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Sample records for tectonics ii plates

  1. The Plate Tectonics Project

    Science.gov (United States)

    Hein, Annamae J.

    2011-01-01

    The Plate Tectonics Project is a multiday, inquiry-based unit that facilitates students as self-motivated learners. Reliable Web sites are offered to assist with lessons, and a summative rubric is used to facilitate the holistic nature of the project. After each topic (parts of the Earth, continental drift, etc.) is covered, the students will…

  2. Indonesian Landforms and Plate Tectonics

    Directory of Open Access Journals (Sweden)

    Herman Th. Verstappen

    2014-06-01

    Full Text Available DOI: 10.17014/ijog.v5i3.103The horizontal configuration and vertical dimension of the landforms occurring in the tectonically unstable parts of Indonesia were resulted in the first place from plate tectonics. Most of them date from the Quaternary and endogenous forces are ongoing. Three major plates – the northward moving Indo-Australian Plate, the south-eastward moving SE-Asian Plate and the westward moving Pacific Plate - meet at a plate triple-junction situated in the south of New Guinea’s Bird’s Head. The narrow North-Moluccan plate is interposed between the Asia and Pacific. It tapers out northward in the Philippine Mobile Belt and is gradually disappearing. The greatest relief amplitudes occur near the plate boundaries: deep ocean trenches are associated with subduction zones and mountain ranges with collision belts. The landforms of the more stable areas of the plates date back to a more remote past and, where emerged, have a more subdued relief that is in the first place related to the resistance of the rocks to humid tropical weathering Rising mountain ranges and emerging island arcs are subjected to rapid humid-tropical river erosions and mass movements. The erosion products accumulate in adjacent sedimentary basins where their increasing weight causes subsidence by gravity and isostatic compensations. Living and raised coral reefs, volcanoes, and fault scarps are important geomorphic indicators of active plate tectonics. Compartmental faults may strongly affect island arcs stretching perpendicular to the plate movement. This is the case on Java. Transcurrent faults and related pull-apart basins are a leading factor where plates meet at an angle, such as on Sumatra. The most complicated situation exists near the triple-junction and in the Moluccas. Modern research methods, such as GPS measurements of plate movements and absolute dating of volcanic outbursts and raised coral reefs are important tools. The mega-landforms resulting

  3. Plate Tectonic Cycle. K-6 Science Curriculum.

    Science.gov (United States)

    Blueford, J. R.; And Others

    Plate Tectonics Cycle is one of the units of a K-6 unified science curriculum program. The unit consists of four organizing sub-themes: (1) volcanoes (covering formation, distribution, and major volcanic groups); (2) earthquakes (with investigations on wave movements, seismograms and sub-suface earth currents); (3) plate tectonics (providing maps…

  4. Earth's Decelerating Tectonic Plates

    Energy Technology Data Exchange (ETDEWEB)

    Forte, A M; Moucha, R; Rowley, D B; Quere, S; Mitrovica, J X; Simmons, N A; Grand, S P

    2008-08-22

    Space geodetic and oceanic magnetic anomaly constraints on tectonic plate motions are employed to determine a new global map of present-day rates of change of plate velocities. This map shows that Earth's largest plate, the Pacific, is presently decelerating along with several other plates in the Pacific and Indo-Atlantic hemispheres. These plate decelerations contribute to an overall, globally averaged slowdown in tectonic plate speeds. The map of plate decelerations provides new and unique constraints on the dynamics of time-dependent convection in Earth's mantle. We employ a recently developed convection model constrained by seismic, geodynamic and mineral physics data to show that time-dependent changes in mantle buoyancy forces can explain the deceleration of the major plates in the Pacific and Indo-Atlantic hemispheres.

  5. Reducing risk where tectonic plates collide

    Science.gov (United States)

    Gomberg, Joan S.; Ludwig, Kristin A.

    2017-06-19

    Most of the world’s earthquakes, tsunamis, landslides, and volcanic eruptions are caused by the continuous motions of the many tectonic plates that make up the Earth’s outer shell. The most powerful of these natural hazards occur in subduction zones, where two plates collide and one is thrust beneath another. The U.S. Geological Survey’s (USGS) “Reducing Risk Where Tectonic Plates Collide—A USGS Plan to Advance Subduction Zone Science” is a blueprint for building the crucial scientific foundation needed to inform the policies and practices that can make our Nation more resilient to subduction zone-related hazards.

  6. MACMA: a Virtual Lab for Plate Tectonics

    Science.gov (United States)

    Grigne, C.; Combes, M.; Tisseau, C.

    2013-12-01

    MACMA (Multi-Agent Convective MAntle) is a tool developed to simulate evolutive plate tectonics and mantle convection in a 2-D cylindrical geometry (Combes et al., 2012). The model relies mainly on a force balance to compute the velocity of each plate, and on empirical rules to determine how plate boundaries move and evolve. It includes first-order features of plate tectonics: (a) all plates on Earth do not have the same size, (b) subduction zones are asymmetric, (c) plates driven by subducting slabs and upper plates do not exhibit the same velocities, and (d) plate boundaries are mobile, can collide, merge and disappear, and new plate boundaries can be created. The MACMA interface was designed to be user-friendly and a simple use of the simulator can be achieved without any prerequisite knowledge in fluid dynamics, mantle rheology, nor in numerical methods. As a preliminary study, the simulator was used by a few students from bachelor's degree to master's degree levels. An initial configuration for plate tectonics has to be created before starting a simulation: the number and types of plate boundaries (ridge, subduction, passive margins) has to be defined and seafloor ages must be given. A simple but interesting exercise consists in letting students build such an initial configuration: they must analyze a map of tectonic plates, choose a 2-D section and examine carefully a map of seafloor ages. Students mentioned that the exercise made them realize that the 3-D spherical structure of plate tectonics does not translate directly in a simple 2-D section, as opposed to what is usually shown in books. Physical parameters: e.g. mantle viscosity, number of layers to consider in the mantle (upper and lower mantle, possible asthenosphere), initial time and mantle temperature, have to be chosen, and students can use this virtual lab to see how different scenarios emerge when parameters are varied. Very importantly, the direct visualization of the mobility of plate

  7. LOWLID FORMATION AND PLATE TECTONICS ON EXOPLANETS

    Science.gov (United States)

    Stamenkovic, V.; Noack, L.; Breuer, D.

    2009-12-01

    The last years of astronomical observation have opened the doors to a universe filled with extrasolar planets. Detection techniques still only offer the possibility to detect mainly Super-Earths above five Earth masses. But detection techniques do steadily improve and are offering the possibility to detect even smaller planets. The observations show that planets seem to exist in many possible sizes just as the planets and moons of our own solar system do. It is only a natural question to ask if planetary mass has an influence on some key habitability factors such as on plate tectonics, allowing us to test which exoplanets might be more likely habitable than others, and allowing us to understand if plate tectonics on Earth is a stable or a critical, instable process that could easily be perturbed. Here we present results derived from 1D parameterized thermal evolution and 2D/3D computer models, showing how planetary mass influences the propensity of plate tectonics for planets with masses ranging from 0.1 to 10 Earth masses. Lately [2, 3] studied the effect of planetary mass on the ability to break plates and hence initiate plate tectonics - but both derived results contradictory to the other. We think that one of the reasons why both studies [2, 3] are not acceptable in their current form is partly due to an oversimplification. Both treated viscosity only temperature-dependent but neglected the effect pressure has on enlarging the viscosity in the deep mantle. More massive planets have therefore a stronger pressure-viscosity-coupling making convection at high pressures sluggish or even impossible. For planets larger than two Earth masses we observe that a conductive lid (termed low-lid) forms above the core-mantle boundary and thus reduces the effective convective part of the mantle when including a pressure-dependent term into the viscosity laws as shown in [1]. Moreover [2, 3] use time independent steady state models neglecting the fact that plate tectonics is a

  8. From Plate Tectonic to Continental Dynamics

    Science.gov (United States)

    Molnar, P. H.

    2017-12-01

    By the early 1970s, the basics of plate tectonics were known. Although much understanding remained to be gained, as a topic of research, plate tectonics no longer defined the forefront of earth science. Not only had it become a foundation on which to build, but also the methods used to reveal it became tools to take in new directions. For me as a seismologist studying earthquakes and active processes, the deformation of continents offered an obvious topic to pursue. Obviously examining the deformation of continents and ignoring the widespread geologic evidence of both ongoing and finite deformation of crust would be stupid. I was blessed with the opportunity to learn from and collaborate with two of the best, Paul Tapponnier and Clark Burchfiel. Continental deformation differed from plate tectonics both because deformation was widespread but more importantly because crust shortens (extends) horizontally and thickens (thins), processes that can be ignored where plate tectonics - the relative motion of rigid plates - occurs. Where a plate boundary passes into a continent, not only must the forces that move plates do work against friction or other dissipative processes, but where high terrain is created, they must also do work against gravity, to create gravitational potential energy in high terrain. Peter Bird and Kenneth Piper and Philip England and Dan McKenzie showed that a two-dimensional thin viscous sheet with vertically averaged properties enabled both sources of resistance to be included without introducing excessive complexity and to be scaled by one dimensionless number, what the latter pair called the Argand number. Increasingly over the past thirty years, emphasis has shifted toward the role played by the mantle lithosphere, because of both its likely strength and its negative buoyancy, which makes it gravitationally unstable. Despite progress since realizing that rigid plates (the essence of plate tectonics) provides a poor description of continental

  9. Plate Tectonics and Continental Drift: Classroom Ideas.

    Science.gov (United States)

    Stout, Prentice K.

    1983-01-01

    Suggests various classroom studies related to plate tectonics and continental drift, including comments on and sources of resource materials useful in teaching the topics. A complete list of magazine articles on the topics from the Sawyer Marine Resource Collection may be obtained by contacting the author. (JN)

  10. Crustal thickness controlled by plate tectonics

    DEFF Research Database (Denmark)

    Artemieva, Irina M.; Meissner, Rolf

    2012-01-01

    /gabbro–eclogite phase transition in crustal evolution and the links between lithosphere recycling, mafic magmatism, and crustal underplating. We advocate that plate tectonics processes, togetherwith basalt/gabbro–eclogite transition, limit crustal thickness worldwide by providing effective mechanisms of crustal...

  11. Plate tectonics in the late Paleozoic

    Directory of Open Access Journals (Sweden)

    Mathew Domeier

    2014-05-01

    Full Text Available As the chronicle of plate motions through time, paleogeography is fundamental to our understanding of plate tectonics and its role in shaping the geology of the present-day. To properly appreciate the history of tectonics—and its influence on the deep Earth and climate—it is imperative to seek an accurate and global model of paleogeography. However, owing to the incessant loss of oceanic lithosphere through subduction, the paleogeographic reconstruction of ‘full-plates’ (including oceanic lithosphere becomes increasingly challenging with age. Prior to 150 Ma ∼60% of the lithosphere is missing and reconstructions are developed without explicit regard for oceanic lithosphere or plate tectonic principles; in effect, reflecting the earlier mobilistic paradigm of continental drift. Although these ‘continental’ reconstructions have been immensely useful, the next-generation of mantle models requires global plate kinematic descriptions with full-plate reconstructions. Moreover, in disregarding (or only loosely applying plate tectonic rules, continental reconstructions fail to take advantage of a wealth of additional information in the form of practical constraints. Following a series of new developments, both in geodynamic theory and analytical tools, it is now feasible to construct full-plate models that lend themselves to testing by the wider Earth-science community. Such a model is presented here for the late Paleozoic (410–250 Ma together with a review of the underlying data. Although we expect this model to be particularly useful for numerical mantle modeling, we hope that it will also serve as a general framework for understanding late Paleozoic tectonics, one on which future improvements can be built and further tested.

  12. Plate tectonics drive tropical reef biodiversity dynamics

    Science.gov (United States)

    Leprieur, Fabien; Descombes, Patrice; Gaboriau, Théo; Cowman, Peter F.; Parravicini, Valeriano; Kulbicki, Michel; Melián, Carlos J.; de Santana, Charles N.; Heine, Christian; Mouillot, David; Bellwood, David R.; Pellissier, Loïc

    2016-05-01

    The Cretaceous breakup of Gondwana strongly modified the global distribution of shallow tropical seas reshaping the geographic configuration of marine basins. However, the links between tropical reef availability, plate tectonic processes and marine biodiversity distribution patterns are still unknown. Here, we show that a spatial diversification model constrained by absolute plate motions for the past 140 million years predicts the emergence and movement of diversity hotspots on tropical reefs. The spatial dynamics of tropical reefs explains marine fauna diversification in the Tethyan Ocean during the Cretaceous and early Cenozoic, and identifies an eastward movement of ancestral marine lineages towards the Indo-Australian Archipelago in the Miocene. A mechanistic model based only on habitat-driven diversification and dispersal yields realistic predictions of current biodiversity patterns for both corals and fishes. As in terrestrial systems, we demonstrate that plate tectonics played a major role in driving tropical marine shallow reef biodiversity dynamics.

  13. Caribbean plate tectonics from seismic tomography

    Science.gov (United States)

    Ten Brink, U. S.; Villasenor, A.

    2012-12-01

    New seismic tomography in the Caribbean shows close links between the geometry and dynamics of subducting slabs and the geology of the overriding plate. Unlike most oceanic plates, the Caribbean plate lacks identifiable seafloor magnetic anomalies and fracture zones. The plate's history has therefore been inferred primarily from land geology along the plate boundary, which is complicated by large-scale shear deformation, and from finite rotations of surrounding plates.We used more than 14 million arrival times from 300,000 earthquakes to identify P-wave velocity anomalies. We relate the anomalies to the geometry and dynamics of subducting slabs and to patterns of earthquake activity, volcanism, topographic relief, and tectonic deformation. For example, we detect two separate slabs belonging to the North and South American plates, respectively, which appear to be responsible for morphologic and tectonic differences between the arcs of the Northern (from Guadeloupe northward) and Southern (from Dominica southward) Lesser Antilles. Variations in earthquake activity between Haiti and the Dominican Republic can be explained by a change in slab geometry from an underplated slab beneath Haiti to a subducting slab under the Dominican Republic. A shallow tear in the slab may explain the anomalously deep Puerto Rico Trench and the frequent earthquake swarms there. The westward shift in volcanic activity in the Northern Lesser Antilles from the Miocene Limestone Caribbees to the present arc can be attributed to the limit on convective flow imposed by the 3-D geometry of the slab at depth. A thinned South America slab under the southern Lesser Antilles may result from traction imposed on the slab by a wide forearc wedge. Variations in tectonic deformation of northern South America could be related to the location of the Caribbean Large Igneous Province north of the Maracaibo Block.

  14. Seismology: tectonic strain in plate interiors?

    Science.gov (United States)

    Calais, E; Mattioli, G; DeMets, C; Nocquet, J-M; Stein, S; Newman, A; Rydelek, P

    2005-12-15

    It is not fully understood how or why the inner areas of tectonic plates deform, leading to large, although infrequent, earthquakes. Smalley et al. offer a potential breakthrough by suggesting that surface deformation in the central United States accumulates at rates comparable to those across plate boundaries. However, we find no statistically significant deformation in three independent analyses of the data set used by Smalley et al., and conclude therefore that only the upper bounds of magnitude and repeat time for large earthquakes can be inferred at present.

  15. Organization of the tectonic plates in the last 200 Myr

    Science.gov (United States)

    Morra, Gabriele; Seton, Maria; Quevedo, Leonardo; Müller, R. Dietmar

    2013-07-01

    The present tessellation of the Earth's surface into tectonic plates displays a remarkably regular plate size distribution, described by either one (Sornette and Pisarenko, 2003) or two (Bird, 2003) statistically distinct groups, characterised by large and small plate size. A unique distribution implies a hierarchical structure from the largest to the smallest plate. Alternatively, two distributions indicate distinct evolutionary laws for large and small plates, the first tied to mantle flow, the second determined by a hierarchical fragmentation process. We analyse detailed reconstructions of plate boundaries during the last 200 Myr and find that (i) large and small plates display distinct statistical distributions, (ii) the small plates display little organisational change since 60 Ma and (iii) the large plates oscillate between heterogeneous (200-170 Myr and 65-50 Ma) and homogeneous (120-100 Ma) plate tessellations on a timescale of about 100 Myr. Heterogeneous states are reached more rapidly, while the plate configuration decays into homogeneous states following a slower asymptotic curve, suggesting that heterogeneous configurations are excited states while homogeneous tessellations are equilibrium states. We explain this evolution by proposing a model that alternates between bottom- and top-driven Earth dynamics, physically described by fluid-dynamic analogies, the Rayleigh-Benard and Bénard-Marangoni convection, respectively. We discuss the implications for true polar wander (TPW), global kinematic reorganisations (50 and 100 Ma) and the Earth's magnetic field inversion frequency.

  16. Is plate tectonics needed to evolve technological species on exoplanets?

    Directory of Open Access Journals (Sweden)

    Robert J. Stern

    2016-07-01

    Full Text Available As we continue searching for exoplanets, we wonder if life and technological species capable of communicating with us exists on any of them. As geoscientists, we can also wonder how important is the presence or absence of plate tectonics for the evolution of technological species. This essay considers this question, focusing on tectonically active rocky (silicate planets, like Earth, Venus, and Mars. The development of technological species on Earth provides key insights for understanding evolution on exoplanets, including the likely role that plate tectonics may play. An Earth-sized silicate planet is likely to experience several tectonic styles over its lifetime, as it cools and its lithosphere thickens, strengthens, and becomes denser. These include magma ocean, various styles of stagnant lid, and perhaps plate tectonics. Abundant liquid water favors both life and plate tectonics. Ocean is required for early evolution of diverse single-celled organisms, then colonies of cells which specialized further to form guts, appendages, and sensory organisms up to the complexity of fish (central nervous system, appendages, eyes. Large expanses of dry land also begin in the ocean, today produced above subduction zones in juvenile arcs and by their coalescence to form continents, although it is not clear that plate tectonics was required to create continental crust on Earth. Dry land of continents is required for further evolution of technological species, where modification of appendages for grasping and manipulating, and improvement of eyes and central nervous system could be perfected. These bioassets allowed intelligent creatures to examine the night sky and wonder, the beginning of abstract thinking, including religion and science. Technology arises from the exigencies of daily living such as tool-making, agriculture, clothing, and weapons, but the pace of innovation accelerates once it is allied with science. Finally, the importance of plate

  17. Plate tectonics and planetary habitability: current status and future challenges.

    Science.gov (United States)

    Korenaga, Jun

    2012-07-01

    Plate tectonics is one of the major factors affecting the potential habitability of a terrestrial planet. The physics of plate tectonics is, however, still far from being complete, leading to considerable uncertainty when discussing planetary habitability. Here, I summarize recent developments on the evolution of plate tectonics on Earth, which suggest a radically new view on Earth dynamics: convection in the mantle has been speeding up despite its secular cooling, and the operation of plate tectonics has been facilitated throughout Earth's history by the gradual subduction of water into an initially dry mantle. The role of plate tectonics in planetary habitability through its influence on atmospheric evolution is still difficult to quantify, and, to this end, it will be vital to better understand a coupled core-mantle-atmosphere system in the context of solar system evolution. © 2012 New York Academy of Sciences.

  18. Oil prospection using the tectonic plate model

    Science.gov (United States)

    Pointu, Agnès

    2015-04-01

    Tectonic plate models are an intellectual setting to understand why oil deposits are so uncommon and unequally distributed and how models can be used in actual oil and gas prospection. In this case, we use the example of the Ghawar deposit (Saudi Arabia), one of the largest producing well in the world. In the first step, physical properties of rocks composing the oil accumulation are studied by laboratory experiments. Students estimate the porosity of limestone and clay by comparing their mass before and after water impregnation. Results are compared to microscopic observations. Thus, students come to the conclusion that oil accumulations are characterized by superposition of rocks with very different properties: a rich organic source rock (clays of the Hanifa formation), a porous reservoir rock to store the petroleum in (limestones of the Arab formation) and above an impermeable rock with very low porosity (evaporites of the Tithonien). In previous lessons, students have seen that organic matter is usually mineralized by bacteria and that this preservation requires particular conditions. The aim is to explain why biomass production has been so important during the deposit of the clays of the Hanifa formation. Tectonic plate models make it possible to estimate the location of the Arabian Peninsula during Jurassic times (age of Hanifa formation). In order to understand why the paleo-location of the Arabian Peninsula is important to preserve organic matter, students have different documents showing: - That primary production of biomass by phytoplankton is favored by climatic conditions, - That the position of continents determinate the ocean currents and the positions of upwelling zones and zones where organic matter will be able to be preserved, - That north of the peninsula there was a passive margin during Jurassic times. An actual seismic line is studied in order to highlight that this extensive area allowed thick sedimentary deposits to accumulate and that fast

  19. Plate Tectonics and Planetary Evolution: Implications for Understanding Exoplanets

    Science.gov (United States)

    Elkins-Tanton, L. T.

    2015-12-01

    A primary purpose in our study of exoplanets is the search for life. In hypothesizing how we might detect life, we start by examining life on Earth; it is our only example. How do we understand the meaning of habitability when there is only one example? All clues seem significant: the common need for the existence of water, the range of temperatures over which life on Earth is found, and the chemical cycles that maintain the surface and near-surface of the Earth within that range. A common assertion is that plate tectonics is necessary for the carbon cycle that keeps the Earth at habitable temperatures by sequestering carbon in limetone in oceans, and parceling it back into the atmosphere through volcanoes. This is an unproven hypothesis. There are other tectonic processes that cycle carbon into a planetary interior and back to the atmosphere; one possibility is small-scale convection that returns lithospheric material to the mantle and produces small-scale volcanism. Whether this process is sufficient to stabilize climate on one-plate planets or planets with sluggish convection remains to be demonstrated. Before we can discuss the criticality of plate tectonics on other planets we need to understand its criticality on Earth, and its apparent lack on Venus. And before we can predict whether plate tectonics should exist on a given exoplanet, we need to understand why it exists on Earth, and apparently not on Venus, and we need to know more about that exoplanet than can currently be detected. In this talk I will compare the predictions for exoplanetary conditions conducive to plate tectonics, walk through possible pathways in planetary evolution that lead to plate tectonics, and discuss whether any aspect of plate tectonics on an exoplanet is detectable from Earth. Predicting and hoping to detect plate tectonics on exoplanets is walking out a shaky limb; making cautious incremental advances in understanding terrestrial plate tectonics is critical before extending

  20. Looking for Plate Tectonics in all the wrong fluids

    Science.gov (United States)

    Davaille, Anne

    2017-04-01

    Ever since the theory of Plate Tectonics in the 1960's, the dream of the geomodeler has been to generate plate tectonics self-consistently from thermal convection in the laboratory. By selfconsistenly, I mean that the configuration of the plate boundaries is in no way specified a priori, so that the plates develop and are wholly consumed without intervention from the modeler. The reciepe is simple : put a well-chosen fluid in a fishtank heated from below and cooled from above, wait and see. But the « well-chosen » is the difficult part... and the interesting one. Plate tectonics is occuring on Earth because of the characteristics of the lithosphere rheology. The latter are complex to estimate as they depend on temperature, pressure, phase, water content, chemistry, strain rate, memory and scale. As a result, the ingredients necessary for plate tectonics are still debated, and it would be useful to find an analog fluid who could reproduce plate tectonics in the laboratory. I have therefore spent the last 25 years to try out fluids, and I shall present a number of failures to generate plate tectonics using polymers, colloids, ketchup, milk, chocolate, sugar, oils. To understand why they failed is important to narrow down the « well-chosen » fluid.

  1. Structure and tectonics of convergent plate margins

    Czech Academy of Sciences Publication Activity Database

    Špičák, Aleš (ed.); Čadek, O. (ed.); Engdahl, E. R. (ed.)

    2004-01-01

    Roč. 141, č. 4 (2004), s. 241 ISSN 0031-9201 R&D Projects: GA AV ČR KSK3012103 Keywords : tectonics * subduction * convergent margins Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 2.370, year: 2004

  2. Scaling of plate tectonic convection with pseudoplastic rheology

    Science.gov (United States)

    Korenaga, Jun

    2010-11-01

    The scaling of plate tectonic convection is investigated by simulating thermal convection with pseudoplastic rheology and strongly temperature-dependent viscosity. The effect of mantle melting is also explored with additional depth-dependent viscosity. Heat flow scaling can be constructed with only two parameters, the internal Rayleigh number and the lithospheric viscosity contrast, the latter of which is determined entirely by rheological properties. The critical viscosity contrast for the transition between plate tectonic and stagnant lid convection is found to be proportional to the square root of the internal Rayleigh number. The relation between mantle temperature and surface heat flux on Earth is discussed on the basis of these scaling laws, and the inverse relationship between them, as previously suggested from the consideration of global energy balance, is confirmed by this fully dynamic approach. In the presence of surface water to reduce the effective friction coefficient, the operation of plate tectonics is suggested to be plausible throughout the Earth history.

  3. A planetary perspective on Earth evolution: Lid Tectonics before Plate Tectonics

    Science.gov (United States)

    Piper, John D. A.

    2013-03-01

    Plate Tectonics requires a specific range of thermal, fluid and compositional conditions before it will operate to mobilise planetary lithospheres. The response to interior heat dispersion ranges from mobile lids in constant motion able to generate zones of subduction and spreading (Plate Tectonics), through styles of Lid Tectonics expressed by stagnant lids punctured by volcanism, to lids alternating between static and mobile. The palaeomagnetic record through Earth history provides a test for tectonic style because a mobile Earth of multiple continents is recorded by diverse apparent polar wander paths, whilst Lid Tectonics is recorded by conformity to a single position. The former is difficult to isolate without extreme selection whereas the latter is a demanding requirement and easily recognised. In the event, the Precambrian palaeomagnetic database closely conforms to this latter property over very long periods of time (~ 2.7-2.2 Ga, 1.5-1.3 Ga and 0.75-0.6 Ga); intervening intervals are characterised by focussed loops compatible with episodes of true polar wander stimulated by disturbances to the planetary figure. Because of this singular property, the Precambrian palaeomagnetic record is highly effective in showing that a dominant Lid Tectonics operated throughout most of Earth history. A continental lid comprising at least 60% of the present continental area and volume had achieved quasi-integrity by 2.7 Ga. Reconfiguration of mantle and continental lid at ~ 2.2 Ga correlates with isotopic signatures and the Great Oxygenation Event and is the closest analogy in Earth history to the resurfacing of Venus. Change from Lid Tectonics to Plate Tectonics is transitional and the geological record identifies incipient development of Plate Tectonics on an orogenic scale especially after 1.1 Ga, but only following break-up of the continental lid (Palaeopangaea) in Ediacaran times beginning at ~ 0.6 Ga has it become comprehensive in the style evident during the

  4. Alfred Wegener-From Continental Drift to Plate Tectonics

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 10; Issue 6. Alfred Wegener – From Continental Drift to Plate Tectonics. A J Saigeetha Ravinder Kumar Banyal. General Article Volume 10 Issue 6 June 2005 pp 43-59. Fulltext. Click here to view fulltext PDF. Permanent link:

  5. Is Active Tectonics on Madagascar Consistent with Somalian Plate Kinematics?

    Science.gov (United States)

    Stamps, D. S.; Kreemer, C.; Rajaonarison, T. A.

    2017-12-01

    The East African Rift System (EARS) actively breaks apart the Nubian and Somalian tectonic plates. Madagascar finds itself at the easternmost boundary of the EARS, between the Rovuma block, Lwandle plate, and the Somalian plate. Earthquake focal mechanisms and N-S oriented fault structures on the continental island suggest that Madagascar is experiencing east-west oriented extension. However, some previous plate kinematic studies indicate minor compressional strains across Madagascar. This inconsistency may be due to uncertainties in Somalian plate rotation. Past estimates of the rotation of the Somalian plate suffered from a poor coverage of GPS stations, but some important new stations are now available for a re-evaluation. In this work, we revise the kinematics of the Somalian plate. We first calculate a new GPS velocity solution and perform block kinematic modeling to evaluate the Somalian plate rotation. We then estimate new Somalia-Rovuma and Somalia-Lwandle relative motions across Madagascar and evaluate whether they are consistent with GPS measurements made on the island itself, as well as with other kinematic indicators.

  6. Learning Plate Tectonics Using a Pre-Analogy Step

    Science.gov (United States)

    Glesener, G. B.; Sandoval, W. A.

    2011-12-01

    Previous research has shown that children tend to demonstrate lower performance on analogical reasoning tasks at a causal relations level compared to most adults (Gentner & Toupin, 1986). This tendency is an obstacle that geoscience educators must overcome because of the high frequency of analogies used in geoscience pedagogy. In particular, analog models are used to convey complex systems of non-everyday/non-observable events found in nature, such as plate tectonics. Key factors in successful analogical reasoning that have been suggested by researchers include knowledge of the causal relations in the base analog (Brown & Kane, 1988; Gentner, 1988; Gentner & Toupin, 1986), and development of learning strategies and metaconceptual competence(Brown & Kane, 1988). External factors, such as guiding cues and hints have been useful cognitive supports that help students reason through analogical problems (Gick & Holyoak, 1980). Cognitive supports have been seen by researchers to decrease processing demands on retrieval and working memory (Richland, Zur, & Holyoak, 2007). We observed third and fourth graders learning about plate tectonics beginning with a pre-analogy step-a cognitive support activity a student can do before working with an analogy to understand the target. This activity was designed to aid students in developing their understanding of object attributes and relations within an analog model so that more focus can be placed on mapping the corresponding higher-order relations between the base and target. Students learned targeted concepts of plate tectonics, as measured by pre to post gains on items adapted from the Geosciences Concept Inventory. Analyses of classroom interaction showed that students used the object attributes and higher-order relations highlighted in the pre-analogy activity as resources to reason about plate boundaries and plate movement during earthquakes.

  7. The San Andreas fault experiment. [gross tectonic plates relative velocity

    Science.gov (United States)

    Smith, D. E.; Vonbun, F. O.

    1973-01-01

    A plan was developed during 1971 to determine gross tectonic plate motions along the San Andreas Fault System in California. Knowledge of the gross motion along the total fault system is an essential component in the construction of realistic deformation models of fault regions. Such mathematical models will be used in the future for studies which will eventually lead to prediction of major earthquakes. The main purpose of the experiment described is the determination of the relative velocity of the North American and the Pacific Plates. This motion being so extremely small, cannot be measured directly but can be deduced from distance measurements between points on opposite sites of the plate boundary taken over a number of years.

  8. Ore-lead isotopes and Grenville plate tectonics

    International Nuclear Information System (INIS)

    Farquhar, R.M.; Fletcher, I.R.

    1980-01-01

    Recent advances in the 'whole earth' modelling of evolutionary processes of Pb isotopes shed light upon the origin of the metals found in various types of ore deposits. On the bases of these models and several recently published data sets, we believe that the ore deposits formed in various plate tectonic environments may carry 'isotopic fingerprints' which, when used with other characteristics such as mineral assemblages, may identify the depositional environments of many ore bodies. In the present study Pb-isotopic measurements have been made of a number of Precambrain mineralization types and localities throughout the Central Metasedimentary Belt of the Grenville Province. The data for individual deposits are at best ambiguous, but fall into two groups sufficiently distinctive to allow some degree of 'fingerprint' identification. Comparisons with data from other areas suggest that the major periods of sedimentation within the Central Metasedimentary Belt accompanied plate rifting and/or island arc tectonic activity, with most of the mineralized lead being derived from mantle sources. Detailed comparisons between the Grenville and other regions are uncertain, mainly because there are few detailed high-accuracy data sets from younger, tectonically unambiguous mineral occurrences. We suggest that once these data sets are availble, isotopic fingerprinting may become diagnostic for deposits ranging well back into the Precambrain

  9. Geophysical Limitations on the Habitable Zone: Volcanism and Plate Tectonics

    Science.gov (United States)

    Noack, Lena; Rivoldini, Attilio; Van Hoolst, Tim

    2016-04-01

    Planets are typically classified as potentially life-bearing planets (i.e. habitable planets) if they are rocky planets and if a liquid (e.g. water) could exist at the surface. The latter depends on several factors, like for example the amount of available solar energy, greenhouse effects in the atmosphere and an efficient CO2-cycle. However, the definition of the habitable zone should be updated to include possible geophysical constraints, that could potentially influence the CO2-cycle. Planets like Mars without plate tectonics and no or only limited volcanic events can only be considered to be habitable at the inner boundary of the habitable zone, since the greenhouse effect needed to ensure liquid surface water farther away from the sun is strongly reduced. We investigate if the planet mass as well as the interior structure can set constraints on the occurrence of plate tectonics and outgassing, and therefore affect the habitable zone, using both parameterized evolution models [1] and mantle convection simulations [1,2]. We find that plate tectonics, if it occurs, always leads to sufficient volcanic outgassing and therefore greenhouse effect needed for the outer boundary of the habitable zone (several tens of bar CO2), see also [3]. One-plate planets, however, may suffer strong volcanic limitations. The existence of a dense-enough CO2 atmosphere allowing for the carbon-silicate cycle and release of carbon at the outer boundary of the habitable zone may be strongly limited for planets: 1) without plate tectonics, 2) with a large planet mass, and/or 3) a high iron content. Acknowledgements This work has been funded by the Interuniversity Attraction Poles Programme initiated by the Belgian Science Policy Office through the Planet Topers alliance, and results within the collaboration of the COST Action TD 1308. References Noack, L., Rivoldini, A., and Van Hoolst, T.: CHIC - Coupling Habitability, Interior and Crust, INFOCOMP 2015, ISSN 2308-3484, ISBN 978

  10. Organization of the tectonic plates in the last 200 Myr (Invited)

    Science.gov (United States)

    Morra, G.; Seton, M.; Quevedo, L. E.; Müller, D.

    2013-12-01

    The present tessellation of the Earth's surface into tectonic plates displays a remarkably regular plate size distribution, described by either one (Sornette and Pisarenko, 2003) or two (Bird, 2003) statistically distinct groups, characterised by large and small plate size. A unique distribution implies a hierarchical structure from the largest to the smallest plate. Alternatively, two distributions indicate distinct evolutionary laws for large and small plates, the first tied to mantle flow, the second determined by a hierarchical fragmentation process. We analyse detailed reconstructions of plate boundaries during the last 200 Myr and find that (i) large and small plates display distinct statistical distributions, (ii) the small plates display little organisational change since 60 Ma and (iii) the large plates oscillate between heterogeneous (200-170 Ma and 65-50 Ma) and homogeneous (120-100 Ma) plate tessellations on a timescale of about 100 Myr. Heterogeneous states are reached more rapidly, while the plate configuration decays into homogeneous states following a slower asymptotic curve, suggesting that heterogeneous configurations are excited states while homogeneous tessellations are equilibrium states. We explain this evolution by proposing a model that alternates between bottom- and top-driven Earth dynamics, physically described by fluid-dynamic analogies, the Rayleigh-Benard and Bénard-Marangoni convection, respectively. We discuss the implications for true polar wander (TPW), global kinematic reorganisations (50 and 100 Ma) and the Earth's magnetic field inversion frequency. Earth's present tessellation: grey scale proportional to the logarithm of plate size. Plot: logarithm of complementary 'cumulative plate count' (Y-axis) vs. the logarithm of the plate size (X-axis). Time evolution of the 'standard deviation' of the plate size every one million years.

  11. The Biggest Plates on Earth. Submarine Ring of Fire--Grades 5-6. Plate Tectonics.

    Science.gov (United States)

    National Oceanic and Atmospheric Administration (DOC), Rockville, MD.

    This activity is designed to teach how tectonic plates move, what some consequences of this motion are, and how magnetic anomalies document the motion at spreading centers do. The activity provides learning objectives, a list of needed materials, key vocabulary words, background information, day-to-day procedures, internet connections, career…

  12. Modelling continental deformation within global plate tectonic reconstructions

    Science.gov (United States)

    Williams, S.; Whittaker, J.; Heine, C.; Müller, P.

    2010-12-01

    A limitation of regional and global plate tectonic models is the way continental deformation is represented. Continental blocks are typically represented as rigid polygons - overlaps or gaps between adjacent continental blocks represent extension or compression respectively. Full-fit reconstructions of major ocean basins result in large overlaps between the conjugate continental plates, on the basis that the continental margins are highly extended compared to their pre-rift state. A fundamental challenge in generating more robust global-scale plate reconstructions is the incorporation of a more quantitative description of the kinematics within extended passive margins, based on observations. We have used the conjugate Southern Australia and Wilkes Land, Antarctica margins as a case study, and as part of this work have generated revised sediment thickness maps for these margins. These datasets are used to test different approaches for generating full-fit reconstructions in order to create a framework of methodologies that is globally applicable. One approach is to restore two conjugate continent-ocean boundaries (COBs) to their pre-rift configuration and then use the geometric fitting method of Hellinger (1981) and Royer and Chang (1991), used to generate fits of seafloor isochrons, to generate a “full-fit” Euler pole. To quantitatively restore the COBs to their palinspastic pre-rift configuration we integrate estimates of crustal thickness along small circle paths, defined by an initial estimate of the Euler stage pole describing plate motions during continental rifting. We then use the conjugate sets of restored COB’s as inputs to the geometric fitting method, treating them as isochrons, and so generate poles of rotation for the plate configuration prior to rifting. Two potential shortcomings of this methodology are that (1) the conjugate margins are treated independently, whereas in reality they were actually one continuous continental basin during rifting

  13. Activities for Plate Tectonics using GeoMapApp

    Science.gov (United States)

    Goodwillie, A. M.

    2016-12-01

    The concept of plate tectonics is a fundamental component of our understanding of how Earth works yet authentic, high-quality geoscience data related to plate tectonics may not be readily available to all students. To compound matters, when data is accessible, students may not possess the skills or resources necessary to explore and analyse it. As a result, much emphasis at federal and state level is now placed upon encouraging students to work with more data and more technology more often and more rigourously. Easy-to-use digital platforms offer much potential for promoting inquiry-based learning at all levels of education. GeoMapApp is one such tool. Developed at Columbia University's Lamont-Doherty Earth Observatory, GeoMapApp (http://www.geomapapp.org) is a free resource that integrates a wide range of research-grade geoscience data in one intuitive map-based interface. Simple strategies for data manipulation, visualisation and presentation allow uses to explore the data in meaningful ways. Layering and transparency capabilities further allow learners to use GeoMapApp to compare multiple data sets at once, and high-impact Save Session functionality allows a GeoMapApp project to be saved for sharing or later use. In this presentation, activities related to plate tectonics will be highlighted. One GeoMapApp activity helps students investigate plate boundaries by exploring earthquake and volcano locations. Another requires students to calculate the rate of seafloor spreading using crustal age data in various ocean basins. A third uses the GeoMapApp layering technique to explore the influence of geological forces in shaping the landscape. Each activity shown can be done by students on an individual basis, as pairs, or as groups. Educators report that student use of GeoMapApp fosters an increased sense of data "ownership" amongst students, promotes STEM skills, and provides them with access to authentic research-grade geoscience data using the same cutting

  14. Plate tectonic reconstruction of the Carpathian-Pannonian region

    Science.gov (United States)

    Csontos, L.; Vörös, A.

    2003-04-01

    Plate tectonics of the Carpathian area is controlled by microcontinents between the European and African margins and the relative movements of these margins. Beside the generally accepted Apulian (Austroalpine, West Carpathian, Dinaric) microcontinents two others: the Bihor-Getic (Tisza) and Drina-Ivanjica are introduced. The first was attached to the European margin, the second to the Apulian microcontinent. During Permian a major ocean was obliquely subducted south of the Apulian microcontinents. Drina-Ivanjica rifted off the Apulian microcontinent in the Late Permian-Middle Triassic, as a consequence of back-arc rifting. Short-lived oceans subducted by the end of Jurassic, causing Drina-Ivanjica to collide with the internal Dinaric-West Carpathian and Bihor-Getic margins. An external Penninic-Váhic ocean tract began opening in the Early Jurassic, separating the East Alpine-West Carpathian microcontinent (and its fauna) from the European shelf. Further south, the Severin-Ceahlau-Magura also began opening in the Early Jurassic, but final separation of the Bihor-Getic (and its fauna) from the European shelf did not take place until the Middle-Late Jurassic. Two oroclinal bends: the Alcapa on the Dinaric margin and the Tisza-Dacia on the South Carpathian-Getic margin are essential elements of these reconstructions. Their bending (Aptian and Albian-Maastrichtian, respectively) are suggested by paleomagnetic and tectonic transport data. The two oroclinal bends are finally opposed and pushed into the Carpathian embayment by the Paleogene. In Miocene a back-arc basin develops on older tectonic elements. Differential rotations affect the wealded microcontinents.

  15. Plate tectonics on the Earth triggered by plume-induced subduction initiation.

    Science.gov (United States)

    Gerya, T V; Stern, R J; Baes, M; Sobolev, S V; Whattam, S A

    2015-11-12

    Scientific theories of how subduction and plate tectonics began on Earth--and what the tectonic structure of Earth was before this--remain enigmatic and contentious. Understanding viable scenarios for the onset of subduction and plate tectonics is hampered by the fact that subduction initiation processes must have been markedly different before the onset of global plate tectonics because most present-day subduction initiation mechanisms require acting plate forces and existing zones of lithospheric weakness, which are both consequences of plate tectonics. However, plume-induced subduction initiation could have started the first subduction zone without the help of plate tectonics. Here, we test this mechanism using high-resolution three-dimensional numerical thermomechanical modelling. We demonstrate that three key physical factors combine to trigger self-sustained subduction: (1) a strong, negatively buoyant oceanic lithosphere; (2) focused magmatic weakening and thinning of lithosphere above the plume; and (3) lubrication of the slab interface by hydrated crust. We also show that plume-induced subduction could only have been feasible in the hotter early Earth for old oceanic plates. In contrast, younger plates favoured episodic lithospheric drips rather than self-sustained subduction and global plate tectonics.

  16. Initiation of Plate Tectonics from Post-Magma Ocean Thermo-Chemical Convection

    OpenAIRE

    Foley, Bradford J.; Bercovici, David; Elkins-Tanton, Linda T.

    2014-01-01

    Leading theories for the presence of plate tectonics on Earth typically appeal to the role of present day conditions in promoting rheological weakening of the lithosphere. However, it is unknown whether the conditions of the early Earth were favorable for plate tectonics, or any form of subduction, and thus how subduction begins is unclear. Using physical models based on grain-damage, a grainsize-feedback mechanism capable of producing plate-like mantle convection, we demonstrate that subduct...

  17. Subduction controls the distribution and fragmentation of Earth’s tectonic plates.

    Science.gov (United States)

    Mallard, Claire; Coltice, Nicolas; Seton, Maria; Müller, R Dietmar; Tackley, Paul J

    2016-07-07

    The theory of plate tectonics describes how the surface of Earth is split into an organized jigsaw of seven large plates of similar sizes and a population of smaller plates whose areas follow a fractal distribution. The reconstruction of global tectonics during the past 200 million years suggests that this layout is probably a long-term feature of Earth, but the forces governing it are unknown. Previous studies, primarily based on the statistical properties of plate distributions, were unable to resolve how the size of the plates is determined by the properties of the lithosphere and the underlying mantle convection. Here we demonstrate that the plate layout of Earth is produced by a dynamic feedback between mantle convection and the strength of the lithosphere. Using three-dimensional spherical models of mantle convection that self-consistently produce the plate size–frequency distribution observed for Earth, we show that subduction geometry drives the tectonic fragmentation that generates plates. The spacing between the slabs controls the layout of large plates, and the stresses caused by the bending of trenches break plates into smaller fragments. Our results explain why the fast evolution in small back-arc plates reflects the marked changes in plate motions during times of major reorganizations. Our study opens the way to using convection simulations with plate-like behaviour to unravel how global tectonics and mantle convection are dynamically connected.

  18. Plate tectonic regulation of global marine animal diversity

    Science.gov (United States)

    Zaffos, Andrew; Finnegan, Seth; Peters, Shanan E.

    2017-05-01

    Valentine and Moores [Valentine JW, Moores EM (1970) Nature 228:657-659] hypothesized that plate tectonics regulates global biodiversity by changing the geographic arrangement of continental crust, but the data required to fully test the hypothesis were not available. Here, we use a global database of marine animal fossil occurrences and a paleogeographic reconstruction model to test the hypothesis that temporal patterns of continental fragmentation have impacted global Phanerozoic biodiversity. We find a positive correlation between global marine invertebrate genus richness and an independently derived quantitative index describing the fragmentation of continental crust during supercontinental coalescence-breakup cycles. The observed positive correlation between global biodiversity and continental fragmentation is not readily attributable to commonly cited vagaries of the fossil record, including changing quantities of marine rock or time-variable sampling effort. Because many different environmental and biotic factors may covary with changes in the geographic arrangement of continental crust, it is difficult to identify a specific causal mechanism. However, cross-correlation indicates that the state of continental fragmentation at a given time is positively correlated with the state of global biodiversity for tens of millions of years afterward. There is also evidence to suggest that continental fragmentation promotes increasing marine richness, but that coalescence alone has only a small negative or stabilizing effect. Together, these results suggest that continental fragmentation, particularly during the Mesozoic breakup of the supercontinent Pangaea, has exerted a first-order control on the long-term trajectory of Phanerozoic marine animal diversity.

  19. The ultra low frequency electromagnetic radiation observed in the topside ionosphere above boundaries of tectonic plates

    Directory of Open Access Journals (Sweden)

    Michael A. Athanasiou

    2015-01-01

    Full Text Available In this paper we present results of a comparison between ultra low frequency (ULF electromagnetic (EM radiation, recorded by an electric field instrument onboard the satellite detection of electromagnetic emissions transmitted from earthquake regions in the topside ionosphere, and the seismicity of regions with high and low seismic activity. In particular, we evaluated the energy variations of the ULF Ezelectric field component during a period of four years (2006-2009, in order to examine the possible relation of ULF EM radiation with seismogenic regions located in Central America, Indonesia, the Eastern Mediterranean Basin and Greece. As a tool for evaluating the ULF Ez energy variations we used singular spectrum analysis techniques. The results of our analysis clearly show a significant increase of the ULF EM energy emitted from regions of highest seismic activity at the boundaries tectonic plates. Furthermore, we found that higher electromagnetic radiation was detected in a region above the northern- western Greek Arc (R1 than above the adjacent region including Athens and its urban area. We interpret these results of the present study as suggesting that: i the seismogenic regions at the boundary of tectonic plates radiate ULF EM emissions observed by satellites in the topside ionosphere; and ii that this EM radiation is not only related with the occurrence time of great (M≥5 earthquakes, but it is often present in intermediate times and it appears as a quasi-permanent phenomenon.

  20. The Earth's Mantle Is Solid: Teachers' Misconceptions About the Earth and Plate Tectonics.

    Science.gov (United States)

    King, Chris

    2000-01-01

    Discusses the misconceptions revealed by the teachers' answers and outlines more accurate answers and explanations based on established evidence and uses these to provide a more complete understanding of plate tectonic process and the structure of Earth. (Author/YDS)

  1. Plate tectonic evolution of the Mediterranean-Middle East region

    Science.gov (United States)

    Gealey, W. K.

    1988-12-01

    An interpretive model for the Mesozoic-Cenozoic plate tectonic evolution of the Mediterranean and adjacent areas is illustrated by a series of paleoposition maps at selected intervals between the Late Triassic and Recent. This interval witnessed an important period of tensional development during the Triassic and Jurassic that fragmented Pangea after its Late Paleozoic consolidation. A number of oceanic areas evolved through Jurassic time, all of which have since been consumed during the Alpine orogeny. During the Cretaceous and Tertiary, sea-floor spreading geometry in the North and South Atlantic resulted in convergence between Africa and Eurasia that controlled the evolution of the Mediterranean and adjacent Middle East areas from the Late Mesozoic to Recent. The interpretation departs from several previous ones in the following respects: (1) The Eastern Mediterranean and adjacent Middle East area are interpreted to have developed as two seaways with an intervening continental sliver derived from Africa that now comprises Central Turkey and West Iran. These seaways persisted from the Late Triassic to Late Cretaceous, by which time they were largely consumed by northward subduction. (2) Spreading that produced the present Eastern Mediterranean Sea developed during the Late Cretaceous, driving the Tripolitza-Eratosthenes-Iskenderun continental fragments northward from Africa to collision with Central Turkey as the preceding southern arm of the Mesozoic Tethys sea-floor was entirely consumed. Initial block faulting in this zone occurred during the Jurassic and Early Cretaceous but without subsidence reaching clearly bathyal depths until the Cenomanian-Turonian. This differs from the timing of events in the "Ionian" sequence of the Pindic Nappe of Crete, which shows a change from shallow carbonate shelf in the Triassic to deep basin in the Liassic to the north of equivalent platform facies of the Tripolitza Nappe. (3) Moesia and Rhodope are concluded to have been a

  2. Plate tectonics, mantle convection and D'' seismic structures

    Science.gov (United States)

    Wen, Lianxing

    This thesis adopts multidisciplinary (geodynamical and seismological) approaches toward understanding dynamics of the Earth's mantle. My geodynamical approach is directed at understanding the relationship between large-scale surface observables (geoid, topography, plate motions) and mantle rheology and convection of the present-day Earth. In chapter 2, I remove shallow mantle structure of various tectonic features to generate "residual tomography." In chapter 3, I show that the pattern, spectrum and amplitude of the "residual topography" are consistent with shallow origin of the "Earth surface dynamic topography;" the long wavelength geoid and topography (l = 2-3) are successfully explained by density models inferred from the "residual tomography," assuming layered mantle convection stratified at the "920 km seismic discontinuity." In chapter 4, I develop a new method to calculate mantle flow with lateral variation of viscosity. The viscosity contrast between continental and oceanic regions is identified to have dominating effects on both the observed poloidal/toroidal ratio and pattern of toroidal motions at long wavelengths. My seismological approach is focused on exploring fine structures near the core-mantle boundary (CMB) and developing new seismic techniques. I discuss the method development and strategies to explore fine structures in the following chapters. In chapter 5, I develop a hybrid method, a combination of analytical and numerical methods, with numerical methods applied in heterogeneous regions only. In chapter 6, I constrain the general structures of the ultra low velocity zones (ULVZ) near the CMB under the south-east Pacific and Iceland. The SKS-SPdKS data are explained by ULVZ with P-velocity reduction of 10%, horizontal length-scales of about 250 km and height of about 40 km. S-velocity reduction of 30% is consistent with the data. In chapter 7, I constrain the detailed structures of the ULVZ near the CMB from observed broadband PKP precursors

  3. A plate tectonics oddity: Caterpillar-walk exhumation of subducted continental crust

    NARCIS (Netherlands)

    Tirel, C.; Brun, J.-P.; Burov, E.; Wortel, M.J.R.; Lebedev, S.

    2013-01-01

    Since plate tectonics began on Earth, grandiose "subduction factories" have continually shaped the continents, accreting continental blocks and new crust at the convergent plate boundaries. An enigmatic product of subduction factories is the high-pressure to ultrahigh-pressure (HP-UHP) metamorphic

  4. Barrel organ of plate tectonics - a new tool for outreach and education

    Science.gov (United States)

    Broz, Petr; Machek, Matěj; Šorm, Zdar

    2016-04-01

    Plate tectonics is the major geological concept to explain dynamics and structure of Earth's outer shell, the lithosphere. In the plate tectonic theory processes in the Earth lithosphere and its dynamics is driven by the relative motion and interaction of lithospheric plates. Geologically most active regions on Earth often correlate with the lithospheric plate boundaries. Thus for explaining the earth surface evolution, mountain building, volcanism and earthquake origin it is important to understand processes at the plate boundaries. However these processes associated with plate tectonics usually require significant period of time to take effects, therefore, their entire cycles cannot be directly observed in the nature by humans. This makes a challenge for scientists studying these processes, but also for teachers and popularizers trying to explain them to students and to the general public. Therefore, to overcome this problem, we developed a mechanical model of plate tectonics enabling demonstration of most important processes associated with plate tectonics in real time. The mechanical model is a wooden box, more specifically a special type of barrel organ, with hand painted backdrops in the front side. These backdrops are divided into several components representing geodynamic processes associated with plate tectonics, specifically convective currents occurring in the mantle, sea-floor spreading, a subduction of the oceanic crust under the continental crust, partial melting and volcanism associated with subduction, a formation of magmatic stripes, an ascent of mantle plume throughout the mantle, a volcanic activity associated with hot spots, and a formation and degradation of volcanic islands on moving lithospheric plate. All components are set in motion by a handle controlled by a human operator, and the scene is illuminated with colored lights controlled automatically by an electric device embedded in the box. Operation of the model may be seen on www

  5. Geodynamic evolution of the Earth over the Phanerozoic: Plate tectonic activity and palaeoclimatic indicators

    Directory of Open Access Journals (Sweden)

    Christian Vérard

    2015-04-01

    In this paper, we compare values derived from the tectonic model (ages of oceanic floor, production and subduction rates, tectonic activity with a combination of chemical proxies (namely CO2, 87Sr/86Sr, glaciation evidence, and sea-level variations known to be strongly influenced by tectonics. One of the outstanding results is the observation of an overall decreasing trend in the evolution of the global tectonic activity, mean oceanic ages and plate velocities over the whole Phanerozoic. We speculate that the decreasing trend reflects the global cooling of the Earth system. Additionally, the parallel between the tectonic activity and CO2 together with the extension of glaciations confirms the generally accepted idea of a primary control of CO2 on climate and highlights the link between plate tectonics and CO2 in a time scale greater than 107 yr. Last, the wide variations observed in the reconstructed sea-floor production rates are in contradiction with the steady-state model hypothesized by some.

  6. Leading and trailing edges of moving plates record contrasting thermal, mechanical, tectonic and stratigraphic histories

    Science.gov (United States)

    Bodur, O. F.; Rey, P. F.; Müller, D.

    2017-12-01

    At the transition between thick continental plates and thinner adjacent oceanic plates, the deep-seated corner of the related lithospheric mantle step is exposed to thermomechanical erosion during plate motion, and lateral variations in lithospheric thickness and temperature at these regions initiate a corner flow. Here, we present a suite of thermomechanical numerical experiments to document and characterize the mechanical and thermal evolution of the trailing and leading edge of a moving plate. We show that the geometry of the trailing and leading margins of plates evolve by a combination of thermomechanical accretion or erosion, respectively. This drives subsidence and uplift, part of which is dynamically driven by the mantle flow, and the remainder is an isostatic response to the change in structure and/or temperature of the margins. Interestingly, leading and trailing edges record contrasting tectonic histories with magnitudes of extension/contraction measurable after tens of million years of plate motion. Our numerical experiments predict different sediment supply and accommodation space, along with different tectonics and heat flow for different margins during sedimentation. These suggest that measurable differences in tectonics and stratigraphy should exist between the trailing and leading margins of moving continents. This new modelling approach will provide new insights into fundamental differences in the evolution of Australian passive margin basins regarding their subsidence, thermal evolution and stratigraphy depending on their location along the southern, trailing edge or the northern leading edge of the continent.

  7. Comparing the Plate-Tectonics-Related Misconceptions of High School Students and University Undergraduates

    Science.gov (United States)

    Kàdàr, Anett; Farsang, Andrea

    2017-01-01

    International research into the nature, emergence, and development of geographical misconceptions is substantial. However, Hungarian educational research lags behind in exploring this phenomenon in detail. The present study identified some plate-tectonics-related misconceptions of three distinctive groups of students: ninth-grade secondary school…

  8. Introduction of the Concepts of Plate Tectonics into Secondary-School Earth Science Textbooks.

    Science.gov (United States)

    Glenn, William Harold

    1992-01-01

    Secondary school earth-science textbooks in print from 1960 through 1979 were examined to determine how rapidly concepts of plate tectonics were incorporated into those texts during the period when scientists' views about these concepts were evolving most rapidly. Suggests that delays were probably due to an unwillingness to engage in speculation…

  9. Plate Tectonics: The Way the Earth Works. Teacher's Guide. LHS GEMS.

    Science.gov (United States)

    Cuff, Kevin

    This teacher guide presents a unit on plate tectonics and introduces hands-on activities for students in grades 6-8. In each unit, students act as real scientists and gather evidence by using science process skills such as observing, graphing, analyzing data, designing and making models, visualizing, communicating, theorizing, and drawing…

  10. Using a Web GIS Plate Tectonics Simulation to Promote Geospatial Thinking

    Science.gov (United States)

    Bodzin, Alec M.; Anastasio, David; Sharif, Rajhida; Rutzmoser, Scott

    2016-01-01

    Learning with Web-based geographic information system (Web GIS) can promote geospatial thinking and analysis of georeferenced data. Web GIS can enable learners to analyze rich data sets to understand spatial relationships that are managed in georeferenced data visualizations. We developed a Web GIS plate tectonics simulation as a capstone learning…

  11. Plate Tectonics as a Far-From-Equilibrium Self-Organized Dissipative System

    Science.gov (United States)

    Anderson, D. L.

    2001-12-01

    A fluid above the critical Rayleigh number is far from equilibrium and spontaneously organizes itself into patterns involving the collective motion of large numbers of molecules which are resisted by the viscosity of the fluid. No external template is involved in forming the pattern. In 1928 Pearson showed that Bénard's experiments were driven by variations in surface tension at the top of the fluid and the surface motions drove convection in the fluid. In this case, the surface organized itself AND the underlying fluid. Both internal buoyancy driven flow and flow driven by surface forces can be far-from-equilibrium self-organized open systems that receive energy and matter from the environment. In the Earth, the cold thermal boundary layer at the surface drives plate tectonics and introduces temperature, shear and pressure gradients into the mantle that drive mantle convection. The mantle provides energy and material but may not provide the template. Plate tectonics is therefore a candidate for a far-from-equilibrium dissipative self-organizing system. Alternatively, one could view mantle convection as the self-organized system and the plates as simply the surface manifestation. Lithospheric architecture also imposes lateral temperature gradients onto the mantle which can drive and organize flow. Far-from-equilibrium self-organization requires; an open system, interacting parts, nonlinearities or feedbacks, an outside steady source of energy or matter, multiple possible states and a source of dissipation. In uniform fluids viscosity is the source of dissipation. Sources of dissipation in the plate system include bending, breaking, folding, shearing, tearing, collision and basal drag. These can change rapidly, in contrast to plate driving forces, and introduce the sort of fluctuations that can reorganize far-from-equilibrium systems. Global plate reorganizations can alternatively be thought of as convective overturns of the mantle, or thermal weakening of plates

  12. Crustal history of Margarita Island (Venezuela) in detail: Constraint on the Caribbean plate-tectonic scenario

    Science.gov (United States)

    Stöckhert, Bernhard; Maresch, Walter V.; Brix, Manfred; Kaiser, Claudia; Toetz, Andreas; Kluge, Rolf; Krückhans-Lueder, Gabriela

    1995-09-01

    The pressure-temperature-time-deformation evolution for the crust of Margarita Island (Venezuela) has been established to allow comparison with current plate-tectonic models for the Caribbean region. On Margarita, the 12 recognizable stages of development can be summarized in terms of the following evolving tectonic settings: Protolith evolution as Aptian-Albian or older oceanic crust, as well as continental crust with Paleozoic basement (stages 1 and 2); accretion and high-pressure metamorphism (500 600 °C, 10 14 kbar) as the Margarita Complex in the deep level of a fore arc at 100 90 Ma (stage 3); ascent, cooling, and emplacement into the intermediate crustal level of a volcanic arc at 90 80 Ma (stage 4); transform plate-margin setting at a comparable level at 80 50 Ma (stage 5); second episode of rapid uplift and cooling (stages 6 and 7); and shallow crustal level close to transform plate margin from 50 Ma to present (stages 8 to 12). This complex sequence is in excellent agreement with plate-tectonic scenarios that require a Pacific origin for the Caribbean plate and eastward migration of the Margarita Complex and its correlatives along northern South America since the Cretaceous.

  13. Plate tectonics and continental basaltic geochemistry throughout Earth history

    Science.gov (United States)

    Keller, Brenhin; Schoene, Blair

    2018-01-01

    Basaltic magmas constitute the primary mass flux from Earth's mantle to its crust, carrying information about the conditions of mantle melting through which they were generated. As such, changes in the average basaltic geochemistry through time reflect changes in underlying parameters such as mantle potential temperature and the geodynamic setting of mantle melting. However, sampling bias, preservation bias, and geological heterogeneity complicate the calculation of representative average compositions. Here we use weighted bootstrap resampling to minimize sampling bias over the heterogeneous rock record and obtain maximally representative average basaltic compositions through time. Over the approximately 4 Ga of the continental rock record, the average composition of preserved continental basalts has evolved along a generally continuous trajectory, with decreasing compatible element concentrations and increasing incompatible element concentrations, punctuated by a comparatively rapid transition in some variables such as La/Yb ratios and Zr, Nb, and Ti abundances approximately 2.5 Ga ago. Geochemical modeling of mantle melting systematics and trace element partitioning suggests that these observations can be explained by discontinuous changes in the mineralogy of mantle partial melting driven by a gradual decrease in mantle potential temperature, without appealing to any change in tectonic process. This interpretation is supported by the geochemical record of slab fluid input to continental basalts, which indicates no long-term change in the global proportion of arc versus non-arc basaltic magmatism at any time in the preserved rock record.

  14. A combined rigid/deformable plate tectonic model for the evolution of the Indian Ocean

    Science.gov (United States)

    Watson, J. G.; Glover, C. T.; Adriasola Munoz, A. C.; Harris, J. P.; Goodrich, M.

    2012-04-01

    Plate tectonic reconstructions are essential for placing geological information in its correct spatial context, understanding depositional environments, defining basin dimensions and evolution, and serve as a basis for palaeogeographic mapping and for palaeo-climate modelling. Traditional 'rigid' plate reconstructions often result in misfits (overlaps and underfits) in the geometries of juxtaposed plate margins when restored to their pre-rift positions. This has been attributed to internal deformation pre- and/or syn- continental break-up. Poorly defined continent-ocean boundaries add to these problems. To date, few studies have integrated continental extension within a global model. Recent plate tectonic reconstructions based on the relative motions of Africa, Madagascar, India and Antarctica during the break-up of eastern Gondwana have not taken into account the effects of deformation; particularly between India and Madagascar, and India and the Seychelles. A deformable plate model is in development that builds on the current rigid plate model to describe the complex multiphase break-up history between Africa, Madagascar, Seychelles and India, the associated magmatic activity and subsequent India/Eurasia collision. The break-up of eastern Gondwana occurred in the mid Jurassic by rifting between Africa and the India-Madagascar-Australian-Antarctica plates, followed by the Late Jurassic drift of India away from Australia and the Cretaceous break-up of Australia and Antarctica. The northwards drift of the Seychelles-India block in the Tertiary was accommodated by the opening of the Laxmi Basin. This was followed by the eruption of the extensive Deccan flood basalts and the separation of India and the Seychelles. Crustal domains on volcanic margins can be very difficult to define due to the accretion of magmatic material. On these margins, there is much speculation on the position of the continent-ocean boundary and the timing of rifting and sea-floor spreading. The

  15. Alfred Wegener - From Continental Drift to Plate Tectonics

    Indian Academy of Sciences (India)

    The seawater occupies more than 70% of the Earth's surface. Several oceanographic studies and deep-sea surv~ys carried out after the World War II, established the fact that the ocean basement is not as flat and featureless as it was originally thought. The sea floor consists of Mid-Ocean ridges, huge volcanic moun-.

  16. Topography of Venus and earth - A test for the presence of plate tectonics

    Science.gov (United States)

    Head, J. W.; Yuter, S. E.; Solomon, S. C.

    1981-01-01

    Comparisons of earth and Venus topography by use of Pioneer/Venus radar altimetry are examined. Approximately 93% of the Venus surface has been mapped with a horizontal resolution of 200 km and a vertical resolution of 200 m. Tectonic troughs have been indicated in plains regions which cover 65% of Venus, and hypsometric comparisons between the two planets' elevation distributions revealed that while the earth has a bimodal height distribution, Venus displays a unimodal configuration, with 60% of the planet surface within 500 m of the modal planet radius. The effects of mapping the earth at the same resolution as the Venus observations were explored. Continents and oceans were apparent, and although folded mountains appeared as high spots, no indications of tectonic activity were discernible. A NASA Venus Orbiting Imaging radar is outlined, which is designed to detect volcanoes, folded mountain ranges, craters, and faults, and thereby allow definition of possible plate-tectonic activity on Venus.

  17. Experimental constraints on the degree of melting beneath tectonic plates

    Science.gov (United States)

    Clark, A. N.; Lesher, C. E.

    2017-12-01

    Determining the volume and geometric distribution of silicate melts is fundamentally important to understand the current structure of the Earth as well as the dynamics of the Earth's interior. Regions in the upper mantle and crust that have lower velocities than the 1D global average are commonly attributed to the presence of silicate melts. Constraining melt fraction and distribution from seismic data requires a robust equation of state for silicate melts. Commonly, silicate melts are modeled at high pressure using equations of state developed for crystalline materials (e.g. the Birch-Murnaghan equation of state). However, amorphous silicates (glasses and melts), which lack long-range ordering, violate Birch's law at high pressures and high temperatures (Clark et al., 2016). We present a new model for seismic velocity reductions that accounts for the violation of Birch's law (anomalous compressibility) observed in amorphous silicates, rendering compressional wave velocities more sensitive to melt fraction and distribution than previous estimates. Forward modeling that combines our experimental data with the analytical solution of Takei (2002) predicts comparable velocity reductions for compressional and shear waves for partially molten mantle. Additionally, models that use crystalline equations of state to determine melt fraction at high pressure may overestimate melt fraction by 20% at pressures corresponding to the lithosphere-asthenosphere boundary (LAB) with the overestimation increasing with depth (e.g. a factor of 2 at the transition zone). By applying our results to recent seismic studies below the western Pacific plate that have reported low velocity regions associated with the lithosphere - asthenosphere boundary (LAB), we predict melt present at Journal of Geophysical Research: Solid Earth, v. 121, no. 6, p. 4232-4248. Takei, Y., 2002, Journal of Geophysical Research: Solid Earth (1978-2012), v. 107, no. B2, p. 6-12.

  18. Titanium isotopic evidence for felsic crust and plate tectonics 3.5 billion years ago.

    Science.gov (United States)

    Greber, Nicolas D; Dauphas, Nicolas; Bekker, Andrey; Ptáček, Matouš P; Bindeman, Ilya N; Hofmann, Axel

    2017-09-22

    Earth exhibits a dichotomy in elevation and chemical composition between the continents and ocean floor. Reconstructing when this dichotomy arose is important for understanding when plate tectonics started and how the supply of nutrients to the oceans changed through time. We measured the titanium isotopic composition of shales to constrain the chemical composition of the continental crust exposed to weathering and found that shales of all ages have a uniform isotopic composition. This can only be explained if the emerged crust was predominantly felsic (silica-rich) since 3.5 billion years ago, requiring an early initiation of plate tectonics. We also observed a change in the abundance of biologically important nutrients phosphorus and nickel across the Archean-Proterozoic boundary, which might have helped trigger the rise in atmospheric oxygen. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  19. Tethyan evolution of Turkey: A plate tectonic approach

    Science.gov (United States)

    ^Şengör, A. M. Celâl; Yilmaz, Yücel

    nappe systems of the Taurides, and buried beneath these, the metamorphic axis of Anatolia, the Anatolides. The Maden basin closed during the early late Eocene by north-dipping subduction, synthetic to the Inner-Tauride subduction zone that had switched from south-dipping subduction beneath the Bitlis—Pötürge fragment to north dipping subduction beneath the Anatolide—Tauride platform during the later Palaeocene. Finally, the terminal collision of Arabia with Eurasia in eastern Turkey eliminated the Çüngüş basin as well and created the present tectonic regime of Turkey by pushing a considerable piece of it eastwards along the two newly-generated transform faults, namely those of North and East Anatolia. Much of the present eastern Anatolia is underlain by an extensive mélange prism that accumulated during the late Cretaceous—late Eocene interval north and east of the Bitlis—Pötürge fragment.

  20. JaMBES: A "New" Way of Calculating Plate Tectonic Reconstruction

    Science.gov (United States)

    Chambord, A. I.; Smith, E. G. C.; Sutherland, R.

    2014-12-01

    Calculating the paleoposition of tectonic plates using marine geophysical data has been usually done by using the Hellinger criterion [Hellinger, 1981]. However, for the Hellinger software [Kirkwood et al., 1999] to produce stable results, we find that the input data must be abundant and spatially well distributed. Although magnetic anomalies and fracture zone data have been increasingly abundant since the 1960s, some parts of the globe remain too sparsely explored to provide enough data for the Hellinger code to provide satisfactory rotations. In this poster, we present new software to calculate the paleopositions of tectonic plates using magnetic anomalies and fracture zone data. Our method is based on the theory of plate tectonics as introduced by [Bullard et al., 1965] and [Morgan, 1968], which states that ridge segments (ie. magnetic lineations) and fracture zones are at right angles to each other. In order to test our software, we apply it to a region of the world where climatic conditions hinder the acquisition of magnetic data: the Southwest Pacific, between New Zealand and Antarctica from breakup time to chron 20 (c43Ma). Bullard, E., J. E. Everett, and A. G. Smith (1965), The fit of continents around the atlantic, Philosophical Transactions of the Royal Society of London, Series A: Mathematical and Physical Sciences, 258(1088), 41-51. Hellinger, S. J. (1981), The uncertainties of finite rotations in plate tectonics, Journal of Geophysical Research, 86(B10), 9312-9318. Kirkwood, B. H., J. Y. Royer, T. C. Chang, and R. G. Gordon (1999), Statistical tools for estimating and combining finite rotations and their uncertainties, Geophysical Journal International, 137(2), 408-428. Morgan, W. J. (1968), Rises, trenches, great faults, and crustal blocks, Journal of Geophysical Research, 73(6), 1959-1982.

  1. The fate of water within Earth and super-Earths and implications for plate tectonics.

    Science.gov (United States)

    Tikoo, Sonia M; Elkins-Tanton, Linda T

    2017-05-28

    The Earth is likely to have acquired most of its water during accretion. Internal heat of planetesimals by short-lived radioisotopes would have caused some water loss, but impacts into planetesimals were insufficiently energetic to produce further drying. Water is thought to be critical for the development of plate tectonics, because it lowers viscosities in the asthenosphere, enabling subduction. The following issue persists: if water is necessary for plate tectonics, but subduction itself hydrates the upper mantle, how is the upper mantle initially hydrated? The giant impacts of late accretion created magma lakes and oceans, which degassed during solidification to produce a heavy atmosphere. However, some water would have remained in the mantle, trapped within crystallographic defects in nominally anhydrous minerals. In this paper, we present models demonstrating that processes associated with magma ocean solidification and overturn may segregate sufficient quantities of water within the upper mantle to induce partial melting and produce a damp asthenosphere, thereby facilitating plate tectonics and, in turn, the habitability of Earth-like extrasolar planets.This article is part of the themed issue 'The origin, history and role of water in the evolution of the inner Solar System'. © 2017 The Authors.

  2. Mantle rheology and the scaling of bending dissipation in plate tectonics

    Science.gov (United States)

    Rose, I. R.; Korenaga, J.

    2011-06-01

    Plate tectonics on Earth involves the bending deformation of plates at subduction zones, and because plates are generally considered to be stiff owning to the rheology of mantle minerals, the role of energy dissipation by plate bending in the global energy balance has been frequently debated in the recent literature. Here we consider how bending dissipation should scale with slab parameters such as dip angle, plate age, the radius of curvature, and plate velocity by systematically exploring the parameter space with instantaneous Stokes flow calculations. We derive the scaling of bending dissipation for a range of mantle viscosity functions, including pseudoplastic rheology with olivine flow laws. Our results indicate that, as we move away from the isoviscous case, the scaling gradually deviates from what has commonly been assumed in previous studies, most notably for the radius exponent, which exhibits more than threefold reduction and even a sign reversal in some cases. These modifications in scaling exponents originate in the complication of the deformation field caused by viscosity variations within the bending plate. Approximating the lithospheric rheology by a single effective viscosity in the dynamical models of subduction has been a common practice, but we suggest that such approximation may limit the geological relevance of modeling studies, in particular when estimating the significance of bending dissipation.

