Plate Tectonics by Creeps

2018 ◽  
Author(s):  
Roy Livermore
Keyword(s):  
Turbine Blade ◽  
Solid Rock ◽  
Plate Tectonics ◽  
The Other ◽  
Plate Boundaries ◽  
Living World ◽  
The Earth ◽  
Natural Home ◽  
Aero Engine ◽  
Form Part

Earthquakes are caused primarily by the movement of plates. Plates move over the mantle, and the mantle is solid rock. So why aren’t there earthquakes beneath the plates? If all plates are moving (and they are), there should be earthquakes just about everywhere, at a depth corresponding to the base of the plates. The answer is that, while plate boundaries are the natural home of jerks, the mantle beneath the plates is the preserve of creeps. Except where cold slabs penetrate to depths of 650 km or more, the mantle moves only very gradually by creep, a phenomenon that occurs in many solids, including metals, when subjected to stress. Creep can be very inconvenient, particularly where a metal happens to form part of, say, a turbine blade in an aero engine. On the other hand, creep is the process that transformed the Earth into a living world.

scholarly journals Some Geodetic Aspects of the Plate Tectonics Hypothesis

1980 ◽  
Vol 56 ◽  
pp. 87-101
Author(s):  
Kurt Lambeck
Keyword(s):  
Plate Tectonics ◽  
Geodetic Data ◽  
Geophysical Data ◽  
Plate Boundaries ◽  
Frequency Range ◽  
Crustal Motion ◽  
Intraplate Tectonics ◽  
The Earth ◽  
Seismic Frequencies ◽  
Body Tides

AbstractGeodetic observations of gravity, body tides, the Earth’s rotation and crustal motion and deformation potentially provide important constraints in the general inversion of geophysical data for determining the structure and evolution of the Earth. More specifically, the geodetic data provide constraints on the rheology of the planet in the frequency range intermediate between geological and seismic frequencies, on the geologically instantaneous kinematics of the Earth and on the mechanisms responsible for the motions within the Earth, results that are intimately related to the plate tectonics hypothesis. The discussion is limited here to only a few aspects of these “geodetic” aspects of this hypothesis, including deformation along plate boundaries, intraplate tectonics and vertical motions.

Emergence of plate tectonic during the Archean: insights from 3D numerical modelling.

2021 ◽  
Author(s):  
Andrea Piccolo ◽  
Boris Kaus ◽  
Richard White ◽  
Nicolas Arndt ◽  
Nicolas Riel
Keyword(s):  
Phase Transitions ◽  
Subduction Zones ◽  
Plate Tectonics ◽  
Large Scale ◽  
Potential Temperature ◽  
Secular Change ◽  
Plate Boundaries ◽  
Plate Tectonic ◽  
Subduction Initiation ◽  
The Earth

<p>In the plate tectonic convection regime, the external lid is subdivided into discrete plates that move independently. Although it is known that the system of plates is mainly dominated by slab-pull forces, it is not yet clear how, when and why plate tectonics became the dominant geodynamic process in our planet. It could have started during the Meso-Archean (3.0-2.9 Ga). However, it is difficult to conceive a subduction driven system at the high mantle potential temperatures (<strong>Tp</strong>) that are thought to have existed around that time, because <strong>Tp</strong> controls the thickness and the strength of the compositional lithosphere making subduction unlikely. In recent years, however, a credible solution to the problem of subduction initiation during the Archean has been advanced, invoking a plume-induced subduction mechanism[1] that seems able to generate plate-tectonic like behaviour to first order. However, it has not yet been demonstrated how these tectonic processes interact with each other, and whether they are able to eventually propagate to larger scale subduction zones.</p><p>The Archean Eon was characterized by a high <strong>Tp</strong>[2]<strong>, </strong>which generates weaker plates, and a thick and chemically buoyant lithosphere. In these conditions, slab pull forces are inefficient, and most likely unable to be transmitted within the plate. Therefore, plume-related proto-plate tectonic cells may not have been able to interact with each other or showed a different interaction as a function of mantle potential temperature and composition of the lithosphere. Moreover, due to secular change of <strong>Tp, </strong>the dynamics may change with time. In order to understand the complex interaction between these tectonic seeds it is necessary to undertake large scale 3D numerical simulations, incorporating the most relevant phase transitions and able to handle complex constitutive rheological model.</p><p>Here, we investigate the effects of the composition and <strong>Tp </strong>independently to understand the potential implications of the interaction of plume-induced subduction initiation. We employ a finite difference visco-elasto-plastic thermal petrological code using a large-scale domain (10000 x 10000 x 1000 km along x, y and z directions) and incorporating the most relevant petrological phase transitions. We prescribed two oceanic plateaus bounded by subduction zones and we let the negative buoyancy and plume-push forces evolve spontaneously. The paramount question that we aim to answer is whether these configurations allow the generation of stable plate boundaries. The models will also investigate whether the presence of continental terrain helps to generate plate-like features and whether the processes are strong enough to generate new continental terrains <span>or assemble them </span></p><p>.</p><p> </p><p>[1]       T. V. Gerya, R. J. Stern, M. Baes, S. V. Sobolev, and S. A. Whattam, “Plate tectonics on the Earth triggered by plume-induced subduction initiation,” Nature, vol. 527, no. 7577, pp. 221–225, 2015.</p><p>[2]       C. T. Herzberg, K. C. Condie, and J. Korenaga, “Thermal history of the Earth and its petrological expression,” Earth Planet. Sci. Lett., vol. 292, no. 1–2, pp. 79–88, 2010.</p><p>[3]       R. M. Palin, M. Santosh, W. Cao, S.-S. Li, D. Hernández-Uribe, and A. Parsons, “Secular metamorphic change and the onset of plate tectonics,” Earth-Science Rev., p. 103172, 2020.</p>

