scholarly journals Towards understanding how surface life can affect interior geological processes: a non-equilibrium thermodynamics approach

2011 ◽  
Vol 2 (1) ◽  
pp. 139-160 ◽  
Author(s):  
J. G. Dyke ◽  
F. Gans ◽  
A. Kleidon
Keyword(s):  
Continental Crust ◽  
Oceanic Crust ◽  
Mantle Convection ◽  
Dynamical Models ◽  
Geological Processes ◽  
The Earth ◽  
Uplift And Erosion ◽  
Life On Earth ◽  
Mantle Temperature ◽  
Non Equilibrium

Abstract. Life has significantly altered the Earth's atmosphere, oceans and crust. To what extent has it also affected interior geological processes? To address this question, three models of geological processes are formulated: mantle convection, continental crust uplift and erosion and oceanic crust recycling. These processes are characterised as non-equilibrium thermodynamic systems. Their states of disequilibrium are maintained by the power generated from the dissipation of energy from the interior of the Earth. Altering the thickness of continental crust via weathering and erosion affects the upper mantle temperature which leads to changes in rates of oceanic crust recycling and consequently rates of outgassing of carbon dioxide into the atmosphere. Estimates for the power generated by various elements in the Earth system are shown. This includes, inter alia, surface life generation of 264 TW of power, much greater than those of geological processes such as mantle convection at 12 TW. This high power results from life's ability to harvest energy directly from the sun. Life need only utilise a small fraction of the generated free chemical energy for geochemical transformations at the surface, such as affecting rates of weathering and erosion of continental rocks, in order to affect interior, geological processes. Consequently when assessing the effects of life on Earth, and potentially any planet with a significant biosphere, dynamical models may be required that better capture the coupled nature of biologically-mediated surface and interior processes.

scholarly journals Assessing life's effects on the interior dynamics of planet Earth using non-equilibrium thermodynamics

2010 ◽  
Vol 1 (1) ◽  
pp. 191-246 ◽  
Author(s):  
J. G. Dyke ◽  
F. Gans ◽  
A. Kleidon
Keyword(s):  
Free Energy ◽  
Boundary Conditions ◽  
Continental Crust ◽  
Oceanic Crust ◽  
Mantle Convection ◽  
Maximum Power ◽  
Earth System ◽  
Equilibrium Thermodynamics ◽  
Non Equilibrium ◽  
Whole Earth

Abstract. Vernadsky described life as the geologic force, while Lovelock noted the role of life in driving the Earth's atmospheric composition to a unique state of thermodynamic disequilibrium. Here, we use these notions in conjunction with thermodynamics to quantify biotic activity as a driving force for geologic processes. Specifically, we explore the hypothesis that biologically-mediated processes operating on the surface of the Earth, such as the biotic enhancement of weathering of continental crust, affect interior processes such as mantle convection and have therefore shaped the evolution of the whole Earth system beyond its surface and atmosphere. We set up three simple models of mantle convection, oceanic crust recycling and continental crust recycling. We describe these models in terms of non-equilibrium thermodynamics in which the generation and dissipation of gradients is central to driving their dynamics and that such dynamics can be affected by their boundary conditions. We use these models to quantify the maximum power that is involved in these processes. The assumption that these processes, given a set of boundary conditions, operate at maximum levels of generation and dissipation of free energy lead to reasonable predictions of core temperature, seafloor spreading rates, and continental crust thickness. With a set of sensitivity simulations we then show how these models interact through the boundary conditions at the mantle-crust and oceanic-continental crust interfaces. These simulations hence support our hypothesis that the depletion of continental crust at the land surface can affect rates of oceanic crust recycling and mantle convection deep within the Earth's interior. We situate this hypothesis within a broader assessment of surface-interior interactions by setting up a work budget of the Earth's interior to compare the maximum power estimates that drive interior processes to the power that is associated with biotic activity. We estimate that the maximum power involved in mantle convection is 12 TW, oceanic crust cycling is 28 TW, and continental uplift is less than 1 TW. By directly utilizing the low entropy nature of solar radiation, photosynthesis generates 215 TW of chemical free energy. This high power associated with life results from the fact that photochemistry is not limited by the low energy that is available from the heating gradients that drive geophysical processes in the interior. We conclude that by utilizing only a small fraction of the generated free chemical energy for geochemical transformations at the surface, life has the potential to substantially affect interior processes, and so the whole Earth system. Consequently, when understanding Earth system processes we may need to adopt a dynamical model schema in which previously fixed boundary conditions become components of a co-evolutionary system.

