denmark)

    Sarri, Kalliopi; Bintliff, John; Farinetti, Emeri

    2006-01-01

    also small, short-lived farms; both were associated withwetland hand cultivation. In later Neolithic and Early Bronze Age times, these locationsremained, but vestigial traces discovered by hyperintensive survey methods have identified anexplosion of small, short-lived, and horizontally migrating farms......Current hyperintensive surface survey in the Tanagra district of Boeotia, central Greece (J. L.Bintliff et al., 2002), together with a recent reanalysis of survey results from the Thespiae dis-trict (J. L. Bintliff et al., 1999), have led to a radical rethinking of how and where early farm...

  16. Results of a QC program on dental radiography in Greece

    International Nuclear Information System (INIS)

    Pappous, George; Kolitsi, Zoi; Pallikarakis, Nikolas; Arvanitakis, Gerasimos

    1998-01-01

    Quality Control (QC) performed on 99 intraoral dental X-Ray units, installed in equal in number dental offices, at the Achaia prefecture, a region of south west Greece. The QC procedure includes collection of general information, radiation safety checks, beam qualitative and quantitative characteristic checks, and film processing checks, according to international established protocols. The collected data are characterised by a non-uniformity and in some cases indicate a poor performance level. The results of the study on a representative sample of dental X-Ray units helps to map the existing situation and may be useful in the reviewing and optimisation of the applied process. (authors)

  17. Energy consumption and economic growth. Assessing the evidence from Greece

    International Nuclear Information System (INIS)

    Hondroyiannis, George; Lolos, Sarantis; Papapetrou, Evangelia

    2002-01-01

    This paper attempts to shed light into the empirical relationship between energy consumption and economic growth, for Greece (1960-1996) employing the vector error-correction model estimation. The vector specification includes energy consumption, real GDP and price developments, the latter taken to represent a measure of economic efficiency. The empirical evidence suggests that there is a long-run relationship between the three variables, supporting the endogeneity of energy consumption and real output. These findings have important policy implications, since the adoption of suitable structural policies aiming at improving economic efficiency can induce energy conservation without impeding economic growth

  18. Spatial and temporal variability of Aridity Index in Greece

    Science.gov (United States)

    Nastos, Panagiotis; Politi, Nadia; Douvis, Kostas

    2010-05-01

    Drought events have deteriorated in most European regions during the last decades in frequency, duration, or intensity. Besides, increased drying associated with higher temperatures and decreased precipitation have contributed to changes in drought. Drought-affected areas are projected to increase in extent, with the potential for adverse impacts on multiple sectors, e.g. agriculture, water supply, energy production and health, according to IPCC. The objective of this study is the spatial and temporal variability of the Aridity Index (AI) per decade, in Greece during the period 1951-2000, as far as the projections of AI for the period 2051-2100, based on simulations of ensemble regional climate models (RCMs), for A1B SRES scenario. The climatic data used for the analysis concern monthly values of precipitation and air temperature from 28 meteorological stations; 22 stations from the National Hellenic Meteorological Service and 6 stations from neighboring countries. According to the United Nations Environment Programme (UNEP), AI is defined as P/PET, where P is the average annual precipitation and PET is the potential evapotranspiration, estimated by the Thornthwaite method; PET and P must be expressed in same units, e.g., in milimetres. All the meteorological data processing was carried out by the application of Geographical Information System (GIS). The results of the analysis showed that within the examined period a clear shift from "humid" class that characterized the greater area of Greece in 1950's to "sub-humid" and "semi-dry" classes appeared in mainly the eastern regions of Greece, such as eastern Crete Island, Cyclades Islands, Evia and Attica in 1990's. The future projections derived by the simulations of ensemble RCMs indicated that drier conditions are very likely to appear in Greece associated with significant socio-economic consequences. The decreasing precipitation along with the high rates of evapotranspiration, because of increase in the air

  19. General siting regulation and population distribution criteria for Greece

    International Nuclear Information System (INIS)

    Kollas, J.; Yadigaroglu, G.

    1983-01-01

    A new national regulation for nuclear power plant siting is described. The main body of the regulation is similar in contents to the IAEA Code of Practice in siting, but exceeds its scope in certain areas and covers all aspects of the impact of the plant on the population and the environment of the region, including non-radiological effects. The regulation is accompanied by appendices which refer to site suitability criteria with respect to the radiological consequences from the operational states of the plant and with respect to accidents, including core-melt accidents; these reflect the particular geographic and demographic situation of Greece

  20. Tot Graeci Tot Sententiae: Astronomical Perspective Multiplicity in Ancient Greece

    Science.gov (United States)

    Longo, O.

    2011-06-01

    Ancient Greece was made of a multiplicity of thinking heads, in an atmosphere of (relative) freedom of opinions, in every field of knowledge. then we should not wonder if many astronomical and cosmological theories, survived until our 17th century, had already been formulated by different philosophers and in different regions, cities and periods of Greek history. Geocentric and heliocentric theories, as well as an atomistic theory of an infinite universe (with infinite worlds), could survive without crashing with one another. In the same time, religious opinions regarding the planets and Sun as a series of gods were present, however not on a scientific ground.

  1. A Case of Human Infection by Rickettsia slovaca in Greece.

    Science.gov (United States)

    Kostopoulou, Vasiliki; Chochlakis, Dimosthenis; Kanta, Chrysoula; Katsanou, Andromachi; Rossiou, Konstantina; Rammos, Aidonis; Papadopoulos, Spyridon-Filippos; Katsarou, Theodora; Tselentis, Yannis; Psaroulaki, Anna; Boukas, Chrysostomos

    2016-07-22

    Although tick-borne rickettsiosis is endemic in Greece, until recently, human samples arriving at the National Reference Centre under suspicion of rickettsial infection were routinely tested only for Rickettsia typhi and R. conorii. However, identification of additional rickettsia species in ticks prompted revision of the protocol in 2010. Until that year, all human samples received by the laboratory were tested for antibodies against R. conorii and R. typhi only. Now, tests for R. slovaca, R. felis, and R. mongolotimonae are all included in routine analysis. The current description of a human R. slovaca case is possible as a result of these changes in routine testing.

  2. Magnetic Prospecting On Ancient Towns In Turkey and Greece

    Science.gov (United States)

    Smekalova, T.; Smekalov, S.

    Magnetic prospecting on ancient towns in Turkey and Greece. Tatyana Smekalova, Sergey Smekalov. Saint-Petersburg In 2001 archaeophysical group of Saint-Petersburg State University participated in archaeological investigation of ancient town Pisidian Antioch in Turkey (near mod- ern town Yalvach) and ancient town Kalydon in Greece (not far from modern town Mesolongy). Both sites have a big size (more than kilometer in perimeter) and com- plicated hilly relief (especially Kalydon). The mine idea of the magnetic survey on the sites was to try the method of magnetic prospecting in conditions of the sites, to estimate the possibilities and limitations of the method and to reveal ancient structures on several different parts of the site. Magnetic survey on the Pisidian Antioch carried out in four areas of the site showed that much could be recovered by this non-invasive technique. Most significantly, sur- vey of the area previously thought to contain a palestra shows instead the plan of a Christian basilica. Other areas included houses, streets, important elements in the water system and industrial establishments. The work was supported by Columbia University, USA On the Ancient Kalydon, the whole area of the site was investigated by method of Sfree searchT that is walking with magnetometers and measuring without a grid. Five ´ different areas have been chosen for detail investigation with regular grid. The most interesting result is in one of the the areas, where it seems to be an SindustrialT quar- & cedil;ter of the site. There are several workshops, revealed on this place. The work was supported by Ny Carlsberg Glyptotek, Denmark. During the work on both sites we used GPS equipment to put the survey areas on the maps. Simultaneously with magnetic survey archaeological teams made a usual topographical survey of the sites (team of Calgary University in Turkey, Canada and team of Greece topographers, working together with Danish archaeologist in Greece). Thanks to that

  3. Sexualities and public space in Greece:a celluloid quest

    OpenAIRE

    Kallitsis, Phevos

    2014-01-01

    Greece is a country that considers itself to be part of the Western civilization, though still a lot oriental elements exist in its culture and way of thinking. LGBT people are considered to be either invisible or pointed out as metaphorical or literal punch bag. So it was a surprise that a year after the first Athens Gay Pride (2005), two Greek movies appeared with homosexuality as their central theme. The first one 'The Blue Dress', a drama about the journey of a young boy till he turns int...

  4. Rapid differentiation in a sill-like magma reservoir: a case study from the campi flegrei caldera.

    Science.gov (United States)

    Pappalardo, Lucia; Mastrolorenzo, Giuseppe

    2012-01-01

    In recent decades, geophysical investigations have detected wide magma reservoirs beneath quiescent calderas. However, the discovery of partially melted horizons inside the crust is not sufficient to put constraints on capability of reservoirs to supply cataclysmic eruptions, which strictly depends on the chemical-physical properties of magmas (composition, viscosity, gas content etc.), and thus on their differentiation histories. In this study, by using geochemical, isotopic and textural records of rocks erupted from the high-risk Campi Flegrei caldera, we show that the alkaline magmas have evolved toward a critical state of explosive behaviour over a time span shorter than the repose time of most volcanic systems and that these magmas have risen rapidly toward the surface. Moreover, similar results on the depth and timescale of magma storage were previously obtained for the neighbouring Somma-Vesuvius volcano. This consistency suggests that there might be a unique long-lived magma pool beneath the whole Neapolitan area.

  5. THE VISCOUS TO BRITTLE TRANSITION IN CRYSTAL- AND BUBBLE-BEARING MAGMAS

    Directory of Open Access Journals (Sweden)

    Mattia ePistone

    2015-11-01

    Full Text Available The transition from viscous to brittle behaviour in magmas plays a decisive role in determining the style of volcanic eruptions. While this transition has been determined for one- or two-phase systems, it remains poorly constrained for natural magmas containing silicic melt, crystals, and gas bubbles. Here we present new experimental results on shear-induced fracturing of three-phase magmas obtained at high-temperature (673-1023 K and high-pressure (200 MPa conditions over a wide range of strain-rates (5·10-6 s-1 to 4·10-3 s-1. During the experiments bubbles are deformed (i.e. capillary number are in excess of 1 enough to coalesce and generate a porous network that potentially leads to outgassing. A physical relationship is proposed that quantifies the critical stress required for magmas to fail as a function of both crystal (0.24 to 0.65 and bubble volume fractions (0.09 to 0.12. The presented results demonstrate efficient outgassing for low crystal fraction ( 0.44 promote gas bubble entrapment and inhibit outgassing. The failure of bubble-free, crystal-bearing systems is enhanced by the presence of bubbles that lower the critical failure stress in a regime of efficient outgassing, while the failure stress is increased if bubbles remain trapped within the crystal framework. These contrasting behaviours have direct impact on the style of volcanic eruptions. During magma ascent, efficient outgassing reduces the potential for an explosive eruption and favours brittle behaviour, contributing to maintain low overpressures in an active volcanic system resulting in effusion or rheological flow blockage of magma at depth. Conversely, magmas with high crystallinity experience limited loss of exsolved gas, permitting the achievement of larger overpressures prior to a potential sudden transition to brittle behaviour, which could result in an explosive volcanic eruption.

  6. The chemical and isotopic differentiation of an epizonal magma body: Organ Needle pluton, New Mexico

    Science.gov (United States)

    Verplanck, P.L.; Farmer, G.L.; McCurry, M.; Mertzman, S.A.

    1999-01-01

    Major and trace element, and Nd and Sr isotopic compositions of whole rocks and mineral separates from the Oligocene, alkaline Organ Needle pluton (ONP), southern New Mexico, constrain models for the differentiation of the magma body parental to this compositionally zoned and layered epizonal intrusive body. The data reveal that the pluton is rimmed by lower ??(Nd) (~-5) and higher 87Sr/86Sr (~0.7085) syenitic rocks than those in its interior (??(Nd) ~ 2, 87Sr/86Sr ~0.7060) and that the bulk compositions of the marginal rocks become more felsic with decreasing structural depth. At the deepest exposed levels of the pluton, the ??(Nd)~-5 lithology is a compositionally heterogeneous inequigranular syenite. Modal, compositional and isotopic data from separates of rare earth element (REE)-bearing major and accesory mineral phases (hornblende, titanite, apatite, zircon) demonstrate that this decoupling of trace and major elements in the inequigranular syenite results from accumulation of light REE (LREE)-bearing minerals that were evidently separated from silicic magmas as the latter rose along the sides of the magma chamber. Chemical and isotopic data for microgranular mafic enclaves, as well as for restite xenoliths of Precambrian granite wall rock, indicate that the isotopic distinction between the marginal and interior facies of the ONP probably reflects assimilation of the wall rock by ??(Nd) ~-2 mafic magmas near the base of the magma system. Fractional crystallization and crystal liquid separation of the crystally contaminated magma at the base and along the margins of the chamber generated the highly silicic magmas that ultimately pooled at the chamber top.