scholarly journals Extreme metamorphism and metamorphic facies series at convergent plate boundaries: Implications for supercontinent dynamics

Geosphere ◽  
2021 ◽  
Author(s):  
Yong-Fei Zheng ◽  
Ren-Xu Chen
Keyword(s):  
Subduction Zones ◽  
Plate Tectonics ◽  
The Other ◽  
Ultrahigh Pressure ◽  
Plate Boundaries ◽  
Lower Grade ◽  
Thermal Gradients ◽  
Mountain Building ◽  
Convergent Plate Boundaries ◽  
Metamorphic Facies

Crustal metamorphism under extreme pressure-temperature conditions produces characteristic ultrahigh-pressure (UHP) and ultrahigh-temperature (UHT) mineral assemblages at convergent plate boundaries. The formation and evolution of these assemblages have important implications, not only for the generation and differentiation of continental crust through the operation of plate tectonics, but also for mountain building along both converging and con- verged plate boundaries. In principle, extreme metamorphic products can be linked to their lower-grade counterparts in the same metamorphic facies series. They range from UHP through high-pressure (HP) eclogite facies to blueschist facies at low thermal gradients and from UHT through high-temperature (HT) granulite facies to amphibolite facies at high thermal gradients. The former is produced by low-temperature/pressure (T/P ) Alpine-type metamorphism during compressional heating in active subduction zones, whereas the latter is generated by high-T/P Buchan-type metamorphism during extensional heating in rifting zones. The thermal gradient of crustal metamorphism at convergent plate boundaries changes in both time and space, with low-T/P ratios in the compressional regime during subduction but high-T/P ratios in the extensional regime during rifting. In particular, bimodal metamorphism, one colder and the other hotter, would develop one after the other at convergent plate boundaries. The first is caused by lithospheric subduction at lower thermal gradients and thus proceeds in the compressional stage of convergent plate boundaries; the second is caused by lithospheric rifting at higher thermal gradients and thus proceeds in the extensional stage of convergent plate boundaries. In this regard, bimodal metamorphism is primarily dictated by changes in both the thermal state and the dynamic regime along plate boundaries. As a consequence, supercontinent assembly is associated with compressional metamorphism during continental collision, whereas supercontinent breakup is associated with extensional metamorphism during active rifting. Nevertheless, aborted rifts are common at convergent plate boundaries, indicating thinning of the previously thickened lithosphere during the attempted breakup of supercontinents in the history of Earth. Therefore, extreme metamorphism has great bearing not only on reworking of accretionary and collisional orogens for mountain building in continental interiors, but also on supercontinent dynamics in the Wilson cycle.

VII.—Tombs

1888 ◽  
Vol 9 ◽  
pp. 264-271
Author(s):  
D. G. Hogarth ◽  
M. R. James
Keyword(s):  
Solid Rock ◽  
The State ◽  
The Other ◽  
Ample Evidence ◽  
Gentle Slope ◽  
Past Season ◽  
The Past ◽  
The Poor ◽  
The Earth ◽  
The Temple

