Annual Review of Earth and Planetary Sciences - Volume 42, 2014
Volume 42, 2014
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Hydrogeomorphic Effects of Explosive Volcanic Eruptions on Drainage Basins*
Vol. 42 (2014), pp. 469–507More LessExplosive eruptions can severely disturb landscapes downwind or downstream of volcanoes by damaging vegetation and depositing large volumes of erodible fragmental material. As a result, fluxes of water and sediment in affected drainage basins can increase dramatically. System-disturbing processes associated with explosive eruptions include tephra fall, pyroclastic density currents, debris avalanches, and lahars—processes that have greater impacts on water and sediment discharges than lava-flow emplacement. Geo-morphic responses to such disturbances can extend far downstream, persist for decades, and be hazardous. The severity of disturbances to a drainage basin is a function of the specific volcanic process acting, as well as distance from the volcano and magnitude of the eruption. Postdisturbance unit-area sediment yields are among the world's highest; such yields commonly result in abundant redeposition of sand and gravel in distal river reaches, which causes severe channel aggradation and instability. Response to volcanic disturbance can result in socioeconomic consequences more damaging than the direct impacts of the eruption itself.
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Seafloor Geodesy
Vol. 42 (2014), pp. 509–534More LessSeafloor geodetic techniques allow for measurements of crustal deformation over the ∼70% of Earth's surface that is inaccessible to the standard tools of tectonic geodesy. Precise underwater measurement of position, displacement, strain, and gravity poses technical, logistical, and cost challenges. Nonetheless, acoustic ranging; pressure sensors; underwater strain-, tilt- and gravimeters; and repeat multibeam sonar and seismic measurements are able to capture small-scale or regional deformation with approximately centimeter-level precision. Pioneering seafloor geodetic measurements offshore Japan, Cascadia, and Hawaii have substantially contributed to advances in our understanding of the motion and deformation of oceanic tectonic plates, earthquake cycle deformation in subduction zones, and the deformation of submarine volcanoes. Nontectonic deformation related to down-slope mass movement and underwater extraction of hydrocarbons or other resources represent other important targets. Recent technological advances promise further improvements in precision as well as the development of smaller, more autonomous, and less costly seafloor geodetic systems.
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Particle Geophysics
Vol. 42 (2014), pp. 535–549More LessGeophysics research has long been dominated by classical mechanics, largely disregarding the potential of particle physics to augment existing techniques. The purpose of this article is to review recent progress in probing Earth's interior with muons and neutrinos. Existing results for various volcanological targets are reviewed. Geoneutrinos are also highlighted as examples in which the neutrino probes elucidate the composition of Earth's deep interior. Particle geophysics has the potential to serve as a useful paradigm to transform our understanding of Earth as dramatically as the X-ray transformed our understanding of medicine and the body.
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Impact Origin of the Moon?
Vol. 42 (2014), pp. 551–578More LessEarth formed in a series of giant impacts, and the last one made the Moon. This idea, an edifice of post-Apollo science, can explain the Moon's globally melted silicate composition, its lack of water and iron, and its anomalously large mass and angular momentum. But the theory is seriously called to question by increasingly detailed geochemical analysis of lunar rocks. Lunar samples should be easily distinguishable from Earth, because the Moon derives mostly from the impacting planet, in standard models of the theory. But lunar rocks are the same as Earth in O, Ti, Cr, W, K, and other species, to measurement precision. Some regard this as a repudiation of the theory; others say it wants a reformation. Ideas put forward to salvage or revise it are evaluated, alongside their relationships to past models and their implications for planet formation and Earth.
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Evolution of Neogene Mammals in Eurasia: Environmental Forcing and Biotic Interactions
Vol. 42 (2014), pp. 579–604More LessThe relative weights of physical forcing and biotic interaction as drivers of evolutionary change have been debated in evolutionary theory. The recent finding that species, genera, clades, and chronofaunas all appear to exhibit a symmetrical pattern of waxing and waning lends support to the view that biotic interactions shape the history of life. Yet, there is similarly abundant evidence that these primary units of biological evolution arise and wane in coincidence with major climatic change. We review these patterns and the process-level explanations offered for them. We also propose a tentative synthesis, characterized by interdependence between physical forcing and biotic interactions. We suggest that species with evolutionary novelties arise predominantly in “species factories” that develop under harsh environmental conditions, under dominant physical forcing, whereas exceptionally mild environments give rise to “oases in the desert,” characterized by strong competition and survival of relics.
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Planetary Reorientation
Vol. 42 (2014), pp. 605–634More LessPlanetary bodies can undergo reorientation due to mass redistribution associated with internal or external processes such as convection or impacts. Mass redistribution produces perturbations to the inertia tensor, and the planet must reorient to adjust to the new orientation of the maximum principal axis. The amount of reorientation depends on the competing sizes of the applied load and the remnant bulge. For tidally deformed satellites in synchronous rotation, the slow rotation and correspondingly small remnant bulge makes them prone to reorientation. Reorientation can generate gravity and topography perturbations and large tectonic stresses. Observational constraints based on gravity, tectonic, and paleomagnetic data suggest that many Solar System bodies appear to have undergone significant reorientation.
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Thermal Maturation of Gas Shale Systems
Vol. 42 (2014), pp. 635–651More LessShale gas systems serve as sources, reservoirs, and seals for unconventional natural gas accumulations. These reservoirs bring numerous challenges to geologists and petroleum engineers in reservoir characterization, most notably because of their heterogeneous character due to depositional and diagenetic processes but also because of their constituent rocks' fine-grained nature and small pore size—much smaller than in conventional sandstone and carbonate reservoirs. Significant advances have recently been achieved in unraveling the gaseous hydrocarbon generation and retention processes that occur within these complex systems. In addition, cutting-edge characterization technologies have allowed precise documentation of the spatial variability in chemistry and structure of thermally mature organic-rich shales at the submicrometer scale, revealing the presence of geochemical heterogeneities within overmature gas shale samples and, notably, the presence of nanoporous pyrobitumen. Such research advances will undoubtedly lead to improved performance, producibility, and modeling of such strategic resources at the reservoir scale.