  7. Finite-element modeling of magma chamber-host rock interactions prior to caldera collapse

    Science.gov (United States)

    Kabele, Petr; Žák, Jiří; Somr, Michael

    2017-06-01

    Gravity-driven failure of shallow magma chamber roofs and formation of collapse calderas are commonly accompanied by ejection of large volumes of pyroclastic material to the Earth's atmosphere and thus represent severe volcanic hazards. In this respect, numerical analysis has proven as a key tool in understanding the mechanical conditions of caldera collapse. The main objective of this paper is to find a suitable approach to finite-element simulation of roof fracturing and caldera collapse during inflation and subsequent deflation of shallow magma chambers. Such a model should capture the dominant mechanical phenomena, for example, interaction of the host rock with magma and progressive deformation of the chamber roof. To this end, a comparative study, which involves various representations of magma (inviscid fluid, nearly incompressible elastic, or plastic solid) and constitutive models of the host rock (fracture and plasticity), was carried out. In particular, the quasi-brittle fracture model of host rock reproduced well the formation of tension-induced radial and circumferential fractures during magma injection into the chamber (inflation stage), especially at shallow crustal levels. Conversely, the Mohr-Coulomb shear criterion has shown to be more appropriate for greater depths. Subsequent magma withdrawal from the chamber (deflation stage) results in further damage or even collapse of the chamber roof. While most of the previous studies of caldera collapse rely on the elastic stress analysis, the proposed approach advances modeling of the process by incorporating non-linear failure phenomena and nearly incompressible behaviour of magma. This leads to a perhaps more realistic representation of the fracture processes preceding roof collapse and caldera formation.

  8. Origin of silicic magmas along the Central American volcanic front: Genetic relationship to mafic melts

    Science.gov (United States)

    Vogel, Thomas A.; Patino, Lina C.; Eaton, Jonathon K.; Valley, John W.; Rose, William I.; Alvarado, Guillermo E.; Viray, Ela L.

    2006-09-01

    Silicic pyroclastic flows and related deposits are abundant along the Central American volcanic front. These silicic magmas erupted through both the non-continental Chorotega block to the southeast and the Paleozoic continental Chortis block to the northwest. The along-arc variations of the silicic deposits with respect to diagnostic trace element ratios (Ba/La, U/Th, Ce/Pb), oxygen isotopes, Nd and Sr isotope ratios mimic the along-arc variation in the basaltic and andesitic lavas. This variation in the lavas has been interpreted to indicate relative contributions from the slab and asthenosphere to the basaltic magmas [Carr, M.J., Feigenson, M.D., Bennett, E.A., 1990. Incompatible element and isotopic evidence for tectonic control of source mixing and melt extraction along the Central American arc. Contributions to Mineralogy and Petrology, 105, 369-380.; Patino, L.C., Carr, M.J. and Feigenson, M.D., 2000. Local and regional variations in Central American arc lavas controlled by variations in subducted sediment input. Contributions to Mineralogy and Petrology, 138 (3), 265-283.]. With respect to along-arc trends in basaltic lavas the largest contribution of slab fluids is in Nicaragua and the smallest input from the slab is in central Costa Rica — similar trends are observed in the silicic pyroclastic deposits. Data from melting experiments of primitive basalts and basaltic andesites demonstrate that it is difficult to produce high K 2O/Na 2O silicic magmas by fractional crystallization or partial melting of low-K 2O/Na 2O sources. However fractional crystallization or partial melting of medium- to high-K basalts can produce these silicic magmas. We interpret that the high-silica magmas associated Central America volcanic front are partial melts of penecontemporaneous, mantle-derived, evolved magmas that have ponded and crystallized in the mid-crust — or are melts extracted from these nearly completely crystallized magmas.

  9. Temperatures and isotopic evolution of silicic magmas, Taupo Volcanic Zone and Coromandel, New Zealand

    International Nuclear Information System (INIS)

    Blattner, P.; Rui-Zhong, Hu; Graham, I.J.; Houston-Eleftheriadis, C.

    1996-01-01

    A new set of oxygen and strontium isotope data on rhyolitic lavas and ignimbrites of the Taupo Volcanic Zone (TVZ) and the Coromandel Peninsula provides new limits for petrogenetic models. For oxygen isotopes, the rock matrix is frequently altered, so that values for magma need to be phenocryst based. Within TVZ a trend towards more negative delta 1 8 O values for more recent magmas appears likely (average before about 1 Ma and for Coromandel near 8.0 per thousand; after 1 Ma near 7.5 per thousand). This could indicate the gradual removal of supracrustal contaminants from the zones of magma accumulation and extrusion. Similar trends within Coromandel cannot yet be resolved. A generally positive correlation is found for oxygen and strontium isotopes of magmas. Most magmas have a limited range of isotopic values, which then becomes a useful fingerprint (e.g., the Mamaku, Matahina, and Waiotapu Ignimbrites). A narrow range of eruption temperatures of 880 plus or minus 60degC is derived from quartz-plagioclase fractionations of 0.98 plus or minus 0.25 per thousand delta 1 8 O for 15 magmas. Some delta 1 8 O values of quartz and feldspar phenocrysts are sufficiently low to suggest interaction between surface water and magma. However, large negative oxygen isotope anomalies (such as known from Yellowstone), could be no more than partially concealed by the isotopically less depleted meteoric water of New Zealand, and have not yet been found in New Zealand. (author). 45 refs., 3 tabs., 6 figs

  10. Sr and Nd isotope geochemistry of coexisting alkaline magma series, Cantal, Massif Central, France

    International Nuclear Information System (INIS)

    Downes, H.

    1984-01-01

    Sr and Nd isotope analyses are presented for Tertiary continental alkaline volcanics from Cantal, Massif Central, France. The volcanics belong to two main magma series, silica-saturated and silica-undersaturated (with rare nephelinites). Trace element and isotopic data indicate a common source for the basic parental magmas of both major series; the nephelinites in contrast must have been derived from a mantle source which is isotopically and chemically distinct from that which gave rise to the basalts and basanites. 87 Sr/ 86 Sr initial ratios range from 0.7034 to 0.7056 in the main magma series (excluding rhyolites) and 143 Nd/ 144 Nd ratios vary between 0.512927 and 0.512669; both are correlated with increasing SiO 2 in the lavas. The data can be explained by a model of crustal contamination linked with fractional crystallisation. This indicates that crustal magma chambers are the sites of differentiation since only rarely do evolved magmas not show a crustal isotopic signature and conversely basic magmas have primitive isotopic ratios unless they contain obviuos crustal-derived xenocrysts. Potential contaminants include lower crustal granulites or partial melts of upper crustal units. Equal amounts of contamination are required for both magma series, refuting hypotheses of selective contamination of the silica-saturated series. The isotopic characteristics of the apparently primary nephelinite lavas demonstrates widespread heterogeneity in the mantle beneath Cantal. Some rhyolites, previously thought to be extremely contaminated or to be crustally derived, are shown to have undergone post-emplacement hydrothermal alteration. (orig.)

  11. Growing magma chambers control the distribution of small-scale flood basalts.

    Science.gov (United States)

    Yu, Xun; Chen, Li-Hui; Zeng, Gang

    2015-11-19

    Small-scale continental flood basalts are a global phenomenon characterized by regular spatio-temporal distributions. However, no genetic mechanism has been proposed to explain the visible but overlooked distribution patterns of these continental basaltic volcanism. Here we present a case study from eastern China, combining major and trace element analyses with Ar-Ar and K-Ar dating to show that the spatio-temporal distribution of small-scale flood basalts is controlled by the growth of long-lived magma chambers. Evolved basalts (SiO2 > 47.5 wt.%) from Xinchang-Shengzhou, a small-scale Cenozoic flood basalt field in Zhejiang province, eastern China, show a northward younging trend over the period 9.4-3.0 Ma. With northward migration, the magmas evolved only slightly ((Na2O + K2O)/MgO = 0.40-0.66; TiO2/MgO = 0.23-0.35) during about 6 Myr (9.4-3.3 Ma). When the flood basalts reached the northern end of the province, the magmas evolved rapidly (3.3-3.0 Ma) through a broad range of compositions ((Na2O + K2O)/MgO = 0.60-1.28; TiO2/MgO = 0.30-0.57). The distribution and two-stage compositional evolution of the migrating flood basalts record continuous magma replenishment that buffered against magmatic evolution and induced magma chamber growth. Our results demonstrate that the magma replenishment-magma chamber growth model explains the spatio-temporal distribution of small-scale flood basalts.

  12. Shallow-level magma-sediment interaction and explosive behaviour at Anak Krakatau (Invited)

    Science.gov (United States)

    Troll, V. R.; Jolis, E. M.; Dahren, B.; Deegan, F. M.; Blythe, L. S.; Harris, C.; Berg, S. E.; Hilton, D. R.; Freda, C.

    2013-12-01

    Crustal contamination of ascending arc magmas is generally thought to be a significant process which occurs at lower- to mid-crustal magma storage levels where magmas inherit their chemical and isotopic character by blending, assimilation and differentiation [1]. Anak Krakatau, like many other volcanoes, erupts shallow-level crustal xenoliths [2], indicating a potential role for upper crustal modification and hence late-stage changes to magma rheology and thus potential eruptive behaviour. Distinguishing deep vs. shallow crustal contamination processes at Krakatau, and elsewhere, is therefore crucial to understand and assess pre-eruptive magmatic conditions and their associated hazard potential. Here we report on a multi-disciplinary approach to unravel the crustal plumbing system of the persistently-active and dominantly explosive Anak Krakatau volcano [2, 3], employing rock-, mineral- and gas-isotope geochemistry and link these results with seismic tomography [4]. We show that pyroxene crystals formed at mid- and lower-crustal levels (9-11 km) and carry almost mantle-like isotope signatures (O, Sr, Nd, He), while feldspar crystals formed dominantly at shallow levels (< 5km) and display unequivocal isotopic evidence for late stage contamination (O, Sr, Nd). This obeservation places a significant element of magma-crust interaction into the uppermost, sediment-rich crust beneath the volcano. Magma storage in the uppermost crust can thus offer a possible explanation for the compositional modifications of primitive Krakatau magmas, and likely provides extra impetus to increased explosivity at Anak Krakatau. [1] Annen, et al., 2006. J. Petrol. 47, 505-539. [2] Gardner, et al., 2013. J. Petrol. 54, 149-182. [3] Dahren, et al., 2012. Contrib. Mineral. Petrol. 163, 631-651. [4] Jaxybulatov, et al., 2011. J. Volcanol. Geoth. Res. 206, 96-105.

  13. Isotopic disequilibrium among commingled hybrid magmas: Evidence for a two-stage magma mixing-commingling process in the Mt. Perkins Pluton, Arizona

    International Nuclear Information System (INIS)

    Metcalf, R.V.; Smith, E.I.; Reed, R.C.

    1995-01-01

    The syn-extensional Miocene Mt. Perkins pluton, northwestern Arizona, cooled rapidly due to its small size (6 km 2 ) and shallow emplacement (7.5 km) and allows examination of commingled rocks that experienced little isotopic exchange. Within the pluton, quartz dioritic to granodioritic host rocks (58-68 wt% SiO 2 ) enclose dioritic enclaves (50-55 wt% SiO 2 ) and a portion contains enclave-free granodiorite (70-74 wt% SiO 2 ). Fine-grained, crenulate enclave margins and a lack of advanced mixing structures (e.g., schlieren, flow fabrics, etc.) indicate an incipient stage of commingling. Isotopic variation between enclaves and enclosing host rocks is large (6.8 to 10.6 ε Nd units; 0.0036 to 0.0046 87 Sr/ 86 Sr units), suggesting isotopic disequilibrium. Comparison of an enclave core and rim suggests that isotopic exchange with the host magma was limited to the enclave rim. Enclaves and hosts collectively form a calc-alkaline suite exhibiting a large range of ε Nd (+1.2 to -12.5) and initial 87 Sr/ 86 Sr (0.705 to 0.71267) with a correlation among ε Nd , initial 87 Sr/ 86 Sr, and major and trace element compositions. Modeling suggests that the suite formed by magma hybridization involving magma mixing accompanied by fractional crystallization. The magma mixing must have predated commingling at the present exposure level and indicates a larger mixing chamber at depth. Isotopic and trace element data suggests mixing end-members were asthenospheric mantle-derived mafic and crustal-derived felsic magmas. Fractional crystallization facilitated mixing by reducing the rheological contrasts between the mafic and felsic mixing end-members. 58 refs., 11 figs., 3 tabs

  14. INTERACTIONS BETWEEN GABBROID AND GRANITOID MAGMAS DURING FORMATION OF THE PREOBRAZHENSKY INTRUSION, EAST KAZAKHSTAN

    Directory of Open Access Journals (Sweden)

    S. V. Khromykh

    2017-01-01

    Full Text Available The paper reports on studies of the Preobrazhensky gabbro‐granitoid intrusion, East Kazakhstan, com‐ posed of the rocks that belong to four phases of intrusion, from quartz monzonites and gabbroids to granite‐ leucogranites. Specific relationships between basite and granitoid rocks are usually classified as the result of interac‐ tions and mixing of liquid magmas, i.e. magma mingling and mixing. Basite rocks are represented by a series from biotite gabbros to monzodiorites. Granitoids rocks are biotite‐amphibole granites. Porphyric granosyenites, com‐ bining the features of both granites and monzodiorites, are also involved in mingling. It is established that the primary granitoid magmas contained granosyenite/quartz‐monzonite and occurred in the lower‐medium‐crust conditions in equilibrium with the garnet‐rich restite enriched with plagioclase. Monzodiorites formed during fractionation of the parent gabbroid magma that originated from the enriched mantle source. We propose a magma interaction model describing penetration of the basite magma into the lower horizons of the granitoid source, which ceased below the viscoplastic horizon of granitoids. The initial interaction assumes the thermal effect of basites on the almost crystal‐ lized granitic magma and saturation of the boundary horizons of the basite magma with volatile elements, which can change the composition of the crystallizing melt from gabbroid to monzodiorite. A ‘boundary’ layer of monzodiorite melt is formed at the boundary of the gabbroid and granitoid magmas, and interacts with granitoids. Due to chemical interactions, hybrid rocks – porphyric granosyenites – are formed. The heterogeneous mixture of monzodiorites and granosyenites is more mobile in comparison with the overlying almost crystallized granites. Due to contraction frac‐ turing in the crystallized granites, the heterogeneous mixture of monzodiorites and granosyenites penetrate into the

  15. Reaction of Rhyolitic Magma to its Interception by the IDDP-1 Well, Krafla, 2009

    Science.gov (United States)

    Saubin, É.; Kennedy, B.; Tuffen, H.; Villeneuve, M.; Watson, T.; Nichols, A. R.; Schipper, I.; Cole, J. W.; Mortensen, A. K.; Zierenberg, R. A.