Tombs of all periods were opened during the past season, a few archaic ones at Leontari Vouno, which have been described by Mr. James in his account of that site, and others at Kuklia of all subsequent ages, down to the very latest. They are usually cut in the rock or earth of a gentle slope, in many cases, as in the Xylino valley at Kuklia, tier above tier: but they are also found in level ground, approached by a sloping passage now filled with earth. The whole plateau to the east of Kuklia above the is honey-combed with earth-tombs of this kind, consisting mainly of one or two vaulted chambers, leading one out of the other, without niches for the bodies, and entered by a vaulted opening closed by a slab. Such are probably tombs of the poor: the richer Cypriotes were for the most part laid in rock-tombs, such as abound in the plain north of New Paphos, and were found by us at Old Paphos on the slopes between the Temple of Aphrodite and the sea. From their greater durability and accessibility the latter were often used two or three times over, being sometimes sanctified at last for Christian burial by innumerable crosses, cut over the niches, as is the case at Cape Drepano: thus they are usually less profitable to the explorer of to-day than the earth-chambers, which were left undisturbed in the possession of their original tenants, and were not so easily detected by the τυμβωρύχος of the early centuries of our era. Of the work of the latter we found ample evidence at Kuklia: tomb after tomb was opened on the eastern slopes, in which broken glass and pottery were lying in a huge heap either in the middle or near the door, what the thieves did not want having apparently been wantonly destroyed: the lids of the sarcophagi were either hewn in pieces or wrenched aside, and even, in some cases, in order probably to evade notice, carefully replaced in statu quo. The door was by no means the favourite place of ingress, for we often dug down to find the slab quite undisturbed, while the tomb was in the state described above, and search would reveal the presence of a hole or passage cut through the solid rock from above or at the side.

Plate tectonics and Earth System Science

2021 ◽  
Author(s):  
Dietmar Müller
Keyword(s):  
Plate Tectonics ◽  
Plate Boundary ◽  
Plate Motion ◽  
Plate Boundaries ◽  
Earth System ◽  
Dynamic Topography ◽  
Lithospheric Deformation ◽  
The Earth ◽  
Plate Models ◽  
Reconstruction Software

<p>Over the last 25 years the theory of plate tectonics and a growing set of geo-databases have been used to develop global plate models with increasing sophistication, enabled by open-source plate reconstruction software, particularly GPlates. Today’s editable open-access community models include networks of evolving plate boundaries and deforming regions, reflecting the fact that tectonic plates are not always rigid. The theory of plate tectonics was originally developed primarily based on magnetic anomaly and fracture zone data from the ocean basins. As a consequence there has been a focus on applying plate tectonics to modelling the Jurassic to present-day evolution of the Earth based on the record of preserved seafloor, or only modelling the motions of continents at earlier times. Modern plate models are addressing this shortcoming with recently developed technologies built upon the pyGPlates python library, utilising evolving plate boundary topologies to reconstruct entirely destroyed seafloor for the entire Phanerozoic. Uncertainties in these reconstructions are large and can represented with end-member scenarios. These models are paving the way for a multitude of applications aimed at better understanding Earth system evolution, connecting surface processes with the Earth’s mantle via plate tectonics. These models allow us to address questions such as: What are the causes of major perturbations in the interplay between tectonic plate motion and Earth’s deep interior? How do lithospheric deformation, mantle convection driven dynamic topography and climate change together drive regional changes in erosion and sedimentation? How are major perturbations of the plate-mantle system connected to environmental change, biological extinctions and species radiation?</p>

Note on Selection of Coordinate Systems for Geodynamics

1975 ◽  
Vol 26 ◽  
pp. 395-407
Author(s):  
S. Henriksen
Keyword(s):  
Sea Level ◽  
The Other ◽  
Coordinate Systems ◽  
Mean Sea Level ◽  
The Earth ◽  
The One ◽  
Static Systems ◽  
Selection Of

The first question to be answered, in seeking coordinate systems for geodynamics, is: what is geodynamics? The answer is, of course, that geodynamics is that part of geophysics which is concerned with movements of the Earth, as opposed to geostatics which is the physics of the stationary Earth. But as far as we know, there is no stationary Earth – epur sic monere. So geodynamics is actually coextensive with geophysics, and coordinate systems suitable for the one should be suitable for the other. At the present time, there are not many coordinate systems, if any, that can be identified with a static Earth. Certainly the only coordinate of aeronomic (atmospheric) interest is the height, and this is usually either as geodynamic height or as pressure. In oceanology, the most important coordinate is depth, and this, like heights in the atmosphere, is expressed as metric depth from mean sea level, as geodynamic depth, or as pressure. Only for the earth do we find “static” systems in use, ana even here there is real question as to whether the systems are dynamic or static. So it would seem that our answer to the question, of what kind, of coordinate systems are we seeking, must be that we are looking for the same systems as are used in geophysics, and these systems are dynamic in nature already – that is, their definition involvestime.