  3. Duality of thermal regimes is the distinctive characteristic of plate tectonics since the Neoarchean

    Science.gov (United States)

    Brown, Michael

    2006-11-01

    Ultrahigh-temperature (UHT) granulite metamorphism is documented predominantly in the Neoarchean to Cambrian rock record, but UHT granulite metamorphism also may be inferred at depth in Cenozoic orogenic systems. The first occurrence of UHT granulite metamorphism in the record signifies a change in geodynamics that generated transient sites of very high heat flow. Many UHT granulite metamorphic belts may have developed in settings analogous to modern continental backarcs; on a warmer Earth, destruction of oceans floored by thinner lithosphere may have generated hotter backarcs than those associated with the modern Pacific ring of fire. Medium-temperature eclogite high- pressure (EHP) granulite metamorphism is documented in the Neoarchean rock record and at intervals throughout the Proterozoic and Paleozoic record. EHP granulite metamorphic belts are complementary to UHT granulite metamorphic belts in that they are generally inferred to record subduction-to-collision orogenesis. Blueschists become evident in the Neoproterozoic rock record, but lawsonite blueschist eclogite metamorphism (high pressure [HP]) and ultrahigh-pressure metamorphism (UHP) characterized by coesite or diamond are predominantly Phanerozoic phenomena. HP-UHP metamorphism registers the low thermal gradients and deep subduction of continental crust during the early stage of subduction-to-collision orogenesis. A duality of metamorphic belts—reflecting a duality of thermal regimes—appears in the record only since the Neoarchean Era. A duality of thermal regimes is the hallmark of modern plate tectonics, and the duality of metamorphic belts is the characteristic imprint of plate tectonics in the rock record. The occurrence of both UHT and EHP granulite metamorphism since the Neoarchean marks the onset of a “Proterozoic plate tectonics” regime, which evolved during a Neoproterozoic transition to the modern plate tectonics regime, characterized by colder subduction as chronicled by HP

  4. Plate tectonics

    Digital Repository Service at National Institute of Oceanography (India)

    Chaubey, A.K.

    ), for the first time, have proposed time scale for geomagnetic reversals making use of the Potassium- Argon (K-Ar) dates. Further, discovery of short polarity event of duration as small as 10 5 years within the major polarity intervals have led to modify... of geomagnetism e.g. Brunhes, Matuyama, Gauss, Gilbert, while the short duration polarity events (short intra-epoch fluctuations) were named after the sites of their discovery (Cox et al., 1964). A polarity epoch may contain several polarity events and can...

  5. Development of the Plate Tectonics and Seismology markup languages with XML

    Science.gov (United States)

    Babaie, H.; Babaei, A.

    2003-04-01

    The Extensible Markup Language (XML) and its specifications such as the XSD Schema, allow geologists to design discipline-specific vocabularies such as Seismology Markup Language (SeismML) or Plate Tectonics Markup Language (TectML). These languages make it possible to store and interchange structured geological information over the Web. Development of a geological markup language requires mapping geological concepts, such as "Earthquake" or "Plate" into a UML object model, applying a modeling and design environment. We have selected four inter-related geological concepts: earthquake, fault, plate, and orogeny, and developed four XML Schema Definitions (XSD), that define the relationships, cardinalities, hierarchies, and semantics of these concepts. In such a geological concept model, the UML object "Earthquake" is related to one or more "Wave" objects, each arriving to a seismic station at a specific "DateTime", and relating to a specific "Epicenter" object that lies at a unique "Location". The "Earthquake" object occurs along a "Segment" of a "Fault" object, which is related to a specific "Plate" object. The "Fault" has its own associations with such things as "Bend", "Step", and "Segment", and could be of any kind (e.g., "Thrust", "Transform'). The "Plate" is related to many other objects such as "MOR", "Subduction", and "Forearc", and is associated with an "Orogeny" object that relates to "Deformation" and "Strain" and several other objects. These UML objects were mapped into XML Metadata Interchange (XMI) formats, which were then converted into four XSD Schemas. The schemas were used to create and validate the XML instance documents, and to create a relational database hosting the plate tectonics and seismological data in the Microsoft Access format. The SeismML and TectML allow seismologists and structural geologists, among others, to submit and retrieve structured geological data on the Internet. A seismologist, for example, can submit peer-reviewed and

  6. Tectonics and Non-isostatic Topography of the Mariana Trench and Adjacent Plates

    Science.gov (United States)

    Hongyu, L.; Lin, J.; Zhou, Z.; Zhang, F.

    2017-12-01

    Multi-types of geophysical data including multibeam bathymetry, sediment thickness, gravity anomaly, and crustal magnetic age were analyzed to investigate tectonic processes of the Mariana Trench and the surrounding plates. We calculated non-Airy-isostatic topography by removing from the observed bathymetry the effects of sediment loading, thermal subsidence, and Airy local isostatically-compensated topography. The Mariana Trench was found to be associated with a clearly defined zone of negative non-isostatic topography, which was caused by flexural bending of the subducting Pacific plate and with the maximum depth anomaly and flexural bending near the Challenger Deep. In contrast, the Caroline Ridge and Caroline Islands Chain have much more subdued non-isostatic topography, indicating their higher topography is largely compensated by thicker crust. Along the Mariana Trough, the northern and central segments appear to be associated with relatively low magma supply as indicated by the relatively low topography and thin crust. In contrast, the southern Mariana Trough is associated with relatively high magma supply as indicated by the relatively high and smoother topography, an axial high spreading center, and relatively thick crust. The southern end of the Mariana Trough was also found to be associated with positive non-isostatic topographic anomaly, which might be caused by the complex tectonic deformation of the overriding Mariana and Philippine Sea plates and their interaction with the subducting Pacific plate. Analysis further revealed that the southern Mariana Arc, located between the Mariana Trench and Mariana Trough, is associated with positive non-isostatic topographic anomalies, which may be explained by the late stage magmatic loading on the older and thus stronger lithospheric plate of the Mariana volcanic arc.

  7. Initiation of modern-style plate tectonics recorded in Mesoarchean marine chemical sediments

    Science.gov (United States)

    Satkoski, Aaron M.; Fralick, Philip; Beard, Brian L.; Johnson, Clark M.

    2017-07-01

    The chemistry of the oceans in part reflects a balance between inputs from the continents and mantle. Traditionally, it has been thought that Archean ocean chemistry was dominated by mantle sources, but recent work has suggested that continental weathering during the Archean provided a much higher flux to the oceans than previously recognized. Here, we present new Rb-Sr and Sm-Nd isotope compositions on carbonate (dolomite and limestone) from the 2.94 Ga Red Lake and 2.80 Ga Steep Rock groups in the Superior Province, Canada to assess the potential impact continental weathering had on ocean chemistry during the Mesoarchean, a time when initiation of modern-style plate tectonics has been proposed to have occurred. The low Rb contents of all carbonate samples suggest that clastic contamination does not affect the Sr isotope compositions. Using O and Sr isotope modeling, we identified unaltered samples and estimate a 87Sr/86Sr ratio of 0.70173 for seawater at 2.94 Ga and 0.70182 at 2.80 Ga. Strontium isotope compositions from both Red Lake and Steep Rock indicate that seawater was significantly more radiogenic than contemporaneous mantle, and suggests that weathering of evolved continental crust was an important input to seawater. Continental weathering likely affected seawater chemistry through uplift of continental lithosphere during the initiation of modern-style plate tectonics at 3.2 Ga, a model that is contrary to those that suggest the Archean continents were small in extent and largely submerged. Initiation of modern-style plate tectonics and associated continental weathering had an important effect on the biosphere, including increased nutrient delivery, as well as creation of ecological niches that allowed development of the first biologically produced shallow marine redox gradients.

  8. Stagnant lids and mantle overturns: Implications for Archaean tectonics, magmagenesis, crustal growth, mantle evolution, and the start of plate tectonics

    Directory of Open Access Journals (Sweden)

    Jean H. Bédard

    2018-01-01

    probability that oceanic crustal segments could founder in an organized way, producing a gradual evolution of pre-subduction convergent margins into modern-style active subduction systems around 2.5 Ga. Plate tectonics today is constituted of: (1 a continental drift system that started in the Early Archaean, driven by deep mantle currents pressing against the Archaean-age sub-continental lithospheric mantle keels that underlie Archaean cratons; (2 a subduction-driven system that started near the end of the Archaean.

  9. Cenozoic Plate tectonic history of the northern Venezuela-Trinidad Area

    Science.gov (United States)

    Erlich, Robert N.; Barrett, S. F.

    1990-02-01

    Geological and geophysical data, coupled with recent plate tectonic reconstructions, suggest that the Cenozoic geologic history of the northern Venezuela-Trinidad area has been dominated by strike-slip displacement of discrete crustal blocks. Allochthonous terranes within the area include metavolcanic rocks of the Cretaceous Villa de Cura Group and metamorphic rocks of the Precambrian to Cretaceous Cordillera de la Costa. A relatively competent crustal block (Margarita Block) is defined by an outline around the metamorphic basement of Margarita Island, the Araya/Paria peninsula, the Northern Range of Trinidad, and Tobago Island. Reconstruction of the Margarita Block to its original position requires at least partial closure of the Falcon Basin, closure of the Bonaire and Cariaco basins, and restoration of about 50 km of motion on both the Oca and Bocono faults. Post middle Eocene eastward translation of the Caribbean plate caused eastward motion of the Margarita Block. A minor change in relative plate motion during the late Oligocene or early Miocene produced a right step in the Moron fault, forming the Cariaco pull-apart basin and El Pilar fault zone. Maximum offset on El Pilar fault is estimated to be no more than 125 km, though displacement along the entire fault zone may have been greater. Transpressional stresses between the Caribbean plate and northern South America caused folding of the Serrania del Interior of Venezuela and the Central Range of Trinidad. Eastward migration of transpressional stresses at the southeastern corner of the Caribbean-South American plate boundary is being accommodated by formation of oblique thrusts, transpressive anticlines, and downwarping of the crust. Bouguer gravity data suggest that Jurassic-aged Atlantic oceanic crust is being depressed as the Caribbean plate expands into the Demerara Plateau area. This study suggests that the faults and transtensional/transpressional/compressional structures identified in this study are

  10. Using Google Earth to Explore Multiple Data Sets and Plate Tectonic Concepts

    Science.gov (United States)

    Goodell, L. P.

    2015-12-01

    Google Earth (GE) offers an engaging and dynamic environment for exploration of earth science data. While GIS software offers higher-level analytical capability, it comes with a steep learning curve and complex interface that is not easy for the novice, and in many cases the instructor, to negotiate. In contrast, the intuitive interface of GE makes it easy for students to quickly become proficient in manipulating the globe and independently exploring relationships between multiple data sets at a wide range of scales. Inquiry-based, data-rich exercises have been developed for both introductory and upper-level activities including: exploration of plate boundary characteristics and relative motion across plate boundaries; determination and comparison of short-term and long-term average plate velocities; crustal strain analysis (modeled after the UNAVCO activity); and determining earthquake epicenters, body-wave magnitudes, and focal plane solutions. Used successfully in undergraduate course settings, for TA training and for professional development programs for middle and high school teachers, the exercises use the following GE data sets (with sources) that have been collected/compiled by the author and are freely available for non-commercial use: 1) tectonic plate boundaries and plate names (Bird, 2003 model); 2) real-time earthquakes (USGS); 3) 30 years of M>=5.0 earthquakes, plotted by depth (USGS); 4) seafloor age (Mueller et al., 1997, 2008); 5) location and age data for hot spot tracks (published literature); 6) Holocene volcanoes (Smithsonian Global Volcanism Program); 7) GPS station locations with links to times series (JPL, NASA, UNAVCO); 8) short-term motion vectors derived from GPS times series; 9) long-term average motion vectors derived from plate motion models (UNAVCO plate motion calculator); 10) earthquake data sets consisting of seismic station locations and links to relevant seismograms (Rapid Earthquake Viewer, USC/IRIS/DELESE).

  11. Driving Forces of Plate Tectonics and Evolution of the Oceanic Lithosphere and Asthenosphere

    Science.gov (United States)

    Forsyth, D. W.

    2017-12-01

    As plate tectonics became established as an excellent kinematic description of the relative motions of different blocks of the Earth's lithosphere, many investigators also began exploring the forces involved in driving the plate motions. Because the plates move at nearly constant velocities over long periods of time and inertial terms are unimportant, driving forces must always be balanced by resisting forces in a way that regulates the velocities. Forsyth and Uyeda (1975) incorporated the balancing of torques on the individual plates to help constrain the relative importance of the driving and resisting forces, as parameterized in a way based on prior model investigations of individual parts of the convecting system. We found that the primary driving force was sinking of subducting lithosphere at trenches, balanced largely by viscous resisting forces in the sub-asthenospheric mantle; that viscous drag beneath the oceanic plates was negligible; and that mid-ocean ridges provided a relatively small push. One of the early questions was whether there was buoyant upwelling on a large scale beneath mid-ocean ridges as part of a whole mantle convection system with subduction of the plates representing the downwelling limb. If so, then it would be likely that the plates were just riding on top of large convection cells. Seismic tomography has demonstrated that, on average, there are no deep roots beneath mid-ocean ridges, so that active, buoyant upwelling from the deep mantle does not exist beneath spreading centers. However, more recent tomographic studies have found asymmetry of the shear velocity structure beneath ridges in some areas, pointing to a smaller scale of active convection in the shallow mantle perhaps induced by melt retention buoyancy or the local effects of ridge/hotspot interaction.

  12. Tectonics

    Science.gov (United States)

    John Dewey will complete his term as editor-in-chief of Tectonics at the end of 1984. Clark Burchfiel's term as North American Editor will also end. Tectonics is published jointly with the European Geophysical Society. This newest of AGU's journals has already established itself as an important journal bridging the concerns of geophysics and geology.James A. Van Allen, president of AGU, has appointed a committee to recommend candidates for both editor-in-chief and North American editor for the 1985-1987 term.

  13. Plate tectonic influences on Earth's baseline climate: a 2 billion-year record

    Science.gov (United States)

    McKenzie, R.; Evans, D. A.; Eglington, B. M.; Planavsky, N.

    2017-12-01

    Plate tectonic processes present strong influences on the long-term carbon cycle, and thus global climate. Here we utilize multiple aspects of the geologic record to assess the role plate tectonics has played in driving major icehouse­-greenhouse transitions for the past 2 billion years. Refined paleogeographic reconstructions allow us to quantitatively assess the area of continents in various latitudinal belts throughout this interval. From these data we are able to test the hypothesis that concentrating continental masses in low-latitudes will drive cooler climates due to increased silicate weathering. We further superimpose records of events that are believed to increase the `weatherability' of the crust, such as large igneous province emplacement, island-arc accretion, and continental collisional belts. Climatic records are then compared with global detrital zircon U-Pb age data as a proxy for continental magmatism. Our results show a consistent relationship between zircon-generating magmatism and icehouse-greenhouse transitions for > 2 billion years, whereas paleogeographic records show no clear consistent relationship between continental configurations and prominent climate transitions. Volcanic outgassing appears to exert a first-order control on major baseline climatic shifts; however, paleogeography likely plays an important role in the magnitude of this change. Notably, climatic extremes, such as the Cryogenian icehouse, occur during a combination of reduce volcanism and end-member concentrations of low-latitudinal continents.

  14. Interaction between central volcanoes and regional tectonics along divergent plate boundaries: Askja, Iceland

    Science.gov (United States)

    Trippanera, Daniele; Ruch, Joël; Acocella, Valerio; Thordarson, Thor; Urbani, Stefano

    2018-01-01

    Activity within magmatic divergent plate boundaries (MDPB) focuses along both regional fissure swarms and central volcanoes. An ideal place to investigate their mutual relationship is the Askja central volcano in Iceland. Askja consists of three nested calderas (namely Kollur, Askja and Öskjuvatn) located within a hyaloclastite massif along the NNE-SSW trending Icelandic MDPB. We performed an extensive field-based structural analysis supported by a remote sensing study of tectonic and volcanic features of Askja's calderas and of the eastern flank of the hyaloclastite massif. In the massif, volcano-tectonic structures trend N 10° E to N 40° E, but they vary around the Askja caldera being both parallel to the caldera rim and cross-cutting on the Western side. Structural trends around the Öskjuvatn caldera are typically rim parallel. Volcanic vents and dikes are preferentially distributed along the caldera ring faults; however, they follow the NNE-SSW regional structures when located outside the calderas. Our results highlight that the Askja volcano displays a balanced amount of regional (fissure-swarm related) and local (shallow-magma-chamber related) tectonic structures along with a mutual interaction among these. This is different from Krafla volcano (to the north of Askja) dominated by regional structures and Grímsvötn (to the South) dominated by local structures. Therefore, Askja represents an intermediate tectono-magmatic setting for volcanoes located in a slow divergent plate boundary. This is also likely in accordance with a northward increase in the spreading rate along the Icelandic MDPB.

  15. Interaction between central volcanoes and regional tectonics along divergent plate boundaries: Askja, Iceland

    KAUST Repository

    Trippanera, Daniele

    2017-12-04

    Activity within magmatic divergent plate boundaries (MDPB) focuses along both regional fissure swarms and central volcanoes. An ideal place to investigate their mutual relationship is the Askja central volcano in Iceland. Askja consists of three nested calderas (namely Kollur, Askja and Öskjuvatn) located within a hyaloclastite massif along the NNE-SSW trending Icelandic MDPB. We performed an extensive field-based structural analysis supported by a remote sensing study of tectonic and volcanic features of Askja’s calderas and of the eastern flank of the hyaloclastite massif. In the massif, volcano-tectonic structures trend N 10° E to N 40° E, but they vary around the Askja caldera being both parallel to the caldera rim and cross-cutting on the Western side. Structural trends around the Öskjuvatn caldera are typically rim parallel. Volcanic vents and dikes are preferentially distributed along the caldera ring faults; however, they follow the NNE-SSW regional structures when located outside the calderas. Our results highlight that the Askja volcano displays a balanced amount of regional (fissure-swarm related) and local (shallow-magma-chamber related) tectonic structures along with a mutual interaction among these. This is different from Krafla volcano (to the north of Askja) dominated by regional structures and Grímsvötn (to the South) dominated by local structures. Therefore, Askja represents an intermediate tectono-magmatic setting for volcanoes located in a slow divergent plate boundary. This is also likely in accordance with a northward increase in the spreading rate along the Icelandic MDPB.

  16. Evolution of the western segment of Juan Fernández Ridge (Nazca Plate): plume vs. plate tectonic processes

    Science.gov (United States)

    Lara, Luis E.; Rodrigo, Cristián; Reyes, Javier; Orozco, Gabriel

    2014-05-01

    The Juan Fernandez Ridge (Eastern Pacific, Nazca Plate) is thought to be a classic hot spot trail because of the apparent age progression observed in 40Ar-39Ar data. However, geological evidence and some thermochronological data suggest a more complex pattern with a rejuvenation stage in Robinson Crusoe Island, the most eroded of the Juan Fernandez Archipelago. In fact, a postshield stage at 900-700 ka separates the underlying shield-related pile from the post-erosional alkaline succession (Ba/Yb=38.15; La/Yb=15.66; Ba/Y=20.27; Ba/Zr=2.31). Shield volcanoes grew at high effusion rate at ca. 5-4 Ma erupting mostly tholeiitic to transitional magmas (Ba/Yb=18.07-8.32; La/Yb=4.59-9.84; Ba/Y=4.24-8.18; Ba/Zr=0.73-1.09). Taken together, shield volcanoes form a continuous plateau with a base at ca. 3900 mbsl. However, a more complex structural pattern can be inferred from geophysical data, which suggest some intracrustal magma storage and a more extended area of magma ascent. A role for the Challenger Fracture Zone is hypothesized fueling the controversy between pristine plume origin and the effect of plate tectonic processes in the origin of intraplate volcanism. This research is supported by FONDECYT Project 1110966.

  17. Active faulting and transpression tectonics along the plate boundary in North Africa

    Directory of Open Access Journals (Sweden)

    Mustapha Meghraoui

    2013-01-01

    Full Text Available We present a synthesis of the active tectonics of the northern Atlas Mountains, and suggest a kinematic model of transpression and block rotation that illustrates the mechanics of this section of the Africa–Eurasia plate boundary. Neotectonic structures and significant shallow seismicity (with Mw >5.0 indicate that coeval E-W-trending, right-lateral faulting and NE-SW, thrust-related folding result from oblique convergence at the plate boundary, which forms a transpressional system. The strain distribution obtained from fault–fold structures and P axes of focal mechanism solutions, and the geodetic (NUVEL-1 and GPS convergence show that the shortening and convergence directions are not coaxial. The transpressional strain is partitioned along the strike and the quantitative description of the displacement field yields a compression-to-transcurrence ratio varying from 33% near Gibraltar, to 50% along the Tunisian Atlas. Shortening directions oriented NNE and NNW for the Pliocene and Quaternary, respectively, and the S shape of the Quaternary anticline axes, are in agreement with the 2.24˚/Myr to 3.9˚/Myr modeled clockwise rotation of the small tectonic blocks and with the paleomagnetic data. The convergence between Africa and Eurasia is absorbed along the Atlas Mountains at the upper crustal level, by means of thrusting above decollement systems, which are controlled by subdued transcurrent faults. The Tell Atlas of northwest Algeria, which has experienced numerous large earthquakes with respect to the other regions, is interpreted as a restraining bend that localizes the strain distribution along the plate boundary.

  18. The life cycle of continental rifts: Numerical models of plate tectonics and mantle convection.

    Science.gov (United States)

    Ulvrova, Martina; Brune, Sascha; Williams, Simon

    2017-04-01

    Plate tectonic processes and mantle convection form a self-organized system whose surface expression is characterized by repeated Wilson cycles. Conventional numerical models often capture only specific aspects of plate-mantle interaction, due to imposed lateral boundary conditions or simplified rheologies. Here we study continental rift evolution using a 2D spherical annulus geometry that does not require lateral boundary conditions. Instead, continental extension is driven self-consistently by slab pull, basal drag and trench suction forces. We use the numerical code StagYY to solve equations of conservation of mass, momentum and energy and transport of material properties. This code is capable of computing mantle convection with self-consistently generated Earth-like plate tectonics using a pseudo-plastic rheology. Our models involve an incompressible mantle under the Boussinesq approximation with internal heat sources and basal heating. Due to the 2D setup, our models allow for a comparably high resolution of 10 km at the mantle surface and 15 km at the core mantle boundary. Viscosity variations range over 7 orders of magnitude. We find that the causes for rift initiation are often related to subduction dynamics. Some rifts initiate due to increasing slab pull, others because of developing trench suction force, for instance by closure of an intra-oceanic back-arc basin. In agreement with natural settings, our models reproduce rifts forming in both young and old collision zones. Our experiments show that rift dynamics follow a characteristic evolution, which is independent of the specific setting: (1) continental rifts initiate during tens of million of years at low extension rates (few millimetres per year) (2) the extension velocity increases during less than 10 million years up to several tens of millimetres per year. This speed-up takes place before lithospheric break-up and affects the structural architecture of rifted margins. (3) high divergence rates

  19. Feeling and Understanding Plate Tectonics - How can We attract Museum Visitors Attention?

    Science.gov (United States)

    Simon, Gilla; Apel, Michael

    2017-04-01

    Earthquakes, volcano eruptions and other natural hazards are commonly paid attention to, if news about disastrous events reach us. The mission of an Earth Science or Natural History Museum, however, goes beyond explaining the causes of natural disasters, but should also present science history and cutting edge research. Since dealing with a subject, especially with one, which seems to be in the abstract, is more effective, we realised two new projects where our visitors can feel and understand plate tectonics in a more exciting way. In 2015 we installed an earthquake simulator in our permanent exhibition to allow our visitors the physical experience of an earthquake. Because of static restrictions the simulator is housed in a container outside the building where it can be visited as a booked program upon prior reservation or by joining public tours on Sundays and special occasions. The simulation of six real earthquakes in two spatial directions is accompanied by a movie presenting facts about the earthquake itself (e.g. location, magnitude, damage and victims), but also general information about plate tectonics. This standard program takes about 20 minutes. During an educational program, however, not only the simulator is visited, but also the permanent exhibition, where the guide can focus on different aspects and then might choose specific earthquakes and information blocs in the simulator. In addition workshops with experiments are offered for school classes and other groups. This allows us to offer an individual program fitting to the visitor group. In 2016 we converted an old movie room to a state of the art media room. In cooperation with Media Informatics students we developed a quiz for three different levels and various themes like earthquakes, volcanoes, history and plate tectonics in general. Starting the quiz, a virtual earthquake destroys a building which will be reconstructed if the participants answer multiple choice questions correctly. Though, the

  20. HYBRID ACCRETIONARY/COLLISIONAL MECHANISM OF PALEOZOIC ASIAN CONTINENTAL GROWTH: NEW PLATE TECTONIC PERSPECTIVE

    Directory of Open Access Journals (Sweden)

    Karel Schulmann

    2017-01-01

    Full Text Available Continental crust is formed above subduction zones by well-known process of “juvenile crust growth”. This new crust is in modern Earth assembled into continents by two ways: (i short-lived collisions of continental blocks with the Laurussian or later Eurasian continent along the “Alpine Himalayan collisional/interior orogens” in the heart of the Pangean continental plates realm; and (ii long lived lateral accretion of ocean-floor fragments along “circum-Pacific accretionary/peripheral orogens” at the border of the PaleoPacific and modern Pacific oceanic plate.

  1. Opening of the Aden Gulf Ridge Derived from GPS Constraints and Plate Tectonic Models

    Science.gov (United States)

    Fernandes, R. M.; Rolandone, F.; Leroy, S.; Alothman, A.; Al-Aydrus, A.; Khalil, H.; Ahmed, A.; Khanbari, K.; Bos, M. S.; Nicolon, P.; Heydel, L.

    2012-12-01

    The Aden Gulf Ridge forms, together with the Red Sea and the Ethiopian Rift, the only emerged RRR-type (Ridge/Ridge/Ridge) triple junction in the globe: the Afar Triple Junction. The Aden Gulf Ridge defines the boundary between two major tectonic blocks: Arabia and Somalia, being Nubia the third unit in the triple junction (bordering Arabia along the Red Sea and Somalia along the Ethiopian Rift). Although the extensional behaviour of these structures are well known, the present-day magnitudes of their opening rates are still under evaluation, in particular for the opening rate between the Arabia and Somalia plates. This work uses GPS observations acquired in campaign and continuous mode in order to better constrain the opening rates of the three plate boundaries. For the Nubia-Arabia and Nubia-Somalia boundary plates, we use solely the velocity predictions given by our computed angular velocity models using the available continuous stations in Nubia, Somalia and Arabia. The available data set is augmented here with several stations in Saudi Arabia, which allow us to better constrain the angular velocity for the stable part of the Arabia plate. We estimate the angular velocity model with respect to ITRF2008 (the latest realization of the International Terrestrial Reference System) using the value of 2.5 years (although most of the stations have already a significantly longer time-series) as threshold data span for the processed time-series. Temporal correlations are used to properly estimate the uncertainty of the time-series and derived angular velocity model. In addition, to study the near-field in the Aden Gulf, data acquired in denser campaign networks in Yemen and Oman are used to also directly compute the extension rate in the Red Sea. We show that most of the Arabian Peninsula is stable (within the uncertainties) but the southwest part (Yemen) is influenced by the proximity with the Afar Triple Junction.

  2. Supercontinents, mantle dynamics and plate tectonics: A perspective based on conceptual vs. numerical models

    Science.gov (United States)

    Yoshida, Masaki; Santosh, M.

    2011-03-01

    The periodic assembly and dispersal of supercontinents through the history of the Earth had considerable impact on mantle dynamics and surface processes. Here we synthesize some of the conceptual models on supercontinent amalgamation and disruption and combine it with recent information from numerical studies to provide a unified approach in understanding Wilson Cycle and supercontinent cycle. Plate tectonic models predict that superdownwelling along multiple subduction zones might provide an effective mechanism to pull together dispersed continental fragments into a closely packed assembly. The recycled subducted material that accumulates at the mantle transition zone and sinks down into the core-mantle boundary (CMB) provides the potential fuel for the generation of plumes and superplumes which ultimately fragment the supercontinent. Geological evidence related to the disruption of two major supercontinents (Columbia and Gondwana) attest to the involvement of plumes. The re-assembly of dispersed continental fragments after the breakup of a supercontinent occurs through complex processes involving 'introversion', 'extroversion' or a combination of both, with the closure of the intervening ocean occurring through Pacific-type or Atlantic-type processes. The timescales of the assembly and dispersion of supercontinents have varied through the Earth history, and appear to be closely linked with the processes and duration of superplume genesis. The widely held view that the volume of continental crust has increased over time has been challenged in recent works and current models propose that plate tectonics creates and destroys Earth's continental crust with more crust being destroyed than created. The creation-destruction balance changes over a supercontinent cycle, with a higher crustal growth through magmatic influx during supercontinent break-up as compared to the tectonic erosion and sediment-trapped subduction in convergent margins associated with supercontinent

  3. Time variability in Cenozoic reconstructions of mantle heat flow: plate tectonic cycles and implications for Earth's thermal evolution.

    Science.gov (United States)

    Loyd, S J; Becker, T W; Conrad, C P; Lithgow-Bertelloni, C; Corsetti, F A

    2007-09-04

    The thermal evolution of Earth is governed by the rate of secular cooling and the amount of radiogenic heating. If mantle heat sources are known, surface heat flow at different times may be used to deduce the efficiency of convective cooling and ultimately the temporal character of plate tectonics. We estimate global heat flow from 65 Ma to the present using seafloor age reconstructions and a modified half-space cooling model, and we find that heat flow has decreased by approximately 0.15% every million years during the Cenozoic. By examining geometric trends in plate reconstructions since 120 Ma, we show that the reduction in heat flow is due to a decrease in the area of ridge-proximal oceanic crust. Even accounting for uncertainties in plate reconstructions, the rate of heat flow decrease is an order of magnitude faster than estimates based on smooth, parameterized cooling models. This implies that heat flow experiences short-term fluctuations associated with plate tectonic cyclicity. Continental separation does not appear to directly control convective wavelengths, but rather indirectly affects how oceanic plate systems adjust to accommodate global heat transport. Given that today's heat flow may be unusually low, secular cooling rates estimated from present-day values will tend to underestimate the average cooling rate. Thus, a mechanism that causes less efficient tectonic heat transport at higher temperatures may be required to prevent an unreasonably hot mantle in the recent past.

  4. Geodynamics of kimberlites on a cooling Earth: Clues to plate tectonic evolution and deep volatile cycles

    Science.gov (United States)

    Tappe, Sebastian; Smart, Katie; Torsvik, Trond; Massuyeau, Malcolm; de Wit, Mike

    2018-02-01

    Kimberlite magmatism has occurred in cratonic regions on every continent. The global age distribution suggests that this form of mantle melting has been more prominent after 1.2 Ga, and notably between 250-50 Ma, than during early Earth history before 2 Ga (i.e., the Paleoproterozoic and Archean). Although preservation bias has been discussed as a possible reason for the skewed kimberlite age distribution, new treatment of an updated global database suggests that the apparent secular evolution of kimberlite and related CO2-rich ultramafic magmatism is genuine and probably coupled to lowering temperatures of Earth's upper mantle through time. Incipient melting near the CO2- and H2O-bearing peridotite solidus at >200 km depth (1100-1400 °C) is the petrologically most feasible process that can produce high-MgO carbonated silicate melts with enriched trace element concentrations akin to kimberlites. These conditions occur within the convecting asthenospheric mantle directly beneath thick continental lithosphere. In this transient upper mantle source region, variable CHO volatile mixtures control melting of peridotite in the absence of heat anomalies so that low-degree carbonated silicate melts may be permanently present at ambient mantle temperatures below 1400 °C. However, extraction of low-volume melts to Earth's surface requires tectonic triggers. Abrupt changes in the speed and direction of plate motions, such as typified by the dynamics of supercontinent cycles, can be effective in the creation of lithospheric pathways aiding kimberlite magma ascent. Provided that CO2- and H2O-fluxed deep cratonic keels, which formed parts of larger drifting tectonic plates, existed by 3 Ga or even before, kimberlite volcanism could have been frequent during the Archean. However, we argue that frequent kimberlite magmatism had to await establishment of an incipient melting regime beneath the maturing continents, which only became significant after secular mantle cooling to below

  5. Miocene uplift of the NE Greenland margin linked to plate tectonics: Seismic evidence from the Greenland Fracture Zone, NE Atlantic

    DEFF Research Database (Denmark)

    Døssing Andreasen, Arne; Japsen, Peter; Watts, Anthony B.

    2016-01-01

    Tectonic models predict that, following breakup, rift margins undergo only decaying thermal subsidence during their post-rift evolution. However, post-breakup stratigraphy beneath the NE Atlantic shelves shows evidence of regional-scale unconformities, commonly cited as outer margin responses to ...... by plate tectonic forces, induced perhaps by a change in the Iceland plume (a hot pulse) and/or by changes in intra-plate stresses related to global tectonics.......Tectonic models predict that, following breakup, rift margins undergo only decaying thermal subsidence during their post-rift evolution. However, post-breakup stratigraphy beneath the NE Atlantic shelves shows evidence of regional-scale unconformities, commonly cited as outer margin responses...... backstripping. We explain the thermo-mechanical coupling and the deposition of contourites by the formation of a continuous plate boundary along the Mohns and Knipovich ridges, leading to an accelerated widening of the Fram Strait. We demonstrate that the IMU event is linked to onset of uplift and massive shelf...

  6. Shear-wave splitting beneath western United States in relation to plate tectonics

    Science.gov (United States)

    Özalaybey, Serdar; Savage, Martha K.

    1995-09-01

    Andreas fault. Stations located over the young subducting Gorda plate mark a change in the fast direction to nearly NE-SW. This direction aligns well with the maximum compressive stress direction in the overlying North American plate and the NE-SW directed internal shearing of the Gorda plate. The anisotropic thicknesses calculated from delay times suggest roughly double that expected for purely lithospheric contributions. This implies that the anisotropic thickness may include some of the asthenosphere. Alternatively, using a higher anisotropy of 8% can bring thicknesses in line with other measures of lithospheric thicknesses. The correspondence between the fast directions and the present plate tectonic deformations suggest that mapping upper mantle deformation through seismic anisotropy is a viable method, and that asthenospheric flow may be a significant contributor to seismic anisotropy.

  7. Large-Scale Present-Day Plate Boundary Deformations in the Eastern Hemisphere Determined from VLBI Data: Implications for Plate Tectonics and Indian Ocean Growth

    Science.gov (United States)

    Akilan, A.; Abdul Azeez, K. K.; Schuh, H.; Yuvraaj, N.

    2015-10-01

    The dynamics of the planet Earth are manifestations of diverse plate tectonic processes which have been occurring since the Archean period of the Earth's evolution and continue to deform the plate boundaries. Very long baseline interferometry (VLBI) is an efficient space geodetic method that enables precise measurement of plate motion and associated deformations. We analyze here VLBI measurements made during a period of approximately three decades at five locations on the Eastern hemisphere of the globe, which are geographically distributed over five continents (plates) around the Indian Ocean. Computed rate of change of baseline length show the deformation pattern and its rate at the boundaries between the major tectonic plates constituting the Eastern hemisphere of the Earth. The African (Nubian) and Antarctic plates are moving apart at 13.5 mm/year, which is mostly attributed to spreading of the South West Indian Ridge. Similarly, spreading of 59.0 mm/year is observed for the South East Indian Ridge that separates the Antarctic and Australian plates. Shortening at the rate of 3.9 mm/year is estimated across the subduction boundary between Africa (Nubia) and Eurasia. Similar convergence is evident between the Australian and Sunda blocks (of the Eurasian plate). The associated deformation of -54.8 mm/year seems to be chiefly accommodated along the Banda arc system, where the Australian plate is subducting under the Sunda block. VLBI sites within the Eurasian plate, Wettzell in Germany, and Seshan on the South China block, are moving apart at 3.6 mm/year. This relative motion between locations on the same plate is interpreted as a result of the deformation process along a large strike-slip fault, which is identified as the Western boundary of the South China block. Expansion of the Indian Ocean, at +91.5 m2/year, is also estimated from the rate of deformation estimated within the five baselines studied here. From the Hurst exponent values, which are indicators of

  8. From Dearth to El Dorado: Andean Nature, Plate Tectonics, and the Ontologies of Ecuadorian Resource Wealth

    Directory of Open Access Journals (Sweden)

    David Kneas

    2018-03-01

    Full Text Available Since the early 1990s, the Ecuadorian government has pledged to convert the nation into a “mining country” of global standing. Contemporary claims of mineral wealth, however, stand in stark contrast to previous assessments. Indeed, through much of the 20th century, geologists described Ecuador as a country of mineral dearth. Exploring the process through which Ecuador seemingly transitioned from a nation of resource scarcity to one of mineral plenty, I demonstrate how assessments of Ecuador’s resource potential relate to ideas of Andean nature. Promoters of resource abundance have emphasized Andean uniformity and equivalence—the notion that Ecuador’s mineral wealth is inevitable by virtue of the resource richness of its Andean neighbors. Geologists who have questioned Ecuador’s mineral content, on the other hand, have emphasized Andean heterogeneity. In the recent promotion of Ecuador’s resource potential, notions of Andean uniformity have been bolstered by models of subsoil copper that emerged in the in 1970s in the context of plate-tectonic theory. In highlighting the linkage between ideas of Andean nature and appraisals of Ecuadorian resource potential since the late 19th century, I outline the dialectics between nature and natural resources that underpin processes of resource becoming.

  9. Seismic potential of weak, near-surface faults revealed at plate tectonic slip rates.

    Science.gov (United States)

    Ikari, Matt J; Kopf, Achim J

    2017-11-01

    The near-surface areas of major faults commonly contain weak, phyllosilicate minerals, which, based on laboratory friction measurements, are assumed to creep stably. However, it is now known that shallow faults can experience tens of meters of earthquake slip and also host slow and transient slip events. Laboratory experiments are generally performed at least two orders of magnitude faster than plate tectonic speeds, which are the natural driving conditions for major faults; the absence of experimental data for natural driving rates represents a critical knowledge gap. We use laboratory friction experiments on natural fault zone samples at driving rates of centimeters per year to demonstrate that there is abundant evidence of unstable slip behavior that was not previously predicted. Specifically, weak clay-rich fault samples generate slow slip events (SSEs) and have frictional properties favorable for earthquake rupture. Our work explains growing field observations of shallow SSE and surface-breaking earthquake slip, and predicts that such phenomena should be more widely expected.

  10. Whole-mantle convection with tectonic plates preserves long-term global patterns of upper mantle geochemistry.

    Science.gov (United States)

    Barry, T L; Davies, J H; Wolstencroft, M; Millar, I L; Zhao, Z; Jian, P; Safonova, I; Price, M

    2017-05-12

    The evolution of the planetary interior during plate tectonics is controlled by slow convection within the mantle. Global-scale geochemical differences across the upper mantle are known, but how they are preserved during convection has not been adequately explained. We demonstrate that the geographic patterns of chemical variations around the Earth's mantle endure as a direct result of whole-mantle convection within largely isolated cells defined by subducting plates. New 3D spherical numerical models embedded with the latest geological paleo-tectonic reconstructions and ground-truthed with new Hf-Nd isotope data, suggest that uppermost mantle at one location (e.g. under Indian Ocean) circulates down to the core-mantle boundary (CMB), but returns within ≥100 Myrs via large-scale convection to its approximate starting location. Modelled tracers pool at the CMB but do not disperse ubiquitously around it. Similarly, mantle beneath the Pacific does not spread to surrounding regions of the planet. The models fit global patterns of isotope data and may explain features such as the DUPAL anomaly and long-standing differences between Indian and Pacific Ocean crust. Indeed, the geochemical data suggests this mode of convection could have influenced the evolution of mantle composition since 550 Ma and potentially since the onset of plate tectonics.

  11. A planet in transition: The onset of plate tectonics on Earth between 3 and 2 Ga?

    Directory of Open Access Journals (Sweden)

    Kent C. Condie

    2018-01-01

    Full Text Available Many geological and geochemical changes are recorded on Earth between 3 and 2 Ga. Among the more important of these are the following: (1 increasing proportion of basalts with “arc-like” mantle sources; (2 an increasing abundance of basalts derived from enriched (EM and depleted (DM mantle sources; (3 onset of a Great Thermal Divergence in the mantle; (4 a decrease in degree of melting of the mantle; (5 beginning of large lateral plate motions; (6 appearance of eclogite inclusions in diamonds; (7 appearance and rapid increase in frequency of collisional orogens; (8 rapid increase in the production rate of continental crust as recorded by zircon age peaks; (9 appearance of ophiolites in the geologic record, and (10 appearance of global LIP (large igneous province events some of which correlate with global zircon age peaks. All of these changes may be tied directly or indirectly to cooling of Earth's mantle and corresponding changes in convective style and the strength of the lithosphere, and they may record the gradual onset and propagation of plate tectonics around the planet. To further understand the changes that occurred between 3 and 2 Ga, it is necessary to compare rocks, rock associations, tectonics and geochemistry during and between zircon age peaks. Geochemistry of peak and inter-peak basalts and TTGs needs to be evaluated in terms of geodynamic models that predict the existence of an episodic thermal regime between stagnant-lid and plate tectonic regimes in early planetary evolution.

  12. Punctuated Neogene tectonics and stratigraphy of the African-Iberian plate-boundary zone: concurrent development of Betic-Rif basins (southern Spain, northern Morocco)

    NARCIS (Netherlands)

    Sissingh, W.

    2008-01-01

    This paper integrates the sequence stratigraphic and tectonic data related to the Neogene geodynamic and palaeogeographic development of the African-Iberian plate boundary zone between Spain and Morocco. Though the dating of individual tectonostratigraphic sequences and their delimiting sequence

  13. Seismic tomographic constraints on plate-tectonic reconstructions of Nazca subduction under South America since late Cretaceous (˜80 Ma)

    Science.gov (United States)

    Chen, Y. W.; Wu, J.; Suppe, J.

    2017-12-01

    Global seismic tomography has provided new and increasingly higher resolution constraints on subducted lithospheric remnants in terms of their position, depth, and volumes. In this study we aim to link tomographic slab anomalies in the mantle under South America to Andean geology using methods to unfold (i.e. structurally restore) slabs back to earth surface and input them to globally consistent plate reconstructions (Wu et al., 2016). The Andean margin of South America has long been interpreted as a classic example of a continuous subduction system since early Jurassic or later. However, significant gaps in Andean plate tectonic reconstructions exist due to missing or incomplete geology from extensive Nazca-South America plate convergence (i.e. >5000 km since 80 Ma). We mapped and unfolded the Nazca slab from global seismic tomography to produce a quantitative plate reconstruction of the Andes back to the late Cretaceous 80 Ma. Our plate model predicts the latest phase of Nazca subduction began in the late Cretaceous subduction after a 100 to 80 Ma plate reorganization, which is supported by Andean geology that indicates a margin-wide compressional event at the mid-late Cretaceous (Tunik et al., 2010). Our Andean plate tectonic reconstructions predict the Andean margin experienced periods of strike-slip/transtensional and even divergent plate tectonics between 80 to 55 Ma. This prediction is roughly consistent with the arc magmatism from northern Chile between 20 to 36°S that resumed at 80 Ma after a magmatic gap. Our model indicates the Andean margin only became fully convergent after 55 Ma. We provide additional constraints on pre-subduction Nazca plate paleogeography by extracting P-wave velocity perturbations within our mapped slab surfaces following Wu et al. (2016). We identified localized slow anomalies within our mapped Nazca slab that apparently show the size and position of the subducted Nazca ridge, Carnegie ridge and the hypothesized Inca plateau

  14. SECULAR CHANGES IN RELATIONSHIPS BETWEEN PLATE-TECTONIC AND MANTLE-PLUME ENGENDERED PROCESSES DURING PRECAMBRIAN TIME

    Directory of Open Access Journals (Sweden)

    M. V. Mints

    2016-01-01

    Full Text Available Paradoxically, the lists of “proxies” of both plate- and plume-related settings are devoid of even a mention of the high-grade metamorphic rocks (granulite, amphibolite and high-temperature eclogite facies. However, the granulite-gneiss belts and areas which contain these rocks, have a regional distribution in both the Precambrian and the Phanerozoic records. The origin and evolution of the granulite-gneiss belts correspond to the activity of plumes expressed in vigorous heating of the continental crust; intraplate magmatism; formation of rift depressions filled with sediments, juvenile lavas, and pyroclastic flow deposits; and metamorphism of lower and middle crustal complexes under conditions of granulite and high-temperature amphibolite facies that spreads over the fill of rift depressions also. Granulite-gneiss complexes of the East European Craton form one of the main components of the large oval intracontinental tectonic terranes of regional or continental rank. Inclusion of the granulite-gneiss complexes from Eastern Europe, North and South America, Africa, India, China and Australia in discussion of the problem indicated in the title to this paper, suggests consideration of a significant change in existing views on the relations between the plate- and plume-tectonic processes in geological history, as well as in supercontinent assembly and decay. The East European and North American cratons are fragments of the long-lived supercontinent Lauroscandia. After its appearance at ~2.8 Ga, the crust of this supercontinent evolved under the influence of the sequence of powerful mantle plumes (superplumes up to ~0.85 Ga. During this time Lauroscandia was subjected to rifting, partial breakup and the following reconstruction of the continent. The processes of plate-tectonic type (rifting with the transition to spreading and closing of the short-lived ocean with subduction within Lauroscandia were controlled by the superplumes. Revision of the

  15. A harbinger of plate tectonics: a commentary on Bullard, Everett and Smith (1965) ?The fit of the continents around the Atlantic?

    OpenAIRE

    Dewey, John F.

    2015-01-01

    In the 1960s, geology was transformed by the paradigm of plate tectonics. The 1965 paper of Bullard, Everett and Smith was a linking transition between the theories of continental drift and plate tectonics. They showed, conclusively, that the continents around the Atlantic were once contiguous and that the Atlantic Ocean had grown at rates of a few centimetres per year since the Early Jurassic, about 160?Ma. They achieved fits of the continental margins at the 500 fathom line (approx. 900?m),...

  16. Global crustal movement and tectonic plate boundary deformation constrained by the ITRF2008

    Directory of Open Access Journals (Sweden)

    Zhu Ze

    2012-08-01

    Full Text Available On the basis of the newly released International Terrestrial Reference Frame(ITRF2008 by the International Earth Rotation Service (IERS, a new global plate model ITRF2008 plate for the major plates is established. This ITRF2008-derived model is analyzed in comparison with NNR-NUVEL1A model, which is mainly based on geological and geophysical data. The Eurasia and Pacific plates display obvious differences in terms of the velocity fields derived from the two plate motion models. Plate acceleration is also introduced to characterize the differences of the two velocity fields which obtained from ITRF2008 -plate and NNR-NUVEL1A models for major individual plates. The results show that the Africa, South America and Eurasia plates are undergoing acceleration, while the North America and Australia plates are in the state of deceleration motion.

  17. Generation of plate tectonics with two-phase grain-damage and pinning: Source-sink model and toroidal flow

    Science.gov (United States)

    Bercovici, David; Ricard, Yanick

    2013-03-01

    theory therefore readily satisfies key plate-tectonic metrics of localized toroidal motion and plate-boundary inheritance, and thus provides a predictive theory for the generation of plate tectonics on Earth and other planets.

  18. Archean greenstone-tonalite duality: Thermochemical mantle convection models or plate tectonics in the early Earth global dynamics?

    Science.gov (United States)

    Kerrich, Robert; Polat, Ali

    2006-03-01

    Mantle convection and plate tectonics are one system, because oceanic plates are cold upper thermal boundary layers of the convection cells. As a corollary, Phanerozoic-style of plate tectonics or more likely a different version of it (i.e. a larger number of slowly moving plates, or similar number of faster plates) is expected to have operated in the hotter, vigorously convecting early Earth. Despite the recent advances in understanding the origin of Archean greenstone-granitoid terranes, the question regarding the operation of plate tectonics in the early Earth remains still controversial. Numerical model outputs for the Archean Earth range from predominantly shallow to flat subduction between 4.0 and 2.5 Ga and well-established steep subduction since 2.5 Ga [Abbott, D., Drury, R., Smith, W.H.F., 1994. Flat to steep transition in subduction style. Geology 22, 937-940], to no plate tectonics but rather foundering of 1000 km sectors of basaltic crust, then "resurfaced" by upper asthenospheric mantle basaltic melts that generate the observed duality of basalts and tonalities [van Thienen, P., van den Berg, A.P., Vlaar, N.J., 2004a. Production and recycling of oceanic crust in the early earth. Tectonophysics 386, 41-65; van Thienen, P., Van den Berg, A.P., Vlaar, N.J., 2004b. On the formation of continental silicic melts in thermochemical mantle convection models: implications for early Earth. Tectonophysics 394, 111-124]. These model outputs can be tested against the geological record. Greenstone belt volcanics are composites of komatiite-basalt plateau sequences erupted from deep mantle plumes and bimodal basalt-dacite sequences having the geochemical signatures of convergent margins; i.e. horizontally imbricated plateau and island arc crust. Greenstone belts from 3.8 to 2.5 Ga include volcanic types reported from Cenozoic convergent margins including: boninites; arc picrites; and the association of adakites-Mg andesites- and Nb-enriched basalts. Archean cratons

  19. Widespread remagnetizations and a new view of Neogene tectonic rotations within the Australia-Pacific plate boundary zone, New Zealand

    Science.gov (United States)

    Rowan, Christopher J.; Roberts, Andrew P.

    2008-03-01

    Large, clockwise, vertical axis tectonic rotations of the Hikurangi margin, East Coast, New Zealand, have been inferred over both geological and contemporary timescales, from paleomagnetic and geodetic data, respectively. Previous interpretations of paleomagnetic data have laterally divided the margin into independently rotating domains; this is not a feature of the short-term velocity field, and it is also difficult to reconcile with the large-scale boundary forces driving the rotation. New paleomagnetic results, rigorously constrained by field tests, demonstrate that late diagenetic growth of the iron sulfide greigite has remagnetized up to 65% of sampled localities on the Hikurangi margin. When these remagnetizations are accounted for, similar rates, magnitudes, and timings of tectonic rotation can be inferred for the entire Hikurangi margin south of the Raukumara Peninsula in the last 7-10 Ma. Numerous large (50-80°) declination anomalies from magnetizations acquired in the late Miocene require much greater rates of rotation (8-14° Ma-1) than the presently observed rate of 3-4° Ma-1, which is only likely to be characteristic of the tectonic regime established since 1-2 Ma. These new results are consistent with both long- and short-term deformation on the Hikurangi margin being driven by realignment of the subducting Pacific plate, with collision of the Hikurangi Plateau in the late Miocene potentially being key to both the initiation of tectonic rotations and the widespread remagnetization of Neogene sediments. However, accommodating faster, more coherent rotation of the Hikurangi margin in Neogene reconstructions of the New Zealand plate boundary region, particularly in the late Miocene, remains a challenge.

  20. The Role of Plate Tectonic-Climate Coupling and Exposed Land Area in the Development of Habitable Climates on Rocky Planets

    Science.gov (United States)

    Foley, Bradford J.

    2015-10-01

    The long-term carbon cycle is vital for maintaining liquid water oceans on rocky planets due to the negative climate feedbacks involved in silicate weathering. Plate tectonics plays a crucial role in driving the long-term carbon cycle because it is responsible for CO2 degassing at ridges and arcs, the return of CO2 to the mantle through subduction, and supplying fresh, weatherable rock to the surface via uplift and orogeny. However, the presence of plate tectonics itself may depend on climate according to recent geodynamical studies showing that cool surface temperatures are important for maintaining vigorous plate tectonics. Using a simple carbon cycle model, I show that the negative climate feedbacks inherent in the long-term carbon cycle are uninhibited by climate's effect on plate tectonics. Furthermore, initial atmospheric CO2 conditions do not impact the final climate state reached when the carbon cycle comes to equilibrium, as long as liquid water is present and silicate weathering can occur. Thus an initially hot, CO2 rich atmosphere does not prevent the development of a temperate climate and plate tectonics on a planet. However, globally supply limited weathering does prevent the development of temperate climates on planets with small subaerial land areas and large total CO2 budgets because supply limited weathering lacks stabilizing climate feedbacks. Planets in the supply limited regime may become inhospitable for life and could experience significant water loss. Supply limited weathering is less likely on plate tectonic planets because plate tectonics promotes high erosion rates and thus a greater supply of bedrock to the surface.

  1. Tracking the evolution of mantle sources with incompatible element ratios in stagnant-lid and plate-tectonic planets

    Science.gov (United States)

    Condie, Kent C.; Shearer, Charles K.

    2017-09-01

    The distribution of high field strength incompatible element ratios Zr/Nb, Nb/Th, Th/Yb and Nb/Yb in terrestrial oceanic basalts prior to 2.7 Ga suggests the absence or near-absence of an enriched mantle reservoir. Instead, most oceanic basalts reflect a variably depleted mantle source similar in composition to primitive mantle. In contrast, basalts from hydrated mantle sources (like those associated with subduction) exist from 4 Ga onwards. The gradual appearance of enriched mantle between 2 and 3 Ga may reflect the onset and propagation of plate tectonics around the globe. Prior to 3 Ga, Earth may have been in a stagnant-lid regime with most basaltic magmas coming from a rather uniform, variably depleted mantle source or from a non-subduction hydrated mantle source. It was not until the extraction of continental crust and accompanying propagation of plate tectonics that ;modern type; enriched and depleted mantle reservoirs developed. Consistent with the absence of plate tectonics on the Moon is the near absence of basalts derived from depleted (DM) and enriched (EM) mantle reservoirs as defined by the four incompatible element ratios of this study. An exception are Apollo 17 basalts, which may come from a mixed source with a composition similar to primitive mantle as one end member and a high-Nb component as the other end member. With exception of Th, which requires selective enrichment in at least parts of the martian mantle, most martian meteorites can be derived from sources similar to terrestrial primitive mantle or by mixing of enriched and depleted mantle end members produced during magma ocean crystallization. Earth, Mars and the Moon exhibit three very different planetary evolution paths. The mantle source regions for Mars and the Moon are ancient and have HFS element signatures of magma ocean crystallization well-preserved, and differences in these signatures reflect magma ocean crystallization under two distinct pressure regimes. In contrast, plate

  2. Evidence of a plate-wide tectonic pressure pulse provided by extensometric monitoring in the Balkan Mountains (Bulgaria)

    Czech Academy of Sciences Publication Activity Database

    Briestenský, Miloš; Rowberry, Matthew David; Stemberk, Josef; Stefanov, P.; Vozár, J.; Šebela, S.; Petro, L.; Bella, P.; Gaal, L.; Ormukov, Ch.

    2015-01-01

    Roč. 66, č. 5 (2015), s. 427-438 ISSN 1335-0552 R&D Projects: GA MŠk LM2010008; GA MŠk OC 625.10; GA ČR GA205/05/2770; GA ČR GA205/06/1828; GA ČR GA205/09/2024 Institutional support: RVO:67985891 Keywords : Eurasian Plate * Balkan Peninsula * active tectonics research * aseismic transient deformations * slow-slip phenomena Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.523, year: 2015 http://www.geologicacarpathica.com/browse-journal/volumes/66-5/article-780

  3. History of internal fixation with plates (part 2): new developments after World War II; compressing plates and locked plates.

    Science.gov (United States)

    Hernigou, Philippe; Pariat, Jacques

    2017-07-01

    The first techniques of operative fracture with plates were developed in the 19th century. In fact, at the beginning these methods consisted of an open reduction of the fracture usually followed by a very unstable fixation. As a consequence, the fracture had to be opened with a real risk of (sometimes lethal) infection, and due to unstable fixation, protection with a cast was often necessary. During the period between World Wars I and II, plates for fracture fixation developed with great variety. It became increasingly recognised that, because a fracture of a long bone normally heals with minimal resorption at the bone ends, this may result in slight shortening and collapse, so a very rigid plate might prevent such collapse. However, as a consequence, delayed healing was observed unless the patient was lucky enough to have the plate break. One way of dealing with this was to use a slotted plate in which the screws could move axially, but the really important advance was recognition of the role of compression. After the first description of compression by Danis with a "coapteur", Bagby and Müller with the AO improved the technique of compression. The classic dynamic compression plates from the 1970s were the key to a very rigid fixation, leading to primary bone healing. Nevertheless, the use of strong plates resulted in delayed union and the osteoporosis, cancellous bone, comminution, and/or pathological bone resulted in some failures due to insufficient stability. Finally, new devices represented by locking plates increased the stability, contributing to the principles of a more biological osteosynthesis while giving enough stability to allow immediate full weight bearing in some patients.

  4. Segmentation of the eastern North Greenland oblique-shear margin – regional plate tectonic implications

    DEFF Research Database (Denmark)

    Andreasen, Arne Døssing; Stemmerik, Lars; Dahl-Jensen, T.

    2010-01-01

    a highly complex, Paleozoic–early Cenozoic pre-opening setting. However, due to extreme ice conditions, very little is known about the offshore areas seawards of – and between – the peninsulas. Consequently, prevailing structural-tectonic models of the margin tend to be significantly oversimplified...... anticipated. In particular, we interpret strong margin segmentation along N/NE-striking fault structures. The structures are likely to have formed by Late Mesozoic–early Cenozoic strike-slip tectonics and have continued to be active during the late Cenozoic. A more than 8 km deep sedimentary basin...

  5. Plate tectonic reconstruction of India and Madagascar closing through the Mascarene Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Shuhail, M.

    of India and the adjacent ocean basins were evolved by rifting and subsequent Basin, and then from Seychelles, creating the conjugate Arabian and Eastern Somali basins. Since the hydrocarbon occurrence in passive continental margins is closely... with its conjugate region of Madagascar has been directly addressed or indirectly depicted in a number of earlier studies. However the proposed relative Indian Ocean is associated with Indian Plate (IND), African Plate (AFR) and Antarctic Plate (ANT...

  6. 3-D thermo-mechanical laboratory modeling of plate-tectonics: modeling scheme, technique and first experiments

    Directory of Open Access Journals (Sweden)

    D. Boutelier

    2011-05-01

    Full Text Available We present an experimental apparatus for 3-D thermo-mechanical analogue modeling of plate tectonic processes such as oceanic and continental subductions, arc-continent or continental collisions. The model lithosphere, made of temperature-sensitive elasto-plastic analogue materials with strain softening, is submitted to a constant temperature gradient causing a strength reduction with depth in each layer. The surface temperature is imposed using infrared emitters, which allows maintaining an unobstructed view of the model surface and the use of a high resolution optical strain monitoring technique (Particle Imaging Velocimetry. Subduction experiments illustrate how the stress conditions on the interplate zone can be estimated using a force sensor attached to the back of the upper plate and adjusted via the density and strength of the subducting lithosphere or the lubrication of the plate boundary. The first experimental results reveal the potential of the experimental set-up to investigate the three-dimensional solid-mechanics interactions of lithospheric plates in multiple natural situations.

  7. Discovering Plate Boundaries, A Data-Rich Inquiry-Based Classroom Exercise for Teaching Plate Tectonic Boundary Processes

    Science.gov (United States)

    Sawyer, D. S.

    2005-12-01

    Discovering Plate Boundaries is a classroom exercise based on 4 world maps containing earthquake, volcano, topography, and seafloor age data. A novel aspect of the exercise is the jigsaw manner in which student groups access the maps and use them to discover, classify, and describe plate boundary types. The exercise is based only on observation and description, which makes it useful at a wide variety of levels. We have used it successfully with middle school, high school, and college major and non-major earth science classes, as well as with pre-service and in-service teachers. The exercise takes three to four 50 minute class periods to complete and involves the students making presentations to one another in small groups and to the whole class. The students come away from the exercise with knowledge of the key features of each type of plate boundary and a sense of why each looks the way it does. While the materials are accessible on the web (http://terra.rice.edu/plateboundary/ and through http://www.dlese.org ), the actual exercise is not based on student access to the Web and is not dependent on classroom technology equipment.

  8. Philippine Sea and East Asian plate tectonics since 52 Ma constrained by new subducted slab reconstruction methods

    Science.gov (United States)

    Wu, Jonny; Suppe, John; Lu, Renqi; Kanda, Ravi

    2016-06-01

    We reconstructed Philippine Sea and East Asian plate tectonics since 52 Ma from 28 slabs mapped in 3-D from global tomography, with a subducted area of ~25% of present-day global oceanic lithosphere. Slab constraints include subducted parts of existing Pacific, Indian, and Philippine Sea oceans, plus wholly subducted proto-South China Sea and newly discovered "East Asian Sea." Mapped slabs were unfolded and restored to the Earth surface using three methodologies and input to globally consistent plate reconstructions. Important constraints include the following: (1) the Ryukyu slab is ~1000 km N-S, too short to account for ~20° Philippine Sea northward motion from paleolatitudes; (2) the Marianas-Pacific subduction zone was at its present location (±200 km) since 48 ± 10 Ma based on a >1000 km deep slab wall; (3) the 8000 × 2500 km East Asian Sea existed between the Pacific and Indian Oceans at 52 Ma based on lower mantle flat slabs; (4) the Caroline back-arc basin moved with the Pacific, based on the overlapping, coeval Caroline hot spot track. These new constraints allow two classes of Philippine Sea plate models, which we compared to paleomagnetic and geologic data. Our preferred model involves Philippine Sea nucleation above the Manus plume (0°/150°E) near the Pacific-East Asian Sea plate boundary. Large Philippine Sea westward motion and post-40 Ma maximum 80° clockwise rotation accompanied late Eocene-Oligocene collision with the Caroline/Pacific plate. The Philippine Sea moved northward post-25 Ma over the northern East Asian Sea, forming a northern Philippine Sea arc that collided with the SW Japan-Ryukyu margin in the Miocene (~20-14 Ma).

  9. On plate tectonics and the geologic evolution of southwestern North America

    Science.gov (United States)

    Ward, Peter L.

    1991-07-01

    Very rapid subduction of the Farallon plate under southwestern North America between 60 and 40 Ma was accompanied by a relatively low volume of magmatism throughout the southwestern United States and northern Mexico. Between 40 and 20 Ma, when subduction slowed significantly and in one area may have even stopped, magmatism became widespread and voluminous from Nevada and Utah to central Mexico. This correlation of rapid subduction with a relatively low volume of magmatism can be explained by the observation that subduction-related andesitic arc volcanism, often formed in a Laramide-style compressional regime, is relatively low volume compared to continental volcanism. The shallow roots of arc volcanic systems are clearly exposed in the porphyry copper deposits found in currently active arcs and common throughout southwestern North America between 60 and 50 Ma. By 43 Ma, worldwide plate motions changed, the Pacific plate began moving away from North America, and subduction of the Farallon plate slowed. By around 36 Ma, the easternmost part of the East Pacific Rise, which was located between the Pioneer and Murray fracture zones, approached the trench and the young, hot, buoyant lithosphere appears to have clogged part of the subduction zone. Uplift on land became widespread. Voluminous continental magmatism formed the Sierra Madre Occidental (SMO) of Mexico, one of the largest batholiths in the world, as well as volcanic centers now exposed in the San Juan Mountains of Colorado and the Rio Grande Rift of New Mexico. Vectors of motion of the Pacific plate relative to the North American plate determined by Stock and Molnar (1988) are consistent with formation of a transtensional environment along the plate boundary sufficient to create a 100- to 200-km-wide void just landward of the old volcanic arc. While the SMO batholith was forming within this void, the Monterey and Arguello microplates just offshore to the west were broken off from the Farallon plate and rotated

  10. Origin of marginal basins of the NW Pacific and their plate tectonic reconstructions

    Science.gov (United States)

    Xu, Junyuan; Ben-Avraham, Zvi; Kelty, Tom; Yu, Ho-Shing

    2014-03-01

    Geometry of basins can indicate their tectonic origin whether they are small or large. The basins of Bohai Gulf, South China Sea, East China Sea, Japan Sea, Andaman Sea, Okhotsk Sea and Bering Sea have typical geometry of dextral pull-apart. The Java, Makassar, Celebes and Sulu Seas basins together with grabens in Borneo also comprise a local dextral, transform-margin type basin system similar to the central and southern parts of the Shanxi Basin in geometry. The overall configuration of the Philippine Sea resembles a typical sinistral transpressional "pop-up" structure. These marginal basins except the Philippine Sea basin generally have similar (or compatible) rift history in the Cenozoic, but there do be some differences in the rifting history between major basins or their sub-basins due to local differences in tectonic settings. Rifting kinematics of each of these marginal basins can be explained by dextral pull-apart or transtension. These marginal basins except the Philippine Sea basin constitute a gigantic linked, dextral pull-apart basin system.

  11. Rotational inertia of continents: A proposed link between polar wandering and plate tectonics

    Science.gov (United States)

    Kane, M.F.

    1972-01-01

    A mechanism is proposed whereby displacement between continents and the earth's pole of rotation (polar wandering) gives rise to latitudinal transport of continental plates (continental drift) because of their relatively greater rotational inertia. When extended to short-term polar wobble, the hypothesis predicts an energy change nearly equivalent to the seismic energy rate.

  12. Quantifying the net slab pull force as a driving mechanism for plate tectonics

    NARCIS (Netherlands)

    Schellart, W. P.

    2004-01-01

    It has remained unclear how much of the negative buoyancy force of the slab (FB) is used to pull the trailing plate at the surface into the mantle. Here I present three-dimensional laboratory experiments to quantify the net slab pull force (FNSP) with respect to FB during subduction. Results show

  13. Combining floating continents and a free surface in a 3D spherical mantle convection model with self-consistent plate tectonics

    Science.gov (United States)

    Rolf, T.; Crameri, F.; Tackley, P. J.

    2012-04-01

    The dynamics of the Earth's lithosphere and mantle are strongly influenced by its upper mechanical boundary condition. For instance, our previous work has shown that a necessity for the evolution of Earth-like, single-sided subduction is a free surface, which allows for vertical movement of the two converging plates, i.e. the development of surface topography [Crameri et al (2012), in press]. Single-sided subduction has an important effect on the evolution of self-consistent plate tectonics, e.g. by shaping subduction trenches. However, due to the usage of a homogeneous, i.e. purely oceanic, lithosphere these models tend to favour the rigid lid mode of plate tectonics for a realistic strength of the lithosphere, which is in contradiction to the present-day Earth. In contrast, our previous work with a pre-existing heterogeneous structure of the lithosphere has shown that the presence of continents floating at the top of the mantle may play an important role in the evolution of plate tectonics. Convective stresses may be focussed at the rheological boundary between continent and ocean, which facilitates the formation of plate boundaries and makes the Earth-like, mobile lid mode of plate tectonics easier to observe [Rolf & Tackley (2011)]. However, in these models subduction is single-sided when one oceanic and one continental plate converge, but double-sided in the case of two converging oceanic plates. Taking the previous findings as a motivation, we now combine both ingredients: the free surface and the heterogeneous lithosphere, in one self-consistent model. We approximate the free surface by using a "sticky air" layer [Schmeling et al, 2008; Crameri et al., submitted] and the continents by strong Archaean cratons, which can resist recycling on long timescales [Rolf & Tackley (2011)]. Such a model might produce single-sided subduction that is continuously evolving supported by the presence of continents. Performing global-scale self-consistent mantle convection

  14. Plate tectonics and the origin of the Juan Fernández Ridge: analysis of bathymetry and magnetic patterns

    Directory of Open Access Journals (Sweden)

    Cristián Rodrigo

    2014-10-01

    Full Text Available Juan Fernández Ridge (JFR is a cα. 800 km long alignment of seamounts and islands which is thought to be fed by a deep mantle plume. JFR includes the Friday and Domingo seamounts in the western active edge close to the active hotspot, and the O'Higgins Seamount and Guyot at the eastern limit just in front of the Chile-Perú trench. Recent bathymetric (Global Topography and magnetic (EMAG-2 datasets were interpreted both qualitatively and quantitatively by means of 3D inverse modeling and 2D direct modeling for geometry and susceptibility, together with an interpretation of the synthetic anomalies related to the classical hypothesis of deep seafloor spreading. Topographic and magnetic patterns are used to understand the tectonic evolution and origin of the JFR, especially in the western segment. Results show a continuous corridor with a base at ~3900 m depth formed by four groups of seamounts/islands with a number of summits. The deep ocean floor is ~22 to ~37 Myr old and is younger to the south of the Challenger Fracture Zone that runs in a SW-NE direction. The magnetic pattern of the western JFR segment, which is different than the eastern one, has no correlation with bathymetry and does not present a common polarity nor fit with magnetic models for isolated bodies. This superposition of magnetic patterns indicates a role of the faults/fractures of the Nazca Plate. Geological evidence supports the hypothesis of a fixed mantle plume for the origin of JFR but our data suggest that tectonic processes play a role, thus fueling the global controversy about these competing processes.

  15. Active tectonic deformation of the western Indian plate boundary: A case study from the Chaman Fault System

    Science.gov (United States)

    Crupa, Wanda E.; Khan, Shuhab D.; Huang, Jingqiu; Khan, Abdul S.; Kasi, Aimal

    2017-10-01

    Collision of the Eurasian and Indian plates has resulted in two spatially offset subduction zones, the Makran subduction zone to the south and the Himalayan convergent margin to the north. These zones are linked by a system of left-lateral strike-slip faults known as the Chaman Fault System, ∼1200 km, which spans along western Pakistan. Although this is one of the greatest strike-slip faults, yet temporal and spatial variation in displacement has not been adequately defined along this fault system. This study conducted geomorphic and geodetic investigations along the Chaman Fault in a search for evidence of spatial variations in motion. Four study areas were selected over the span of the Chaman Fault: (1) Tarnak-Rud area over the Tarnak-Rud valley, (2) Spinatizha area over the Spinatizha Mountain Range, (3) Nushki area over the Nushki basin, and (4) Kharan area over the northern tip of the Central Makran Mountains. Remote sensing data allowed for in depth mapping of different components and faults within the Kohjak group. Wind and water gap pairs along with offset rivers were identified using high-resolution imagery and digital-elevation models to show displacement for the four study areas. The mountain-front-sinuosity ratio, valley height-to-width-ratio, and the stream-length-gradient index were calculated and used to determine the relative tectonic activity of each area. These geomorphic indices suggest that the Kharan area is the most active and the Tarnak-Rud area is the least active. GPS data were processed into a stable Indian plate reference frame and analyzed. Fault parallel velocity versus fault normal distance yielded a ∼8-10 mm/yr displacement rate along the Chaman Fault just north of the Spinatizha area. InSAR data were also integrated to assess displacement rates along the fault system. Geodetic data support that ultra-slow earthquakes similar to those that strike along other major strike-slip faults, such as the San Andreas Fault System, are

  16. Collision tectonics

    Energy Technology Data Exchange (ETDEWEB)

    Coward, M.P.; Ries, A.C.

    1985-01-01

    The motions of lithospheric plates have produced most existing mountain ranges, but structures produced as a result of, and following the collision of continental plates need to be distinguished from those produced before by subduction. If subduction is normally only stopped when collision occurs, then most geologically ancient fold belts must be collisional, so it is essential to recognize and understand the effects of the collision process. This book consists of papers that review collision tectonics, covering tectonics, structure, geochemistry, paleomagnetism, metamorphism, and magmatism.