General discussion

1987 ◽  
Vol 321 (1557) ◽  
pp. 271-273
Keyword(s):  
Mathematical Models ◽  
Continental Crust ◽  
Oceanic Crust ◽  
Continuous Medium ◽  
The Urals ◽  
The Earth ◽  
Scandinavian Caledonides ◽  
Fold Belts ◽  
Normal Thickness

E. V. Artyushkov ( Institute of Physics of the Earth, Moscow, U.S.S.R .). Shortening of the crust has been modelled by compression of a continuous medium. It has also been supposed that compression can start in continental crust of normal thickness. Mathematical models of the same type have recently been used by some other authors. It should be noted that an intense shortening of the crust in fold belts never occurred in such a way. In the main Phanerozoic fold belts (the Urals, Appalachians, Scandinavian Caledonides, the Alpine and Verkhoyansk belts, and others) no era tonic block with a normal continental crust and lithosphere was shortened (Artyushkov & Baer 1983, 1984, 1986). An intense compression took place only in deep basins on oceanic or continental crust. Most oceanic crust disappeared from the surface in the process of subduction. Now the fold belts are mainly built up of a strongly compressed crust of deep basins on continental crust. How can it be proven that this crust was really thin?

What led to episodic subduction during the Archean?

2021 ◽  
Author(s):  
Prasanna Gunawardana ◽  
Gabriele Morra ◽  
Priyadarshi Chowdhury ◽  
Peter Cawood
Keyword(s):  
Mantle Convection ◽  
Tectonic Setting ◽  
Potential Temperature ◽  
Surface Heat ◽  
Surface Velocity ◽  
Plate Tectonic ◽  
The Earth ◽  
Engineering Sciences ◽  
Short Period ◽  
Mantle Temperature

<p>The tectonic regime of the early Earth is crucial to understand how interior and exterior elements of the Earth interacted to make our planet habitable (Cawood et al., 2018). Our understanding of the processes involved is far from complete, particularly about how the switch between non-plate tectonic and plate tectonic regimes may have happened during the Archean. In this study, we investigate how Archean subduction events (albeit isolated and intermittent) may have evolved within/from a stagnant-lid regime. We perform 2D numerical modelling of mantle convection (using Underworld2) under a range of conditions appropriate for the early-to-mid Archean Earth including hotter mantle potential temperature and internal heat production. Using the models, we evaluate how the mantle temperature and viscosity, buoyancy force, surface heat flow and surface velocity may have evolved over a duration of ~800-1000 million years.</p><p>Our models indicate that lithospheric drips are an efficient way of releasing a large amount of heat from the Earth’s surface over a short period of time. Repeated occurrences of dripping events result in average mantle temperature gradually decreasing. Concomitant with this thermal evolution, the drip dimensions grew to form large, symmetrical drips as well as occasional, asymmetric subduction type events. The subduction events lead to large-scale resurfacing of the lithosphere. We surmise that the decreasing of average mantle temperature: (1) increases the temperature dependent viscosity of the mantle, and 2) decreases the buoyancy forces of mantle convection. Both these factors lower the convective vigour and increases the lithospheric (the upper thermal boundary layer) thickness via decreasing the effective Rayleigh number. These changes in the lithosphere-asthenosphere system facilitate the transition from a dripping dominated regime to a mix of large-dripping and intermittent subduction regime over a period of ~1 billon years. This change in tectonic setting is predicted to alter surface velocity patterns, surface heat flux and production rate of felsic magmas, which allows the modelling results can be tested against the rock record.</p><p>Reference</p><p>Cawood, P. A., Hawkesworth, C. J., Pisarevsky, S. A., Dhuime, B., Capitanio, F. A., and Nebel, O., 2018, Geological archive of the onset of plate tectonics: Philosophical transactions. Series A, Mathematical, physical, and engineering sciences, v. 376, no. 2132.</p>

TO STRATIGRAPHY AND GEODYNAMICS ZILAIR SEDIMENTS IN THE SOUTHERN URALS

2021 ◽  
Vol 0 (3) ◽  
pp. 77-88
Author(s):  
T.T. KAZANTSEVA ◽  
Keyword(s):  
Conceptual Framework ◽  
Continental Crust ◽  
Southern Urals ◽  
Earth’S Crust ◽  
Spatial Relationships ◽  
The Southern Urals ◽  
Geological Processes ◽  
The Earth ◽  
Earth's Crust ◽  
The Relationship