    2017-12-01

    The unexpected encounter of rhyolitic magma during IDDP-1 geothermal borehole drilling at Krafla, Iceland in 2009, temporarily created the world's hottest geothermal well. This allowed new questions to be addressed. i) How does magma react to drilling? ii) Are the margins of a magma chamber suitable for long-term extraction of supercritical fluids? To investigate these questions, we aim to reconstruct the degassing and deformation behaviour of the enigmatic magma by looking for correlations between textures in rhyolitic material retrieved from the borehole and the recorded drilling data. During drilling, difficulties were encountered in two zones, at 2070 m and below 2093 m depth. Drilling parameters are consistent with the drill bit encountering a high permeability zone and the contact zone of a magma chamber, respectively. Magma was intercepted three times between 2101-2104.4 m depth, which culminated in an increase in standpipe pressure followed by a decrease in weight on bit interpreted as representing the ascent of magma within the borehole. Circulation returned one hour after the last interception, carrying cuttings of glassy particles, felsite with granophyre and contaminant clasts from drilling, which were sampled as a time-series for the following 9 hours. The nature of glassy particles in this time-series varied through time, with a decrease in the proportion of vesicular clasts and a commensurate increase in dense glassy clasts, transitioning from initially colourless to brown glass. Componentry data show a sporadic decrease in felsite (from 34 wt. %), an increase in glassy particles during the first two hours (from 63 wt. % to 94 wt. %) and an increase in contaminant clasts towards the end of the cutting retrieval period. These temporal variations are probably related to the magma body architecture and interactions with the borehole. Transition from vesicular to dense clasts suggests a change in the degassing process that could be related to an early

  16. Evolution of silicic magmas in the Kos-Nisyros volcanic center: cycles associated with caldera collapse

    Science.gov (United States)

    Ruprecht, J. S.; Bachmann, O.; Deering, C. D.; Huber, C.; Skopelitis, A.; Schnyder, C.

    2010-12-01

    Multiple eruptions of silicic magma (dacite and rhyolites) occurred over the last ~ 3 My in the Kos-Nisyros volcanic center (eastern Aegean sea). Over the course of this period, magmas have changed from hornblende-biotite rich units with low eruption temperatures (≤750-800 °C; Kefalos and Kos units) to hotter (>800-850 °C), pyroxene-bearing units (Nisyros units) and are transitioning back to colder magmas (Yali units). Using bulk-rock compositions, mineral chemistry, and zircon Hf isotopes, we show that the two different types of silicic magmas followed the same differentiation trend; they all evolved by crystal fractionation (and minor assimilation) from parents with intermediate compositions characterized by high Sr/Y and low Nb content, following a wet, high oxygen fugacity liquid line of descent typical of subduction zones. As the transition between the Kos-Kefalos and Nisyros-type magmas occurred immediately and abruptly after the major caldera collapse in the area (the 161 ky Kos Plateau Tuff; KPT), we suggest that the efficient emptying of the magma chamber during the KPT drew most of the eruptible magma out and partly froze the silicic magma source zone in the upper crust due to rapid unloading, decompression and resulting crystallization. Therefore, the system had to reinstate a shallow silicic production zone from more mafic parents, recharged at temperatures typically around 850-900 °C from the mid to lower crust. The first silicic eruptions evolving from these parents after the caldera collapse (Nisyros units) were thus slightly hotter and less evolved than the Kefalos-Kos package. However, with time, the upper crustal intermediate mush grew and cooled, leading to interstitial melt compositions reaching again the highly-evolved, cold state that prevailed prior to the Kefalos-Kos. The recent (albeit not precisely dated) eruption of the high-SiO2 rhyolite of Yali suggests that another large, potentially explosive magma chamber is presently building

  17. International Uranium Resources Evaluation Project (IUREP) national favourability studies: Greece

    International Nuclear Information System (INIS)

    1977-10-01

    Greece, with an area of 131,944 km 2 , has been actively explored since 1971 under a programme of co-operation with UNDP and IAEA on which close to US $1 million have been spent so far. The programme is focused on the Rhodope Precambrian massif, which is the most attractive structural unit from the geological point of view. The indications available at present, and which have been known for a long time, are also to be found in this unit. They are associated either with Tertiary continental volcanism or with detritic sediments in basins covering this massif. So far there is no evidence of their being of any economic value. The paucity of data available on the basement of the Rhodope precludes any prediction as to the possibility of its containing Pre-cambrian uranium mineralizations. One might perhaps think in terms of mineralizations of the alaskite or alkaline complex type, or also of vein-type deposits. But it is primarily in the deposits associated with tertiary trachy-rhyolitic volcanism that we have most confidence, especially in the Rhodope massif and the Vardar region but possibly elsewhere in the Hellenides as well. All things considered, we place Greece in Group 2 of the IUREP classification. (author)

  18. Scanning the business external environment for information: evidence from Greece

    Directory of Open Access Journals (Sweden)

    L. Kourteli

    2005-01-01

    Full Text Available Introduction. This paper examines the business external environment scanning theory for information in the context of Greece. Method. A questionnaire was developed to explore the relationships between general and task business environment, perceived uncertainty, scanning strategy, and sources of information with respect to type of environment, size and industry.The research was based on a sample of 144 private organizations operating in North Greece. Analysis. Data collected were analysed using SPSS. The statistical procedures of chi-squared homogeneity test, ANOVA, Duncan's test of homogeneity of means, and related samples t-test were followed for testing the hypotheses developed. Results. The results show that perceived uncertainty of the general and task business external environment factors depend on the type of the environment, size of organization, and industry where the organizations operate; organizations adapt their scanning strategy to the complexity of the environment; personal sources of information seem to be more important than impersonal sources; external sources of information are equally important with internal sources; and higher levels of environmental uncertainty are associated with higher levels of scanning the various sources. Conclusion. Business external environment scanning of information is influenced by the characteristics of the organizations themselves and by the characteristics of the external environment within which the organizations operate. The study contributes to both environmental scanning theory and has important messages for practitioners.

  19. Service quality perceptions in primary health care centres in Greece

    Science.gov (United States)

    Papanikolaou, Vicky; Zygiaris, Sotiris

    2012-01-01

    Abstract Context  The paper refers to the increased competition between health care providers and the need for patient‐centred services in Greece. Using service quality methodology, this paper investigates service quality perceptions of patients in Greek public primary health centres. Objective  To test the internal consistency and applicability of SERVQUAL in primary health care centres in Greece. Strategy  SERVQUAL was used to examine whether patients have different expectations from health care providers and whether different groups of patients may consider some dimensions of care more important than others. Results  The analysis showed that there were gaps in all dimensions measured by SERVQUAL. The largest gap was detected in empathy. Further analysis showed that there were also differences depending on gender, age and education levels. A separate analysis of expectations and perceptions revealed that this gap was because of differences in patients’ perceptions rather than expectations. Discussion and conclusions  This paper raises a number of issues that concern the applicability of SERVQUAL in health care services and could enhance current discussions about SERVQUAL improvement. Quality of health care needs to be redefined by encompassing multiple dimensions. Beyond a simple expectations–perceptions gap, people may hold different understandings of health care that, in turn, influence their perception of the quality of services. PMID:22296402

  20. The solar thermal market in Greece - review and perspectives

    International Nuclear Information System (INIS)

    Argiriou, A.A.; Mirasgedis, S.

    2003-01-01

    The Hellenic solar thermal market is actually one of the most developed worldwide. This paper provides an overview of the evolution of this market since its start in the mid-1970s until today. The reasons for its success are discussed in detail: the role of the manufacturers, the quality assurance practices applied and the incentives on the demand and supply sides. The role of economic instruments towards the development of the Hellenic solar thermal market is investigated using a cost-benefit analysis (CBA). Although commercially successful, solar thermal applications today in Greece still cover a very limited percentage of their potential applications. The perspectives and potential barriers for their future development are presented, analysed by a CBA and discussed. This information is useful for all parties related to this market, manufacturers, potential users, policy makers, etc. Countries having a solar energy potential similar to that of Greece but a less developed solar market may also identify in this work parameters that will contribute to the development of their national market. (author)

  1. Greece Financial Crises and Sukuk Markets: Experience From Gulf Countries

    Directory of Open Access Journals (Sweden)

    Aldrin Herwany

    2016-12-01

    Full Text Available Many studies have been carried out to investigate the impact of recent European financial crises on the performance of financial instruments in other regions. Nevertheless, there have been insufficient studies explaining such impact on Islamic financial instrument. In particular, whether Greece Financial crises have affected performance of Sukuk traded in Gulf Markets needs to be answered. This study is aimed at empirically investigating the causality of credit and liquidity risk on Sukuk Markets in Gulf economies in the period of Greece Financial Crises. We analyzed the Sukuk data by employing Granger casuality test, with all the associated vector autoregression model procedures. Our findings show that Bahrain sukuk market is cointegrated with those of Qatar and UAE in the full period observation. Meanwhile, during the crisis, Qatar Sukuk market is cointegrated with those of UAE Bahrain. We also find that Bahrain Sukuk triggers market shock in both Qatar and UAE Sukuk markets. Bahrain consistently causes changes in price and spread of UAE Sukuk, both in the context of the full period and the during-crisis period.DOI: 10.15408/aiq.v9i1.3733

  2. Organ transplantation in Greece: the need for mediation.

    Science.gov (United States)

    Zanni, A

    2014-11-01

    Organ transplants are not regarded as an exclusively medical process, because they involve financial, religious, philosophic, and bioethical parameters. It becomes clear that if they are to achieve their purpose, which we believe extends well beyond the medical dimension, the creation of a comprehensive framework of communication between the involved parties is of paramount importance. The aim of this paper is to present an outline and a number of considerations regarding the communicational, bioethical, and legal issues that arise from a rather dramatic state of affairs in Greece today: In 2012 the rate of organ transplants stood at only 7 per 1 million of the population. The outdated legal framework and the lack of trust on the part of patients and the public have led to a highly inefficient system that is lagging behind in many respects. The proposition made in this paper is that there is a need for a new system of communication between doctors, patients, relatives of patients, and hospitals: bioethical mediation. This is a system that has played a vital role and has produced astounding results in other countries. There is also every indication that the introduction of such a system is crucial for Greece, especially as the symptoms of the acute financial crisis are become fully visible and tangible. Mediation aims to identify solutions that are oriented toward the interests and wishes of patients, are acknowledged and accepted by all parties involved, and are in tune with the values and the principles of medical practice.

  3. The epidemiology of benign prostatic hyperplasia: a study in Greece.

    Science.gov (United States)

    Signorello, L B; Tzonou, A; Lagiou, P; Samoli, E; Zavitsanos, X; Trichopoulos, D

    1999-08-01

    To assess the epidemiology of benign prostatic hyperplasia (BPH) in a case-control study in greater Athens, Greece. The study comprised 184 patients surgically treated for BPH within one year of its diagnosis (cases) and 246 patients with no symptoms of BPH who were treated in the same hospitals for minor diseases or conditions (controls). All cases and controls were permanent residents of the greater Athens area, Greece. The data were assessed using unconditional logistic regression. After controlling for age and education, cases and controls had similar distributions for height, body mass index, sibship size and birth order in the parental family, marital status, number of offspring and a series of previous medical diagnoses or surgical operations. The sole exception was surgery for haemorrhoids, that appeared to be related to the incidence of BPH, possibly by chance. There was no evidence that vertex baldness, tobacco smoking, alcohol consumption or coffee drinking increased the risk for BPH. Men who had spent most of their lives in a rural rather than an urban environment appeared to be at reduced risk for BPH. The lifestyle factors assessed here have no major effect on the aetiology of BPH.

  4. Future prospects for the management of radioactive waste in greece

    International Nuclear Information System (INIS)

    Savidou, A.

    2015-01-01

    In Greece, there isn.t yet any decision for construction of a disposal facility. Since the predisposal management of radioactive waste should be aligned with the disposal solutions, the determination of the disposal options is essential for the selection of the technology needed for treatment and conditioning of the wastes. The scope of the present study is the investigation of the disposal options for Greece. Firstly, the study deals with the preliminary inventory as well as the classification of the existing radioactive waste and the prediction of the expected waste from decommissioning of the open pool type at 5 MW Greek Research Reactor (GRR-1). The existing radioactive waste includes the institutional waste from the operation of GRR-1 and associated facilities as well as orphan sources and other radioactive items collected in the frame of emergency by the Greek Atomic Energy Commission (GAEC) and kept at the interim storage of the National Centre for Scientific Research ''Demokritos'' NCSR ''D''. Based on the present inventory of radioactive waste, the establishment of a small scale and LILW geological repository seems to be the appropriate and most acceptable by the public disposal solution. (authors)

  5. Shame and Anxiety Feelings of a Roma Population in Greece.

    Science.gov (United States)

    Gouva, M; Mentis, M; Kotrotsiou, S; Paralikas, Th; Kotrotsiou, E

    2015-12-01

    Shame is a crucial issue for Roma. The purpose of the present study was to evaluate the severity of shame and anxiety feelings in a Roma population living in Greece and assess the differentiation of these feelings between Roma men and women. A quota sample of 194 Roma adult men and women living in Southern Greece was retrieved. The Experiences of Shame Scale (ESS), the Other As Shamer Scale (OAS) and the Spielberg's State/Trait Anxiety Inventory (STAI) questionnaires were used. Women scored statistically significantly higher than men on ESS, whereas men scored higher on OAS scale (52.27 ± 16.91 vs 45.42 ± 9.98 and 35.93 ± 16.94 vs 30.87 ± 13.72 respectively). Women scored higher than men in both STAI subscales, however significant differences were observed only in State Anxiety scale (48.83 ± 9.26 vs 43.20 ± 9.81). OAS total score was inversely related to state anxiety, whereas ESS total score was positive related to trait anxiety, all correlations being significant at p Cultural, social and minority issues contribute to feelings of inferiority and anxiety experience.