PLANETARY SELF-ORGANIZATION

2020 ◽  
Vol 42 (3) ◽  
pp. 271-282
Author(s):  
OLEG IVANOV
Keyword(s):  
Dynamical System ◽  
Heat Source ◽  
Mantle Convection ◽  
Plate Tectonics ◽  
Rotation Speed ◽  
Self Organization ◽  
Heat Sources ◽  
Kinematic Parameters ◽  
The Earth ◽  
New Type

The general characteristics of planetary systems are described. Well-known heat sources of evolution are considered. A new type of heat source, variations of kinematic parameters in a dynamical system, is proposed. The inconsistency of the perovskite-post-perovskite heat model is proved. Calculations of inertia moments relative to the D boundary on the Earth are given. The 9 times difference allows us to claim that the sliding of the upper layers at the Earth's rotation speed variations emit heat by viscous friction.This heat is the basis of mantle convection and lithospheric plate tectonics.

scholarly journals Geocomputing, New Technologies and Historical Analysis: Tools for a Changing Planet

Proceedings ◽  
2019 ◽  
Vol 30 (1) ◽  
pp. 9
Author(s):  
Sebastiano Trevisani
Keyword(s):  
Quantitative Analysis ◽  
Philosophy Of Science ◽  
New Technologies ◽  
Historical Analysis ◽  
Holistic Approach ◽  
Research Topic ◽  
The Other ◽  
Historical Records ◽  
The Earth ◽  
The Relationship

Modern Earth Scientists need also to interact with other disciplines, apparently far from the Earth Sciences and Engineering. Disciplines related to history and philosophy of science are emblematic from this perspective. From one side, the quantitative analysis of information extracted from historical records (documents, maps, paintings, etc.) represents an exciting research topic, requiring a truly holistic approach. On the other side, epistemological and philosophy of science considerations on the relationship between geoscience and society in history are of fundamental importance for understanding past, present and future geosphere-anthroposphere interlinked dynamics.

scholarly journals The Critical Raw Materials Issue between Scarcity, Supply Risk, and Unique Properties

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1826
Author(s):  
Mihaela Girtan ◽  
Antje Wittenberg ◽  
Maria Luisa Grilli ◽  
Daniel P. S. de Oliveira ◽  
Chiara Giosuè ◽  
...  
Keyword(s):  
Scientific Community ◽  
Chemical Elements ◽  
Raw Materials ◽  
The Other ◽  
Innovation Networks ◽  
Supply Risk ◽  
European Cooperation ◽  
Research And Innovation ◽  
The Earth ◽  
Critical Raw Materials

This editorial reports on a thorough analysis of the abundance and scarcity distribution of chemical elements and the minerals they form in the Earth, Sun, and Universe in connection with their number of neutrons and binding energy per nucleon. On one hand, understanding the elements’ formation and their specific properties related to their electronic and nucleonic structure may lead to understanding whether future solutions to replace certain elements or materials for specific technical applications are realistic. On the other hand, finding solutions to the critical availability of some of these elements is an urgent need. Even the analysis of the availability of scarce minerals from European Union sources leads to the suggestion that a wide-ranging approach is essential. These two fundamental assumptions represent also the logical approach that led the European Commission to ask for a multi-disciplinary effort from the scientific community to tackle the challenge of Critical Raw Materials. This editorial is also the story of one of the first fulcrum around which a wide network of material scientists gathered thanks to the support of the funding organization for research and innovation networks, COST (European Cooperation in Science and Technology).

Part 2. The deeper structure of the Atlantic - Geological hypotheses and the earth's crust under the oceans

1954 ◽  
Vol 222 (1150) ◽  
pp. 341-348 ◽  
Keyword(s):  
Heat Flow ◽  
Recent Work ◽  
Sea Water ◽  
Volcanic Rocks ◽  
The Other ◽  
Ocean Floor ◽  
Peridotite Xenoliths ◽  
The Earth ◽  
Southern Rhodesia ◽  
Mohorovičić Discontinuity

Recent work has determined the depth of the Mohorovičić discontinuity at sea and has made it likely that peridotite xenoliths in basaltic volcanic rocks are samples of material from below the discontinuity. It is now possible to produce a hypothetical section showing the transition from a continent to an ocean. This section is consistent with both the seismic and gravity results. The possible reactions of the crust to changes in the total volume of sea water are dis­cussed. It seems possible that the oceans were shallower and the crust thinner in the Archean than they are now. If this were so, some features of the oldest rocks of Canada and Southern Rhodesia could be explained. Three processes are described that might lead to the formation of oceanic ridges; one of these involves tension, one compression and the other quiet tectonic conditions. It is likely that not all ridges are formed in the same way. It is possible that serpentization of olivine by water rising from the interior of the earth plays an important part in producing changes of level in the ocean floor and anomalies in heat flow. Finally, a method of reducing gravity observations at sea is discussed.

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