It is known that the upper shell of our planet is the earth's crust, which is different in composition on the continents and in the oceans. The composition of the continental crust is predominantly sialic, and the oceanic one is simatic. The capacity of the first is within 35-70 km, the second is close to 5-12. The formation of any type of the earth's crust is determined by the participation of specific geological processes, causal relationships of matter and geodynamics, which is justified by researchers on the basis of well-proven facts and judgments. The concepts used must be specific, in accordance with well-known definitions, such as: stratigraphy is a branch of geology that studies «the formation of rocks in their primary spatial relationships», and geodynamics is «a branch of geology that studies the forces and processes in the crust, mantle and core of the Earth, deep and surface movements of masses in time and space» [1]. The use of the conceptual framework and the study of numerous facts allow us to confidently identify the sequence of connections and the reasons for the relationship.

scholarly journals Crustal evolution and mantle dynamics through Earth history

2018 ◽  
Vol 376 (2132) ◽  
pp. 20170408 ◽  
Author(s):  
Jun Korenaga
Keyword(s):  
Continental Crust ◽  
Mantle Convection ◽  
Plate Tectonics ◽  
Indirect Evidence ◽  
Quantitative Model ◽  
Early Earth ◽  
Mantle Dynamics ◽  
Earth History ◽  
Geological Processes ◽  
Earth Dynamics

Resolving the modes of mantle convection through Earth history, i.e. when plate tectonics started and what kind of mantle dynamics reigned before, is essential to the understanding of the evolution of the whole Earth system, because plate tectonics influences almost all aspects of modern geological processes. This is a challenging problem because plate tectonics continuously rejuvenates Earth's surface on a time scale of about 100 Myr, destroying evidence for its past operation. It thus becomes essential to exploit indirect evidence preserved in the buoyant continental crust, part of which has survived over billions of years. This contribution starts with an in-depth review of existing models for continental growth. Growth models proposed so far can be categorized into three types: crust-based, mantle-based and other less direct inferences, and the first two types are particularly important as their difference reflects the extent of crustal recycling, which can be related to subduction. Then, a theoretical basis for a change in the mode of mantle convection in the Precambrian is reviewed, along with a critical appraisal of some popular notions for early Earth dynamics. By combining available geological and geochemical observations with geodynamical considerations, a tentative hypothesis is presented for the evolution of mantle dynamics and its relation to surface environment; the early onset of plate tectonics and gradual mantle hydration are responsible not only for the formation of continental crust but also for its preservation as well as its emergence above sea level. Our current understanding of various material properties and elementary processes is still too premature to build a testable, quantitative model for this hypothesis, but such modelling efforts could potentially transform the nature of the data-starved early Earth research by quantifying the extent of preservation bias.This article is part of a discussion meeting issue ‘Earth dynamics and the development of plate tectonics’.

Forecast of manifestations of dangerous geological processes in Dnipropetrovsk with the use of methods of aerospace remote sensing of the Earth

2004 ◽  
Vol 10 (5-6) ◽  
pp. 194-196
Author(s):  
V.I. Voloshin ◽  
◽  
A.S. Levenko ◽  
N.N. Peremetchik ◽  
◽  
...  
Keyword(s):  
Remote Sensing ◽  
Geological Processes ◽  
The Earth

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.

Ups and Downs

2018 ◽  
Author(s):  
Roy Livermore
Keyword(s):  
Mantle Convection ◽  
Laboratory Experiments ◽  
Inner Core ◽  
Computer Modelling ◽  
Great Depth ◽  
New Horizons ◽  
The Core ◽  
The Earth ◽  
The World ◽  
The 1960S

Despite the dumbing-down of education in recent years, it would be unusual to find a ten-year-old who could not name the major continents on a map of the world. Yet how many adults have the faintest idea of the structures that exist within the Earth? Understandably, knowledge is limited by the fact that the Earth’s interior is less accessible than the surface of Pluto, mapped in 2016 by the NASA New Horizons spacecraft. Indeed, Pluto, 7.5 billion kilometres from Earth, was discovered six years earlier than the similar-sized inner core of our planet. Fortunately, modern seismic techniques enable us to image the mantle right down to the core, while laboratory experiments simulating the pressures and temperatures at great depth, combined with computer modelling of mantle convection, help identify its mineral and chemical composition. The results are providing the most rapid advances in our understanding of how this planet works since the great revolution of the 1960s.

Sign in / Sign up

Export Citation Format

Share Document