  17. Evidence of a plate-wide tectonic pressure pulse provided by extensometric monitoring in the Balkan Mountains (Bulgaria

    Directory of Open Access Journals (Sweden)

    Briestenský Miloš

    2015-10-01

    Full Text Available The EU-TecNet monitoring network uses customized three-dimensional extensometers to record transient deformations across individual faults. This paper presents the first results from two newly established monitoring points in the Balkan Mountains in Bulgaria. The data from Saeva Dupka, recorded across an EEN-WWS striking fault, show sinistral strike-slip along the fault and subsidence of the southern block. Much of the subsidence occurred around the time of the distal MW = 5.6 Pernik Earthquake. An important transient deformation event, which began in autumn 2012, was reflected by significant compression and following extension, across the monitored fault. The data from Bacho Kiro, recorded across a NE–SW striking fault, show sinistral strike-slip along the fault and subsidence of the north-western block. The same important deformation event was reflected by changes in the strike-slip, dip-slip, and horizontal opening/closing trends. These results have been compared to data from other monitoring points in the Western Carpathians, External Dinarides, and Tian Shan. Many of the sites show evidence of simultaneous displacement anomalies and this observation is interpreted as a reflection of the plate-wide propagation of a tectonic pressure pulse towards the end of 2012.

  18. A harbinger of plate tectonics: a commentary on Bullard, Everett and Smith (1965) 'The fit of the continents around the Atlantic'.

    Science.gov (United States)

    Dewey, John F

    2015-04-13

    In the 1960s, geology was transformed by the paradigm of plate tectonics. The 1965 paper of Bullard, Everett and Smith was a linking transition between the theories of continental drift and plate tectonics. They showed, conclusively, that the continents around the Atlantic were once contiguous and that the Atlantic Ocean had grown at rates of a few centimetres per year since the Early Jurassic, about 160 Ma. They achieved fits of the continental margins at the 500 fathom line (approx. 900 m), not the shorelines, by minimizing misfits between conjugate margins and finding axes, poles and angles of rotation, using Euler's theorem, that defined the unique single finite difference rotation that carried congruent continents from contiguity to their present positions, recognizing that the real motion may have been more complex around a number of finite motion poles. Critically, they were concerned only with kinematic reality and were not restricted by considerations of the mechanism by which continents split and oceans grow. Many of the defining features of plate tectonics were explicit or implicit in their reconstructions, such as the torsional rigidity of continents, Euler's theorem, closure of the Tethyan ocean(s), major continental margin shear zones, the rapid rotation of small continental blocks (Iberia) around nearby poles, the consequent opening of small wedge-shaped oceans (Bay of Biscay), and misfit overlaps (deltas and volcanic piles) and underlaps (stretched continental edges). This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society.

  19. A harbinger of plate tectonics: a commentary on Bullard, Everett and Smith (1965) ‘The fit of the continents around the Atlantic’

    Science.gov (United States)

    Dewey, John F.

    2015-01-01

    In the 1960s, geology was transformed by the paradigm of plate tectonics. The 1965 paper of Bullard, Everett and Smith was a linking transition between the theories of continental drift and plate tectonics. They showed, conclusively, that the continents around the Atlantic were once contiguous and that the Atlantic Ocean had grown at rates of a few centimetres per year since the Early Jurassic, about 160 Ma. They achieved fits of the continental margins at the 500 fathom line (approx. 900 m), not the shorelines, by minimizing misfits between conjugate margins and finding axes, poles and angles of rotation, using Euler's theorem, that defined the unique single finite difference rotation that carried congruent continents from contiguity to their present positions, recognizing that the real motion may have been more complex around a number of finite motion poles. Critically, they were concerned only with kinematic reality and were not restricted by considerations of the mechanism by which continents split and oceans grow. Many of the defining features of plate tectonics were explicit or implicit in their reconstructions, such as the torsional rigidity of continents, Euler's theorem, closure of the Tethyan ocean(s), major continental margin shear zones, the rapid rotation of small continental blocks (Iberia) around nearby poles, the consequent opening of small wedge-shaped oceans (Bay of Biscay), and misfit overlaps (deltas and volcanic piles) and underlaps (stretched continental edges). This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society. PMID:25750142

  20. Nonlinear morphoelastic plates II: Exodus to buckled states

    KAUST Repository

    McMahon, J.

    2011-05-11

    Morphoelasticity is the theory of growing elastic materials. The theory is based on the multiplicative decomposition of the deformation gradient and provides a formulation of the deformation and stresses induced by growth. Following a companion paper, a general theory of growing non-linear elastic Kirchhoff plate is described. First, a complete geometric description of incompatibility with simple examples is given. Second, the stability of growing Kirchhoff plates is analyzed. © SAGE Publications 2011.

  1. Dinosaur tectonics

    DEFF Research Database (Denmark)

    Graversen, Ole; Milàn, Jesper; B. Loope, David

    2007-01-01

    to crustal scale tectonics associated with plate tectonics and foreland fold-thrust belts. A structural analysis of the dinosaur tracks shows the timing and direction of the forces exercised on the substrate by the animal's foot during the stride. Based on the structural analysis, we establish a scenario......A dinosaur trackway in the Middle Jurassic eolian Entrada Sandstone of southern Utah, USA, exposes three undertracks that we have modeled as isolated tectonic regimes showing the development of fold-thrust ramp systems induced by the dinosaur's feet. The faulted and folded sequence is comparable...... for foot movements and weight distribution in the feet. During the end of the weight-bearing phase of the stride, the weight of the animal was transferred to the front of the digits, creating a rotated disc below the foot that was bounded by an extensional fault at the front and a thrust ramp toward...

  2. Plate flexure and volcanism: Late Cenozoic tectonics of the Tabar-Lihir-Tanga-Feni alkalic province, New Ireland Basin, Papua New Guinea

    Science.gov (United States)

    Lindley, I. D.

    2016-05-01

    Late Cenozoic Tabar-Lihir-Tanga-Feni (TLTF) alkaline volcanism, New Ireland Basin, PNG, is associated with extensional cracks along the crests of flexed ridges developed on the New Ireland Microplate (New name). The tectonic alignment of the TLTF volcanic arc is essentially perpendicular to the flexed ridges, suggesting that fractures parallel to the direction of maximum horizontal compression facilitated the rapid ascent of alkaline magmas from the mantle region, perhaps 60-70 km depth. The mainly Pliocene to Pleistocene volcanoes were localized at the intersection of ridge-parallel Kabang structures and arc-parallel Niffin structures, suggesting that the Kabang-Niffin structural intersections underlying each of the TLTF island groups provided a well developed, clustered network of open conduits which tapped the mantle source region. Periodic post-Miocene locking and unlocking along the strike-slip Kilinailau Fault (New name) are thought to have functioned as a valve, turning on (Pliocene) and then turning off (Pleistocene) volcanic activity, respectively. Partial locking of the Kilinailau Fault during the Pliocene resulted in the accumulation of intraplate stresses within the New Ireland Microplate, and caused plate flexure and ridge development, plate-cracking along ridge crests and the development of arc-parallel regional fractures parallel to the direction of maximum compression. Unlocking of the Kilinailau Fault in the Pleistocene resulted in the release of intraplate stresses in the New Ireland Microplate and a cessation of volcanic activity across most of the TLTF arc. The style and scale of plate flexure and cracking, accompanied by within-plate alkaline volcanism from equally spaced ridge-top eruptive centers confined to a narrow, linear volcanic arc are unknown from any other tectonic province.

  3. Transpressional Tectonics across the N. American-Caribbean Plate Boundary: Preliminary Results of a Multichannel Seismic Survey of Lake Azuei, Haiti.

    Science.gov (United States)

    Hearn, C. K.; Cormier, M. H.; Sloan, H.; Wattrus, N. J.; Boisson, D.; Brown, B.; Guerrier, K.; King, J. W.; Knotts, P.; Momplaisir, R.; Sorlien, C. C.; Stempel, R.; Symithe, S. J.; Ulysse, S. M. J.

    2017-12-01

    On January 12, 2010, a Mw 7.0 earthquake struck Haiti, killing over 200,000 people and devastating the Capital city of Port-au-Prince and the surrounding regions. It ruptured a previously unknown blind-thrust fault that abuts the Enriquillo Plantain Garden Fault (EPGF), one of two transform faults that define the North American-Caribbean plate boundary. That earthquake highlighted how transpression across this complex boundary is accommodated by slip partitioning into strike-slip and compressional structures. Because the seismic hazard is higher for a rupture on a reverse or oblique-slip fault than on a vertical strike-slip fault, the need to characterize the geometry of that fault system is clear. Lake Azuei overlies this plate boundary 60 km east of the 2010 epicenter. The lake's 23 km long axis trends NW-SE, parallel to the Haitian fold-and-thrust belt and oblique to the EPGF. This tectonic context makes it an ideal target for investigating the partitioning of plate motion between strike-slip and compressional structures. In January 2017, we acquired 222 km of multichannel seismic (MCS) profiles in the lake, largely concurrent with subbottom seismic (CHIRP) profiles. The MCS data were acquired using a high-frequency BubbleGun source and a 75 m-long, 24-channel streamer, achieving a 24 seismic fold with a penetration of 200 m below lakebed. With the goal of resolving tectonic structures in 3-D, survey lines were laid out in a grid with profiles spaced 1.2 km apart. Additional profiles were acquired at the SE end of the lake where most of the tectonic activity is presumably occurring. The co-located CHIRP and MCS profiles document the continuity of tectonic deformation between the surficial sediments and the deeper strata. Preliminary processing suggests that a SW-dipping blind thrust fault, expressed updip as a large monocline fold, may control the western edge of the lake. Gentle, young folds that protrude from the flat lakebed are also imaged with the CHIRP

  4. Venus: No Catastrophic Resurfacing, No Plate Tectonics, But a Rich Ancient History - Results from Global Ribbon Tessera Terrain Mapping

    Science.gov (United States)

    Hansen, V. L.; López, I.

    2008-03-01

    A global map of ribbon tessera terrain rtt shows: rtt covers ~18% of Venus; distinct rtt suites "defined by tectonic fabric" cover millions of km2, and show crosscutting relations, forming the basis for a global-scale (relative) ancient timescale.

  5. Geochemistry of subalkaline and alkaline extrusives from the Kermanshah ophiolite, Zagros Suture Zone, Western Iran: implications for Tethyan plate tectonics

    Science.gov (United States)

    Ghazi, A. Mohamad; Hassanipak, A. A.

    1999-06-01

    The Kermanshah ophiolite is a highly dismembered ophiolite complex that is located in western Iran and belongs to the Zagros orogenic system. The igneous rocks of this complex consist of both mantle and crustal suites and include peridotites (dunite and harzburgite), cumulate gabbros, diorites, and a volcanic sequence that exhibits a wide range in composition from subalkaline basalts to alkaline basalts to trachytes. The associated sedimentary rocks include a variety of Upper Triassic to Lower Cretaceous deep- and shallow-water sedimentary rocks (e.g., dolomite, limestone, and pelagic sediments, including umber). Also present are extensive units of radiolarian chert. The geochemical data clearly identifies some of the volcanic rocks to have formed from two distinct types of basaltic melts: (i) those of the subalkaline suite, which formed from an initial melt with a light rare earth elements (LREE) enriched signature and incompatible trace element patterns that suggest an island arc affinity; and (ii) those of the alkaline suite with LREE-enriched signature and incompatible trace element patterns that are virtually identical to typical oceanic island basalt (OIB) pattern. The data also suggests that the trachytes were derived from the alkaline source, with fractionation controlled by extensive removal of plagioclase and to a lesser extent clinopyroxene. The presence of compositionally diverse volcanics together with the occurrence of a variety of Triassic-Cretaceous sedimentary rocks and radiolarian chert indicate that the studied volcanic rocks from the Kermanshah ophiolite represent off-axis volcanic units that were formed in intraplate oceanic island and island arc environments in an oceanic basin. They were located on the eastern and northern flanks of one of the spreading centers of a ridge-transform fault system that connected Troodos to Oman prior to its subduction under the Eurasian plate.

  6. Misconceptions and Conceptual Changes Concerning Continental Drift and Plate Tectonics among Portuguese Students Aged 16-17.

    Science.gov (United States)

    Marques, Luis; Thompson, David

    1997-01-01

    This study investigates student misconceptions in the areas of continent, ocean, permanence of ocean basins, continental drift, Earth's magnetic field, and plates and plate motions. A teaching-learning model was designed based on a constructivist approach. Results show that students held a substantial number of misconceptions. (Author/DKM)

  7. Neutron detection with imaging plates Part II. Detector characteristics

    CERN Document Server

    Thoms, M

    1999-01-01

    On the basis of the physical processes described in Neutron detection with imaging plates - part I: image storage and readout [Nucl. Instr. and Meth. A 424 (1999) 26-33] detector characteristics, such as quantum efficiency, detective quantum efficiency, sensitivity to neutron- and gamma-radiation, readout time and dynamic range are predicted. It is estimated that quantum efficiencies and detective quantum efficiencies close to 100% can be reached making these kind of detectors interesting for a wide range of applications.

  8. Slab dip, surface tectonics: How and when do they change following an acceleration/slow down of the overriding plate?

    Science.gov (United States)

    Guillaume, Benjamin; Hertgen, Solenn; Martinod, Joseph; Cerpa, Nestor G.

    2018-02-01

    We present analogue models simulating the subduction of an oceanic lithosphere beneath an overriding plate advancing at variable rates. The convergence velocity is imposed by lateral boundary conditions in this experimental set. We analyze the geometry of the slab and the deformation of the overriding plate. Experiments confirm the strong correlation between the absolute velocity of the overriding plate on the one hand, the geometry of the subducting plate and the deformation of the overriding plate on the other hand. Following an instantaneous change in kinematic boundary conditions, the subduction system progressively shifts to a new steady-state regime. Models suggest that the adjustment time necessary to shift from the previous to the new equilibrium is independent of the imposed upper plate velocity. Transient stage lasts ∼ 12.5 ± 6 m.y. for the shallow slab dip (100-150-km depth), ∼ 29.2 ± 10 m.y. for the deeper slab dip (300-350-km depth), and ∼ 2.2 ± 2 m.y. for the upper plate deformation. The analysis of present-day subduction zones and their evolution through the last 20 m.y suggests an adjustment time of ∼15 m.y. for shallow slab dip and ∼20 m.y. for deep slab dip in Nature. Since only few subduction zones have shown a constant upper plate velocity over the last 15 m.y., it suggests that most of them are in a transient stage at present-day.

  9. DISCUSSION: When and How did Plate Tectonics Begin, What Came Before, and Why is this Controversy important for Understanding the Earth and Exoplanets?

    Science.gov (United States)

    Stern, R. J.; Gerya, T.; Sobolev, S. V.; Tackley, P.

    2015-12-01

    Because all 5 presentations in the Union session "When and How did Plate Tectonics Begin, What Came Before, and Why is this Controversy important for Understanding the Earth and Exoplanets?" will have 5 minute discussion periods, the scheduled 15 minute end-of-session discussion period is intended to allow other perspectives to be presented by the scientific community. We invite brief (2 powerpoint slides) comments from the community about any aspect of the topic at hand. We encourage anyone who has something pertinent or interesting to say to submit 2 powerpoint slides directly to any one of the four co-convenors listed on this abstract. The first slide should be a simple title with the name and affiliation of the commenter. The second slide should be the content of the comment. The convenors will compile all of these that are submitted up to the noon on the day before the session occurs, when we will upload the compiled files in the order that they were received (if we have received digital scans of signed waivers by that time, see below). During the discussion, we will call on those who have submitted 2 slides to the podium to make their points in 2 minutes or less (total time from being called to leaving the podium). Because this AGU Union session including the discussion period will be live-streamed and recorded, all Discussion Session commenters will be required to sign an AGU waiver acknowledging this and giving permission to be recorded. These will be sent via e-mail to those who submit 2 slide powerpoints. Commenters that do not sign and return the waiver will be scheduled after all commenters who have returned signed waivers and AGU will terminate live streaming and recording accordingly. If no one submits anything then we will have open discussion from the floor. We will also advertise the Monte Verita conference in Locarno Switzerland 17-22 July 2016. This conference will explore in greater detail the 5 key aspects of Plate Tectonic evolution briefly

  10. Far-Field Deformation Resulting from Rheologic Differences Interacting with Tectonic Stresses: An Example from the Pacific/Australian Plate Boundary in Southern New Zealand

    Directory of Open Access Journals (Sweden)

    Phaedra Upton

    2014-07-01

    Full Text Available The Miocene in Southern New Zealand was dominated by strike-slip tectonics. Stratigraphic evidence from this time attests to two zones of subsidence in the south: (a a middle Cenozoic pull-apart basin and (b a regionally extensive subsiding lake complex, which developed east and distal to the developing plate boundary structure. The lake overlay a block of crust with a significantly weak mid-crustal section and we pose the question: can rheological transitions at an angle to a plate boundary produce distal subsidence and/or uplift? We use stratigraphic, structural and geophysical observations from Southern New Zealand to constrain three-dimensional numerical models for a variety of boundary conditions and rheological scenarios. We show that coincident subsidence and uplift can result from purely strike-slip boundary conditions interacting with a transition from strong to weak to strong mid-crustal rheology. The resulting pattern of vertical displacement is a function of the symmetry or asymmetry of the boundary conditions and the extent and orientation of the rheological transitions. For the Southern New Zealand case study, subsidence rates of ~0.1 mm/yr are predicted for a relative plate motion of 25 mm/yr, leading to ~500 m of subsidence over a 5 Ma time period, comparable to the thickness of preserved lacustrine sediments.

  11. The distribution and composition characteristics of siliceous rocks from Qinzhou Bay-Hangzhou Bay joint belt, South China: constraint on the tectonic evolution of plates in South China.

    Science.gov (United States)

    Li, Hongzhong; Zhai, Mingguo; Zhang, Lianchang; Zhou, Yongzhang; Yang, Zhijun; He, Junguo; Liang, Jin; Zhou, Liuyu

    2013-01-01

    The Qinzhou Bay-Hangzhou Bay joint belt is a significant tectonic zone between the Yangtze and Cathaysian plates, where plentiful hydrothermal siliceous rocks are generated. Here, the authors studied the distribution of the siliceous rocks in the whole tectonic zone, which indicated that the tensional setting was facilitating the development of siliceous rocks of hydrothermal genesis. According to the geochemical characteristics, the Neopalaeozoic siliceous rocks in the north segment of the Qinzhou Bay-Hangzhou Bay joint belt denoted its limited width. In comparison, the Neopalaeozoic Qinzhou Bay-Hangzhou Bay joint belt was diverse for its ocean basin in the different segments and possibly had subduction only in the south segment. The ocean basin of the north and middle segments was limited in its width without subduction and possibly existed as a rift trough that was unable to resist the terrigenous input. In the north segment of the Qinzhou Bay-Hangzhou Bay joint belt, the strata of hydrothermal siliceous rocks in Dongxiang copper-polymetallic ore deposit exhibited alternative cycles with the marine volcanic rocks, volcanic tuff, and metal sulphide. These sedimentary systems were formed in different circumstances, whose alternative cycles indicated the release of internal energy in several cycles gradually from strong to weak.

  12. Tectono-stratigraphic evolution of the Canete Basin, Lima, Peru, a plate tectonic model for the Mesozoic evolution of the Central Andes

    Energy Technology Data Exchange (ETDEWEB)

    Aleman, A.M. (Amoco Production Company, Houston, TX (United States))

    1993-02-01

    An arc-trench system has been active in the Central Andes since at least since Late Triassic. This Mesozoic margin was characterized by subduction-erosion processes, PreMesozoic metamorphic outer basement high, pervasive extension, tectonic inversion, sporadic igneous activity and segmentation of the arc. Episodic variations in the tectonic evolution of the associated basins were controlled by the variable angle of subduction, age of the subducted plate, rate and angle of convergence, and the relative motion of the Farallon and South America Plates. The Canete Basin is an elongate frontal arc basin, subparallel to the arc, which documents the early evolution of the Andean Orogeny. In the Canete Basin, the oldest arc volcanism is documented by the interbedded tuffs, lava flows and tuffaceous marine shales of the Late Jurassic Puente Piedra Group which was deposited along a series of isolated and elongated troughs that formed adjacent to the arc. During Late Berriasian the arc subsided and the lithofacies changed from arc to continental derived lithologies. The shallow marine, quartz rich Morro Solar Group was derived from the uplifted metamorphic basement high in the west, as the result of ensialic extension. Locally, volcanic quiescence was interrupted by deposition of the volcaniclastic rich Pucusana Formation. The Late Hauterivian to Aptian Lima Group consists of lime mudstones, shales and subordinated gypsum and bioclastic limestones with volcaniclastic and lava flow facies of the Chilca Group. Stratigraphic relationship rapid changes in thickness and facies of this unit document the development of an incipient arc and the persistence of ensialic extension prior to the maximum paroxysm of volcanic activity of the overlying Albian to Cenomanian Chillon Group. Interbedded volcaniclastic sandstones, lava flows, hyaloclastic breccias and the tuffaceous shales of the Chillon Group were coeval with the early phases of emplacement of the Coastal Batholith (CB).

  13. Plate convergence, crustal delamination, extrusion tectonics and minimization of shortening work as main controlling factors of the recent Mediterranean deformation pattern

    Directory of Open Access Journals (Sweden)

    D. Babbucci

    1997-06-01

    Full Text Available It is argued that the time-space distribution of major post middle Miocene deformation events in the Central-Eastern Mediterranean region, deduced from the relevant literature, can be coherently explained as a consequence of the convergence between the Africa/Arabia and Eurasia blocks. This plate convergence has mainly been accommodated by the consumption of the thinnest parts of the Northern African (Ionian and Levantine basins and peri-Adriatic margins. During each evolutionary phase the space distribution of trench zones is controlled by the basic physical requirement of minimizing the work of horizontal forces, induced by plate convergence, against the resisting forces, i.e., the cohesion of the upper brittle crustal layer and the buoyancy forces at the consuming boundaries. The significant changes of tectonic styles which determined the transition from one phase to the next, like those which occurred around the Messinian and the late Pliocene-early Pleistocene, were determined by the suture of consuming boundaries. When such an event occurs, the system must activate alternative consuming processes to accommodate the convergence of the major confining blocks. The observed deformations in the study area suggest that this tectonic reorganization mostly developed by the lateral extrusion of crustal wedges away from the sutured borders. This mechanism allowed the translation of maximum horizontal stresses from the locked collisional fronts to the zones where consumable lithosphere was still present, in order to activate the next consuming processes. The extensional episodes which led to the formation of basins and troughs in the Tyrrhenian and Aegean zones are interpreted as secondary effects of the outward escape of crustal wedges, like those which occurred in response to longitudinal compressional regimes in the Apennines and Aegean regions.

  14. Two interpenetrating Cu{sup II}/Ni{sup II}-coordinated polymers based on an unsymmetrical bifunctional N/O-tectonic: Syntheses, structures and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yong-Liang [College of Materials & Chemical Engineering, China Three Gorges University, Yichang 443002 (China); Department of Chemistry and Chemical Engineering, Shaanxi Key Laboratory of Comprehensive Utilization of Tailings Resources, Shang Luo University, Shang Luo 726000 (China); Wu, Ya-Pan [College of Materials & Chemical Engineering, China Three Gorges University, Yichang 443002 (China); Li, Dong-Sheng, E-mail: lidongsheng1@126.com [College of Materials & Chemical Engineering, China Three Gorges University, Yichang 443002 (China); Dong, Wen-Wen [College of Materials & Chemical Engineering, China Three Gorges University, Yichang 443002 (China); Zhou, Chun-Sheng [Department of Chemistry and Chemical Engineering, Shaanxi Key Laboratory of Comprehensive Utilization of Tailings Resources, Shang Luo University, Shang Luo 726000 (China)

    2015-03-15

    Two new interpenetrating Cu{sup II}/Ni{sup II} coordination polymers, based on a unsymmetrical bifunctional N/O-tectonic 3-(pyrid-4′-yl)-5-(4″-carbonylphenyl)-1,2,4-triazolyl (H{sub 2}pycz), ([Cu-(Hpycz){sub 2}]·2H{sub 2}O){sub n} (1) and ([Ni(Hpycz){sub 2}]·H{sub 2}O){sub n} (2), have been solvothermally synthesized and structure characterization. Single crystal X-ray analysis indicates that compound 1 shows 2-fold parallel interpenetrated 4{sup 4}-sql layers with the same handedness. The overall structure of 1 is achiral—in each layer of doubly interpenetrating nets, the two individual nets have the opposite handedness to the corresponding nets in the adjoining layers—while 2 features a rare 8-fold interpenetrating 6{sup 6}-dia network that belongs to class IIIa interpenetration. In addition, compounds 1 and 2 both show similar paramagnetic characteristic properties. - Graphical abstract: Two new Cu(II)/Ni(II) coordination polymers present 2D parallel 2-fold interpenetrated 4{sup 4}-sql layers and a rare 3D 8-fold interpenetrating 6{sup 6}-dia network. In addition, magnetic susceptibility measurements show similar paramagnetic characteristic for two complexes. - Highlights: • A new unsymmetrical bifunctional N/O-tectonic as 4-connected spacer. • A 2-fold parallel interpenetrated sql layer with the same handedness. • A rare 8-fold interpenetrating dia network (class IIIa)

  15. Nagra technical report 14-02, geological basics - Dossier II - Sediments and tectonic considerations

    International Nuclear Information System (INIS)

    Madritsch, H.; Deplazes, G.

    2014-01-01

    This dossier is the second of a series of eight reports concerning the safety and technical aspects of locations for the disposal of radioactive wastes in Switzerland. It considers the sediments that can be used and discusses tectonic considerations. As an introduction, the geological framework is discussed with the various sediments from the Paleozoic, Mesozoic and Cenozoic periods. The various methods used to investigate the rock, such as drilling and reflection-seismic methods along with the investigation of surface formations are discussed. A detailed discussion of the stratigraphic and sedimentological characteristics of the various formations follows. Geological structures and the tectonics in the proposed areas are discussed, as are the depth and thickness of the structures

  16. Strike-slip tectonics within the northernmost Philippine Sea plate in an arc-continent collisional setting

    Science.gov (United States)

    Gong, Wei; Jiang, Xiaodian; Guo, Yufan; Xing, Junhui; Li, Congying; Sun, Yang

    2017-09-01

    The geological processes in the northernmost Philippine Sea plate, which is bounded by the Suruga and Sagami troughs, are a typical example of an active collision zone. We attempt to illustrate the stress field through seismic estimations and geodetic analysis and propose the kinematic mode of the northernmost tip of the Philippine Sea plate. Seven events (M ≥ 4.0) are chosen for waveform inversion by the ISOLA software to distinguish the stress field. In particular, six of the chosen events, which exhibit strike-slip motion, are distributed in the eastern area, where few focal mechanisms have been reported by previous studies. According to the available focal mechanisms, strike-slip faults with similar P and T axes are widely distributed in the study area. The stress inversion suggests that the northern area is characterized by a NW-SE compression and a NE-SW extension stress regime, although some spatial differences exist. As indicated by an analysis of the geodesy, epicenters, focal mechanisms, gravity anomalies and velocity structure, the deformation in the northernmost tip is mainly accommodated by several conjugate strike-slip fault systems with steep dips that center on the Izu volcanic line. Generally, the maximum principal stress of the kinematics is derived from the collision between the Philippine Sea plate and Central Japan. Because of the different subduction angles, rates and directions of the down-going plate, diverging slab-pull forces along the Suruga and Sagami troughs may be causing the NE-NNE extension in most of the areas that are bounded by the two troughs. The extension propagates southwards along the Izu volcanic line and reaches the area adjacent to Miyake-jima.

  17. Tectonics Timor-style: Episodic, early-stage orogenesis at a young collision plate margin and implications for orogenic and petroleum fluids

    Science.gov (United States)

    Keep, Myra; Haig, David; Benincasa, Aaron

    2017-04-01

    Timor Island, in the Outer Banda Arc, preserves the orogenic product of an arc-continent collision between the Australian Plate and the Banda Arc that commenced after 9.8 Ma GTS2004 but emerged above sea level only 3.1 Ma ago. The orogenic pile includes large tracts of material from the Australian margin, including the Permian to Middle Jurassic Gondwana Megasequence and the Late Jurassic to early Late Miocene Australian-Margin Megasequence, as well as stratigraphic sequences indicating a Gondwanan terrane with an oceanic affinity. In addition, material from the Banda Arc side of the plate margin, referred to as the Banda Terrane, occurs throughout the island and includes both seaf!oor metamorphosed igneous material and cover sediments. We document four distinct stages to this young orogeny, based largely on detailed and robust stratigraphic and biostratigraphic analyses. An early shortening, between 9.8 Ma and 5.5 Ma reflects the early collision. However, somewhat unexpectedly we found that this early collision was followed by a period of tectonic quiescence, 5.5 Ma to 4.5 Ma, during which time pelagic sedimentation occurred across much of Timor, reflecting locking of the subduction zone. Since 4.5 Ma deformation has been manifest as late, high-angle strike slip faults that dominate the topography and dismember the early-formed thrust sheets, and a more recent phase of broad doming causing uplift relate to the rapid rise of the island. Early deformation, manifest as south- to southeasterly directed thrust nappes, is now preserved in only a handful of locations. Oil and gas seeps and hot springs that occur across East Timor reflect control by underlying structural zones parallel to the strike of the island. These linear zones parallel plate-boundary scale strike-slip faults that exhume the Australian-derived (oldest) rocks on Timor. Recent strike-slip deformation, manifest as linear tectonic melange zones parallel to major, late, high-angle faults controls the

  18. Tectonic growth of a Cretaceous-Eocene accretionary orogen formed at the southern margin of the Caribbean Plate: integrated geological insights from northernmost Colombia

    Science.gov (United States)

    Cardona, A.; Weber, M. B.; Bayona, G.; Jaramillo, C.; Montes, C.; Ojeda, G.; Duque, J. F.; Salazar, C. A.

    2007-05-01

    Geological characteristics from the Cretaceous to Eocene metamorphic and igneous basement rocks from the Guajira and the NW corner of the Sierra Nevada de Santa Marta massifs in the northern Colombian Caribbean region, and the stratigraphy of adjacent basins, reveal different stages of growth of a segmented Late Cretaceous to Eocene accretionary orogen formed by interaction between the NW margin of South America and the Caribbean plate. Extensive intercalations of metavolcano-sedimentary rocks in the Santa Marta region, chemical composition of spinels and pyroxenes from serpentinized mantle tectonites and gabbros, as well as whole rock geochemistry from basaltic dykes from the Guajira massifs, record the evolution of a Cretaceous intra-oceanic arc in a succesion of Mariana- and Chile-type subduction styles. Geological and positive gravity signatures suggest that this arc was accreted and tectonically underplated to the continental margin of South America, creating a Maastrichian-Paleocene syn-orogenic basin, presently cropping out in the Cesar-Rancheria valley. After this collisional event, subduction of the Caribbean plate under South America started, as revealed by intrusion of composite stitched Late Paleocene-Eocene granitoids in the NW corner of the SNSM and Guajira massifs. These plutons show continental calc-alkaline geochemical signatures and more evolved Sr and Nd isotopic compositions than juvenile and older intra-oceanic arc magmatic rocks. This new subduction environment is linked to the convergence between North and South America at this time. Low pressure estimations and fast cooling rates between 450-250° for the Eocene granitoids in the Guajira and Santa Marta regions, indicate shallow < 7 Km depths of intrusion. Local unconformable stratigraphic relationships with Eocene-Miocene sediments at the Guajira region and overimposed post-magmatic low temperature deformation in some of these granitoids suggest an important Late Eocene unroofing and

  19. How We Got to the Northern Hemisphere Ice Ages: Late Miocene Global Cooling and Plate Tectonic CO2 Forcing

    Science.gov (United States)

    Herbert, T.; Dalton, C. A.; Carchedi, C.

    2017-12-01

    The evolution of Earth's climate between "refrigeration" of East Antarctica and the onset of cyclic Northern Hemisphere glaciation spanned more than 11 Myr. In the latest Miocene (Messinian) time, approximately half way on this journey, changes on land, ranging from the expansion of arid zones to major floral and faunal ecosystem shifts, accelerated. Recent compilations of marine surface temperatures reveal that global cooling from the Miocene Optimum (14-16Ma) also accelerated in late Miocene (7-5.35 Ma) time to reach temperatures not much above Holocene conditions. Both hemispheres cooled in parallel, with the changes amplified at higher latitudes in comparison to the tropics. Despite the strong circumstantial case for CO2 decline as the dominant cause of late Miocene climatic and evolutionary change, proxy indicators of CO2concentrations paint an equivocal picture of greenhouse forcing. Here we provide evidence that global sea floor spreading (SFS) rates decelerated at exactly the times of major climatic cooling, linking a decline in tectonic degassing (at both subduction zones and mid-ocean ridges) to fundamental shifts in the global carbon cycle. Our work utilizes newly available global compilations of seafloor fabric and marine magnetic anomalies provided by the NSF-funded Global Seafloor Fabric and Magnetic Lineation Data Base Project. Previous global compilations of SFS typically binned estimates over 10 Myr increments, losing critical resolution on the timescale of late Neogene climate changes. We further improve the signal:noise of SFS estimates by incorporating recent advances in the astronomical calibration of the Miocene geomagnetic polarity timescale. We use two approaches to compile spreading rate estimates over the past 20 Myr at each spreading system: optimized finite rotation calculations, and averages of sea floor-spreading derived from the distances of magnetic lineations along flow lines on the sea floor. Weighted by ridge length, we find an 25

  20. PLATE

    DEFF Research Database (Denmark)

    Kling, Joyce; Hjulmand, Lise-Lotte

    2008-01-01

    ’s level of English is sufficient for the increasing number of courses offered in English each semester. This paper addresses these concerns and describes a pilot project initiated in 2003 at CBS to gauge the overall English language proficiency of those teaching content courses in English. Through...... the Project in Language Assessment for Teaching in English (PLATE) language professionals from CBS’s Language Center observe teachers and provide feedback using evaluation criteria from the Common European Framework for Reference (CEFR) supplemented by some additional criteria which take the LSP nature...... of academic teaching and lecturing into account....

  1. Structural and Tectonic Map Along the Pacific-North America Plate Boundary in Northern Gulf of California, Sonora Desert and Valle de Mexicali, Mexico, from Seismic Reflection Evidence

    Science.gov (United States)

    Gonzalez-Escobar, M.; Suarez-Vidal, F.; Mendoza-Borunda, R.; Martin Barajas, A.; Pacheco-Romero, M.; Arregui-Estrada, S.; Gallardo-Mata, C.; Sanchez-Garcia, C.; Chanes-Martinez, J.

    2012-12-01

    Between 1978 and 1983, Petróleos Mexicanos (PEMEX) carried on an intense exploration program in the northern Gulf of California, the Sonora Desert and the southern part of the Mexicali Valley. This program was supported by a seismic reflection field operation. The collected seismic data was 2D, with travel time of 6 s recording, in 48 channels, and the source energy was: dynamite, vibroseis and air guns. Since 2007 to present time, the existing seismic data has been re-processing and ire-interpreting as part of a collaboration project between the PEMEX's Subdirección de Exploración (PEMEX) and CICESE. The study area is located along a large portion of the Pacific-North America plate boundary in the northern Gulf of California and the Southern part of the Salton Trough tectonic province (Mexicali Valley). We present the result of the processes reflection seismic lines. Many of the previous reported known faults were identify along with the first time described located within the study region. We identified regions with different degree of tectonic activity. In structural map it can see the location of many of these known active faults and their associated seismic activity, as well as other structures with no associated seismicity. Where some faults are mist placed they were deleted or relocated based on new information. We included historical seismicity for the region. We present six reflection lines that cross the aftershocks zone of the El Mayor-Cucapah earthquake of April 4, 2010 (Mw7.2). The epicenter of this earthquake and most of the aftershocks are located in a region where pervious to this earthquake no major earthquakes are been reported. A major result of this study is to demonstrate that there are many buried faults that increase the seismic hazard.

  2. Towards community-driven paleogeographic reconstructions: integrating open-access paleogeographic and paleobiology data with plate tectonics

    Directory of Open Access Journals (Sweden)

    N. Wright

    2013-03-01

    Full Text Available A variety of paleogeographic reconstructions have been published, with applications ranging from paleoclimate, ocean circulation and faunal radiation models to resource exploration; yet their uncertainties remain difficult to assess as they are generally presented as low-resolution static maps. We present a methodology for ground-truthing the digital Palaeogeographic Atlas of Australia by linking the GPlates plate reconstruction tool to the global Paleobiology Database and a Phanerozoic plate motion model. We develop a spatio-temporal data mining workflow to validate the Phanerozoic Palaeogeographic Atlas of Australia with paleoenvironments derived from fossil data. While there is general agreement between fossil data and the paleogeographic model, the methodology highlights key inconsistencies. The Early Devonian paleogeographic model of southeastern Australia insufficiently describes the Emsian inundation that may be refined using biofacies distributions. Additionally, the paleogeographic model and fossil data can be used to strengthen numerical models, such as the dynamic topography and the associated inundation of eastern Australia during the Cretaceous. Although paleobiology data provide constraints only for paleoenvironments with high preservation potential of organisms, our approach enables the use of additional proxy data to generate improved paleogeographic reconstructions.

  3. Role of the Tectonic inheritance on multi-phased rifting of the Sperchios Basin (Greece), north-western boundary of the Aegean Plate

    Science.gov (United States)

    Chanier, Frank; Ferriere, Jacky; Averbuch, Olivier; Gaullier, Virginie; Graveleau, Fabien

    2017-04-01

    The Aegean plate is characterized by active extension, mainly occurring during the Pliocene to the Quaternary. This extensional deformation is considered as the upper plate response to the rollback of the northward subducting African slab. In Central Greece, it has led to the formation of large rifted basins, such as the Corinth Rift or the Sperchios basin. Both are experiencing active tectonics, as seismicity and morphotectonic analysis demonstrate. In this study, we focus on the East-West Sperchios basin, which has developed obliquely across a major NW-SE thrust zone separating the internal and external zones of the Hellenides mountain range. This range has developed since the late Jurassic, with the obduction of the Maliac Ocean, up to the Eocene times, with the collision of the External Zones. The Frontal Thrust of the internal Hellenides constitutes a major discontinuity within the crust, which may have influenced the development of the Sperchios basin. Our field investigations indicate that the southern boundary of the Sperchios rifted basin shows several large E-W to NW-SE normal faults that accommodate km-scale offsets. Our fault plane analysis showed a variety of fault orientations, all with dip-slip slicken-slides. It suggests at least two major episodes of extension, starting with a NE-SW direction in the Pliocene and then followed by a N-S direction. The latter is still active today and confirmed by geodetic studies and by earthquakes focal mechanisms. The early NE-SW episode of extension (mainly Pliocene in age) is expressed in the field by low-angle normal faults, dipping 20 to 30° northeastward, more or less parallel to the Frontal thrust of the Internal Hellenides. These low-angle normal faults are separating the platform limestones of the external zones from the upper tectonic units of the internal zones. We suggest that these low-angle normal faults are corresponding to the earlier stage of rifting and that they are rooted in the major thrust

  4. Evolution of Plate Tectonics on Earth since the Mid-Mesoarchean was Controlled by Sedimentary Fluxes from Continents to Oceans and Mantle Temperature

    Science.gov (United States)

    Sobolev, S. V.; Brown, M.

    2017-12-01

    Plate tectonics (PT) is the most important geological process operating on Earth, making it unique among the rocky planets in the Solar System. The question of how PT was initiated and which factors controlled its evolution over Earth's history are widely discussed, but remain controversial. It is broadly accepted that a necessary condition for initiation and stable operation of PT is maintaining low strength along plate boundaries, particularly along the subduction zone interfaces in the subduction channels. Examples from the South American Andes and other convergent margins show that unconsolidated continental sediments in trenches serve as an efficient lubricant for subduction; if these are lacking, friction in the subduction channel and strength of the plate boundary are significantly increased. We suggest that lubrication of subduction by accumulation of continental sediments in trenches played a crucial role during the evolution of PT on Earth since the mid-Mesoarchean. We posit that continental emergence and enhanced surface erosion caused an increasing flux of sediments into the oceans, which in turn lubricated subduction channels and intensified PT. Thus, peaks in orogenesis, as confirmed by several proxies, during periods of supercraton/supercontinent assembly represent periods of vigorous subduction and continental sedimentation in trenches prior to terminal collision. Conversely, a decrease in plate boundary length and a reduction in continental sediment accumulation in trenches during periods of stability after supercraton/supercontinent assembly is the likely reason for periods of lower PT vigor, including the so called `boring billion' between 1.8 and 0.8 Ga. The largest surface erosion and subduction-lubrication event occurred at the end of the `snowball' Earth epoch in the Neoproterozoic and likely accelerated the most recent episode of vigorous PT. Based on analysis of various geological observations, we suggest that the cyclic behavior of PT on

  5. Earthquakes as Expressions of Tectonic Activity

    Indian Academy of Sciences (India)

    With an introduction to the ideas of plate tectonics and earthquake terminology, this article introduces ... timum thickness, to generate a fragmented architecture. A hard and fragmented outer shell, floating on the ... The basic idea of the plate tectonic model is that the outer shell of the Earth is divided into several plates, both ...

  6. Clavicle hook plate fixation for displaced lateral-third clavicle fractures (Neer type II): a functional outcome study.

    LENUS (Irish Health Repository)

    Good, Daniel W

    2012-08-01

    Controversy exists with the use of the acromioclavicular hook plate for the treatment of lateral-third clavicle fractures (Neer type II). This is thought to stem from problems associated with the hook plate causing impingement symptoms, which can cause long-term limitation of movement and pain. Our aim was to evaluate the functional outcomes of patients with lateral-third clavicle fractures treated with the hook plate.

  7. Numerical simulation of projectile impact on mild steel armour plates using LS-DYNA, Part II: Parametric studies

    OpenAIRE

    Raguraman, M; Deb, A; Gupta, NK; Kharat, DK

    2008-01-01

    In Part I of the current two-part series, a comprehensive simulation-based study of impact of Jacketed projectiles on mild steel armour plates has been presented. Using the modelling procedures developed in Part I, a number of parametric studies have been carried out for the same mild steel plates considered in Part I and reported here in Part II. The current investigation includes determination of ballistic limits of a given target plate for different projectile diameters and impact velociti...

  8. Two contrasting late Paleozoic magmatic episodes in the northwestern Chinese Tianshan Belt, NW China: Implication for tectonic transition from plate convergence to intra-plate adjustment during accretionary orogenesis

    Science.gov (United States)

    Wang, Xiangsong; Cai, Keda; Sun, Min; Xiao, Wenjiao; Xia, Xiaoping; Wan, Bo; Bao, Zihe; Wang, Yannan

    2018-03-01

    temperature (815-938 °C) volcanism to oceanic slab break-off during assembly of the West Junggar Terrane with the Yili Block, and relate the generation of ca. 288 Ma low temperature (723-735 °C) plutonism to subsequent strike-slipping of North Tianshan Fault that facilitated introduction of water-fluxes triggering hydrous partial melting of juvenile lower crust. The sequential magmatic episodes in the northwestern Chinese Tianshan Belt may provide a crucial clue to a tectonic transition from plate convergence to intra-plate adjustment during the formation of the Kazakhstan Orocline in the late Paleozoic.

  9. Spiral tectonics

    Science.gov (United States)

    Hassan Asadiyan, Mohammad

    2014-05-01

    Spiral Tectonics (ST) is a new window to global tectonics introduced as alternative model for Plate Tectonics (PT). ST based upon Dahw(rolling) and Tahw(spreading) dynamics. Analogues to electric and magnetic components in the electromagnetic theory we could consider Dahw and Tahw as components of geodynamics, when one component increases the other decreases and vice versa. They are changed to each other during geological history. D-component represents continental crust and T-component represents oceanic crust. D and T are two arm of spiral-cell. T-arm 180 degree lags behind D-arm so named Retard-arm with respect to D or Forward-arm. It seems primary cell injected several billions years ago from Earth's center therefore the Earth's core was built up first then mantel and finally the crust was build up. Crust building initiate from Arabia (Mecca). As the universe extended gravitation wave swirled the earth fractaly along cycloid path from big to small scale. In global scale (order-0) ST collect continents in one side and abandoned Pacific Ocean in the other side. Recent researches also show two mantels upwelling in opposite side of the Earth: one under Africa (tectonic pose) and the other under Pacific Ocean (tectonic tail). In higher order (order-1) ST build up Africa in one side and S.America in the other side therefore left Atlantic Ocean meandered in between. In order-n e.g. Khoor Musa and Bandar-Deylam bay are seen meandered easterly in the Iranian part but Khoor Abdullah and Kuwait bay meandered westerly in the Arabian part, they are distributed symmetrically with respect to axis of Persian Gulf(PG), these two are fractal components of easterly Caspian-wing and westerly Black Sea-wing which split up from Anatoly. Caspian Sea and Black Sea make two legs of Y-like structure, this shape completely fitted with GPS-velocity map which start from PG and split up in the Catastrophic Point(Anatoly). We could consider PG as remnants of Ancient Ocean which spent up

  10. Maps, Plates, and Mount Saint Helens.

    Science.gov (United States)

    Lary, Barbara E.; Krockover, Gerald H.

    1987-01-01

    Describes a laboratory activity on plate tectonics which focuses on the connection between plate tectonics and the different types of volcanoes. Provides questions for discussion and includes suggestions for extending the activity. (ML)

  11. Ophiolites of Iran: Keys to understanding the tectonic evolution of SW Asia: (II) Mesozoic ophiolites

    Science.gov (United States)

    Moghadam, Hadi Shafaii; Stern, Robert J.

    2015-03-01

    Iran is a mosaic of continental terranes of Cadomian (520-600 Ma) age, stitched together along sutures decorated by Paleozoic and Mesozoic ophiolites. Here we present the current understanding of the Mesozoic (and rare Cenozoic) ophiolites of Iran for the international geoscientific audience. We summarize field, chemical and geochronological data from the literature and our own unpublished data. Mesozoic ophiolites of Iran are mostly Cretaceous in age and are related to the Neotethys and associated backarc basins on the S flank of Eurasia. These ophiolites can be subdivided into five belts: 1. Late Cretaceous Zagros outer belt ophiolites (ZOB) along the Main Zagros Thrust including Late Cretaceous-Early Paleocene Maku-Khoy-Salmas ophiolites in NW Iran as well as Kermanshah-Kurdistan, Neyriz and Esfandagheh (Haji Abad) ophiolites, also Late Cretaceous-Eocene ophiolites along the Iraq-Iran border; 2. Late Cretaceous Zagros inner belt ophiolites (ZIB) including Nain, Dehshir, Shahr-e-Babak and Balvard-Baft ophiolites along the southern periphery of the Central Iranian block and bending north into it; 3. Late Cretaceous-Early Paleocene Sabzevar-Torbat-e-Heydarieh ophiolites of NE Iran; 4. Early to Late Cretaceous Birjand-Nehbandan-Tchehel-Kureh ophiolites in eastern Iran between the Lut and Afghan blocks; and 5. Late Jurassic-Cretaceous Makran ophiolites of SE Iran including Kahnuj ophiolites. Most Mesozoic ophiolites of Iran show supra-subduction zone (SSZ) geochemical signatures, indicating that SW Asia was a site of plate convergence during Late Mesozoic time, but also include a significant proportion showing ocean-island basalt affinities, perhaps indicating the involvement of subcontinental lithospheric mantle.

  12. Production of Copper-Plated Beamline Bellows and Spools for LCLS-II

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, Katherine M. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Carpenter, Brian C. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Daly, Ed [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Huque, Naeem A. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Peshehonoff, Ted [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Arkan, Tug [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Lunin, A. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Premo, K. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

    2017-05-01

    The SLAC National Accelerator Laboratory is currently constructing a major upgrade to its accelerator, the Linac Coherent Light Source II (LCLS-II). Several Department of Energy national laboratories, including the Thomas Jefferson National Accelerator Facility (JLab) and Fermi National Accelerator Laboratory (FNAL), are participating in this project. The 1.3-GHz cryomodules for this project consist of eight cavities separated by bellows (expansion joints) and spools (tube sections), which are copper plated for RF conduction. JLab is responsible for procurement of these bellows and spools, which are delivered to JLab and FNAL for assembly into cryomodules. Achieving accelerator-grade copper plating is always a challenge and requires careful specification of requirements and application of quality control processes. Due to the demanding technical requirements of this part, JLab implemented procurement strategies to make the process more efficient as well as provide process redundancy. This paper discusses the manufacturing challenges that were encountered and resolved, as well as the strategies that were employed to minimize the impact of any technical issues.

  13. Tectonic History and Deep Structure of the Demerara Plateau from Combined Wide-Angle and Reflection Seismic Data and Plate Kinematic Reconstructions

    Science.gov (United States)

    Klingelhoefer, F.; Museur, T.; Roest, W. R.; Graindorge, D.; Chauvet, F.; Loncke, L.; Basile, C.; Poetisi, E.; Deverchere, J.; Lebrun, J. F.; Perrot, J.; Heuret, A.

    2017-12-01

    Many transform margins have associated intermediate depth marginal plateaus, which are commonly located between two oceanic basins. The Demerara plateau is located offshore Surinam and French Guiana. Plate kinematic reconstructions show that the plateau is located between the central and equatorial Atlantic in a position conjugate to the Guinean Plateau. In the fall of 2016, the MARGATS cruise acquired geophysical data along the 400 km wide Demerara plateau. The main objective of the cruise was to image the deep structure of the Demerara plateau and to study its tectonic history. A set of 4 combined wide-angle and reflection seismic profiles was acquired along the plateau, using 80 ocean-bottom seismometers, a 3 km long seismic streamer and a 8000 cu inch tuned airgun array. Forward modelling of the wide-angle seismic data on a profile, located in the eastern part of the plateau and oriented in a NE-SW direction, images the crustal structure of the plateau, the transition zone and the neighbouring crust of oceanic origin, up to a depth of 40 km. The plateau itself is characterised by a crust of 30 km thickness, subdivided into three distinct layers. However, the velocities and velocity gradients do not fit typical continental crust, with a lower crustal layer showing untypically high velocities and an upper layer having a steep velocity gradient. From this model we propose that the lowermost layer is probably formed from volcanic underplated material and that the upper crustal layer likely consists of the corresponding extrusive volcanic material, forming thick seaward-dipping reflector sequences on the plateau. A basement high is imaged at the foot of the slope and forms the ocean-continent transition zone. Further oceanward, a 5-6 km thick crust is imaged with velocities and velocity gradients corresponding to a thin oceanic crust. A compilation of magnetic data from the MARGATS and 3 previous cruises shows a high amplitude magnetic anomaly along the northern

  14. Global tectonics and space geodesy.

    Science.gov (United States)

    Gordon, R G; Stein, S

    1992-04-17

    Much of the success of plate tectonics can be attributed to the near rigidity of tectonic plates and the availability of data that describe the rates and directions of motion across narrow plate boundaries \\m=~\\1 to 60 kilometers wide. Nonetheless, many plate boundaries in both continental and oceanic lithosphere are not narrow but are hundreds to thousands of kilometers wide. Wide plate boundary zones cover \\m=~\\15 percent of Earth's surface area. Space geodesy, which includes very long baseline radio interferometry, satellite laser ranging, and the global positioning system, is providing the accurate long-distance measurements needed to estimate the present motion across and within wide plate boundary zones. Space geodetic data show that plate velocities averaged over years are remarkably similar to velocities averaged over millions of years.

  15. Performative Tectonics

    DEFF Research Database (Denmark)

    Holst, Malene Kirstine; Kirkegaard, Poul Henning; Mullins, Michael

    2010-01-01

    This paper studies two digital generative tools in terms of Performative Tectonics. Performative Tectonics is a term developed in the paper, which links the contemporary development of digital tools to the tectonic tradition of architecture. Within the theoretical framework of this definition......, the paper presents case studies of the structural optimisation software eifForm, and the parametric modelling software Generative-Components....

  16. Mantle constraints on the plate tectonic evolution of the Tonga-Kermadec-Hikurangi subduction zone and the South Fiji Basin region

    NARCIS (Netherlands)

    Schellart, W.P.; Spakman, W.

    2012-01-01

    The Tonga–Kermadec–Hikurangi subduction zone is a major plate boundary in the Southwest Pacific region, where the Pacific plate subducts westward underneath the Australian plate. Considerable controversy exists regarding the Cenozoic evolution of this subduction zone, its connection with

  17. Mantle constraints on the plate tectonic evolution of the Tonga-Kermadec-Hikurangi subduction zone and the South Fiji Basin region

    NARCIS (Netherlands)

    Schellart, W. P.; Spakman, W.

    The Tonga-Kermadec-Hikurangi subduction zone is a major plate boundary in the Southwest Pacific region, where the Pacific plate subducts westward underneath the Australian plate. Considerable controversy exists regarding the Cenozoic evolution of this subduction zone, its connection with the

  18. Operation and performance of the CMS Resistive Plate Chambers during LHC run II

    CERN Document Server

    Eysermans, Jan

    2017-01-01

    The Resitive Plate Chambers (RPC) at the Compact Muon Solenoid (CMS) experiment at the CERN Large Hadron Collider (LHC) provide redundancy to the Drift Tubes in the barrel and Cathode Strip Chambers in the endcap regions. Consisting of 1056 double gap RPC chambers, the main detector parameters and environmental conditions are carefully monitored during the data taking period. At a center of mass energy of 13 TeV, the luminosity reached record levels which was challenging from the operational and performance point of view. In this work, the main operational parameters are discussed and the overall performance of the RPC system is reported for the LHC run II data taking period. With a low amount of inactive chambers, a good and stable detector performance was achieved with high efficiency.

  19. The Clinical and Economic Impact of Generic Locking Plate Utilization at a Level II Trauma Center.

    Science.gov (United States)

    Mcphillamy, Austin; Gurnea, Taylor P; Moody, Alastair E; Kurnik, Christopher G; Lu, Minggen

    2016-12-01

    In today's climate of cost containment and fiscal responsibility, generic implant alternatives represent an interesting area of untapped resources. As patents have expired on many commonly used trauma implants, generic alternatives have recently become available from a variety of sources. The purpose of this study was to examine the clinical and economic impact of a cost containment program using high quality, generic orthopaedic locking plates. The implants available for study were anatomically precontoured plates for the clavicle, proximal humerus, distal radius, proximal tibia, distal tibia, and distal fibula. Retrospective review. Level II Trauma center. 828 adult patients with operatively managed clavicle, proximal humerus, distal radius, proximal tibia, tibial pilon, and ankle fractures. Operative treatment with conventional or generic implants. The 414 patients treated with generic implants were compared with 414 patients treated with conventional implants. There were no significant differences in age, sex, presence of diabetes, smoking history or fracture type between the generic and conventional groups. No difference in operative time, estimated blood loss or intraoperative complication rate was observed. No increase in postoperative infection rate, hardware failure, hardware loosening, malunion, nonunion or need for hardware removal was noted. Overall, our hospital realized a 56% reduction in implant costs, an average savings of $1197 per case, and a total savings of $458,080 for the study period. Use of generic orthopaedic implants has been successful at our institution, providing equivalent clinical outcomes while significantly reducing implant expenditures. Based on our data, the use of generic implants has the potential to markedly reduce operative costs as long as quality products are used. Therapeutic Level III.

  20. RNL automated ultrasonic inspection of the PISC II PWR inlet nozzle (Plate 3)

    International Nuclear Information System (INIS)

    Rogerson, A.; Poulter, L.N.J.; Clough, P.; Cooper, A.G.

    1987-01-01

    In June 1984, Risley Nuclear Laboratories (RNL) performed an automated ultrasonic inspection of the Pressurized Water Reactor (PWR) inlet nozzle (plate 3) from the international Programme of Inspection of Steel Components (PISC II) round-robin inspection programme. High-sensitivity pulse-echo detection and predominantly time-of-flight diffraction sizing techniques were employed from the clad inner surface of the nozzle using digital data collection, analysis, and display facilities developed at RNL. RNL detected 30 out of 31 intended weld flaws, achieved one hundred per cent correct acceptance of all acceptable flaws and had a correct rejection frequency on all rejectable flaws of 0.86. The results confirm that well-conceived automated inspection procedures, similar to those used by RNL in this nozzle inspection, could form the basis of a PSI/ISI procedure for reactor pressure vessel nozzle regions. Analysis of the RNL results with regard to the influence of flaw characteristics on inspection performance lends strong support to the general conclusions drawn by the PISC Data Analysis Group. In particular, the most difficult flaws to accurately size were circular smooth and rough flaws. Examination of the RNL results on individual flaws reveals valuable information on the strengths and weaknesses of the adopted procedures and points towards procedural changes that would improve inspection performance. This report describes the procedures adopted by RNL, in the inspection, and reviews the results in the light of definitive flaw information. (author)

  1. Tectonic stress pattern in the Chinese Mainland from the inversion of ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 126; Issue 3. Tectonic stress pattern in the ... models (e.g., the extrusion model). From the perspective of tectonics, the mutual actions among the Eurasian plate, Pacific plate and Indian plate caused the present-day tectonic stress field in the Chinese Mainland.

  2. Ballistic Behaviour of Thick Steel Armour Plate under Oblique Impact : Experimental Investigation II

    OpenAIRE

    S. N. Dikshit

    1999-01-01

    The ballistic behaviour of thick steel armour plate at different obliquities has been investigated. Ballistic experiments were conducted in the velocity range 300-800 mls at 0°, 15°, 30° and 45° obliquity .A steel, conical projectile or 6.1 mm diameter was impacted on a 10 mm thick steel armour plate. At 30° and 45° obliquity, the plate offers protection up to a striking velocity of 800 mls. At zero obliquity, the plate provides protection below 6~ m/s. The depth of penetration decreases with...

  3. Digital Tectonics

    DEFF Research Database (Denmark)

    Christiansen, Karl; Borup, Ruben; Søndergaard, Asbjørn

    2014-01-01

    Digital Tectonics treats the architectonical possibilities in digital generation of form and production. The publication is the first volume of a series, in which aspects of the strategic focus areas of the Aarhus School of Architecture will be disseminated.......Digital Tectonics treats the architectonical possibilities in digital generation of form and production. The publication is the first volume of a series, in which aspects of the strategic focus areas of the Aarhus School of Architecture will be disseminated....

  4. Active control of sound transmission/radiation from elastic plates by vibration inputs. II - Experiments

    Science.gov (United States)

    Metcalf, V. L.; Fuller, C. R.; Silcox, R. J.; Brown, D. E.

    1992-01-01

    Actively controlled harmonic force inputs were applied experimentally to reduce the sound transmitted through an elastic circular plate. The control implementation used a time domain least mean square adaptive algorithm with two error sensors. The control forces were applied directly to the plate by point force vibration inputs, while the error information and performance were measured in the radiated acoustic field by microphones. Test cases were also performed in which the error sensors were accelerometers mounted on the plate. When accelerometers were used as error sensors, the controller performance was degraded; leading to the conclusion that minimizing plate motion does not necessarily lead to an associated decrease in radiated sound levels. In contrast, the results show excellent attenuation of the transmitted sound field when microphone error sensors were used. This result was consistent over a range of frequencies. In addition, the experimental results are compared to previously derived analytical results and the effect of using a point or global minimization scheme is discussed.

  5. Advanced Composite Bipolar Plate for Unitized Regenerative Fuel Cell/Electrolyzer Systems, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Development of an advanced composite bipolar plate is proposed for a unitized regenerative fuel cell and electrolyzer system that operates on pure feed streams...

  6. Role of the offshore Pedro Banks left-lateral strike-slip fault zone in the plate tectonic evolution of the northern Caribbean

    Science.gov (United States)

    Ott, B.; Mann, P.; Saunders, M.

    2013-12-01

    Previous workers, mainly mapping onland active faults on Caribbean islands, defined the northern Caribbean plate boundary zone as a 200-km-wide bounded by two active and parallel strike-slip faults: the Oriente fault along the northern edge of the Cayman trough with a GPS rate of 14 mm/yr, and and the Enriquillo-Plaintain Garden fault zone (EPGFZ) with a rate of 5-7 mm/yr. In this study we use 5,000 km of industry and academic data from the Nicaraguan Rise south and southwest of the EPGFZ in the maritime areas of Jamaica, Honduras, and Colombia to define an offshore, 700-km-long, active, left-lateral strike-slip fault in what has previously been considered the stable interior of the Caribbean plate as determined from plate-wide GPS studies. The fault was named by previous workers as the Pedro Banks fault zone because a 100-km-long segment of the fault forms an escarpment along the Pedro carbonate bank of the Nicaraguan Rise. Two fault segments of the PBFZ are defined: the 400-km-long eastern segment that exhibits large negative flower structures 10-50 km in width, with faults segments rupturing the sea floor as defined by high resolution 2D seismic data, and a 300-km-long western segment that is defined by a narrow zone of anomalous seismicity first observed by previous workers. The western end of the PBFZ terminates on a Quaternary rift structure, the San Andres rift, associated with Plio-Pleistocene volcanism and thickening trends indicating initial rifting in the Late Miocene. The southern end of the San Andreas rift terminates on the western Hess fault which also exhibits active strands consistent with left-lateral, strike-slip faults. The total length of the PBFZ-San Andres rift-Southern Hess escarpment fault is 1,200 km and traverses the entire western end of the Caribbean plate. Our interpretation is similar to previous models that have proposed the "stable" western Caribbean plate is broken by this fault whose rate of displacement is less than the threshold

  7. Optimization of a functionally graded circular plate with inner rigid thin obstacles. II. Approximate problems

    Czech Academy of Sciences Publication Activity Database

    Hlaváček, Ivan; Lovíšek, J.

    2011-01-01

    Roč. 91, č. 12 (2011), s. 957-966 ISSN 0044-2267 R&D Projects: GA AV ČR(CZ) IAA100190803 Institutional research plan: CEZ:AV0Z10190503 Keywords : control of elliptic variational inequalities * functionally graded plates * optimal design of plates * finite element approximations Subject RIV: BA - General Mathematics Impact factor: 0.863, year: 2011 http://onlinelibrary.wiley.com/doi/10.1002/zamm.201000238/abstract

  8. Wear plates control rod guide tubes top internal reactor vessel C. N. VANDELLOS II

    International Nuclear Information System (INIS)

    2010-01-01

    The guide tubes for control rods forming part of the upper internals of the reactor vessel, its function is to guide the control rod to permit its insertion in the reactor core. These guide tubes are suspended from the upper support plate which are fixed by bolts and extending to the upper core plate which is fastened by clamping bolts (split pin) to prevent lateral displacement of the guide tubes, while allowing axial expansion.

  9. Active tectonics, fault patterns, and stress field of Deception Island: A response to oblique convergence between the Pacific and Antarctic plates

    Science.gov (United States)

    Maestro, A.; Somoza, L.; Rey, J.; Martínez-Frías, J.; López-Martínez, J.

    2007-02-01

    Palaeostress results derived from brittle mesoscopic structures on Deception Island (Bransfield Trough, Western Antarctica) show a recent stress field characterized by an extensional regime, with local compressional stress states. The maximum horizontal stress ( σy) shows NW-SE and NNE-SSW to NE-SW orientations and horizontal extension ( σ3) in NE-SW and WNW-ESE to NW-SE directions. Alignments of mesofractures show a maximum of NNE-SSW orientation and several relative maxima striking N030-050E, N060-080E, N110-120E, and N160-170E. Subaerial and submarine macrofaults of Deception Island show six main systems controlling the morphology of the island: N-S, NNE-SSW, NE-SW, ENE-WSW to E-W, WNW-ESE, and NNW-SSE. Geochemical patterns related to submarine hydrothermally influenced fault and fissure pathways also share the same trends. The orientation of these fault systems is compared to Riedel shear fractures. Following this model, we propose two evolutionary stages from geometrical relationships between the location and orientation of joints and faults. These stages imply a counter-clockwise rotation of Deception Island, which may be linked to a regional left-lateral strike-slip. In addition, the simple shear zone could be a response to oblique convergence between the Antarctic and Pacific plates. This stress direction is consistent with the present-day movements between the Antarctic, Scotia, and Pacific plates. Nevertheless, present basalt-andesitic volcanism and deep earthquake focal mechanisms may indicate rollback of the former Phoenix subducted slab, which is presently amalgamated with the Pacific plate. We postulate that both mechanisms could occur simultaneously.

  10. Numerical Simulation of the Borehole Magnetic Field for Resolving the Possible Rotation of Tectonic Basins and Plates during ICDP and IODP Experiments

    Science.gov (United States)

    Lee, S. M.; Parq, J. H.

    2017-12-01

    An accurate measurement of magnetic field inside the borehole, together with a right set of paleomagnetic measurements on the recovered core samples, should allow one to resolve important elements such as the rotation of the basin or the plate on which the basin is located. The ability to resolve the rotation of the basin can be crucial during drilling experiments by International Continental Scientific Drilling Program (ICDP) and International Ocean Discovery Program (IODP). A good example where the rotation is a central question is the Philippine Sea Plate, which is thought to have rotated about 90° clockwise during the last 55 million years. Despite the significance, previous borehole magnetometers were not accurate enough to achieve such a goal because, among various technical issues, determining the orientation of the sensor inside the borehole to a very high level of accuracy was not easy. The next-generation (third-generation) borehole magnetometer (3GBM) was developed to overcome this difficulty and to bring paleomagnetic investigations to a new level. Even with the new development, however, there are still concerns whether the new instrument can really resolve the rotation because the magnetic field anomalies generated by the sediment is generally very low. In this paper, we present numerical simulations based on finite element method of the magnetic field inside the borehole that were conducted as part of a test to demonstrate that, despite low levels of magnetization, the magnetic fields can be resolved. The results also served as an important input on the design requirements of the borehole magnetometer. Various cases were considered, including the situation where the sedimentary layer is horizontal and inclined. We also explored the cases where volcanic sills were present within the sedimentary layer as they may provide a greater magnetic signature than having sediment alone, and thus improving our chances of determining the rotation. Simulations are

  11. Planar polarization of Vangl2 in the vertebrate neural plate is controlled by Wnt and Myosin II signaling

    Directory of Open Access Journals (Sweden)

    Olga Ossipova

    2015-07-01

    Full Text Available The vertebrate neural tube forms as a result of complex morphogenetic movements, which require the functions of several core planar cell polarity (PCP proteins, including Vangl2 and Prickle. Despite the importance of these proteins for neurulation, their subcellular localization and the mode of action have remained largely unknown. Here we describe the anteroposterior planar cell polarity (AP-PCP of the cells in the Xenopus neural plate. At the neural midline, the Vangl2 protein is enriched at anterior cell edges and that this localization is directed by Prickle, a Vangl2-interacting protein. Our further analysis is consistent with the model, in which Vangl2 AP-PCP is established in the neural plate as a consequence of Wnt-dependent phosphorylation. Additionally, we uncover feedback regulation of Vangl2 polarity by Myosin II, reiterating a role for mechanical forces in PCP. These observations indicate that both Wnt signaling and Myosin II activity regulate cell polarity and cell behaviors during vertebrate neurulation.

  12. Geochemical characteristics of Mesoproterozoic metabasite dykes from the Chhotanagpur Gneissic Terrain, eastern India: Implications for their emplacement in a plate margin tectonic environment

    Science.gov (United States)

    Srivastava, Rajesh K.; Sinha, Anup K.; Kumar, Suresh

    2012-04-01

    A number of mafic intrusive bodies (mostly dykes) are exposed in the Chhotanagpur Gneissic Terrain (CGT). Most dykes trend in ENE-WSW to E-W following major structural trends of the region. These metabasite dykes show granoblastic to grano-nematoblastic textures and contain hornblende, plagioclase, chlorite, quartz and epidote which suggest their metamorphism under amphibolite grade P-T conditions. Although no radiometric age is available for the metabasite dykes, field relationships with host rock and available geochronology on granitoids suggest their emplacement during Mesoproterozoic. Geochemical characteristics of these dykes classify them as low-K tholeiite to medium-K calc-alkaline type. At least two types of metabasite dykes are recognized on the basis of their HFSE contents; one group shows entirely calc-alkaline nature, whereas the other group has rocks of tholeiite-calc-alkaline series. High Mg# observed in a number of samples indicates their derivation from primary melt. Multi-element spidergrams and rare-earth element patterns observed in these samples also corroborate their derivation from different magma batches. Trace element patterns observed for Nb-Ta, Hf-Zr, Sr and Y suggesting involvement of subduction related processes in the genesis of CGT metabasite dykes. Perceived geochemical characteristics suggest that metamorphism did not affect much on the chemistry of metabasites but source region, responsible for the generation of CGT metabasites, was possibly modified during subduction process. This study suggests that magma generated in a destructive plate setting fed the Mesoproterozoic mafic dykes of the CGT.

  13. The use of BAS-TR imaging plates calibration in determining the resolving power of Fuji BAS-1800II image plate reader

    Science.gov (United States)

    Alnaimi, R.

    2018-01-01

    The importance of this work lies in assuring the reliability of the results obtained from both imaging plates type BAS-TR and Fuji Image Reader BAS-1800II as they are widely used in calculating essential x-ray sources parameters such as the source size, x-ray flux and brilliance, hence, the calibration presented in this work. For such quantitative analysis, a common practice used by many researchers, where Gold resolution meshes are utilised for such purpose, however not quite successful due to the transmission effect of high energy photons at their edges as well as the pixeling effect while magnifying the scanned image to secure the edge spread function (ESF) data. In contrast, the use of resolution test target (RTT) and wire mesh grid together with a set of test samples i.e. Stanley blades, Ta, Ti and Si wafer of 100, 300, 15, and 490 micron thickness respectively appeared to be efficient in determining IP pixel size and the resolution of the reader. Two different experiments were conducted using two different targets and lasers of very different performance. The first, was a 15 μm VHS video tape composed of Mylar as carrier film with Fe2O3 and CrO2 powder. Nd:YAG laser of long pulse 800 ps, 50 Hz repetition rate and single shot were utilised. Whereas, the second experiment were conducted on a 9μm C wire and a short pulse 500fs Cerberus single shot laser was used. The results obtained from both experiments were pretty much similar. The imaging plate spatial resolution was measured to be: 3.4 ± 0.2 pixels and a pixel size of 41.26 ± 1.4 μm, whereas the smallest resolvable object visible to the reader (1:1 imaging with magnification factor) was of order 140.3 ± 0.3 microns. This appeared to be worse by a factor of three which indicates the importance of the reader's calibration on a regular basis, and at the same time one has to reconsider any related work and calculation based upon the previous nominal values.

  14. Active tectonics and Holocene versus modern catchment erosion rates at 300 MW Baspa II hydroelectric power plant (NW Himalaya, India)

    Science.gov (United States)

    Draganits, Erich; Grasemann, Bernhard; Gier, Susanne; Hofmann, Christa-Charlotte; Janda, Christoph; Bookhagen, Bodo; Preh, Alexander

    2015-04-01

    The Baspa River is one of the most important tributaries to the Sutlej River in the NW Himalaya (India). Its catchment is 1116 km2 in size, ranges from c. 6400 m asl to 1770 m asl and contains India's largest private hydroelectric facility, the 300 MW Baspa II. Geologically, the hydroelectric installation is located in the Higher Himalayan Crystalline, just above the active Karcham Normal Fault, which is reactivating the Early Miocene Main Central Thrust, one of the principal Himalayan faults. The area is seismically active and mass-movements are common. Around 8200 yrs BP the Baspa was dammed by a rock-avalanche dam, leading to the formation of the originally c. 260 m deep palaeo-lake Sangla palaeo-lake. Detailed sedimentological investigations and radiocarbon dating indicate that the palaeo-lake was completely filled with sediments until c. 5100 yrs BP. This makes the Sangla palaeo-lake to a very rare example of a mass-movement dam with very long duration and its lacustrine sediments represent a valuable archive for geological processes and environmental proxies within the Baspa catchment during the c. 3100 years of its existence - which are the aim of our study. At least 5 levels of soft-sediment deformation have been recorded in the exposed part of the lacustrine sediments of Sangla palaeo-lake, including brecciated laminae, overturned laminae, folds, faults and deformation bands, separated by undeformed deposits. They are interpreted as seismites, indicating at least 5 earthquakes within 2500 years strong enough to cause liquefaction. The 300 MW Baspa II hydro-electric power plant has been built exactly on top of this palaeo-lake. This special location represents a very rare possibility to evaluate the short-term, river load and hydrological parameters measured during the planning and operational stages of Baspa II with the long-term parameters gained from the palaeo-lake sediments from the catchment. This data show that the Mid-Holocene erosion rates of the

  15. Dinosaur tectonics

    DEFF Research Database (Denmark)

    Graversen, Ole; Milàn, Jesper; B. Loope, David

    2007-01-01

    for foot movements and weight distribution in the feet. During the end of the weight-bearing phase of the stride, the weight of the animal was transferred to the front of the digits, creating a rotated disc below the foot that was bounded by an extensional fault at the front and a thrust ramp toward...... of the undertrack. The total length of the tectonic disturbance created by the dinosaur is up to three times that of the original footprint. Early, near-surface cementation gave the substrate the rheological properties necessary for development of the observed structures....