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Global Positioning System (GPS) and GPS-Acoustic Observations: Insight into Slip Along the Subduction Zones Around Japan
Vol. 42 (2014), pp. 653–674More LessThe global positioning system (GPS) is one of the most powerful tools available for observation of Earth's surface deformation. In particular, coseismic, postseismic, slow transient, and interseismic deformation have all been observed globally by GPS over the past two decades, especially in subduction zones. Moreover, GPS-acoustic techniques have been developed for practical use in the past decade, allowing observation of offshore deformation immediately above slip regions. Here, we describe the application of GPS and GPS-acoustic observations to the detection of deformation due to plate boundary slip for interplate earthquakes as well as afterslip and slow slip events in subduction zones around Japan, where geodetic data coverage is particularly dense. The data demonstrate temporally variable strain accumulation in the source region of the 2011 Mw 9.0 Tohoku-oki earthquake, and observation of the huge slip of the Tohoku-oki earthquake near the trench using GPS-acoustic methods has considerably advanced our knowledge of stress release and accumulation in this subduction zone.
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On Dinosaur Growth
Vol. 42 (2014), pp. 675–697More LessDespite nearly two centuries of investigation, a comprehensive understanding of dinosaur biology has proven intractable. The recent development of means to study tissue-level growth, age these animals, and make growth curves has revolutionized our knowledge of dinosaur lives. From such data it is now understood that dinosaurs grew both disruptively and determinately; that they rarely if ever exceeded a century in age; that they became giants through accelerated growth and dwarfed through truncated development; that they were likely endothermic, sexually matured like crocodiles, and showed survivorship like populations of large mammals; and that basal birds retained dinosaurian physiology.
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Diamond Formation: A Stable Isotope Perspective
Vol. 42 (2014), pp. 699–732More LessPrimarily on the basis of C, N, S, and O stable isotope systematics, this article reviews recent achievements in understanding diamond formation and growth in Earth's mantle. Diamond is a metasomatic mineral that results from either the reduction or oxidation of mobile C-bearing liquids (fluids or melts) that intrude preexisting lithologies (eclogites, peridotites, and metamorphic rocks). This process seems ubiquitous, as it occurs over a large range of depths and extends through time. Diamond-forming carbon derives mainly from the convective asthenosphere. Most of its isotopic anomalies reflect fractionation processes in the lithospheric mantle, which are attributed to diamond precipitation itself and/or a mineralogical control occurring prior to diamond precipitation. Evidence for a mineralogical control would be the decoupling of the 15N/14N ratios in eclogitic diamond from other tracers of subduction in inclusions in the same diamond. C isotope anomalies related to subduction are rare and are probably best seen in diamonds from the transition zone.
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Organosulfur Compounds: Molecular and Isotopic Evolution from Biota to Oil and Gas
Vol. 42 (2014), pp. 733–768More LessOrganosulfur compounds (OSCs) play important roles in the formation, preservation, and thermal degradation of sedimentary organic matter and the associated petroleum generation. Improved analytical techniques for S isotope analysis have recently enhanced our understanding of the mechanisms for OSC formation and maturation and their associated S isotope distributions. The close interaction of OSCs with inorganic S species throughout their formation and maturation affects their 34S/32S isotopic ratio (δ34S), forming specific signatures for distinct sources and processes. Ultimately, thermal maturation homogenizes the δ34S values of different fractions and individual compounds. Reservoir processes such as thermochemical sulfate reduction (TSR) introduce exogenous and isotopically distinct S into hydrocarbons and can significantly change the δ34S of petroleum or kerogen. Specific OSCs react at different rates and thus can be used to evaluate the extent of processes such as TSR. This article reviews factors that affect the 34S/32S isotopic distribution of OSCs along pathways of formation, diagenesis, and thermal alteration.
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Previous Volumes
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Volume 51 (2023)
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Volume 50 (2022)
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Volume 49 (2021)
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Volume 48 (2020)
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Volume 47 (2019)
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Volume 46 (2018)
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Volume 45 (2017)
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Volume 44 (2016)
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Volume 43 (2015)
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Volume 42 (2014)
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Volume 41 (2013)
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Volume 40 (2012)
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Volume 39 (2011)
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Volume 38 (2010)
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Volume 37 (2009)
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Volume 36 (2008)
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Volume 35 (2007)
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Volume 34 (2006)
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Volume 33 (2005)
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Volume 32 (2004)
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Volume 31 (2003)
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Volume 30 (2002)
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Volume 29 (2001)
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Volume 28 (2000)
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Volume 27 (1999)
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Volume 26 (1998)
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Volume 25 (1997)
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Volume 24 (1996)
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Volume 23 (1995)
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Volume 22 (1994)
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Volume 21 (1993)
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Volume 20 (1992)
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Volume 19 (1991)
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Volume 18 (1990)
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Volume 17 (1989)
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Volume 16 (1988)
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Volume 15 (1987)
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Volume 14 (1986)
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Volume 13 (1985)
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Volume 12 (1984)
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Volume 11 (1983)
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Volume 10 (1982)
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Volume 9 (1981)
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Volume 8 (1980)
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Volume 7 (1979)
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Volume 6 (1978)
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Volume 5 (1977)
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Volume 4 (1976)
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Volume 3 (1975)
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Volume 2 (1974)
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Volume 1 (1973)
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Volume 0 (1932)