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Michael Brown - One of the best experts on this subject based on the ideXlab platform.
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Plate Tectonics and the Archean Earth
Annual Review of Earth and Planetary Sciences, 2020Co-Authors: Michael Brown, Tim E. Johnson, Nicholas J. GardinerAbstract:If we accept that a critical condition for Plate Tectonics is the creation and maintenance of a global network of narrow boundaries separating multiple Plates, then to argue for Plate Tectonics dur...
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Metamorphism and the evolution of Plate Tectonics.
Nature, 2019Co-Authors: Robert M. Holder, Michael Brown, Daniel R. Viete, Tim E. JohnsonAbstract:Earth’s mantle convection, which facilitates planetary heat loss, is manifested at the surface as present-day Plate Tectonics1. When Plate Tectonics emerged and how it has evolved through time are two of the most fundamental and challenging questions in Earth science1–4. Metamorphic rocks—rocks that have experienced solid-state mineral transformations due to changes in pressure (P) and temperature (T)—record periods of burial, heating, exhumation and cooling that reflect the tectonic environments in which they formed5,6. Changes in the global distribution of metamorphic (P, T) conditions in the continental crust through time might therefore reflect the secular evolution of Earth’s tectonic processes. On modern Earth, convergent Plate margins are characterized by metamorphic rocks that show a bimodal distribution of apparent thermal gradients (temperature change with depth; parameterized here as metamorphic T/P) in the form of paired metamorphic belts5, which is attributed to metamorphism near (low T/P) and away from (high T/P) subduction zones5,6. Here we show that Earth’s modern Plate tectonic regime has developed gradually with secular cooling of the mantle since the Neoarchaean era, 2.5 billion years ago. We evaluate the emergence of bimodal metamorphism (as a proxy for secular change in Plate Tectonics) using a statistical evaluation of the distributions of metamorphic T/P through time. We find that the distribution of metamorphic T/P has gradually become wider and more distinctly bimodal from the Neoarchaean era to the present day, and the average metamorphic T/P has decreased since the Palaeoproterozoic era. Our results contrast with studies that inferred an abrupt transition in tectonic style in the Neoproterozoic era (about 0.7 billion years ago1,7,8) or that suggested that modern Plate Tectonics has operated since the Palaeoproterozoic era (about two billion years ago9–12) at the latest. Variability in Earth’s thermal gradients, recorded by metamorphic rocks through time, shows that Earth’s modern Plate Tectonics developed gradually since the Neoarchaean era, three billion years ago.
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surface erosion events controlled the evolution of Plate Tectonics on earth
Nature, 2019Co-Authors: S V Sobolev, Michael BrownAbstract:Plate Tectonics is among the most important geological processes on Earth, but its emergence and evolution remain unclear. Here we extrapolate models of present-day Plate Tectonics to the past and propose that since about three billion years ago the rise of continents and the accumulation of sediments at continental edges and in trenches has provided lubrication for the stabilization of subduction and has been crucial in the development of Plate Tectonics on Earth. We conclude that the two largest surface erosion and subduction lubrication events occurred after the Palaeoproterozoic Huronian global glaciations (2.45 to 2.2 billion years ago), leading to the formation of the Columbia supercontinent, and after the Neoproterozoic ‘snowball’ Earth glaciations (0.75 to 0.63 billion years ago). The snowball Earth event followed the ‘boring billion’—a period of reduced Plate tectonic activity about 1.75 to 0.75 billion years ago that was probably caused by a shortfall of sediments in trenches—and it kick-started the modern episode of active Plate Tectonics. The rise of continents and the accumulation of sediments in trenches since about three billion years ago has had a crucial role in the emergence and evolution of Plate Tectonics on Earth.
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surface erosion events controlled the evolution of Plate Tectonics on earth
Nature, 2019Co-Authors: Stephan V. Sobolev, Michael BrownAbstract:Plate Tectonics is among the most important geological processes on Earth, but its emergence and evolution remain unclear. Here we extrapolate models of present-day Plate Tectonics to the past and propose that since about three billion years ago the rise of continents and the accumulation of sediments at continental edges and in trenches has provided lubrication for the stabilization of subduction and has been crucial in the development of Plate Tectonics on Earth. We conclude that the two largest surface erosion and subduction lubrication events occurred after the Palaeoproterozoic Huronian global glaciations (2.45 to 2.2 billion years ago), leading to the formation of the Columbia supercontinent, and after the Neoproterozoic ‘snowball’ Earth glaciations (0.75 to 0.63 billion years ago). The snowball Earth event followed the ‘boring billion’—a period of reduced Plate tectonic activity about 1.75 to 0.75 billion years ago that was probably caused by a shortfall of sediments in trenches—and it kick-started the modern episode of active Plate Tectonics.