  16. Catalyzed combustion in a flat plate boundary layer. II. Numerical calculations

    Energy Technology Data Exchange (ETDEWEB)

    Schefer, R.; Robben, F.

    1977-09-01

    A computer program has been developed to solve the boundary layer equations for laminar flow over a heated plate with H/sub 2//air combustion. The objectives are to investigate the importance of homogeneous as opposed to catalytic surface reactions during the combustion process, and to determine the roles of heat and mass transfer and their effect on combustion. Results are presented for combustion of H/sub 2//air at an equivalence ratio of 0.1 for flow over a noncatalytic plate at a surface temperature of 1100/sup 0/K. A detailed mechanism involving 8 chemical species and 13 reactions has been used to describe the kinetics. The reactions leading to the initiation of combustion and the effect of the large diffusivity of hydrogen are discussed. The boundary conditions for catalytic surface and a simplified model to account for catalytic wall reaction are formulated. Results are presented for combustion over a catalytic surface and compared with the non-catalytic case.

  17. Late Mesozoic basin and range tectonics and related magmatism in Southeast China

    Directory of Open Access Journals (Sweden)

    Dezi Wang

    2012-03-01

    Full Text Available During the Late Mesozoic Middle Jurassic–Late Cretaceous, basin and range tectonics and associated magmatism representative of an extensional tectonic setting was widespread in southeastern China as a result of Pacific Plate subduction. Basin tectonics consists of post-orogenic (Type I and intra-continental extensional basins (Type II. Type I basins developed in the piedmont and intraland during the Late Triassic to Early Jurassic, in which coarse-grained terrestrial clastic sediments were deposited. Type II basins formed during intra-continental crustal thinning and were characterized by the development of grabens and half-grabens. Graben basins were mainly generated during the Middle Jurassic and were associated with bimodal volcanism. Sediments in half-grabens are intercalated with rhyolitic tuffs and lavas and are Early Cretaceous in age with a dominance of Late Cretaceous–Paleogene red beds. Ranges are composed of granitoids and bimodal volcanic rocks, A-type granites and dome-type metamorphic core complexes. The authors analyzed lithological, geochemical and geochronological features of the Late Mesozoic igneous rock assemblages and proposed some geodynamical constraints on forming the basin and range tectonics of South China. A comparison of the similarities and differences of basin and range tectonics between the eastern and western shores of the Pacific is made, and the geodynamical evolution model of the Southeast China Block during Late Mesozoic is discussed. Studied results suggest that the basin and range terrane within South China developed on a pre-Mesozoic folded belt was derived from a polyphase tectonic evolution mainly constrained by subduction of the western Pacific Plate since the Late Mesozoic, leading to formation of various magmatism in a back-arc extensional setting. Its geodynamic mechanism can compare with that of basin and range tectonics in the eastern shore of the Pacific. Differences of basin and range

  18. History of internal fixation (part 1): early developments with wires and plates before World War II.

    Science.gov (United States)

    Hernigou, Philippe; Pariat, Jacques

    2017-06-01

    Though the date at which an orthopaedic implant was first used cannot be ascertained with any certainty, the fixation of bone fracture using an iron wire was reported for the first time in a French manuscript in 1775. The first techniques of operative fracture treatment were developed at the end of the 18th and in the beginning of the 19th centuries. The use of cerclage wires to fix fractures was the most frequent fixation at this time. The French Berenger-Feraud (1832-1900) had written the first book on internal fixation. However internal fixation of fractures could not become a practical method before Lister had ensured the safety of open reduction and internal fixation in the treatment of fractures. Lister is not only the father of asepsis; he also used metal wires to fix even closed fractures. The first internal fixation by means of a plate and screws was described by Carl Hansmann in 1858 in Hamburg. Nevertheless, Arbuthnot Lane (1892) and Albin Lambotte (1905) are considered to be the founders of this method, which was further developed by Sherman in the first part of the 20th century.

  19. Tectonics and metallogenic provinces

    Science.gov (United States)

    Guild, P.W.

    1983-01-01

    Various theories have been advanced to explain the well-known uneven distribution of metals and ore-deposit types in space and time. Primordial differences in the mantle, preferential concentration of elements in the crust, the prevalence of ore-forming processes at certain times and (or) places, and combinations of one or several of these factors have all been called upon to account for the "metallogenic provinces," which can be defined loosely as regions containing similar deposits of one or a group of metals or minerals. Because many, perhaps most, provinces have complex, multistage origins, the relative importance of inheritance vs. process is still controversial. In recent years the geographic relationship of many geologically young provinces to present-day plate-tectonic positions (accreting or consuming margins, intraplate structures, etc.) has been widely recognized, and the presumption is strong that older provinces had similar relationships to former plates. As most ore deposits resulted from a favorable conjunction of geological processes that are no longer operative, elucidation of their genesis requires reconstruction of the geologic history of the province, with particular emphasis on events coeval with mineralization. Tectonic analysis is an important aspect of this reconstruction; data from orbiting satellites have contributed greatly to this analysis, as the voluminous literature of the past decade testifies. Both the synoptic view of large areas and the ability to emphasize faint contrasts have revealed linear, curvilinear, and circular features not previously recognized from field studies. Some of these undoubtedly reflect basement structures that have contributed to the development, or limit the extent, of metallogenic provinces. Their recognition and delineation will be increasingly valuable to the assessment of resources available and as guides to exploration for the ores needed by future generations. ?? 1983.

  20. Tectonic shortening and coeval volcanism during the Quaternary ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 122; Issue 1. Tectonic shortening ... Abstract. The Northeast Japan arc, a mature volcanic arc with a back-arc marginal basin (Japan Sea), is located on a convergent plate boundary along the subducting Pacific plate and the overriding North American plate. From a ...

  1. Treating Class II patients with removable plates and functional orthopedic appliances-the importance of anterior tooth inclination and direction of growth on treatment outcome.

    Science.gov (United States)

    Hönn, Mirjam; Schneider, Colette; Dietz, Klaus; Godt, Arnim; Göz, Gernot

    2006-07-01

    To determine the influence of physiological growth pattern and anterior tooth inclination on the outcome in Class II patients treated with removable orthodontic plates and functional orthodontic appliances. After recruiting 50 patients with an upper anterior proclination of 1-SN >or= 107 degrees for this retrospective study, another 50 patients with a retroclination of 1-SN appliances was initiated in mixed dentition. Pre- and post-treatment lateral cephalograms were evaluated for each patient. Dento-alveolar analysis showed that the inclination of the upper incisors changed in the direction of the clinical standard value independent of the craniofacial configuration, although full correction using removable orthodontic plates and functional orthodontic appliances was not always achieved. Similarly good treatment outcomes were achieved with regard to overjet and overbite. The lower incisors of all patients were in proclination after treatment. The ANB angle was reduced in both groups. Nevertheless, on average a skeletal Class II persisted in the Class II, Division 2 patients, while Class II, Division 1 patients with horizontal craniofacial configurations attained skeletal Class I. Treatment of Class II patients with removable appliances resulted in differences depending on anterior tooth inclination (Class II, Division 1 and II, Division 2) and craniofacial configuration. These differences must be taken into account during treatment planning. Complete treatment success with regard to sagittal jaw balance is very difficult to achieve with removable orthodontic plates (pre-treatment) and functional orthodontic appliances alone in Class II, Division 1 cases with a vertical craniofacial configuration and generally in Class II, Division 2 cases. A particularly favorable constellation for removable treatment is a Class II, Division 1 situation with a horizontal craniofacial configuration and retroclined or orthognathic mandibular anteriors.

  2. The seismicity of Ethiopia; active plate tectonics

    Science.gov (United States)

    Mohr, P.

    1981-01-01

    "But I tell you, when you look at the way the pieces of the northeastern portion of the African continent seem to fit together, separated by a narrow gulf, you could almost make a believer [in continental drift] of anybody" Astronaut Harrison Schmidt, on the view from Apollo 17.

  3. Marginal inherited structures impact on the oblique convergent N American Plate/ Central Caribbean plate-boundary in the Northern Caribbean. The tectonic evolution since Miocene times based on Haiti data acquired onshore and offshore since 2012- a step toward an ADP Drilling Proposal (Haiti-DRILL).

    Science.gov (United States)

    Ellouz, N.; Hamon, Y.; Deschamps, R.; Battani, A.; Wessels, R.; Boisson, D.; Prepetit, C.; Momplaisir, R.

    2017-12-01

    Since Early Paleogene times, the North Caribbean plate is colliding obliquely with the south continental part of the old N. American Margins, which is represented by various segments from West to East, inherited from Jurassic times. Location, amount of displacement, rotation and the structural deformation of these margin segments, resulting from the dislocation of the continental N American margin, are not clearly yet established. At present, the plate limits are marked either by two left lateral faults west and inside Haiti (OSF in the North and EPGF in the South), oblique collision front (further west in Cuba), oblique subducted segments (to the East, Porto-Rico). From our recent works operated both offshore (Haiti-SIS and Haiti-BGF surveys 2012-2015) and onshore (field campaigns 2013-2017) in Haitian zone, the position of the present-day and paleo major limits have been redefined. These paleolimits have been reconstructed up to early Miocene times, based on: restoration of regional structural cross-sections, sedimentology and on paleoenvironement studies. In a preliminary way, we analyzed the complexity of the tectonic heritage with possible nature, heterogeneity of the crustal fragments and associated margins close to Haiti (age, structure, environment, location of the dislocated blocks through times) which profoundly impact the partitioning of the deformation along this complex transformed margin. The change in the structure wavelength, decollement level variations are primary constraints in the restoration of the main units and do impose a deep connection along specific segments either related to strike-slip or to splay faults. The asymmetry on the repartition of the fault activity tend to prove that the past motion related to "EPGF transfer zone" is mainly partitioned in Haiti to the North of the present-day EPGF position. At present, these results are still coherent with the distribution of the aftershoks registered after 2010, and with the present

  4. Inversion tectonics of the benue trough | Mamah | Global Journal of ...

    African Journals Online (AJOL)

    The Benue Trough, an aulacogen at the entrant of the Gulf of Guinea in Nigeria, has been historically studied from the concepts of ortho-mio-eu-geosynclines at outcrops and in the subsurface. Its structural evolution reveals a tectonic scenario compatible with Plate tectonic evolution of the Atlantic Ocean. Spreading was ...

  5. Continental tectonics and continental kinetics

    International Nuclear Information System (INIS)

    Allegre, C.J.; Jaupart, C.; Paris-7 Univ., 75

    1985-01-01

    We present a model of continental growth which combines the results of geochemical studies and tectonic ideas about the evolution of continents through geological time. The process of continental growth is mainly controlled by surface phenomena. Continental material is extracted from the mantle along subduction zones at the periphery of oceans, and is destroyed in collision zones where it is remobilized and made available for subduction. We derive an equation for S, the portion of the Earth's surface occupied by continents, which reads as follows: dS/dt=a . √(1-S)-b . S. Coefficients a and b depend on the geometry of plates, on their number and on their velocities. We assume that they decrease exponentially with time with the same time-scale α. This model satisfies both geochemical and tectonic constraints, and allows the integration of several current observations in a single framework. (orig.)

  6. The alternative concept of global tectonics

    Science.gov (United States)

    Anokhin, Vladimir; Kholmyansky, Mikhael

    2016-04-01

    The existing plate tectonic paradigm becomes more questionable in relation to the new facts of the Earth. The most complete to date criticism of plate tectonics provisions contained in the article (Pratt, 2000). Authors can recall a few facts that contradict the idea of long-range movement of plates: - The absence of convection cells in the mantle, detected by seismic tomography; - The presence of long-lived deep regmatic network in the crust, not distorted by the movement of plates; - The inability of linking the global geometry of the of mutual long-distance movement of plates. All this gives reason to believe that correct, or at least a satisfactory concept of global tectonics are not exist now. After overcoming the usual inertia of thinking the plate paradigm in the foreseeable future will replace by different concept, more relevant as the observable facts of the Earth and the well-known physical laws. The authors suggest that currently accumulated sufficient volume of facts and theoretical ideas for the synthesis of a new general hypothesis of the structure and dynamics of the Earth. Analysis of the existing tectonic theory suggests that most of their provisions are mutually compatible. Obviously, plume tectonics perfectly compatible with any of classical models. It contradicts the only plate tectonics (movement of hot spots in principle not linked either with each other or with the general picture of the plate movements, the presence of mantle convection and mantle streams are mutually exclusive, and so on). The probable transfer of the heated material down up within the Earth may occur in various forms, the simplest of which (and, consequently, the most probable) are presented plumes. The existence in the mantle numerous large volumes of decompressed substances (detected seismic tomography), can be correlated with the bodies of plumes at different stages of uplift. Plumes who raise to the bottom of the lithosphere, to spread out to the sides and form a set

  7. Zn(II Removal from Wastewater by Electrocoagulation/Flotation Method using New Configuration of a Split-Plate Airlift Electrochemical Reactor

    Directory of Open Access Journals (Sweden)

    Saad H. Ammar

    2018-01-01

    Full Text Available In this paper, split-plate airlift electrochemical reactor as an apparatus with new configuration for wastewater treatment was provided. Two aluminum plates were fixed inside the reactor and present two functions; first it works as split plates for internal loop generation of the airlift system (the zone between the two plates acts as riser while the other two zones act as downcomer and second it works as two electrodes for electrocoagulation process. Simulated wastewater contaminated with zinc ions was used to test the performance of this apparatus for zinc removal by studying the effect of different experimental variables such as initial concentration of zinc (50-800 ppm, electrical current density (2.67-21.4 mA/cm2, initial pH (3-11, air flowrate (12-50 LPH, and implicitly the electrocoagulation time. The results have shown the applicability of this split-plate airlift reactor as electrocoagulation cell in the treatment of wastewater such as wastewater containing Zink ions. The Zink removal percent was shown to increase upon increasing the current density and the electrolysis time. Also best removal percent was achieved in the initial pH range between 7 and 9. The minimum electrocoagulation time required for removal of ≥ 90% of Zn(II decreases from 90 to 22 min when operating current density increases from 2.67 to 21.4 mA/cm2.

  8. Tectonics of montage

    DEFF Research Database (Denmark)

    Bundgaard, Charlotte

    2013-01-01

    We build in accordance with specific contemporary conditions, defined by production methods, construction and materials as well as ethics, meaning and values. Exactly this relationship between the work as such and the conditions behind its coming into being is a crucial point. The simultaneity of...... and the creation of meaning forms the core of tectonics. So tectonic thinking is not only about portraying a constructional logic. Tectonics is to create material realities that reveal narrative meaning. Tectonics is to construct with cultural references....

  9. Andean tectonics: Implications for Satellite Geodesy

    Science.gov (United States)

    Allenby, R. J.

    1984-09-01

    Current knowledge and theories of large scale Andean tectonics as they relate to site planning for the NASA Crustal Dynamics Program's proposed high precision geodetic measurements of relative motions between the Nazca and South American plates are summarized. The Nazca Plate and its eastern margin, the Peru-Chile Trench, is considered a prototype plate marked by rapid motion, strong seismicity and well defined boundaries. Tectonic activity across the Andes results from the Nazca Plate subducting under the South American plate in a series of discrete platelets with different widths and dip angles. This in turn, is reflected in the tectonic complexity of the Andes which are a multitutde of orogenic belts superimposed on each other since the Precambrian. Sites for Crustal Dynamics Program measurements are being located to investigate both interplate and extraplate motions. Observing operations have already been initiated at Arequipa, Peru and Easter Island, Santiago and Cerro Tololo, Chile. Sites under consideration include Iquique, Chile; Oruro and Santa Cruz, Bolivia; Cuzco, Lima, Huancayo and Bayovar, Peru; and Quito and the Galapagos Islands, Ecuador. Based on scientific considerations, Santa Cruz, Huancayo (or Lima), Quito and the Galapagos Islands should be replaced by Isla San Felix, Chile; Brazilia or Petrolina, Brazil; and Guayaquil, Ecuador. If resources permit, additional important sites would be Buenaventura and Villavicencio or Puerto La Concordia, Colombia; and Mendoza and Cordoba, Argentina.

  10. Quaternary tectonics of recent basins in northwestern Armenia

    Science.gov (United States)

    Trifonov, V. G.; Shalaeva, E. A.; Saakyan, L. Kh.; Bachmanov, D. M.; Lebedev, V. A.; Trikhunkov, Ya. I.; Simakova, A. N.; Avagyan, A. V.; Tesakov, A. S.; Frolov, P. D.; Lyubin, V. P.; Belyaeva, E. V.; Latyshev, A. V.; Ozherelyev, D. V.; Kolesnichenko, A. A.

    2017-09-01

    New data on the stratigraphy, faults, and formation history of lower to middle Pleistocene rocks in Late Cenozoic basins of northwestern Armenia are presented. It has been established that the low-mountain topography created by tectonic movements and volcanic activity existed in the region by the onset of the Pleistocene. The manifestations of two geodynamic structure-forming factors became clear in Pleistocene: (i) collisional interaction of plates due to near-meridional compression and (ii) deep tectogenesis and magma formation expressed in the distribution of vertical movements and volcanism. The general uplift of the territory, which was also related to deep processes, reached 350-500 m in basins and 600-800 m in mountain ranges over the last 0.5 Ma. The early Pleistocene ( 1.8 Ma) low- and medium-mountain topography has been reconstructed by subtraction of the latest deformations and uplift of the territory. Ancient human ancestry appeared at that time.

  11. Introduction to Plate Boundaries and Natural Hazards

    NARCIS (Netherlands)

    Duarte, João C.; Schellart, Wouter P.

    2016-01-01

    A great variety of natural hazards occur on Earth, including earthquakes, volcanic eruptions, tsunamis, landslides, floods, fires, tornadoes, hurricanes, and avalanches. The most destructive of these hazards, earthquakes, tsunamis, and volcanic eruptions, are mostly associated with tectonic plate

  12. Fresnel zone plate telescopes for X-ray imaging II: numerical simulations with parallel and diverging beams

    Science.gov (United States)

    Palit, Sourav; Chakrabarti, Sandip Kumar; Debnath, Dipak; Rao, A. R.; Nandi, Anuj; Yadav, Vipin K.; Girish, V.

    2009-12-01

    We present the results of simulations of shadows cast by a zone plate telescope which may have one to four pairs of zone plates. From the shadows we reconstruct the images under various circumstances. We discuss physical basis of the resolution of the telescope and demonstrate this by our simulations. We allow the source to be at a finite distance (diverging beam) as well as at an infinite distance (parallel beam) and show that the resolution is worsened when the source is nearby. By reconstructing the zone plates in a way that both the zone plates subtend the same solid angles at the source, we obtain back high resolution even for sources at a finite distance. We present simulated results for the observation of the galactic center and show that the sources of varying intensities may be reconstructed with accuracy. Results of these simulations would be of immense use in interpreting the X-ray images from recently launched CORONAS-PHOTON satellite.

  13. The tectonics of Mercury

    International Nuclear Information System (INIS)

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

    1988-01-01

    The probable tectonic history of Mercury and the relative sequence of events are discussed on the basis of data collected by the Mariner-10 spacecraft. Results indicate that Mercury's tectonic activity was confined to its early history; its endogenic activity was principally due to a small change in the shape of its lithosphere, caused by tidal despinning, and a small change in area caused by shrinkage due to cooling. Exogenic processes, in particular the impact activity, have produced more abundant tectonic features. Many features associated with the Caloris basin are due to loading of Mercury's thick lithosphere by extrusive lavas or subsidence due to magma withdrawal. It is emphasized that tectonic features observed on Mercury yield insight into the earliest tectonic events on planets like Mars and, perhaps, the earth, where subsequent events obscured or erased the most ancient tectonic records

  14. The Tectonic Practice

    DEFF Research Database (Denmark)

    Schmidt, Anne Marie Due

    has the consequence that it is difficult to create architecture where the technical concerns are an inherent part of the architectural expression. The aim of the thesis is to discuss the role of digital tools in overcoming the distance between the professional specializations and thereby support...... a tectonic practice. The project develops a framework to understand the role of digital tools in the tectonic practice from and discusses how and in which areas the tectonic practice could become supported by digital tools....

  15. Dynamics and stress field of the Eurasian plate: A combined lithosphere-mantle approach

    NARCIS (Netherlands)

    Ruckstuhl, K.N.|info:eu-repo/dai/nl/304848743

    2012-01-01

    This thesis presents a new combined lithosphere-mantle modeling approach to the dynamics of individual tectonic plates. This approach incorporates tractions from convective mantle flow modeling into a detailed analysis of the forces acting on a tectonic plate. Mechanical equilibrium of the plate is

  16. Seismic link at plate boundary

    Indian Academy of Sciences (India)

    transfer between two major faults, and parallel to the geothermal area extension. 1. Introduction. Plate boundaries are the zones where most earth dynamics are focussed. The complexity of tectonic boundaries draws attention to them as the largest earthquakes are felt in these areas and they elicit the natural hazard of ...

  17. Active tectonics and earthquake potential of the Myanmar region

    OpenAIRE

    Wang, Yu; Sieh, Kerry; Tun, Soe Thura; Lai, Kuang-Yin; Myint, Than

    2014-01-01

    This paper describes geomorphologic evidence for the principal neotectonic features of Myanmar and its immediate surroundings. We combine this evidence with published structural, geodetic, and seismic data to present an overview of the active tectonic architecture of the region and its seismic potential. Three tectonic systems accommodate oblique collision of the Indian plate with Southeast Asia and extrusion of Asian territory around the eastern syntaxis of the Himalayan mountain range. Subd...

  18. Scaling and spatial complementarity of tectonic earthquake swarms

    KAUST Repository

    Passarelli, Luigi

    2017-11-10

    Tectonic earthquake swarms (TES) often coincide with aseismic slip and sometimes precede damaging earthquakes. In spite of recent progress in understanding the significance and properties of TES at plate boundaries, their mechanics and scaling are still largely uncertain. Here we evaluate several TES that occurred during the past 20 years on a transform plate boundary in North Iceland. We show that the swarms complement each other spatially with later swarms discouraged from fault segments activated by earlier swarms, which suggests efficient strain release and aseismic slip. The fault area illuminated by earthquakes during swarms may be more representative of the total moment release than the cumulative moment of the swarm earthquakes. We use these findings and other published results from a variety of tectonic settings to discuss general scaling properties for TES. The results indicate that the importance of TES in releasing tectonic strain at plate boundaries may have been underestimated.

  19. WAVE TECTONICS OF THE EARTH

    Directory of Open Access Journals (Sweden)

    Tatiana Yu. Tveretinova

    2010-01-01

    Full Text Available In the Earth's lithosphere, wavy alternation of positive and negative heterochronous structures is revealed; such structures are variable in ranks and separated by vergence zones of fractures and folds. In the vertical profile of the lithosphere, alternating are layers characterized by relatively plastic or fragile rheological properties and distinguished by different states of stress. During the Earth’s evolution, epochs of compression and extension are cyclically repeated, including planetary-scale phenomena which are manifested by fluctuating changes of the planet’s volume. Migration of geological and geophysical (geodynamic processes takes place at the Earth's surface and in its interior. The concept of the wave structure and evolution of the Earth's lithosphere provides explanations to the abovementioned regularities. Wavy nature of tectonic structures of the lithosphere, the cyclic recurrence of migration and geological processes in space and time can be described in terms of the multiple-order wave geodynamics of the Earth's lithosphere that refers to periodical variations of the state of stress. Effects of structure-forming tectonic forces are determined by «interference» of tangential and radial stresses of the Earth. The tangential stresses, which occur primarily due to the rotational regime of the planet, cause transformations of the Earth’s shape, redistributions of its substance in depths, the westward drift of the rock mass in its upper levels, and changes of structural deformation plans. The radial stresses, which are largely impacted by gravity, determine the gravitational differentiation of the substance, vertical flattening and sub-horizontal flow of the rock masses, and associated fold-rupture deformation. Under the uniform momentum geodynamic concept proposed by [Vikulin, Tveritinova, 2004, 2005, 2007, 2008], it is possible to provide consistent descriptions of seismic and volcanic, tectonic and geological processes

  20. Discriminating Between Tectonic and Climatic Controls on Early Hominin Paleoenvironments From the Koobi Fora Region, Northeastern Turkana Basin, Kenya: Part II

    Science.gov (United States)

    Quinn, R. L.; Lepre, C. J.

    2004-12-01

    Global climate is often elected as a catalyst for environmental change and used to characterize selective pressures acting on Plio-Pleistocene African hominins. Vrba's Habitat Theory (1992) and Pott's Variability Selection (1998) credit mammalian evolutionary pattern and process to global climate regulated by orbital forcing. Feibel (1999: 276) argues the need for a middle ground, tethering the "global-scale climatic phenomena" to "environmental change, habitat shift, and biotic evolution" and offers the basin as a scale for analysis. Feibel suggests that all basins are not created equal, and will respond to climate change with different sensitivities and thresholds. As such, interpretations of climate proxies must account for differences in basin size, climatic regime(s), topography, geology, and water availability when drawing relationships to global phenomena. Here we examine pedogenic carbonate isotopes (d13C, d18O) from the Plio-Pleistocene Koobi Fora Region to elucidate the differential influences of climate, tectonics, and deposition on ecological factors of early hominin evolution in the northeastern Turkana Basin of Kenya. One of the richest Plio-Pleistocene fossil localities in Africa, Koobi Fora has served as a setting for hominin evolution between 4.0 and 1.0 Ma. Numerous paleosols, stratigraphically controlled by tuffaceous marker beds, are preserved in the Plio-Pleistocene sediments of the Koobi Fora Formation. Cerling and others (1988) and Wynn (2000) conducted isotopic studies of pedogenic carbonates from the Plio-Pleistocene Omo Group deposits of the Turkana Basin. With these data Wynn (2004) demonstrates stepwise d13C shifts over the last 4.0 Ma, with marked events at 2.5 and 1.8 Ma, and interprets increased aridity on a basin scale due to comparable records on the east and west side of present Lake Turkana. In this study, we increased the sample size of the current database and conducted widespread sampling of synchronous lateral horizons in the

  1. Tectonic predictions with mantle convection models

    Science.gov (United States)

    Coltice, Nicolas; Shephard, Grace E.

    2018-04-01

    Over the past 15 yr, numerical models of convection in Earth's mantle have made a leap forward: they can now produce self-consistent plate-like behaviour at the surface together with deep mantle circulation. These digital tools provide a new window into the intimate connections between plate tectonics and mantle dynamics, and can therefore be used for tectonic predictions, in principle. This contribution explores this assumption. First, initial conditions at 30, 20, 10 and 0 Ma are generated by driving a convective flow with imposed plate velocities at the surface. We then compute instantaneous mantle flows in response to the guessed temperature fields without imposing any boundary conditions. Plate boundaries self-consistently emerge at correct locations with respect to reconstructions, except for small plates close to subduction zones. As already observed for other types of instantaneous flow calculations, the structure of the top boundary layer and upper-mantle slab is the dominant character that leads to accurate predictions of surface velocities. Perturbations of the rheological parameters have little impact on the resulting surface velocities. We then compute fully dynamic model evolution from 30 and 10 to 0 Ma, without imposing plate boundaries or plate velocities. Contrary to instantaneous calculations, errors in kinematic predictions are substantial, although the plate layout and kinematics in several areas remain consistent with the expectations for the Earth. For these calculations, varying the rheological parameters makes a difference for plate boundary evolution. Also, identified errors in initial conditions contribute to first-order kinematic errors. This experiment shows that the tectonic predictions of dynamic models over 10 My are highly sensitive to uncertainties of rheological parameters and initial temperature field in comparison to instantaneous flow calculations. Indeed, the initial conditions and the rheological parameters can be good enough

  2. Tectonic Vocabulary & Materialization

    DEFF Research Database (Denmark)

    Hvejsel, Marie Frier; Beim, Anne; Bundgaard, Charlotte

    2015-01-01

    By referring to the fundamental question of how we unite aesthetics and technology – tectonic theory is necessarily a focal point in the development of the architectural discipline. However, a critical reconsideration of the role of tectonic theory seems necessary when facing the present everyday...... architectural practice. In this matter the paper focuses on the need to juxtapose theoretical studies, to bring the present vocabulary of the tectonic further, as well as to spur further practical experiments enabling theory to materialize in the everyday of the current practice....

  3. Deformation of the Northwestern Okhotsk Plate: How is it happening?

    OpenAIRE

    Hindle, D.; Fujita, K.; Mackey, K.

    2009-01-01

    The Eurasia (EU) – North America (NA) plate boundary zone across Northeast Asia still presents many open questions within the plate tectonic paradigm. Constraining the geometry and number of plates or microplates present in the plate boundary zone is especially difficult because of the location of the EU-NA euler pole close to or even upon the EU-NA boundary. One of the major challenges remains the geometry of the Okhotsk plate (OK). whose northwestern portion terminates on ...

  4. Incorporating Cutting Edge Scientific Results from the Margins-Geoprisms Program into the Undergraduate Curriculum, Rupturing Continental Lithosphere Part II: Introducing Euler Poles Using Baja-North America Relative Plate Motion Across the Gulf of California

    Science.gov (United States)

    Loveless, J. P.; Bennett, S. E. K.; Cashman, S. M.; Dorsey, R. J.; Goodliffe, A. M.; Lamb, M. A.

    2014-12-01

    The NSF-MARGINS Program funded a decade of research on continental margin processes. The NSF-GeoPRISMS Mini-lesson Project, funded by NSF-TUES, is designed to integrate the significant findings from the MARGINS program into open-source college-level curriculum. The Gulf of California (GOC) served as the focus site for the Rupturing Continental Lithosphere (RCL) initiative, which addressed several scientific questions: What forces drive rift initiation, localization, propagation and evolution? How does deformation vary in time and space, and why? How does crust evolve, physically and chemically, as rifting proceeds to sea-floor spreading? What is the role of sedimentation and magmatism in continental extension? We developed two weeks of curriculum, including lectures, labs, and in-class activities that can be used as a whole or individually. This component of the curriculum introduces students to the Euler pole description of relative plate motion (RPM) by examining the tectonic interactions of the Baja California microplate and North American plate. The plate boundary varies in rift obliquity along strike, from highly oblique and strike-slip dominated in the south to slightly less oblique and with a larger extensional component in the north. This Google Earth-based exercise provides students with a visualization of RPM using small circle contours of the local direction and magnitude of Baja-North America movement on a spherical Earth. Students use RPM to calculate the fault slip rates on transform, normal, and oblique-slip faults and examine how the varying faulting styles combine to accommodate RPM. MARGINS results are integrated via comparison of rift obliquity with the structural style of rift-related faults around the GOC. We find this exercise to fit naturally into courses about plate tectonics, geophysics, and especially structural geology, given the similarity between Euler pole rotations and stereonet-based rotations of structural data.

  5. The effect of plate-scale rheology and plate interactions on intraplate seismicity

    Science.gov (United States)

    So, Byung-Dal; Capitanio, Fabio A.

    2017-11-01

    We use finite element modeling to investigate on the stress loading-unloading cycles and earthquakes occurrence in the plate interiors, resulting from the interactions of tectonic plates along their boundary. We model a visco-elasto-plastic plate embedding a single or multiple faults, while the tectonic stress is applied along the plate boundary by an external loading visco-elastic plate, reproducing the tectonic setting of two interacting lithospheres. Because the two plates deform viscously, the timescale of stress accumulation and release on the faults is self-consistently determined, from the boundary to the interiors, and seismic recurrence is an emerging feature. This approach overcomes the constraints on recurrence period imposed by stress (stress-drop) and velocity boundary conditions, while here it is unconstrained. We illustrate emerging macroscopic characteristics of this system, showing that the seismic recurrence period τ becomes shorter as Γ and Θ decreases, where Γ =ηI /ηL, the viscosity ratio of the viscosities of the internal fault-embedded to external loading plates, respectively, and Θ =σY /σL the stress ratio of the elastic limit of the fault to far-field loading stress. When the system embeds multiple, randomly distributed faults, stress transfer results in recurrence period deviations, however the time-averaged recurrence period of each fault show the same dependence on Γ and Θ, illustrating a characteristic collective behavior. The control of these parameters prevails even when initial pre-stress was randomly assigned in terms of the spatial arrangement and orientation on the internal plate, mimicking local fluctuations. Our study shows the relevance of macroscopic rheological properties of tectonic plates on the earthquake occurrence in plate interiors, as opposed to local factors, proposing a viable model for the seismic behavior of continent interiors in the context of large-scale, long-term deformation of interacting tectonic

  6. French RSE-M and RCC-MR code appendices for flaw analysis: Presentation of the fracture parameters calculation-Part II: Cracked plates

    Energy Technology Data Exchange (ETDEWEB)

    Marie, S. [CEA Saclay, DEN/DM2S/SEMT/LISN, 91191 Gif sur Yvette Cedex (France)], E-mail: stephane.marie@cea.fr; Chapuliot, S.; Kayser, Y. [CEA Saclay, DEN/DM2S/SEMT/LISN, 91191 Gif sur Yvette Cedex (France); Lacire, M.H. [CEA Saclay, DEN/DDIN, 91191 Gif sur Yvette Cedex (France); Drubay, B. [CEA Saclay, DEN/DM2S/SEMT/LISN, 91191 Gif sur Yvette Cedex (France); Barthelet, B. [EDF/EPN, Site Cap Ampere, 1 place Pleyel 93207, Saint Denis Cedex 1 (France); Le Delliou, P. [EDF Pole Industrie-Division R and D, Site des Renardieres, Route de Sens, Ecuelles, 77250 Moret sur Loing Cedex (France); Rougier, V. [EDF/UTO SIS/GAM, 6, avenue Montaigne, 93192 Noisy le Grand (France); Naudin, C. [EDF/SEPTEN, 12-14, avenue Dutrievoz, 69628 Villeurbanne Cedex (France); Gilles, P.; Triay, M. [AREVA ANP, Tour AREVA, 92084 Paris La Defense Cedex 16 (France)

    2007-10-15

    French nuclear codes include flaw assessment procedures: the RSE-M Code 'Rules for In-service Inspection of Nuclear Power Plant Components' and the RCC-MR code 'Design and Construction rules for mechanical components of FBR nuclear islands and high temperature applications'. An important effort of development of these analytical methods has been made for the last 10 years in the frame of a collaboration between CEA, EDF and AREVA-NP, and in the frame of R and D actions involving CEA and IRSN. These activities have led to a unification of the common methods of the two codes. The calculation of fracture mechanics parameters, and in particular the stress intensity factor K{sub I} and the J integral, has been widely developed for industrial configurations. All the developments have been integrated in the 2005 edition of RSE-M and in the 2007 edition of RCC-MR. This series of articles is composed of 5 parts: the first part presents an overview of the methods proposed in the RCC-MR and RSE-M codes. Parts II-IV provide compendia for specific components. The geometries are plates (part II), pipes (part III) and elbows (part IV). Finally, part V presents the validation elements of the methods, with details on the process followed for the development and evaluation of the accuracy of the proposed analytical methods. This second article in the series presents all details for the stress intensity factor and J calculations for cracked plates. General data applicable for all defect geometries are first presented, and then, available defect geometries where compendia for K{sub I} and {sigma}{sub ref} calculation are provided are given.

  7. French RSE-M and RCC-MR code appendices for flaw analysis: Presentation of the fracture parameters calculation-Part II: Cracked plates

    International Nuclear Information System (INIS)

    Marie, S.; Chapuliot, S.; Kayser, Y.; Lacire, M.H.; Drubay, B.; Barthelet, B.; Le Delliou, P.; Rougier, V.; Naudin, C.; Gilles, P.; Triay, M.

    2007-01-01

    French nuclear codes include flaw assessment procedures: the RSE-M Code 'Rules for In-service Inspection of Nuclear Power Plant Components' and the RCC-MR code 'Design and Construction rules for mechanical components of FBR nuclear islands and high temperature applications'. An important effort of development of these analytical methods has been made for the last 10 years in the frame of a collaboration between CEA, EDF and AREVA-NP, and in the frame of R and D actions involving CEA and IRSN. These activities have led to a unification of the common methods of the two codes. The calculation of fracture mechanics parameters, and in particular the stress intensity factor K I and the J integral, has been widely developed for industrial configurations. All the developments have been integrated in the 2005 edition of RSE-M and in the 2007 edition of RCC-MR. This series of articles is composed of 5 parts: the first part presents an overview of the methods proposed in the RCC-MR and RSE-M codes. Parts II-IV provide compendia for specific components. The geometries are plates (part II), pipes (part III) and elbows (part IV). Finally, part V presents the validation elements of the methods, with details on the process followed for the development and evaluation of the accuracy of the proposed analytical methods. This second article in the series presents all details for the stress intensity factor and J calculations for cracked plates. General data applicable for all defect geometries are first presented, and then, available defect geometries where compendia for K I and σ ref calculation are provided are given

  8. Litho-tectonic mapping of the North Afar region from Sentinel-2A multispectral imagery and ALOS AW3D30 digital elevation data: Controls on Danakil-Nubia plate motion between the Erta'Ale ridge and the Gulf of Zula

    Science.gov (United States)

    Hartnady, Chris; Hartnady, Michael; Wise, Edward; Blake, Dylan; McGibbon, David; Hay, E. Rowena

    2017-04-01

    The Danakil Depression in the North Afar region of Ethiopia reaches elevations deeper than 120 m below sea level and contains a Pleistocene-Holocene evaporite sequence currently investigated for potash mineral deposits. Separated from the main Ethiopian escarpment by the Dogua horst mountains, the asymmetric half-graben is bordered on its western (Nubian) side by the active, normal Main Danakil Rift-border Fault (MDRF). Above the MDRF, a series of piedmont alluvial fans (bajadas) fringes the Dogua Horst, emanating from a series of wadi catchments between the larger perennial rivers (Ragali, Saba) that drain from the high (>2000 m) Ethiopian Plateau. On its eastern side, the Danakil block contains Proterozoic-Palaeozoic sequences correlated with similar units in the Dogua range, and forms a microplate rotating independently between the larger Nubian and Arabian plates (McClusky et al., 2010). An understanding of the sedimentary and tectonic evolution of the Danakil-Nubia (DA-NU) plate system is crucial to the beneficial development of fresh groundwater resources and to an assessment of seismotectonic and volcanic geohazards in the area. Between the Mt Alid caldera in the Dandeiro graben and the Erta'Ale crater in the south Danakil, the rate of present-day DA-NU motion is 10.9 - 13.5 mm/yr, with direction azimuths N106E- N096E (after Schettino et al., 2016). DA-NU relative motion is focussed along the east-dipping MDRF in the Danakil but switches to an eastern (west-dipping) rift-border normal fault in the Dandiero, a northward extension of the Renda-Maglalla-Coma graben, separating the Dogua Horst from the main part of the NU plate. This change in rifting asymmetry occurs across a WNW/ESE-striking zone of basement faulting that terminates the Dogua Horst and functions as a left-stepping proto-transform fault zone, across the NNW direction of DA-NU proto-rift propagation. From 13-channel multispectral data of the European Space Agency satellite Sentinel-2A, a false

  9. Tectonic evolution of Tarim basin in Cambrian–Ordovician and its ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 125; Issue 2 ... In order to find the impact of regional tectonic evolution of Tarim basin on the inside distribution of sedimentary facies and reservoir development, this paper, based on the research of plate-tectonic evolution of Tarim basin, conducts an in-depth ...

  10. Tectonic Theory and Practice

    DEFF Research Database (Denmark)

    Frier, Marie; Fisker, Anna Marie; Kirkegaard, Poul Henning

    2010-01-01

    defined by Semper as a constructive precondition, a theory for developing a novel tectonic relation between home and system opens up. As a research result the paper suggests a practical spatial exploitation of the actual prefab construction, defining interiority not solely as a visual occupation......’ is an example of this sensuous interior transformation of a house into a home, a level of detailing which is, however, seldom represented in the prefabricated house. Consequently, this paper investigates whether interiority can be developed as a tectonic theory and design principle for uniting home and system......Since the first optimistic originally Modernist prefab visions were formulated there has been, and are still, challenges to be overcome in order to fulfill the increasing need for fast, precise and economically produced homes. The tectonic need to transform a home, into a system of joints...

  11. Transcultural Tectonic Connections

    DEFF Research Database (Denmark)

    Carter, Adrian

    2014-01-01

    This paper presents an understanding of Jørn Utzon, as one of the most profound exponents of a transcultural and tectonic approach to modern architecture in the late twentieth century. The paper will examine the sources of inspiration, intersections and connections in Utzon’s architecture; which...... of cloud formations over a Hawaiian beach, when Utzon was teaching at the University of Hawai’i at Manoa. It is this ability to make connections and translate ideas from one context to another with poetic architectural vision and tectonic integrity, that is at the heart of Utzon’s architecture Together...... with such original unrealised projects as the subterranean Silkeborg Art Museum, Utzon’s work embodies a visionary approach to architecture that is site specific and poetic, tectonic and humane; informed by a profound appreciation of nature and diversity of human cultures, as sources of inspiration and analogy...

  12. Tectonic environments and rare metal mineralization in pegmatites ...

    African Journals Online (AJOL)

    The discrimination diagrams show that the pegmatites were mainly emplaced in tectonic environments similar to those of syn-collisional granites (Syn COG) and within plate granites (WPG). Volcanic arc environment was not pronounced. The emplacement of the pegmatites was structurally controlled by the predominantly ...

  13. Fission-track evidence of tectonic evolution in the northwestern ...

    Indian Academy of Sciences (India)

    track evidence of tectonic evolution in the ... The later (1.2–32.0 Ma) tectonothermal event resulted from further collision of the Indian and Eurasian plates along the Yarlung Tsangpo suture zone. Strata in the Qaidam Basin were further ...

  14. Cold plate

    Energy Technology Data Exchange (ETDEWEB)

    Marroquin, Christopher M.; O' Connell, Kevin M.; Schultz, Mark D.; Tian, Shurong

    2018-02-13

    A cold plate, an electronic assembly including a cold plate, and a method for forming a cold plate are provided. The cold plate includes an interface plate and an opposing plate that form a plenum. The cold plate includes a plurality of active areas arranged for alignment over respective heat generating portions of an electronic assembly, and non-active areas between the active areas. A cooling fluid flows through the plenum. The plenum, at the non-active areas, has a reduced width and/or reduced height relative to the plenum at the active areas. The reduced width and/or height of the plenum, and exterior dimensions of cold plate, at the non-active areas allow the non-active areas to flex to accommodate surface variations of the electronics assembly. The reduced width and/or height non-active areas can be specifically shaped to fit between physical features of the electronics assembly.

  15. Plating laboratory

    International Nuclear Information System (INIS)

    Seamster, A.G.; Weitkamp, W.G.

    1984-01-01

    The lead plating of the prototype resonator has been conducted entirely in the plating laboratory at SUNY Stony Brook. Because of the considerable cost and inconvenience in transporting personnel and materials to and from Stony Brook, it is clearly impractical to plate all the resonators there. Furthermore, the high-beta resonator cannot be accommodated at Stony Brook without modifying the set up there. Consequently the authors are constructing a plating lab in-house

  16. Extrusive and Intrusive Magmatism Greatly Influence the Tectonic Mode of Earth-Like Planets

    Science.gov (United States)

    Lourenco, D.; Tackley, P. J.; Rozel, A.; Ballmer, M.

    2017-09-01

    Plate tectonics on Earth-like planets is typically modelling using a strongly temperature-dependent visco-plastic rheology. Previous analyses have generally focussed on purely thermal convection. However, we have shown that the influence of compositional heterogeneity in the form of continental or oceanic crust can greatly influence plate tectonics by making it easier (i.e. it occurs at a lower yield stress or friction coefficient). Here we present detailed results on this topic, in particular focussing on the influence of intrusive vs. extrusive magmatism on the tectonic mode.

  17. Tectonic vision in architecture

    DEFF Research Database (Denmark)

    Beim, Anne

    1999-01-01

    By introducing the concept; Tectonic Visions, The Dissertation discusses the interrelationship between the basic idea, the form principles, the choice of building technology and constructive structures within a given building. Includes Mies van der Rohe, Le Corbusier, Eames, Jorn Utzon, Louis Kahn...

  18. Cretacic tectonics in Uruguay

    International Nuclear Information System (INIS)

    Gomez Rifas, C.

    2012-01-01

    This work is about Cretacic tectonics in Uruguay, this formation is characterized by high level cortex because the basament is cratonized since Middle Devonian. There were formed two main grabens such as Santa Lucia and Mirim-Pelotas which are filled with basalt and sediments.

  19. Tectonic vision in architecture

    DEFF Research Database (Denmark)

    Beim, Anne

    1999-01-01

    By introducing the concept; Tectonic Visions, The Dissertation discusses the interrelationship between the basic idea, the form principles, the choice of building technology and constructive structures within a given building. Includes Mies van der Rohe, Le Corbusier, Eames, Jorn Utzon, Louis Kah...

  20. Tectonic design strategies

    DEFF Research Database (Denmark)

    Beim, Anne

    2000-01-01

    The tectonic realm of architecture concerns elements such as intentions and meaning - the process of translating visions into physical constructions - as well as the actual realization of building structures. This field of architectural making has been characterized by Kenneth Frampton as the poe...

  1. Tectonics of montage

    DEFF Research Database (Denmark)

    Bundgaard, Charlotte

    2013-01-01

    in architecture. The Italian architectural theorist, Marco Frascari describes the concepts 'construction' and 'construing' as inherent dimensions of tectonics, and according to him both dimensions have to be present in meaningful architecture. This close link between the creation of concrete solutions...

  2. Tectonic feedback and the earthquake cycle

    Science.gov (United States)

    Lomnitz, Cinna

    1985-09-01

    The occurrence of cyclical instabilities along plate boundaries at regular intervals suggests that the process of earthquake causation differs in some respects from the model of elastic rebound in its simplest forms. The model of tectonic feedback modifies the concept of this original model in that it provides a physical interaction between the loading rate and the state of strain on the fault. Two examples are developed: (a) Central Chile, and (b) Mexico. The predictions of earthquake hazards for both types of models are compared.

  3. Seismicity and tectonics of Bangladesh

    International Nuclear Information System (INIS)

    Hossain, K.M.

    1989-05-01

    Northern and eastern Bangladesh and surrounding areas belong to a seismically active zone and are associated with the subduction of the Indian plate. The seismicity and tectonics have been studied in detail and the observations have been correlated to understand the earthquake phenomenon in the region. The morphotectonic behaviour of northern Bangladesh shows that it is deeply related to the movement of the Dauki fault system and relative upliftment of the Shillong plateau. Contemporary seismicity in the Dauki fault system is relatively quiet comparing to that in the Naga-Disang-Haflong thrust belt giving rise to the probability of sudden release of energy being accumulated in the vicinity of the Dauki fault system. This observation corresponds with the predicted average return period of a large earthquake (1897 type) and the possibility of M > 8 earthquake in the vicinity of the Dauki fault within this century should not be ruled out. The seismicity in the folded belt in the east follows the general trend of Arakan-Yoma anticlinorium and represents shallow and low-angled thrust movements in conformity with the field observation. Seismotectonic behaviour in the deep basin part of Bangladesh demonstrates that an intraplate movement in the basement rock has been taking place along the deep-seated faults causing relative upliftment and subsidence in the basin. Bangladesh has been divided into three seismic zones on the basis of morphotectonic and seismic behaviour. Zone-I has been identified as the zone of high seismic risk. (author). 43 refs, 5 figs, 3 tabs

  4. Stagnant lid tectonics: Perspectives from silicate planets, dwarf planets, large moons, and large asteroids

    Directory of Open Access Journals (Sweden)

    Robert J. Stern

    2018-01-01

    Full Text Available To better understand Earth's present tectonic style–plate tectonics–and how it may have evolved from single plate (stagnant lid tectonics, it is instructive to consider how common it is among similar bodies in the Solar System. Plate tectonics is a style of convection for an active planetoid where lid fragment (plate motions reflect sinking of dense lithosphere in subduction zones, causing upwelling of asthenosphere at divergent plate boundaries and accompanied by focused upwellings, or mantle plumes; any other tectonic style is usefully called “stagnant lid” or “fragmented lid”. In 2015 humanity completed a 50+ year effort to survey the 30 largest planets, asteroids, satellites, and inner Kuiper Belt objects, which we informally call “planetoids” and use especially images of these bodies to infer their tectonic activity. The four largest planetoids are enveloped in gas and ice (Jupiter, Saturn, Uranus, and Neptune and are not considered. The other 26 planetoids range in mass over 5 orders of magnitude and in diameter over 2 orders of magnitude, from massive Earth down to tiny Proteus; these bodies also range widely in density, from 1000 to 5500 kg/m3. A gap separates 8 silicate planetoids with ρ = 3000 kg/m3 or greater from 20 icy planetoids (including the gaseous and icy giant planets with ρ = 2200 kg/m3 or less. We define the “Tectonic Activity Index” (TAI, scoring each body from 0 to 3 based on evidence for recent volcanism, deformation, and resurfacing (inferred from impact crater density. Nine planetoids with TAI = 2 or greater are interpreted to be tectonically and convectively active whereas 17 with TAI <2 are inferred to be tectonically dead. We further infer that active planetoids have lithospheres or icy shells overlying asthenosphere or water/weak ice. TAI of silicate (rocky planetoids positively correlates with their inferred Rayleigh number. We conclude that some type of stagnant lid tectonics is

  5. A palaeomagnetic perspective of Precambrian tectonic styles

    Science.gov (United States)

    Schmidt, P. W.; Embleton, B. J. J.

    1986-01-01

    The considerable success derived from palaeomagnetic studies of Phanerozoic rocks with respect to the tectonic styles of continental drift and plate tectonics, etc., have not been repeated by the many palaeomagnetic studies of Precambrian rocks. There are 30 years of research with results covering the major continents for Precambrian times that overlap considerably yet there is no concensus. There is good evidence that the usual assumptions employed by palaeomagnetism are valid for the Precambrian. The exisence of magnetic reversals during the Precambrian, for instance, is difficult to explain except in terms of a geomagnetic field that was predominantly dipolar in nature. It is a small concession to extend this notion of the Precambrian geomagnetic field to include its alignment with the Earth's spin axis and the other virtues of an axial geocentric dipole that characterize the recent geomagnetic field. In terms of greenstone terranes it is obvious that tectonic models postulated to explain these observations are paramount in understanding Precambrian geology. What relevance the current geographical relationships of continents have with their Precambrian relationships remains a paradox, but it would seem that the ensialic model for the development of greenstone terranes is favored by the Precambrian palaeomagnetic data.

  6. Towards a Tectonic Approach

    DEFF Research Database (Denmark)

    Hvejsel, Marie Frier; Kirkegaard, Poul Henning; Mortensen, Sophie Bondgaard

    2015-01-01

    with these demands. As the largest potential for energy savings lies in re-insulation of the building envelope, specifically by adding an additional insulation layer, this transformation will dramatically affect the everyday experience of the built environment. Articulating the architectural consequences...... and potentials of this transformation is an urgent matter if it is not to be realized solely as a monotonous technical cladding. In this matter, that of conceiving such extra insulation layer simultaneously as a technical ‘principle’ and as a spatial ‘gesture’ revealing an aesthetic architectural potential...... through this transformation is inevitably a tectonic question. By analyzing three historical examples, Adolf Loos’ Villa Moller, Le Corbusier’s Unité d’Habitation, and Frank Lloyd Wright’s Johnson Wax Administration Building, chosen for their tectonic ability to exploit the technical ‘principle’ defining...

  7. End Late Paleozoic tectonic stress field in the southern edge of Junggar Basin

    Directory of Open Access Journals (Sweden)

    Wei Ju

    2012-09-01

    Full Text Available This paper presents the end Late Paleozoic tectonic stress field in the southern edge of Junggar Basin by interpreting stress-response structures (dykes, folds, faults with slickenside and conjugate joints. The direction of the maximum principal stress axes is interpreted to be NW–SE (about 325°, and the accommodated motion among plates is assigned as the driving force of this tectonic stress field. The average value of the stress index R′ is about 2.09, which indicates a variation from strike-slip to compressive tectonic stress regime in the study area during the end Late Paleozoic period. The reconstruction of the tectonic field in the southern edge of Junggar Basin provides insights into the tectonic deformation processes around the southern Junggar Basin and contributes to the further understanding of basin evolution and tectonic settings during the culmination of the Paleozoic.

  8. Tectonics wins AAP Award

    Science.gov (United States)

    AGU's newest journal, Tectonics, won the 1983 award for excellence in journal design and production given by the Association of American Publishers, Inc. (AAP), in the eighth annual professional and scholarly publishing awards competition. Edited by John F. Dewey, the bimonthly journal is a joint publication of AGU and the European Geophysical Society. Paul E. Tapponnier is the European editor and B.C. Burchfiel is the North American editor. The journal is now in its third year of publication.

  9. Crustal structure and active tectonics in the Eastern Alps

    DEFF Research Database (Denmark)

    Brückl, E.; Behm, M.; Decker, K.

    2010-01-01

    fragment (PA), was interpreted and a triple junction was inferred. The goal of this study has been to relate these deep crustal structures to active tectonics. We used elastic plate modeling to reconsider the Moho fragmentation. We interpret subduction of EU below AD and PA from north to south......During the last decade, a series of controlled source seismic experiments brought new insight into the crustal and lithospheric structure of the Eastern Alps and their adjacent tectonic provinces. A fragmentation of the lithosphere into three blocks, Europe (EU), Adria (AD), and the new Pannonian...

  10. Problems of Tectonics and Tectonic Evolution of the Arctic

    Science.gov (United States)

    Vernikovskiy, V. A.; Metelkin, D. V.; Matushkin, N. Y.; Vernikovskaya, A. E.; Chernova, A. I.; Mikhaltsov, N. E.

    2017-12-01

    The Arctic Ocean within Russia remains poorly investigated area, in particular to geological structures and the Arctic Ocean floor. Many researchers believe that the basements of the terranes, composing the Arctic shelf and continental slopes, are of the Precambrian age. It was assumed that the Arctic terranes formed the ancient paleocontinent of Arctida that broke up during rifting, whereas the separated plates and terranes accreted to the periphery of the Arctic Ocean at a later stage. However, geological, geochronological and paleomagnetic evidence to test this assumption has been insufficient. Recently, geological and geophysical studies have significantly increased, in particular to the structures of Eastern Arctic. For example, the New Siberian Islands Archipelago is one of key structures for understanding geology and evolution of the Arctic region. Additionally, several submerged structures containing fragments of continental crust, including the Lomonosov Ridge and the Mendeleev Rise, are identified within the Arctic Ocean and adjacent to the New Siberian Islands Archipelago. Here we present new geochronological and paleomagnetic data to refine the evolution of the Arctida paleocontinent. Our model implies existence of the two Arctidas during Late Precambrian - Late Paleozoic. The earlier Arctida-I was located near equator and connected with the continental margins of Laurentia, Baltica and Siberia within the supercontinent of Rodinia. The initiation of Arctida-I rifting is associated with breakup of Rodinia. As a result, small plates, including Svalbard, Kara, New Siberia Island and other terranes, were formed. We have reconstructed the main stages of further remobilization and global drift of these plates before Pangea assemblage. We assume that the later Arctida-II was located at the Pangean periphery in the temperate latitudes, and was also connected to the Laurentia, Baltica, and Siberia cratons. The breakup of the Arctida-II is suggested to have

  11. TECTONIC ZONING OF THE SEDIMENTARY COVER OF THE SEA OF OKHOTSK BASED ON LITHOPHYSICAL, STRUCTURAL AND STRUCTURAL-LITHOPHYSICAL INDICATORS

    Directory of Open Access Journals (Sweden)

    V. P. Semakin

    2014-01-01

    Full Text Available In terms of tectonics, the Sea of Okhotsk (Fig.1 is the epi-Mesozoic Okhotsk plate comprising the heterogeneous basement that is mainly pre-Cenozoic (the lower structural stage and the sedimentary cover that is mainly represented by the Paleogenic-Neogenic-Quaternary deposits with the Upper Cretaceous sedimentary rocks observed locally without a visible hiatus (the upper structural stage.Results of tectonic zoning of the sedimentary cover based on  lithophysical indicators (Fig. 2 are represented in the format of maps showing lithophysical complexes (LC within the limits of four regional seismo-stratigraphic complexes/structural layers (RSSC I-IV corresponding to the following time intervals: the pre-Oligocene К2-P1-2 (RSSC I, the Oligocene – Lower Miocene P3-N11 (RSSC II, the Lower-Mid Miocene N11-2 (RSSC III, and the Upper Miocene – Pliocene N13-N2 (RSSC IV. Diverse lithological-facies associations composing the RSSCs are grouped into the following lithophysical complexes (LC: 1 - coal-bearing silty-clayey-sandy terrigenous, 2 - sandy-silty-clayey terrigenous, 3 - silty-clayey-siliceous, and 4 - sandy-silty-clayey volcanic [Sergeyev, 2006].Tectonic zoning of the sedimentary cover based on structural indicators is carried out with reference to the sediment-thickness map [Sergeyev, 2006], including a significantly revised segment showing the area of the Deryugin basin [Semakin, Kochergin, 2013]. Results of such zoning are represented in the format of a structural-tectonic map (Fig. 3 showing orientations and morphology of the structural elements of the sedimentary cover, the thickness of the sedimentary cover, and amplitudes of relative uplifts and troughs.With reference to the structural-tectonic map (see Fig 3, the structural elements of different orders are grouped by their sizes, spatial positions and orientations and thus comprise tectonic sistems (Fig. 4, structural zones (Fig. 5 that unclude relative uplifts and troughs that are

  12. Numerical modeling of intraplate seismicity with a deformable loading plate

    Science.gov (United States)

    So, B. D.; Capitanio, F. A.

    2017-12-01

    We use finite element modeling to investigate on the stress loading-unloading cycles and earthquakes occurrence in the plate interiors, resulting from the interactions of tectonic plates along their boundary. We model a visco-elasto-plastic plate embedding a single or multiple faults, while the tectonic stress is applied along the plate boundary by an external loading visco-elastic plate, reproducing the tectonic setting of two interacting lithospheres. Because the two plates deform viscously, the timescale of stress accumulation and release on the faults is self-consistently determined, from the boundary to the interiors, and seismic recurrence is an emerging feature. This approach overcomes the constraints on recurrence period imposed by stress (stress-drop) and velocity boundary conditions, while here it is unconstrained. We illustrate emerging macroscopic characteristics of this system, showing that the seismic recurrence period τ becomes shorter as Γ and Θ decreases, where Γ = ηI/ηL the viscosity ratio of the viscosities of the internal fault-embedded to external loading plates, respectively, and Θ = σY/σL the stress ratio of the elastic limit of the fault to far-field loading stress. When the system embeds multiple, randomly distributed faults, stress transfer results in recurrence period deviations, however the time-averaged recurrence period of each fault show the same dependence on Γ and Θ, illustrating a characteristic collective behavior. The control of these parameters prevails even when initial pre-stress was randomly assigned in terms of the spatial arrangement and orientation on the internal plate, mimicking local fluctuations. Our study shows the relevance of macroscopic rheological properties of tectonic plates on the earthquake occurrence in plate interiors, as opposed to local factors, proposing a viable model for the seismic behavior of continent interiors in the context of large-scale, long-term deformation of interacting tectonic

  13. Land-ocean tectonics (LOTs) and the associated seismic hazard over the Eastern Continental Margin of India (ECMI)

    Digital Repository Service at National Institute of Oceanography (India)

    Murthy, K.S.R.; Subrahmanyam, V.; Subrahmanyam, A.S.; Murty, G.P.S.; Sarma, K.V.L.N.S.

    are hence more predominant on the east coast. Recent geophysical studies delineated land-ocean tectonics (LOTs) over the eastern margin, in some cases associated with moderate seismicity as a result of the compressional stress acting on the Indian Plate...

  14. Tectonic Theory and Practice

    DEFF Research Database (Denmark)

    Frier, Marie; Fisker, Anna Marie; Kirkegaard, Poul Henning

    2010-01-01

    and assembly processes, seems a paradoxical challenge which has left prefabricated houses raw constructions rather than inhabitable homes. Based on the hypothesis that home is determined spatially via sensuous impressions of interiority at the threshold of furniture: The bath in Le Corbusier’s ‘Villa Savoye......’ is an example of this sensuous interior transformation of a house into a home, a level of detailing which is, however, seldom represented in the prefabricated house. Consequently, this paper investigates whether interiority can be developed as a tectonic theory and design principle for uniting home and system...

  15. Global tectonic of Enceladus driven by subsidence of South Polar Terrain

    Science.gov (United States)

    Czechowski, Leszek

    2016-07-01

    Enceladus is the smallest celestial body in the Solar System where volcanic and tectonic activities are observed. Every second, the mass of ~200 kg is ejected into space from the South Polar Terrain (SPT) - [1]. Our hypothesis states that this mass loss is the main driving mechanism of the tectonic processes. The hypothesis is presented in [2] and [3]. We find that the loss of the volatiles results in a void, an instability, and motion of solid matter to fill the void. The motion includes: (i) Subsidence of the 'lithosphere' of SPT. (ii) Flow of the matter in the mantle. (iii) Motion of plates adjacent to SPT towards the active region. The numerical model of the subsidence process is developed. It is based on the model of thermal convection in the mantle. Special boundary conditions are applied that could simulate subsidence of SPT. If emerging void is being filled by the subsidence of SPT only, then the velocity of subsidence is ~0.05 mm per yr. However, numerical calculations indicate that all three types of motion are usually important. The role of a given motion depends on the viscosity distribution. Generally, for most of the models the subsidence is ~0.02 mm per yr, but mantle flow and plates' motion also play a role in filling the void. The preliminary results of the numerical model indicate also that the velocity of adjacent plates could be ~0.02 mm per yr for the Newtonian rheology. The SPT is not compressed, so "tiger stripes" could exist for long time. Only after significant subsidence the regime of stresses changes to compression. It means the end of activity in a given region. The future region of activity is suggested. Acknowledgments This work was partially supported by the National Science Centre (grant 2011/01/B/ST10/06653). Computer resources of Interdisciplinary Centre for Mathematical and Computational Modeling of University of Warsaw were also used in the research References [1] Spencer, J. R., et al. (2009) Enceladus: An Active Cryovolcanic

  16. Active tectonics and earthquake potential of the Myanmar region

    Science.gov (United States)

    Wang, Yu; Sieh, Kerry; Tun, Soe Thura; Lai, Kuang-Yin; Myint, Than

    2014-04-01

    This paper describes geomorphologic evidence for the principal neotectonic features of Myanmar and its immediate surroundings. We combine this evidence with published structural, geodetic, and seismic data to present an overview of the active tectonic architecture of the region and its seismic potential. Three tectonic systems accommodate oblique collision of the Indian plate with Southeast Asia and extrusion of Asian territory around the eastern syntaxis of the Himalayan mountain range. Subduction and collision associated with the Sunda megathrust beneath and within the Indoburman range and Naga Hills accommodate most of the shortening across the transpressional plate boundary. The Sagaing fault system is the predominant locus of dextral motion associated with the northward translation of India. Left-lateral faults of the northern Shan Plateau, northern Laos, Thailand, and southern China facilitate extrusion of rocks around the eastern syntaxis of the Himalaya. All of these systems have produced major earthquakes within recorded history and continue to present major seismic hazards in the region.

  17. Alfred Wegener - From Continental Drift to Plate Tectonics

    Indian Academy of Sciences (India)

    permanently fixed on the Earth's surface and their positions do not change with time. In order to explain a wide range of confusing geological data, they supported the existence of huge land bridges that seem to have connected the .... courageously uses his intelligence." Needless to say, Wegener's new theory sparked a ...

  18. Learning about Plate Tectonics through Argument-Writing

    Science.gov (United States)

    Klein, Perry D.; Samuels, Boba

    2010-01-01

    In a quasi-experimental study (N = 60), grade 7/8 teachers students were taught to write arguments in content-area subjects. After instruction, students drew on document portfolios to write on a new topic: "Do the continents drift?" In a MANCOVA, students who participated in argument instruction scored significantly higher than a control…

  19. Using Google Earth to Teach Plate Tectonics and Science Explanations

    Science.gov (United States)

    Blank, Lisa M.; Plautz, Mike; Almquist, Heather; Crews, Jeff; Estrada, Jen

    2012-01-01

    "A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas" emphasizes that the practice of science is inherently a model-building activity focused on constructing explanations using evidence and reasoning (NRC 2012). Because building and refining is an iterative process, middle school students may view this practice…

  20. Seismic structure and tectonics of the continental margins of India

    Digital Repository Service at National Institute of Oceanography (India)

    Krishna, K.S.; Chaubey, A.K.; Rao, D.G.; Reddy, P.R.

    floor belong to different lithospheric plates. Active margins are commonly the sites of tectonic activity such as earthquakes, volcanoes, mountain building and formation of new igneous rocks. Because of the mountainous terrain the continental shelf... greater proportion of the river borne sediments occur on the shelves, continental slopes, and deep sea fans where terrigenous sedimentation is dominant process. On lower slopes and continental rises, fine-grained siliciclastics commonly mixed...

  1. Contemporary block tectonics: California and Nevada.

    Science.gov (United States)

    Hill, D.P.

    1982-01-01

    Well-determined fault plane solution and the gross pattern of late-Cenozoic faulting in California and Nevada show a systematic relation between the orientation of fault planes and slip directions. In general, normal faults have N strikes, reverse faults have E strikes, and dextral and sinstral strike slip faults have NW and NE strikes, respectively. Kinematically, this relation is consistent with the response of clusters of fault-bounded crustal blocks to a regional stress field generated by the relative motion between the Pacific and N American plates. In this stress field, the greatest and least principal (compressive) stresses are restricted to N and E striking vertical planes, respectively. Simple arrangements of block clusters mimic the gross kinematic pattern of Quaternary faulting in California and Nevada. Some implications for contemporary tectonics emphasized by this model involve the W displacement of the Sierra Nevada block with respect to the stable interior of the N American plates, oblique thrusting of the Salinian block over the Pacific plate, and a progressive increase in the offset of the San Andreas fault represented by the 'big bend' through the Transverse Ranges. -from Author

  2. Quantitative tectonic reconstructions of Zealandia based on crustal thickness estimates

    Science.gov (United States)

    Grobys, Jan W. G.; Gohl, Karsten; Eagles, Graeme

    2008-01-01

    Zealandia is a key piece in the plate reconstruction of Gondwana. The positions of its submarine plateaus are major constraints on the best fit and breakup involving New Zealand, Australia, Antarctica, and associated microplates. As the submarine plateaus surrounding New Zealand consist of extended and highly extended continental crust, classic plate tectonic reconstructions assuming rigid plates and narrow plate boundaries fail to reconstruct these areas correctly. However, if the early breakup history shall be reconstructed, it is crucial to consider crustal stretching in a plate-tectonic reconstruction. We present a reconstruction of the basins around New Zealand (Great South Basin, Bounty Trough, and New Caledonia Basin) based on crustal balancing, an approach that takes into account the rifting and thinning processes affecting continental crust. In a first step, we computed a crustal thickness map of Zealandia using seismic, seismological, and gravity data. The crustal thickness map shows the submarine plateaus to have a uniform crustal thickness of 20-24 km and the basins to have a thickness of 12-16 km. We assumed that a reconstruction of Zealandia should close the basins and lead to a most uniform crustal thickness. We used the standard deviation of the reconstructed crustal thickness as a measure of uniformity. The reconstruction of the Campbell Plateau area shows that the amount of extension in the Bounty Trough and the Great South Basin is far smaller than previously thought. Our results indicate that the extension of the Bounty Trough and Great South Basin occurred simultaneously.

  3. Functionalized Nano-Film Microchannel Plate: A Single High Aspect Ratio Device for High Resolution, Low Noise Astronomical Imaging, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Atomic layer deposited functional nano-film technology is used to manufacture Microchannel plate (MCP) devices capable of high gain / low ion feedback operation, on...

  4. Evaluation of the base/subgrade soil under repeated loading : phase II, in-box and ALF cyclic plate load tests.

    Science.gov (United States)

    2012-03-01

    This research study aims at evaluating the performance of base and subgrade soil in flexible pavements under repeated loading test conditions. For this purpose, an indoor cyclic plate load testing equipment was developed and used to conduct a series ...

  5. Convergent plate margin dynamics : New perspectives from structural geology, geophysics and geodynamic modelling

    NARCIS (Netherlands)

    Schellart, W. P.; Rawlinson, N.

    2010-01-01

    Convergent plate margins occur when two adjoining tectonic plates come together to form either a subduction zone, where at least one of the converging plates is oceanic and plunges beneath the other into the mantle, or a collision zone, where two continents or a continent and a magmatic arc collide.

  6. Puzzling features of western Mediterranean tectonics explained by slab dragging

    Science.gov (United States)

    Spakman, Wim; Chertova, Maria V.; van den Berg, Arie.; van Hinsbergen, Douwe J. J.

    2018-02-01

    The recent tectonic evolution of the western Mediterranean region is enigmatic. The causes for the closure of the Moroccan marine gateway prior to the Messinian salinity crisis, for the ongoing shortening of the Moroccan Rif and for the origin of the seismogenic Trans-Alboran shear zone and eastern Betics extension are unclear. These puzzling tectonic features cannot be fully explained by subduction of the east-dipping Gibraltar slab in the context of the regional relative plate motion frame. Here we use a combination of geological and geodetic data, as well as three-dimensional numerical modelling of subduction, to show that these unusual tectonic features could be the consequence of slab dragging—the north to north-eastward dragging of the Gibraltar slab by the absolute motion of the African Plate. Comparison of our model results to patterns of deformation in the western Mediterranean constrained by geological and geodetic data confirm that slab dragging provides a plausible mechanism for the observed deformation. Our results imply that the impact of absolute plate motion on subduction is identifiable from crustal observations. Identifying such signatures elsewhere may improve the mantle reference frame and provide insights on subduction evolution and associated crustal deformation.

  7. Tectonic reconstruction models for the break-up and divergence of the Manihiki and Hikurangi plateaux

    Science.gov (United States)

    Pockalny, R. A.; Dahn, M. R.

    2013-12-01

    The plate tectonic history of the Mid-Cretaceous seafloor located between the Manihiki and Hikurangi plateaux is poorly constrained due to the complex pattern of fracture zones and the lack of correlatable magnetic anomalies. Conventional plate reconstruction models suggest the Manihiki, Hikurangi and Ontong Java plateau were once part of a larger igneous complex, which broke up during a major plate reorganization at about magnetic anomaly M0 time (~120 Ma). The divergence between the Manihiki and Hikurangi plateaux continued for an unspecified duration, but likely ceased during another major plate reorganization event in the Late Cretaceous (71-84 Ma). At that time, spreading near the Osbourn Trough relocated to the Pacific-Antarctic divergent plate boundary. To understand the detailed tectonic history of the region bracketed by these plate reorganization events, we have assembled all available high-resolution multibeam in the region. These data were used to quantify regional trends in abyssal hill orientations and to identify fracture zone locations and offset orientations. Our preliminary results suggest a fairly complex spreading history for the region, which requires multiple Euler Poles and ridge-axis relocation events. We present several tectonic reconstruction scenarios to account for these new observations. These tectonic reconstructions have important implications for the mantle plume-influenced history of the region and the origin/evolution of the Manihiki-Hikurangi-Ontong Java large igneous province.