  6. Decadal changes in extreme daily precipitation in Greece

    Directory of Open Access Journals (Sweden)

    P. T. Nastos

    2008-04-01

    Full Text Available The changes in daily precipitation totals in Greece, during the 45-year period (1957–2001 are examined. The precipitation datasets concern daily totals recorded at 21 surface meteorological stations of the Hellenic National Meteorological Service, which are uniformly distributed over the Greek region. First and foremost, the application of Factor Analysis resulted in grouping the meteorological stations with similar variation in time. The main sub groups represent the northern, southern, western, eastern and central regions of Greece with common precipitation characteristics. For representative stations of the extracted sub groups we estimated the trends and the time variability for the number of days (% exceeding 30 mm (equal to the 95% percentile of daily precipitation for eastern and western regions and equal to the 97.5% percentile for the rest of the country and 50 mm which is the threshold for very extreme and rare events. Furthermore, the scale and shape parameters of the well fitted gamma distribution to the daily precipitation data with respect to the whole examined period and to the 10-year sub periods reveal the changes in the intensity of the precipitation.

  7. Service quality perceptions in primary health care centres in Greece.

    Science.gov (United States)

    Papanikolaou, Vicky; Zygiaris, Sotiris

    2014-04-01

    The paper refers to the increased competition between health care providers and the need for patient-centred services in Greece. Using service quality methodology, this paper investigates service quality perceptions of patients in Greek public primary health centres. To test the internal consistency and applicability of SERVQUAL in primary health care centres in Greece. SERVQUAL was used to examine whether patients have different expectations from health care providers and whether different groups of patients may consider some dimensions of care more important than others. The analysis showed that there were gaps in all dimensions measured by SERVQUAL. The largest gap was detected in empathy. Further analysis showed that there were also differences depending on gender, age and education levels. A separate analysis of expectations and perceptions revealed that this gap was because of differences in patients' perceptions rather than expectations. THIS paper raises a number of issues that concern the applicability of SERVQUAL in health care services and could enhance current discussions about SERVQUAL improvement. Quality of health care needs to be redefined by encompassing multiple dimensions. Beyond a simple expectations-perceptions gap, people may hold different understandings of health care that, in turn, influence their perception of the quality of services. © 2012 John Wiley & Sons Ltd.

  8. Preliminary study on the flow field over Greece

    International Nuclear Information System (INIS)

    Pissimanis, D; Karras, G; Notaridou, V; Bartzis, J.G.

    1989-02-01

    Full text: For radiation risk assessment from long distance sources, the knowledge of the synoptic air flow field patterns over the territory under consideration is required. In the present study a first representation of the air flow field in the atmospheric boundary layer over Greece is attempted. For this purpose, synoptic weather maps at 850mb available for a ten-years period, as well as sounding data from six meteorological stations were utilized, while the Greek territory was divided into four parts, i.e. NW, NE, SW, SE, with a number of stations in each sector. It was shown that the prevailing wind directions of the upper flow are either of the W/SW sector (winter, spring) or the northern sector (summer, autumn). In the SE sector a stronger tendency towards winds from the nothern sector was shown, due to the thermal low near Cyprus. The main characteristics of the surface flow is the strong influence by topographical features. Typical examples are the strong NW winds in Northern Greece due to the Vardar Valley, and the sea breeze circulations at coastal environments. (author)

  9. Top Income Shares in Greece: 1957-2010

    Directory of Open Access Journals (Sweden)

    Kostas Chrissis

    2013-11-01

    Full Text Available This paper analyses the evolution of top income shares in Greece for the period 1957 to 2010 following Piketty (2001 methodology. We present the 10%, 5%, 2.5%, 2%, 1.5%, 1%, 0.5% and 0.1% income shares estimates which are based on tax statistics. The empirical results indicate that the behavior of the alternative estimated top income shares is quite similar. A ‘flat’ Ushaped pattern for most cases seems to exist. This common pattern is more apparent for the 2.5-0.1% top income shares. The top 10% and 5% income shares seem to be more volatile, accompanied with an increasing trend by the end of the period. This paper is an attempt to extend the existing research in southern Europe by presenting the relevant Greek experience. For the whole period, country comparisons show that the 1% top income share in Greece is in lower levels than that of USA and the other European countries (Italy, Portugal, Spain, France, Germany.

  10. Update of indicators for climate change mitigation in Greece

    International Nuclear Information System (INIS)

    Dimitroulopoulou, C.; Ziomas, I.

    2011-01-01

    This paper analyses the factors affecting greenhouse gas (GHG) emissions in Greece, (i.e. the drivers of pressures on climate change), using environmental indicators related to energy, demographics and economic growth. The analysis is based on the data of 2008 and considers types of fuel and sectors. The Kaya identity is used to identify the relationship between drivers and pressures, using annual time series data of National GHG emissions, population, energy consumption and gross domestic product. The analysis shows that over the period 2000-2008, GHG emissions show a slight variation, but they are almost stabilised, with a total increase of 1.6%. Despite the economic growth over that period, this stabilisation may be considered as a combination of reductions in the energy intensity of GDP and the carbon intensity of energy, which are affected by improvements in energy efficiency and introduction of 'cleaner' fuels, such as natural gas and renewables in the energy mixture of the country. - Highlights: → We analyse drivers affecting GHG emissions (pressures on climate) in Greece, using indicators. → Indicators relate to energy, demographics and economic growth. → Kaya identity identifies the relationship between drivers and pressures. → GHG emissions are almost stable due to reductions in energy intensity and carbon intensity of energy. → Improvements in energy efficiency and introduction of clean fuels in energy mix reduce emissions.

  11. The number and its symbolism in ancient Greece

    Directory of Open Access Journals (Sweden)

    Doc. dr Milena Bogdanović

    2013-07-01

    Full Text Available The symbols are of particular importance. They are the heart of the creative life; rather they are its core. They reveal the secrets of the unconscious mind open to the unknown and the infinite. While talking or gestures while express, we use the symbols, noting it or not. All spiritual science, all art and all art techniques encounter on their way symbols. History confirms that the symbols of each object can be obtained symbolic value, whether natural (rocks, trees, animals, planets, fire, lightning, etc... or abstract (geometrical shape, number, pace, ideas, etc.... The use of numbers as symbols is as old as language itself, but one that precedes writing, which symbolize numbers (that is, where the reality behind the external characters. The sheer numbers and their symbolism in ancient Greece and is closely associated with the philosophy and mathematics (namely arithmetic. They summarize their view of the world and everything around them. This paper draws attention to the symbolism of the numbers that were in ancient Greece.

  12. Chronological evidence that the Moon is either young or did not have a global magma ocean.

    Science.gov (United States)

    Borg, Lars E; Connelly, James N; Boyet, Maud; Carlson, Richard W

    2011-08-17

    Chemical evolution of planetary bodies, ranging from asteroids to the large rocky planets, is thought to begin with differentiation through solidification of magma oceans many hundreds of kilometres in depth. The Earth's Moon is the archetypical example of this type of differentiation. Evidence for a lunar magma ocean is derived largely from the widespread distribution, compositional and mineralogical characteristics, and ancient ages inferred for the ferroan anorthosite (FAN) suite of lunar crustal rocks. The FANs are considered to be primary lunar flotation-cumulate crust that crystallized in the latter stages of magma ocean solidification. According to this theory, FANs represent the oldest lunar crustal rock type. Attempts to date this rock suite have yielded ambiguous results, however, because individual isochron measurements are typically incompatible with the geochemical make-up of the samples, and have not been confirmed by additional isotopic systems. By making improvements to the standard isotopic techniques, we report here the age of crystallization of FAN 60025 using the (207)Pb-(206)Pb, (147)Sm-(143)Nd and (146)Sm-(142)Nd isotopic systems to be 4,360 ± 3 million years. This extraordinarily young age requires that either the Moon solidified significantly later than most previous estimates or the long-held assumption that FANs are flotation cumulates of a primordial magma ocean is incorrect. If the latter is correct, then much of the lunar crust may have been produced by non-magma-ocean processes, such as serial magmatism.

  13. Timing of Crystallisation of the Lunar Magma Ocean Constrained by the Oldest Zircon

    Science.gov (United States)

    Nemchin, A.; Timms, N.; Pidgeon, R.; Geisler, T.; Reddy, S.; Meyer, C.

    2009-01-01

    The presently favoured concept for the early evolution of the Moon involves consolidation of debris from a giant impact of a Mars sized body with Earth forming a primitive Moon with a thick global layer of melt referred to as the Lunar Magma Ocean1 . It is widely accepted that many significant features observed on the Moon today are the result of crystallisation of this magma ocean. However, controversy exists over the precise timing and duration of the crystallisation process. Resolution of this problem depends on the establishment of precise and robust key crystallisation time points. We report a 4417 6 Myr old zircon in lunar breccia sample 72215,195, which provides a precisely determined younger limit for the solidification of the Lunar Magma Ocean. A model based on these data, together with the age of the Moon forming giant impact, defines an exponential time frame for crystallisation and suggests formation of anorthositic crust after about 80-85% of the magma ocean was solidified. In combination with other zircon ages the 4417 +/- 6 Myr age also suggests that the very small (less than a few per cent) residual portion of the magma ocean continued to solidify during the following 300-500 m.y.

  14. Transport of metals and sulphur in magmas by flotation of sulphide melt on vapour bubbles

    Science.gov (United States)

    Mungall, J. E.; Brenan, J. M.; Godel, B.; Barnes, S. J.; Gaillard, F.

    2015-03-01

    Emissions of sulphur and metals from magmas in Earth’s shallow crust can have global impacts on human society. Sulphur-bearing gases emitted into the atmosphere during volcanic eruptions affect climate, and metals and sulphur can accumulate in the crust above a magma reservoir to form giant copper and gold ore deposits, as well as massive sulphur anomalies. The volumes of sulphur and metals that accumulate in the crust over time exceed the amounts that could have been derived from an isolated magma reservoir. They are instead thought to come from injections of multiple new batches of vapour- and sulphide-saturated magmas into the existing reservoirs. However, the mechanism for the selective upward transfer of sulphur and metals is poorly understood because their main carrier phase, sulphide melt, is dense and is assumed to settle to the bottoms of magma reservoirs. Here we use laboratory experiments as well as gas-speciation and mass-balance models to show that droplets of sulphide melt can attach to vapour bubbles to form compound drops that float. We demonstrate the feasibility of this mechanism for the upward mobility of sulphide liquids to the shallow crust. Our work provides a mechanism for the atmospheric release of large amounts of sulphur, and contradicts the widely held assumption that dense sulphide liquids rich in sulphur, copper and gold will remain sequestered in the deep crust.

  15. Onset of solid state mantle convection and mixing during magma ocean solidification

    Science.gov (United States)

    Maurice, Maxime; Tosi, Nicola; Samuel, Henri; Plesa, Ana-Catalina; Hüttig, Christian; Breuer, Doris

    2017-04-01

    The fractional crystallization of a magma ocean can cause the formation of a compositional layering that can play a fundamental role for the subsequent long-term dynamics of the interior, for the evolution of geochemical reservoirs, and for surface tectonics. In order to assess to what extent primordial compositional heterogeneities generated by magma ocean solidification can be preserved, we investigate the solidification of a whole-mantle Martian magma ocean, and in particular the conditions that allow solid state convection to start mixing the mantle before solidification is completed. To this end, we performed 2-D numerical simulations in a cylindrical geometry. We treat the liquid magma ocean in a parametrized way while we self-consistently solve the conservation equations of thermochemical convection in the growing solid cumulates accounting for pressure-, temperature- and, where it applies, melt-dependent viscosity as well as parametrized yield stress to account for plastic yielding. By testing the effects of different cooling rates and convective vigor, we show that for a lifetime of the liquid magma ocean of 1 Myr or longer, the onset of solid state convection prior to complete mantle crystallization is likely and that a significant part of the compositional heterogeneities generated by fractionation can be erased by efficient mantle mixing.

  16. Magmatic architecture within a rift segment: Articulate axial magma storage at Erta Ale volcano, Ethiopia

    Science.gov (United States)

    Xu, Wenbin; Rivalta, Eleonora; Li, Xing

    2017-10-01

    Understanding the magmatic systems beneath rift volcanoes provides insights into the deeper processes associated with rift architecture and development. At the slow spreading Erta Ale segment (Afar, Ethiopia) transition from continental rifting to seafloor spreading is ongoing on land. A lava lake has been documented since the twentieth century at the summit of the Erta Ale volcano and acts as an indicator of the pressure of its magma reservoir. However, the structure of the plumbing system of the volcano feeding such persistent active lava lake and the mechanisms controlling the architecture of magma storage remain unclear. Here, we combine high-resolution satellite optical imagery and radar interferometry (InSAR) to infer the shape, location and orientation of the conduits feeding the 2017 Erta Ale eruption. We show that the lava lake was rooted in a vertical dike-shaped reservoir that had been inflating prior to the eruption. The magma was subsequently transferred into a shallower feeder dike. We also find a shallow, horizontal magma lens elongated along axis inflating beneath the volcano during the later period of the eruption. Edifice stress modeling suggests the hydraulically connected system of horizontal and vertical thin magmatic bodies able to open and close are arranged spatially according to stresses induced by loading and unloading due to topographic changes. Our combined approach may provide new constraints on the organization of magma plumbing systems beneath volcanoes in continental and marine settings.