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Earth dynamics and the development of Plate Tectonics
Philosophical transactions. Series A Mathematical physical and engineering sciences, 2018Co-Authors: Chris J. Hawkesworth, Michael BrownAbstract:This volume brings together contributions from the Royal Society Discussion Meeting on ‘Earth dynamics and the development of Plate Tectonics' held in March 2018. Other planets in the Solar System do not exhibit Plate Tectonics, so why does it occur on Earth, how did it develop and when did Earth adopt this tectonic regime? In evaluating evidence from the geological record, it is critical to distinguish between local and global phenomena in a discussion of the why, how and when of the transition to Plate Tectonics on Earth. Thus, evidence of local or episodic subduction in the geological record, for example, does not necessarily provide evidence for the development of a sustainable global network of mobile belts that forms the basis for a mosaic of Plates. The tectonic regime at any point in the evolution of a planet appears to depend on the initial conditions set by crystallization of the last magma ocean. These conditions determine the thermal state—‘hot’ or ‘cold’—at the start of sub-solidus mantle convection, which is subsequently driven by the relative contributions of basal and internal heating to the mantle through time. Plate Tectonics is linked to the ability of mantle convection to form Plate boundaries, which requires localized weakening of the lithospheric lid. How and when did this become possible? Consideration of the tectonic regime on Venus, which may be an analogue for the early tectonic development of Earth, evidence from the rock record, rock deformation experiments, geodynamic models extrapolated back to the thermal conditions appropriate to the Archaean, and geochemical models for the development and growth of the continental crust have led to the currently popular view that Plate Tectonics developed from a stagnant lid regime. However, if mantle convection is able to form weak Plate boundaries at the higher mantle temperatures expected during the …
Jun Korenaga - One of the best experts on this subject based on the ideXlab platform.
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Plate Tectonics: Metamorphic myth
Nature Geoscience, 2015Co-Authors: Jun KorenagaAbstract:Clear evidence for subduction-induced metamorphism, and thus the operation of Plate Tectonics on the ancient Earth has been lacking. Theoretical calculations indicate that we may have been looking for something that cannot exist.
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Initiation and Evolution of Plate Tectonics on Earth: Theories and Observations
Annual Review of Earth and Planetary Sciences, 2013Co-Authors: Jun KorenagaAbstract:The inception of Plate Tectonics on Earth and its subsequent evolution are discussed on the basis of theoretical considerations and observational constraints. The likelihood of Plate Tectonics in the past depends on what mechanism is responsible for the relatively constant surface heat flux that is indicated by the likely thermal history of Earth. The continuous operation of Plate Tectonics throughout Earth's history is possible if, for example, the strength of convective stress in the mantle is affected by the gradual subduction of surface water. Various geological indicators for the emergence of Plate Tectonics are evaluated from a geodynamical perspective, and they invariably involve certain implicit assumptions about mantle dynamics, which are either demonstrably wrong or yet to be explored. The history of Plate Tectonics is suggested to be intrinsically connected to the secular evolution of the atmosphere, through sea-level changes caused by ocean-mantle interaction.
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Plate Tectonics and planetary habitability: current status and future challenges
Annals of the New York Academy of Sciences, 2012Co-Authors: Jun KorenagaAbstract: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.
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Thermal evolution with a hydrating mantle and the initiation of Plate Tectonics in the early Earth
Journal of Geophysical Research, 2011Co-Authors: Jun KorenagaAbstract:[1] The net influx of water into the deep mantle by Plate Tectonics has been poorly constrained because it is difficult to quantify how efficiently subducting slabs are devolatilized on a global scale. The significance of deep water cycle in the Earth history is similarly ambiguous because it depends critically on when Plate Tectonics started and how it evolved through time. Here I show that, using the new scaling of Plate-tectonic convection based on fully dynamic calculations, the thermal evolution of Earth consistent with geochemical, petrological, and geological data requires continuous mantle hydration since the early Earth, with the net water influx of ∼2–3 × 1014 g yr−1. A drier mantle in the Hadean and Archean is suggested to help the initiation of Plate Tectonics by reducing the viscosity contrast between lithosphere and asthenosphere. As an increase in the vigor of Plate Tectonics with time would encourage global marine inundation, the slow intake of surface water by the convecting mantle is essential to maintain the continental freeboard.
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ON THE LIKELIHOOD OF Plate Tectonics ON SUPER-EARTHS: DOES SIZE MATTER?