  8. Tectonic pattern of mare ridges of the Letronne-Montes Riphaeus region of the Moon

    International Nuclear Information System (INIS)

    Raitala, J.

    1978-01-01

    A structural analysis is presented of mare ridges in an area of about 360 000 km 2 in the southeastern part of Oceanus Procellarum just north of Mare Humorum. Mare ridges can be regarded as the result of large-scale natural tectonic deformation experiments coupled with and extended by volcanic phenomena. The old lunar crust has evidently retained part of the Moon's original tectonic elements throughout major exo- and endogenic events. Those structures which in places were flooded by mare lavas were also the first flaws to yield and to extend during younger tectonic and volcanic activity. Linear mare ridges may thus have formed at the activated and re-activated junctures of lunar crustal plates. Implications for the tectonics of mare ridges evidently show that one global stress field cannot account for all lunar tectonics but that global and areal variations in the lunar stress system have probably occurred. (Auth.)

  9. Deciphering detailed plate kinematics of the Indian Ocean and developing a unified model for East Gondwanaland reconstruction: An Indian-Australian-French initiative

    Digital Repository Service at National Institute of Oceanography (India)

    Yatheesh, V.; Dyment, J.; Bhattacharya, G.C.; Muller, R.D.

    in the northwestern and central Indian Ocean by combining the available magnetic data from conjugate regions and provided a detailed understanding of plate tectonic evolution of Indian-Antarctic and Indian-African plate boundaries. Those projects were complemented...

  10. Vertical tectonics at an active continental margin

    Science.gov (United States)

    Houlié, N.; Stern, T. A.

    2017-01-01

    Direct observations of vertical movements of the earth's surface are now possible with space-based GPS networks, and have applications to resources, hazards and tectonics. Here we present data on vertical movements of the Earth's surface in New Zealand, computed from the processing of GPS data collected between 2000 and 2015 by 189 permanent GPS stations. We map the geographical variation in vertical rates and show how these variations are explicable within a tectonic framework of subduction, volcanic activity and slow slip earthquakes. Subsidence of >3 mm/yr is observed along southeastern North Island and is interpreted to be due to the locked segment of the Hikurangi subduction zone. Uplift of 1-3 mm/yr further north along the margin of the eastern North Island is interpreted as being due to the plate interface being unlocked and underplating of sediment on the subduction thrust. The Volcanic Plateau of the central North Island is being uplifted at about 1 mm/yr, which can be explained by basaltic melts being injected in the active mantle-wedge at a rate of ∼6 mm/yr. Within the Central Volcanic Region there is a 250 km2 area that subsided between 2005 and 2012 at a rate of up to 14 mm/yr. Time series from the stations located within and near the zone of subsidence show a strong link between subsidence, adjacent uplift and local earthquake swarms.

  11. Teaching Tectonics to Undergraduates with Web GIS

    Science.gov (United States)

    Anastasio, D. J.; Bodzin, A.; Sahagian, D. L.; Rutzmoser, S.

    2013-12-01

    Geospatial reasoning skills provide a means for manipulating, interpreting, and explaining structured information and are involved in higher-order cognitive processes that include problem solving and decision-making. Appropriately designed tools, technologies, and curriculum can support spatial learning. We present Web-based visualization and analysis tools developed with Javascript APIs to enhance tectonic curricula while promoting geospatial thinking and scientific inquiry. The Web GIS interface integrates graphics, multimedia, and animations that allow users to explore and discover geospatial patterns that are not easily recognized. Features include a swipe tool that enables users to see underneath layers, query tools useful in exploration of earthquake and volcano data sets, a subduction and elevation profile tool which facilitates visualization between map and cross-sectional views, drafting tools, a location function, and interactive image dragging functionality on the Web GIS. The Web GIS platform is independent and can be implemented on tablets or computers. The GIS tool set enables learners to view, manipulate, and analyze rich data sets from local to global scales, including such data as geology, population, heat flow, land cover, seismic hazards, fault zones, continental boundaries, and elevation using two- and three- dimensional visualization and analytical software. Coverages which allow users to explore plate boundaries and global heat flow processes aided learning in a Lehigh University Earth and environmental science Structural Geology and Tectonics class and are freely available on the Web.

  12. Tectonics and volcanism on Mars: a compared remote sensing analysis with earthly geostructures

    Science.gov (United States)

    Baggio, Paolo; Ancona, M. A.; Callegari, I.; Pinori, S.; Vercellone, S.

    1999-12-01

    The recent knowledge on Mars' lithosphere evolution does not find yet sufficient analogies with the Earth's tectonic models. The Viking image analysis seems to be even now frequently, rather fragmentary, and do not permits to express any coherent relationships among the different detected phenomena. Therefore, today it is impossible to support any reliable kinematic hypothesis. The Remote-Sensing interpretation is addressed to a Viking image mosaic of the known Tharsis Montes region and particularly focused on the Arsia Mons volcano. Several previously unknown lineaments, not directly linked to volcano-tectonics, were detected. Their mutual relationships recall transcurrent kinematics that could be related to similar geostructural models known in the Earth plate tectonic dynamics. Several concordant relationships between the Arsia Mons volcano and the brittle extensive tectonic features of earthly Etnean district (Sicily, South Italy), interpreted on Landsat TM images, were pointed out. These analogies coupled with the recently confirmed strato- volcano topology of Tharsis Montes (Head and Wilson), the layout distribution of the effusive centers (Arsia, Pavonis and Ascraeus Montes), the new tectonic lineaments and the morphological features, suggest the hypothesis of a plate tectonic volcanic region. The frame could be an example in agreement with the most recent interpretation of Mars (Sleep). A buried circular body, previously incorrectly interpreted as a great landslide event from the western slope of Arsia Mons volcano, seems really to be a more ancient volcanic structure (Arsia Mons Senilis), which location is in evident relation with the interpreted new transcurrent tectonic system.

  13. A Possible Differentially Shortened Strike-slip Plate Boundary: the Okhotsk Plate Example.

    Science.gov (United States)

    Hindle, D.; Egorov, V.; Mackey, K. G.; Fujita, K.

    2004-12-01

    The Okhotsk plate has been postulated based on a combination of GPS geodetic inversions (REVEL1), seimsicity, geologic and lineament data. Lying between the North American and Eurasian plates, its northwestern corner would appear to be undergoing compression in a scissors motion between the two bounding plates. Extrusion tectonics along multiple, large strike-slip faults within the Okhotsk plate itself have been suggested to allow the escape of material away from the apex of Eurasia-North America. The plate boundary between Okhotsk and North America has been suggested to be diffuse, based on widely scattered minor seismicity. However, the large, left lateral, Ulakhan fault has also been suggested as a candidate plate boundary. We present field geological and geomorphological evidence of the partitioning of deformation between the Ulakhan fault, and several parallel and oblique, linked faults. The Ulakhan fault strand appears to have a maximum displacement of 24 km based on river valley offsets and closing large pull apart basins. Some of the displacement from the Ulakhan fault appears relayed into the plate margin along oblique trending, thrust/oblique slip faults. Estimated shortening over these faults is equivalent to the amount of shortening relayed into the plate margin from the plate boundary. There may be several thrust/oblique slip faults along the Ulakhan fault, which leads to the interesting situation of a segmented, strike-slip plate boundary being actively shortened in a margin parallel direction. This may be the result of postulated extrusion of the Okhotsk plate due to North America/Eurasia convergence. Such a situation would have important consequences for the interpretation of GPS data in a plate tectonic context.

  14. Teaching And Learning Tectonics With Web-GIS

    Science.gov (United States)

    Anastasio, D. J.; Sahagian, D. L.; Bodzin, A.; Teletzke, A. L.; Rutzmoser, S.; Cirucci, L.; Bressler, D.; Burrows, J. E.

    2012-12-01

    Tectonics is a new curriculum enhancement consisting of six Web GIS investigations designed to augment a traditional middle school Earth science curriculum. The investigations are aligned to Disciplinary Core Ideas: Earth and Space Science from the National Research Council's (2012) Framework for K-12 Science Education and to tectonics benchmark ideas articulated in the AAAS Project 2061 (2007) Atlas of Science Literacy. The curriculum emphasizes geospatial thinking and scientific inquiry and consists of the following modules: Geohazards, which plate boundary is closest to me? How do we recognize plate boundaries? How does thermal energy move around the Earth? What happens when plates diverge? What happens when plate move sideways past each other? What happens when plates collide? The Web GIS interface uses JavaScript for simplicity, intuition, and convenience for implementation on a variety of platforms making it easier for diverse middle school learners and their teachers to conduct authentic Earth science investigations, including multidisciplinary visualization, analysis, and synthesis of data. Instructional adaptations allow students who are English language learners, have disabilities, or are reluctant readers to perform advanced desktop GIS functions including spatial analysis, map visualization and query. The Web GIS interface integrates graphics, multimedia, and animation in addition to newly developed features, which allow users to explore and discover geospatial patterns that would not be easily visible using typical classroom instructional materials. The Tectonics curriculum uses a spatial learning design model that incorporates a related set of frameworks and design principles. The framework builds on the work of other successful technology-integrated curriculum projects and includes, alignment of materials and assessments with learning goals, casting key ideas in real-world problems, engaging students in scientific practices that foster the use of key

  15. Phanerozoic tectonic evolution of the Circum-North Pacific

    Science.gov (United States)

    Nokleberg, Warren J.; Parfenov, Leonid M.; Monger, James W.H.; Norton, Ian O.; Khanchuk, Alexander I.; Stone, David B.; Scotese, Christopher R.; Scholl, David W.; Fujita, Kazuya

    2000-01-01

    the ancestral margins of present-day Northeast Asia and northwestern North America. The rifting resulted in the fragmentation of each continent and the formation of cratonal and passive continental-margin terranes that eventually migrated and accreted to other sites along the evolving margins of the original or adjacent continents. (2) From about the Late Triassic through the mid-Cretaceous, a succession of island arcs and tectonically paired subduction zones formed near the continental margins. (3) From about mainly the mid-Cretaceous through the present, a succession of igneous arcs and tectonically paired subduction zones formed along the continental margins. (4) From about the Jurassic to the present, oblique convergence and rotations caused orogenparallel sinistral and then dextral displacements within the upper-plate margins of cratons that have become Northeast Asia and North America. The oblique convergences and rotations resulted in the fragmentation, displacement, and duplication of formerly more nearly continuous arcs, subduction zones, and passive continental margins. These fragments were subsequently accreted along the expanding continental margins. (5) From the Early Jurassic through Tertiary, movement of the upper continental plates toward subduction zones resulted in strong plate coupling and accretion of the former island arcs and subduction zones to the continental margins. Accretions were accompanied and followed by crustal thickening, anatexis, metamorphism, and uplift. The accretions resulted in substantial growth of the North Asian and North American Continents. (6) During the middle and late Cenozoic, oblique to orthogonal convergence of the Pacifi c plate with present-day Alaska and Northeast Asia resulted in formation of the modern-day ring of volcanoes around the Circum-North Pacific. Oblique convergence between the Pacific plate and Alaska also resulted in major dextral-slip faulting in interior and southern Alaska and along the western p

  16. Biological modulation of tectonics

    Science.gov (United States)

    Sleep, N. H.; Bird, D. K.

    2008-12-01

    Photosynthesis has had geologic consequences over the Earth's history. In addition to modifying Earth's atmosphere and ocean chemistry, it has also modulated tectonic processes through enhanced weathering and modification of the nature and composition of sedimentary rocks within fold mountain belts and convergent margins. Molecular biological studies indicate that bacterial photosynthesis evolved just once and that most bacterial clades descend from this photosynthetic common ancestor. Iron-based photosynthesis (ideally 4FeO + CO2 + H2O = 2Fe2O3 + CH2O) was the most bountiful anoxygenic niche on land. The back reaction provided energy to heterotrophic microbes and returned FeO to the photosynthetic microbes. Bacterial land colonists evolved into ecosystems that effectively weathered FeO-bearing minerals and volcanic glass. Clays, sands, and dissolved cations from the weathering process entered the ocean and formed our familiar classes sedimentary rocks: shales, sandstones, and carbonates. Marine photosynthesis caused organic carbon to accumulate in black shales. In contrast, non-photosynthetic ecosystems do not cause organic carbon to accumulate in shale. These evolutionary events occurred before 3.8 Ga as black shales are among the oldest rock types (Rosing and Frei, Earth Planet. Sci. Lett. 217, 237-244, 2004). Thick sedimentary sequences deformed into fold mountain belts. They remelted at depth to form granitic rocks (Rosing et al., Palaeoclimatol. Palaeoecol. 232, 99-11, 2006). Regions of outcropping low-FeO rocks including granites, quartzites, and some shales were a direct result. This dearth of FeO favored the evolution of oxic photosynthesis of cyanobacteria from photosynthetic soil bacteria. Black shales have an additional modulation effect on tectonics as they concentrate radioactive elements, particularly uranium (e.g. so that the surface heat flow varies by a factor of ca. 2). Thick sequences of black shales at continental rises of passive margins are

  17. Global evaluation of erosion rates in relation to tectonics

    Science.gov (United States)

    Hecht, Hagar; Oguchi, Takashi

    2017-12-01

    Understanding the mechanisms and controlling factors of erosion rates is essential in order to sufficiently comprehend bigger processes such as landscape evolution. For decades, scientists have been researching erosion rates where one of the main objectives was to find the controlling factors. A variety of parameters have been suggested ranging from climate-related, basin morphometry and the tectonic setting of an area. This study focuses on the latter. We use previously published erosion rate data obtained mainly using 10Be and sediment yield and sediment yield data published by the United States Geological Survey. We correlate these data to tectonic-related factors, i.e., distance to tectonic plate boundary, peak ground acceleration ( PGA), and fault distribution. We also examine the relationship between erosion rate and mean basin slope and find significant correlations of erosion rates with distance to tectonic plate boundary, PGA, and slope. The data are binned into high, medium, and low values of each of these parameters and grouped in all combinations. We find that groups with a combination of high PGA (> 0.2.86 g) and long distance (> 1118.69 km) or low PGA (erosion rates include long distance and/or low PGA, and groups with high erosion rates include neither of these. These observations indicate that tectonics plays a major role in determining erosion rates, which is partly ascribable to steeper slopes produced by active crustal movements. However, our results show no apparent correlation of slope with erosion rates, pointing to problems with using mean basin-wide slope as a slope indicator because it does not represent the complex slope distribution within a basin.

  18. Modic changes in lumbar spine: prevalence and distribution patterns of end plate oedema and end plate sclerosis.

    Science.gov (United States)

    Xu, Lei; Chu, Bin; Feng, Yang; Xu, Feng; Zou, Yue-Fen

    2016-01-01

    The purpose of this study is to evaluate the distribution of end plate oedema in different types of Modic change especially in mixed type and to analyze the presence of end plate sclerosis in various types of Modic change. 276 patients with low back pain were scanned with 1.5-T MRI. Three radiologists assessed the MR images by T1 weighted, T2 weighted and fat-saturation T2 weighted sequences and classified them according to the Modic changes. Pure oedematous end plate signal changes were classified as Modic Type I; pure fatty end plate changes were classified as Modic Type II; and pure sclerotic end plate changes as Modic Type III. A mixed feature of both Types I and II with predominant oedematous signal change is classified as Modic I-II, and a mixture of Types I and II with predominant fatty change is classified as Modic II-I. Thus, the mixed types can further be subdivided into seven subtypes: Types I-II, Types II-I, Types I-III, Types III-I, Types II-III, Types III-II and Types I-III. During the same period, 52 of 276 patients who underwent CT and MRI were retrospectively reviewed to determine end plate sclerosis. (1) End plate oedema: of the 2760 end plates (276 patients) examined, 302 end plates showed Modic changes, of which 82 end plates showed mixed Modic changes. The mixed Modic changes contain 92.7% of oedematous changes. The mixed types especially Types I-II and Types II-I made up the majority of end plate oedematous changes. (2) End plate sclerosis: 52 of 276 patients were examined by both MRI and CT. Of the 520 end plates, 93 end plates showed Modic changes, of which 34 end plates have shown sclerotic changes in CT images. 11.8% of 34 end plates have shown Modic Type I, 20.6% of 34 end plates have shown Modic Type II, 2.9% of 34 end plates have shown Modic Type III and 64.7% of 34 end plates have shown mixed Modic type. End plate oedema makes up the majority of mixed types especially Types I-II and Types II-I. The end plate sclerosis on CT images may

  19. The Aegean: A natural laboratory for tectonics

    International Nuclear Information System (INIS)

    Burchfiel, B C

    2008-01-01

    The Aegean, a young and active tectonic region, is a natural laboratory for analyzing many tectonic processes that occur in backarc extensional regimes, and the correlation of these processes from landscape development to deeper mantle dynamics. Cenozoic development of the Aegean region was dominated by subduction beneath Europe and coeval upper plate extension modified by westward extrusion of Anatolia. Intraorogenic and backarc extension began during early Cenozoic time within the Balkans and NW Turkey during closure of the Vardar ocean. Extension was manifested by core complex formation and a change in volcanism caused by the evolution of the lithosphere and mantle wedge. Following a short period of local (?) shortening in ∼ early Miocene time, regional extension began and continued to the present. Within the Hellenides, E-W extension and the subduction zone migrated westward as thick and thin crustal units were progressively accreted and were complexly rotated up to 40 0 CW. Within the eastern Balkans and NW Turkey, N-S extension migrated westward and southward, and in the Aegean the volcanic arc and subduction zone migrated southward. Turkish crustal elements rotated complexly CCW, which in concert with the CW rotation in the Hellenides increased the curvature of the subduction zone and lengthened the orogen causing greater subsidence and extension in the Aegean Sea. Westward extrusion of Anatolia from the Arabian collision zone was enhanced by slab roll back in west moving Aegean crust more rapidly westward. Abundant evidence supports slab rollback at different velocities along the subduction zone. In Pliocene time, the North Anatolian fault crossed the Hellenides in a complex transtensional zone and a diffuse zone of left-lateral shear crossed western Turkey at present isolating a relatively undeforming Aegean plate. Major tectonic questions include: What is the geometry and fate of subducted slabs?, How much crust is accreted during subduction of thick

  20. Tectonic evolution of Mars

    International Nuclear Information System (INIS)

    Wise, D.U.; Golombek, M.P.; McGill, G.E.

    1979-01-01

    Any model for the tectonic evolution of Mars must account for two major crustal elements: the Tharsis bulge and the topographically low and lightly crated northern third of the planet. Ages determined by crater density indicate that both of these elements came into existence very early in Martian history, a conclusion that holds no matter which of the current crater density versus age curves is used. The size of these two major crustal elements and their sequential development suggest that both may be related to a global-scale internal process. It is proposed that the resurfacing of the northern third of Mars is related to subcrustal erosion and isostatic foundering during the life of a first-order convection cell. With the demise of the cell, denser segregations of metallic materials began to coalesce as a gravitatively unstable layer which finally overturned to form the core. In the overturn, lighter crustal materials was shifted laterally and underplated beneath Tharsis to cause rapid and permanent isostatic rise. This was followed by a long-lived thermal phase produced by the hot underplate and by the gravitative energy of core formation slowly making its way to the surface to produce the Tharsis volcanics

  1. Earth's glacial record and its tectonic setting

    Science.gov (United States)

    Eyles, N.

    1993-09-01

    Glaciations have occurred episodically at different time intervals and for different durations in Earth's history. Ice covers have formed in a wide range of plate tectonic and structural settings but the bulk of Earth's glacial record can be shown to have been deposited and preserved in basins within extensional settings. In such basins, source area uplift and basin subsidence fulfill the tectonic preconditions for the initiation of glaciation and the accomodation and preservation of glaciclastic sediments. Tectonic setting, in particular subsidence rates, also dictates the type of glaciclastic facies and facies successions that are deposited. Many pre-Pleistocene glaciated basins commonly contain well-defined tectonostratigraphic successions recording the interplay of tectonics and sedimentation; traditional climatostratigraphic approaches involving interpretation in terms of either ice advance/retreat cycles or glacio-eustatic sea-level change require revision. The direct record of continental glaciation in Earth history, in the form of classically-recognised continental glacial landforms and "tillites", is meagre; it is probable that more than 95% of the volume of preserved "glacial" strata are glacially-influenced marine deposits that record delivery of large amounts of glaciclastic sediment to offshore basins. This flux has been partially or completely reworked by "normal" sedimentary processes such that the record of glaciation and climate change is recorded in marine successions and is difficult to decipher. The dominant "glacial" facies in the rock record are subaqueous debris flow diamictites and turbidites recording the selective preservation of poorly-sorted glaciclastic sediment deposited in deep water basins by sediment gravity flows. However, these facies are also typical of many non-glacial settings, especially volcanically-influenced environments; numerous Archean and Proterozoic diamictites, described in the older literature as tillites, have no

  2. Strike-slip tectonics during rift linkage

    Science.gov (United States)

    Pagli, C.; Yun, S. H.; Ebinger, C.; Keir, D.; Wang, H.

    2017-12-01

    The kinematics of triple junction linkage and the initiation of transforms in magmatic rifts remain debated. Strain patterns from the Afar triple junction provide tests of current models of how rifts grow to link in area of incipient oceanic spreading. Here we present a combined analysis of seismicity, InSAR and GPS derived strain rate maps to reveal that the plate boundary deformation in Afar is accommodated primarily by extensional tectonics in the Red Sea and Gulf of Aden rifts, and does not require large rotations about vertical axes (bookshelf faulting). Additionally, models of stress changes and seismicity induced by recent dykes in one sector of the Afar triple junction provide poor fit to the observed strike-slip earthquakes. Instead we explain these patterns as rift-perpendicular shearing at the tips of spreading rifts where extensional strains terminate against less stretched lithosphere. Our results demonstrate that rift-perpendicular strike-slip faulting between rift segments achieves plate boundary linkage during incipient seafloor spreading.

  3. Planetary Geophysics and Tectonics

    Science.gov (United States)

    Zuber, Maria

    2005-01-01

    The broad objective of this work is to improve understanding of the internal structures and thermal and stress histories of the solid planets by combining results from analytical and computational modeling, and geophysical data analysis of gravity, topography and tectonic surface structures. During the past year we performed two quite independent studies in the attempt to explain the Mariner 10 magnetic observations of Mercury. In the first we revisited the possibility of crustal remanence by studying the conditions under which one could break symmetry inherent in Runcorn's model of a uniformly magnetized shell to produce a remanent signal with a dipolar form. In the second we applied a thin shell dynamo model to evaluate the range of intensity/structure for which such a planetary configuration can produce a dipole field consistent with Mariner 10 results. In the next full proposal cycle we will: (1) develop numerical and analytical and models of thin shell dynamos to address the possible nature of Mercury s present-day magnetic field and the demise of Mars magnetic field; (2) study the effect of degree-1 mantle convection on a core dynamo as relevant to the early magnetic field of Mars; (3) develop models of how the deep mantles of terrestrial planets are perturbed by large impacts and address the consequences for mantle evolution; (4) study the structure, compensation, state of stress, and viscous relaxation of lunar basins, and address implications for the Moon s state of stress and thermal history by modeling and gravity/topography analysis; and (5) use a three-dimensional viscous relaxation model for a planet with generalized vertical viscosity distribution to study the degree-two components of the Moon's topography and gravity fields to constrain the primordial stress state and spatial heterogeneity of the crust and mantle.

  4. Revisit of Criteria and Evidence for the Tectonic Erosion vs Accretion in East Asian Margin

    Science.gov (United States)

    Kimura, G.; Hamahashi, M.

    2015-12-01

    Accretionary and erosive margins provide tectonic end-members in subduction zone and how these tectonic processes might be recorded and recognizable in ancient subduction complexes remains a challenging issue. Tectonic erosion includes sediment subduction and basal erosion along the plate boundary megathrust and drags down the crust of the upper plate into the mantle. Geologic evidence for the erosion is commonly based on lost geological tectono-stratigraphic data, i.e. gaps in the record and indirect phenomena such as subsidence of the forearc slopes. A topographically rough surface such as seamount has been suggested to work like an erosive saw carving the upper plate. Another mechanism of basal erosion has been suggested to be hydrofracturing of upper plate materials due to dehydration-induced fluid pressures, resulting in entrainment of upper plate materials into the basal décollement. Considering the interaction between the ~30 km thick crust of the upper plate and subducting oceanic plate, a subduction dip angle of ~15°, and convergent rate of ~10 cm/year, at least ~1 Ma of continuous basal erosion is necessary to induce clear subsidence of the forearc because the width of plate interface between the upper crustal and subducting plates is about 115 km (30/cos15°). In several examples of subduction zones, for example the Japan Trench and the Middle America Trench off Costa Rica, the subsidence of a few thousand metres of the forearc, combined with a lack of accretionary prism over a period of several million years, suggest that the erosive condition needs to be maintained for several to tens of million years.Such age gaps in the accretionary complex, however, do not automatically imply that tectonic erosion has taken place, as other interpretations such as no accretion, cessation of subduction, and/or later tectonic modification, are also possible. Recent drilling in the forearc of the Nankai Trough suggests that the accretion was ceased between ~12 Ma to

  5. Creep-fatigue evaluation method for weld joint of Mod.9Cr-1Mo steel Part II: Plate bending test and proposal of a simplified evaluation method

    International Nuclear Information System (INIS)

    Ando, Masanori; Takaya, Shigeru

    2016-01-01

    Highlights: • Creep-fatigue evaluation method for weld joint of Mod.9Cr-1Mo steel is proposed. • A simplified evaluation method is also proposed for the codification. • Both proposed evaluation method was validated by the plate bending test. • For codification, the local stress and strain behavior was analyzed. - Abstract: In the present study, to develop an evaluation procedure and design rules for Mod.9Cr-1Mo steel weld joints, a method for evaluating the creep-fatigue life of Mod.9Cr-1Mo steel weld joints was proposed based on finite element analysis (FEA) and a series of cyclic plate bending tests of longitudinal and horizontal seamed plates. The strain concentration and redistribution behaviors were evaluated and the failure cycles were estimated using FEA by considering the test conditions and metallurgical discontinuities in the weld joints. Inelastic FEA models consisting of the base metal, heat-affected zone and weld metal were employed to estimate the elastic follow-up behavior caused by the metallurgical discontinuities. The elastic follow-up factors determined by comparing the elastic and inelastic FEA results were determined to be less than 1.5. Based on the estimated elastic follow-up factors obtained via inelastic FEA, a simplified technique using elastic FEA was proposed for evaluating the creep-fatigue life in Mod.9Cr-1Mo steel weld joints. The creep-fatigue life obtained using the plate bending test was compared to those estimated from the results of inelastic FEA and by a simplified evaluation method.

  6. How the continents deform: The evidence from tectonic geodesy

    Science.gov (United States)

    Thatcher, Wayne R.

    2009-01-01

    Space geodesy now provides quantitative maps of the surface velocity field within tectonically active regions, supplying constraints on the spatial distribution of deformation, the forces that drive it, and the brittle and ductile properties of continental lithosphere. Deformation is usefully described as relative motions among elastic blocks and is block-like because major faults are weaker than adjacent intact crust. Despite similarities, continental block kinematics differs from global plate tectonics: blocks are much smaller, typically ∼100–1000 km in size; departures from block rigidity are sometimes measurable; and blocks evolve over ∼1–10 Ma timescales, particularly near their often geometrically irregular boundaries. Quantitatively relating deformation to the forces that drive it requires simplifying assumptions about the strength distribution in the lithosphere. If brittle/elastic crust is strongest, interactions among blocks control the deformation. If ductile lithosphere is the stronger, its flow properties determine the surface deformation, and a continuum approach is preferable.

  7. Tectonics: The meaning of form

    DEFF Research Database (Denmark)

    Christiansen, Karl; Brandt, Per Aage

    Tectonics – The meaning of form deals with one of the core topics of architecture: the relationship between form and content. In the world of architecture, form is not only made from brick, glass and wood. Form means something. When a material is processed with sufficient technical skill and insi......Tectonics – The meaning of form deals with one of the core topics of architecture: the relationship between form and content. In the world of architecture, form is not only made from brick, glass and wood. Form means something. When a material is processed with sufficient technical skill...... perspectives. You can read the chapters in any order you like – from the beginning, end or the middle. There is no correct order. The project is methodologically inductive: the more essays you read, the broader your knowledge of tectonics get....

  8. The Tectonic Potentials of Concrete

    DEFF Research Database (Denmark)

    Egholm Pedersen, Ole

    2013-01-01

    Contemporary techniques for concrete casting in an architectural context are challenged by demands of increased individualization in our built environment, reductions in the use of resources and waste generation. In recent years, new production technologies and strategies that break...... of geometric forms in concrete. The former was referred to as mould tectonics, the latter concrete tectonics. A study of the concepts of ‘New Production Philosophy’, ‘Mass-customization’, and Digital Tectonics is presented as a basis for investigating their use in concrete casting. Digital modelling...... plastic in which precision is maintained. The ability to reuse the PETG moulds makes the technique a zero waste production. In general it was concluded that problems with existing techniques relate to production time, surface quality and precision and are caused by the use of mould fabrication technique...

  9. Crustal structure and rift tectonics across the Cauvery–Palar basin ...

    Indian Academy of Sciences (India)

    ping and Curie point isothermal surface for geothermal reconnaissance; J. Geophys. Res. 80 4461–4465. Biswas S K, Bhasin A L and Jokhan Ram 1993 Classifi- cation of Indian sedimentary basins in the framework of plate tectonics; In: Proceedings of the second seminar on petroliferous basins of India: Dehradun (eds) ...

  10. Is plate tectonis withstanding the test of time?

    Directory of Open Access Journals (Sweden)

    O. Shields

    1997-06-01

    Full Text Available Since the theory of plate tectonics was first proposed thirty years ago, some problems have arisen in its practical application. These call into question its fundamental assumptions of horizontal plate motion, hotspot fixity, true polar wander, Panthalassa, and the Earth’s constant size while leaving seafloor spreading and subduction intact. A rapidity expanding earth solves these problems and privides an alternative viewpoint worth reconsidering.

  11. Do cratons preserve evidence of stagnant lid tectonics?

    Directory of Open Access Journals (Sweden)

    Derek Wyman

    2018-01-01

    Full Text Available Evidence for episodic crustal growth extending back to the Hadean has recently prompted a number of numerically based geodynamic models that incorporate cyclic changes from stagnant lid to mobile lid tectonics. A large part of the geologic record is missing for the times at which several of these cycles are inferred to have taken place. The cratons, however, are likely to retain important clues relating to similar cycles developed in the Mesoarchean and Neoarchean. Widespread acceptance of a form of plate tectonics by ∼3.2 Ga is not at odds with the sporadic occurrence of stagnant lid tectonics after this time. The concept of scale as applied to cratons, mantle plumes and Neoarchean volcanic arcs are likely to provide important constraints on future models of Earth's geodynamic evolution. The Superior Province will provide some of the most concrete evidence in this regard given that its constituent blocks may have been locked into a stagnant lid relatively soon after their formation and then assembled in the next global plate tectonic interval. Perceived complexities associated with inferred mantle plume – volcanic arc associations in the Superior Province and other cratons may be related to an over estimation of plume size. A possible stagnant lid episode between ∼2.9 Ga and ∼2.8 Ga is identified by previously unexplained lapses in volcanism on cratons, including the Kaapvaal, Yilgarn and Superior Province cratons. If real, then mantle dynamics associated with this episode likely eliminated any contemporaneous mantle plume incubation sites, which has important implications for widespread plumes developed at ∼2.7 Ga and favours a shallow mantle source in the transition zone. The Superior Province provides a uniquely preserved local proxy for this global event and could serve as the basis for detailed numerical models in the future.

  12. Florida: A Jurassic transform plate boundary

    Science.gov (United States)

    Klitgord, Kim D.; Popenoe, Peter; Schouten, Hans

    1984-01-01

    Magnetic, gravity, seismic, and deep drill hole data integrated with plate tectonic reconstructions substantiate the existence of a transform plate boundary across southern Florida during the Jurassic. On the basis of this integrated suite of data the pre-Cretaceous Florida-Bahamas region can be divided into the pre-Jurassic North American plate, Jurassic marginal rift basins, and a broad Jurassic transform zone including stranded blocks of pre-Mesozoic continental crust. Major tectonic units include the Suwannee basin in northern Florida containing Paleozoic sedimentary rocks, a central Florida basement complex of Paleozoic age crystalline rock, the west Florida platform composed of stranded blocks of continental crust, the south Georgia rift containing Triassic sedimentary rocks which overlie block-faulted Suwannee basin sedimentary rocks, the Late Triassic-Jurassic age Apalachicola rift basin, and the Jurassic age south Florida, Bahamas, and Blake Plateau marginal rift basins. The major tectonic units are bounded by basement hinge zones and fracture zones (FZ). The basement hinge zone represents the block-faulted edge of the North American plate, separating Paleozoic and older crustal rocks from Jurassic rifted crust beneath the marginal basins. Fracture zones separate Mesozoic marginal sedimentary basins and include the Blake Spur FZ, Jacksonville FZ, Bahamas FZ, and Cuba FZ, bounding the Blake Plateau, Bahamas, south Florida, and southeastern Gulf of Mexico basins. The Bahamas FZ is the most important of all these features because its northwest extension coincides with the Gulf basin marginal fault zone, forming the southern edge of the North American plate during the Jurassic. The limited space between the North American and the South American/African plates requires that the Jurassic transform zone, connecting the Central Atlantic and the Gulf of Mexico spreading systems, was located between the Bahamas and Cuba FZ's in the region of southern Florida. Our

  13. Active tectonics around the Mediterranean region: site studies and application of new methodologies

    Directory of Open Access Journals (Sweden)

    Luigi Cucci

    2013-01-01

    Full Text Available More than 25 years have passed since the definition of Active Tectonics as "tectonic movements that are expected to occur within a future time span of concern to society", formulated in a milestone book by the National Research Council on this topic (Studies in Geophysics, Active Tectonics, National Academy Press, Washington, D.C. 1986, and those words have still to be considered the most suitable and exhaustive way to explain this branch of the Earth Sciences. Indeed only bridging together basic studies ("tectonic movements", rates of occurrence ("time span" and hazard assessment ("society" can we fully evaluate ongoing tectonic activity and its associated hazards. The broad Mediterranean Sea region is a paradigmatic area from this point of view, as on one hand this region displays in a relatively limited geographic extent a great variety of tectonic processes such as plate collision, subduction, volcanic activity, large-magnitude earthquakes, active folding and faulting, vertical uplift and/or subsidence. On the other hand, all the above mentioned tectonic processes can potentially affect a total population of about 450 million, mostly concentrated in fast-growing urban areas and/or close to industrial compounds and critical facilities often located nearby hazard sources. […

  14. Mechanics and Partitioning of Deformation of the Northwestern Okhostk Plate, Northeast Russia

    Science.gov (United States)

    Hindle, D.; Mackey, K.; Fujita, K.

    2007-12-01

    The tectonic evolution and present day deformation of northeastern Russia remains one of the major challenges in plate tectonics. Arguments over the existence of at least a separate Okhotsk plate between North America and Eurasia appear to be resolved on the basis of the latest GPS studies combined with elastic modeling. The question of the mechanical behaviour of the Okhotsk plate, caught between the slowly, obliquely converging North American and Eurasian plates now becomes important. We present an analysis of geological lineaments, micro-seismicity, total seismic moment release and seismic deformation rate and GPS campaign data and global plate tectonic model data (REVEL) to estimate the likelihood of future seismicity and the relative amount of elastic and viscous deformation of the lithosphere of the northwestern Okhotsk plate. We find that it is likely that the Okhotsk plate is cracked into slivers, but that rates of relative motion of these slivers are close to indistinguishable from the behaviour of a single, rigid plate. The analysis also suggests the upper bound for large earthquakes in the region to be Mw 7-7.5 which we expect to occur only on the plate boundary fault itself. This fits geological evidence for a long term offset rate 5-10 times higher on the major plate boundary fault than other lineaments cutting the Okhotsk plate itself.

  15. Global Models of Ridge-Push Force, Geoid, and Lithospheric Strength of Oceanic plates

    Science.gov (United States)

    Mahatsente, Rezene

    2017-12-01

    An understanding of the transmission of ridge-push related stresses in the interior of oceanic plates is important because ridge-push force is one of the principal forces driving plate motion. Here, I assess the transmission of ridge-push related stresses in oceanic plates by comparing the magnitude of the ridge-push force to the integrated strength of oceanic plates. The strength is determined based on plate cooling and rheological models. The strength analysis includes low-temperature plasticity (LTP) in the upper mantle and assumes a range of possible tectonic conditions and rheology in the plates. The ridge-push force has been derived from the thermal state of oceanic lithosphere, seafloor depth and crustal age data. The results of modeling show that the transmission of ridge-push related stresses in oceanic plates mainly depends on rheology and predominant tectonic conditions. If a lithosphere has dry rheology, the estimated strength is higher than the ridge-push force at all ages for compressional tectonics and at old ages (>75 Ma) for extension. Therefore, under such conditions, oceanic plates may not respond to ridge-push force by intraplate deformation. Instead, the plates may transmit the ridge-push related stress in their interior. For a wet rheology, however, the strength of young lithosphere (stress may dissipate in the interior of oceanic plates and diffuses by intraplate deformation. The state of stress within a plate depends on the balance of far-field and intraplate forces.

  16. Is There Really A North American Plate?

    Science.gov (United States)

    Krill, A.

    2011-12-01

    Lithospheric plates are typically identified from earthquake epicenters and evidence such as GPS movements. But no evidence indicates a plate boundary between the North American and South American Plates. Some plate maps show them separated by a transform boundary, but it is only a fracture zone. Other maps show an "undefined plate boundary" or put no boundary between these two plates (check Google images). Early plate maps showed a single large American Plate, quite narrow east of the Caribbean Plate (Le Pichon 1968, Morgan 1968). The North and South American Plates became established by the leading textbook Earth (Press & Siever 1974). On their map, from a Scientific American article by John Dewey (1972), these new plates were separated by an "uncertain plate boundary." The reasons for postulating a North American Plate were probably more psychological than geological. Each of the other continents of the world had its own plate, and North American geologists naturally wanted theirs. Similarly, European geographers used to view Europe as its own continent. A single large plate should again be hypothesized. But the term American Plate would now be ambiguous ("Which plate, North or South?") Perhaps future textbook authors could call it the "Two-American Plate." Textbook authors ultimately decide such global-tectonic matters. I became aware of textbook authors' opinions and influence from my research into the history of Alfred Wegener's continental drift (see Fixists vs. Mobilists by Krill 2011). Leading textbook author Charles Schuchert realized that continental drift would abolish his cherished paleogeographic models of large east-west continents (Eria, Gondwana) and small oceans (Poseiden, Nereis). He and his junior coauthors conspired to keep drift evidence out of their textbooks, from the 1934-editions until the 1969-editions (Physical Geology by Longwell et al. 1969, Historical Geology by Dunbar & Waage 1969). Their textbooks ruled in America. Textbooks

  17. Plate-wide stress relaxation explains European Palaeocene basin inversions

    DEFF Research Database (Denmark)

    Nielsen, S.B.; Thomsen, Erik; Hansen, D.L.

    2005-01-01

    of the in-plane tectonic stress. The onset of relaxation inversions was plate-wide and simultaneous, and may have been triggered by stress changes caused by elevation of the North Atlantic lithosphere by the Iceland plume or the drop in NS convergence rate between Africa and Europe....

  18. Waffle production: influence of batter ingredients on sticking of waffles at baking plates-Part II: effect of fat, leavening agent, and water.

    Science.gov (United States)

    Huber, Regina; Schoenlechner, Regine

    2017-05-01

    Fresh egg waffles are continuously baked in tunnel baking ovens in industrial scale. Waffles that partly or fully stick to the baking plates cause significant product loss and increased costs. The aim of this study was, therefore, to investigate the effect of different recipe ingredients on the sticking behavior of waffles. In this second part, ingredients investigated were different leavening agents (sodium acid pyrophosphate, ammonium bicarbonate, magnesium hydroxide carbonate, or monocalcium phosphate), different fat sources (rapeseed oil, cocos fat, butter, or margarine), and different water sources (tap water 12°dH and distilled water). Within the different types of fats, solid fats with high amount of short-chain fatty acids (cocos fat or butter) decreased the number of sticking waffles compared to liquid oils (rapeseed oil). Regarding leavening agents, magnesium hydroxide carbonate and ammonium bicarbonate were superior to sodium acid pyrophosphate or monocalcium phosphate. Between the two water sources, effects were small.

  19. Dynamics of Mid-Palaeocene North Atlantic rifting linked with European intra-plate deformations

    NARCIS (Netherlands)

    Nielsen, S.B.; Stephenson, R.A.; Thomsen, E.

    2007-01-01

    The process of continental break-up provides a large-scale experiment that can be used to test causal relations between plate tectonics and the dynamics of the Earth's deep mantle. Detailed diagnostic information on the timing and dynamics of such events, which are not resolved by plate kinematic

  20. HVDC Ground Electrodes and Tectonic Setting

    Science.gov (United States)

    Freire, P. F.; Pereira, S. Y.

    2017-12-01

    Ground electrodes in HVDC transmission are huge grounding systems for the DC part of the converter substation, about 1 km wide, sized to inject in the ground DC currents up to 3.5 kA. This work presents an analysis of how the tectonic setting at converter substation location is determinant for the search of the best electrode location (Site Selection) and on its design and performance. It will briefly present the author experience on HVDC electrode design, summarized as follows: Itaipu - Foz do Iguaçu electrodes (transmitter side) located in the middle of Paraná Sedimentary Basin, and Ibiúna electrodes (receiving side) on the border of the basin, 6 km from the geological strike, where the crystalline basement outcrops in São Paulo state; Madeira River - North electrodes (transmitting side) located on the Northwest border of South Amazon Craton, where the crystalline basement is below a shallow sediments layer, and South electrodes (receiving side) located within Paraná Sedimentary Basin; Chile - electrodes located on the Andean forearc, where the Nazca Plate plunges under the South American Plate; Kenya - Ethiopia - electrodes located in the African Rift; Belo Monte - North electrodes (transmitter side) located within the Amazonian Sedimentary Basin, about 35 km of its South border, and South electrodes (receiving side) within Paraná Sedimentary Basin (bipole 1) and on crystalline metamorphic terrain "Brasília Belt" (bipole 2). This diversity of geological conditions results on ground electrodes of different topologies and dimensions, with quite different electrical and thermal performances. A brief study of the geology of the converter stations regions, the so-called Desktop Study, allows for the preview of several important parameters for the site selection and design of the electrodes, such as localization, type, size and estimate of the interference area, which are important predictors of the investment to be made and indications of the design to be

  1. Cenozoic tectonic jumping and implications for hydrocarbon accumulation in basins in the East Asia Continental Margin

    Science.gov (United States)

    Suo, Yanhui; Li, Sanzhong; Yu, Shan; Somerville, Ian D.; Liu, Xin; Zhao, Shujuan; Dai, Liming

    2014-07-01

    Tectonic migration is a common geological process of basin formation and evolution. However, little is known about tectonic migration in the western Pacific margins. This paper focuses on the representative Cenozoic basins of East China and its surrounding seas in the western Pacific domain to discuss the phenomenon of tectonic jumping in Cenozoic basins, based on structural data from the Bohai Bay Basin, the South Yellow Sea Basin, the East China Sea Shelf Basin, and the South China Sea Continental Shelf Basin. The western Pacific active continental margin is the eastern margin of a global convergent system involving the Eurasian Plate, the Pacific Plate, and the Indian Plate. Under the combined effects of the India-Eurasia collision and retrogressive or roll-back subduction of the Pacific Plate, the western Pacific active continental margin had a wide basin-arc-trench system which migrated or ‘jumped’ eastward and further oceanward. This migration and jumping is characterized by progressive eastward younging of faulting, sedimentation, and subsidence within the basins. Owing to the tectonic migration, the geological conditions associated with hydrocarbon and gashydrate accumulation in the Cenozoic basins of East China and its adjacent seas also become progressively younger from west to east, showing eastward younging in the generation time of reservoirs, seals, traps, accumulations and preservation of hydrocarbon and gashydrate. Such a spatio-temporal distribution of Cenozoic hydrocarbon and gashydrate is significant for the oil, gas and gashydrate exploration in the East Asian Continental Margin. Finally, this study discusses the mechanism of Cenozoic intrabasinal and interbasinal tectonic migration in terms of interplate, intraplate and underplating processes. The migration or jumping regimes of three separate or interrelated events: (1) tectonism-magmatism, (2) basin formation, and (3) hydrocarbon-gashydrate accumulation are the combined effects of the

  2. Rheological and structural inheritance : key parameters for intra-plate deformation. A study based on analogue models

    NARCIS (Netherlands)

    Calignano, E.

    2015-01-01

    Mountain ranges are impressive tectonic features that characterize the Earth’s surface. Their formation is often associated with regions where two tectonic plates, making up the Earth surface, collide, as in the case of the Himalaya. While the surface is forced to uplift, the displacement of rocks

  3. Geodynamical Nature of the Formation of Large Plates of Platforms, Jointed in North Caspian Oil and Gas Basin

    Science.gov (United States)

    Seitov, Nassipkali; Tulegenova, Gulmira P.

    2016-01-01

    This article addresses the problems of tectonic zoning and determination of geodynamical nature of the formation of jointed tectonic structures within the North Caspian oil and gas basin, represented by Caspian Depression of Russian platform of East European Pre-Cambrian Craton and plate ancient Precambrian Platform stabilization and Turan…

  4. Seismicity of the Earth 1900-2007, Caribbean Plate and Vicinity

    Science.gov (United States)

    Benz, Harley M.; Tarr, Arthur C.; Hayes, Gavin P.; Villaseñor, Antonio; Furlong, Kevin P.; Dart, Richard L.; Rhea, Susan

    2010-01-01

    Extensive diversity of tectonic regimes characterizes the perimeter of the Caribbean plate, involving no fewer than four major adjacent plates (North America, South America, Nazca, and Cocos). Inclined zones of deep earthquakes (Wadati-Benioff zones), deep ocean trenches, and arcs of volcanoes clearly indicate subduction of oceanic lithosphere along the Central American and Atlantic Ocean margins of the Caribbean plate, while shallow seismicity and focal mechanisms of major shocks in Guatemala, northern Venezuela, and the Cayman Ridge and Cayman Trench indicate transform fault and pull-apart basin tectonics.

  5. Geoprospective study of a nuclear waste repository. Prospective tectonics: convergent and divergent episodes, evolution of stress during the next 100,000 years

    International Nuclear Information System (INIS)

    Gros, Y.

    1985-01-01

    Within the frame of a contract with the CEC, dealing with storage and disposal of radioactive wastes in geological formations, the B.R.G.M. has been involved in a research on prospective tectonics. Within the Western European continental plate, since Mesozoic times, one sees the alternation or succession of convergent and divergent tectonic episodes. These tectonic episodes, although representing geologically discontinuous phenomena, still have time periods of between 4 to 40 millions years. These tectonic phenomena are the cause of the formation or reactivation, at all scales in the continental plate, of brittle, fault-like structures. Tectonic analysis and the in situ measures of stress and the earthquake focal phenomena show that, from the lower Quaternary to the present, the Western European continental plate has been subjected to NNW to SSE convergent stress. A study of the arrangement of European and African plates in the Western Mediterranean shows that the entire region, is undergoing a period of continental collision. The change in the process implies a westerly continental drift of the Spanish plate, a movement which would take several million years. On the Western European scale, the most likely hypothesis during the next 100,000 years is the persistance of the present stress trending approximately N-5. On the other hand, on a local scale, reorganisations of this stress are possible, owing to the presence of tectonic or lithological heterogeneities

  6. Upright folding during extensional and transtensional tectonics

    Science.gov (United States)

    Teyssier, Christian; Fossen, Haakon; Rey, Patrice F.; Whitney, Donna L.

    2017-04-01

    Upright folds are common structures that develop in response to horizontal shortening in layered material, for example in foreland basins that surround orogens. While the contractional nature of these folds is not in doubt, interpretation of their tectonic setting needs careful consideration. Here we focus on two examples: (1) folds developed in transtension; and (2) folds developed during the flow of deep crust in response to lithospheric extension. In both cases we consider folding of nearly horizontal layers that are either primary (bedding) or secondary (foliation). Strain theory inspired by John Ramsay's work makes predictions for the behavior of material lines and planes as well as strain axes (instantaneous, finite) during transtensional deformation. Results show: folds can form in transtension; fold hinges rotate toward the direction of divergence (and not the shear zone boundary as they do in transpression), providing unique insight into ancient plate motions; fold tightness is controlled by the obliquity of divergence and not finite strain; hinge parallel stretching is always greater than hinge-perpendicular shortening, resulting in constriction strain and boudinage of fold hinges. Taken together these results provide a rigorous framework for interpreting field observations where structures are complex and boundary conditions unclear. These principles are applied to various tectonic settings ranging from active tectonic regions of oblique divergence in western North America to ancient folding that developed during oblique extension of the Western Gneiss Region, deposition of Devonian basins, and exhumation of ultrahigh-pressure rocks in the Norwegian Caledonides. The other class of upright folds that form during extension may require revision of the tectonic interpretation of structural overprints in orogenic cores, for example in gneiss/migmatite domes. Dynamic modeling of extension of thick/hot crust predicts a positive feedback between extension of

  7. Properties of light transition radiation of 660 MeV proton inclined incidence (γ=1.7) on a thick nickel plate. II

    International Nuclear Information System (INIS)

    Zrelov, V.P.; Pavlovic, P.; Ruzicka, J.

    1975-01-01

    The basic properties of transition radiation in the visible fraction of the spectrum have been calculated for 660 MeV protons (γ=1.7) obliquely incident on a thick nickel plate in vacuum. The angular distributions of the summary radiation (i.e. the sums of radiations of various polarizations) both 'forward' and 'backward' for different azimuthal planes are presented in tables and diagrams for different particle inclination angles to the separation boundary. The examples of angular distributions of radiation having various polarizations (at the inclination angle of 45 0 ) show that they differ considerably. The spectra of summary radiation are of a monotonous character. The calculations have shown that in a relativistic case the forward radiation is concentrated near the direction of particle motion and backward radiation moves in an opposite direction with respect to that of the particle inclination. The dependence of the total yield of forward and backward transition radiations upon the particle inclination angle is approximately cos 2 psi. (Auth.)

  8. Relative tectonic activity classification in the Kermanshah area, western Iran

    Science.gov (United States)

    Arian, M.; Aram, Z.

    2014-12-01

    Due to the closing of the subduction zone and the collision of the Arabian and Eurasian plates, the High Zagros region has always been affected by a wide range of tectonic variations. In this research, the Gharasu River basin, which is located in the Kermanshah area, was selected as the study area, six geomorphic indices were calculated, and the results of each one were divided into three classes. Then, using the indices, relative tectonic activity was calculated, and their values were classified and analysed in four groups. Regions were identified as very high, high, moderate and low. In analysing the results and combining them with field observations and regional geology, the results were often associated and justified with field evidence. The highest value is located on the Dokeral anticline in the crush zone in Zagros. Most of the areas with high and moderate values of Index of Active Tectonics (IAT) are also located in the crush zone in Zagros. Crushing in this zone is because of the main fault mechanism of the Zagros region. The result in this paper confirms previous research in this region. At the eastern end of the study area, the value of Iat is high, which could be the result of the Sarab and Koh-e Sefid fault mechanisms.

  9. ITRF2014 plate motion model

    Science.gov (United States)

    Altamimi, Zuheir; Métivier, Laurent; Rebischung, Paul; Rouby, Hélène; Collilieux, Xavier

    2017-06-01

    For various geodetic and geophysical applications, users need to have access to a plate motion model (PMM) that is consistent with the ITRF2014 frame. This paper describes the approach used for determining a PMM from the horizontal velocities of a subset of the ITRF2014 sites away from plate boundaries, Glacial Isostatic Adjustment regions and other deforming zones. In theory it would be necessary to include in the inversion model a translational motion vector (called in this paper origin rate bias, ORB) that would represent the relative motion between the ITRF2014 origin (long-term averaged centre of mass of the Earth as sensed by SLR) and the centre of tectonic plate motion. We show that in practice, the magnitude of the estimated ORB is strongly dependent on the selection of ITRF2014 sites used for the PMM adjustment. Its Z-component can in particular range between 0 and more than 1 mm yr-1 depending on the station network used, preventing any geophysical interpretation of the estimated value. Relying on rigorous statistical criteria, the site selection finally adopted for the ITRF2014-PMM adjustment leads to a relatively small ORB (0.30 ± 0.18 mm yr-1 in the Z-component), which is statistically insignificant at the 2-sigma level, but also according to an F-ratio test. Therefore we opted for an ITRF2014-PMM without estimating the ORB, which in turn accommodates geodetic applications that require access to the ITRF2014 frame through pure plate rotation poles.

  10. Simple radiography by Imaging Plate

    Energy Technology Data Exchange (ETDEWEB)

    Takata, Shigeru; Koyama, Motoko; Tanizaki, Yoshiyuki [Tokyo Metropolitan Industrial Technology Research Insitute, Tokyo (Japan)

    1998-12-31

    Photo-stimulable phosphor is a material which emits luminescence by incitement of light. As useful photo-stimulable phosphor, alkali halide, like BaFBr: Eu, II - VI compound, like SrS: Eu and oxide, such as Al{sub 2}O{sub 3}: Care reported at present. Imaging Plate is a popular name of products, which is composed of thin layer of the phosphor fixed plastic plate. Photo-stimulable luminescence of Imaging Plate is emitted by scanning with narrow beam of incitement light. The light of luminescence is separated from incitement light by filter and it`s intensity is measured. The intensity of luminescence is proportional to absorbed dose of Imaging Plate from incident radiation. The map of luminescence intensity makes radiation image like radiograph taken by X-ray film. Reusability and usability of digital image are another advantage. The problem to solve of Imaging Plate are less resolution than X-ray film, expensive reading instrument and fading, which means decrease of luminescence intensity depend on elapse time after irradiation. High sensitivity of Imaging Plate makes possible of simple radiography by small radiation source. In Japanese law, sealed radioisotopes source less than 3.7 MBq can use without permission and register. If radiograph can be taken by sealed source less than 3.7 MBq, application of radiography is widely developed. So we try to take radiographs of some objects using Imaging Plate and sealed radioisotope sources under 3.7 MBq. As the result, useful radiographs are taken under conditions that exposure time is more than a few hours and distance between the source and the Plate is less than 30 cm. Quality of the image is poor than general radiograph by large radiation source. But the simple radiography taken by small source is of great value. (J.P.N.)

  11. Create Your Plate

    Medline Plus

    Full Text Available ... Pacific Islanders American Indian/Alaska Native Programs Older Adults Family Link Diabetes EXPO Upcoming Diabetes EXPOs EXPO ... Plate! Click on the plate sections below to add your food choices. Reset Plate Share Create Your ...

  12. Archaean tectonic systems: A view from igneous rocks

    Science.gov (United States)

    Moyen, Jean-François; Laurent, Oscar

    2018-03-01

    with somewhat different tectonic systems. In particular, the familiar distinction between collision, arcs, ridges and hotspots seems to blur in the Archaean. Rather, the large-scale geochemical pattern reveals a long-lived, altered and periodically resurfaced basaltic crust. This protocrust is reworked, through a range of processes occurring at various depths that correspond to a progressive stabilization of burial systems and the establishment of true subductions. A punctuated onset of global plate tectonics is unlikely to have occurred, but rather short-term episodes of proto-subduction in the late Archaean evolved over time into longer-term, more stable style of plate tectonics as mantle temperature decayed.

  13. Tectonic pattern of the Azores spreading centre and triple junction

    Science.gov (United States)

    Searle, Roger

    1980-12-01

    The major tectonic elements of the Azores triple junction have been mapped using long-range side-scan sonar. The data enable the Mid-Atlantic Ridge axis to be located with a precision of a few kilometres. Major faults and other tectonic and volcanic elements of the ridge maintain their regional trend of 010° to 020° past the triple junction area. There is no oblique spreading, and only minor transform offsets of the Mid-Atlantic Ridge occur here. The main effect of the triple junction or Azores hot spot is to diminish the amplitude of the median valley to 200 m or less. There is no axial high: a topographic high seen on several profiles is located to the east of the Mid-Atlantic Ridge spreading axis and does not appear to have any fundamental significance. The third arm of the triple junction includes the Azores srreading centre which appears to have developed as a series of en echelon rifted basins (the Terceira Rift) extending from Formigas Trough at 36.8°N, 24.5°W to a point near 39.3°N, 28.8°W. There are indications that recent activity in the spreading centre may be concentrated in a series of ridges which flank the older rifted basins. Until recently the northwest end of the Terceira Rift was connected to the Mid-Atlantic Ridge axis either directly at an RRR junction, or via a transform fault. The triple junction has probably moved south during the last 6 Ma to a positin on the Mid-Atlantic Ridge near 38.7°N. Initiation of the Azores spreading centre may have occurred during the 36 Ma B.P. rearrangement of poles, with an RFF triple junction north from the East Azores fracture zone to the North Azores fracture zone and transferring a wedge of European plate to the African plate. The tectonic elements revealed by this study are in good agreement with inferred earthquake mechanisms and with the RM2 plate tectonic model of Minster and Jordan, but east-west motion between North America and Africa does not seem to be compatible with the other motions at the

  14. Field-based evaluations of horizontal flat-plate fish screens, II: Testing of a unique off-stream channel device - The Farmers Screen

    Science.gov (United States)

    Mesa, Matthew G.; Rose, Brien P.; Copeland, Elizabeth S.

    2012-01-01

    Screens are installed at water diversion sites to reduce entrainment of fish. Recently, the Farmers Irrigation District (Oregon) developed a unique flat-plate screen (the “Farmers Screen”) that operates passively and may offer reduced installation and operating costs. To evaluate the effectiveness of this screen on fish, we conducted two separate field experiments. First, juvenile coho salmon Oncorhynchus kisutch were released over a working version of this screen under a range of inflows (0.02–0.42 m3/s) and diversion flows (0.02–0.34 m3/s) at different water depths. Mean approach velocities ranged from 0 to 5 cm/s and sweeping velocities ranged from 36 to 178 cm/s. Water depths over the screen surface ranged from 1 to 25 cm and were directly related to inflow. Passage of fish over the screen under these conditions did not severely injure them or cause delayed mortality, and no fish were observed becoming impinged on the screen surface. Second, juvenile coho salmon and steelhead O. mykiss were released at the upstream end of a 34-m flume and allowed to volitionally move downstream and pass over a 3.5-m section of the Farmers Screen to determine whether fish would refuse to pass over the screen after encountering its leading edge. For coho salmon, 75–95% of the fish passed over the screen within 5 min and 82–98% passed within 20 min, depending on hydraulic conditions. For steelhead, 47–90% of the fish passed over the screen within 5 min and 79–95% passed within 20 min. Our results indicate that when operated within its design criteria, the Farmers Screen provides safe and efficient downstream passage of juvenile salmonids under a variety of hydraulic conditions.

  15. TERRAIN TECTONICS OF THE CENTRAL ASIAN FOLDED BELT

    Directory of Open Access Journals (Sweden)

    M. M. Buslov

    2014-01-01

    Full Text Available The terrain analysis concept envisages primarily a possibility of approximation of fragments / terrains of various geodynamic settings which belong to different plates. The terrain analysis can supplement the theory of plate tectonics in solving problems of geodynamics and tectonics of regions of the crust with complex structures. The Central Asian belt is among such complicated regions. Terrain structures occurred as a result of combined movements in the system of 'frontal' and/or oblique subduction – collision. In studies of geological objects, it is required first of all to prove their (vertical and horizontal autochthony in relations to each other and then proceed to paleogeodynamic, paleotectonic and paleogeographic reconstructions. Obviously, such a complex approach needs data to be obtained by a variety of research methods, including those applied to study geologic structures, stratigraphy, paleontology, paleogeography, lithothlogy, geochemistry, geochronology, paleomagnetism etc. Only by correlating such data collected from inter-disciplinary studies of the regions, it is possible to establish reliable characteristics of the geological settings and avoid mistakes and misinterpretations that may be associated with the 'stratigraphic' approach to solutions of both regional and global problems of geodynamics and tectonics of folded areas. The terrain analysis of the Central Asian folded belt suggests that its tectonic structure combines marginal continental rock complexes that were formed by the evolution of two major oceanic plates. One of them is the plate of the Paleo-Asian Ocean. As the analogue of the current Indo-Atlantic segment of Earth, it is characterised by the presence of continental blocks in the composition of the oceanic crust and the formation of oceanic basins resulting from the breakup of Rodinia and Gondvana. In the course of its evolution, super-continents disintegrated, and the blocks were reunited into the Kazakhstan

  16. Measurements of Active Tectonic Deformation on the Guerrero Coast, Mexico

    Science.gov (United States)

    Ramirez, T.; Cundy, A.; Carranza-Edwards, A.; Morales, E.; Kostoglodov, V.; Urrutia-Fucugauchi, J.

    2004-12-01

    The study of tectonic deformation rates using displaced shoreline features is relatively well-established, and has provided much useful information on seismic hazard. Such studies have frequently been complemented by analysis of the coastal sedimentary record, where past marine to terrestrial environmental changes (and vice versa) may be recorded by clear changes in stratigraphy. Studies of this type are particularly valuable for tectonically-active areas where the preservation of former shoreline features is poor, or where long-term subsidence has resulted in their erosion, drowning or burial. The specific objective of this study is to derive rates of tectonic deformation from geomorphic and stratigraphic studies of the Guerrero coastal area, and to examine the feasibility of this stratigraphic approach in the coastal lagoons of the Mexican Pacific coast, in the Guerrero gap. The Guerrero gap coastal area, where a major earthquake is expected to occur, parallels the Cocos plate subduction zone. Here convergence rates vary from 5.2 cm/yr to 5.8 cm/yr. The Guerrero gap has experienced several historical earthquakes, notably the 1911 (7.8 Ms). However, no large magnitude events since the 1911 earthquake and only a few Ms~6 events have occurred near the Guerrero gap edges. It is expected that a major interplate earthquake of estimated magnitude Mw=8.1 to 8.4 has a high probability to occur. Landforms within the Guerrero gap indicate that the coast is subsiding. A series of key indicators such as elongated islands reminiscent of ancient barriers, submerged barriers island, extensive marshy environments, increased depths in the lagoons, and submerged anthropogenic features (shell mounds), among others, suggest active tectonic subsidence of the coast. In contrast, the adjacent northwest area off the Guerrero gap exhibits landforms characteristic of tectonic uplift (marine terraces and uplifted beach ridges), indicating a different seismo-tectonic regime northwest of the

  17. Tectonic inheritance, reactivation and long term fault weakening processes

    Science.gov (United States)

    Holdsworth, Bob

    2017-04-01

    This talk gives a geological review of weakening processes in faults and their long-term effect on reactivation and tectonic inheritance during crustal deformation. Examples will be drawn from the Atlantic margins, N America, Japan and the Alps. Tectonic inheritance and reactivation are fundamentally controlled by the processes of stress concentration and shear localisation manifested at all scales in the continental lithosphere. Lithosphere-scale controls include crustal thickness, thermal age and the boundary conditions imposed by the causative plate tectonic processes during extension. At the other end of the scale range, grain-scale controls include local environmental controls (depth, stress, strain rate), rock composition, grainsize, fabric intensity and the presence of fluids or melt. Intermediate-scale geometric controls are largely related to the size, orientation and interconnectivity of pre-existing anisotropies. If reactivation of pre-existing structures occurs, it likely requires a combination of processes across all three scale ranges to be favourable. This can make the unequivocal recognition of inheritance and reactivation difficult. Large (e.g. crustal-scale) pre-existing structures are especially important due to their ability to efficiently concentrate stress and localise strain. For big faults (San Andreas, Great Glen, Median Tectonic Line), detailed studies of the associated exposed fault rocks indicate that reactivation is linked to the development of strongly anisotropic phyllosilicate-rich fault rocks that are weak (e.g. friction coefficients as low as 0.2 or less) under a broad range of deformation conditions. In the case of pre-existing regional dyke swarms (S Atlantic, NW Scotland) - which may themselves track deep mantle fabrics at depth - multiple reactivation of dyke margins is widespread and may preclude reactivation of favourably oriented local basement fabrics. In a majority of cases, pre-existing structures in the crust are

  18. Contrasting styles of (U)HP rock exhumation along the Cenozoic Adria-Europe plate boundary (Western Alps, Calabria, Corsica)

    Science.gov (United States)

    Malusà, Marco G.; Faccenna, Claudio; Baldwin, Suzanne L.; Fitzgerald, Paul G.; Rossetti, Federico; Balestrieri, Maria Laura; Danišík, Martin; Ellero, Alessandro; Ottria, Giuseppe; Piromallo, Claudia

    2015-06-01

    Since the first discovery of ultrahigh pressure (UHP) rocks 30 years ago in the Western Alps, the mechanisms for exhumation of (U)HP terranes worldwide are still debated. In the western Mediterranean, the presently accepted model of synconvergent exhumation (e.g., the channel-flow model) is in conflict with parts of the geologic record. We synthesize regional geologic data and present alternative exhumation mechanisms that consider the role of divergence within subduction zones. These mechanisms, i.e., (i) the motion of the upper plate away from the trench and (ii) the rollback of the lower plate, are discussed in detail with particular reference to the Cenozoic Adria-Europe plate boundary, and along three different transects (Western Alps, Calabria-Sardinia, and Corsica-Northern Apennines). In the Western Alps, (U)HP rocks were exhumed from the greatest depth at the rear of the accretionary wedge during motion of the upper plate away from the trench. Exhumation was extremely fast, and associated with very low geothermal gradients. In Calabria, HP rocks were exhumed from shallower depths and at lower rates during rollback of the Adriatic plate, with repeated exhumation pulses progressively younging toward the foreland. Both mechanisms were active to create boundary divergence along the Corsica-Northern Apennines transect, where European southeastward subduction was progressively replaced along strike by Adriatic northwestward subduction. The tectonic scenario depicted for the Western Alps trench during Eocene exhumation of (U)HP rocks correlates well with present-day eastern Papua New Guinea, which is presented as a modern analog of the Paleogene Adria-Europe plate boundary.

  19. Petrogenesis of the NE Gondwanan uppermost Ediacaran-Lower Cretaceous siliciclastic sequence of Jordan: Provenance, tectonic, and climatic implications

    Science.gov (United States)

    Amireh, Belal S.

    2018-04-01

    Detrital framework modes of the NE Gondwanan uppermost Ediacaran-Lower Cretaceous siliciclastic sequence of Jordan are determined employing the routine polarized light microscope. The lower part of this sequence constitutes a segment of the vast lower Paleozoic siliciclastic sheet flanking the northern Gondwana margin that was deposited over a regional unconformity truncating the outskirts of the East African orogen in the aftermath of the Neoproterozoic amalgamation of Gondwana. The research aims to evaluate the factors governing the detrital light mineral composition of this sandstone. The provenance terranes of the Arabian craton controlled by plate tectonics appear to be the primary factor in most of the formations, which could be either directly inferred employing Dickinson's compositional triangles or implied utilizing the petrographic data achieved and the available tectonic and geological data. The Arabian-Nubian Shield constitutes invariably the craton interior or the transitional provenance terrane within the NE Gondwana continental block that consistently supplied sandy detritus through northward-flowing braided rivers to all the lower Paleozoic formations. On the other hand, the Lower Cretaceous Series received siliciclastic debris, through braided-meandering rivers having same northward dispersal direction, additionally from the lower Paleozoic and lower-middle Mesozoic platform strata in the Arabian Craton. The formations making about 50% of the siliciclastic sequence represent a success for Dickinson's plate tectonics-provenance approach in attributing the detrital framework components primarily to the plate tectonic setting of the provenance terranes. However, even under this success, the varying effects of the other secondary sedimentological and paleoclimatological factors are important and could be crucial. The inapplicability of this approach to infer the appropriate provenance terranes of the remaining formations could be ascribed either to the

  20. Land and OBS recordings of tectonic tremor on New Zealand's Alpine Fault

    Science.gov (United States)

    Wech, A.; Boese, C. M.; Stern, T. A.; Townend, J.; Sheehan, A. F.; Collins, J. A.

    2012-12-01

    Tectonic tremor is characterized by persistent, low-frequency seismic energy seen at major plate boundaries. Although predominantly associated with subduction zones, tremor also occurs along the deep extension of the strike-slip San Andreas Fault. Here we present the observations of tectonic tremor along New Zealand's Alpine Fault, a major transform boundary that is late in its earthquake cycle using a combination of land and ocean-bottom seismometers (OBS). We report tectonic tremor that occurred on the central section of the Alpine Fault on 12 days between March 2009 and October 2011. Tremor hypocenters concentrate in the lower crust at the downdip projection of the Alpine Fault; coincide with a zone of high P-wave attenuation (low Qp) and bright seismic reflections; occur in the 25-45 km depth range, below the seismogenic zone; and may define the deep plate boundary structure extending through the lower crust and into the upper mantle. We infer this tremor to represent slow slip on the deep extent of the Alpine Fault in a fluid-rich region marked by high attenuation and reflectivity. These observations provide the first indication of present-day displacement on the lower crustal portion of the Australia-Pacific transform plate boundary. Furthermore, the offshore observations—ground-truthed by onshore shallow borehole seismometers—demonstrate the potential utility of OBS experiments in better characterizing plate boundary processes.

  1. The Okhotsk Plate and the Eurasia-North America plate boundary zone.

    Science.gov (United States)

    Hindle, David; Mackey, Kevin

    2014-05-01

    The Eurasia-North America plate boundary zone transitions from spreading at rates of ~ 25mm/yr in the North Atlantic, to compression at rates of ~ 5mm/yr in the region of the Okhotsk plate. Because the pole of rotation between Eurasia and North America lies more or less on their mutual boundary, there is a linear change in rate along the boundary, and regions near the euler pole are subject to extremely low deformation rates. The Okhotsk - Eurasia - North America triple junction lies slightly south of the rotation pole, placing the Okhotsk plate entirely in a weakly contractional setting. Regions near the triple junction absorb 1mm/yr contraction. Further south, towards the shoreline of the Okhotsk sea, up to 5 mm/yr contraction may be absorbed within the plate. How shortening is accommodated across the boundary remains an open question. One possibility is wholesale extrusion of the entire Okhotsk plate (or possibly its northwestern corner) along two plate boundary strike slip faults (Eurasia-Okhostk and North America Okhotsk). The problem with this model is that the seismic record does not presently clearly support it, with the largest events distributed both within the plate interior and on its boundaries. This may suggest that instead, the Okhotsk plate, and particularly its north-western end, consists of a series of smaller blocks which shuffle against each other, partially accommodating extrusion, but also permitting some internal deformation and change of shape of the Okhotsk plate itself. We present analyses of the very sparse seismic record from the region, as well as geometric-kinematic, tectonic models of the possible deformation of northwest Okhotsk to try to better understand the different probabilities of how this slowly deforming plate boundary zone is behaving.

  2. Framework for Tectonic Thinking, a Conceptual Approach

    DEFF Research Database (Denmark)

    Garritzmann, Udo

    2017-01-01

    This research paper is a contribution to the field of architectural design theory in the area of tectonics. From the designer’s point of view, it will develop an overarching conceptual framework for tectonic thinking (FTT), which will serve as a tool for the comparative analysis and interpretation...... of a wide range of tectonic motifs and design positions. The understanding of tectonics will be broadened and differentiated. The conceptual framework will be developed in writing and in hand-drawn mappings. This comparative method assumes not one single, supposedly right, meaning of tectonics, but several...... a value judgement beforehand about any of these positions. Also a-tectonic design positions will be regarded as valid positions within this framework....