  17. Towards a comprehensive classification of igneous rocks and magmas

    Science.gov (United States)

    Middlemost, Eric A. K.

    1991-08-01

    QAPF modal classification. The QAPF and TAS classifications are regarded as being of equal validity, with the TAS classification being of more practical value in the classification of the common volcanic rocks and the various magmas conjured up in petrogenetic discussions. A new, comprehensive, hierarchical classification of igneous rocks is introduced, and the petrographic character and systematic position of the various rocks and clans that make up this classification are reviewed.

  18. Cassini Scientist for a Day: an international contest in Greece

    Science.gov (United States)

    Solomonidou, Anezina; Moussas, Xenophon; Xystouris, Georgios; Coustenis, Athena; Lebreton, Jean-Pierre; Katsavrias, Christos; Bampasidis, Georgios; Kyriakopoulos, Konstantinos; Kouloumvakos, Athanasios; Patsou, Ioanna

    2013-04-01

    The Cassini Outreach Team of NASA's Jet Propulsion Laboratory is being organizing a brilliant school contest in Astronomy focusing in the Saturnian system. This essay contest provides school students all around the worlds with the opportunity to get involved in astronomy and astrophysics and planetary sciences in particular. From 2010 the 'Cassini Scientist for a Day' contest has being one of the most successful as well as important outreach activities of ESA and NASA in Greece with hundreds of participants all over Greece. The number of participants is growing rapidly every year. This type of school competition in Greece is particularly important since Astronomy and Astrophysics and Space Sciences, although very popular, are not included in the school curricula and thus students rarely have the opportunity to experience and participate actively in these subjects. For the years 2010 and 2011, the Space Physics Group of the Astronomy, Astrophysics and Mechanics section of the University of Athens in association with external colleagues has been selected as the co-ordinator of NASA for the competition in Greece. Under the guidance of Cassini Outreach team, the members of the Space Physics Group have informed, explained and spread the rules of the competition at primary, secondary and high schools all over Greece. In general, the students have the option to choose Cassini monitoring between three targets of the Saturnian system, which the participants show that will bring the best scientific result. Their arguments should be summarized in an essay of 500 words more or less. They also have the option to do team work through groups of maximum three students. The participation in the contest for 2010 was unexpectedly high and thoroughly satisfied. The winners awarded through a ceremony which was held in the largest amphitheater at the central building of the University of Athens, that was fully packed. The following year 2011 the participation increased up to 300% while

  19. The Dovyren Intrusive Complex (Southern Siberia, Russia): Insights into dynamics of an open magma chamber with implications for parental magma origin, composition, and Cu-Ni-PGE fertility

    Science.gov (United States)

    Ariskin, Alexey; Danyushevsky, Leonid; Nikolaev, Georgy; Kislov, Evgeny; Fiorentini, Marco; McNeill, Andrew; Kostitsyn, Yuri; Goemann, Karsten; Feig, Sandrin T.; Malyshev, Alexey

    2018-03-01

    The Dovyren Intrusive Complex (DIC, Northern Baikal region, 728 Ma) includes the layered dunite-troctolite-gabbronorite Yoko-Dovyren massif (YDM), associated mafic-ultramafic sills, and dykes of olivine-rich to olivine-free gabbronorite. Major rock types of the DIC are presented, including a diversity of olivine orthocumulates to olivine-plagioclase and gabbroic adcumulates, carbonate-contaminated ultramafics and Cu-Ni-PGE mineralisation. Detailed comparisons of complete cross-sections of the YDM in its centre and at the NE and SW margins demonstrate differences in the cumulate succession, mineral chemistry, and geochemical structure that likely reflect variations in parental magma compositions. Combining petrochemical reconstructions for most primitive rocks and calculations using the COMAGMAT-5 model, it is shown that the central and peripheral parts of the intrusion formed by olivine-laden parental magmas ranged in their temperatures by 100 °C, approximately from 1290 °C ( 11 wt% MgO, olivine Fo88) to 1190 °C ( 8 wt% MgO, olivine Fo86). Thermodynamic modelling suggests that the most primitive high-Mg magma was S-undersaturated, whereas its derivatives became S-saturated at T piles to generate poorly-mineralised plagiodunite. In the troctolite and gabbroic parts of the Dovyren chamber, sulphide immiscibility likely occurred at lower temperatures, producing Cu-rich sulphide precursors, which gave rise to the 'platinum group mineral' (PGM-containing) troctolite and low-mineralised PGE-rich anorthosite in the Main Reef. The geochemical structure of the YDM demonstrates C-shaped distributions of TiO2, K2O, P2O5, and incompatible trace elements, which are 3-5 fold depleted in the cumulate rocks from the inner horizons of the intrusion with respect to the relatively thin lower and upper contact zones. In addition, a marked misbalance between estimates of the average composition of the YDM and that of the proposed olivine-laden parental magmas is established. This

  20. Magnetotelluric Investigations of the Yellowstone Caldera: Understanding the Emplacement of Crustal Magma Bodies

    Science.gov (United States)

    Gurrola, R. M.; Neal, B. A.; Bennington, N. L.; Cronin, R.; Fry, B.; Hart, L.; Imamura, N.; Kelbert, A.; Bowles-martinez, E.; Miller, D. J.; Scholz, K. J.; Schultz, A.

    2017-12-01

    Wideband magnetotellurics (MT) presents an ideal method for imaging conductive shallow magma bodies associated with contemporary Yellowstone-Snake River Plain (YSRP) magmatism. Particularly, how do these magma bodies accumulate in the mid to upper crust underlying the Yellowstone Caldera, and furthermore, what role do hydrothermal fluids play in their ascent? During the summer 2017 field season, two field teams from Oregon State University and the University of Wisconsin-Madison installed forty-four wideband MT stations within and around the caldera, and using data slated for joint 3-D inversion with existing seismic data, two 2-D vertical conductivity sections of the crust and upper mantle were constructed. These models, in turn, provide preliminary insight into the emplacement of crustal magma bodies and hydrothermal processes in the YSRP region.

  1. Lava lake level as a gauge of magma reservoir pressure and eruptive hazard

    Science.gov (United States)

    Patrick, Matthew R.; Anderson, Kyle R.; Poland, Michael P.; Orr, Tim R.; Swanson, Donald A.

    2015-01-01

    Forecasting volcanic activity relies fundamentally on tracking magma pressure through the use of proxies, such as ground surface deformation and earthquake rates. Lava lakes at open-vent basaltic volcanoes provide a window into the uppermost magma system for gauging reservoir pressure changes more directly. At Kīlauea Volcano (Hawaiʻi, USA) the surface height of the summit lava lake in Halemaʻumaʻu Crater fluctuates with surface deformation over short (hours to days) and long (weeks to months) time scales. This correlation implies that the lake behaves as a simple piezometer of the subsurface magma reservoir. Changes in lava level and summit deformation scale with (and shortly precede) changes in eruption rate from Kīlauea's East Rift Zone, indicating that summit lava level can be used for short-term forecasting of rift zone activity and associated hazards at Kīlauea.

  2. Influences of magma chamber ellipticity on ring fracturing and eruption at collapse calderas

    International Nuclear Information System (INIS)

    Holohan, Eoghan P; Walsh, John J; Vries, Benjamin van Wyk de; Troll, Valentin R; Walter, Thomas R

    2008-01-01

    Plan-view ellipticity of a pre-caldera magma reservoir, and its influence on the development of caldera ring fracturing and eruptive behaviour, have not previously been subjected to dedicated evaluation. We experimentally simulated caldera collapse into elliptical magma chambers and found that collapse into highly-elliptical chambers produced a characteristic pattern of ring-fault localization and lateral propagation. Although results are preliminary, the general deformation pattern for elliptical resurgence shows strong similarities to elliptical collapse. Ring faults accommodating uplift again initiate around the chamberos short axis and are reverse, but dip inward. Field and geophysical observations at several elliptical calderas of varying scale (e.g. Long Valley, Katmai, and Rabaul calderas) are consistent with a control from elliptical magma chamber geometry on ring fracturing and eruption, as predicted from our experiments.

  3. Modeling the Daly Gap: The Influence of Latent Heat Production in Controlling Magma Extraction and Eruption

    Science.gov (United States)

    Nelson, B. K.; Ghiorso, M. S.; Bachmann, O.; Dufek, J.

    2011-12-01

    A century-old issue in volcanology is the origin of the gap in chemical compositions observed in magmatic series on ocean islands and arcs - the "Daly Gap". If the gap forms during differentiation from a mafic parent, models that predict the dynamics of magma extraction as a function of chemical composition must simulate a process that results in volumetrically biased, bimodal compositions of erupted magmas. The probability of magma extraction is controlled by magma dynamical processes, which have a complex response to magmatic heat evolution. Heat loss from the magmatic system is far from a simple, monotonic function of time. It is modified by the crystallization sequence, chamber margin heat flux, and is buffered by latent heat production. We use chemical and thermal calculations of MELTS (Ghiorso & Sack, 1995) as input to the physical model of QUANTUM (Dufek & Bachmann, 2010) to predict crystallinity windows of most probable magma extraction. We modeled two case studies: volcanism on Tenerife, Canary Islands, and the Campanian Ignimbrite (CI) of Campi Flegrei, Italy. Both preserve a basanitic to phonolitic lineage and have comparable total alkali concentrations; however, CI has high and Tenerife has low K2O/Na2O. Modeled thermal histories of differentiation for the two sequences contrast strongly. In Tenerife, the rate of latent heat production is almost always greater than sensible heat production, with spikes in the ratio of latent to sensible heats of up to 40 associated with the appearance of Fe-Ti oxides at near 50% crystallization. This punctuated heat production must cause magma temperature change to stall or slow in time. The extended time spent at ≈50% crystallinity, associated with dynamical processes that enhance melt extraction near 50% crystallinity, suggests the magma composition at this interval should be common. In Tenerife, the modeled composition coincides with that of the first peak in the bimodal frequency-composition distribution. In our

  4. Modeling Magma Mixing: Evidence from U-series age dating and Numerical Simulations

    Science.gov (United States)

    Philipp, R.; Cooper, K. M.; Bergantz, G. W.

    2007-12-01

    Magma mixing and recharge is an ubiquitous process in the shallow crust, which can trigger eruption and cause magma hybridization. Phenocrysts in mixed magmas are recorders for magma mixing and can be studied by in- situ techniques and analyses of bulk mineral separates. To better understand if micro-textural and compositional information reflects local or reservoir-scale events, a physical model for gathering and dispersal of crystals is necessary. We present the results of a combined geochemical and fluid dynamical study of magma mixing processes at Volcan Quizapu, Chile; two large (1846/47 AD and 1932 AD) dacitic eruptions from the same vent area were triggered by andesitic recharge magma and show various degrees of magma mixing. Employing a multiphase numerical fluid dynamic model, we simulated a simple mixing process of vesiculated mafic magma intruded into a crystal-bearing silicic reservoir. This unstable condition leads to overturn and mixing. In a second step we use the velocity field obtained to calculate the flow path of 5000 crystals randomly distributed over the entire system. Those particles mimic the phenocryst response to the convective motion. There is little local relative motion between silicate liquid and crystals due to the high viscosity of the melts and the rapid overturn rate of the system. Of special interest is the crystal dispersal and gathering, which is quantified by comparing the distance at the beginning and end of the simulation for all particle pairs that are initially closer than a length scale chosen between 1 and 10 m. At the start of the simulation, both the resident and new intruding (mafic) magmas have a unique particle population. Depending on the Reynolds number (Re) and the chosen characteristic length scale of different phenocryst-pairs, we statistically describe the heterogeneity of crystal populations on the thin section scale. For large Re (approx. 25) and a short characteristic length scale of particle

  5. The parent magma of the nakhlite meteorites - Clues from melt inclusions

    Science.gov (United States)

    Harvey, Ralph P.; Mcsween, Harry Y., Jr.

    1992-01-01

    Several forms of trapped liquid found within nakhlite meteorites have been examined, including interstitial melt and magmatic inclusions within the cores of large olivine grains. Differences in the mineralogy and texture between two types of trapped melt inclusions, and between these inclusions and the mesostasis, indicate that vitrophyric inclusions are most appropriate for estimating the composition of a nakhlite parental magma in equilibrium with early-forming olivine and augite. Parent liquids were calculated from the mineralogy of large inclusions in Nakhla and Governador Valadares, using a system of mass-balance equations solved by linear regression methods. The chosen parental liquids were cosaturated in olivine and augite and had Mg/Fe values consistent with measured augite/liquid Kds. These parental magma compositions are similar to other published compositions for Nakhla, Chassigny, and Shergotty parental melts, and may correspond to a significant magma type on Mars.

  6. Rapid cooling and cold storage in a silicic magma reservoir recorded in individual crystals.

    Science.gov (United States)

    Rubin, Allison E; Cooper, Kari M; Till, Christy B; Kent, Adam J R; Costa, Fidel; Bose, Maitrayee; Gravley, Darren; Deering, Chad; Cole, Jim

    2017-06-16

    Silicic volcanic eruptions pose considerable hazards, yet the processes leading to these eruptions remain poorly known. A missing link is knowledge of the thermal history of magma feeding such eruptions, which largely controls crystallinity and therefore eruptability. We have determined the thermal history of individual zircon crystals from an eruption of the Taupo Volcanic Zone, New Zealand. Results show that although zircons resided in the magmatic system for 10 3 to 10 5 years, they experienced temperatures >650° to 750°C for only years to centuries. This implies near-solidus long-term crystal storage, punctuated by rapid heating and cooling. Reconciling these data with existing models of magma storage requires considering multiple small intrusions and multiple spatial scales, and our approach can help to quantify heat input to and output from magma reservoirs. Copyright © 2017, American Association for the Advancement of Science.

