Plate Tectonics - Horizon Research, Inc.
... E. Since the supercontinent Pangaea split up about 200 million years ago, the shapes of continents have been somewhat modified, mostly by erosion, sea level changes, and mountain-building; this is why the present-day "fit" of the continents is less than perfect. F. Plate motion causes abutting plate ...
... E. Since the supercontinent Pangaea split up about 200 million years ago, the shapes of continents have been somewhat modified, mostly by erosion, sea level changes, and mountain-building; this is why the present-day "fit" of the continents is less than perfect. F. Plate motion causes abutting plate ...
Attenuation Tomography Beneath the Rocky Mountain Front
... time tomography but with smaller variations in P wave velocity, -4% (also summarized by Lerner-Lam et al. [1998]). Li et al. [2002] measured surface wave dispersion and inverted for crustal and upper mantle shear wave velocity. The greatest difference between the models of Lee and Grand and Li et al ...
... time tomography but with smaller variations in P wave velocity, -4% (also summarized by Lerner-Lam et al. [1998]). Li et al. [2002] measured surface wave dispersion and inverted for crustal and upper mantle shear wave velocity. The greatest difference between the models of Lee and Grand and Li et al ...
Are the Earth and the Moon compositionally alike? Inferences on
... observational study of the phase relationships and trace element compositions of lunar mare basalts and picritic glasses. In particular, by melting a typical model mantle composition using the pMELTS algorithm, we found that a range of batch melts generated from these models have features in common ...
... observational study of the phase relationships and trace element compositions of lunar mare basalts and picritic glasses. In particular, by melting a typical model mantle composition using the pMELTS algorithm, we found that a range of batch melts generated from these models have features in common ...
subsurface data at core sites
... Figure SM1: Map of Cocos Ridge Survey (COCOS6N, Liao and Lyle, in press) showing seismic lines (blue) and other tracklines (red). Cores are taken at yellow dots. Figure SM2: Map of Carnegie Ridge Survey, showing seismic lines (blue) and other tracklines (red). Cores are taken at yellow dots. Figure ...
... Figure SM1: Map of Cocos Ridge Survey (COCOS6N, Liao and Lyle, in press) showing seismic lines (blue) and other tracklines (red). Cores are taken at yellow dots. Figure SM2: Map of Carnegie Ridge Survey, showing seismic lines (blue) and other tracklines (red). Cores are taken at yellow dots. Figure ...
Convective destabilization of a thickened continental lithosphere
... Removal or delamination of the lithospheric mantle in a late stage of mountain building is a process often invoked to explain syn orogenic extension, high temperature metamorphism, magmatism and uplift. One mechanism that could explain the lithospheric root detachment is the development of convectiv ...
... Removal or delamination of the lithospheric mantle in a late stage of mountain building is a process often invoked to explain syn orogenic extension, high temperature metamorphism, magmatism and uplift. One mechanism that could explain the lithospheric root detachment is the development of convectiv ...
The Origin, Evolution and Present State of Subcontinental Lithosphere
... Scientific questions to be considered and discussed: (1) What may have caused the lithosphere thinning? (2) Is it plausible that the buoyant SCLM sinks into the dense asthenosphere by a process called “delamination”? (3) If so, why doesn’t such “delamination” seem to occur beneath ancient cratons su ...
... Scientific questions to be considered and discussed: (1) What may have caused the lithosphere thinning? (2) Is it plausible that the buoyant SCLM sinks into the dense asthenosphere by a process called “delamination”? (3) If so, why doesn’t such “delamination” seem to occur beneath ancient cratons su ...
One-dimensional physical reference models for the upper mantle
... [6] Our aim in this paper is to define a physical onedimensional model for the upper mantle that can be used for seismic inversions and aid their interpretation. Our analysis is an illustration of how this problem can be approached and gives a first set of physical reference models. These models can ...
... [6] Our aim in this paper is to define a physical onedimensional model for the upper mantle that can be used for seismic inversions and aid their interpretation. Our analysis is an illustration of how this problem can be approached and gives a first set of physical reference models. These models can ...
Document
... Prior to the 1960’s most geologists considered the ocean floors to be generally featureless plains, the oceanic crust to be very old and topographically featureless. It was also assumed to be fixed in place. By 1970, all this had changed. ...
... Prior to the 1960’s most geologists considered the ocean floors to be generally featureless plains, the oceanic crust to be very old and topographically featureless. It was also assumed to be fixed in place. By 1970, all this had changed. ...
Anisotropy in the Earth`s crust and uppermost mantle in
... calculated lateral group-velocity distributions for both Rayleigh and Love waves in the period range of 10 – 20 s in Black Sea and adjoining regions. They inverted local dispersion curves and thus obtained the crust structure along a profile (latitude 43j, longitude between 24j and 42j) down to the ...
... calculated lateral group-velocity distributions for both Rayleigh and Love waves in the period range of 10 – 20 s in Black Sea and adjoining regions. They inverted local dispersion curves and thus obtained the crust structure along a profile (latitude 43j, longitude between 24j and 42j) down to the ...
Chapter 2 Volcanoes - San Diego State University Department of
... arc lies about 100 ‐ 125 km from the trench. However, if the subducting plate dips steeper, as for example 60o, then the volcanic arc will lie about 58 ‐ 72 km from the trench. In contrast, if the subducting plate dips say 30o, then the volcanic arc will lie about 173 – 217 km from the trench. ...