The Astrophysical Journal, 2010Co-Authors: Jun KorenagaAbstract:The operation of Plate Tectonics on Earth is essential to modulate its atmospheric composition over geological time and is thus commonly believed to be vital for planetary habitability at large. It has been suggested that Plate Tectonics is very likely for super-Earths, with or without surface water, because a planet with a larger mass tends to have sufficient convective stress to escape from the mode of stagnant-lid convection. Here, this suggestion is revisited on the basis of the recently developed scaling laws of Plate-tectonic convection, which indicate that the planetary size plays a rather minor role and that the likelihood of Plate Tectonics is controlled largely by the presence of surface water.
Amaury H. M. J. Triaud - One of the best experts on this subject based on the ideXlab platform.
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The ability of significant tidal stress to initiate Plate Tectonics
Icarus, 2019Co-Authors: J. J. Zanazzi, Amaury H. M. J. TriaudAbstract:Abstract Plate Tectonics is a geophysical process currently unique to Earth, has an important role in regulating the Earth's climate, and may be better understood by identifying rocky planets outside our solar system with tectonic activity. The key criterion for whether or not Plate Tectonics may occur on a terrestrial planet is if the stress on a planet's lithosphere from mantle convection may overcome the lithosphere's yield stress. Although many rocky exoplanets closely orbiting their host stars have been detected, all studies to date of Plate Tectonics on exoplanets have neglected tidal stresses in the planet's lithosphere. Modeling a rocky exoplanet as a constant density, homogeneous, incompressible sphere, we show the tidal stress from the host star acting on close-in planets may become comparable to the stress on the lithosphere from mantle convection. Tidal stress of this magnitude may aid mantle convection stress in subduction of Plates, or drive the subduction of Plates without the need for mantle convective stresses. We also show that tidal stresses from planet-planet interactions are unlikely to be significant for Plate Tectonics, but may be strong enough to trigger Earthquakes. Our work may imply planets orbiting close to their host stars are more likely to experience Plate Tectonics, with implications for exoplanetary geophysics and habitability. We produce a list of detected rocky exoplanets under the most intense stresses. Atmospheric and topographic observations may confirm our predictions in the near future. Investigations of planets with significant tidal stress can not only lead to observable parameters linked to the presence of active Plate Tectonics, but may also be used as a tool to test theories on the main driving force behind tectonic activity.
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Initiation of Plate Tectonics on Exoplanets with Significant Tidal Stress
2017Co-Authors: J. J. Zanazzi, Amaury H. M. J. TriaudAbstract:Plate Tectonics is a geophysical process currently unique to Earth, has an important role in regulating the Earth's climate, and may be better understood by identifying rocky planets outside our solar system with tectonic activity. The key criterion for whether or not Plate Tectonics may occur on a terrestrial planet is if the stress on a planet's lithosphere from mantle convection may overcome the lithosphere's yield stress. Although many rocky exoplanets closely orbiting their host stars have been detected, all studies to date of Plate Tectonics on exoplanets have neglected tidal stresses in the planet's lithosphere. Modeling a rocky exoplanet as a constant density, homogeneous, incompressible sphere, we show the tidal stress from the host star acting on close-in planets may become comparable to the stress on the lithosphere from mantle convection. We also show that tidal stresses from planet-planet interactions are unlikely to be significant for Plate Tectonics, but may be strong enough to trigger Earthquakes. Our work may imply planets orbiting close to their host stars are more likely to experience Plate Tectonics, with implications for exoplanetary geophysics and habitability. We produce a list of detected rocky exoplanets under the most intense stresses. Atmospheric and topographic observations may confirm our predictions in the near future. Investigations of planets with significant tidal stress can not only lead to observable parameters linked to the presence of active Plate Tectonics, but may also be used as a tool to test theories on the main driving force behind tectonic activity.