  7. Asymmetric shock heating and the terrestrial magma ocean origin of the Moon.

    Science.gov (United States)

    Karato, Shun-ichiro

    2014-01-01

    One of the difficulties of the current giant impact model for the origin of the Moon is to explain the marked similarity in the isotopic compositions and the substantial differences in the major element chemistry. Physics of shock heating is analyzed to show that the degree of heating is asymmetric between the impactor and the target, if the target (the proto-Earth) had a magma-ocean but the impactor did not. The magma ocean is heated much more than the solid impactor and the vapor-rich jets come mainly from the magma-ocean from which the Moon might have been formed. In this scenario, the similarity and differences in the composition between the Moon and Earth would be explained as a natural consequence of a collision in the later stage of planetary formation. Including the asymmetry in shock heating is the first step toward explaining the chemical composition of the Moon.

  8. Chaotic behavior of earthquakes induced by a nonlinear magma up flow

    International Nuclear Information System (INIS)

    Pelap, F.B.; Kagho, L.Y.; Fogang, C.F.

    2016-01-01

    This paper considers the dynamics of a modified 1D nonlinear spring-block model for earthquake subjected to the strengths induced by the motion of the tectonic plates and the up flow of magma during volcanism. Based on the multiple time scales method, we establish that after the slip, the fault remains active and the frictions increase with the power of the earthquake. We also obtain in the non-resonance case that the appearing probability of an event decreases with these frictions. In the resonance case, the dynamics of harmonic oscillations show that the rocks constituting the block will fracture or resist to the effects induced by the magma motion. Our analytical investigations are complemented by numerical simulations from which it appears that, for given values of the magma thrust strength magnitude, the friction coefficient, the quadratic and cubic nonlinear parameters, the system exhibits chaotic behavior.

  9. Contraction or expansion of the Moon's crust during magma ocean freezing?

    Science.gov (United States)

    Elkins-Tanton, Linda T; Bercovici, David

    2014-09-13

    The lack of contraction features on the Moon has been used to argue that the Moon underwent limited secular cooling, and thus had a relatively cool initial state. A cool early state in turn limits the depth of the lunar magma ocean. Recent GRAIL gravity measurements, however, suggest that dikes were emplaced in the lower crust, requiring global lunar expansion. Starting from the magma ocean state, we show that solidification of the lunar magma ocean would most likely result in expansion of the young lunar crust, and that viscous relaxation of the crust would prevent early tectonic features of contraction or expansion from being recorded permanently. The most likely process for creating the expansion recorded by the dikes is melting during cumulate overturn of the newly solidified lunar mantle. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  10. [The spectrum studies of structure characteristics in magma contact metamorphic coal].

    Science.gov (United States)

    Wu, Dun; Sun, Ruo-Yu; Liu, Gui-Jian; Yuan, Zi-Jiao

    2013-10-01

    The structural parameters evolution of coal due to the influence of intrusions of hot magma was investigated and analyzed. X-ray diffraction and laser confocal microscope Raman spectroscopy were used to test and analyze 4 coal samples undergoing varying contact-metamorphism by igneous magmas in borehole No. 13-4 of Zhuji coal mine, Huainan coalfield. The result showed that coal XRD spectrum showed higher background intensity, with the 26 degrees and 42 degrees nearby apparent graphite diffraction peak. Two significant vibration peaks of coal Raman spectra were observed in the 1 000-2 000 cm(-1) frequency range: broad "D" peak at 1 328-1 369 cm(-1) and sharp "G" peak at 1 564-1 599 cm(-1). With the influence of magma intrusion, the relationship between coal structural parameters and coal ranks was excellent.

  11. Magmas near the critical degassing pressure drive volcanic unrest towards a critical state

    Science.gov (United States)

    Chiodini, Giovanni; Paonita, Antonio; Aiuppa, Alessandro; Costa, Antonio; Caliro, Stefano; De Martino, Prospero; Acocella, Valerio; Vandemeulebrouck, Jean

    2016-01-01

    During the reawaking of a volcano, magmas migrating through the shallow crust have to pass through hydrothermal fluids and rocks. The resulting magma–hydrothermal interactions are still poorly understood, which impairs the ability to interpret volcano monitoring signals and perform hazard assessments. Here we use the results of physical and volatile saturation models to demonstrate that magmatic volatiles released by decompressing magmas at a critical degassing pressure (CDP) can drive volcanic unrest towards a critical state. We show that, at the CDP, the abrupt and voluminous release of H2O-rich magmatic gases can heat hydrothermal fluids and rocks, triggering an accelerating deformation that can ultimately culminate in rock failure and eruption. We propose that magma could be approaching the CDP at Campi Flegrei, a volcano in the metropolitan area of Naples, one of the most densely inhabited areas in the world, and where accelerating deformation and heating are currently being observed. PMID:27996976

  12. Influences of magma chamber ellipticity on ring fracturing and eruption at collapse calderas

    Energy Technology Data Exchange (ETDEWEB)

    Holohan, Eoghan P; Walsh, John J [Fault Analysis Group, School of Geological Sciences, University College Dublin, Belfield, Dublin 4 (Ireland); Vries, Benjamin van Wyk de [Laboratoire Magmas et Volcans, 5 rue Kessler, 63038 Clermont-Ferrand (France); Troll, Valentin R [Department of Earth Sciences, Uppsala University, SE-752 36, Uppsala (Sweden); Walter, Thomas R [GFZ Potsdam, Telegrafenberg, Potsdam, D-14473 (Germany)], E-mail: Eoghan.Holohan@ucd.ie

    2008-10-01

    Plan-view ellipticity of a pre-caldera magma reservoir, and its influence on the development of caldera ring fracturing and eruptive behaviour, have not previously been subjected to dedicated evaluation. We experimentally simulated caldera collapse into elliptical magma chambers and found that collapse into highly-elliptical chambers produced a characteristic pattern of ring-fault localization and lateral propagation. Although results are preliminary, the general deformation pattern for elliptical resurgence shows strong similarities to elliptical collapse. Ring faults accommodating uplift again initiate around the chamberos short axis and are reverse, but dip inward. Field and geophysical observations at several elliptical calderas of varying scale (e.g. Long Valley, Katmai, and Rabaul calderas) are consistent with a control from elliptical magma chamber geometry on ring fracturing and eruption, as predicted from our experiments.

  13. The Greek Crisis – How the 1980s created Greece of today

    OpenAIRE

    Lauridsen, Ida Møller

    2013-01-01

    The economic crisis of 2008 is often taken to be a very special event when it comes to Greece. The Greeks are being blamed for their overconsumption and Greece is often described as one of the epicenters of the financial crisis. That Greece alone should be able to shake the global economy seems to be an exaggeration with the regard to Greece’s relatively small contribution to the European economy. The explanation for the Greek debt should be sought not only internally, but as a combination be...

  14. Economic Growth and Defense Spending in Greece, Turkey and Cyprus: Evidence from Cointegrated Panel Analysis

    Directory of Open Access Journals (Sweden)

    Stylianou Tasos

    2012-06-01

    Full Text Available This paper investigates the nexus between economic growth and defense spending for three adjacent countries, namely Greece, Turkey and Cyprus. Greece and Cyprus, members-countries of European Union spend much more money than other member countries of EU relatively to their GDP. Turkey is in accession negotiations with EU and is among the top 15 countries with the highest military expenditure. These three countries are particularly interesting case studies because of their high military burdens and the bad relations between them (Greece and Cyprus opposite Turkey. The empirical analysis is based on panel data analysis of data over the period 1960 – 2006.

  15. Magmas in motion: Degassing in volcanic conduits and fabrics of pyroclastic density current

    Science.gov (United States)

    Burgisser, Alain

    Volcanoes are caused by the transport of magma batches from the Earth's crust to the surface. These magmas in motion undergo drastic changes of rheologic properties during their journey to the surface and this work explores how these changes affect volcanic eruptions. The first part of this study is devoted to the dynamic aspects of degassing and permeability in magmas with high pressure, high temperature experiments on natural volcanic rocks. Degassing is measured by the influence of decompression rate on the growth of the bubbles present in the magma while permeability is deduced from the temporal evolution of these bubbles. The parameterization of our results in a numerical model of volcanic conduit flow show that previous models based on equilibrium degassing overestimate the acceleration and the decompression rate of the magma. Assessing permeability effects derived form our results show that the transition between explosive and effusive eruptions is a strong function of the magma initial ascent rate. The second part of this work is a unification of two end-members of pyroclastic currents (highly concentrated pyroclastic flows and dilute, turbulent pyroclastic surges) using theoretical scaling arguments based on multiphase physics. Starting from the dynamics of the particle interactions with a fundamental eddy, we consider the full spectrum of eddies generated within a turbulent current. We demonstrate that the presence of particles with various sizes induces a density stratification of the current, leading to its segregation into a basal concentrated part overlain by a dilute cloud. To verify our predictions on the interactions of such a segregated pyroclastic current with its surroundings (hills and sea), we studied the products of the 2050 BP caldera-forming eruption of Okmok Volcano (Alaska). This field study allowed us to reconstruct the eruptive sequence and to validate the main aspects of our theoretical model, such as the superposition of a dense and

  16. Magma shearing and friction in the volcanic conduit: A crystal constraint

    Science.gov (United States)

    Wallace, P. A.; Kendrick, J. E.; Henton De Angelis, S.; Ashworth, J. D.; Coats, R.; Miwa, T.; Mariani, E.; Lavallée, Y.

    2017-12-01

    Magma shearing and friction processes in the shallow volcanic conduit are typical manifestations of strain localisation, which in turn can have an influential role on magma ascent dynamics. The thermal consequences of such events could drive the destabilisation of magma and thus dictate the style of activity at the surface. Shear heating and fault friction are prime candidates for the generation of significant quantities of heat. Here we use a combination of field and experimental evidence to investigate how crystals can act as sensitive recorders of both physical and chemical processes occurring in the shallow volcanic conduit. Spine extrusion during the closing of the 1991-95 eruption at Unzen volcano, Japan, provided the unique opportunity to investigate marginal shear zone formation, which preserves a relic of the deformation during magma ascent. Our results show that crystals can effectively act as a deformation marker during magma ascent through the viscous-brittle transition by accommodating strain in the form of crystal plasticity before fracturing (comminution). Electron backscatter diffraction (EBSD) reveals up to 40° lattice distortion of biotite phenocrysts in zones of high shear, with negligible plasticity further away. Plagioclase microlites display a systematic plastic response to an increase in shear intensity, as recorded by an increase in lattice distortion towards the spine margin of up to 9°. This localisation of strain within the shear zone is also accompanied by the destabilisation of hydrous mineral phases (i.e. amphibole), compaction of pores (23-13% Φ), glass devitrification and magnetic anomalies. The narrow zone of disequilibrium textures suggests the likely effect of a thermal input due to strain localisation being the contributing factor. These observations are complimented by high-temperature high-velocity rotary shear experiments which simulate the deformation evolution during shear. Hence, understanding these shallow volcanic

  17. Upward migration of Vesuvius magma chamber over the past 20,000 years.

    Science.gov (United States)

    Scaillet, B; Pichavant, M; Cioni, R

    2008-09-11

    Forecasting future eruptions of Vesuvius is an important challenge for volcanologists, as its reawakening could threaten the lives of 700,000 people living near the volcano. Critical to the evaluation of hazards associated with the next eruption is the estimation of the depth of the magma reservoir, one of the main parameters controlling magma properties and eruptive style. Petrological studies have indicated that during past activity, magma chambers were at depths between 3 and 16 km (refs 3-7). Geophysical surveys have imaged some levels of seismic attenuation, the shallowest of which lies at 8-9 km depth, and these have been tentatively interpreted as levels of preferential magma accumulation. By using experimental phase equilibria, carried out on material from four main explosive events at Vesuvius, we show here that the reservoirs that fed the eruptive activity migrated from 7-8 km to 3-4 km depth between the ad 79 (Pompeii) and ad 472 (Pollena) events. If data from the Pomici di Base event 18.5 kyr ago and the 1944 Vesuvius eruption are included, the total upward migration of the reservoir amounts to 9-11 km. The change of preferential magma ponding levels in the upper crust can be attributed to differences in the volatile content and buoyancy of ascending magmas, as well as to changes in local stress field following either caldera formation or volcano spreading. Reservoir migration, and the possible influence on feeding rates, should be integrated into the parameters used for defining expected eruptive scenarios at Vesuvius.

  18. High magma storage rates before the 1983 eruption of kilauea, hawaii

    Science.gov (United States)

    Cayol; Dieterich; Okamura; Miklius

    2000-06-30

    After a magnitude 7.2 earthquake in 1975 and before the start of the ongoing eruption in 1983, deformation of Kilauea volcano was the most rapid ever recorded. Three-dimensional numerical modeling shows that this deformation is consistent with the dilation of a dike within Kilauea's rift zones coupled with creep over a narrow area of a low-angle fault beneath the south flank. Magma supply is estimated to be 0.18 cubic kilometers per year, twice that of previous estimates. The 1983 eruption may be a direct consequence of the high rates of magma storage within the rift zone that followed the 1975 earthquake.