  3. The Arabia-India plate boundary unveiled

    Science.gov (United States)

    Fournier, M.; Chamot-Rooke, N. R.; Rodriguez, M.; Petit, C.; Huchon, P.; Beslier, M.; Hazard, B.

    2009-12-01

    Since the advent of Plate Tectonics, tectonic plate boundaries were explored on land as at sea for search of active faults where the destructive energy of earthquakes is released. Yet, some plate boundaries, less active or considered as less dangerous to humankind, escaped general attention and remained unknown to a large extent. Among them, the boundary between two major tectonic plates: Arabia and India. The Arabia-India motion is currently accommodated along the Owen Fracture Zone (OFZ) in the NW Indian Ocean, which connects the spreading centers of the Sheba and Carlsberg ridge system to the Makran subduction zone. We recently surveyed this fracture zone onboard the R/V Beautemps-Beaupré (Owen Cruise, March 2009) using a high-resolution deep-water multibeam echo-sounder. Bathymetric data reveal a spectacular submarine fault system running over a distance of 800 km between the Arabia-India-Somalia triple junction to the south and the Dalrymple Trough to the north. The morphology of the active faults is well preserved on the seafloor where fault scarps can be followed over hundreds of kilometres. The surficial trace of the faults is not obscured by the sediments of the aggrading deep-sea fan of the Indus River. The fault system is segmented in five main segments connected by pull apart basins. The length of the individual, apparently uninterrupted, segments is between 100 km and 220 km. The largest pull-apart basin at the latitude 20°N (20°N-Basin) corresponds to a right step-over of about 12 km between two fault segments. The 20°N-Basin is bounded by a normal fault scarp with a throw of 450-500 m. Numerous minor normal faults cutting the floor of the basin attest to recent activity. The 20°N-Basin is directly supplied in turbidity-current deposits by an active channel of the Indus fan. The preservation of tectonic features indicates that the dip-slip motion has exceeded the rate of burial by sediments. Some compressional structures are also deduced from

  4. Navigating Towards Digital Tectonic Tools

    DEFF Research Database (Denmark)

    Schmidt, Anne Marie Due; Kirkegaard, Poul Henning

    2006-01-01

    The computer holds a great potential to break down the barriers between architecture and the technical aspects relating to architecture, thus supporting innovative architecture with an inner correspondence between form and technique. While the differing values in architecture and technique can seem...... a tectonic tool should encompass. Secondly the ability and validity of the model are shown by applying it to a case study of Jørn Utzon’s work on Minor Hall in Sydney Opera House - for the sake of exemplification the technical field focused on in this paper is room acoustics. Thirdly the relationship between...

  5. Tectonic setting of the Seychelles, Mascarene and Amirante Plateaus in the Western Equatorial Indian Ocean

    International Nuclear Information System (INIS)

    Mart, Y.

    1988-01-01

    A system of marine plateaus occurs in the western equatorial Indian Ocean, forming an arcuate series of wide and shallow banks with small islands in places. The oceanic basins that surround the Seychelles - Amirante region are of various ages and reflect a complex seafloor spreading pattern. The structural analysis of the Seychelle - Amirante - Mascarene region reflects the tectonic evolution of the western equatorial Indian Ocean. It is suggested that due to the seafloor spreading during a tectonic stage, the Seychelles continental block drifted southwestwards to collide with the oceanic crust of the Mascarene Basin, forming an elongated folded structure at first, and then a subduction zone. The morphological similarity, the lithological variability and the different origin of the Seychelles Bank, the Mascarene Plateau and the Amirante Arc emphasizes the significant convergent effects of various plate tectonic processes on the development of marine plateaus

  6. Impacts and tectonism in Earth and moon history of the past 3800 million years

    Science.gov (United States)

    Stothers, Richard B.

    1992-01-01

    The moon's surface, unlike the Earth's, displays a comparatively clear record of its past bombardment history for the last 3800 Myr, the time since active lunar tectonism under the massive premare bombardment ended. From Baldwin's (1987) tabulation of estimated ages for a representative sample of large lunar craters younger than 3800 Ma, six major cratering episodes can be discerned. These six bombardment episodes, which must have affected the Earth too, appear to match in time the six major episodes of orogenic tectonism on Earth, despite typical resolution errors of +/- 100 Myr and the great uncertainties of the two chronologies. Since more highly resolved events during the Cenozoic and Mesozoic Eras suggest the same correlation, it is possible that large impacts have influenced plate tectonics and other aspects of geologic history, perhaps by triggering flood basalt eruptions.

  7. ON THE NOTION OF WELL-DEFINED TECTONIC REGIMES FOR TERRESTRIAL PLANETS IN THIS SOLAR SYSTEM AND OTHERS

    International Nuclear Information System (INIS)

    Lenardic, A.; Crowley, J. W.

    2012-01-01

    A model of coupled mantle convection and planetary tectonics is used to demonstrate that history dependence can outweigh the effects of a planet's energy content and material parameters in determining its tectonic state. The mantle convection-surface tectonics system allows multiple tectonic modes to exist for equivalent planetary parameter values. The tectonic mode of the system is then determined by its specific geologic and climatic history. This implies that models of tectonics and mantle convection will not be able to uniquely determine the tectonic mode of a terrestrial planet without the addition of historical data. Historical data exists, to variable degrees, for all four terrestrial planets within our solar system. For the Earth, the planet with the largest amount of observational data, debate does still remain regarding the geologic and climatic history of Earth's deep past but constraints are available. For planets in other solar systems, no such constraints exist at present. The existence of multiple tectonic modes, for equivalent parameter values, points to a reason why different groups have reached different conclusions regarding the tectonic state of extrasolar terrestrial planets larger than Earth ( s uper-Earths ) . The region of multiple stable solutions is predicted to widen in parameter space for more energetic mantle convection (as would be expected for larger planets). This means that different groups can find different solutions, all potentially viable and stable, using identical models and identical system parameter values. At a more practical level, the results argue that the question of whether extrasolar terrestrial planets will have plate tectonics is unanswerable and will remain so until the temporal evolution of extrasolar planets can be constrained.

  8. Geochronology and geochemistry of Mesozoic intrusive rocks in the Xing'an Massif of NE China: Implications for the evolution and spatial extent of the Mongol-Okhotsk tectonic regime

    Science.gov (United States)

    Li, Yu; Xu, Wen-Liang; Tang, Jie; Pei, Fu-Ping; Wang, Feng; Sun, Chen-Yang

    2018-04-01

    This study presents new zircon U-Pb-Hf and whole-rock geochemical data for intrusive rocks in the Xing'an Massif of NE China, with the aim of furthering our understanding of the evolution and spatial influence of the Mongol-Okhotsk tectonic regime. Zircon U-Pb dating indicates that five stages of Mesozoic magmatism are recorded in the Xing'an Massif, namely during the Middle Triassic ( 237 Ma), the Late Triassic ( 225 Ma), the Early Jurassic ( 178 Ma), the Middle Jurassic ( 168 Ma), and the late Early Cretaceous ( 130 Ma). The Middle Triassic-Early Jurassic intrusive rocks in the Xing'an Massif are dominantly granodiorites, monzogranites, and syenogranites that formed from magma generated by partial melting of newly accreted continental crust. Geochemistry of the Middle Triassic-Early Jurassic granitoid suites of the Xing'an Massif indicates their formation at an active continental margin setting, related to the southwards subduction of the Mongol-Okhotsk oceanic plate. The Middle Jurassic monzogranites in the Xing'an Massif are geochemically similar to adakites and have εHf(t) values (+3.8 to +5.8) and Hf two-stage model ages (TDM2; 979-850 Ma) that are indicative of derivation from magma generated by partial melting of thickened juvenile lower crust. The Middle Jurassic monzogranites formed in a compressional setting related to the closure of the Mongol-Okhotsk Ocean. The late Early Cretaceous intrusive rocks in the Xing'an Massif are dominated by A-type granitoids that are associated with bimodal volcanic rocks, suggesting their formation in an extensional environment related to either (i) delamination of a previously thickened region of the crust, associated with the Mongol-Okhotsk tectonic regime; (ii) the subduction of the Paleo-Pacific Plate; or (iii) the combined influence of these two tectonic regimes.

  9. Slow slip hidden in the noise: the intermittence of tectonic release

    Science.gov (United States)

    Frank, W.

    2016-12-01

    Referred to as slow slip events, the transient aseismic slip that occurs along plate boundaries can be indirectly characterized through colocated seismicity, such as tectonic tremor and low-frequency earthquakes (LFEs). Using the timing of cataloged LFE and tremor activity in Guerrero, Mexico and northern Cascadia, I decompose the inter-aseismic GPS displacement, defined as the surface deformation between previously detected slow slip events, into separate regimes of tectonic loading and release. In such a way, previously undetected slow slip events that produce on average less than a millimeter of surface deformation are extracted from the geodetic noise. These new observations demonstrate that the inter-aseismic period is not quiescent and that slow slip occurs much more often than previously thought. This suggests that the plate interface where slow slip and tremor occur is in fact strongly coupled and undergoes rapid cycles of stress accumulation and release.

  10. Syn-kinematic palaeogeographic evolution of the West European Platform: correlation with Alpine plate collision and foreland deformation

    NARCIS (Netherlands)

    Sissingh, W.

    Sequence stratigraphic correlations indicate that intermittent changes of the kinematic far-field stress-field regimes, and the associated geodynamic re-organisations at the plate-tectonic contacts of the African, Apulian, Iberian and European plates, affected the Tertiary palaeogeographic evolution

  11. Mass loss as a driving mechanism of tectonics of Enceladus

    Science.gov (United States)

    Czechowski, Leszek

    2015-04-01

    Summary We suggest that the mass loss from South Polar Terrain (SPT) is the main driving force of the following tectonic processes on Enceladus: subsidence of SPT, flow in the mantle and motion of plates. 1. Introduction Enceladus, a satellite of Saturn, is the smallest celestial body in the Solar System where volcanic activity is observed. Every second, the mass of ~200 kg is ejected into space from the South Polar Terrain (SPT) - [1, 2, 3]. The loss of matter from the body's interior should lead to global compression of the crust. Typical effects of compression are: thrust faults, folding and subduction. However, such forms are not dominant on Enceladus. We propose here special tectonic model that could explain this paradox. 2. Subsidence of SPT and tectonics The volatiles escape from the hot region through the fractures forming plumes in the space. The loss of the volatiles results in a void, an instability, and motion of solid matter into the hot region to fill the void. The motion includes : Subsidence of the 'lithosphere' of SPT. Flow of the matter in the mantle. Motion of plates adjacent to SPT towards the active region. If emerging void is being filled by the subsidence of SPT only, then the velocity of subsidence is ~0.05 mm-yr-1. However, all three types of motion are probably important, so the subsidence is slower but mantle flow and plates' motion also play a role in filling the void. Note that in our model the reduction of the crust area is not a result of compression but it is a result of the plate sinking. Therefore the compressional surface features do not have to be dominant. 3. Models of subsidence The numerical model of suggested process of subsidence is developed. It is based on the typical set of equation: Navier-Stokes equation for incompressible viscous liquid, equation of continuity and equation of heat conduction. The Newtonian and non-Newtonian rheologies are used. The preliminary results of the model indicate that the subsidence rate of

  12. Geomorphological features of active tectonics and ongoing ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 124; Issue 6. Geomorphological features of active tectonics and ... concluded that the region is still tectonically active. The information would be very important in identifying the areas of hazard prone and also planning and designing of the socio-economic projects.

  13. Strain transformation between tectonic extrusion and crustal thickening in the growth of the Tibetan Plateau

    Science.gov (United States)

    Liu, M.; Li, Y.; Sun, Y.; Shen, X.

    2017-12-01

    The Indo-Eurasian continental collision since 50 Ma has thickened the crust to raise the Himalayan-Tibetan Plateau and driven lateral extrusion of Asian lithospheric blocks to affect Cenozoic tectonics in central and east Asia. The relative roles of crustal thickening and tectonic extrusion, and the strain partitioning between them over time and space, remain controversial. We have analyzed the strain rates using GPS velocities, and correlated the results with vertical motion derived from precise leveling. We found that tectonic extrusion largely transforms to crustal thickening near the margins of the Tibetan Plateau. Near the NW margin of the Tibetan Plateau, the shear stain transforms to compressive strain, consistent with neotectonic studies that indicate crustal shortening and uplift. Around the SE margin, shear stain largely terminates in the southern Yunnan province of China. The present-day crustal motion in SE Tibetan Plateau can be well explained by gravitational spreading without invoking plate-edge push as envisioned in the tectonic extrusion model. Using data collected from local seismic arrays, we derived receiver functions to image the lithospheric structures across the Tibetan Plateau and the Alashan block to its north and the Ordos block to its east. Our results indicate that the mantle lithosphere of these bounding Asian blocks has not been reworked by Tibetan tectonics; instead they have acted as restrictive walls to the growing Tibetan Plateau. Our finite element modeling shows that crustal deformation along the margins of the Tibetan Plateau are consistent with the notion that the east- and southeastward extrusion of the Tibetan lithosphere is largely confined to the Tibetan Plateau because of the restrictive bounding blocks of the Asian lithosphere. Thus the tectonic impact of the Indo-Eurasian collision on the Cenozoic Asian tectonics may not be as extensive as previously thought.

  14. Numerical Models of Alaskan Tectonics: A Review and Looking Ahead to a New Era of Research

    Science.gov (United States)

    Jadamec, M. A.; Freymueller, J. T.

    2015-12-01

    The Pacific-North American plate boundary in Alaska is in the current scientific spotlight, as a highlighted tectonic region for integrated scientific investigation. It is timely, therefore, to step back and examine the previous numerical modeling studies of Alaska. Reviewing the numerical models is valuable, as geodynamic modeling can be a predictive tool that can guide and target field studies, both geologic and geophysical. This review presents a comparison of the previous numerical modeling studies of the Alaska-Aleutian subduction zone, including the mainland and extending into northwestern Canada. By distinguishing between the model set-up, governing equations, and underlying assumptions, non-modelers can more easily understand under what context the modeling predictions can be interpreted. Several key features in the Alaska tectonic setting appear in all the models to have a first order effect on the resulting deformation, such as the plate margin geometry and Denali fault. In addition, there are aspects of the tectonic setting that lead to very different results depending how they are implemented into the models. For example, models which fix the slab velocity to surface plate motions predict lower mantle flow rates than models that allow the slab to steepen. Despite the previous modeling studies, many unanswered questions remain, including the formation of the Wrangell volcanics, the driver for motion in western and interior Alaska, and the timing and nature of slab deformation. A synthesis of this kind will be of value to geologists, geodeticists, seismologists, volcanologists, sedimentologists, geochemists, as well as geodynamicists.

  15. Tectonically asymmetric Earth: From net rotation to polarized westward drift of the lithosphere

    Directory of Open Access Journals (Sweden)

    Carlo Doglioni

    2015-05-01

    Full Text Available The possibility of a net rotation of the lithosphere with respect to the mantle is generally overlooked since it depends on the adopted mantle reference frames, which are arbitrary. We review the geological and geophysical signatures of plate boundaries, and show that they are markedly asymmetric worldwide. Then we compare available reference frames of plate motions relative to the mantle and discuss which is at best able to fit global tectonic data. Different assumptions about the depths of hotspot sources (below or within the asthenosphere, which decouples the lithosphere from the deep mantle predict different rates of net rotation of the lithosphere relative to the mantle. The widely used no-net-rotation (NNR reference frame, and low (1°/Ma net rotation (shallow hotspots source, all plates, albeit at different velocity, move westerly along a curved trajectory, with a tectonic equator tilted about 30° relative to the geographic equator. This is consistent with the observed global tectonic asymmetries.

  16. Growth of a tectonic ridge

    Energy Technology Data Exchange (ETDEWEB)

    Fleming, R.W.; Messerich, J.A. [Geological Survey, Denver, CO (United States); Johnson, A.M. [Purdue Univ., West Lafayette, IN (United States). Dept. of Earth and Atmospheric Sciences

    1997-12-31

    The 28 June 1992 Landers, California, earthquake of M 7.6 created an impressive record of surface rupture and ground deformation. Fractures extend over a length of more than 80 km including zones of right-lateral shift, steps in the fault zones, fault intersections and vertical changes. Among the vertical changes was the growth of a tectonic ridge described here. In this paper the authors describe the Emerson fault zone and the Tortoise Hill ridge including the relations between the fault zone and the ridge. They present data on the horizontal deformation at several scales associated with activity within the ridge and belt of shear zones and show the differential vertical uplifts. And, they conclude with a discussion of potential models for the observed deformation.

  17. The Ecology of Urban Tectonics

    DEFF Research Database (Denmark)

    Beim, Anne; Hvejsel, Marie Frier

    2016-01-01

    unfairly neglected when accounting for the great modern heroes of Danish architecture. Just recently, examples of his work have been thoroughly presented in the Danish architectural magazine; ‘Arkitekten’. (Keiding 2013) This paper analyses two works of Hansen: Bremerholm Transformer Station and Bellahøj......’. In this way Hansen’s work sets an example in itself as built heritage, but in addition, they set a methodological example when valued in relation to Frampton’s notion of the arrière-garde. Hansen’s work witnesses a critical and reflective ability on his behalf that enables him to act in everyday practice....... In concluding, it is our finding, that it is exactly here that research into the field of tectonics holds it potential. NOT as “optimization of advanced technology” and visual occupation with structural elements as such and NOT as “the ever-present tendency to regress into nostalgic historicism or the glibly...

  18. Create Your Plate

    Medline Plus

    Full Text Available ... Student Resources History of Diabetes Resources for School Projects How to Reference Our Site Diabetes Basics Myths ... Your Plate It's simple and effective for both managing diabetes and losing weight. Creating your plate lets ...

  19. Create Your Plate

    Medline Plus

    Full Text Available ... Planning Meals Diabetes Meal Plans Create Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook ... Create Your Plate Meal Planning for Vegetarian Diets Gluten Free Diets Holiday Meal Planning Cook with Heart- ...

  20. Create Your Plate

    Medline Plus

    Full Text Available ... Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook with Heart-Healthy Foods Holiday Meal ... Healthy Diet Create Your Plate Meal Planning for Vegetarian Diets Gluten Free Diets Holiday Meal Planning Cook ...

  1. Create Your Plate

    Medline Plus

    Full Text Available ... Your Plate It's simple and effective for both managing diabetes and losing weight. Creating your plate lets you still choose the foods you want, but changes the portion sizes so you are getting larger ...

  2. Williamson Polishing & Plating Site

    Science.gov (United States)

    Williamson Polishing & Plating Co. Inc. was a plating shop located in the Martindale-Brightwood neighborhood of Indianapolis. The facility conducted job shop polishing and electroplating services. The vacant site contains a 14,651-square-foot building.

  3. The Cretaceous and Cenozoic tectonic evolution of Southeast Asia

    Science.gov (United States)

    Zahirovic, S.; Seton, M.; Müller, R. D.

    2014-04-01

    Tectonic reconstructions of Southeast Asia have given rise to numerous controversies that include the accretionary history of Sundaland and the enigmatic tectonic origin of the proto-South China Sea. We assimilate a diversity of geological and geophysical observations into a new regional plate model, coupled to a global model, to address these debates. Our approach takes into account terrane suturing and accretion histories, the location of subducted slabs imaged in mantle tomography in order to constrain the evolution of regional subduction zones, as well as plausible absolute and relative plate velocities and tectonic driving mechanisms. We propose a scenario of rifting from northern Gondwana in the latest Jurassic, driven by northward slab pull from north-dipping subduction of Tethyan crust beneath Eurasia, to detach East Java, Mangkalihat, southeast Borneo and West Sulawesi blocks that collided with a Tethyan intra-oceanic subduction zone in the mid-Cretaceous and subsequently accreted to the Sunda margin (i.e., southwest Borneo core) in the Late Cretaceous. In accounting for the evolution of plate boundaries, we propose that the Philippine Sea plate originated on the periphery of Tethyan crust forming this northward conveyor. We implement a revised model for the Tethyan intra-oceanic subduction zones to reconcile convergence rates, changes in volcanism and the obduction of ophiolites. In our model the northward margin of Greater India collides with the Kohistan-Ladakh intra-oceanic arc at ∼53 Ma, followed by continent-continent collision closing the Shyok and Indus-Tsangpo suture zones between ∼42 and 34 Ma. We also account for the back-arc opening of the proto-South China Sea from ∼65 Ma, consistent with extension along east Asia and the formation of supra-subduction zone ophiolites presently found on the island of Mindoro. The related rifting likely detached the Semitau continental fragment from South China, which accreted to northern Borneo in the mid

  4. Vibration of plates

    CERN Document Server

    Chakraverty, Snehashish

    2008-01-01

    Plates are integral parts of most engineering structures and their vibration analysis is required for safe design. This work provides a comprehensive introduction to vibration theory and analysis of two-dimensional plates. It offers information on vibration problems along with a discussion of various plate geometries and boundary conditions.

  5. The quasi-rigid premise in Precambrian tectonics

    Science.gov (United States)

    Piper, J. D. A.

    1991-12-01

    A simple test of the proposition that movements between multiple continental fragments driven by plate tectonics took place during the earlier eons of geological time is presented. A random distribution is derived when the collective palaeomagnetic poles are rotated into any quasi-rigid reconstruction. The test surmounts the most serious limitation of Precambrian palaeomagnetic data, namely, that the ages of magnetization are mostly poorly known. Confirmation of the quasi-rigid premise is derived in a debased form, but is not suppressed, by the deficiencies of the database. This palaeomagnetic constraint explains the distinctive isotopic, geochemical, and lithofacies signatures of the Proterozoid eon and is independently supported by the trend and long temporal continuity of crustal lineaments.

  6. Metallogenic relationships to tectonic evolution - the Lachlan Orogen, Australia

    Science.gov (United States)

    Bierlein, Frank P.; Gray, David R.; Foster, David A.

    2002-08-01

    Placing ore formation within the overall tectonic framework of an evolving orogenic system provides important constraints for the development of plate tectonic models. Distinct metallogenic associations across the Palaeozoic Lachlan Orogen in SE Australia are interpreted to be the manifestation of interactions between several microplates and three accretionary complexes in an oceanic back-arc setting. In the Ordovician, significant orogenic gold deposits formed within a developing accretionary wedge along the Pacific margin of Gondwana. At the same time, major porphyry Cu-Au systems formed in an oceanic island arc outboard of an evolved magmatic arc that, in turn, gave rise to granite-related Sn-W deposits in the Early Silurian. During the ongoing evolution of the orogen in the Late Silurian to Early Devonian, sediment-hosted Cu-Au and Pb-Zn deposits formed in short-lived intra-arc basins, whereas a developing fore-arc system provided the conditions for the formation of several volcanogenic massive sulphide deposits. Inversion of these basins and accretion to the Australian continental margin triggered another pulse of orogenic gold mineralisation during the final consolidation of the orogenic belt in the Middle to Late Devonian.

  7. Relative tectonic activity classification in Kermanshah area, west Iran

    Science.gov (United States)

    Arian, M.; Aram, Z.

    2014-07-01

    The High Zagros region because of closing to subduction zone and the collision of the Arabian and Eurasian plates is imposed under the most tectonic variations. In this research, Gharasu river basin that it has located in Kermanshah area was selected as the study area and 6 geomorphic indices were calculated and the results of each ones were divided in 3 classes. Then, using the indices, relative tectonic activity was calculated and the values were classified and analyzed in 4 groups. Regions were identified as very high, high, moderate and low. In analyzing the results and combining them with field observation and regional geology the results are often associated and justified with field evidences. The highest value is located on Dokeral anticline in crush zone in Zagros Most of the areas with high and moderate values of lat are located on crush zone in Zagros too. Crushing of this zone is because of main faults mechanism of Zagros region. The result of this paper confirms previous researches in this region. At the end of the eastern part of the study area, the value of Iat is high that could be the result of Sarab and Koh-e Sefid faults mechanism.

  8. Understanding plate-motion changes over the past 100 Myr with quantitative models of the coupled lithosphere/mantle system

    Science.gov (United States)

    Stotz, Ingo; Iaffaldano, Giampiero; Rhodri Davies, D.

    2015-04-01

    impact of the mantle time-evolving buoyancy-field on lithospheric plate-motions; and (ii) explore the dynamics of lithosphere/mantle interactions by using the geological record as constraint, focusing on regions featuring cratonic lithosphere, dynamic topography or high topographic features. This progress allows us to self-consistently simulate any tectonic scenario from the late Cretaceous -- through the Cenozoic -- to the present-day. Our work will aid with better understanding the processes that govern the coupled lithosphere/mantle system.

  9. Towards a tectonic sustainable building practice

    DEFF Research Database (Denmark)

    Beim, Anne

    2010-01-01

    and environmental problems? The objective of the project is to analyse and develop the tectonic practice based on case studies, in relation to: • Cultural anchoring and identity creation • Building culture and creative processes • Sustainability, lifecycle and resource management The research project is divided...... into a main project and various subprojects, respectively, two levels that mutually feed each other.The main project, which constitutes the general level, seeks to identify a coherent strategy towards a new tectonically sustainable building culture.The subprojects look at partial issues and go into specific...... questions dealing with central aspects of the overall project: tectonics, identity creation, cultural heritage/recycling and sustainability....

  10. New aero-gravity results from the Arctic: Linking the latest Cretaceous-early Cenozoic plate kinematics of the North Atlantic and Arctic Ocean

    DEFF Research Database (Denmark)

    Døssing, Arne; Hopper, J.R.; Olesen, Arne Vestergaard

    2013-01-01

    The tectonic history of the Arctic Ocean remains poorly resolved and highly controversial. Details regarding break up of the Lomonosov Ridge from the Barents-Kara shelf margins and the establishment of seafloor spreading in the Cenozoic Eurasia Basin are unresolved. Significantly, the plate...... tectonic evolution of the Mesozoic Amerasia Basin is essentially unknown. The Arctic Ocean north of Greenland is at a critical juncture that formed at the locus of a Mesozoic three-plate setting between the Lomonosov Ridge, Greenland, and North America. In addition, the area is close to the European plate...... plateau against an important fault zone north of Greenland. Our results provide new constraints for Cretaceous-Cenozoic plate reconstructions of the Arctic. Key Points Presentation of the largest aero-gravity survey acquired over the Arctic Ocean Plate tectonic link between Atlantic and Arctic spreading...

  11. Earthquake recurrence and magnitude and seismic deformation of the northwestern Okhotsk plate, northeast Russia

    Science.gov (United States)

    Hindle, D.; Mackey, K.

    2011-02-01

    Recorded seismicity from the northwestern Okhotsk plate, northeast Asia, is currently insufficient to account for the predicted slip rates along its boundaries due to plate tectonics. However, the magnitude-frequency relationship for earthquakes from the region suggests that larger earthquakes are possible in the future and that events of ˜Mw 7.5 which should occur every ˜100-350 years would account for almost all the slip of the plate along its boundaries due to Eurasia-North America convergence. We use models for seismic slip distribution along the bounding faults of Okhotsk to conclude that relatively little aseismic strain release is occurring and that larger future earthquakes are likely in the region. Our models broadly support the idea of a single Okhotsk plate, with the large majority of tectonic strain released along its boundaries.

  12. Source-to-sink constraints on tectonic and sedimentary evolution of the western Central Range and Cenderawasih Bay (Indonesia)

    Science.gov (United States)

    Babault, Julien; Viaplana-Muzas, Marc; Legrand, Xavier; Van Den Driessche, Jean; González-Quijano, Manuel; Mudd, Simon M.

    2018-05-01

    The island of New Guinea is the result of continent-arc collision that began building the island's Central Range during the late Miocene. Recent studies have shown that rapid subduction, uplift and exhumation events took place in response to rapid, oblique convergence between the Pacific and the Australian plates. The tectonic and sedimentary evolution of Cenderawasih Bay, in the northwestern part of the New Guinea Island is still poorly understood: this bay links a major structural block, the Kepala Burung block, to the island's Central Ranges. Previous studies have shown that Cenderawasih Bay contains a thick (>8 km) sequence of undated sediments. One hypothesis claims that the embayment resulted from a 3 Ma opening created by anticlockwise rotation of the Kepala Burung block with respect to the northern rim of the Australian plate. Alternatively, the current configuration of Cenderawasih Bay could have resulted from the southwest drift of a slice of volcanics and oceanic crust between 8 and 6 Ma. We test these hypotheses using (i) a geomorphologic analysis of the drainage network dynamics, (ii) a reassessment of available thermochronological data, and (iii) seismic lines interpretation. We suggest that sediments started to accumulate in Cenderawasih Bay and onshore in the Waipoga Basin in the late Miocene since the inception of growth of the Central Range, beginning at 12 Ma, resulting in sediment accumulation of up to 12,200 m. This evidence is more consistent with the second hypothesis, and the volume of sediment accumulated means it is unlikely that the embayment was the result of recent (2-3 Ma) rotation of structural blocks. At first order, we predict that infilling is mainly composed of siliciclastics sourced in the graphite-bearing Ruffaer Metamorphic Belt and its equivalent in the Weyland Overthrust. Ophiolites, volcanic arc rocks and diorites contribute minor proportions. From the unroofing paths in the Central Range we deduce two rates of solid phase

  13. Paleomagnetism and Tectonic Evolution of Mexico: Precambrian to Recent

    Science.gov (United States)

    Fucugauchi, J. U.

    2007-05-01

    It is 20yr since publication of the last synthesis of country-wide paleomagnetic data and almost 30yr of first attempt to construct an apparent polar wander path for Mexico. During this time, data has increased ten-fold and a new synthesis may appear long overdue. Mexico constitutes the southern portion of the North American plate, and tectonic models long suggested a complex evolution involving ocean-basin closure, continental collision/break-up, terrane accretion, large-scale motions, orogenic deformation, oceanic plate reorganizations and oceanic basin development. Paleoreconstructions of Atlantic-bordering continents show major overlap of northern South America onto Mexico, highlighting the geometric problem, allocthonous nature and opening room for a diversity of models. Paleomagnetism appears well-suited to tackle these problems, and data had early been used to evaluate tectonic models. Likewise, the larger database is now used to assess models and develop alternatives. This task is greatly aided by new available geochronological, geophysical and geological data. Our new synthesis still shows data gaps, with Paleozoic and Precambrian units poorly represented. Paleomagnetic data and tectonic models require complex large-scale motions of Precambrian and Paleozoic blocks, solutions for opening of Gulf of Mexico and Caribbean Sea, and post-Triassic-Jurassic amalgamation of Mexico and Central America. The southern edge of the North American craton is positioned in northern Mexico, marking the limit for accreted terranes to the south. Possible southern extension of Marathon-Ouachita Paleozoic belt, obscured or truncated when it comes into Mexico, remains unstudied paleomagnetically. Left-lateral motions along faults related to opening of Gulf of Mexico are not supported by paleomagnetism. The Western Cordilleran belt appears laterally displaced in southern US and into Mexico, where the paleomagnetic signature of northward latitudinal translations and clockwise

  14. The Tectonic Potentials of Concrete

    DEFF Research Database (Denmark)

    Egholm Pedersen, Ole

    2013-01-01

    Contemporary techniques for concrete casting in an architectural context are challenged by demands of increased individualization in our built environment, reductions in the use of resources and waste generation. In recent years, new production technologies and strategies that break with the indu......Contemporary techniques for concrete casting in an architectural context are challenged by demands of increased individualization in our built environment, reductions in the use of resources and waste generation. In recent years, new production technologies and strategies that break...... with the industrial paradigm of standardization, have been put forward. This development is carried forward by computers and digital fabrication, but has yet to find its way into the production of building components. With regards to concrete casting, however, existing research do offer advancement towards...... an increased customisation of casting moulds. The hypothesis of this research is that the techniques used in this research do not fully address the tectonic potentials of concrete which gives rise to the primary research question: Is it possible to enhance existing or develop new concrete casting techniques...

  15. Tectonics earthquake distribution pattern analysis based focal mechanisms (Case study Sulawesi Island, 1993–2012)

    International Nuclear Information System (INIS)

    Ismullah M, Muh. Fawzy; Lantu,; Aswad, Sabrianto; Massinai, Muh. Altin

    2015-01-01

    Indonesia is the meeting zone between three world main plates: Eurasian Plate, Pacific Plate, and Indo – Australia Plate. Therefore, Indonesia has a high seismicity degree. Sulawesi is one of whose high seismicity level. The earthquake centre lies in fault zone so the earthquake data gives tectonic visualization in a certain place. This research purpose is to identify Sulawesi tectonic model by using earthquake data from 1993 to 2012. Data used in this research is the earthquake data which consist of: the origin time, the epicenter coordinate, the depth, the magnitude and the fault parameter (strike, dip and slip). The result of research shows that there are a lot of active structures as a reason of the earthquake in Sulawesi. The active structures are Walannae Fault, Lawanopo Fault, Matano Fault, Palu – Koro Fault, Batui Fault and Moluccas Sea Double Subduction. The focal mechanism also shows that Walannae Fault, Batui Fault and Moluccas Sea Double Subduction are kind of reverse fault. While Lawanopo Fault, Matano Fault and Palu – Koro Fault are kind of strike slip fault

  16. Tectonics earthquake distribution pattern analysis based focal mechanisms (Case study Sulawesi Island, 1993–2012)

    Energy Technology Data Exchange (ETDEWEB)

    Ismullah M, Muh. Fawzy, E-mail: mallaniung@gmail.com [Master Program Geophysical Engineering, Faculty of Mining and Petroleum Engineering (FTTM), Bandung Institute of Technology (ITB), Jl. Ganesha no. 10, Bandung, 40116, Jawa Barat (Indonesia); Lantu,; Aswad, Sabrianto; Massinai, Muh. Altin [Geophysics Program Study, Faculty of Mathematics and Natural Sciences, Hasanuddin University (UNHAS), Jl. PerintisKemerdekaan Km. 10, Makassar, 90245, Sulawesi Selatan (Indonesia)

    2015-04-24

    Indonesia is the meeting zone between three world main plates: Eurasian Plate, Pacific Plate, and Indo – Australia Plate. Therefore, Indonesia has a high seismicity degree. Sulawesi is one of whose high seismicity level. The earthquake centre lies in fault zone so the earthquake data gives tectonic visualization in a certain place. This research purpose is to identify Sulawesi tectonic model by using earthquake data from 1993 to 2012. Data used in this research is the earthquake data which consist of: the origin time, the epicenter coordinate, the depth, the magnitude and the fault parameter (strike, dip and slip). The result of research shows that there are a lot of active structures as a reason of the earthquake in Sulawesi. The active structures are Walannae Fault, Lawanopo Fault, Matano Fault, Palu – Koro Fault, Batui Fault and Moluccas Sea Double Subduction. The focal mechanism also shows that Walannae Fault, Batui Fault and Moluccas Sea Double Subduction are kind of reverse fault. While Lawanopo Fault, Matano Fault and Palu – Koro Fault are kind of strike slip fault.

  17. Recent deeper geophysical results better account for the tectonics in the Italian area

    Directory of Open Access Journals (Sweden)

    C. Morelli

    1997-06-01

    Full Text Available Results from extended DSS profiles (1956-1986 in Italy and surrounding land and sea areas offer good constraints for other geophysical and geological data. Integrated interpretations outline the main tectonic features. Collisional tectonics is predominant in the Alps, for which the Adriatic plate acted as hinterland against the European plate foreland. Main results: W-wards, NW- and N-wards oriented overthrusting on the European crust, bending of the lower European crust, European Moho to 70 km depth with the Adriatic mantle indented above, crustal doubling (Adriatic over the European one. In the Apennines, on the contrary, the Adriatic plate acted as a foreland, against the overthrusts generated by the Tuscanian and Tyrrhenian mantellic bodies, heated, elevated and migrated NE-wards and SE-wards, respectively. Also the Adriatic plate bends under this load-centripetally towards the Tyrrhenian sea, so that the Adriatic Moho from 35 km depth is presumed to descend through a flexure till 40-50 km below the Tuscanian and Tyrrhenian land areas. The external peri-Apenninic area is still in compression and includes thick sedimentary basins, from the Po-plain to Sicily. The internal area is in extension, overlapped by thin, stretched crusts of Ligurian and Tyrrhenian origin, whose remnants occupy most of both seas areas, with two areas of oceanic crust in the SE-Tyrrhenian. Rifting and opening is in action also in the Ligurian Sea and Sicily Strait.

  18. Tectonic vocabulary and materialization: Discourse on the future of tectonic architectural research in the Nordic countries

    DEFF Research Database (Denmark)

    Beim, Anne; Bundgaard, Charlotte; Hvejsel, Marie Frier

    2015-01-01

    By referring to the fundamental question of how we unite aesthetics and technology – tectonic theory is necessarily a focal point in the development of the architectural discipline. However, a critical reconsideration of the role of tectonic theory seems necessary when facing the present everyday...... to establish a Nordic Network for Research and Teaching in Tectonics is currently forming. This paper seeks to jointly reflect upon these initiatives in order to bring them further, with the intention to clad a discourse on the future of tectonic architectural research that addresses the conditions of everyday...

  19. Radon emanation in tectonically active areas

    International Nuclear Information System (INIS)

    King, C.Y.

    1980-01-01

    Subsurface radon emanation has been continuously monitored for up to three years by the Track Etch method in shallow dry holes at more than 60 sites along several tectonic faults in central California and at 9 sites near the Kilauea volcano in Hawaii. The measured emanation in these tectonically active areas shows large long-term variations that may be related mainly to crustal strain changes

  20. TECTONIC ZONING OF THE SEDIMENTARY COVER IN THE DERYUGIN BASIN OF THE SEA OF OKHOTSK BASED ON STRUCTURAL-MATERIAL (LITHOPHYSICAL INDICATORS

    Directory of Open Access Journals (Sweden)

    V. P. Semakin

    2013-01-01

    Full Text Available In terms of tectonics, the Deryugin basin (Fig. 1 is a part of the epi-Mesozoic Okhotsk plate comprising the heterogeneous basement that is mainly pre-Cenozoic (the lower structural stage and the sedimentary cover that is mainly represented by the Paleogenic-Neogenic-Quaternary deposits with the Upper Cretaceous sedimentary rocks observed locally without a visible hiatus (the upper structural stage.The acoustic basement (AB is composed of the metamorphosed Upper Cretaceous-Paleogenic silty-clayey-siliceous deposits (the western part of the region, amphibolites, gneisses, crystalline schists, weakly metamorphosed sandstones, siltstones, and mudstones (often siliceous, as well as intrusive and effusive rocks of basic, intermediate, and rarely persilic composition (the eastern part of the region. AB is generally dated as Mesozoic–Paleozoic.Results of tectonic zoning of the sedimentary cover based on material (lithophysical indicators (Fig. 2 are represented in the format of maps showing lithophysical complexes (LC within the limits of four regional seismo-stratigraphic complexes/structural layers (RSSC I-IV corresponding to the following time intervals: the pre-Oligocene К2–P1-2 (RSSC I, the Oligocene – Lower Miocene P3–N11 (RSSC II, the Lower – Mid Miocene N11–2 (RSSC III, and the Upper Miocene – Pliocene N13–N2 (RSSC IV. Diverse lithological-facies associations composing the RSSCs are grouped into the following lithophysical complexes (LC: 1 - coal-bearing silty-clayey-sandy terrigenous, 2 - sandy-silty-clayey terrigenous, 3 - silty-clayey-siliceous, and 4 - sandy-silty-clayey volcanic [Sergeyev, 2006]. In the studied area (Fig. 2, the deposits of the pre-Oligocene RSSC are identified in limited areas within its northern, northwestern, and southwestern parts; they are represented by coal-bearing silty-clayey-sandy terrigenous and silty-clayey-siliceous LCs. Other RSSCs (II, III, and IV in this area represented mostly by sandy

  1. State-of-the-art for evaluating the potential impact of tectonism and volcanism on a radioactive waste repository

    Energy Technology Data Exchange (ETDEWEB)

    1980-07-16

    Most estimates of the time required for safe isolation of radioactive wastes from the biosphere range from 100,000 to 1,000,000 years. For such long time spans, it is necessary to assess the potential effects of geologic processes such as volcanism and tectonic activity on the integrity of geologic repositories. Predictions of geologic phenomena can be based on probabilistic models, which assume a random distribution of events. The necessary historic and geologic records are rarely available to provide an adequate data base for such predictions. The observed distribution of volcanic and tectonic activity is not random, and appears to be controlled by extremely complex deterministic processes. The advent of global plate tectonic theory in the past two decades has been a giant step toward understanding these processes. At each potential repository site, volcanic and tectonic processes should be evaluated to provide the most thorough possible understanding of those deterministic processes. Based on this knowledge, judgements will have to be made as to whether or not the volcanic and tectonic processes pose unacceptable risk to the integrity of the repository. This report describes the potential hazards associated with volcanism and tectonism, and the means for evaluating these processes.

  2. State-of-the-art for evaluating the potential impact of tectonism and volcanism on a radioactive waste repository

    International Nuclear Information System (INIS)

    1980-01-01

    Most estimates of the time required for safe isolation of radioactive wastes from the biosphere range from 100,000 to 1,000,000 years. For such long time spans, it is necessary to assess the potential effects of geologic processes such as volcanism and tectonic activity on the integrity of geologic repositories. Predictions of geologic phenomena can be based on probabilistic models, which assume a random distribution of events. The necessary historic and geologic records are rarely available to provide an adequate data base for such predictions. The observed distribution of volcanic and tectonic activity is not random, and appears to be controlled by extremely complex deterministic processes. The advent of global plate tectonic theory in the past two decades has been a giant step toward understanding these processes. At each potential repository site, volcanic and tectonic processes should be evaluated to provide the most thorough possible understanding of those deterministic processes. Based on this knowledge, judgements will have to be made as to whether or not the volcanic and tectonic processes pose unacceptable risk to the integrity of the repository. This report describes the potential hazards associated with volcanism and tectonism, and the means for evaluating these processes

  3. Interaction between subducting plates: results from numerical and analogue modeling

    Science.gov (United States)

    Kiraly, Agnes; Capitanio, Fabio A.; Funiciello, Francesca; Faccenna, Claudio

    2016-04-01

    The tectonic setting of the Alpine-Mediterranean area is achieved during the late Cenozoic subduction, collision and suturing of several oceanic fragments and continental blocks. In this stage, processes such as interactions among subducting slabs, slab migrations and related mantle flow played a relevant role on the resulting tectonics. Here, we use numerical models to first address the mantle flow characteristic in 3D. During the subduction of a single plate the strength of the return flow strongly depends on the slab pull force, that is on the plate's buoyancy, however the physical properties of the slab, such as density, viscosity or width, do not affect largely the morphology of the toroidal cell. Instead, dramatic effects on the geometry and the dynamics of the toroidal cell result in models where the thickness of the mantle is varied. The vertical component of the vorticity vector is used to define the characteristic size of the toroidal cell, which is ~1.2-1.3 times the mantle depth. This latter defines the range of viscous stress propagation through the mantle and consequent interactions with other slabs. We thus further investigate on this setup where two separate lithospheric plates subduct in opposite sense, developing opposite polarities and convergent slab retreat, and model different initial sideways distance between the plates. The stress profiles in time illustrate that the plates interacts when slabs are at the characteristic distance and the two slabs toroidal cells merge. Increased stress and delayed slab migrations are the results. Analogue models of double-sided subduction show similar maximum distance and allow testing the additional role of stress propagated through the plates. We use a silicon plate subducting on its two opposite margins, which is either homogeneous or comprises oceanic and continental lithospheres, differing in buoyancy. The modeling results show that the double-sided subduction is strongly affected by changes in plate

  4. The revised tectonic history of Tharsis

    Science.gov (United States)

    Bouley, Sylvain; Baratoux, David; Paulien, Nicolas; Missenard, Yves; Saint-Bézar, Bertrand

    2018-04-01

    Constraining the timing of the emplacement of the volcano-tectonic province of Tharsis is critical to understanding the evolution of mantle, surface environment and climate of Mars. The growth of Tharsis had exerted stresses on the lithosphere, which were responsible for tectonic deformation, previously mapped as radial or concentric faults. Insights into the emplacement history of Tharsis may be gained from an analysis of the characteristics and ages of these tectonic features. The number, total length, linear density of extensional or compressional faults in the Tharsis region and deformation rates are reported for each of the following 6 stages: Early and Middle Noachian (stage 1); Late Noachian (stage 2); Early Hesperian (stage 3); Late Hesperian (stage 4), Early Amazonian (stage 5) and Middle Amazonian to Late Amazonian (stage 6). 8571 Tharsis-related tectonic features (radial or concentric to the center of Tharsis) were assigned to one of these periods of time based on their relationship with stratigraphic units defined in the most recent geological map. Intense faulting at Tempe Terra, Claritas and Coracis Fossae and Thaumasia Planum confirms that tectonic deformation started during the Noachian. However, we report a peak in both compressive and extensive rates of deformation during the Early Hesperian whereas the quantitative indicators for compressional and extensional tectonics vary within less than one order of magnitude from the Late Noachian to the Late Hesperian. These observations indicate a protracted growth of Tharsis during the first quarter of Mars evolution and declining from 3 Gyrs ago.

  5. Interdisciplinary approach to exploit the tectonic memory in the continental crust of collisional belts.

    Science.gov (United States)

    Gosso, G.; Marotta, A. M.; Rebay, G.; Regorda, A.; Roda, M.; Spalla, M. I.; Zanoni, D.; Zucali, M.

    2015-12-01

    Collisional belts result by thoroughly competing thermo-mechanical disaggregation and coupling within both continental and oceanic lithospheric slices, during construction of tectono-metamorphic architectures. In multiply reworked metamorphics, tectonic units may be contoured nowadays on the base of coherent thermo-baric and structural time-sequences rather than simply relying on lithologic affinities. Sequences of equilibrium assemblages and related fabric imprints are an approach that appears as a more reliable procedure, that enables to define tectonic units as the volume of crustal slices that underwent corresponding variations during the dynamics of an active margin and takes into account a history of physical imprints. The dimensions of these tectonic units may have varied over time and must be reconstructed combining the tracers of structural and metamorphic changes of basement rocks, since such kind of tectono-metamorphic units (TMUs) is a realistic configuration of the discrete portions of orogenic crust that experienced a coherent sequence of metamorphic and textural variations. Their translational trajectories, and bulk shape changes during deformation, cannot simply be derived from the analysis of the geometries and kinematics of tectonic units, but are to be obtained by adding the reconstruction of quantitative P-T-d-t paths making full use of fossil mineral equilibria. The joint TMU field-and-laboratory definition is an investigation procedure that bears a distinct thermo-tectonic connotation, that, through modelling, offers the opportunity to test the physical compatibilities of plate-scale interconnected variables, such as density, viscosity, and heat transfer, with respect to what current interpretative geologic histories may imply. Comparison between predictions from numerical modelling and natural data obtained by this analytical approach can help to solve ambiguities on geodynamic significance of structural and thermal signatures, also as a

  6. Interactions between tectonics, silicate weathering, and climate explored with carbon cycle modeling

    Science.gov (United States)

    Penman, D. E.; Caves Rugenstein, J. K.; Ibarra, D. E.; Winnick, M.

    2017-12-01

    Earth's long-term carbon cycle is thought to benefit from a stabilizing negative feedback in the form of CO2 consumption by the chemical weathering of silicate minerals: during periods of elevated atmospheric pCO2, chemical weathering rates increase, thus consuming more atmospheric CO2 and cooling global climate, whereas during periods of low pCO2, weathering rates decrease, allowing buildup of CO2 in the atmosphere and warming. At equilibrium, CO2 consumption by silicate weathering balances volcanic CO2 degassing at a specific atmospheric pCO2 dictated by the relationship between total silicate weathering rate and pCO2: Earth's "weathering curve." We use numerical carbon cycle modeling to demonstrate that the shape and slope of the weathering curve is crucial to understanding proposed tectonic controls on pCO2 and climate. First, the shape of the weathering curve dictates the equilibrium response of the carbon cycle to changes in the rate of background volcanic/solid Earth CO2 degassing, which has been suggested to vary significantly with plate tectonic reorganizations over geologic timescales. Second, we demonstrate that if tectonic events can significantly change the weathering curve, this can act as an effective driver of pCO2 and climate on tectonic timescales by changing the atmospheric pCO2 at which silicate weathering balances a constant volcanic/solid Earth degassing rate. Finally, we review the complex interplay of environmental factors that affect modern weathering rates in the field and highlight how the resulting uncertainty surrounding the shape of Earth's weathering curve significantly hampers our ability to quantitatively predict the response of pCO2 and climate to tectonic forcing, and thus represents a substantial knowledge gap in Earth science. We conclude with strategies for closing this knowledge gap by using precise paleoclimatic reconstructions of intervals with known tectonic forcings.

  7. The Contributions of Leonid M. Parfenov to the Tectonics of Eastern Russia

    Science.gov (United States)

    Prokopiev, A. V.; Fujita, K.; Stone, D. B.

    2004-12-01

    Leonid M. Parfenov (1937-2002) was the leading force behind theinterpretation of northeast Russia in the context of plate tectonics. Originally interested in Precambrian geology, he conducted his early field work in southern Siberia in the 1960s. He was exposed to plate tectonics at Liverpool University in 1970 and published the first mobilistic reconstructions of the Precambrian in Russia in 1973. Starting in 1971, he began to systematically conduct field work and accumulate geologic data on what is now considered the accretionary collage of northeast Russia. With colleague Boris A. Natal'in, he published a series of papers on the tectonic evolution of eastern Russia starting in 1977, with a doctoral dissertation on "Comparative Tectonics and Evolution History of Mesozoides of Northeast Asia" in 1983. His work became known in the west with his publication in 1978 in the Journal of Physics of the Earth on "Geodynamics of the North-Eastern Asia in the Mesozoic and Cenozoic Time and the Nature of Volcanic Belt" in which the volcanic belts of eastern Russia were interpreted in the context of subduction zones. From the mid-1980s to his death, he concentrated on understanding the evolution of the fold belts of eastern Yakutia. Parfenov immediately became a proponent of terrane analysis as it evolved in the early 1980s and was the primary mover in developing the terrane map of northeast Russia in the late 1990s. In 1990, he developed joint programs with the University of Alaska Fairbanks and Michigan State University, and later with Stanford University and the U.S. Geological Survey, opening eastern Russia to western scientists. His life's work was synthesized in a monograph entitled "Tectonics, Geodynamics, and metallogenesis of the Territory of the Sakha Republic (Yakutia)" published in Russian in 2001 and currently being prepared in English translation. As a result of his efforts we now have a basic understanding of the plate tectonic evolution of northeast Russia as

  8. Animated tectonic reconstruction of the Lower Colorado River region: Implications for Late Miocene to Present deformation

    Science.gov (United States)

    Bennett, Scott E. K.; Darin, Michael H.; Dorsey, Rebecca J.; Skinner, Lisa A.; Umhoefer, Paul J.; Oskin, Michael E.

    2016-01-01

    Although the majority of late Miocene to present Pacific-North America plate boundary strain has been accommodated by faults of the San Andreas and Gulf of California systems, growing evidence of dextral shear east of the San Andreas Fault indicates that a component of plate boundary deformation occurred in the lower Colorado River (LoCR) region. Large-scale tectonic reconstructions across the Gulf of California and Salton Trough (GCAST) region (Fig. 1), a ~500 km-wide zone of deformation that affected the western margin of North America, provide important constraints on the location, timing, style, and magnitude of crustal deformation in the LoCR region (Fig. 2). Characterizing Miocene to present deformation in the LoCR region is important to resolve the presence and kinematics of upper crustal structures that accommodated intracontinental strain and improves our understanding of the processes that promoted localized or diffuse strain during reorganization of the Pacific-North America plate boundary.

  9. Disparate Tectonic Settings of Devastating Earthquakes in Mexico, September 2017

    Science.gov (United States)

    Li, J.; Chen, W. P.; Ning, J.

    2017-12-01

    Large earthquakes associated with thrust faulting along the plate interface typically pose the highest seismic risk along subduction zones. However, both damaging earthquakes in Mexico of September 2017 are notable exceptions. The Tehuantepec event on the 8th (Mw 8.1) occurred just landward of the trench but is associated with normal faulting, akin to the large (Ms 8) historical event of 1931 that occurred about 200 km to the northwest along this subduction zone. The Puebla earthquake (on the 19th, Mw 7.1) occurred almost 300 km away from the trench where seismic imaging had indicated that the flat-lying slab steepens abruptly and plunges aseismically into the deep mantle. Here we show that both types of tectonic settings are in fact common along a large portion of the Mexican subduction zone, thus identifying source zones of potentially damaging earthquakes away from the plate interface. Additionally, modeling of broadband waveforms made clear that another significant event (Mw 6.1) on the 23rd, is associated with shallow normal faulting in the upper crust, not directly related to the two damaging earthquakes.

  10. Active Deformation in the Overriding Plate Associated with Temporal Changes of the Philippine Sea Plate Motion

    Science.gov (United States)

    Ishiyama, T.; Sato, H.; Van Horne, A.

    2015-12-01

    We present detailed geologic evidence linking changes over time in Philippine Sea plate (PHS) motion and intracontinental deformation in central and southwest (SW) Japan during the Pliocene and after. In the early Pliocene, subduction of the PHS plate under SW Japan restarted in a northerly direction after period of deceleration or cessation. Later, motion changed to a more westerly direction. Corresponding geological changes found in the overriding plate include unconformities in the forearc basins, changes in slip sense on faults, depocenter migration, re-organization of drainage systems and volcanism. Quaternary intraplate deformation is prominent north of the Median Tectonic Line (MTL) inactive segment, above a shallow flat slab. In contrast, less Quaternary tectonic activity is found north of the MTL active segment which lies over a steadily-slipping portion of the subducting slab that behaves as a less-deformed rigid block. Depocenters and active thrusting have migrated north/northwestward over the past 5 My above the shallow flat slab segment of the PHS. We reconstructed the Plio-Pleistocene migration history using Neogene stratigraphy and shallow seismic reflection profiles. We see shallow PHS slab contact with the lower continental crust in our deep seismic reflection profiles, which may explain its enhanced downward drag of the overriding plate and synchronous strong compression in the crust. We find evidence of more westerly PHS plate subduction since the middle Pleistocene in (1) unconformities in the Kumano forearc basin deposits in SW Japan, (2) drastic stream captures in Shikoku, and (3) concordant changes in fault slip sense from thrust to dextral slip along the MTL. Oblique subduction could have induced stronger horizontal stress in the overriding plate above the shallow flat slab which could account for the increasing geologic slip rate observed on active structures. During four repetitions of megathrust earthquake sequences since the 17th century

  11. From transpressional to transtensional tectonics in Northern Central America controlled by Cocos - Caribbean subduction coupling change

    Science.gov (United States)

    Alonso-Henar, Jorge; Alvarez-Gomez, José Antonio; Jesús Martinez-Diaz, José

    2017-04-01

    The Central American Volcanic Arc (CAVA) is located at the western margin of the Caribbean plate, over the Chortís Block, spanning from Guatemala to Costa Rica. The CAVA is associated to the subduction of the Cocos plate under the Caribbean plate at the Middle America Trench. Our study is focused in the Salvadorian CAVA segment, which is tectonically characterized by the presence of the El Salvador Fault Zone (ESFZ), part of the western boundary of a major block forming the Caribbean plate (the Chortis Block). The structural evolution of the western boundary of the Chortis Block, particularly in the CAVA crossing El Salvador remains unknown. We have done a kinematic analysis from seismic and fault slip data and combined our results with a review of regional previous studies. This approach allowed us to constrain the tectonic evolution and the forces that control the deformation in northern Central America. Along the active volcanic arc we identified active transtensional deformation. On the other hand, we have identified two deformation phases in the back arc region: A first one of transpressional wrenching close to simple shearing (Miocene); and a second one characterized by almost E-W extension. Our results reveal a change from transpressional to transtensional shearing coeval with a migration of the volcanism towards the trench in Late Miocene times. This strain change could be related with a coupled to decoupled transition on the Cocos - Caribbean subduction interface, which could be related to a slab roll-back of the Cocos Plate beneath the Chortis Block. The combination of different degrees of coupling on the subduction interface, together with a constant relative eastward drift of the Caribbean Plate, control the deformation style along the western boundary of the Chortis Block.

  12. Lithosphere-mantle coupling and the dynamics of the Eurasian Plate

    NARCIS (Netherlands)

    Warners-Ruckstuhl, K.N.; Govers, R.; Wortel, R.

    2012-01-01

    Mechanical equilibrium of tectonic plates implies that lithospheric edge and body forces are balanced by forces arising from interaction with the underlying mantle. We use this quantitative physical relation to integrate existing modelling approaches of lithosphere dynamics and mantle flow into a

  13. What drives microplate motion and deformation in the northeastern Caribbean plate boundary region?

    NARCIS (Netherlands)

    van Benthem, S.A.C.; Govers, R.; Wortel, R.

    2014-01-01

    The north Caribbean plate boundary zone is a broad deformation zone with several fault systems and tectonic blocks that move with different velocities. The indentation by the Bahamas Platform (the “Bahamas Collision”) is generally invoked as a cause of this fragmentation. We propose that a second

  14. Tectonic, Climatic and Anthropogenic Vertical Land Movements in Western Europe by Repeated Absolute Gravity Measurements

    Science.gov (United States)

    van Camp, M. J.; de Viron, O.; Lecocq, T.; Hinzen, K. G.; Quinif, Y.; Williams, S. D.; Camelbeeck, T.

    2010-12-01

    In continental plate interiors, tectonic deformations are small and the associated ground surface movements remain close to or below the accuracy of current geodetic techniques, and at the limit of the noise level. An absolute gravimeter is an appropriate tool to quantify slow vertical movements, as this instrument, based on length and time standards, is drift free and does not depend on any terrestrial reference frame. Repeated absolute gravity (AG) measurements have been performed in Oostende (Belgian coastline) and at 8 stations along a southwest-northeast profile across the Belgian Ardennes and the Roer Valley Graben (Germany), in order to estimate the tectonic deformations in the area. After 7-13 years (depending on the station), we find evidence that the movements are no larger than a few millimeter per year and result from a combination of anthropogenic, climatic, tectonic, and Glacial Isostatic Adjustment (GIA) effects. This demonstrates the importance of precisely modeling the GIA effects in order to investigate intraplate tectonic deformations at the sub-millimeter level. This study also shows that AG measurements, repeated once or twice a year, can resolve vertical velocities at the 1.0 mm/yr level after 10 years, even in difficult conditions, provided that the gravimeter is carefully maintained.

  15. Africa's Megafans and Their Tectonic Setting

    Science.gov (United States)

    Wilkinson, M. J.; Burke, K.

    2016-01-01

    fans lies on the western margin of the Congo Basin (Mayombe Swell), and on the coastal slopes of the Namibia Swell. Sheer size may have militated aginst the recognition of many megafans: the largest in the Sahara are the Teghahart (378 km, Hoggar Swell, Algeria), and the Wadi Albalata (340 km, Uweinat Swell, Egypt). In southern Africa the largest are the Cubango (320 km, Bié Swell, Angola/ Namibia), and the Limpopo (230 km, Mozambique). (ii) Rift zones (a) Steer's horns basins-wide depressions centered on rifts. The largest contiguous group (n=14) developed in a steer's-horns basin occupies the wide Muglad depression (200-350 km, South Sudan). Four rift-related megafans lie SE of Lake Chad (Chad). Nine megafans occupy the complex Anza Rift in Kenya/South Somalia. The Salamat megafan (Chad), is unusual because it oriented parallel with the linked Salamat, Doseo and Doba rift axes, and is consequently one of the longest in Africa (465 km). (b) Rift depressions sensu stricto. Most rifts are too narrow to provide a transverse dimension large enough to accommodate megafans. Although well-known, the Okavango Rift (NW Botswana, NE Namibia) is unique in Africa in hosting three megafans within identifiable faulted margins. The Nile megafan is Africa's largest (476 km) and comprises the vast Sudd wetland (South Sudan). An explanation for its remarkable size may be its location in a depression at the junction of two conducive tectonic zones, the East African Swell margin and the Muglad steer's-horns depression. Discharge of the River Nile, the largest in the region, has allowed the Nile megafan to outcompete neighboring megafans for space.

  16. Preface of special issue on ;tectonics, volcanism and geo-energy in East Asia;

    Science.gov (United States)

    Song, Sheng-Rong; Chen, Cheng-Hong; Ryu, Byong-Jae; Lin, Saulwood

    2017-11-01

    The East Asia, from north to south, including Russia, China, Korea, Japan, Taiwan, Philippines and Indonesia etc., is one of the most active tectonic and natural hazardous regions in the world. The subduction and collision zones, such as the Pacific Plate subducting into the Japan Arc and the Philippine Sea, and the Philippine Sea Plate subducting into the Eurasia Plate, and the collision zones of the Philippine Sea Plate with the Asian continental margin in the Taiwan mountain belt, and the India Plate with the Eurasia Plate in Himalaya mountain belts, distribute widely in this region. It is also the most densely populated areas in the world. More than two billion people (one/third populations of the world) live in East Asia. Most of disastrous natural hazards, such as volcanic eruptions, earthquakes and debris flows induced by floods occur frequently and cause many building collapses and causalities in this area. Geoscientists, therefore, must seriously consider and endeavor for mitigations of the natural hazards and reduction of the properties lose and human death.

  17. A Natural Model of Active Transpressional Tectonics the en Échelon Structures of the Oriente Deep, Along the Northern Caribbean Transcurrent Plate Boundary (Southern Cuban Margin Un modèle naturel de tectonique transpressive active Les structures en échelon de la fosse de l'Oriente le long de la limite de plaques décrochante Nord-Caraïbe

    Directory of Open Access Journals (Sweden)

    Calais E.

    2006-11-01

    Full Text Available A seabearn and seismic reflection structural study of the Oriente Deep, located along the northern Caribbean transcurrent plate boundary, allows us to image in three dimensions active transpressional structures (cruise SEA-CARIB II, R/V Jean Charcot. These structures are folds and reverse faults. The folds display an en échelon arrangement and are set within three E-W trending alignments. The folds appear with an axis trending 30° to 40° to the shear direction. Their axes have undergone a rotation which gives them in plan a sigmoidal Zshape. The reverse faults formed after the folds and are located at the bases of the anticlines. The folding occurs outside the main strike-slip fault, above inactive burried faults affecting the basement of the Oriente Deep. The Oriente Deep is a exceptional natural model for the study of active transpressional deformation along a major strike-slip fault. La campagne océanographique SEACARIB II du N/O Jean Charcot a permis l'étude structurale du bassin de l'Oriente, situé le long de la limite de plaques décrochante nord caraïbe au sud de Cuba. Cette étude, par Seabeam et sismique réflexion, y a révélé des structures transpressives actives (plis et failles inverses et a permis de les illustrer en trois dimensions. Au sein de ce bassin, les plis sont disposés en échelon en trois alignements E-W. La direction de l'axe des plis naissant fait un angle de 30° à 40° avec la direction du décrochement principal. Les axes des plis subissent ensuite une rotation qui leur donne, en carte, une forme sigmoïdale en Z . Des failles inverses se forment après les plis à la base des anticlinaux. Le plissement est localisé en avant du décrochement principal, au-dessus de failles inactives enfouies affectant le substratum du bassin de l'Oriente. Le bassin de l'Oriente est un modèle naturel exceptionnel pour l'étude de déformations transpressives actives le long d'un décrochement actif majeur.

  18. Create Your Plate

    Medline Plus

    Full Text Available ... Monthly In Memory In Honor Become a Member En Español Type 1 Type 2 About Us Online ... Print Page Text Size: A A A Listen En Español Create Your Plate Create Your Plate is ...

  19. Create Your Plate

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    Full Text Available ... Diabetes Meal Plans Create Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook with Heart-Healthy Foods Holiday Meal Planning ... Planning Meals Diabetes Meal Plans and a Healthy Diet Create Your Plate Meal Planning for Vegetarian Diets ...

  20. Create Your Plate

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    Full Text Available ... Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook with Heart-Healthy Foods Holiday Meal Planning What Can I Eat? Making ... Forecast® magazine: wcie-meal-planning, . In this ... Your Plate Meal Planning for Vegetarian Diets Gluten Free Diets Holiday Meal Planning Cook ...

  1. Create Your Plate

    Medline Plus

    Full Text Available ... In Memory In Honor Become a Member En Español Type 1 Type 2 About Us Online Community ... Page Text Size: A A A Listen En Español Create Your Plate Create Your Plate is a ...

  2. Growth Plate Injuries

    Science.gov (United States)

    ... cause any lasting problems for your child or teen. Growth plates are areas of growing tissues that cause ... are replaced by solid bone. Who gets them? Growth plate injuries happen to children and teens. This injury happens twice as often in boys ...

  3. Create Your Plate

    Medline Plus

    Full Text Available ... Planning Meals Diabetes Meal Plans Create Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook with Heart- ... Create Your Plate Meal Planning for Vegetarian Diets Gluten Free Diets Holiday Meal Planning Cook with Heart-Healthy Foods ...

  4. Two-dimensional thermal modeling associated with subduction of the Philippine Sea plate in southern Kyushu, Japan

    Science.gov (United States)

    Suenaga, Nobuaki; Yoshioka, Shoichi; Matsumoto, Takumi; Ji, Yingfeng

    2018-01-01

    In Hyuga-nada, southern Kyushu in southwest Japan, afterslip events were found in association with the two large interplate earthquakes, which occurred on October 19 and December 3, 1996. In Kyushu, low-frequency earthquakes (LFEs) and tectonic tremors are not common, but a considerable concentration of tectonic tremors is observed beneath the Pacific coast of the Miyazaki prefecture. To investigate the generation mechanisms of these seismic events, we performed 2-D box-type time-dependent thermal modeling in southern Kyushu. As a result, the temperature range of the upper surface of the subducting Philippine Sea (PHS) plate, where the afterslip occurred, reached approximately 300 to 350 °C. The temperatures where the tectonic tremors occurred ranged from 450 to 650 °C in the mantle wedge corner. We also estimated the spatial distribution of water content within the subducting PHS plate, using phase diagrams of hydrous mid-ocean ridge basalt (MORB) and ultramafic rock. Then, we found that no characteristic phase transformations accompany the dehydration of the subducting PHS plate in the afterslip region, but phase transformation from lawsonite blueschist to lawsonite eclogite is expected within the oceanic crust of the PHS plate just below the active region of the tectonic tremors. Our estimated water content distribution is consistent with the VP/VS ratio calculated from the seismic tomography. Therefore, we conclude that the occurrence of the afterslip is controlled by the temperature condition at the plate boundary, and occurs near the down-dip limit of the seismogenic zone. On the other hand, determining the major factors leading to the occurrence of the tectonic tremors is difficult, we estimated the temperature in the mantle wedge is ranging from 450 °C to 650 °C, and dehydration of 1.0 wt% would be expected from the subducting PHS plate near the active region of the tectonic tremors.

  5. Plate motion changes drive Eastern Indian Ocean microcontinent formation

    Science.gov (United States)

    Whittaker, J. M.; Williams, S.; Halpin, J.; Wild, T.; Stilwell, J.; Jourdan, F.; Daczko, N. R.

    2016-12-01

    The roles of plate tectonic or mantle dynamic forces in rupturing continental lithosphere remain controversial. Particularly enigmatic is the rifting of microcontinents from mature continental rifted margin - several well-studied microcontinent calving events coincide in space and time with mantle plume activity, but the significance of plumes in driving microcontinent formation remains controversial, and a role for plate-driven processes has also been suggested. In 2011, our team discovered two new microcontinents in the eastern Indian Ocean, the Batavia and Gulden Draak microcontinents. These microcontinents are unique as they are the only surviving remnants of the now-destroyed or highly deformed Greater Indian margin and provide us with an opportunity to test existing models of microcontinent formation against new observations. Here, we explore models for microcontinent formation using our new data from the Eastern Indian Ocean in a plate tectonic reconstruction framework. We use Argon dating and paleontology results to constrain calving from greater India at 101-104 Ma. This region had been proximal to the active Kerguelen plume for 30 Myrs but we demonstrate that calving did not correspond with a burst of volcanic activity. Rather, it is likely that plume-related thermal weakening of the Indian passive margin preconditioned it for microcontinent formation but calving was triggered by changes in plate tectonic boundary forces. Changes in the relative motions between Indian and Australia led to increasing compressive forces along the long-offset Wallaby-Zenith Fracture Zone, which was eventually abandoned during the jump of the spreading ridge into the Indian continental margin.

  6. Climate vs. tectonic induced variations in Cenozoic sediment supply from western Scandinavia

    DEFF Research Database (Denmark)

    Gołędowski, Bartosz; Nielsen, S.B.; Clausen, O.R.

    . Nielsen, S.B., et al., The evolution of western Scandinavian topography: A review of Neogene uplift versus the ICE (isostasy-climate-erosion) hypothesis. Journal of Geodynamics, 2009. 47(2-3): p. 72-95. 3. Summerfield, M.A., Global geomorphology: an introduction to the study of landforms. Global...... is much less constrained. For this period we therefore search for an alternative explanation in terms of climate and climate change [1-3] Methods The extensive seismic and well data set allow investigation of inland erosion rates via the offshore distribution of sediments. However, varying marine......-quantitative approach is applied in this study. Tectonism and climate in the Cenozoic era A number of Cenozoic tectonic episodes have been constrained by the offshore sedimentary record: 1) structures related to the opening of the North Atlantic [5], 2) changes in plate motions [6], 3) inversion movements...

  7. Summary of the stretching tectonics research

    International Nuclear Information System (INIS)

    Yu Dagan

    1994-01-01

    The rise of stretching tectonics is established on the basis of recent structural geology theory, the establishment of metamorphic nucleus complex structural model on one hand plays an important promoting art to the development of stretching structure, on the other hand, it needs constant supplement and perfection in practice. Metamorphic nucleus complex is the carrier of comparatively deep geological information in vertical section of the crust and has wide distribution in the era of south China. Evidently, it can be taken as the 'key' to understanding the deep and studying the basement, Strengthening the study will play the important promoting role to the deep prospecting. The study of stretching tectonics is not only limited within the range of structure and metamorphism, but combine with the studies of sedimentation, magmatism, metamorphism and mineralization, thus form a new field of tectonic geology of self-developing system

  8. Lohse's historic plate archive

    Science.gov (United States)

    Tsvetkov, M.; Tsvetkova, K.; Richter, G.; Scholz, G.; Böhm, P.

    The description and the analysis of Oswald Lohse's astrophotographic plates, collected at the Astrophysical Observatory Potsdam in the period 1879 - 1889, are presented. 67 plates of the archive, taken with the greatest instrument of the observatory at that time - the refractor (D = 0.30 m, F = 5.40 m, scale = 38''/mm) and with the second heliographic objective (D = 0.13 m, F = 1.36 m, scale = 152''/mm) - - survived two world wars in relative good condition. The plate emulsions are from different manufacturers in the beginning of astrophotography (Gädicke, Schleussner, Beernaert, etc.). The sizes of the plates are usually 9x12 cm2, which corresponds to fields of 1.2deg and 5deg respectively for each instrument mentioned above. The average limiting magnitude is 13.0(pg). Besides of the plates received for technical experiments (work on photographic processes, testing of new instruments and methods of observations), the scientific observations follow programs for studies of planet surfaces, bright stars, some double stars, stellar clusters and nebulous objects. Lohse's archive is included into the Wide Field Plate Database (http://www.skyarchive.org) as the oldest systematic one, covering the fields of Orion (M42/43), Pleiades, h & chi Persei, M37, M3, M11, M13, M92, M31, etc. With the PDS 2020 GM+ microdensitometer of Münster University 10 archive plates were digitized.