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The Ability of Significant Tidal Stress to Initiate Plate Tectonics
arXiv: Earth and Planetary Astrophysics, 2017Co-Authors: J. J. Zanazzi, Amaury H. M. J. TriaudAbstract:Plate Tectonics is a geophysical process currently unique to Earth, has an important role in regulating the Earth's climate, and may be better understood by identifying rocky planets outside our solar system with tectonic activity. The key criterion for whether or not Plate Tectonics may occur on a terrestrial planet is if the stress on a planet's lithosphere from mantle convection may overcome the lithosphere's yield stress. Although many rocky exoplanets closely orbiting their host stars have been detected, all studies to date of Plate Tectonics on exoplanets have neglected tidal stresses in the planet's lithosphere. Modeling a rocky exoplanet as a constant density, homogeneous, incompressible sphere, we show the tidal stress from the host star acting on close-in planets may become comparable to the stress on the lithosphere from mantle convection. We also show that tidal stresses from planet-planet interactions are unlikely to be significant for Plate Tectonics, but may be strong enough to trigger Earthquakes. Our work may imply planets orbiting close to their host stars are more likely to experience Plate Tectonics, with implications for exoplanetary geophysics and habitability. We produce a list of detected rocky exoplanets under the most intense stresses. Atmospheric and topographic observations may confirm our predictions in the near future. Investigations of planets with significant tidal stress can not only lead to observable parameters linked to the presence of active Plate Tectonics, but may also be used as a tool to test theories on the main driving force behind tectonic activity.
J. J. Zanazzi - One of the best experts on this subject based on the ideXlab platform.
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The ability of significant tidal stress to initiate Plate Tectonics
Icarus, 2019Co-Authors: J. J. Zanazzi, Amaury H. M. J. TriaudAbstract:Abstract Plate Tectonics is a geophysical process currently unique to Earth, has an important role in regulating the Earth's climate, and may be better understood by identifying rocky planets outside our solar system with tectonic activity. The key criterion for whether or not Plate Tectonics may occur on a terrestrial planet is if the stress on a planet's lithosphere from mantle convection may overcome the lithosphere's yield stress. Although many rocky exoplanets closely orbiting their host stars have been detected, all studies to date of Plate Tectonics on exoplanets have neglected tidal stresses in the planet's lithosphere. Modeling a rocky exoplanet as a constant density, homogeneous, incompressible sphere, we show the tidal stress from the host star acting on close-in planets may become comparable to the stress on the lithosphere from mantle convection. Tidal stress of this magnitude may aid mantle convection stress in subduction of Plates, or drive the subduction of Plates without the need for mantle convective stresses. We also show that tidal stresses from planet-planet interactions are unlikely to be significant for Plate Tectonics, but may be strong enough to trigger Earthquakes. Our work may imply planets orbiting close to their host stars are more likely to experience Plate Tectonics, with implications for exoplanetary geophysics and habitability. We produce a list of detected rocky exoplanets under the most intense stresses. Atmospheric and topographic observations may confirm our predictions in the near future. Investigations of planets with significant tidal stress can not only lead to observable parameters linked to the presence of active Plate Tectonics, but may also be used as a tool to test theories on the main driving force behind tectonic activity.
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Initiation of Plate Tectonics on Exoplanets with Significant Tidal Stress
2017Co-Authors: J. J. Zanazzi, Amaury H. M. J. TriaudAbstract:Plate Tectonics is a geophysical process currently unique to Earth, has an important role in regulating the Earth's climate, and may be better understood by identifying rocky planets outside our solar system with tectonic activity. The key criterion for whether or not Plate Tectonics may occur on a terrestrial planet is if the stress on a planet's lithosphere from mantle convection may overcome the lithosphere's yield stress. Although many rocky exoplanets closely orbiting their host stars have been detected, all studies to date of Plate Tectonics on exoplanets have neglected tidal stresses in the planet's lithosphere. Modeling a rocky exoplanet as a constant density, homogeneous, incompressible sphere, we show the tidal stress from the host star acting on close-in planets may become comparable to the stress on the lithosphere from mantle convection. We also show that tidal stresses from planet-planet interactions are unlikely to be significant for Plate Tectonics, but may be strong enough to trigger Earthquakes. Our work may imply planets orbiting close to their host stars are more likely to experience Plate Tectonics, with implications for exoplanetary geophysics and habitability. We produce a list of detected rocky exoplanets under the most intense stresses. Atmospheric and topographic observations may confirm our predictions in the near future. Investigations of planets with significant tidal stress can not only lead to observable parameters linked to the presence of active Plate Tectonics, but may also be used as a tool to test theories on the main driving force behind tectonic activity.