  19. Lithospheric magma dynamics beneath the El Hierro Volcano, Canary Islands: insights from fluid inclusions

    Science.gov (United States)

    Oglialoro, E.; Frezzotti, M. L.; Ferrando, S.; Tiraboschi, C.; Principe, C.; Groppelli, G.; Villa, I. M.

    2017-10-01

    At active volcanoes, petrological studies have been proven to be a reliable approach in defining the depth conditions of magma transport and storage in both the mantle and the crust. Based on fluid inclusion and mineral geothermobarometry in mantle xenoliths, we propose a model for the magma plumbing system of the Island of El Hierro (Canary Islands). The peridotites studied here were entrained in a lava flow exposed in the El Yulan Valley. These lavas are part of the rift volcanism that occurred on El Hierro at approximately 40-30 ka. The peridotites are spinel lherzolites, harzburgites, and dunites which equilibrated in the shallow mantle at pressures between 1.5 and 2 GPa and at temperatures between 800 and 950 °C (low-temperature peridotites; LT), as well as at higher equilibration temperatures of 900 to 1100 °C (high-temperature peridotites; HT). Microthermometry and Raman analyses of fluid inclusions reveal trapping of two distinct fluid phases: early type I metasomatic CO2-N2 fluids ( X N2 = 0.01-0.18; fluid density (d) = 1.19 g/cm3), coexisting with silicate-carbonate melts in LT peridotites, and late type II pure CO2 fluids in both LT (d = 1.11-1.00 and 0.75-0.65 g/cm3) and HT ( d = 1.04-1.11 and 0.75-0.65 g/cm3) peridotites. While type I fluids represent metasomatic phases in the deep oceanic lithosphere (at depths of 60-65 km) before the onset of magmatic activity, type II CO2 fluids testify to two fluid trapping episodes during the ascent of xenoliths in their host mafic magmas. Identification of magma accumulation zones through interpretation of type II CO2 fluid inclusions and mineral geothermobarometry indicate the presence of a vertically stacked system of interconnected small magma reservoirs in the shallow lithospheric mantle between a depth of 22 and 36 km (or 0.67 to 1 GPa). This magma accumulation region fed a short-lived magma storage region located in the lower oceanic crust at a depth of 10-12 km (or 0.26-0.34 GPa). Following our model

  20. Numerical linear algebra on emerging architectures: The PLASMA and MAGMA projects

    International Nuclear Information System (INIS)

    Agullo, Emmanuel; Demmel, Jim; Dongarra, Jack; Hadri, Bilel; Kurzak, Jakub; Langou, Julien; Ltaief, Hatem; Luszczek, Piotr; Tomov, Stanimire

    2009-01-01

    The emergence and continuing use of multi-core architectures and graphics processing units require changes in the existing software and sometimes even a redesign of the established algorithms in order to take advantage of now prevailing parallelism. Parallel Linear Algebra for Scalable Multi-core Architectures (PLASMA) and Matrix Algebra on GPU and Multics Architectures (MAGMA) are two projects that aims to achieve high performance and portability across a wide range of multi-core architectures and hybrid systems respectively. We present in this document a comparative study of PLASMA's performance against established linear algebra packages and some preliminary results of MAGMA on hybrid multi-core and GPU systems.

  1. Long term storage of explosively erupted magma at Nevado de Toluca volcano, Mexico

    Science.gov (United States)

    Arce, J. L.; Gardner, J.; Macias, J. L.

    2007-12-01

    Dacitic magmas production is common in subduction-related volcanoes, occurring in those with a long period of activity as a result of the magmatic evolution. However, in this evolution many factors (i.e. crystal fractionation, assimilation, magma mixing) can interact to produce dacites. Nevado de Toluca volcano (4,680 masl; 19°09'N; 99°45'W) Central Mexico has recorded a long period of time producing dacites explosively, at least during 42 ka of activity, involving several km3 of magma, with two important Plinian-type eruptions occurred at ~21.7 ka (Lower Toluca Pumice) and ~10.5 ka (Upper Toluca Pumice). Questions like, what was the mechanism responsible to produce voluminous dacitic magma and how the volatiles and pressure changed in the Nevado de Toluca system, remain without answers. Dacites from the Lower Toluca Pumice (LTP) contain plagioclase, amphibole, iron-titanium oxides, and minor resorbed biotite, set in a glassy-vesicular matrix and the Upper Toluca Pumice (UTP) dacites contain the same mineral phases plus orthopyroxene. Ilmenite- ulvospinel geothermometry yielded a temperature of ~860°C for the LTP dacite, a little hotter than the UTP (~ 840°C). Based on hydrothermal experiments data, amphibole is stable above 100 MPa under 900°C, while plagioclase crystallizes up to 250-100 MPa at temperatures of 850-900°C. Pyroxene occurs only at pressures of 200-100 MPa with its respective temperatures of 825-900°C. Water contents in the LTP magma (2-3.5 wt %) are similar to that calculated for the UTP magma (1.3-3.6 wt %). So, there are only small changes in temperature and pressure from ~21.7 ka to 10.5 ka. It is noteworthy that orthopyroxene is absent in the LTP, however reaction-rimmed biotite (probably xenocrystic) is commonly observed in all dacites. Hence, almost all dacitic magmas seem to be stored at relatively similar pressures, water contents, and temperatures. All of these data could suggest repetitive basic magma injections producing the

  2. How does the architecture of a fault system controls magma upward migration through the crust?

    Science.gov (United States)

    Iturrieta, P. C.; Cembrano, J. M.; Stanton-Yonge, A.; Hurtado, D.

    2017-12-01

    The orientation and relative disposition of adjacent faults locally disrupt the regional stress field, thus enhancing magma flow through previous or newly created favorable conduits. Moreover, the brittle-plastic transition (BPT), due to its stronger rheology, governs the average state of stress of shallower portions of the fault system. Furthermore, the BPT may coincide with the location of transient magma reservoirs, from which dikes can propagate upwards into the upper crust, shaping the inner structure of the volcanic arc. In this work, we examine the stress distribution in strike-slip duplexes with variable geometry, along with the critical fluid overpressure ratio (CFOP), which is the minimum value required for individual faults to fracture in tension. We also determine the stress state disruption of the fault system when a dike is emplaced, to answer open questions such as: what is the nature of favorable pathways for magma to migrate? what is the architecture influence on the feedback between fault system kinematics and magma injection? To this end, we present a 3D coupled hydro-mechanical finite element model of the continental lithosphere, where faults are represented as continuum volumes with an elastic-plastic rheology. Magma flow upon fracturing is modeled through non-linear Stoke's flow, coupling solid and fluid equilibrium. A non-linear sensitivity analysis is performed in function of tectonic, rheology and geometry inputs, to assess which are the first-order factors that governs the nature of dike emplacement. Results show that the CFOP is heterogeneously distributed in the fault system, and within individual fault segments. Minimum values are displayed near fault intersections, where local kinematics superimpose on regional tectonic loading. Furthermore, when magma is transported through a fault segment, the CFOP is now minimized in faults with non-favorable orientations. This suggests that these faults act as transient pathways for magma to

  3. Dendrochronological Investigations of Valonia Oak Trees in Western Greece

    Directory of Open Access Journals (Sweden)

    Andreas Papadopoulos

    2016-06-01

    Full Text Available Background and Purpose: Valonia oak (Quercus ithaburensis subsp. macrolepis (Kotschy Hedge & Yalt. is an east Mediterranean endemic, xerothermic and deciduous tree of particular interest in forestry. There has been a growing demand lately to include the species in reforestations in Greece which also increased the interest to investigate its response to climate change. The main purpose of this research is to study valonia oak from a dendrochronological – dendroclimatological point of view within its Mediterranean distribution range. Materials and Methods: Sampling took place in characteristic valonia oak stands where cross sections or tree-cores were taken from 40 trees. The cross sections and the tree-cores were prepared and cross-dated using standard dendrochronological methods and tree-ring widths were measured to the nearest 0.001 mm using the Windendro software program. The ARSTAN program was used to standardize the tree-ring data and to calculate dendrochronological statistical parameters. The inter-annual variability of tree-ring width and the radial growth trend were examined. Finally, tree-ring widths to climate relationships were calculated by orthogonal regression in combination with the bootstrap procedure using master residual chronology and monthly precipitation, temperature data and scPDSI drought index, from October of the n-1 year up to November of the n year. Results: The master chronology of valonia oak trees in Western Greece reaches 365 years, with an average ring width of 0.89 mm and with mean sensitivity being 0.21. The variation of the tree-ring widths indicates the influence of climate and human intervention in the past. Tree-ring to climate relationships show that valonia oak growth is positively affected by precipitations in January and March and by drought reduction during June and July. Conclusions: Valonia oak in Western Greece is a species of great interest for dendrochronological and dendroclimatological studies

  4. Deformation patterns, magma supply, and magma storage at Karymsky Volcanic Center, Kamchatka, Russia, 2000-2010, revealed by InSAR

    Science.gov (United States)

    Ji, Lingyun; Izbekov, Pavel; Senyukov, Sergey; Lu, Zhong

    2018-02-01

    Under a complex geological region influenced by the subduction of the Pacific plate, Kamchatka Peninsula is one of the most active volcanic arcs in the Pacific Rim. Due to logistical difficulty in instrumentation, shallow magma plumbing systems beneath some of the Kamchatkan volcanoes are poorly understood. InSAR offers a safe and quick method for monitoring volcanic deformation with a high spatial resolution. In this study, a group of satellite radar interferograms that span the time interval from 2000 to 2010 shows eruptive and non-eruptive deformation at Karymsky Volcanic Center (KVC), Kamchatka, Russia. All the interferograms provide details of the activity around the KVC during 2000-2010, as follows: (1) from 2000 to 2004, the Karymsky-AN (Akademia Nauk) area deflated and the MS (Maly Semyachik) area inflated, (2) from 2004 to 2006, the Karymsky-AN area deflated with ongoing eruption, while the MS area subsided without eruption, (3) from 2006 to 2008, as with 2000-2004, the Karymsky-AN area deflated and the MS area inflated, (4) from 2008 to 2010, the Karymsky-AN area inflated up to 3 cm, and the MS area subsided. Point source models suggest that two magma reservoirs provide a good fit to the observed deformation. One source is located beneath the area between Karymsky and AN at a depth of approximately 7.0 km, and the other one is situated beneath MS at a depth of around 5.8 km. Synchronous deformation patterns suggest that two magma systems are fed from the same deep magma source and connected by a fracture zone. The InSAR results are consistent with GPS ground deformation measurements, seismic data, and petrological constraints.

  5. On a classification of central Eruptions according to Gas Pressure of the Magma and Viscosity of the Lava

    NARCIS (Netherlands)

    Escher, B.G.

    1933-01-01

    In the above title the word magma is used to signify the solution plus the gas disolved in it under pressure and the word lava for the magma that has partially or entirety lost its content of gas. A clear differentiation of the types of eruptions is not easy, because the character of an eruption

  6. Direct evidence for the origin of low-18O silicic magmas: Quenched samples of a magma chamber's partially-fused granitoid walls, Crater Lake, Oregon

    International Nuclear Information System (INIS)

    Bacon, C.R.; Adami, L.H.; Lanphere, M.A.

    1989-01-01

    Partially fused granitoid blocks were ejected in the climactic eruption of Mount Mazama, which was accompanied by collapse of Crater Lake caldera. Quartz, plagioclase, and glass in the granitoids have much lower δ 18 O values (-3.4 to +4.9per mille) than any fresh lavas of Mount Mazama and the surrounding region (+5.8 to +7.0per mille). Oxygen isotope fractionation between phases in granitoids is consistent with equilibrium at T≥900deg C following subsolidus exchange with hydrothermal fluids of meteoric origin. Assimilation of ≅ 10-20% of material similar to these granitoids can account for the O and Sr isotopic compositions of lavas and juvenile pyroclasts derived from the climactic magma chamber, many of which have δ 18 O values ≅ 0.5per mille or more lower than comparable lavas of Mount Mazama. The O isotope data provide the only clear evidence for such assimilation because the mineralogy and chemical and radiogenic isotopic compositions of the granitoids (dominantly granodiorite) are similar to those of erupted juvenile magmas. The granitoid blocks from Crater Lake serve as direct evidence for the origin of 18 O depletion in large, shallow silicic magma bodies. (orig.)

  7. Ground surface deformation patterns, magma supply, and magma storage at Okmok volcano, Alaska, from InSAR analysis: 2. Coeruptive deflation, July-August 2008

    Science.gov (United States)

    Lu, Zhong; Dzurisin, Daniel

    2010-01-01

    A hydrovolcanic eruption near Cone D on the floor of Okmok caldera, Alaska, began on 12 July 2008 and continued until late August 2008. The eruption was preceded by inflation of a magma reservoir located beneath the center of the caldera and ∼3 km below sea level (bsl), which began immediately after Okmok's previous eruption in 1997. In this paper we use data from several radar satellites and advanced interferometric synthetic aperture radar (InSAR) techniques to produce a suite of 2008 coeruption deformation maps. Most of the surface deformation that occurred during the eruption is explained by deflation of a Mogi-type source located beneath the center of the caldera and 2–3 km bsl, i.e., essentially the same source that inflated prior to the eruption. During the eruption the reservoir deflated at a rate that decreased exponentially with time with a 1/e time constant of ∼13 days. We envision a sponge-like network of interconnected fractures and melt bodies that in aggregate constitute a complex magma storage zone beneath Okmok caldera. The rate at which the reservoir deflates during an eruption may be controlled by the diminishing pressure difference between the reservoir and surface. A similar mechanism might explain the tendency for reservoir inflation to slow as an eruption approaches until the pressure difference between a deep magma production zone and the reservoir is great enough to drive an intrusion or eruption along the caldera ring-fracture system.

