This chapter reviews the present-day composition of the continental crust, the methods employed to derive these estimates, and the implications of the continental crust composition for the formation of the continents, Earth differentiation, and its geochemical inventories. We review the composition of the upper, middle, and lower continental crust. We then examine the bulk crust composition and the implications of this composition for crust generation and modification processes. Finally, we compare the Earth's crust with those of the other terrestrial planets in our solar system and speculate about what unique processes on Earth have given rise to this unusual crustal distribution.

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Composition of the Continental Crust

Changes in Atmospheric Constituents and in Radiative Forcing

This essential reference for graduate students and researchers provides a unified treatment of earthquakes and faulting as two aspects of brittle tectonics at different timescales. The intimate connection between the two is manifested in their scaling laws and populations, which evolve from fracture growth and interactions between fractures. The connection between faults and the seismicity generated is governed by the rate and state dependent friction laws - producing distinctive seismic styles of faulting and a gamut of earthquake phenomena including aftershocks, afterslip, earthquake triggering, and slow slip events. The third edition of this classic treatise presents a wealth of new topics and new observations. These include slow earthquake phenomena; friction of phyllosilicates, and at high sliding velocities; fault structures; relative roles of strong and seismogenic versus weak and creeping faults; dynamic triggering of earthquakes; oceanic earthquakes; megathrust earthquakes in subduction zones; deep earthquakes; and new observations of earthquake precursory phenomena.

The Mechanics of Earthquakes and Faulting

This chapter should be cited as: Myhre, G., D. Shindell, F.-M. Bréon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, J.-F. Lamarque, D. Lee, B. Mendoza, T. Nakajima, A. Robock, G. Stephens, T. Takemura and H. Zhang, 2013: Anthropogenic and Natural Radiative Forcing. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. Coordinating Lead Authors: Gunnar Myhre (Norway), Drew Shindell (USA)

Anthropogenic and Natural Radiative Forcing

A global plate motion model, named NUVEL-1, which describes current plate motions between 12 rigid plates is described, with special attention given to the method, data, and assumptions used Tectonic implications of the patterns that emerged from the results are discussed It is shown that wide plate boundary zones can form not only within the continental lithosphere but also within the oceanic lithosphere; eg, between the Indian and Australian plates and between the North American and South American plates Results of the model also suggest small but significant diffuse deformation of the oceanic lithosphere, which may be confined to small awkwardly shaped salients of major plates

Current plate motions

High-resolution gravity data from GRAIL have yielded new estimates of the bulk density and thickness of the lunar crust. The bulk density of the highlands crust is 2550 kg m-3. From a comparison with crustal composition measured remotely, this density implies a mean porosity of 12%. With this bulk density and constraints from the Apollo seismic experiment, the average global crustal thickness is found to lie between 34 and 43 km, a value 10 to 20 km less than several previous estimates. Crustal thickness is a central parameter in estimating bulk lunar composition. Estimates of the concentrations of refractory elements in the Moon from heat flow, remote sensing and sample data, and geophysical data fall into two categories: those with refractory element abundances enriched by 50% or more relative to Earth, and those with abundances the same as Earth. Settling this issue has implications for processes operating during lunar formation. The crustal thickness resulting from analysis of GRAIL data is less than several previous estimates. We show here that a refractory-enriched Moon is not required

/pdf/revised-thickness-of-the-lunar-crust-from-grail-data-297ehsyfuo.pdf

Revised Thickness of the Lunar Crust from GRAIL Data: Implications for Lunar Bulk Composition

Seismic Evidence for a Plume Beneath the Galápagos Hotspot

“Science is public knowledge.” [Ziman, 1968] The Union's programs in public outreach and education are poised for further growth as a result of an action of the AGU Council taken at its December meeting.

Among the purposes of the Union laid down in the AGU Statutes are two that motivate and guide our activities aimed at engaging and informing the public. The first purpose of the Union is “to promote the scientific study of Earth, Sun, and the solar system and all of their environments and components and to make the results of such studies available to the public.” An additional stated purpose is “to carry out education and other outreach activities to further the public's understanding of the geophysical sciences.”

State of the union: AGU's public outreach programs to expand

Radar measurements show that the outer core of Mercury is molten, providing insight into the planet's history and the origin of its magnetic field.

https://science.sciencemag.org/content/sci/316/5825/702.full.pdf

Hot News on Mercury's Core

Brett W. Denevi (1), Mark S. Robinson (2), Scott L. Murchie (1), Carolyn M. Ernst (1), Paul K. Byrne (3), Sean C. Solomon, (3) Patrick. N. Peplowski (1). (1) The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA, (2) School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA, (3) Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015, USA. Corresponding author’s email address: Brett.Denevi@jhuapl.edu.

Sean C. Solomon

Papers

Revised Thickness of the Lunar Crust from GRAIL Data: Implications for Lunar Bulk Composition

Seismic Evidence for a Plume Beneath the Galápagos Hotspot

State of the union: AGU's public outreach programs to expand

Hot News on Mercury's Core

The Distribution of Young Plains on Mercury