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The Ability of Significant Tidal Stress to Initiate Plate Tectonics
arXiv: Earth and Planetary Astrophysics, 2017Co-Authors: J. J. Zanazzi, Amaury H. M. J. TriaudAbstract:Plate Tectonics is a geophysical process currently unique to Earth, has an important role in regulating the Earth's climate, and may be better understood by identifying rocky planets outside our solar system with tectonic activity. The key criterion for whether or not Plate Tectonics may occur on a terrestrial planet is if the stress on a planet's lithosphere from mantle convection may overcome the lithosphere's yield stress. Although many rocky exoplanets closely orbiting their host stars have been detected, all studies to date of Plate Tectonics on exoplanets have neglected tidal stresses in the planet's lithosphere. Modeling a rocky exoplanet as a constant density, homogeneous, incompressible sphere, we show the tidal stress from the host star acting on close-in planets may become comparable to the stress on the lithosphere from mantle convection. We also show that tidal stresses from planet-planet interactions are unlikely to be significant for Plate Tectonics, but may be strong enough to trigger Earthquakes. Our work may imply planets orbiting close to their host stars are more likely to experience Plate Tectonics, with implications for exoplanetary geophysics and habitability. We produce a list of detected rocky exoplanets under the most intense stresses. Atmospheric and topographic observations may confirm our predictions in the near future. Investigations of planets with significant tidal stress can not only lead to observable parameters linked to the presence of active Plate Tectonics, but may also be used as a tool to test theories on the main driving force behind tectonic activity.
T. Spohn - One of the best experts on this subject based on the ideXlab platform.
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early Plate Tectonics versus single Plate Tectonics on mars evidence from magnetic field history and crust evolution
Journal of Geophysical Research, 2003Co-Authors: Doris Breuer, T. SpohnAbstract:[1] The consequences of an early epoch of Plate Tectonics on Mars followed by single-Plate Tectonics with stagnant lid mantle convection on both crust production and magnetic field generation have been studied with parameterized mantle convection models. Thermal history models with parameterized mantle convection, not being dynamo models, can provide necessary, but not sufficient, conditions for dynamo action. It is difficult to find early Plate Tectonics models that can reasonably explain crust formation, as is required by geological and geophysical observations, and allow an early magnetic field that is widely accepted as the cause for the observed magnetic anomalies. Dating of crust provinces and topography and gravity data suggest a crust production rate monotonically declining through the Noachian and Hesperian and a present-day crust thickness of more than 50 km. Plate Tectonics cools the mantle and core efficiently, and the core may easily generate an early magnetic field. Given a sufficiently weak mantle rheology, Plate Tectonics can explain a field even if the core is not initially superheated with respect to the mantle. Because the crust production rate is proportional to temperature, however, an early efficient cooling will frustrate later crust production and therefore cannot explain, for example, the absence of prominent magnetic anomalies in the northern crustal province and the northern volcanic plains in the Early Hesperian. Voluminous crust formation following Plate Tectonics is possible if Plate Tectonics heat transfer is inefficient but then the crust growth rate has a late peak (about 2 Ga b.p.), which is not observed. These models also require a substantial initial superheating of the core to allow a dynamo. If one accepts the initial superheating, then, as we will show, a simple thermal evolution model with monotonic cooling of the planet due to stagnant lid mantle convection underneath a single Plate throughout the evolution can better reconcile early crust formation and magnetic field generation.
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Early Plate Tectonics versus single‐Plate Tectonics on Mars: Evidence from magnetic field history and crust evolution
Journal of Geophysical Research, 2003Co-Authors: Doris Breuer, T. SpohnAbstract:[1] The consequences of an early epoch of Plate Tectonics on Mars followed by single-Plate Tectonics with stagnant lid mantle convection on both crust production and magnetic field generation have been studied with parameterized mantle convection models. Thermal history models with parameterized mantle convection, not being dynamo models, can provide necessary, but not sufficient, conditions for dynamo action. It is difficult to find early Plate Tectonics models that can reasonably explain crust formation, as is required by geological and geophysical observations, and allow an early magnetic field that is widely accepted as the cause for the observed magnetic anomalies. Dating of crust provinces and topography and gravity data suggest a crust production rate monotonically declining through the Noachian and Hesperian and a present-day crust thickness of more than 50 km. Plate Tectonics cools the mantle and core efficiently, and the core may easily generate an early magnetic field. Given a sufficiently weak mantle rheology, Plate Tectonics can explain a field even if the core is not initially superheated with respect to the mantle. Because the crust production rate is proportional to temperature, however, an early efficient cooling will frustrate later crust production and therefore cannot explain, for example, the absence of prominent magnetic anomalies in the northern crustal province and the northern volcanic plains in the Early Hesperian. Voluminous crust formation following Plate Tectonics is possible if Plate Tectonics heat transfer is inefficient but then the crust growth rate has a late peak (about 2 Ga b.p.), which is not observed. These models also require a substantial initial superheating of the core to allow a dynamo. If one accepts the initial superheating, then, as we will show, a simple thermal evolution model with monotonic cooling of the planet due to stagnant lid mantle convection underneath a single Plate throughout the evolution can better reconcile early crust formation and magnetic field generation.