  9. The DeLong islands and Arctic tectonic reconstuctions

    Science.gov (United States)

    Pease, Victoria; Tegner, Christian

    2014-05-01

    samples collected on Henrietta and Jeanetta islands. These data will be used to evaluate the provenance of the sediments in order to determine i) similarities and differences between the islands, ii) compare detrital populations to other deposits from other locations in the Arctic (e.g. Svalbard, Franz Josef Land, etc.), and iii) determine whether or not the De Long islands can be used as a piercing point and therefore test various tectonic reconstruction scenarios for the high Arctic. [Tegner & Pease, 2014. Continental Flood Basalts of Bennett Island, East Siberian Sea: High Arctic geodynamics, EGU abstract.

  10. Deformation of the Northwestern Okhotsk Plate: How is it happening?

    Science.gov (United States)

    Hindle, D.; Fujita, K.; Mackey, K.

    2009-09-01

    The Eurasia (EU) - North America (NA) plate boundary zone across Northeast Asia still presents many open questions within the plate tectonic paradigm. Constraining the geometry and number of plates or microplates present in the plate boundary zone is especially difficult because of the location of the EU-NA euler pole close to or even upon the EU-NA boundary. One of the major challenges remains the geometry of the Okhotsk plate (OK). whose northwestern portion terminates on the EU-OK-NA triple junction and is thus caught and compressed between converging EU and NA. We suggest that this leads to a coherent and understandable large scale deformation pattern of mostly northwest-southeast trending strike-slip faults which split Northwest OK into several extruding slivers. When the fault geometry is analysed together with space geodetic and focal mechanism data it suggests a central block which is extruding faster bordered east and west by progressively slower extruding blocks until the OK plate boundary faults are encountered. Taking into account elastic loading from both the intra-OK faults and the OK-Pacific (PA) boundary reconciles geodetic motions with geologic slip rates on at least the OK-NA boundary which corresponds to the Ulakhan fault.

  11. High loading uranium plate

    International Nuclear Information System (INIS)

    Wiencek, T.C.; Domagala, R.F.; Thresh, H.R.

    1990-01-01

    Two embodiments of a high uranium fuel plate are disclosed which contain a meat comprising structured uranium compound confined between a pari of diffusion bonded ductile metal cladding plates uniformly covering the meat, the meat hiving a uniform high fuel loading comprising a content of uranium compound greater than about 45 Vol. % at a porosity not greater than about 10 Vol. %. In a first embodiment, the meat is a plurality of parallel wires of uranium compound. In a second embodiment, the meat is a dispersion compact containing uranium compound. The fuel plates are fabricated by a hot isostatic pressing process

  12. Drilling to investigate processes in active tectonics and magmatism

    Science.gov (United States)

    Shervais, J.; Evans, J.; Toy, V.; Kirkpatrick, J.; Clarke, A.; Eichelberger, J.

    2014-12-01

    convergent plate margins (subduction zones). This workshop brought together a diverse group of scientists with a broad range of scientific experience and interests. A particular strength was the involvement of both early-career scientists, who will initiate and carry out these new research programs, and more senior researchers with many years of experience in scientific drilling and active tectonics research. Each of the themes and questions outlined above has direct benefits to society, including improving hazard assessment, direct monitoring of active systems for early warning, renewable and non-renewable resource and energy exploitation, and predicting the environmental impacts of natural hazards, emphasizing the central role that scientific drilling will play in future scientific and societal developments.

  13. Developing an Education and Public Outreach (EPO) program for Caltech's Tectonics Observatory

    Science.gov (United States)

    Kovalenko, L.; Jain, K.; Maloney, J.

    2012-12-01

    The Caltech Tectonics Observatory (TO) is an interdisciplinary center, focused on geological processes occurring at the boundaries of Earth's tectonic plates (http://www.tectonics.caltech.edu). Over the past four years, the TO has made a major effort to develop an Education and Public Outreach (EPO) program. Our goals are to (1) inspire students to learn Earth Sciences, particularly tectonic processes, (2) inform and educate the general public about science in the context of TO discoveries, and (3) provide opportunities for graduate students, postdocs, and faculty to do outreach in the local K-12 schools and community colleges. Our work toward these goals includes hosting local high school teachers and students each summer for six weeks of research experience (as part of Caltech's "Summer Research Connection"); organizing and hosting an NAGT conference aimed at Geoscience teachers at community colleges; participating in teacher training workshops (organized by the local school district); hosting tours for K-12 students from local schools as well as from China; and bringing hands-on activities into local elementary, middle, and high school classrooms. We also lead local school students and teachers on geology field trips through nearby canyons; develop education modules for undergraduate classes (as part of MARGINS program); write educational web articles on TO research (http://www.tectonics.caltech.edu/outreach/highlights/), and regularly give presentations to the general public. This year, we started providing content expertise for the development of video games to teach Earth Science, being created by GameDesk Institute. And we have just formed a scientist/educator partnership with a 6th grade teacher, to help in the school district's pilot program to incorporate new national science standards (NSTA's Next Generation Science Standards, current draft), as well as use Project-Based Learning. This presentation gives an overview of these activities.

  14. Regional Gravity and Magnetic Studies of Crustal Structure in Northeastern Mexico and Their Tectonic Implications

    Science.gov (United States)

    Sanchez-Alvarez, R.; Urrutia-Fucugauchi, J.

    2006-05-01

    Detailed modeling of regional Bouguer gravity and aeromagnetic anomalies in northeastern Mexico permits documentation of the crustal structure and tectonic relationships of major structural features at the southern margin of the North American craton. This region has experienced a complex evolution with major events that include Paleozoic subduction and consumption of an ocean, subsequent collision of continental plates to form the supercontinent Pangaea, major faulting and deformation, middle Mesozoic fragmentation and rifting between North and South America, formation of the Gulf of Mexico and Caribbean, strike-slip lateral faulting, Laramide compression and Cenozoic extension. The Marathon-Ouachita system in northern Mexico shows the effects of strike-slip faulting and deformation, which can be traced from its potential field anomalies and oil- exploration borehole logs and data. Major tectonic elements from west to east are the foreland, frontal zone, interior zone, the Coahuila terrane, and a large elongated intrusive province. Remnants of the Permo-Triassic magmatic arc and exotic continental crust are present in the Coahuila and Gulf coast terranes. They are all affected by lateral faulting along roughly east-west regional faults, and, if the characterization of tectonic elements is correct, the proposed paleoreconstruction sets limits on the amount of lateral translation and regional crustal deformation in northern Mexico. Younger deformational episodes during the Cenozoic need to be accounted for in the tectonic reconstruction. The apparent displacement of the intrusive belt is of the order of 600-700 km. The intrusive belt and the Ouachita frontal and interior zones appear also fragmented and displaced in the Coahuila area by lateral faults such as San Marcos, China-Sierra Mojada, Barroteran, San Carlos and Sabinas. Displacement is less than that observed for the Mojave-Sonora megashear south of Monterrey area, as documented from the gravity and

  15. Tectonic and climatic considerations for deep geological disposal of radioactive waste: A UK perspective

    Energy Technology Data Exchange (ETDEWEB)

    McEvoy, F.M., E-mail: fmcevoy@bgs.ac.uk [British Geological Survey, Keyworth, Nottingham NG12 5GG (United Kingdom); Schofield, D.I. [British Geological Survey, Tongwynlais, CF15 7NE (United Kingdom); Shaw, R.P. [British Geological Survey, Keyworth, Nottingham NG12 5GG (United Kingdom); Norris, S. [Radioactive Waste Management Limited, B587, Curie Avenue, Harwell, Didcot OX11 0RH (United Kingdom)

    2016-11-15

    Identifying and evaluating the factors that might impact on the long-term integrity of a deep Geological Disposal Facility (GDF) and its surrounding geological and surface environment is central to developing a safety case for underground disposal of radioactive waste. The geological environment should be relatively stable and its behaviour adequately predictable so that scientifically sound evaluations of the long-term radiological safety of a GDF can be made. In considering this, it is necessary to take into account natural processes that could affect a GDF or modify its geological environment up to 1 million years into the future. Key processes considered in this paper include those which result from plate tectonics, such as seismicity and volcanism, as well as climate-related processes, such as erosion, uplift and the effects of glaciation. Understanding the inherent variability of process rates, critical thresholds and likely potential influence of unpredictable perturbations represent significant challenges to predicting the natural environment. From a plate-tectonic perspective, a one million year time frame represents a very short segment of geological time and is largely below the current resolution of observation of past processes. Similarly, predicting climate system evolution on such time-scales, particularly beyond 200 ka AP is highly uncertain, relying on estimating the extremes within which climate and related processes may vary with reasonable confidence. The paper highlights some of the challenges facing a deep geological disposal program in the UK to review understanding of the natural changes that may affect siting and design of a GDF. - Highlights: • Natural processes are key to developing a safety case for geological disposal. • Key factors include plate tectonic and climate-mediated processes. • Process variability is a challenge to predicting the natural environment. • We highlight the challenges for geological disposal programs using

  16. Create Your Plate

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    Full Text Available ... managing diabetes and losing weight. Creating your plate lets you still choose the foods you want, but ... you have an easy portion control solution that works. Last Reviewed: October 8, 2015 Last Edited: September ...

  17. What's On Your Plate?

    Science.gov (United States)

    ... what these nutrients do in your body and what foods they are found in. Plans for Healthy Living ... food choices. Get more nutrition information online with What's On Your Plate? Smart Food Choices for Healthy Aging from the National Institute ...

  18. Create Your Plate

    Medline Plus

    Full Text Available ... Plate is a simple and effective way to manage your blood glucose levels and lose weight. With ... been easier. It can be a challenge to manage portion control wherever you are. Now, our best- ...

  19. Create Your Plate

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    Full Text Available ... Count Glycemic Index Low-Calorie Sweeteners Sugar and Desserts Fitness Exercise & Type 1 Diabetes Get Started Safely ... blood glucose levels and lose weight. With this method, you fill your plate with more non-starchy ...

  20. Create Your Plate

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    Full Text Available ... Edited: September 14, 2016 Articles from Diabetes Forecast® magazine: wcie-meal-planning, . In this section Food Planning Meals Diabetes Meal Plans and a Healthy Diet Create Your Plate Meal Planning for Vegetarian Diets Gluten ...

  1. Create Your Plate

    Medline Plus

    Full Text Available ... Children and Type 2 Diabetes Know Your Rights Employment Discrimination Health Care Professionals Law Enforcement Driver's License ... blood glucose levels and lose weight. With this method, you fill your plate with more non-starchy ...

  2. Humvee Armor Plate Drilling

    National Research Council Canada - National Science Library

    2004-01-01

    When drilling holes in hard steel plate used in up-armor kits for Humvee light trucks, the Anniston Army Depot, Anniston, Alabama, requested the assistance of the National Center for Defense Manufacturing and Machining (NCDMM...

  3. Create Your Plate

    Medline Plus

    Full Text Available ... one side, cut it again so you will have three sections on your plate. Fill the largest ... home, the office, or somewhere in between, you have an easy portion control solution that works. Last ...

  4. Plio-Pleistocene magnetostratigraphy of northern Bohai Bay and its implications for tectonic events since ca. 2.0 Ma

    Science.gov (United States)

    Xu, Qinmian; Yuan, Guibang; Yang, Jilong; Xin, Houtian; Yi, Liang; Deng, Chenglong

    2017-11-01

    The sediments of Bohai Bay Basin in North China have recorded the processes of basin filling and structural evolution, which may have resulted from the destruction of the North China Craton during the late Mesozoic and early Cenozoic. However, the absence of a reliable chronostratigraphic framework for the sedimentary sequences in the basin has prevented a comprehensive understanding of these processes. In this study, we combine paleomagnetic and sedimentary analyses of the sediments from two new boreholes (NY05 and TZ02) from northern Bohai Bay to provide new insights into the sedimentary history and regional tectonic processes since the Pliocene. The main findings are as follows: (1) Magnetite and hematite are the main carriers of the characteristic remanent magnetization. (2) The boreholes record the Brunhes and Gauss normal chrons, and the Matuyama reversed chron. (3) Subsidence-related differences in the depths of the Matuyama/Brunhes (M/B) and Gauss/Matuyama (G/M) boundaries, sediment accumulation rates, and the sedimentary environments of the different tectonic units, enable us to identify that tectonic movements started in the Olduvai normal subchron and the development of the WNW-orientated tectonic features were intensified. (4) In the Huanghua depression, comparative analysis of subsidence-related differences between western and northern Bohai Bay indicates that the subsidence of the northern Bohai Bay may have been superimposed on the WNW-orientated tectonic activity and faulting associated with the collision between the Indian and the Eurasian Plates, in the context of localized subsidence.

  5. Provenance, tectonic setting and source-area weathering of the ...

    Indian Academy of Sciences (India)

    s12040-017-0803-5. Provenance, tectonic setting and source-area weathering of the lower Cambrian ... (2010) carried out detrital zircon studies in order to correlate ...... and tectonic evolution of the Central Asian Orogenic Belt;. Chinese Sci. Bull.

  6. Neutron imaging plates

    International Nuclear Information System (INIS)

    Niimura, Nobuo

    1995-01-01

    Imaging plates have been used in the field of medical diagnosis since long ago, but their usefulness was verified as the two-dimensional detector for analyzing the X-ray crystalline structure of high bio molecules like protein, and they have contributed to the remarkable progress in this field. The great contribution is due to the excellent features, such as the detection efficiency of about 100%, the positional resolution smaller than 0.2 mm, the dynamic range of five digits, and the area of several hundreds mm square. The neutron imaging plates have not yet obtained the sufficient results. It was planned to construct the neutron diffractometer for biological matters, and to put imaging plate neutron detectors (IP-ND) to practical use as the detector. The research on the development of IP-NDs was carried out, and the IPp-NDs having the performance comparable with that for X-ray were able to be produced. Imaging plates are the integral type two-dimensional radiation detector using photostimulated luminescence matters, and their principle is explained. As to neutron imaging plates, the converter, neutron detection efficiency and the flight of secondary particles in photo-stimulated luminescence matters are described. As for the present state of development of neutron imaging plates, the IP-NDs made for trial, the dynamic range, the positional resolution, the detection efficiency and the kinds of converters, and the application of IP-NDs are reported. (K.I.)

  7. 3D monitoring of active tectonic structures

    Czech Academy of Sciences Publication Activity Database

    Stemberk, Josef; Košťák, Blahoslav; Vilímek, V.

    2003-01-01

    Roč. 36, 1-2 (2003), s. 103-112 ISSN 0264-3707 R&D Projects: GA MŠk OC 625.10 Institutional research plan: CEZ:AV0Z3046908 Keywords : tectonics * monitoring * active structures Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.754, year: 2003

  8. Radial Extension, Prototypicality, and Tectonic Equivalence

    Directory of Open Access Journals (Sweden)

    Shaver Stephen R.

    2018-01-01

    Full Text Available In his book “Without Metaphor, No Saving God: Theology After Cognitive Linguistics”, Robert Masson describes a metaphoric process by which newly accepted truths emerge: for example, in the assertion “Jesus is the Messiah,” Christians reconfigure the field of meanings associated with an existing concept from the Hebrew scriptures (messiah by asserting its identification with Jesus. Masson dubs this process a “tectonic equivalence” or “tectonic shift.” In this paper I build on Masson‘s work by examining some of the shifts he describes as tectonic through the lens of the cognitive linguistics concepts of radial extension and polysemy. I propose that a lasting tectonic shift may be understood as a blend creating a radial extension that substantially alters the category structure of the original source frame so that the blended space comes to be understood as a central instance of that category. Such an approach allows a fruitful analysis of the similarities and differences among three example blends: god is a rock, jesus is the messiah, and jesus is god.

  9. Tectonically Induced Anomalies Without Large Earthquake Occurrences

    Science.gov (United States)

    Shi, Zheming; Wang, Guangcai; Liu, Chenglong; Che, Yongtai

    2017-06-01

    In this study, we documented a case involving large-scale macroscopic anomalies in the Xichang area, southwestern Sichuan Province, China, from May to June of 2002, after which no major earthquake occurred. During our field survey in 2002, we found that the timing of the high-frequency occurrence of groundwater anomalies was in good agreement with those of animal anomalies. Spatially, the groundwater and animal anomalies were distributed along the Anninghe-Zemuhe fault zone. Furthermore, the groundwater level was elevated in the northwest part of the Zemuhe fault and depressed in the southeast part of the Zemuhe fault zone, with a border somewhere between Puge and Ningnan Counties. Combined with microscopic groundwater, geodetic and seismic activity data, we infer that the anomalies in the Xichang area were the result of increasing tectonic activity in the Sichuan-Yunnan block. In addition, groundwater data may be used as a good indicator of tectonic activity. This case tells us that there is no direct relationship between an earthquake and these anomalies. In most cases, the vast majority of the anomalies, including microscopic and macroscopic anomalies, are caused by tectonic activity. That is, these anomalies could occur under the effects of tectonic activity, but they do not necessarily relate to the occurrence of earthquakes.

  10. Discriminating four tectonic settings: Five new geochemical ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 115; Issue 5. Discriminating four tectonic settings: Five new geochemical diagrams for basic and ultrabasic volcanic rocks based on log–ratio transformation of major-element data. Surendra P Verma Mirna Guevara Salil Agrawal. Volume 115 Issue 5 October 2006 ...

  11. The Phenomenology and Tectonics of Making

    DEFF Research Database (Denmark)

    Carter, Adrian

    2012-01-01

    “The material, detail and structure of a building is an absolute condition. Architecture’s potential is to deliver authentic meanings in what we see, touch and smell; the tectonic is ultimately central to what we feel” Steven Holl...

  12. Tectonic studies in the Lansjaerv region

    International Nuclear Information System (INIS)

    Henkel, H.

    1987-10-01

    This report contains the results and the analysis of ground geophysical measurements and the tectonic interpretation in the 150x200 km Lansjaerv study area. It describes the data and methods used. The significance of strike slip fault patterns in relation to the surface morphology is discussed. The obtained results are used to suggest a tentative model for the present tectonic deformation. The report is part of the bedrock stability programme of SKB. The major conclusions regarding the tectonic structure are: Three regional fault systems are identified, two steep NW and N trending and a third NNE trending with gentle ESE dips, the steep fault systems have strike slip generated deformation patterns both in the Precambrian structures and in the surface morphology, the post-glacial faults of the area are part of this fault pattern and represent movements mainly on reactivated, gently dipping zones, several suspected late or post-glacial, fault related features are found along the steep NW and N faults. Sites for drilling and geodetic networks for deformation measurements are suggested. Detailed background data are documented in additional 4 reports. The basic geophysical and geological datasets are documented in color plotted 1:250 000 maps. A tectonic interpretation map in the same scale has been produced by combined interpretation of magnetic, elevation, elevation relief and gravity data. (orig./HP) With 6 maps

  13. Provenance, tectonics and palaeoclimate of Proterozoic Chandarpur ...

    Indian Academy of Sciences (India)

    climatic condition. The provenance analysis revealed that the Chandarpur clastics were derived from granites and granite–gneisses of a continental block tectonic provenance. Petrographic stud- ies further indicate that high grade metamorphic rocks did not make any perceptible contribution to the Chandarpur system.

  14. Geomorphological features of active tectonics and ongoing ...

    Indian Academy of Sciences (India)

    floods, cloud-bursts and earthquakes. Slopes in the region were formed by combining the effect of geomorphic, tectonic and climatic process and the landslides frequently occurring during the monsoon. The highly deformed, fractured and shattered rocks of Great Himalaya and the prox- imity of active thrusts and fault zones ...

  15. Structural highs on the western continental slope of India: Implications for regional tectonics

    Digital Repository Service at National Institute of Oceanography (India)

    Mukhopadhyay, R.; Rajesh, M.; De, Suritha; Chakraborty, B.; Jauhari, P.

    and Scotese, 1999). Continental rifting coupled with a magma-assisted thermal anomaly from beneath is accepted as the fundamental component of the plate tectonic process (e.g., Northern Ethiopian Rift, Kendall et al., 2005). Similarly it is possible that mafic... 279, 312–315. Kendall, J-M., Stuart, G.W., Ebinger, C.J., Bastow, I.D., Keir, D., 2005. Magma assisted rifting in Ethiopia. Nature 433, 146–148. Krishna, K.S., Murty, G.P.S., Srinivas, K., Rao, D.G., 1992. Magnetic studies over the northern extension...

  16. Contemporary tectonic stress pattern of the Taranaki Basin, New Zealand

    Science.gov (United States)

    Rajabi, Mojtaba; Ziegler, Moritz; Tingay, Mark; Heidbach, Oliver; Reynolds, Scott

    2016-08-01

    The present-day stress state is a key parameter in numerous geoscientific research fields including geodynamics, seismic hazard assessment, and geomechanics of georeservoirs. The Taranaki Basin of New Zealand is located on the Australian Plate and forms the western boundary of tectonic deformation due to Pacific Plate subduction along the Hikurangi margin. This paper presents the first comprehensive wellbore-derived basin-scale in situ stress analysis in New Zealand. We analyze borehole image and oriented caliper data from 129 petroleum wells in the Taranaki Basin to interpret the shape of boreholes and determine the orientation of maximum horizontal stress (SHmax). We combine these data (151 SHmax data records) with 40 stress data records derived from individual earthquake focal mechanism solutions, 6 from stress inversions of focal mechanisms, and 1 data record using the average of several focal mechanism solutions. The resulting data set has 198 data records for the Taranaki Basin and suggests a regional SHmax orientation of N068°E (±22°), which is in agreement with NW-SE extension suggested by geological data. Furthermore, this ENE-WSW average SHmax orientation is subparallel to the subduction trench and strike of the subducting slab (N50°E) beneath the central western North Island. Hence, we suggest that the slab geometry and the associated forces due to slab rollback are the key control of crustal stress in the Taranaki Basin. In addition, we find stress perturbations with depth in the vicinity of faults in some of the studied wells, which highlight the impact of local stress sources on the present-day stress rotation.

  17. Seismic behaviour of mountain belts controlled by plate convergence rate

    Science.gov (United States)

    Dal Zilio, Luca; van Dinther, Ylona; Gerya, Taras V.; Pranger, Casper C.

    2018-01-01

    The relative contribution of tectonic and kinematic processes to seismic behaviour of mountain belts is still controversial. To understand the partitioning between these processes we developed a model that simulates both tectonic and seismic processes in a continental collision setting. These 2D seismo-thermo-mechanical (STM) models obtain a Gutenberg-Richter frequency-magnitude distribution due to spontaneous events occurring throughout the orogen. Our simulations suggest that both the corresponding slope (b value) and maximum earthquake magnitude (MWmax) correlate linearly with plate convergence rate. By analyzing 1D rheological profiles and isotherm depths we demonstrate that plate convergence rate controls the brittle strength through a rheological feedback with temperature and strain rate. Faster convergence leads to cooler temperatures and also results in more larger seismogenic domains, thereby increasing both MWmax and the relative number of large earthquakes (decreasing b value). This mechanism also predicts a more seismogenic lower crust, which is confirmed by a transition from uni- to bi-modal hypocentre depth distributions in our models. This transition and a linear relation between convergence rate and b value and MWmax is supported by our comparison of earthquakes recorded across the Alps, Apennines, Zagros and Himalaya. These results imply that deformation in the Alps occurs in a more ductile manner compared to the Himalayas, thereby reducing its seismic hazard. Furthermore, a second set of experiments with higher temperature and different orogenic architecture shows the same linear relation with convergence rate, suggesting that large-scale tectonic structure plays a subordinate role. We thus propose that plate convergence rate, which also controls the average differential stress of the orogen and its linear relation to the b value, is the first-order parameter controlling seismic hazard of mountain belts.

  18. A New Framework For The Evolution of Terrestrial Planets: Bi-stability, Stochastic Effects, and the Non-Uniqueness of Tectonic States

    Science.gov (United States)

    Weller, M. B.; Lenardic, A.

    2017-12-01

    Of all the Solar System bodies, the Earth is the only one for which significant observation and constraints are accessible such that they can be used to discriminate between competing models of Earth's tectonic evolution. Therefore, it is a natural tendency to use these observations to inform more general models of planetary evolution. Yet, our understating of Earth's evolution is far from complete. Geodynamic and geochemical evidence suggests that plate tectonics may not have operated on the early Earth, with both the timing of its onset and the length of its activity far from certain. In recent years, the potential of tectonic bi-stability (multiple stable, energetically allowed solutions) has been shown to be dynamically viable, both from analytical analysis and through numeric experiments in two and three dimensions. The indication is that multiple tectonic modes may operate on a single planetary body at different times within its temporal evolution. Further, there exists the potential that feedback mechanisms between the internal dynamics and surface processes (e.g., surface temperature changes driven by long term climate evolution), acting at different thermal evolution times, can cause terrestrial worlds to alternate between multiple tectonic states over giga-year timescales. Implied here is that terrestrial planets have the potential to migrate through tectonic regimes at similar `thermal evolutionary times' - points were planets have a similar bulk mantle temperature and energies -, but at very different `temporal times' - time since planetary formation. It can then be shown that identical planets at similar stages of their evolution may exhibit different tectonic regimes due to random fluctuations. A new framework of planetary evolution that moves toward probabilistic arguments based on general physical principals, as opposed to particular rheologies, and incorporates the potential of tectonic regime transitions and multiple tectonics states being viable

  19. Cadmium plating replacements

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, M.J.; Groshart, E.C.

    1995-03-01

    The Boeing Company has been searching for replacements to cadmium plate. Two alloy plating systems seem close to meeting the needs of a cadmium replacement. The two alloys, zinc-nickel and tin-zinc are from alloy plating baths; both baths are neutral pH. The alloys meet the requirements for salt fog corrosion resistance, and both alloys excel as a paint base. Currently, tests are being performed on standard fasteners to compare zinc-nickel and tin-zinc on threaded hardware where cadmium is heavily used. The Hydrogen embrittlement propensity of the zinc-nickel bath has been tested, and just beginning for the tin-zinc bath. Another area of interest is the electrical properties on aluminum for tin-zinc and will be discussed. The zinc-nickel alloy plating bath is in production in Boeing Commercial Airplane Group for non-critical low strength steels. The outlook is promising that these two coatings will help The Boeing Company significantly reduce its dependence on cadmium plating.

  20. Tectonics of the southern escarpment of Ishtar Terra on Venus from observations of morphology and gravity

    International Nuclear Information System (INIS)

    Janle, P.; Jannsen, D.

    1984-01-01

    Maxima of calculated topographical line-of-sight (LOS) gravity attractions caused by Ishtar Terra are shifted to the north with respect to the measured LOS free air gravity maxima south of the highland. This implies a tendency to isostatic compensation of central Ishtar and mass surpluses at the continental border and the southern forelands. The authors present a scenario compatible with the interpretation of the gravity anomalies and morphological features. The existence of global plate tectonics on Venus like on Earth is not necessarily implied, but at least limited horizontal movements of the Venusian lithosphere seem to be likely. This result shows that plate recycling must be considered for heat transfer through the lithosphere beside conduction and hot spot volcanism. (Auth.)

  1. Fluctuations in seafloor spreading predicted by tectonic reconstructions and mantle convection models

    Science.gov (United States)

    Coltice, Nicolas; Seton, Maria; Rolf, Tobias; Müller, R. Dietmar; Tackley, Paul J.

    2013-04-01

    The theory of plate tectonics theory has enabled possible the reconstruction of the ancient seafloor and paleogeography. Over 50 years of data collection and kinematic reconstruction efforts, plate models have improved significantly (Seton et al., 2012) although reconstructions of ancient seafloor are naturally limited by the limited preservation of of very old seafloor. It is challenging to reconstruct ancient ocean basins and associated plate boundaries for times earlier than 200 Ma, since seafloor of this age is not preserved. This means we can merely reconstruct only 5% of the history of the planet in this fashion. However, geodynamic models can now help evaluate how seafloor spreading may evolve over longer time periods, since recent developments of numerical models of mantle convection with pseudo-plasticity can generate long-term solutions that simulate a form of seafloor spreading (Moresi and Solomatov, 1998; Tackley, 2000a; Tackley, 2000b). The introduction of models of continental lithosphere further improves the quality of the predictions: the computed distribution of seafloor ages reproduces the consumption of young seafloor as observed on the present-day Earth (Coltice et al., 2012). The time-dependence of the production of new seafloor has long been debated and there is no consensus on how much it has varied in the past 150My, and how it could have fluctuated over longer time-scales. Using plate reconstructions, Parsons (1982) and Rowley (2002) proposed the area vs. age distribution of the seafloor could have experienced limited fluctuations in the past 150My while others suggest stronger variations would fit the observations equally well (Seton et al., 2009. Here we propose to investigate the global dynamics of seafloor spreading using state-of-the-art plate reconstructions and geodynamic models. We focus on the evolution of the distribution of seafloor ages because fundamental geophysical observations like mantle heat flow or sea level provide

  2. Bending and stretching of plates

    CERN Document Server

    Mansfield, E H; Hemp, W S

    1964-01-01

    The Bending and Stretching of Plates deals with elastic plate theory, particularly on small- and large-deflexion theory. Small-deflexion theory concerns derivation of basic equations, rectangular plates, plates of various shapes, plates whose boundaries are amenable to conformal transformation, plates with variable rigidity, and approximate methods. Large-deflexion theory includes general equations and some exact solutions, approximate methods in large-deflexion theory, asymptotic large-deflexion theories for very thin plates. Asymptotic theories covers membrane theory, tension field theory, a

  3. From P-T-age to secular change and global tectonic regimes (or Essene in reverse - from granulites to blueschists and eclogites over time)

    Science.gov (United States)

    Brown, M.

    2006-12-01

    Essene's contributions began pre-plate tectonics more than 40 years ago; they range from mineralogy to tectonics, from experiments and thermobarometry to elements and isotopes, and from the Phanerozoic to the Precambrian. Eric is a true polymath! Assessing the P-T conditions and age distribution of crustal metamorphism is an important step in evaluating secular change in tectonic regimes and geodynamics. In general, Archean rocks exhibit moderate-P - moderate-to-high-T facies series metamorphism (greenstone belts and granulite terranes); neither blueschists nor any record of deep continental subduction and return are documented and only one example of granulite facies ultrahigh-temperature metamorphism is reported. Granulite facies ultrahigh temperature metamorphism (G-UHTM) is documented in the rock record predominantly from Neoarchean to Cambrian, although G-UHTM facies series rocks may be inferred at depth in younger orogenic systems. The first occurrence of G-UHTM in the rock record signifies a change in geodynamics that generated transient sites of very high heat flow. Many G-UHTM belts may have developed in settings analogous to modern continental backarcs. On a warmer Earth, the formation and breakup of supercontinents, particularly by extroversion, which involved destruction of ocean basins floored by thinner lithosphere, may have generated hotter continental backarcs than those around the modern Pacific rim. Medium-temperature eclogite - high-pressure granulite metamorphism (E-HPGM) also is first recognized in the Neoarchean rock record, and occurs at intervals throughout the Proterozoic and Paleozoic rock record. E- HPGM belts are complementary to G-UHTM belts, and are generally inferred to record subduction-to-collision orogenesis. Blueschists become evident in the Neoproterozoic rock record; lawsonite blueschists and eclogites (high-pressure metamorphism, HPM), and ultrahigh pressure metamorphism (UHPM) characterized by coesite or diamond are

  4. Boninites: Characteristics and tectonic constraints, northeastern Appalachians

    Science.gov (United States)

    Kim, J.; Jacobi, R.D.

    2002-01-01

    Boninites are high Mg andesites that are thought to form in suprasubduction zone tectonic environments as primary melts from refractory mantle. Boninites provide a potential constraint on tectonic models for ancient terranes that contain boninites because the only unequivocal tectonic setting in which "modern" boninites have been recognized is a fore-arc setting. Tectonic models for "modern" boninite genesis include subduction initiation ("infant arc"), fore-arc spreading, and the forearc side of intra-arc rifting (spreading). These models can be differentiated by the relative age of the boninites and to a lesser degree, geochemistry. The distinctive geochemistry of boninites promotes their recognition in ancient terranes. As detailed in this report, several mafic terranes in the northeastern Appalachians contain boninites; these terranes were situated on both sides of Iapetus. The characteristics of these boninites can be used to constrain tectonic models of the evolution of the northeastern Appalachians. On the Laurentian side of Iapetus, "infant arc" boninites were not produced ubiquitously during the Cambrian subduction initiation, unless sampling problems or minimum age dates obscure a more widespread boninite "infant arc". The Cambrian subduction initiation on the Laurentian side was probably characterized by both "infant arc" boninitic arc construction (perhaps the >496 Ma Hawley Formation and the >488 Ma Betts Cove Ophiolite) and "normal" arc construction (Mt. Orford). This duality is consistent with the suggestion that the pre-collisional geometry of the Laurentian margin was complex. The Bay of Islands Complex and Thetford Mines ophiolite boninites are likely associated with forearc/intra-arc spreading during the protracted evolution of the Cambrian arc system. The relatively young boninites in the Bronson Hill Arc suggest that the Taconic continuous eastward subduction tectonic model is less tenable than other models. On the Gondwana side of Iapetus, the

  5. Morphological expression of active tectonics in the Southern Alps

    Science.gov (United States)

    Robl, Jörg; Heberer, Bianca; Neubauer, Franz; Hergarten, Stefan

    2015-04-01

    Evolving drainage pattern and corresponding metrics of the channels (e.g. normalized steepness index) are sensitive indicators for tectonic or climatic events punctuating the evolution of mountain belts and their associated foreland basins. The analysis of drainage systems and their characteristic properties represents a well-established approach to constrain the impact of tectonic and climatic drivers on mountainous landscapes in the recent past. The Southern Alps (SA) are one of the seismically most active zones in the periphery of northern Adria. Recent deformation is caused by the ongoing convergence of the Adriatic and European plate and is recorded by numerous earthquakes in the domain of the SA. Deformation in the SA is characterized by back-thrusting causing crustal thickening and should therefore result in uplift and topography formation. The vertical velocity field determined by GPS-data clearly indicates a belt of significant uplift in the south South alpine indenter between Lake Garda in the west and the Triglav in the east and strong subsidence of the foreland basin surrounding the Mediterranean Sea near Venice, although subsidence is often related to ongoing subduction of the Adriatic microplate underneath Appennines. Despite of these short term time series, timing, rates and drivers of alpine landscape evolution are not well constrained and the linkage between crustal deformation and topographic evolution of this highly active alpine segment remains unclear for the following reasons: (1) The eastern Southern Alps were heavily overprinted by the Pleistocene glaciations and tectonic signals in the alpine landscape are blurred. Only the transition zone to the southern foreland basin remained unaffected and allows an analysis of a glacially undisturbed topography. (2) The major part of this domain is covered by lithology (carbonatic rocks) which is unsuitable for low temperature geochronology and cosmogenic isotope dating so that exhumation and erosion

  6. Plating on Zircaloy-2

    International Nuclear Information System (INIS)

    Dini, J.W.; Johnson, H.R.; Jones, A.

    1979-03-01

    Zircaloy-2 is a difficult alloy to coat with an adherent electroplate because it easily forms a tenacious oxide film in air and aqueous solutions. Procedures reported in the literature and those developed at SLL for surmounting this problem were investigated. The best results were obtained when specimens were first etched in either an ammonium bifluoride/sulfuric acid or an ammonium bifluoride solution, plated, and then heated at 700 0 C for 1 hour in a constrained condition. Machining threads in the Zircaloy-2 for the purpose of providing sites for mechanical interlocking of the plating also proved satisfactory

  7. NICKEL PLATING PROCESS

    Science.gov (United States)

    Hoover, T.B.; Zava, T.E.

    1959-05-12

    A simplified process is presented for plating nickel by the vapor decomposition of nickel carbonyl. In a preferred form of the invention a solid surface is nickel plated by subjecting the surface to contact with a mixture containing by volume approximately 20% nickel carbonyl vapor, 2% hydrogen sulfide and .l% water vapor or 1% oxygen and the remainder carbon dioxide at room temperature until the desired thickness of nickel is obtained. The advantage of this composition over others is that the normally explosive nickel carbonyl is greatly stabilized.

  8. Gneiss Macuira: tectonic evolution of Paleozoic metamorphic rocks of the Alta Guajira, Colombia

    International Nuclear Information System (INIS)

    Lopez I; A Julian; Zuluaga C; A, Carlos

    2012-01-01

    The Macuira Gneiss is a Paleozoic metamorphic unit that outcrops in the Simarua, Jarara and Macuira ranges, Alta Guajira. It is composed by a lithologies metamorphosed under amphibolite facies P-T conditions and consist of amphibolitic and quartz feldspathic gneisses, amphibolites, schists, pegmatites, calc-silicated rocks and marbles, with migmatization evidences in gneisses and amphibolites. Five foliations (S1-5) and three folding events (F1-3) were identified and interpreted as product of two metamorphic events, developed in a progressive barrovian metamorphic gradient of intermediate pressure with intermediate P-T ratio, interpreted as product of continental collision tectonics. This unit is important in understanding of the tectonic evolution of the Alta Guajira and Caribbean because it records different deformational phases pre-, syn- and post-migmatitic, that could be related with different tectonic episodes: the first associated with the collision between Laurasia and Gondwana (Alleghanian Orogeny - Late Paleozoic), and the second related with the Caribbean Plate evolution (Andean Orogeny - Meso-Cenozoic).

  9. Presentation of new tectonic map (and accompanying sections) of Trinidad and Tobago

    Energy Technology Data Exchange (ETDEWEB)

    Persad, K.M.

    1984-04-01

    The Geologic Map of Trinidad, compiled by H.G. Kugler and published in 1961, is currently out of print. While it is the most widely available geologic map, it is confined to onshore Trinidad. This map remains an important reference source, but there have been significant increases in our knowledge of Trindad and Tobago geology since its publication. In particular, there has been: (1) considerable geophysical work, on land and offshore, including 20,000 km (12,400 mi) of seismic lines; (2) approximately 1000 exploration and development wells drilled, including wells in the previously unexplored north and east coast of Trinidad; and (3) significant advances in our understanding of the tectonic evolution of the area, which has resulted largely from the development of the plate tectonic theory. The following items, which take into account many of these new data and concepts, have been compiled. (1) A geologic tectonic map of the entire territory of Trinidad and Tobago, at a scale of 1:200,000. Apart from the surface geology of the land areas, this map shows the major faults and their displacements and locations, total depths and status of exploration wells, and the positions of major petroleum fields. (2) Five accompanying geologic sections at the same scale. (3) A new stratigraphic correlation chart. These new compilations attempt to fill the gap in the published literature on the petroleum geology of Trinidad and Tobago.

  10. Public regulations towards a tectonic architecture

    DEFF Research Database (Denmark)

    Schmidt, Anne Marie Due

    2006-01-01

    Public regulations can support tectonic architecture by changes to the tendering system, supporting new organizational structures of the building industry in public building projects and suggesting a focus on innovation through increased research and development activity. The Danish state......'s activities has primarily been to support the optimization of the building process through ‘trimmed building’ and ‘partnering’ that only takes the immediate economic benefits of the changes to the building process into account and as such has no measures for architectural quality. The public initiatives so...... are happening very slowly which is understandable when there is no economic incitement for the industry to change. A change of these public regulations from sticks to carrots could create the economic incitement for the building industry to create tectonic architecture and thereby develop the building industry...

  11. John F. Dewey—Tectonics Editor

    Science.gov (United States)

    Richman, Barbara T.

    ‘I want the journal to acquire a reputation for very rapid, fair, and accurate reviewing,’ asserted John F. Dewey, editor-in-chief of AGU's newest journal, Tectonics. Dewey said that he will rule the bimonthly, which will begin publication in February, ‘with a bit of a rod of iron’ to ensure that Tectonics is ‘where only original and important papers are published.’‘I'm going to be very strict with reviewers,’ Dewey explained in his quick British clip. ‘If the review does not come back to me within 10 days to 2 weeks, I'll review the paper myself. I'm also going to have a system whereby, if a paper needs major surgery after being refereed, it will be rejected. Papers will have to be in virtually publishable condition before they are first submitted,’ he said.

  12. Searching for the Lost Jurassic and Cretaceous Ocean Basins of the Circum-Arctic Linking Plate Models and Seismic Tomography

    Science.gov (United States)

    Shephard, G. E.; Müller, R.

    2012-12-01

    The tectonic evolution of the circum-Arctic since the breakup of Pangea involves the opening and closing of ocean basins including the Oimyakon, Angayucham, South Anuyi, Amerasia and Eurasia basins. The time-dependent configurations and kinematic history of the basins, adjacent continental terranes, and subduction zones involved are not well understood, and many published tectonic models for particular regions are inconsistent with models for adjacent areas. The age, location, geometry and convergence rates of the subduction zones associated with these ancient ocean basins since at least the Late Jurassic have implications for mantle structure, which can be used as an additional constraint for building plate and plate boundary models. Here we integrate an analysis of both surface and deep mantle observations back to 200 Ma. Based on a digitized set of tectonic features with time-dependent rotational histories we present a refined plate model with topologically closed plate polygons for the circum-Arctic with particular focus on the northern Pacific, Siberian and Alaskan margins (Fig 1). We correlate the location, geometry and timing of subduction zones with associated seismic velocities anomalies from global P and S wave tomography models across different depths. We design a plate model that best matches slabs imaged in seismic tomography in an iterative fashion. This match depends on a combination of relative and absolute plate motions. Therefore we test two end-member absolute plate motion models, evaluating a paleomagnetic model and a model based on hotspot tracks and large igneous provinces. This method provides a novel approach to deciphering the Arctic tectonic history in a global context. Fig 1:Plate reconstruction at 200Ma and 140Ma, visualized using GPlates software. Present-day topography raster (ETOPO2) segmented into major tectonic elements of the circum-Arctic. Plate boundaries delineated in black and selected subduction and arc features labeled in

  13. Tectonic Thinking in Contemporary Industrialized Architecture

    Directory of Open Access Journals (Sweden)

    Anne Beim

    2013-12-01

    Full Text Available This paper argues for a new critical approach to the ways architectural design strategies are developing. Contemporary construction industry appears to evolve into highly specialized and optimized processes driven by industrialized manufacturing, therefore the role of the architect and the understanding of the architectural design process ought to be revised. The paper is based on the following underlying hypothesis: ‘Tectonic thinking – defined as a central attention towards the nature, the properties, and the application of building materials (construction and how this attention forms a creative force in building constructions, structural features and architectural design (construing – helps to identify and refine technology transfer in contemporary industrialized building construction’. (This definition of tectonic thinking forms part of a large, central research project: Towards a tectonic sustainable building practice, that is presently (2010- 2014 executed in collaboration between; The Royal Danish Academy of Fine Arts – School of Architecture, Aarhus School of Architecture, and The Danish Building Research Institute.Through various references from the construction industry, business theory and architectural practice the paper offers various analyses, comparisons and concrete design approaches. How architectural design processes and the tectonic design can benefit from Integrated Product Deliveries, mass-customization and Design for Disassembly is examined and discussed. The paper concludes by presenting a series of arguments that call for adaptable systems based on sufficient numbers of industrialized building products of high quality and a great variety of suppliers, and point at the need for optimizing our use of resources in order to reach sustainable solutions in architecture.

  14. Hot-spot tectonics on Io

    Science.gov (United States)

    Mcewen, A. S.

    1985-01-01

    The thesis is that extensional tectonics and low-angle detachment faults probably occur on Io in association with the hot spots. These processes may occur on a much shorter timescale on Ion than on Earth, so that Io could be a natural laboratory for the study of thermotectonics. Furthermore, studies of heat and detachment in crustal extension on Earth and the other terresrial planets (especially Venus and Mars) may provide analogs to processes on Io. The geology of Io is dominated by volcanism and hot spots, most likely the result of tidal heating. Hot spots cover 1 to 2% of Io's surface, radiating at temperatures typically from 200 to 400 K, and occasionally up to 700K. Heat loss from the largest hot spots on Io, such as Loki Patera, is about 300 times the heat loss from Yellowstone, so a tremendous quantity of energy is available for volcanic and tectonic work. Active volcanism on Io results in a resurfacing rate as high as 10 cm per year, yet many structural features are apparent on the surface. Therefore, the tectonics must be highly active.

  15. Tectonic evolution of Lavinia Planitia, Venus

    Science.gov (United States)

    Squyres, Steven W.; Frank, Sharon L.; Mcgill, George E.; Solomon, Sean C.

    1991-01-01

    High resolution radar images from the Magellan spacecraft have revealed the first details of the morphology of the Lavinia Planitia region of Venus. Lavinia is a broad lowland over 2000 km across, centered at about 45 deg S latitude, 345 deg E longitude. Herein, the tectonic evolution of Lavinia is discussed, and its possible relationship to processes operating in the planet's interior. The discussion is restricted to the region from 37.3 to 52.6 deg S latitude and from about 340 to 0 deg E longitude. One of the most interesting characteristics of Lavinia is that the entire region possesses a regional tectonic framework of striking regularity. Lavinia is also transected by a complex pattern of belts of intense tectonic deformation known as ridge belts. Despite the gross topographic similarity of all of the ridge belts in Lavinia, they exhibit two rather distinct styles of near surface deformation. One is composed of sets of broad, arch-like ridges rising above the surrounding plains. In the other type, obvious fold-like ridges are rare to absent in the radar images. Both type show evidence for small amounts of shear distributed across the belts.

  16. Mesozoic to Cenozoic tectonic transition process in Zhanhua Sag, Bohai Bay Basin, East China

    Science.gov (United States)

    Cheng, Yanjun; Wu, Zhiping; Lu, Shunan; Li, Xu; Lin, Chengyan; Huang, Zheng; Su, Wen; Jiang, Chao; Wang, Shouye

    2018-04-01

    The Zhanhua sag is part of the Bohai Bay intracontinental basin system that has developed since the Mesozoic in East China. The timing of this basin system coincides with the final assembly of East Asia and the development of Western Pacific-type plate margin. Here we use 3-D seismic and core log data to investigate the evolution of this basin and discuss its broad tectonic settings. Our new structural study of Zhanhua sag suggests that there are four major tectonic transitions occurred in the Bohai Bay Basin during Mesozoic and Cenozoic: (1) The first tectonic transition was from stable Craton to thrusting during the Triassic, mainly caused by the South China Block's subduction northward beneath the North China Block, which induced the formation of the NW-striking thrust faults. (2) The second tectonic transition was mainly characterized by a change from compression to extension, which can be further divided into two-stages. At the first stage, two episodes of NW-SE shortening occurred in East Asia during Early-Middle Jurassic and Late Jurassic-earliest Cretaceous, respectively. At the second stage, the extension and left-lateral shearing took place during Early Cretaceous while compression occurred during Late Cretaceous. The NW-striking thrust faults changed to normal faults and the NNE-striking left-lateral strike-slip faults started to influence the eastern part of the basin. (3) The third transition occurred when the NW-SE extension and NNE-striking right-lateral shearing started to form during Paleogene, and the peak deformation happen around 40 Ma due to the change of the subduction direction of Pacific Plate relative to Eurasia Plate. The NE-striking normal faults are the main structure, and the pre-existing NNE-striking strike-slip faults changed from left-lateral to right-lateral. (4) The fourth transition saw the regional subsidence during Neogene, which was probably caused by the India-Asia "Hard collision" between 25 and 20 Ma.

  17. The influence of mantle refertilisation on the formation of TTGs in a plume-lid tectonics setting

    Science.gov (United States)

    Fischer, R.; Gerya, T.

    2017-12-01

    Higher amounts of radiogenic elements and leftover primordial heat in the early Earth both contribute to the increased temperature in the Earth's interior and it is mainly this increased mantle potential temperature that controls the dynamics of the crust and upper mantle and the predominant style of tectonics in the Early Earth. The increased upper mantle temperature precludes the modern plate tectonics regime and stabilizes another type of global tectonics often called plume-lid tectonics (Fischer and Gerya, 2016) or 'plutonic squishy lid' tectonics(Rozel et al., 2017). Plume-lid tectonics is dominated by intrusive mantle-derived magmatism which results in a thickening of the overlaying crust. The overthickened basaltic crust is transformed into eclogite and episodically recycled back into the mantle. Melt extraction from hydrated partially molten basaltic crust leads to the production of primordial tonalite-trondhjemite-granodiorite (TTG) continental crust. TTGs make up over half of the Archean crust and can be classied into low-, medium- and high-pressure types (Moyen, 2011). Field studies show that the three different types (low-, medium- and high-pressure) appear in a ratio of 20%, 60% and 20% (Moyen, 2011). Numerical models of plume-lid tectonics generally agree very well with these values (Rozel et al., 2017) but also show that the ratio between the three different TTG types varies greatly during the two phases of the plume-lid tectonics cycle: growth phase and overturn phase. Melt productivity of the mantle decreases rapidly after removal of the garnet and clinopyroxene components. Addition of new garnet and clinopyroxene-rich material into the harzburgitic residue should lead to a refertilised lherzolite which could potentially yield new melt (Bédard, 2006). Mixing of eclogite drips back into the mantle can lead to the geochemical refertilisation of already depleted mantle and allow for further extraction of melt (Bédard, 2006). We will explore this

  18. Nuclear reactor alignment plate configuration

    Energy Technology Data Exchange (ETDEWEB)

    Altman, David A; Forsyth, David R; Smith, Richard E; Singleton, Norman R

    2014-01-28

    An alignment plate that is attached to a core barrel of a pressurized water reactor and fits within slots within a top plate of a lower core shroud and upper core plate to maintain lateral alignment of the reactor internals. The alignment plate is connected to the core barrel through two vertically-spaced dowel pins that extend from the outside surface of the core barrel through a reinforcement pad and into corresponding holes in the alignment plate. Additionally, threaded fasteners are inserted around the perimeter of the reinforcement pad and into the alignment plate to further secure the alignment plate to the core barrel. A fillet weld also is deposited around the perimeter of the reinforcement pad. To accomodate thermal growth between the alignment plate and the core barrel, a gap is left above, below and at both sides of one of the dowel pins in the alignment plate holes through with the dowel pins pass.

  19. Create Your Plate

    Medline Plus

    Full Text Available ... 1 Type 2 About Us Online Community Meal Planning Sign In Search: Search More Sites Search ≡ Are ... Fitness Home Food MyFoodAdvisor Recipes Association Cookbook Recipes Planning Meals Diabetes Meal Plans Create Your Plate Gluten ...

  20. Create Your Plate

    Medline Plus

    Full Text Available ... Your Plate Meal Planning for Vegetarian Diets Gluten Free Diets Holiday Meal Planning Cook with Heart-Healthy Foods donate en -- A Future Without Diabetes - a-future-without-diabetes-2.html A Future Without Diabetes Donate towards research today and your gift will be matched. Donate ...

  1. Create Your Plate

    Medline Plus

    Full Text Available ... meal-planning, . In this section Food Planning Meals Diabetes Meal Plans and a Healthy Diet Create Your Plate Meal Planning for Vegetarian Diets Gluten Free Diets Holiday Meal Planning Cook with Heart-Healthy Foods donate en -- A Future Without Diabetes - a-future-without-diabetes-1.html A Future ...

  2. Create Your Plate

    Medline Plus

    Full Text Available ... Types of Activity Weight Loss Assess Your Lifestyle Getting Started Food Choices In My Community Home Find Your ... but changes the portion sizes so you are getting larger portions of ... seven steps to get started: Using your dinner plate, put a line down ...

  3. Create Your Plate

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    Full Text Available ... Create Your Plate is a simple and effective way to manage your blood glucose levels and lose weight. With ... for Donations - ways-to-give-201710-hotelscom.html Ways to Give ... to help prevent and manage diabetes. Ask the Experts: Learn to Live Well ...

  4. Create Your Plate

    Medline Plus

    Full Text Available ... meal-planning, . In this section Food Planning Meals Diabetes Meal Plans and a Healthy Diet Create Your Plate Meal Planning for Vegetarian Diets Gluten Free Diets Holiday Meal Planning Cook with Heart-Healthy Foods donate en -- A Future Without Diabetes - a-future-without-diabetes-2.html A Future ...

  5. Create Your Plate

    Medline Plus

    Full Text Available ... Type 1 Type 2 About Us Online Community Meal Planning Sign In Search: Search More Sites Search ≡ ... Home Food MyFoodAdvisor Recipes Association Cookbook Recipes Planning Meals Diabetes Meal Plans Create Your Plate Gluten Free ...

  6. Create Your Plate

    Medline Plus

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  7. Create Your Plate

    Medline Plus

    Full Text Available ... tax-deductible gift today can fund critical diabetes research and support vital diabetes education services that improve the ... way to manage your blood glucose levels and lose weight. With this method, you fill your plate with more non-starchy ...

  8. Plate girders under bending

    NARCIS (Netherlands)

    Abspoel, R.; Dubina, D.; Ungureanu, V.

    2016-01-01

    In a material economy driven plate girder design, the lever arm between the flanges will increase. This leads to higher stiffness and bending moment resistance, but also to an in-crease of the web slenderness. This means that high strength steels can be used leading to a large reduction of the steel

  9. Teaching Plate Tectonic Concepts using GeoMapApp Learning Activities

    Science.gov (United States)

    Goodwillie, A. M.; Kluge, S.

    2012-12-01

    GeoMapApp Learning Activities ( http://serc.carleton.edu/geomapapp/collection.html ) can help educators to expose undergraduate students to a range of earth science concepts using high-quality data sets in an easy-to-use map-based interface called GeoMapApp. GeoMapApp Learning Activities require students to interact with and analyse research-quality geoscience data as a means to explore and enhance their understanding of underlying content and concepts. Each activity is freely available through the SERC-Carleton web site and offers step-by-step student instructions and answer sheets. Also provided are annotated educator versions of the worksheets that include teaching tips, additional content and suggestions for further work. The activities can be used "off-the-shelf". Or, since the educator may require flexibility to tailor the activities, the documents are provided in Word format for easy modification. Examples of activities include one on the concept of seafloor spreading that requires students to analyse global seafloor crustal age data to calculate spreading rates in different ocean basins. Another activity has students explore hot spots using radiometric age dating of rocks along the Hawaiian-Emperor seamount chain. A third focusses upon the interactive use of contours and profiles to help students visualise 3-D topography on 2-D computer screens. A fourth activity provides a study of mass wasting as revealed through geomorphological evidence. The step-by-step instructions and guided inquiry approach reduce the need for teacher intervention whilst boosting the time that students can spend on productive exploration and learning. The activities can be used, for example, in a classroom lab with the educator present and as self-paced assignments in an out-of-class setting. GeoMapApp Learning Activities are funded through the NSF GeoEd program and are aimed at students in the introductory undergraduate, community college and high school levels. The activities are based upon GeoMapApp (http://www.geomapapp.org), a free map-based data exploration and visualisation tool that allows students to access a wide range of geoscience data in a virtual lab-like environment.

  10. Plate tectonics, seaways and climate in the historical biogeography of mammals

    Directory of Open Access Journals (Sweden)

    C Barry Cox

    2000-08-01

    Full Text Available The marsupial and placental mammals originated at a time when the pattern of geographical barriers (oceans, shallow seas and mountains was very different from that of today, and climates were warmer. The sequence of changes in these barriers, and their effects on the dispersal of the mammal families and on the faunas of mammals in the different continents, are reviewed. The mammal fauna of South America changed greatly in the Pliocene/Pleistocene, when the newly-complete Panama Isthmus allowed the North American fauna to enter the continent and replace most of the former South American mammal families. Marsupial, but not placental, mammals reached Australia via Antarctica before Australia became isolated, while rats and bats are the only placentals that dispersed naturally from Asia to Australia in the late Cenozoic. Little is known of the early history of the mammal fauna of India. A few mammal families reached Madagascar from Africa in the early Cenozoic over a chain of islands. Africa was isolated for much of the early Cenozoic, though some groups did succeed in entering from Europe. Before the climate cooled in the mid-Cenozoic, the mammal faunas of the Northern Hemisphere were much richer than those of today.

  11. 3D movies for teaching seafloor bathymetry, plate tectonics, and ocean circulation in large undergraduate classes

    Science.gov (United States)

    Peterson, C. D.; Lisiecki, L. E.; Gebbie, G.; Hamann, B.; Kellogg, L. H.; Kreylos, O.; Kronenberger, M.; Spero, H. J.; Streletz, G. J.; Weber, C.

    2015-12-01

    Geologic problems and datasets are often 3D or 4D in nature, yet projected onto a 2D surface such as a piece of paper or a projection screen. Reducing the dimensionality of data forces the reader to "fill in" that collapsed dimension in their minds, creating a cognitive challenge for the reader, especially new learners. Scientists and students can visualize and manipulate 3D datasets using the virtual reality software developed for the immersive, real-time interactive 3D environment at the KeckCAVES at UC Davis. The 3DVisualizer software (Billen et al., 2008) can also operate on a desktop machine to produce interactive 3D maps of earthquake epicenter locations and 3D bathymetric maps of the seafloor. With 3D projections of seafloor bathymetry and ocean circulation proxy datasets in a virtual reality environment, we can create visualizations of carbon isotope (δ13C) records for academic research and to aid in demonstrating thermohaline circulation in the classroom. Additionally, 3D visualization of seafloor bathymetry allows students to see features of seafloor most people cannot observe first-hand. To enhance lessons on mid-ocean ridges and ocean basin genesis, we have created movies of seafloor bathymetry for a large-enrollment undergraduate-level class, Introduction to Oceanography. In the past four quarters, students have enjoyed watching 3D movies, and in the fall quarter (2015), we will assess how well 3D movies enhance learning. The class will be split into two groups, one who learns about the Mid-Atlantic Ridge from diagrams and lecture, and the other who learns with a supplemental 3D visualization. Both groups will be asked "what does the seafloor look like?" before and after the Mid-Atlantic Ridge lesson. Then the whole class will watch the 3D movie and respond to an additional question, "did the 3D visualization enhance your understanding of the Mid-Atlantic Ridge?" with the opportunity to further elaborate on the effectiveness of the visualization.

  12. Paleogene plate tectonic evolution of the Arabian and Eastern Somali basins

    Digital Repository Service at National Institute of Oceanography (India)

    Royer, J.-Y.; Chaubey, A.K.; Dyment, J.; Bhattacharya, G.C.; Srinivas, K.; Yatheesh, V.; Ramprasad, T.

    Universitaire Europeen de la Mer (IUEM), Place Copernic, 29280 Plouzane, France (e-mail: jyroyer@univ-brest.fr) 2 Geological Oceanography Division, National Institute of Oceanography (NIO), Dona Paula, Goa 403 004, India Abstract: We review previous models... 'ocean Indien: cinematique Inde-Afrique. These de Doctorat, Universite Denis Diderot (Paris 7), Paris. DYMENT, J. 1991. Structure et evolution de la litho- sphe're oceanique dans I'ocean Indien: apport des anomalies magnetiques. These de Doctorat, Univcr...

  13. A Virtual Tour of Plate Tectonics: Using Google Earth for Inquiry Investigations

    Science.gov (United States)

    Mulvey, Bridget; Bell, Randy

    2012-01-01

    Google Earth is an exciting way to engage students in scientific inquiry--the foundation of science education standards and reforms. The National Science Education Standards identify inquiry as an active process that incorporates questioning, gathering and analyzing data, and thinking critically about the interplay of evidence and explanations.…

  14. Reducing risk where tectonic plates collide—U.S. Geological Survey subduction zone science plan

    Science.gov (United States)

    Gomberg, Joan S.; Ludwig, Kristin A.; Bekins, Barbara; Brocher, Thomas M.; Brock, John C.; Brothers, Daniel; Chaytor, Jason D.; Frankel, Arthur; Geist, Eric L.; Haney, Matt; Hickman, Stephen H.; Leith, William S.; Roeloffs, Evelyn A.; Schulz, William H.; Sisson, Thomas W.; Wallace, Kristi; Watt, Janet; Wein, Anne M.

    2017-06-19

    The U.S. Geological Survey (USGS) serves the Nation by providing reliable scientific information and tools to build resilience in communities exposed to subduction zone earthquakes, tsunamis, landslides, and volcanic eruptions. Improving the application of USGS science to successfully reduce risk from these events relies on whole community efforts, with continuing partnerships among scientists and stakeholders, including researchers from universities, other government labs and private industry, land-use planners, engineers, policy-makers, emergency managers and responders, business owners, insurance providers, the media, and the general public.Motivated by recent technological advances and increased awareness of our growing vulnerability to subduction-zone hazards, the USGS is uniquely positioned to take a major step forward in the science it conducts and products it provides, building on its tradition of using long-term monitoring and research to develop effective products for hazard mitigation. This science plan provides a blueprint both for prioritizing USGS science activities and for delineating USGS interests and potential participation in subduction zone science supported by its partners.The activities in this plan address many USGS stakeholder needs:High-fidelity tools and user-tailored information that facilitate increasingly more targeted, neighborhood-scale decisions to mitigate risks more cost-effectively and ensure post-event operability. Such tools may include maps, tables, and simulated earthquake ground-motion records conveying shaking intensity and frequency. These facilitate the prioritization of retrofitting of vulnerable infrastructure;Information to guide local land-use and response planning to minimize development in likely hazardous zones (for example, databases, maps, and scenario documents to guide evacuation route planning in communities near volcanoes, along coastlines vulnerable to tsunamis, and built on landslide-prone terrain);New tools to assess the potential for cascading hazards, such as landslides, tsunamis, coastal changes, and flooding caused by earthquakes or volcanic eruptions;Geospatial models of permanent, widespread land- and sea-level changes that may occur in the immediate aftermath of great (M ≥8.0) subduction zone earthquakes;Strong partnerships between scientists and public safety providers for effective decision making during periods of elevated hazard and risk;Accurate forecasts of far-reaching hazards (for example, ash clouds, tsunamis) to avert catastrophes and unnecessary disruptions in air and sea transportation;Aftershock forecasts to guide decisions about when and where to re-enter, repair, or rebuild buildings and infrastructure, for all types of subduction zone earthquakes.

  15. It's "Your" Fault!: An Investigation into Earthquakes, Plate Tectonics, and Geologic Time

    Science.gov (United States)

    Clary, Renee; Wandersee, James

    2011-01-01

    Earthquakes "have" been in the news of late--from the disastrous 2010 Haitian temblor that killed more than 300,000 people to the March 2011 earthquake and devastating tsunami in Honshu, Japan, to the unexpected August 2011 earthquake in Mineral, Virginia, felt from Alabama to Maine and as far west as Illinois. As expected, these events…

  16. Surveys on environmental tectonics. Special volume.

    NARCIS (Netherlands)

    Cloetingh, S.A.P.L.; Cornu, T.

    2005-01-01

    Until now, research on neotectonics and related seismicity has mostly focused on active plate boundaries characterized by generally high earthquake activity. Current seismic hazard estimates for intraplate areas are commonly based on probabilistic analyses of historical and instrumental earthquake

  17. Subducting an old subduction zone sideways provides insights into what controls plate coupling

    Science.gov (United States)

    Reyners, Martin; Eberhart-Phillips, Donna; Bannister, Stephen

    2017-05-01

    The Hikurangi Plateau has had two episodes of subduction beneath New Zealand - firstly at ca. 100 Ma during north-south convergence with Gondwana, and currently during east-west convergence between the Pacific and Australian plates. As a result of this ninety-degree change in convergence direction, an old subduction zone is now being subducted sideways, and the tectonic history of the subducted plate varies dramatically along the strike of the Hikurangi Margin. Here we identify the location of the underplated Hikurangi Plateau along the shallow part of the Hikurangi Margin, using results from both relocated seismicity and seismic tomography. Next we decipher the tectonic history of the plateau along strike, particularly in terms of the hydration state of the plateau, and the nature of any sedimentary rock units capping the plateau. We then use this information to understand plate coupling at two scales: on the large scale, the southward transition from typical subduction in the North Island to continental collision in the South Island; and at a smaller scale, the strong lateral change from a high deficit in slip rate at the plate interface in the southern North Island to a low deficit in slip rate in the northeastern North Island. We find that the southward transition from subduction to continental collision is controlled by the plateau being more dehydrated to the south, as a result of being more deeply subducted at the Gondwana margin. The southward transition from localized slip at the plate interface to distributed upper plate deformation with no active plate interface occurs in Cook Strait and is relatively sharp. The high deficit in slip rate at the plate interface in the southern North Island is likely due to a relatively smooth plate interface from sedimentary rocks capping the Hikurangi Plateau, an impermeable terrane in the overlying plate, and the hydrated plateau acting in concert to produce an interseismically sealed plate interface. Further northeast

  18. Plate motions and deformations from geologic and geodetic data

    Science.gov (United States)

    Jordan, T. H.

    1986-06-01

    Research effort on behalf of the Crustal Dynamics Project focused on the development of methodologies suitable for the analysis of space-geodetic data sets for the estimation of crustal motions, in conjunction with results derived from land-based geodetic data, neo-tectonic studies, and other geophysical data. These methodologies were used to provide estimates of both global plate motions and intraplate deformation in the western U.S. Results from the satellite ranging experiment for the rate of change of the baseline length between San Diego and Quincy, California indicated that relative motion between the North American and Pacific plates over the course of the observing period during 1972 to 1982 were consistent with estimates calculated from geologic data averaged over the past few million years. This result, when combined with other kinematic constraints on western U.S. deformation derived from land-based geodesy, neo-tectonic studies, and other geophysical data, places limits on the possible extension of the Basin and Range province, and implies significant deformation is occurring west of the San Andreas fault. A new methodology was developed to analyze vector-position space-geodetic data to provide estimates of relative vector motions of the observing sites. The algorithm is suitable for the reduction of large, inhomogeneous data sets, and takes into account the full position covariances, errors due to poorly resolved Earth orientation parameters and vertical positions, and reduces baises due to inhomogeneous sampling of the data. This methodology was applied to the problem of estimating the rate-scaling parameter of a global plate tectonic model using satellite laser ranging observations over a five-year interval. The results indicate that the mean rate of global plate motions for that interval are consistent with those averaged over several million years, and are not consistent with quiescent or greatly accelerated plate motions. This methodology was also

  19. Evolution of the Mariana Convergent Plate Margin System

    Science.gov (United States)

    Fryer, Patricia

    1996-02-01

    The Mariana convergent plate margin system of the western Pacific provides opportunities for studying the tectonic and geochemical processes of intraoceanic plate subduction without the added complexities of continental geology. The system's relative geologic simplicity and the well-exposed sections of lithosphere in each of its tectonic provinces permit in situ examination of processes critical to understanding subduction tectonics. Its general history provides analogs to ancient convergent margin terranes exposed on land and helps to explain the chemical mass balance in convergent plate margins. The Mariana convergent margin's long history of sequential formation of volcanic arcs and extensional back arc basins has created a series of volcanic arcs at the eastern edge of the Philippine Sea plate. The trenchward edge of the overriding plate has a relatively sparse sediment cover. Rocks outcropping on the trench's inner slope are typical of the early formed suprasubduction zone's lithosphere and have been subjected to various processes related to its tectonic history. Pervasive forearc faulting has exposed crust and upper mantle lithosphere. Many large serpentinized peridotite seamounts are within 100 km of the trench axis. From these we can learn the history of regional metamorphism and observe and sample active venting of slab fluids. Ocean drilling recovered suprasubduction zone lava sequences erupted since the Eocene that suggest that the forearc region remains volcanologically dynamic. Seismic studies and seafloor mapping show evidence of deformation throughout forearc evolution. Large portions of uplifted southern forearc are exposed at the larger islands. Active volcanoes at the base of the eastern boundary fault of the Mariana Trough vary in size and composition along strike and record regional differences in source composition. Their locations along strike of the arc are controlled in part by cross-arc structures that also facilitate formation of submarine

  20. Late Quaternary river channel migrations of the Kura River in Transcaucasia - tectonic versus climatic causes

    Science.gov (United States)

    von Suchodoletz, Hans; Gärtner, Andreas; Hoth, Silvan; Umlauft, Josefine; Godoladze, Tea; Faust, Dominik

    2015-04-01

    Large-scale river channel migrations either in the form of avulsions or combing, i.e. progressive lateral migrations, are global phenomena during the Late Quaternary. Such channel migrations were triggered by tectonics, climate change, human activity or a combination of those factors. River channel migrations have the potential to cause significant human and economic losses. Thus, a more thorough knowledge about underlying causes and process rates is essential. Furthermore, such studies will elucidate the sensitivity or robustness of rivers to different external and internal forcing-agents, i.e. they help to identify the dominant drivers of regional landscape evolution. The Caucasus region is part of the active collision zone between the Africa-Arabian and the Eurasian plates, and is characterized by high current tectonic activity. Furthermore, significant environmental changes took place during the Late Quaternary, i.e. the shrinking or even disappearance of glaciers in the Greater and Lesser Caucasus or fundamental changes of the vegetation cover varying between woodland and grassland-dominated vegetation. The Kura River is the main gaining stream of the Transcaucasian Depression located between the Greater Caucasus Mountains in the north and the Lesser Caucasus Mountains in the south, and receives several tributaries from both mountain ranges. This study focusses on the middle course of the Kura River in eastern Georgia, SE of the city of Tbilisi. Integration of fluvial geomorphology, geochronology, heavy mineral analyses and seismo-tectonic analyses demonstrates that this part of the Kura River underwent large-scale channel migrations up to >10 km during Late Pleistocene and Holocene. It is interpreted that these movements followed both tectonic and climatic triggers: Whereas SW-ward migrations were caused by tectonic uplift in and SW-directed advance of the Kura fold and thrust belt as part of the Greater Caucasus, NE-ward migrations occurred during cold

  1. The polyphased tectonic evolution of the Anegada Passage in the northern Lesser Antilles subduction zone

    Science.gov (United States)

    Laurencin, M.; Marcaillou, B.; Graindorge, D.; Klingelhoefer, F.; Lallemand, S.; Laigle, M.; Lebrun, J.-F.

    2017-05-01

    The influence of the highly oblique plate convergence at the northern Lesser Antilles onto the margin strain partitioning and deformation pattern, although frequently invoked, has never been clearly imaged. The Anegada Passage is a set of basins and deep valleys, regularly related to the southern boundary of the Puerto Rico-Virgin Islands (PRVI) microplate. Despite the publications of various tectonic models mostly based on bathymetric data, the tectonic origin and deformation of this Passage remains unconstrained in the absence of deep structure imaging. During cruises Antithesis 1 and 3 (2013-2016), we recorded the first deep multichannel seismic images and new multibeam data in the northern Lesser Antilles margin segment in order to shed a new light on the structure and tectonic pattern of the Anegada Passage. We image the northeastern extent of the Anegada Passage, from the Sombrero Basin to the Lesser Antilles margin front. Our results reveal that this northeastern segment is an EW trending left-stepping en échelon strike-slip system that consists of the Sombrero and Malliwana pull-apart basins, the Malliwana and Anguilla left-lateral faults, and the NE-SW compressional restraining bend at the Malliwana Hill. Reviewing the structure of the Anegada Passage, from the south of Puerto Rico to the Lesser Antilles margin front, reveals a polyphased tectonic history. The Anegada Passage is formed by a NW-SE extension, possibly related to the rotation or escape of PRVI block due to collision of the Bahamas Bank. Currently, it is deformed by an active WNW-ESE strike-slip deformation associated to the shear component of the strain partitioning resulting from the subduction obliquity.

  2. Geophysical Data (Gravity and Magnetic) from the Area Between Adana, Kahramanmaras and Hatay in the Eastern Mediterranean Region: Tectonic Implications

    Science.gov (United States)

    Over, Semir; Akin, Ugur; Sen, Rahime

    2018-01-01

    The gravity and magnetic maps of the area between Adana-Kahramanmaras-Hatay provinces were produced from a compilation of data gathered during the period between 1973 and 1989. Reduced to the pole (RTP) and pseudo-gravity transformation (PGT) methods were applied to the magnetic data, while derivative ratio (DR) processing was applied to both gravity and magnetic data, respectively. Bouguer, RTP and PGT maps show the image of a buried structure corresponding to ophiolites under undifferentiated Quaternary deposits in the Adana depression and Iskenderun Gulf. DR maps show two important faults which reflect the tectonic framework in the study area: (1) the Karatas-Osmaniye Fault extending from Osmaniye to Karatas in the south between Adana and Iskenderun depressions and (2) Amanos Fault (southern part of East Anatolian Fault) in the Hatay region running southward from Turkoglu to Amik Basin along Amanos Mountain forming the actual plate boundary between the Anatolian block (part of Eurasian plate) and Arabian plate.