  8. Nature of the magma storage system beneath the Damavand volcano (N. Iran): An integrated study

    Science.gov (United States)

    Eskandari, Amir; Amini, Sadraddin; De Rosa, Rosanna; Donato, Paola

    2018-02-01

    Damavand intraplate stratovolcano constructed upon a moderately thick crust (58-67 km) over the last 2 Ma. The erupted products are dominantly trachyandesite-trachyte (TT) lavas and pyroclasts, with minor mafic magmas including tephrite-basanite-trachybasalt and alkali olivine basalts emplaced as cinder cones at the base of the stratovolcano. The TT products are characterized by a mineral assemblage of clinopyroxene (diopside-augite), orthopyroxene (clinoenstatite), feldspar (An2-58, Ab6-69, Or2-56), high Ti phlogopite, F-apatite, Fesbnd Ti oxides, and minor amounts of olivine (Fo73-80), amphibole and zircon, whereas olivine (Fo78-88), high Mg# (80-89) diopside, feldspar, apatite and Fesbnd Ti oxide occur in the mafic magmas. The presence of hydrous and anhydrous minerals, normal zonings, mafic cumulates, and the composition of magmatic inclusions in the TT products suggest evolutionary processes in polybaric conditions. In the same way, disequilibrium textures - including orthopyroxene mantled with clinopyroxene, reaction rim of phlogopite and amphibole, the coexistence of olivine and orthopyroxene, reverse, oscillatory and complex zonings of pyroxene and feldspar crystals - suggest magmatic evolutions in open systems with a varying temperature, oxygen fugacity, water as well as pressure and, to a lesser extent, melt chemistry. Mineral assemblages are used to model the physicochemical conditions and assess default parameters for the thermodynamic simulation of crystallization using MELTS software to track the P-T-H2O-ƒO2 evolution of the magma plumbing system. Thermobarometry and MELTS models estimated the initial nucleation depth at 16-17 kb (56-60 km) for olivine (Fo89) and high Al diopside crystals occurring in the mafic primary magma; it then stopped and underwent fractionation between 8 and 10 kb (28-35 km), corresponding with Moho depth, and continued to differentiate in the lower crust, in agreement with the geophysical models. The mafic rocks were formed

  9. Karyomorphometric analysis of Fritillaria montana group in Greece

    Directory of Open Access Journals (Sweden)

    Sofia Samaropoulou

    2016-12-01

    Full Text Available Fritillaria Linnaeus, 1753 (Liliaceae is a genus of geophytes, represented in Greece by 29 taxa. Most of the Greek species are endemic to the country and/or threatened. Although their classical cytotaxonomic studies have already been presented, no karyomorphometric analysis has ever been given. In the present study, the cytological results of Fritillaria montana Hoppe ex W.D.J. Koch, 1832 group, which includes F. epirotica Turrill ex Rix, 1975 and F. montana are statistically evaluated for the first time. Further indices about interchromosomal and intrachromosomal asymmetry are given. A new population of F. epirotica is also investigated, while for F. montana, a diploid individual was found in a known as triploid population. Paired t-tests and PCoA analysis have been applied to compare the two species.

  10. Karyomorphometric analysis of Fritillaria montana group in Greece.

    Science.gov (United States)

    Samaropoulou, Sofia; Bareka, Pepy; Kamari, Georgia

    2016-01-01

    Fritillaria Linnaeus, 1753 (Liliaceae) is a genus of geophytes, represented in Greece by 29 taxa. Most of the Greek species are endemic to the country and/or threatened. Although their classical cytotaxonomic studies have already been presented, no karyomorphometric analysis has ever been given. In the present study, the cytological results of Fritillaria montana Hoppe ex W.D.J. Koch, 1832 group, which includes Fritillaria epirotica Turrill ex Rix, 1975 and Fritillaria montana are statistically evaluated for the first time. Further indices about interchromosomal and intrachromosomal asymmetry are given. A new population of Fritillaria epirotica is also investigated, while for Fritillaria montana , a diploid individual was found in a known as triploid population. Paired t-tests and PCoA analysis have been applied to compare the two species.

  11. Disobedience and driving in patients with epilepsy in Greece.

    Science.gov (United States)

    Zis, Panagiotis; Siatouni, Anna; Kimiskidis, Vassilios K; Verentzioti, Anastasia; Kefalonitis, Georgios; Triantafyllou, Nikolaos; Gatzonis, Stylianos

    2014-12-01

    Regulations and guidelines regarding driving privileges of patients with epilepsy vary greatly worldwide. The aim of our study was twofold: firstly, to evaluate disobedient drivers in Greece and to elucidate their awareness of the law, emotional responses, and seizure profile and, secondly, to identify determinants of disobedience regarding driving among patients with epilepsy. All consecutive patients with epilepsy who visited the epilepsy outpatient clinic of two tertiary epilepsy centers were invited to participate in the study. One hundred ninety patients met our inclusion criteria. Fifty-two percent of our study population was aware of the driving restrictions. More than one out of three patients were disobedient (35.8%). Being a male was associated with a 6.07-fold increase in the odds of being disobedient (95% CI: 2.73-13.47, p important determinants of disobedience regarding driving among patients with epilepsy. Copyright © 2014 Elsevier Inc. All rights reserved.

  12. Carbonatitic dykes during Pangaea transtension (Pelagonian Zone, Greece)

    Science.gov (United States)

    Schenker, Filippo Luca; Burg, Jean-Pierre; Kostopoulos, Dimitrios; Baumgartner, Lukas P.; Bouvier, Anne-Sophie

    2018-03-01

    Carbonatitic dykes surrounded by K-Na-fenites were discovered in the Pelagonian Zone in Greece. Their carbonate portions have an isotopic mantle signature of δ13C and δ18O ranging from -5.18 to -5.56 (‰ vs. VPDB) and from 10.68 to 11.59 (‰ vs. VSMOW) respectively, whereas their mafic silicate portions have high Nb, Ta and ɛNd values, typical of alkaline basalts. Textural relationships hint at a cogenetic intrusion of silicate and carbonate liquids that according to antithetic REE profiles segregated at shallow depths (Pangaea dextral transform fault that signalled the forthcoming penetrating breakoff of the supercontinent, manifested in the Permo-Triassic.

  13. Spatial and temporal analysis of dry spells in Greece

    Science.gov (United States)

    Anagnostopoulou, Chr.; Maheras, P.; Karacostas, T.; Vafiadis, M.

    A spatio-temporal analysis of the dry spells that occur in the Greek area is carried out for an extended period of 40 years (1958-1997). The dry spells can be defined as a number of consecutive days with no rain. The number of days defines the length of the dry spells. The longest spells are identified in central (Cyclades) and the south-east Aegean Sea whereas dry spells with the minimum length are shown over the north-west of the Greek area that reflects the significance of the latitude and the topography. Negative Binomial Distribution and Markov Chains of second order have been used to fit the duration of the dry spells of different lengths. The study of the seasonal and annual distribution of the frequency of occurrence of dry spells revealed that the dry spells in Greece depict a seasonal character, while medium and long sequences are associated with the duration and hazards of drought.

  14. Long survival in a 69,XXX triploid infant in Greece.

    Science.gov (United States)

    Iliopoulos, Dimitrios; Vassiliou, Georgia; Sekerli, Eleni; Sidiropoulou, Vasiliki; Tsiga, Alexandra; Dimopoulou, Despina; Voyiatzis, Nikolaos

    2005-12-30

    The live birth of a triploidy infant is a very rare event and death usually occurs within the first hours of life. Triploid cases with a survival of more than two months are infrequent. We report on an infant with a 69,XXX chromosome constitution who survived 164 days. Chromosomal analysis demonstrated a 69,XXX karyotype with no evidence of mosaicism. This is the longest survival reported for this condition to date in Greece and the fourth longest worldwide. The infant was admitted to our clinic several times due to respiratory problems, and supplementary oxygen was required. The improved survival of our case was possibly due to better management of respiratory illness and prematurity, and these are essential factors that physicians should consider carefully with such rare cases.

  15. A Fiducial Reference Stie for Satellite Altimetry in Crete, Greece

    Science.gov (United States)

    Mertikas, Stelios; Donlon, Craig; Mavrocordatos, Constantin; Bojkov, Bojan; Femenias, Pierre; Parrinello, Tommaso; Picot, Nicolas; Desjonqueres, Jean-Damien; Andersen, Ole Baltazar

    2016-08-01

    With the advent of diverse satellite altimeters and variant measuring techniques, it has become mature in the scientific community, that an absolute reference Cal/Val site is regularly maintained to define, monitor, control the responses of any altimetric system.This work sets the ground for the establishment of a Fiducial Reference Site for ESA satellite altimetry in Gavdos and West Crete, Greece. It will consistently and reliably determine (a) absolute altimeter biases and their drifts; (b) relative bias among diverse missions; but also (c) continuously and independently connect different missions, on a common and reliable reference and also to SI-traceable measurements. Results from this fiducial reference site will be based on historic Cal/Val site measurement records, and will be the yardstick for building up capacity for monitoring climate change. This will be achieved by defining and assessing any satellite altimeter measurements to known, controlled and absolute reference signals with different techniques, processes and instrumentation.

  16. Evaluation of the socialist health policy in Greece.

    Science.gov (United States)

    Tsalikis, G

    1988-01-01

    Following seven years of military rule and seven years of "democratic restoration" under the Right, Greece is now sailing under the flag of the Panhellenic Socialist Movement (PASOK). The Movement was inspired by the ideals of participatory democracy and socialization of the economy and of social services. A central part of socialist planning brought about the National Health System Act (1983) and related legislation intended to universalize health care, remove disparities, and restrict the private sector. It is argued here that the implementation of PASOK's statutory reforms in this field, as in others, will be subject to its ability to transform traditional patterns of production and consumption. As is now increasingly understood, it is hard to plan for socialism on the basis of wants provisions and patterns of consumption established under capitalism.

  17. First results on video meteors from Crete, Greece

    Science.gov (United States)

    Maravelias, G.

    2012-01-01

    This work presents the first systematic video meteor observations from a, forthcoming permanent, station in Crete, Greece, operating as the first official node within the International Meteor Organization's Video Network. It consists of a Watec 902 H2 Ultimate camera equipped with a Panasonic WV-LA1208 (focal length 12mm, f/0.8) lens running MetRec. The system operated for 42 nights during 2011 (August 19-December 30, 2011) recording 1905 meteors. It is significantly more performant than a previous system used by the author during the Perseids 2010 (DMK camera 21AF04.AS by The Imaging Source, CCTV lens of focal length 2.8 mm, UFO Capture v2.22), which operated for 17 nights (August 4-22, 2010) recording 32 meteors. Differences - according to the author's experience - between the two softwares (MetRec, UFO Capture) are discussed along with a small guide to video meteor hardware.

  18. Education and training on nuclear security in Greece

    International Nuclear Information System (INIS)

    Pafilis, C. N.; Kamenopoulou, V.; Maltezos, A.; Seferlis, S.; Dimitriou, P.; Matikas, T. E.

    2009-01-01

    The Greek Atomic Energy Commission is the competent authority responsible for designing, implementing and supervising the radiation protection programme in Greece. According to its statutory law one of its main responsibilities is the provision of education and training to people involved in the national emergency response plan against nuclear and radiological threats. Due to the high requirements demanded for the safe conduct of the Athens 2004 Olympic Games, a nuclear security programme was established and the nuclear security infrastructure of the country was upgraded. Under this framework, GAEC provided training on radiation protection, prevention, detection, emergency preparedness and response to the personnel involved in the emergency plan. Since that time, the GAEC continues to organize seminars frequently addressed to the organizations involved in the emergency plan, in order to establish the sustainability of national operational capability on preparedness and response. (authors)

  19. Uranium exploration in Central and Eastern Macedonia and Thrace (Greece)

    International Nuclear Information System (INIS)

    Kampanellos, John; Persianis, Demetrios.

    1986-02-01

    In accordance with the Greek AEC Project for Uranium Exploration in Central and Eastern Macedonia and Thrace (Greece) car-borne scintillometer, ground scintillometer and geochemical stream sediment surveys along with reconnaissance geological mapping have been carried out within the area of map sheets 2523-2522 (Alexandroupolis-Aesymi, Evros Dept., Thrace). The results of these surveys, presented in a series of 15 maps, indicate that five areas totalling 632 km 2 require further detailed examination in order to test their potential of economic uranium deposits. Of these areas Nea Santa-Kechros-Chloi-Goniko-Kallithea-Leptokarya, Kirki-Kizari-Aesymi and Drosia-Fillyra-Darmeni should be given first priority and be further investigated by detailed stream sediment and bank soil sampling, detailed ground scintillometer measurements, grid soil and radon soil gas samplings, as well as by detailed geological mapping. (author)

  20. Uranium exploration in Central and Eastern Macedonia and Thrace (Greece)

    International Nuclear Information System (INIS)

    Kampanellos, John; Persianis, Demetrios.

    1985-01-01

    In accordance with the Greek AEC Project for Uranium Exploration in Central and Eastern Macedonia and Thrace (Greece) car-borne scintillometer, ground scintillometer and geochemical stream sediment surveys along with reconnaissance geological mapping have been carried out within the area of map sheets 2623(II,III)-2622 (Feres-Lefkimmi, Evros Dept., Thrace). The results of these surveys, presented in a series of 15 maps, indicate that three areas totalling 380 km 2 require further detailed examination in order to test their potential of economic uranium deposits. Of these areas Kotronia and Dadia-Nipsa-Loutros covering 325 km 2 should be given first priority and be further investigated by detailed stream sediment and bank soil sampling, detailed ground scintillometer measurements, grid soil and radon soil gas samplings, as well as by detailed geological mapping. (author)