  3. Tectonic implications of Mesozoic magmatism to initiation of Cenozoic basin development within the passive South China Sea margin

    Science.gov (United States)

    Mai, Hue Anh; Chan, Yu Lu; Yeh, Meng Wan; Lee, Tung Yi

    2018-04-01

    The South China Sea (SCS) is one of the classical example of a non-volcanic passive margin situated within three tectonic plates of the Eurasian, Indo-Australian and Philippine Sea plate. The development of SCS resulted from interaction of various types of plate boundaries, and complex tectonic assemblage of micro blocks and accretionary prisms. Numerous models were proposed for the formation of SCS, yet none can fully satisfy different aspects of tectonic forces. Temporal and geographical reconstruction of Cretaceous and Cenozoic magmatism with the isochrones of major basins was conducted. Our reconstruction indicated the SE margin of Asia had gone through two crustal thinning events. The sites for rifting development are controlled by localized thermal weakening of magmatism. NW-SE extension setting during Late Cretaceous revealed by magmatism distribution and sedimentary basins allow us to allocate the retreated subduction of Pacific plate to the cause of first crustal thinning event. A magmatic gap between 75 and 65 Ma prior to the initiation of first basin rifting suggested a significant modification of geodynamic setting occurred. The Tainan basin, Pearl River Mouth basin, and Liyue basins started to develop since 65 Ma where the youngest Late Cretaceous magmatism concentrated. Sporadic bimodal volcanism between 65 and 40 Ma indicates further continental extension prior to the opening of SCS. The E-W extension of Malay basin and West Natuna began since late Eocene followed by N-S rifting of SCS as Neotethys subducted. The SCS ridge developed between Pearl River Mouth basin and Liyue basin where 40 Ma volcanic activities concentrated. The interaction of two continental stretching events by Pacific followed by Neotethys subduction with localized magmatic thermal weakening is the cause for the non-volcanic nature of SCS.

  4. Tectonic resemblance of the Indian Platform, Pakistan with the Moesian Platform, Romania and strategy for exploration of hydrocarbons

    International Nuclear Information System (INIS)

    Memon, A.D.

    1994-01-01

    There is a remarkable tectonic resemblance between the indian Platform (Pakistan) and the Moesian Platform (Romania). As viewed in global tectonic perspective Moeslan and Indian Plates have played important role in Alpine Himalayan Orogeny; Moesian and Indian Platforms are extension of these respective plates. Characteristics features of both the platforms are block faulting which has effected not only the general tectonic framework but has also played important role in oil accumulation. Main producing rocks in the Moesian platform are Jurassic sandstones and cretaceous limestones while in the indian platform cretaceous sandstones are important reservoirs. The average geothermal gradient in the indian platform is 2.45 C/100m with the higher gradients in the central gas producing region. Geothermal gradients in the Moesian platform have an average value of 3 C/100m with higher gradients in the northern in the northern part. Some of the producing structures in both the platforms are remarkably similar, traps associated with normal faults are very important. Extensive exploration carried in the Moesian Platform makes it very important oil producing region of Romania. After the discovery of oil lower Sindh, serious exploration is being carried in the Indian platform. The paper deals with the similarities between these two important platforms. In the light of the studies of the Moesian platform, strategies or exploration of oil and gas in the Indian Platform are suggested. (author)

  5. Tectonic map of the Circum-Pacific region, Pacific basin sheet

    Science.gov (United States)

    Scheibner, E.; Moore, G.W.; Drummond, K.J.; Dalziel, Corvalan Q.J.; Moritani, T.; Teraoka, Y.; Sato, T.; Craddock, C.

    2013-01-01

    Circum-Pacific Map Project: The Circum-Pacific Map Project was a cooperative international effort designed to show the relationship of known energy and mineral resources to the major geologic features of the Pacific basin and surrounding continental areas. Available geologic, mineral, and energy-resource data are being complemented by new, project-developed data sets such as magnetic lineations, seafloor mineral deposits, and seafloor sediment. Earth scientists representing some 180 organizations from more than 40 Pacific-region countries are involved in this work. Six overlapping equal-area regional maps at a scale of 1:10,000,000 form the cartographic base for the project: the four Circum-Pacific Quadrants (Northwest, Southwest, Southeast, and Northeast), and the Antarctic and Arctic Sheets. There is also a Pacific Basin Sheet at a scale of 1:17,000,000. The Base Map Series and the Geographic Series (published from 1977 to 1990), the Plate-Tectonic Series (published in 1981 and 1982), the Geodynamic Series (published in 1984 and 1985), and the Geologic Series (published from 1984 to 1989) all include six map sheets. Other thematic map series in preparation include Mineral-Resources, Energy-Resources and Tectonic Maps. Altogether, more than 50 map sheets are planned. The maps were prepared cooperatively by the Circum-Pacific Council for Energy and Mineral Resources and the U.S. Geological Survey and are available from the Branch of Distribution, U. S. Geological Survey, Box 25286, Federal Center, Denver, Colorado 80225, U.S.A. The Circum-Pacific Map Project is organized under six panels of geoscientists representing national earth-science organizations, universities, and natural-resource companies. The six panels correspond to the basic map areas. Current panel chairmen are Tomoyuki Moritani (Northwest Quadrant), R. Wally Johnson (Southwest Quadrant), Ian W.D. Dalziel (Antarctic Region), vacant. (Southeast Quadrant), Kenneth J. Drummond (Northeast Quadrant), and

  6. Role of tectonic inheritance in the instauration of Tunisian Atlassic fold-and-thrust belt: Case of Bouhedma - Boudouaou structures

    Science.gov (United States)

    Ghanmi, Mohamed Abdelhamid; Ghanmi, Mohamed; Aridhi, Sabri; Ben Salem, Mohamed Sadok; Zargouni, Fouad

    2016-07-01

    Tectonic inversion in the Bouhedma-Boudouaou Mountains was investigated through recent field work and seismic lines interpretation calibrated with petroleum well data. Located to the Central-Southern Atlas of Tunisia, this area signed shortened intra-continental fold-and-thrust belts. Two dissymmetric anticlines characterize Bouhedma - Boudouaou major fold. These structures show a strong virgation respectively from E-W to NNE-SSW as a response to the interference between both tectonic inversion and tectonic inheritance. This complex geometry is driven by Mesozoic rifting, which marked an extensional inherited regime. A set of late Triassic-Early Jurassic E-W and NW-SE normal faults dipping respectively to the North and to the East seems to widely affect the overall geodynamic evolution of this domain. They result in major thickness changes across the hanging wall and the footwall blocks in response with the rifting activity. Tectonic inversion is inferred from convergence between African and European plates since late Cretaceous. During Serravalian - Tortonian event, NW-SE trending paroxysm led to: 1) folding of pre-inversion and syn-inversion strata, 2) reactivation of pre-existing normal faults to reverse ones and 3) orogeny of the main structures with NE-SW and E-W trending. The compressional feature still remains active during Quaternary event (Post-Villafranchian) with N-S trending compression. Contraction during inversion generates folding and internal deformation as well as Fault-Propagation-Fold and folding related strike.

  7. The Role of a Weak Layer at the Base of an Oceanic Plate on Subduction Dynamics

    Science.gov (United States)

    Carluccio, R.; Moresi, L. N.; Kaus, B. J. P.

    2017-12-01

    Plate tectonics relies on the concept of an effectively rigid lithospheric lid moving over a weaker asthenosphere. In this model, the lithosphere asthenosphere boundary (LAB) is a first-order discontinuity that accommodates differential motion between tectonic plates and the underlying mantle. Recent seismic studies have revealed the existence of a low velocity and high electrical conductivity layer at the base of subducting tectonic plates. This thin layer has been interpreted as being weak and slightly buoyant and it has the potential to influence the dynamics of subducting plates. However, geodynamically, the role of a weak layer at the base of the lithosphere remains poorly studied, especially at subduction zones. Here, we use numerical models to investigate the first-order effects of a weak buoyant layer at the LAB on subduction dynamics. We employ both 2-D and 3-D models in which the slab and the mantle are either linear viscous or have a more realistic temperature-dependent, visco-elastic-plastic rheology and we vary the properties of the layer at the base of the oceanic lithosphere. Our results show that the presence of a weak layer affects the dynamics of plates, primarily by increasing the subduction speed and also influences the morphology of subducting slab. For moderate viscosity contrasts (viscosity contrasts (>1000), it can also change the morphology of the subduction itself and for thinner and more buoyant layers, the overall effect is reduced. The overall impact of this effects may depend on the effective contrast between the properties of the slab and the weak layer + mantle systems, and so, by the layer characteristics modelled such as its viscosity, density, thickness and rheology. In this study, we show and summarise this impact consistently with the recent seismological constraints and observations, for example, a pile-up of weak material in the bending zone of the subducting plate.

  8. A new GPS velocity field for the Pacific Plate - Part 1: constraints on plate motion, intraplate deformation, and the viscosity of Pacific basin asthenosphere

    Science.gov (United States)

    DeMets, C.; Márquez-Azúa, Bertha; Cabral-Cano, Enrique

    2014-12-01

    We combine new, well-determined GPS velocities from Clarion, Guadalupe and Socorro islands on young seafloor in the eastern Pacific basin with newly estimated velocities for 26 GPS sites from older seafloor in the central, western and southern parts of the Pacific Plate to test for deformation within the interior of the Pacific Plate and estimate the viscosity of the asthenosphere below the plate. Relative to a Pacific Plate reference frame defined from the velocities of the 26 GPS sites in other areas of the Pacific Plate, GPS sites on Clarion and Guadalupe islands in the eastern Pacific move 1.2 ± 0.6 mm yr-1 (1σ) towards S09°W ± 38° and 1.9 ± 0.3 mm yr-1 towards S19°E ± 10°, respectively. The two velocities, which are consistent within their 95 per cent uncertainties, both differ significantly from Pacific Plate motion. Transient volcanic deformation related to a 1993-1996 eruption of the Socorro Island shield volcano renders our GPS velocity from that island unreliable for the tectonic analysis although its motion is also southward like those of Clarion and Guadalupe islands. We test but reject the possibilities that drift of Earth's origin in ITRF2008 or unmodelled elastic offsets due to large-magnitude earthquakes around the Pacific rim since 1993 can be invoked to explain the apparent slow southward motions of Clarion and Guadalupe islands. Similarly, corrections to the Pacific Plate GPS velocity field for possible viscoelastic deformation triggered by large-magnitude earthquakes since 1950 also fail to explain the southward motions of the two islands. Viscoelastic models with prescribed asthenospheric viscosities lower than 1 × 1019 Pa s instead introduce statistically significant inconsistencies into the Pacific Plate velocity field, suggesting that the viscosity of the asthenosphere below the plate is higher than 1 × 1019 Pa s. Elastic deformation from locked Pacific-North America Plate boundary faults is also too small to explain the southward

  9. Framework for Tectonic Thinking, a Conceptual Tool of the Architect

    DEFF Research Database (Denmark)

    Garritzmann, Udo

    2017-01-01

    , supposedly right, meaning of tectonics, but several different meanings; nor do we attach a value judgement to any of the tectonic positions beforehand. The FTT will be developed in parallel in writing and in hand-drawn mappings. Research goal: The Framework for Tectonic Thinking will suggest a broadened......This paper is a contribution to the understanding of the term tectonics in the field of architectural design theory. It considers tectonic thinking as a ‘tool of the architect’ to analyse and interpret buildings from the past, to be operative in design practices of the present, and to trigger......: To answer the research question, this paper will develop an overarching Framework for Tectonic Thinking (FTT) by combining three different categories loadbearing construction, type of construction and constructive expression with the following oppositional poles as distinguishing criteria: loadbearing...

  10. Effect of plate shapes in orifice plate type flowmeters

    International Nuclear Information System (INIS)

    Moeller, S.V.

    1984-01-01

    The study of unusual plate shapes in orifice plate type flowmeters is presented, with a view to providing data for the substitution of the plate with one centered circular orifice in those applications where its use is not possible. For this purpose, six pairs of plates with different forms, with and without chamfered edges, were made and tested in a closed water loop. Results show that, generally, the use of chamfers improves the results and, in the case of perforated and slotlike orificed plates, the narrow-ness of the fluid passage tends to make unnecessary its use. (Author) [pt

  11. The concurrent emergence and causes of double volcanic hotspot tracks on the Pacific plate

    DEFF Research Database (Denmark)

    Jones, David T; Davies, D. R.; Campbell, I. H.

    2017-01-01

    Mantle plumes are buoyant upwellings of hot rock that transport heat from Earth's core to its surface, generating anomalous regions of volcanism that are not directly associated with plate tectonic processes. The best-studied example is the Hawaiian-Emperor chain, but the emergence of two sub......-parallel volcanic tracks along this chain, Loa and Kea, and the systematic geochemical differences between them have remained unexplained. Here we argue that the emergence of these tracks coincides with the appearance of other double volcanic tracks on the Pacific plate and a recent azimuthal change in the motion...... of the plate. We propose a three-part model that explains the evolution of Hawaiian double-track volcanism: first, mantle flow beneath the rapidly moving Pacific plate strongly tilts the Hawaiian plume and leads to lateral separation between high- and low-pressure melt source regions; second, the recent...

  12. Tectonic analysis of the Oklo deposit

    International Nuclear Information System (INIS)

    Gauthier-Lafaye, F.; Ruhland, M.; Weber, F.

    1975-01-01

    A large folded structure with a 40 0 incline and extending 500 m in the north-south direction has been uncovered at the Oklo mine. This structure has been analysed from the geometric and dynamic points of view in order to determine the possible role of tectonic activity in the creation of the uraniferous concentrations. Compression and extension zones which at certain points control the shape and arrangement of the lodes are associated with the structure. The natural reactors are situated in an extension zone where compartmentation and slippage, which explain the arrangement of the reactors, are observed

  13. Tectonic movements monitored in the Bohemian Massif

    Czech Academy of Sciences Publication Activity Database

    Košťák, Blahoslav; Mrlina, Jan; Stemberk, Josef; Chán, Bohumil

    2011-01-01

    Roč. 52, č. 1 (2011), s. 34-44 ISSN 0264-3707 R&D Projects: GA ČR GA205/09/2024; GA AV ČR IBS3012353; GA AV ČR IAA300120905; GA MŠk OC 625.10 Institutional research plan: CEZ:AV0Z30460519; CEZ:AV0Z30120515 Keywords : pressure pulse * tectonic displacement * earthquake micro swarm Subject RIV: DB - Geology ; Mineralogy Impact factor: 2.007, year: 2011

  14. The Nature of Tectonic Spatial Structures

    DEFF Research Database (Denmark)

    Carter, Adrian; Kirkegaard, Poul Henning

    2010-01-01

    Since earliest times mankind has sought inspiration from nature for our built structures. However until the dawn of the modern era in architecture and design, the true structural character of a building was invariably full y or partially encased in an ornamented cladding, of often stylised motifs...... particularly of Kenneth Frampton, this paper will argue that the direct inspiration of nature and the increasing use of advanced parametric digital design tools that replicate virtually instantaneously evolutionary processes results in structures that are not only elegant tectonically and in terms of economy...

  15. Seismo-electromagnetic phenomena in the western part of the Eurasia-Nubia plate boundary

    Directory of Open Access Journals (Sweden)

    H. G. Silva

    2011-01-01

    Full Text Available This paper presents a work that aims to monitor seismo-electromagnetic phenomena in the Western Part of the Eurasia-Nubia Plate Boundary. This region has a significant tectonic activity combined with relatively low electromagnetic noise levels, rendering high quality seismo-electromagnetic measurements possible. An overview of the seismicity of this region is presented and the research plan is discussed accordingly.

  16. Gravity and magnetic anomalies of the Cyprus arc and tectonic implications

    Science.gov (United States)

    Ergün, M.; Okay, S.; Sari, C.; Oral, E. Z.

    2003-04-01

    In present day, eastern Mediterranean is controlled by the collision of the African and Eurasian plates and displacements of Arabian, Anatolian and Aegean micro-plates. The boundary between African and Eurasian plates is delineated by the Hellenic arc and Pliny-Strabo trench in the west and the Cyprus arc and a diffuse fault system of the Eastern Anatolian Fault zone in the east. The available gravity and magnetic data from the easternmost Mediterranean allow to subdivide this basin into three provinces: the northeastern Mediterranean north of the Cyprus Arc; the Levant Basin south of the Cyprus Arc and east of the line that roughly continues the Suez rift trend toward the Gulf of Antalya, between Cyprus and Anaximander Mountains; and the Mediterranean Ridge, Herodotus Basin west of this line. High anomalies observed in Cyprus and the sea region at the south is prominent in the gravity data. The Bouguer gravity anomaly reaches its maximum values over Cyprus, where it is most probably caused by high dense Troodos ophiolites. The uplifted oceanic crust causes high Bouguer anomaly also seen in the vicinity of Eratosthenes Seamount. Another result obtained from gravity data is that the crust under Herodotos and Rhodes basins is somehow oceanic and Anaximander, Eratosthenes and Cyprus are continental fragments. There are no linear magnetic anomalies in the Mediterranean. But there are magnetic anomalies over the Eratosthenes seamount and as well as from Cyprus to the Antalya basin due to the ophiolitic bodies. In Cyprus, the last compressional deformations were defined near the Miocene/Pliocene boundary. The extensional deformation associated with the Antalya basin appears to be separated by a zone of the Florence rise and Anaximander Mountains affected by differential tectonic movements. Eratosthenes Seamount is a positive crustal feature in the process of collision with Cyprus along an active margin; there is clearly a potential tectonic relationship to the onland

  17. Marine Terrace Deposits along the Mediterranean Coast on the Southeastern Turkey and Their Implications for Tectonic Uplift and Sea Level Change

    Science.gov (United States)

    Tari, U.; Tüysüz, O.; Blackwell, B. A. B.; Genç, Ş. C.; Florentin, J. A.; Mahmud, Z.; Li, G. L.; Blickstein, J. I. B.; Skinner, A. R.

    2016-12-01

    Tectonic movements among the African, Arabian and Anatolian Plates have deformed the eastern Mediterranean. These movements caused transtensional opening of the NE-trending Antakya Graben since the late Pliocene. Tectonic uplift coupled with Quaternary sealevel fluctuations has produced several stacked marine terraces along the Mediterranean coasts on the graben. Here, marine terrace deposits that sit on both flanks of the graben at elevations between 3 and 175 m were dated using electron spin resonance (ESR) method in order to calculate uplift rates. The ESR ages range from 12 ka in late MIS 2 to 457 ka in MIS 9-11, but most of the terraces contain molluscs reworked from several earlier deposits due to successive tectonic movements and sealevel fluctuations. By dating in situ fossils, along the basal contacts of the marine terraces, uplift rates were calculated on both sides of the Antakya Graben. Results indicate that these deposits were mainly uplifted by local active faults rather than regional movements.

  18. Large plates and small blocks: The Variscan orogeny in the Bohemian Massif

    Science.gov (United States)

    Kroner, Uwe; Romer, Rolf L.

    2017-04-01

    The Bohemian Massif of the Central European Variscides consists of several late Proterozoic / early Paleozoic low-strain crustal units, namely the Bruno-Vistulian continental block of the Laurussian plate that is juxtaposed with the Tepla-Barrandian Unit and the Lausitz block of the Gondwana plate. These pre-Variscan low-strain units are separated by high-strain zones that contain the mid- and lower crustal record of the Variscan orogeny (400-300 Ma), with nappes reflecting successive subduction exhumation events, voluminous migmatites and a wide range of geochemically contrasting granites. Although the principal constraints are undisputed, there is no consensus regarding the general tectonics of this area. Here we present a plate tectonic model explaining the Bohemian Massif as an orogenic wedge with a Gondwana pro-wedge and a Laurussia retro-wedge area. The principal formation steps are as follows. Subduction of the oceanic crust of the Gondwana plate, i.e. the southern part of the Rheic Ocean eventually followed by continental subduction of the distal Peri-Gondwana shelf produced the early Devonian (U)HP complexes now exposed in the uppermost allochthonous units. The arrival of the Tepla-Barrandian Cadomian block initiates a flip of subduction polarity, leading to the complete closure of the Rheic Ocean in the late Devonian coeval with the exhumation of the early Variscan (U)HP units. Caused by the Lausitz block entering the plate boundary zone in the early Carboniferous, this early subduction accretion stage was followed by continent continent collision. The resulting orogenic wedge is characterized by an intra-continental subduction zone in the pro-wedge area superimposed by the crustal stack of early and mid-Variscan accreted units. Due to heating of the subducted slab in the mantle, the isothermal exhumation of this deeply buried continental crust caused HT-LP metamorphism during the final transpressional stage. Lateral extrusion tectonics coeval with the

  19. Plate Coupling and Strain Partitioning in the Northeastern Caribbean

    Science.gov (United States)

    Manaker, D.; Calais, E.; Jansma, P.; Mattioli, G.

    2006-12-01

    Major strike-slip faults commonly found on the margin of overriding plates in oblique subduction zone settings facilitate the partitioning of strain into trench-parallel and trench-normal tectonics. Their development has been proposed to be controlled by factors such as convergence obliquity, basal tractions, magnitude of slab-pull force, or strength of interplate coupling. In the northeastern Caribbean, the direction of GPS velocities and earthquake slip vectors suggests low coupling along the Puerto Rico and Lesser Antilles trenches, but strong coupling to the west along the Hispaniola margin, while the convergence obliquity remains constant. Coincidentally, large strike-slip faults in the overriding plate only develop in Hispaniola, which is also the locus of the largest historical subduction earthquakes in the Caribbean (M8.0, 1946-53 sequence). We investigate interplate coupling at the Caribbean-North American plate boundary using a model that allows for block rotations and elastic strain accumulation on partially coupled faults. Model parameters (block rotations and coupling on interplate faults) are derived from an inversion of earthquake slip vectors and new GPS data covering Haiti, the Dominican Republic, Puerto Rico and the Virgin Islands, and the Lesser Antilles. We find that intraplate coupling is high in the western half of the domain, coincident with the development of large and fast-slipping strike-slip faults in the upper plate that partition the Carribean/North America plate motion, but low in its eastern half, along the Puerto Rico and Lesser Antilles subductions, that show little to no strain partitioning. This suggests that strain partitioning occur only if interplate coupling is large enough to effectively transfer shear stresses to the overriding plate.

  20. Tectonic and erosion-driven uplift in the Gamburtsev Subglacial Mountains of East Antarctica

    Science.gov (United States)

    Ferraccioli, Fausto; Jordan, Tom; Watts, Tony; Bell, Robin; Jamieson, Stewart; Finn, Carol; Damaske, Detlef

    2014-05-01

    Understanding the mechanisms leading to intraplate mountain building remains a significant challenge in Earth Sciences compared to ranges formed along plate margins. The most enigmatic intraplate mountain range on Earth is the Gamburtsev Subglacial Mountains (GSM) located in the middle of the Precambrian East Antarctic Craton. During the International Polar Year, the AGAP project acquired 120,000 line km of new airborne geophysical data (Bell et al., 2011, Science) and seismological observations (Hansen et al., 2010, EPSL) across central East Antarctica. Models derived from these datasets provide new geophysical perspectives on crustal architecture and possible uplift mechanisms for the enigmatic GSM (Ferraccioli et al., 2011, Nature). The geophysical data define a 2,500-km-long Paleozoic to Mesozoic rift system in East Antarctica surrounding the GSM. A thick high-density lower crustal root is partially preserved beneath the range and has been interpreted as formed during the Proterozoic assembly of East Antarctica. Rifting could have triggered phase/density changes at deep crustal levels, perhaps restoring some of the latent root buoyancy, as well as causing rift-flank uplift. Permian rifting is well-established in the adjacent Lambert Rift, and was followed by Cretaceous strike-slip faulting and transtension associated with Gondwana break-up; this phase may have provided a more recent tectonic trigger for the initial uplift of the modern GSM. The Cretaceous rift-flank uplift model for the Gamburtsevs is appealing because it relates the initiation of intraplate mountain-building to large-scale geodynamic processes that led to the separation of Greater India from East Antarctica. It is also consistent with several geological and geophysical interpretations within the Lambert Rift. However, recent detrital thermochrology results from Oligocene-Quaternary sediments in Prydz Bay (Tochlin et al., 2012, G3) argue against the requirement for major Cretaceous rift

  1. Tectonic shortening and coeval volcanism during the Quaternary

    Indian Academy of Sciences (India)

    Japan Sea), is located on a convergent plate boundary along the subducting Pacific plate and the overriding North American plate. From a compilation and analysis of stratigraphy, radiometric age and data on erupted magma volumes, 176 ...

  2. Aspects of collision tectonics and intraplate deformation

    Energy Technology Data Exchange (ETDEWEB)

    Coward, M.P.

    1988-08-01

    Alpine collisional tectonics occurred episodically over the past 100 m.y., closing various small Tethyan basins and causing ripples of basin contraction and tectonic inversion across western Europe. Both at the Tethyan margin and in the smaller basins, deformation styles were controlled by existing fault geometries, in particular, (1) the position, dip, and detachment levels of the important bounding normal faults, (2) the locations of northwest-southwest trending lateral ramps/tear faults, which compartmentalize and tram-line the deformation, and (3) the distribution and thickness of Mesozoic postrift sediments. Collision began in the middle Cretaceous, with the closure of Ligurian and Valais basins and the associated reactivation of northwest-southeast strike-slip faults and small basins as far away as the Atlantic margin. This movement was associated with the earliest orogenic flysch deposits, the subduction of Tethyan ophiolites, and local A-type subduction and high-pressure metamorphism close to the Tethyan continental margins. Major crustal shortening occurred in southern Europe (Spain and southern France) in the Late Cretaceous-Paleogene associated with closure of Pyrenean basins, but in the Alps, the major shortening continued throughout the Neogene. Section restorations based on regional studies, linked to commercial and deep seismic data, indicate well over 100 km of crustal shortening in the western and central Alps, with subduction of lower European crust and lithospheric mantle beneath the southern Alps and the Po plain.

  3. Tectonics and magmatism of ultraslow spreading ridges

    Science.gov (United States)

    Dubinin, E. P.; Kokhan, A. V.; Sushchevskaya, N. M.

    2013-05-01

    The tectonics, structure-forming processes, and magmatism in rift zones of ultraslow spreading ridges are exemplified in the Reykjanes, Kolbeinsey, Mohns, Knipovich, Gakkel, and Southwest Indian ridges. The thermal state of the mantle, the thickness of the brittle lithospheric layer, and spreading obliquety are the most important factors that control the structural pattern of rift zones. For the Reykjanes and Kolbeinsey ridges, the following are crucial factors: variations in the crust thickness; relationships between the thicknesses of its brittle and ductile layers; width of the rift zone; increase in intensity of magma supply approaching the Iceland thermal anomaly; and spreading obliquety. For the Knipovich Ridge, these are its localization in the transitional zone between the Gakkel and Mohns ridges under conditions of shear and tensile stresses and multiple rearrangements of spreading; nonorthogonal spreading; and structural and compositional barrier of thick continental lithosphere at the Barents Sea shelf and Spitsbergen. The Mohns Ridge is characterized by oblique spreading under conditions of a thick cold lithosphere and narrow stable rift zone. The Gakkel and the Southwest Indian ridges are distinguished by the lowest spreading rate under the settings of the along-strike variations in heating of the mantle and of a variable spreading geometry. The intensity of endogenic structure-forming varies along the strike of the ridges. In addition to the prevalence of tectonic factors in the formation of the topography, magmatism and metamorphism locally play an important role.

  4. Active and recent strike-slip tectonics

    Science.gov (United States)

    Nur, Amos; Boccaletti, Mario

    An international workshop cosponsored by the Department of Geology, University of Florence, Italy and the Department of Geophysics, Stanford University, Stanford, Calif., was held in Florence, Italy, April 18-20, 1989,on the topic of active and recent strike-slip tectonics in the continental crust. Workshop participants from Turkey, Ethiopia, Israel, Greece, and various universities in Italy, Spain, West Germany, France, the United Kingdom, Brazil, and the United States reported on a broad range of studies involving strike-slip faulting in continental crustal setting. As it turned out, much of the work reported on involved aspects of strike-slip faulting that are only poorly understood, especially crustal deformation, which is distributed over a multiplicity of faults, or even fault domains.One of the rewarding aspects of this workshop was the diversity of geographic areas and geological settings covered by the reporters. The north and east Anatolian faults, the Dead Sea transform zone, western Turkey, north and central Greece, Malta, Sicily, southern Italy, the bethic Cordillera in southern Spain, Tunisia, Tibet and southwest China, offshore Brazil, Alaska, Nevada, and California. A recurring observation reported for all those areas was mixed mode faulting, i.e., the coterminous or sequential occurrence of strike-slip and normal faulting, or strike-slip and thrust, and in many instances also strikeslip, normal and thrust faulting in a single tectonic setting.

  5. Reconstruction of Northeast Asian Deformation Integrated with Western Pacific Plate Subduction since 200 Ma

    Science.gov (United States)

    Liu, S.; Gurnis, M.; Ma, P.; Zhang, B.

    2017-12-01

    The configuration and kinematics of continental deformation and its marginal plate tectonics on the Earth's surface are intrinsic manifestations of plate-mantle coupling. The complex interactions of plate boundary forces result in plate motions that are dominated by slab pull and ridge push forces and the effects of mantle drag; these interactions also result in continental deformation with a complex basin-mountain architecture and evolution. The kinematics and evolution of the western Pacific subduction and northeast Asian continental-margin deformation are a first-order tectonic process whose nature and chronology remains controversial. This paper implements a "deep-time" reconstruction of the western Pacific subduction, continental accretion or collision and basin-mountain deformation in northeast Asia since 200 Ma based on a newly revised global plate model. The results demonstrate a NW-SE-oriented shortening from 200-137 Ma, a NWW-SEE-oriented extension from 136-101 Ma, a nearly N-S-oriented extension and uplift with a short-term NWW-SEE-oriented compressional inversion in northeast China from 100-67 Ma, and a NW-SE- and nearly N-S-oriented extension from 66 Ma to the present day. The western Pacific oceanic plate subducted forward under East Asia along Mudanjiang-Honshu Island during the Jurassic, and the trenches retreated to the Sikhote-Alin, North Shimanto, and South Shimanto zones from ca. 137-128 Ma, ca. 130-90 Ma, and in ca. 60 Ma, respectively. Our time-dependent analysis of plate motion and continental deformation coupling suggests that the multi-plate convergent motion and ocean-continent convergent orogeny were induced by advance subduction during the Jurassic and earliest Cretaceous. Our analysis also indicates that the intra-continent rifting and back-arc extension were triggered by trench retreat during the Cretaceous and that the subduction of oceanic ridge and arc were triggered by trench retreat during the Cenozoic. Therefore, reconstructing

  6. Fuel cell end plate structure

    Science.gov (United States)

    Guthrie, Robin J.; Katz, Murray; Schroll, Craig R.

    1991-04-23

    The end plates (16) of a fuel cell stack (12) are formed of a thin membrane. Pressure plates (20) exert compressive load through insulation layers (22, 26) to the membrane. Electrical contact between the end plates (16) and electrodes (50, 58) is maintained without deleterious making and breaking of electrical contacts during thermal transients. The thin end plate (16) under compressive load will not distort with a temperature difference across its thickness. Pressure plate (20) experiences a low thermal transient because it is insulated from the cell. The impact on the end plate of any slight deflection created in the pressure plate by temperature difference is minimized by the resilient pressure pad, in the form of insulation, therebetween.

  7. Scheme of fault tectonic and tectonic activity manifestation in the region of the Crimea nuclear power plant construction

    International Nuclear Information System (INIS)

    Pasynkov, A.L.

    1989-01-01

    Characteristic of fault tectonics and tectonic activity manifestation in the region of the Crimea nuclear power plant construction is presented. Mosaic-block structure of the area, predetermined by the development of diagonal systems of activated tectonic dislocations with different displacement amplitudes and different stratigraphic ranges of manifestation, was established. Strained-stressed state of the region is determined by the presence of the South-Azov zone of deep fault and Krasnogorsk-Samarlinks fault system. The presented scheme can be used as tectonic basis of seismogenic activity of the region

  8. cobalt (ii), nickel (ii)

    African Journals Online (AJOL)

    DR. AMINU

    ABSTRACT. The manganese (II), cobalt (II), nickel (II) and copper (II) complexes of N, N' – bis(benzoin)ethylenediiminato have been prepared and characterized by infrared, elemental analysis, conductivity measurements and solubility. The potentiometric, and elemental analyses studies of the complexes revealed 1:1 ...

  9. Tectonic evolution of the Sicilian Maghrebian Chain inferred from stratigraphic and petrographic evidences of Lower Cretaceous and Oligocene flysch

    Directory of Open Access Journals (Sweden)

    Puglisi Diego

    2014-08-01

    Full Text Available The occurrence of a Lower Cretaceous flysch group, cropping out from the Gibraltar Arc to the Balkans with a very similar structural setting and sedimentary provenance always linked to the dismantling of internal areas, suggests the existence of only one sedimentary basin (Alpine Tethys s.s., subdivided into many other minor oceanic areas. The Maghrebian Basin, mainly developed on thinned continental crust, was probably located in the westernmost sector of the Alpine Tethys. Cretaceous re-organization of the plates triggered one (or more tectonic phases, well recorded in almost all the sectors of the Alpine Tethys. However, the Maghrebian Basin seems to have been deformed by Late- or post-Cretaceous tectonics, connected with a “meso-Alpine” phase (pre-Oligocene, already hypothesized since the beginning of the nineties. Field geological evidence and recent biostratigraphic data also support this important meso- Alpine tectonic phase in the Sicilian segment of the Maghrebian Chain, indicated by the deformations of a Lower Cretaceous flysch sealed by Lower Oligocene turbidite deposits. This tectonic development is emphasized here because it was probably connected with the onset of rifting in the southern paleomargin of the European plate, the detaching of the so-called AlKaPeCa block (Auct.; i.e. Alboran + Kabylian + Calabria and Peloritani terranes and its fragmentation into several microplates. The subsequent early Oligocene drifting of these microplates led to the progressive closure of the Maghrebian Basin and the opening of new back-arc oceanic basins, strongly controlled by extensional processes, in the western Mediterranean (i.e. Gulf of Lion, Valencia Trough, Provençal Basin and Alboran Sea.

  10. Determination of activities of human carbonic anhydrase II inhibitors ...

    African Journals Online (AJOL)

    Purpose: To evaluate the activities of new curcumin analogs as carbonic anhydrase II (CA-II) inhibitor. Methods: Carbonic anhydrase II (CA-II) inhibition was determined by each ligand capability to inhibit the esterase activity of CA-II using 4-NPA as a substrate in 96-well plates. Dimethyl sulfoxide was used to dissolve each ...

  11. Plate Full of Color

    Centers for Disease Control (CDC) Podcasts

    2008-08-04

    The Eagle Books are a series of four books that are brought to life by wise animal characters - Mr. Eagle, Miss Rabbit, and Coyote - who engage Rain That Dances and his young friends in the joy of physical activity, eating healthy foods, and learning from their elders about health and diabetes prevention. Plate Full of Color teaches the value of eating a variety of colorful and healthy foods.  Created: 8/4/2008 by National Center for Chronic Disease Prevention and Health Promotion (NCCDPHP).   Date Released: 8/5/2008.

  12. Tectonic geomorphology and volcano-tectonic interaction in the eastern boundary of the Southern Cascades (Hat Creek Graben region, California, USA

    Directory of Open Access Journals (Sweden)

    Engielle Mae Raot-raot Paguican

    2016-07-01

    Full Text Available The eastern boundary of the Southern Cascades (Hat Creek Graben region, California, USA, is an extensively faulted volcanic corridor between the Cascade Range and Modoc Plateau. The east-west extending region is in the transition zone between the convergence and subduction of the Gorda Plate underneath the North American Plate; north-south shortening within the Klamath Mountain region; and transcurrent movement in the Walker Lane. We describe the geomorphological and tectonic features, their alignment and distribution, in order to understand the tectonic geomorphology and volcano-tectonic relationships. One outcome of the work is a more refined morpho-structural description that will affect future hazard assessment in the area.A database of volcanic centers and structures was created from interpretations of topographic models generated from satellite images. Volcanic centers in the region were classified by morphological type into cones, sub-cones, shields and massifs. A second classification by height separated the bigger and smaller edifices and revealed an evolutionary trend. Poisson Nearest Neighbor analysis shows that bigger volcanoes are spatially dispersed while smaller ones are clustered. Using volcano centroid locations, about 90 lineaments consisting of at least three centers within 6km of one another were found, revealing that preferential north-northwest directed pathways control the transport of magma from the source to the surface, consistent with the strikes of the major fault systems. Most of the volcano crater openings are perpendicular to the maximum horizontal stress, expected for extensional environments with dominant normal regional faults. These results imply that the extension of the Hat Creek Graben region and impingement of the Walker Lane is accommodated mostly by extensional faults and partly by the intrusions that formed the volcanoes. Early in the history of a volcano or volcano cluster, melt produced at depth in the

  13. Subsidence of the South Polar Terrain and global tectonic of Enceladus

    Science.gov (United States)

    Czechowski, Leszek

    2016-04-01

    Introduction: Enceladus is the smallest celestial body in the Solar System where volcanic and tectonic activities are observed. Every second, the mass of ˜200 kg is ejected into space from the South Polar Terrain (SPT) - [1]. The loss of matter from the body's interior should lead to global compression of the crust (like on Mercury). Typical effects of compression are: thrust faults, folding and subduction. However, such forms are not dominant on Enceladus. We propose here special dynamical process that could explain this paradox. Our hypothesis states that the mass loss from SPT is the main driving mechanism of the following tectonic processes: subsidence of SPT, flow in the mantle and motion of adjacent tectonic plates. The hypothesis is presented in [2] and [3]. We suggest that the loss of the volatiles results in a void, an instability, and motion of solid matter to fill the void. The motion includes: Subsidence of the 'lithosphere' of SPT. Flow of the matter in the mantle. Motion of plates adjacent to SPT towards the active region. Methods and results: The numerical model of the subsidence process is developed. It is based on the model of thermal convection in the mantle. Special boundary conditions are applied, that could simulate subsidence of SPT. If emerging void is being filled by the subsidence of SPT only, then the velocity of subsidence is ˜0.05 mmṡyr-1. However, numerical calculations indicate that all three types of motion are usually important. The role of a given motion depends on the viscosity distribution. Generally, for most of the models the subsidence is ˜0.02 mmṡyr-1, but mantle flow and plates' motion also play a role in filling the void. The preliminary results of the numerical model indicate also that the velocity of adjacent plates could be ˜0.02 mmṡyr-1 for the Newtonian rheology. Note that in our model the reduction of the crust area is not a result of compression but it is a result of the plate sinking. Therefore the

  14. Intracontinental mantle plume and its implications for the Cretaceous tectonic history of East Asia

    Science.gov (United States)

    Ryu, In-Chang; Lee, Changyeol

    2017-12-01

    A-type granitoids, high-Mg basalts (e.g., picrites), adakitic rocks, basin-and-range-type fault basins, thinning of the North China Craton (NCC), and southwest-to-northeast migration of the adakites and I-type granitoids in southern Korea and southwestern Japan during the Cretaceous are attributed to the passive upwelling of deep asthenospheric mantle or ridge subduction. However, the genesis of these features remains controversial. Furthermore, the lack of ridge subduction during the Cretaceous in recently suggested plate reconstruction models poses a problem because the Cretaceous adakites in southern Korea and southwestern Japan could not have been generated by the subduction of the old Izanagi oceanic plate. Here, we speculate that plume-continent (intracontinental plume-China continent) and subsequent plume-slab (intracontinental plume-subducted Izanagi oceanic plate) interactions generated the various intracontinental magmatic and tectonic activities in eastern China, Korea, and southwestern Japan. We support our proposal using three-dimensional numerical models: 1) An intracontinental mantle plume is dragged into the mantle wedge by corner flow of the mantle wedge, and 2) the resultant channel-like flow of the mantle plume in the mantle wedge apparently migrated from southwest to northeast because of the northeast-to-southwest migration of the East Asian continental blocks with respect to the Izanagi oceanic plate. Our model calculations show that adakites and I-type granitoids can be generated by increased slab-surface temperatures because of the channel-like flow of the mantle plume in the mantle wedge. We also show that the southwest-to-northeast migration of the adakites and I-type granitoids in southern Korea and southwestern Japan can be attributable to the opposite migration of the East Asian continental blocks with respect to the Izanagi oceanic plate. This correlation implies that an intracontinental mantle plume existed in eastern China during the

  15. Refining plate reconstructions of the North Atlantic and Ellesmerian domains

    Science.gov (United States)

    Shephard, Grace E.; Abdelmalak, Mansour M.; Buiter, Susanne; Piepjohn, Karsten; Jones, Morgan; Torsvik, Trond; Faleide, Jan Inge; Gaina, Carmen

    2017-04-01

    Located at the intersection of major tectonic plates, the North Atlantic and western Arctic domains have experienced both widespread and localized deformation since the Paleozoic. In conventional tectonic reconstructions, the plates of Greenland, Eurasia and North America are assumed to be rigid. However, prior to the onset of seafloor spreading, rifting lithosphere experiences significant thinning that is usually not accounted for. This leads to significant (in excess of 300 km in places) over- and under-laps between conjugate continent-ocean boundaries, an incomplete history of basin evolution, and loose correlations between climatic, volcanic, oceanographic and, geologic events. Furthermore, a handful of alternative regional reconstructions now exist, which predict different timings, rates and locations of relative motion and associated deformation. Assumptions of reference crustal thicknesses and the nature of lower crustal bodies, as well as the location of basin hinge lines have to-date not yet been incorporated into a consistent regional kinematic model. Notably, the alternative models predict varying episodes of compression or quiescence, not just orthogonal or oblique rifting. Here, we present new temporal and spatial-dependent results related to (1) the dominant rifting episodes across the North Atlantic (Carboniferous, Late Permian, Late Jurassic-Early Cenozoic and Late Cretaceous-Paleogene), and (2) restoration of compression and strike-slip motion between northern Greenland, Ellesmere Island (North America) and Spitsbergen (Eurasia) related to the Eurekan Orogeny. We achieve this by integrating a series of conjugate seismic profiles, calculated stretching factors, dated volcanic events, structural mapping and mass-balanced restorations into a global plate motion model via GPlates software. We also test alternative models of rift velocities (as kinematic boundary conditions) with 2-D lithosphere and mantle numerical models, and explore the importance of

  16. TECTONIC ZONING OF THE SEDIMENTARY COVER IN THE DERYUGIN BASIN OF THE SEA OF OKHOTSK BASED ON STRUCTURAL-MATERIAL (LITHOPHYSICAL) INDICATORS

    OpenAIRE

    V. P. Semakin; A. V. Kochergin

    2013-01-01

    In terms of tectonics, the Deryugin basin (Fig. 1) is a part of the epi-Mesozoic Okhotsk plate comprising the heterogeneous basement that is mainly pre-Cenozoic (the lower structural stage) and the sedimentary cover that is mainly represented by the Paleogenic-Neogenic-Quaternary deposits with the Upper Cretaceous sedimentary rocks observed locally without a visible hiatus (the upper structural stage).The acoustic basement (AB) is composed of the metamorphosed Upper Cretaceous-Paleogenic silt...

  17. Tectonics control over instability of volcanic edifices in transtensional tectonic regimes

    Science.gov (United States)

    Norini, G.; Capra, L.; Lagmay, A. M. F.; Manea, M.; Groppelli, G.

    2009-04-01

    We present the results of analogue modeling designed to investigate the interactions between volcanic edifices and transtensional basement faulting. Three sets of experiments were run to account for three examples of stratovolcanoes in active transtensive tectonics regimes, the Nevado de Toluca and Jocotitlan volcanoes in Mexico, and the Mayon volcano in the Philippines. All these volcanoes show different behavior and relationship among volcanism, instability of the volcanic edifice, and basement tectonics. Field geological and structural data gave the necessary constrains to the models. The modeling apparatus consisted of a sand cone on a sheared basal layer. Injections of vegetable oil were used to model the rising of magma inside the deformed analogue cones. Set 1: In the case of a volcano directly on top of a basal transtensive shear producing a narrow graben, as observed on the Nevado de Toluca volcano, the analogue models reveal a strong control of the basement faulting on the magma migration path and the volcano instability. Small lateral collapses are directed parallel to the basal shear and affect a limited sector of the cone. Set 2: If the graben generated by transtensive tectonics is bigger in respect to the volcanic edifice and the volcano sits on one boundary fault, as in the case of Mayon volcano, the combined normal and transcurrent movements of the analogue basement fault generate a sigmoidal structure in the sand cone, inducing major sector collapses directed at approx 45° relative to the basement shear toward the downthrown block. Set 3: For volcanoes located near major transtensive faults, as the Jocotitlan volcano, analogue modelling shows an important control of the regional tectonics on the geometry of the fractures and migration paths of magma inside the cone. These structures render unstable the flanks of the volcano and promote sector collapses perpendicular to the basement shear and directed toward the graben formed by the transtensive

  18. Tectonic stress accumulation in Bohai–Zhangjiakou Seismotectonic ...

    Indian Academy of Sciences (India)

    Keywords. Bohai–Zhangjiakou Seismotectonic Zone; tectonic stress accumulation; visco-elastic modelling; Moho surface; modern tectonic stress field ... College of Resources, Shijiazhuang University of Economics, Shijiazhuang 050031, China. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing ...

  19. Characterisation of tectonic lineaments in the Central Equatorial ...

    African Journals Online (AJOL)

    Characterisation of tectonic lineaments in the Central Equatorial Atlantic region of Africa using Bouguer anomaly gravity data. ... Ife Journal of Science ... 3-D standard Euler deconvolution analysis was carried out on Bouguer anomaly gravity data for configuration definition and approximate depth estimate of tectonic ...

  20. Assemblage of strike-slip faults and tectonic extension and ...

    Indian Academy of Sciences (India)

    12

    Assemblage of strike-slip faults and tectonic. 1 extension and compression analysis: A case. 2 study of a Lower Permian commercial coal. 3 reservoir in China. 4. 5. Shuai Yina,*, Dawei Lvb, Zhonghu Wu c .... high-quality reservoirs, and tectonic action is a leading factor for oil and gas. 70 enrichment. Therefore, it is of great ...

  1. Provenance, tectonic setting and source-area weathering of the ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 126; Issue 2. Provenance, tectonic setting and ... The chondrite normalized REE pattern of the samples is equivalent to uppercontinental crust, which reflects enriched LREE and flat HREE with negative Eu anomaly. The tectonic setting discriminant diagram log[K ...

  2. CMS Resistive plate Champers

    CERN Document Server

    Zainab, Karam

    2013-01-01

    There are many types of gas detectors which are used in CERN in LHC project, There is a main parts for the gas detectors which must be in all gas detectors types like Multiwire proportional chambers, such as the micromesh gaseous structure chamber (the MicroMegas), Gas-electron multiplier (GEM) detector, Resistive Plate Champers... Compact Muon Solenoid (CMS) experiment detecting muons which are powerful tool for recognizing signatures of interesting physics processes. The CMS detector uses: drift tube (DT), cathode strip chamber (CSC) and resistive plate chamber (RPC). Building RPC’s was my project in summer student program (hardware). RPC’s have advantages which are triggering detector and Excellent time resolution which reinforce the measurement of the correct beam crossing time. RPC’s Organized in stations :  RPC barrel (RB) there are 4 stations, namely RB1, RB2, RB3, and RB4  While in the RPC endcap (RE) the 3 stations are RE1, RE2, and RE3. In the endcaps a new starion will be added and this...

  3. Tectonic characteristics and structural styles of a continental rifted basin: Revelation from deep seismic reflection profiles

    Directory of Open Access Journals (Sweden)

    Yuan Li

    2016-09-01

    Full Text Available The Fushan Depression is a half-graben rifted sub-basin located in the southeast of the Beibuwan Basin, South China Sea. The Paleogene Liushagang sequence is the main hydrocarbon-bearing stratigraphic unit in the sub-basin. Using three-dimensional (3-D seismic data and logging data over the sub-basin, we analyzed structural styles and sedimentary characteristics of the Liushagang sequence. Five types of structural styles were defined: ancient horst, traditional slope, flexure slope-break, faulted slope-break and multiple-stage faults slope, and interpretations for positions, background and development formations of each structural style were discussed. Structural framework across the sub-basin reveals that the most remarkable tectonic setting is represented by the central transfer zone (CTZ which divides the sub-basin into two independent depressions, and two kinds of sequence architectures are summarized: (i the western multi-stage faults slope; (ii the eastern flexure slope break belt. Combined with regional stress field of the Fushan Depression, we got plane combinations of the faults, and finally built up plan distribution maps of structural system for main sequence. Also, we discussed the controlling factors mainly focused on subsidence history and background tectonic activities such as volcanic activity and earthquakes. The analysis of structural styles and tectonic evolution provides strong theoretical support for future prospecting in the Fushan sub-basin and other similar rifted basins of the Beibuwan Basin in South China Sea.

  4. Tectonics and paleogeography along the Amazon river

    Science.gov (United States)

    Costa, João Batista Sena; Léa Bemerguy, Ruth; Hasui, Yociteru; da Silva Borges, Maurício

    2001-09-01

    The main structural and geomorphological features along the Amazon River are closely associated with Mesozoic and Cenozoic tectonic events. The Mesozoic tectonic setting is characterised by the Amazonas and Marajó Basins, two distinct extensional segments. The Amazonas Basin is formed by NNE-SSW normal faults, which control the emplacement of dolerite dykes and deposition of the sedimentary pile. In the more intense tectonic phase (mid-Late Cretaceous), the depocentres were filled with fluvial sequences associated with axial drainage systems, which diverge from the Lower Tapajós Arch. During the next subsidence phase, probably in the Early Tertiary, and under low rate extension, much of the drainage systems reversed, directing the paleo-Amazon River to flow eastwards. The Marajó Basin encompasses NW-SE normal faults and NE-SW strike-slip faults, with the latter running almost parallel to the extensional axes. The normal faults controlled the deposition of thick rift and post-rift sequences and the emplacement of dolerite dykes. During the evolution of the basin, the shoulder (Gurupá Arch) became distinct, having been modelled by drainage systems strongly controlled by the trend of the strike-slip faults. The Arari Lineament, which marks the northwest boundary of the Marajó Basin, has been working as a linkage corridor between the paleo and modern Amazon River with the Atlantic Ocean. The neotectonic evolution since the Miocene comprises two sets of structural and geomorphological features. The older set (Miocene-Pliocene) encompasses two NE-trending transpressive domains and one NW-trending transtensive domain, which are linked to E-W and NE-SW right-lateral strike-slip systems. The transpressive domains display aligned hills controlled by reverse faults and folds, and are separated by large plains associated with pull-apart basins along clockwise strike-slip systems (e.g. Tupinambarana Lineament). Many changes were introduced in the landscape by the

  5. Tectonics and the photosynthetic habitable zone (Invited)

    Science.gov (United States)

    Sleep, N. H.

    2009-12-01

    The traditional habitable zone lies between an inner stellar radius where the surface of the planet becomes too hot for liquid water carbon-based life and on outer radius, where the surface freezes. It is effectively the zone where photosynthesis is feasible. The concept extends to putative life on objects with liquid methane at the surface, like Titan. As a practical matter, photosynthesis leaves detectable biosignatures in the geological record; black shale on the Earth indicates that sulfide and probably FeO based photosynthesis existed by 3.8 Ga. The hard crustal rocks and the mantle sequester numerous photosynthetic biosignatures. Photosynthesis can produce detectable free oxygen with ozone in the atmosphere of extrasolar planets. In contrast, there is no outer limit for subsurface life in large silicate objects. Pre-photosynthetic niches are dependable but meager and not very detectable at great antiquity or great distance, with global productivity less than 1e-3 of the photosynthetic ones. Photosynthetic organisms have bountiful energy that modifies their surface environment and even tectonics. For example, metamorphic rocks formed at the expense of thick black shale are highly radioactive and hence self-fluxing. Active tectonics with volcanism and metamorphism prevents volatiles from being sequestered in the subsurface as on Mars. A heat-pipe object, like a larger Io, differs from the Earth in that the volatiles return to the deep interior distributed within massive volcanic deposits rather than concentrated in the shallow oceanic crust. One the Earth, the return of water to the surface by arc volcanoes controls its mantle abundance at the transition between behaving as a trace element and behaving as a major element that affects melting. The ocean accumulates the water that the mantle and crust do not take. The Earth has the “right” amount of water that erosion/deposition and tectonics both tend to maintain near sea level surfaces. The mantle contains

  6. Remembering myth and ritual in the everyday tectonics of hospitals

    DEFF Research Database (Denmark)

    Tvedebrink, Tenna Doktor Olsen

    2015-01-01

    When discussing tectonics, the book Studies in tectonic culture by Kenneth Frampton (2001) is often mentioned for linking the ethics of architecture with a focus on structural genius. Another reference is the paper The tell-the-tale detail by Marco Frascari (1984), which in addition to Frampton put...... emphasis on both the physical construction and mental construing of architecture. With this dual perspective Frascari established a discourse in tectonic thinking which brings the tectonic expression beyond structural genius into socio-cultural realms of storytelling, myth and ritual. However, in everyday...... architecture like hospitals this perspective of construing is often neglected. In this paper, I explore if it is possible through a re-reading of Frascari’s words to inspire for a re-construction of everyday tectonics? Based on project MORE at Aalborg Hospital, I argue that the perspective of construing...

  7. Tectonic Evolution of Mozambique Ridge in East African continental margin

    Science.gov (United States)

    Tang, Yong

    2017-04-01

    Tectonic Evolution of Mozambique Ridge in East African continental margin Yong Tang He Li ES.Mahanjane Second Institute of Oceanography,SOA,Hangzhou The East Africa passive continental margin is a depression area, with widely distributed sedimentary wedges from southern Mozambique to northern Somali (>6500km in length, and about 6km in thickness). It was resulted from the separation of East Gondwana, and was developed by three stages: (1) rifting in Early-Middle Jurassic; (2) spreading from Late Jurassic to Early Cretaceous; (3) drifting since the Cretaceous period. Tectonic evolution of the Mozambique continental margin is distinguished by two main settings separated by a fossil transform, the Davie Fracture Zone; (i) rifting and transform setting in the northern margin related to opening of the Somali and Rovuma basins, and (ii) rifting and volcanism setting during the opening of the Mozambique basin in the southern margin. 2D reflection seismic investigation of the crustal structure in the Zambezi Delta Depression, provided key piece of evidence for two rifting phases between Africa and Antarctica. The magma-rich Rift I phase evolved from rift-rift-rift style with remarkable emplacement of dyke swarms (between 182 and 170 Ma). Related onshore outcrops are extensively studied, the Karoo volcanics in Mozambique, Zimbabwe and South Africa, all part of the Karoo "triple-junction". These igneous bodies flow and thicken eastwards and are now covered by up to 5 km of Cretaceous and Tertiary sediments and recorded by seismic and oil exploration wells. Geophysical and geological data recorded during oceanographic cruises provide very controversial results regarding the nature of the Mozambique Ridge. Two conflicting opinions remains open, since the early expeditions to the Indian Ocean, postulating that its character is either magmatic (oceanic) or continental origin. We have carried out an China-Mozambique Joint Cruise(CMJC) on southern Mozambique Basin on 1st June to

  8. Modelling and visualizing distributed compressional plate deformation using GPlates2.0: The Arctic Eurekan Orogeny

    Science.gov (United States)

    Gion, Austin; Williams, Simon; Müller, Dietmar

    2017-04-01

    Present-day distributed plate deformation is being mapped and simulated in great detail, largely based on satellite observations. In contrast, the modelling of and data assimilation into deforming plate models for the geological past is still in its infancy. The recently released GPLates2.0 (www.gplates.org) software provides a framework for building plate models including diffuse deformation. Here we present an application example for the Eurekan orogeny, a Paleogene tectonic event driven by sea floor spreading in the Labrador Sea and Baffin Bay, resulting in compression between NW Greenland and the Canadian Arctic. The complexity of the region has prompted the development of countless tectonic models over the last 100 years. Our new tectonic model incorporates a variety of geological field and geophysical observations to model rigid and diffuse plate deformation in this region. Compression driven by Greenland's northward motion contemporaneous with sea floor spreading in the Labrador Sea, shortens Ellesmere Island in a "fan" like pattern, creating a series of thrust faults. Our model incorporates two phases of tectonic events during the orogeny from 63-35 Ma. Phase one from 63 to 55 Ma incorporates 85 km of Paleocene extension between Ellesmere Island and Devon Island with extension of 20 km between Axel Heiberg Island and Ellesmere Island and 85 km of left-lateral strike-slip along the Nares Strait/Judge Daly Fault System, matching a range of 50-100 km indicated by the offset of marker beds, facies contacts, and platform margins between the conjugate Greenland and Ellesmere Island margins. Phase two from 55 to 35 Ma captures 30 km of east-west shortening and 200 km of north-south shortening from Ellesmere Island to the Canadian Arctic Island margins. Our model extends the boundaries of the Eurekan Orogeny northward, considering its effect on the Lomonosov Ridge, Morris Jessup Rise, and the Yermak Plateau , favouring a model in which the Lomonosov Ridge moves

  9. The Nature of Tectonic Spatial Structures

    DEFF Research Database (Denmark)

    Carter, Adrian; Kirkegaard, Poul Henning

    2010-01-01

    Since earliest times mankind has sought inspiration from nature for our built structures. However until the dawn of the modern era in architecture and design, the true structural character of a building was invariably full y or partially encased in an ornamented cladding, of often stylised motifs...... of nature. The modern emphasis on honest structural expression has resulted in more sincere and innovative interpretations of nature in spatial structures. With reference to the works of amongst others of Gaudi, Candela, Otto, Nervi, Utzon, Calatrava and Foreign Office Architects (FOA) and the writings...... particularly of Kenneth Frampton, this paper will argue that the direct inspiration of nature and the increasing use of advanced parametric digital design tools that replicate virtually instantaneously evolutionary processes results in structures that are not only elegant tectonically and in terms of economy...

  10. Tectonic thinking in contemporary industrialized architecture

    DEFF Research Database (Denmark)

    Beim, Anne

    2013-01-01

    and the understanding of the architectural design process ought to be revised. The paper is based on the following underlying hypothesis: ‘Tectonic thinking – defined as a central attention towards the nature, the properties, and the application of building materials (construction) and how this attention forms......This paper argues for a new critical approach to the ways architectural design strategies are developing. Contemporary construction industry appears to evolve into highly specialized and optimized processes driven by industrialized manufacturing, therefore the role of the architect...... a creative force in building constructions, structural features and architectural design (construing) – helps to identify and refine technology transfer in contemporary industrialized building construction’. Through various references from the construction industry, business theory and architectural practice...

  11. Grabens on Io: Evidence for Extensional Tectonics

    Science.gov (United States)

    Hoogenboom, T.; Schenk, P.

    2012-12-01

    Io may well be the most geologically active body in the solar system. A variety of volcanic features have been identified, including a few fissure eruptions, but tectonism is generally assumed to be limited to compression driven mountain formation (Schenk et al., 2001). A wide range of structural features can also be identified including scarps, lineaments, faults, and circular depressions (pits and patera rims). Narrow curvilinear graben (elongated, relatively depressed crustal unit or block that is bounded by faults on its sides) are also scattered across Io's volcanic plains. These features are dwarfed by the more prominent neighboring volcanoes and mountains, and have been largely ignored in the literature. Although they are likely to be extensional in origin, their relationship to local or global stress fields is unknown. We have mapped the locations, length and width of graben on Io using all available Voyager and Galileo images with a resolution better than 5 km. We compare the locations of graben with existing volcanic centers, paterae and mountain data to determine the degree of correlation between these geologic features and major topographic variations (basins/swells) in our global topographic map of Io (White et al., 2011). Graben are best observed in > 1-2 km low-sun angle images. Approximately 300 images were converted from ISIS to ArcMap format to allow easy comparison with the geological map of Io (Williams et al., 2012) along with previous higher resolution structural mapping of local areas (e.g. Crown et al., 1992). We have located >45 graben to date. Typically 1-3 kilometers across, some of these features can stretch for over 500 kilometers in length. Their formation may be related to global tidal stresses or local deformation. Io's orbit is eccentric and its solid surface experiences daily tides of up to ˜0.1 km, leading to repetitive surface strains of 10-4 or greater. These tides flex and stress the lithosphere and can cause it to fracture

  12. A comprehensive view of Late Quaternary fluvial sediments and stratal architecture in a tectonically active basin: Influence of eustasy, climate, and tectonics on the Bengal Basin and Brahmaputra River system

    Science.gov (United States)

    Sincavage, R.; Goodbred, S. L.; Williams, L. A.; Pickering, J.; Wilson, C.; Steckler, M. S.; Seeber, L.; Reitz, M. D.; Hossain, S.; Akhter, S. H.; Mondal, D. R.; Paola, C.

    2013-12-01

    More than 130 closely-spaced (~3-5 km) boreholes have been drilled along five transects in the upper Bengal Basin, providing the first detailed record of the stratigraphic architecture and provenance of the entire Late Quaternary fluviodeltaic sedimentary succession of the Ganges-Brahmaputra-Meghna Delta (GBMD). This effort is part of BanglaPIRE, an interdisciplinary, multi-institutional research effort aimed at unraveling the history and mechanisms of river-tectonic-basin interactions in the GBMD and Bengal basin, around which three tectonic plates converge. Following the Younger-Dryas, the onset of a strong summer monsoon coincident with continued eustatic sea-level rise initiated construction of the modern delta and rapid development of a thick (up to 80 m) succession of fluvial and deltaic sediments. These deposits illustrate several (3-4) avulsions and asymmetric occupations of the Brahmaputra River in the tectonically active Sylhet Basin. We hypothesize that the longer occupation periods (10 3 years) may be classified as major river avulsions driven by autogenic fluvial processes, whereas shorter occupation periods (10 2 years) reflect minor distributive events that may have been initiated by allogenic forcing via floods or earthquakes. Subsidence rates in Sylhet Basin, driven by an active foredeep, are relatively high (~5 mm/yr); however, the Brahmaputra River does not regularly migrate towards this side of the delta. Annual widespread flooding of Sylhet Basin may negate the potential topographic attraction for the system to be steered in this direction. Furthermore, a gentle westward topographic tilt of the active thrust front of the Tripura fold belt appears to have forced lateral steering of the Brahmaputra River and initiated erosion of a bench-cut terrace into an adjacent Pleistocene landform. Tectonic effects over longer timescales (10 3 years) are revealed by the presence of sediment with a unique provenance at the core of regional anticlines, which

  13. Anatomy of a diffuse cryptic suture zone exemplified by European Variscan belt: a new concept of continental tectonics

    Science.gov (United States)

    Lexa, Ondrej; Schulmann, Karel; Janoušek, Vojtěch; Lardeaux, Jean Marc

    2014-05-01

    The plate tectonics paradigm has offered a link between the horizontal movement of lithospheric plates, closure of intervening oceanic basin and formation of oceanic suture zone preserved even during continental collision. On the example of the Bohemian Massif we document the evolution of Andean type orogen involved in continental collision. Based on combined geological data, geophysical imagery and fully scaled thermomechanical modelling a modified view on the internal architecture of collisional orogens is proposed. The characteristic feature of the model proposed for the Variscan orogen in the Bohemian Massif is the convergence of two contrasting domains of lithosphere, leading to subduction of an attenuated felsic metaigneous crust under the rifted (Gondwana) margin formed by a dense sequence of metasedimentary and metabasic rocks. The relamination of refractory light material rich in radioactive elements underneath the relatively dense upper plate is responsible for the gravitational instabilities that lead to the overturns in the thickened crust. This mechanism results in the formation of a diffuse cryptic suture zone, i.e., a wide zone in which materials from the lower and upper plates are mixed to form a hybrid continental crust. The diffuse cryptic suture zone remains the only evidence of the original plate boundary repeatedly re-appearing within the orogen. We propose that this model may have a general validity and possible link to modern orogens exemplified by comparison of Variscan and Tibetan orogenic systems is proposed based on petrological characteristics and similarities in geophysical signatures.

  14. Design of bridges against large tectonic deformation

    Science.gov (United States)

    Anastasopoulos, I.; Gazetas, G.; Drosos, V.; Georgarakos, T.; Kourkoulis, R.

    2008-12-01

    The engineering community has devoted much effort to understanding the response of soil-structure systems to seismic ground motions, but little attention to the effects of an outcropping fault offset. The 1999 earthquakes of Turkey and Taiwan, offering a variety of case histories of structural damage due to faulting, have (re)fueled the interest on the subject. This paper presents a methodology for design of bridges against tectonic deformation. The problem is decoupled in two analysis steps: the first (at the local level) deals with the response of a single pier and its foundation to fault rupture propagating through the soil, and the superstructure is modeled in a simplified manner; and the second (at the global level) investigates detailed models of the superstructure subjected to the support (differential) displacements of Step 1. A parametric study investigates typical models of viaduct and overpass bridges, founded on piles or caissons. Fixed-head piled foundations are shown to be rather vulnerable to faulting-induced deformation. End-bearing piles in particular are unable to survive bedrock offsets exceeding 10 cm. Floating piles perform better, and if combined with hinged pile-to-cap connections, they could survive much larger offsets. Soil resilience is beneficial in reducing pile distress. Caisson foundations are almost invariably successful. Statically-indeterminate superstructures are quite vulnerable, while statically-determinate are insensitive (allowing differential displacements and rotations without suffering any distress). For large-span cantilever-construction bridges, where a statically determinate system is hardly an option, inserting resilient seismic isolation bearings is advantageous as long as ample seating can prevent the deck from falling off the supports. An actual application of the developed method is presented for a major bridge, demonstrating the feasibility of design against tectonic deformation.

  15. Emplacement of sandstone intrusions during contractional tectonics

    Science.gov (United States)

    Palladino, Giuseppe; Grippa, Antonio; Bureau, Denis; Alsop, G. Ian; Hurst, Andrew

    2016-08-01

    Sandstone injections are created by the forceful emplacement of remobilized sand in response to increases in overpressure. However, the contribution provided by horizontal compressive stress to the build-up in overpressure, and the resulting emplacement of sand injection complexes, is still to be substantiated by robust field observations. An opportunity to address this issue occurs in Central California where a large volume of sandstone intrusions record regionally-persistent supra-lithostatic pore-pressure. Detailed fieldwork allows sandstone-filled thrusts to be recognized and, for the first time, permits us to demonstrate that some sandstone intrusions are linked to contractional deformation affecting the western border of the Great Valley Basin. Fluidized sand was extensively injected along thrust surfaces, and also fills local dilatant cavities linked to thrusting. The main aims of this paper are to provide detailed descriptions of the newly recognized syn-tectonic injections, and describe detailed cross-cutting relationships with earlier sandstone injection complexes in the study area. Finally, an evolutionary model consisting of three phases of sand injection is provided. In this model, sand injection is linked to contractional tectonic episodes affecting the western side of the Great Valley Basin during the Early-Middle Cenozoic. This study demonstrates that sand injections, driven by fluid overpressure, may inject along thrusts and folds and thereby overcome stresses associated with regional contractional deformation. It is shown that different generations of sand injection can develop in the same area under the control of different stress regimes, linked to the evolving mountain chain.

  16. Tectonic thinking in contemporary industrialized architecture

    Directory of Open Access Journals (Sweden)

    Anne

    2013-12-01

    Full Text Available Corresponding author: Professor Anne Beim, Ph.D., CINARK – Centre for Industrialized Architecture, Institute of Architectural Technology, The Royal Danish Academy of Fine Arts – School of Architecture, Phillip Langes ALlé 10, DK-1435 Copenhagen, Denmark. Tel.: +45 4170 1623; E-mail: anne.beim@kadk.dk This paper argues for a new critical approach to the ways architectural design strategies are developing. Contemporary construction industry appears to evolve into highly specialized and optimized processes driven by industrialized manufacturing, therefore the role of the architect and the understanding of the architectural design process ought to be revised. The paper is based on the following underlying hypothesis: ‘Tectonic thinking – defined as a central attention towards the nature, the properties, and the application of building materials (construction and how this attention forms a creative force in building constructions, structural features and architectural design (construing – helps to identify and refine technology transfer in contemporary industrialized building construction’. Through various references from the construction industry, business theory and architectural practice the paper offers various analyses, comparisons and concrete design approaches. How architectural design processes and the tectonic design can benefit from Integrated Product Deliveries, mass-customization and Design for Disassembly is examined and discussed. The paper concludes by presenting a series of arguments that call for adaptable systems based on sufficient numbers of industrialized building products of high quality and a great variety of suppliers, and point at the need for optimizing our use of resources in order to reach sustainable solutions in architecture.

  17. Late Vendian-Early Palaeozoic tectonic evolution of the Baltic Basin: regional tectonic implications from subsidence analysis.

    NARCIS (Netherlands)

    Poprawa, P.; Sliaupa, S.; Stephenson, R.A.; Lazauskiene, J.

    1999-01-01

    Subsidence analysis was performed on 43 boreholes penetrating the Upper Vendian-Lower Palaeozoic sedimentary succession of the Baltic Basin. The results were related to lithofacial and structural data to elucidate subsidence mechanisms and the regional tectonic setting of basin development. Tectonic

  18. The Iberian Plate: myth or reality?

    Energy Technology Data Exchange (ETDEWEB)

    Canerot, J.

    2016-10-01

    The plate tectonics theory generally leads us to consider that Iberia was an independent plate separated from Europe by the North Pyrenean Fault (NPF). The NPF has been commonly interpreted as a transform fault associated with a huge counterclockwise transverse and rotational movement that allowed the opening of the Bay of Biscay and the relative eastward motion of Iberia during the Mesozoic. According to some interpretations, this movement may have generated an interplate gap several hundreds of km wide, which led to the creation of an oceanic crust during the Late Jurassic and Early Cretaceous. However, field studies recently carried out in the Pyrenees do not support these interpretations. The North Pyrenean Fault (NPF) of Tertiary age is observed in the central and eastern Pyrenees, where pioneering researchers defined it as separating the North Pyrenean Zone from the Axial Zone.However, this fault cannot be identified in the western part of the range to the west of the Ossau valley. Consequently, the geodynamic evolution of Iberia has always been dependent on Europe, especially during the failed oceanic rifting in the Mid-Cretaceous. Indeed, during this period, a central zone of crustal thinning occupied by turbiditic basins separated the European from the Iberian continental crust, with a very localized mantle exhumation found only in the Mauleon basin. Therefore, far from being an interplate range, the Pyrenees can neither be considered as an intraplate unit. We can define this orogenic belt as resulting from the Tertiary tectonic inversion of a Mid-Cretaceous rift system. According to this new interpretation, Iberia would not have been an isolated plate but represented an unstable, outlying part of Europe. Rather than displaying the features of a rigid lithospheric unit with well-defined boundaries, Iberia grouped together different crustal blocks undergoing specific movements at particular times. During the Mesozoic, normal, reverse or strike

  19. Channel plate for DNA sequencing

    Science.gov (United States)

    Douthart, Richard J.; Crowell, Shannon L.

    1998-01-01

    This invention is a channel plate that facilitates data compaction in DNA sequencing. The channel plate has a length, a width and a thickness, and further has a plurality of channels that are parallel. Each channel has a depth partially through the thickness of the channel plate. Additionally an interface edge permits electrical communication across an interface through a buffer to a deposition membrane surface.

  20. Hidden Earthquake Potential in Plate Boundary Transition Zones

    Science.gov (United States)

    Furlong, Kevin P.; Herman, Matthew; Govers, Rob

    2017-04-01

    Plate boundaries can exhibit spatially abrupt changes in their long-term tectonic deformation (and associated kinematics) at triple junctions and other sites of changes in plate boundary structure. How earthquake be