... arc lies about 100 ‐ 125 km from the trench. However, if the subducting plate dips steeper, as for example 60o, then the volcanic arc will lie about 58 ‐ 72 km from the trench. In contrast, if the subducting plate dips say 30o, then the volcanic arc will lie about 173 – 217 km from the trench. ...
Relation Between Volcanism, Tectonism, and Hydrothermal Activity
... Early studies focused on hydrothermal systems on the fast-spreading East Pacific Rise, where shallow magma lenses beneath the ridge crest provide heat to drive convection of seawater through the oceanic crust. Ten years later, studies of the slow-spreading Mid-Atlantic Ridge revealed much larger min ...
... Early studies focused on hydrothermal systems on the fast-spreading East Pacific Rise, where shallow magma lenses beneath the ridge crest provide heat to drive convection of seawater through the oceanic crust. Ten years later, studies of the slow-spreading Mid-Atlantic Ridge revealed much larger min ...
Thermal structure and intermediate-depth seismicity in the Tohoku
... Fig. 3. General model geometry (top) and partial mesh (bottom) used in the finite element modeling. The velocity is prescribed in the slab and set to zero in the crust of the overriding plate (with the Moho indicated by M). The wedge is modeled as a fluid with a rheology appropriate for dry olivine ...
... Fig. 3. General model geometry (top) and partial mesh (bottom) used in the finite element modeling. The velocity is prescribed in the slab and set to zero in the crust of the overriding plate (with the Moho indicated by M). The wedge is modeled as a fluid with a rheology appropriate for dry olivine ...
Mantle structure and tectonic history of SE Asia
... subducted before the slab now imaged in the upper mantle. Interpreting tectonic history from seismic tomography is not straightforward, even for the upper mantle, and even if it is entirely the result of subduction. Anomalies at the same depth may correspond to subduction of lithosphere of different ...
... subducted before the slab now imaged in the upper mantle. Interpreting tectonic history from seismic tomography is not straightforward, even for the upper mantle, and even if it is entirely the result of subduction. Anomalies at the same depth may correspond to subduction of lithosphere of different ...
Thermal and metamorphic environment of subduction zone episodic
... truncated at the tip of the mantle wedge to satisfy surface heat flow measurements. Note that the choice of mantle rheology does not significantly affect the temperatures calculated for the shallow fore arc, unless flow in the mantle wedge corner were to extend updip to depths <50 km, which would be ...
... truncated at the tip of the mantle wedge to satisfy surface heat flow measurements. Note that the choice of mantle rheology does not significantly affect the temperatures calculated for the shallow fore arc, unless flow in the mantle wedge corner were to extend updip to depths <50 km, which would be ...
Plate tectonics from space - Laboratoire de Géologie de l`Ecole
... The first artificial satellites were launched at approximately the same time (Sputnik, 1957). Without mentioning the bunch of applications unrelated to the progress of science, positioning was one useful output. However, few geoscientists in these early years would have bet a penny on the "real-time ...
... The first artificial satellites were launched at approximately the same time (Sputnik, 1957). Without mentioning the bunch of applications unrelated to the progress of science, positioning was one useful output. However, few geoscientists in these early years would have bet a penny on the "real-time ...
Geology - Geostud
... values were determined on the basis of Poisson’s ratios between 0.25 and 0.3 for various lithologies (Christensen, 1996). To obtain realistic synthetic waveforms, each computed waveform is convolved with the observed vertical component. The real ambient noise measured 100–5 s before Pwave arrival wa ...
... values were determined on the basis of Poisson’s ratios between 0.25 and 0.3 for various lithologies (Christensen, 1996). To obtain realistic synthetic waveforms, each computed waveform is convolved with the observed vertical component. The real ambient noise measured 100–5 s before Pwave arrival wa ...
Long-term survival of the axial valley morphology at abandoned slow-spreading centers
... For the cyclic faulting model associated with the configuration of Figure 2, we have calculated the corresponding stress distribution in the crust and mantle. Figure 3a shows the axial valley topography and the associated horizontal deviatoric stress, sx 2 P, where P 5 (sx 1 sy 1 sz)/3, at the end o ...
... For the cyclic faulting model associated with the configuration of Figure 2, we have calculated the corresponding stress distribution in the crust and mantle. Figure 3a shows the axial valley topography and the associated horizontal deviatoric stress, sx 2 P, where P 5 (sx 1 sy 1 sz)/3, at the end o ...
ž / Evidence from mantle xenoliths for relatively thin -100
... Ca, and by kelyphitic rims around garnet. The majority of moderate- and high-temperature Ž) 9708C. xenoliths are petrochemically similar to the asthenospheric source of mid-oceanic ridge basalts: fertile Ž) 20% modal clinopyroxene and garnet., Fe-rich garnet lherzolite with major element composition ...
... Ca, and by kelyphitic rims around garnet. The majority of moderate- and high-temperature Ž) 9708C. xenoliths are petrochemically similar to the asthenospheric source of mid-oceanic ridge basalts: fertile Ž) 20% modal clinopyroxene and garnet., Fe-rich garnet lherzolite with major element composition ...
Chemical Geodynamics - Woods Hole Oceanographic Institution
... Inferring domain sizes of mantle heterogeneities based on observations of erupted basalts is a very complex issue, though this avenue is the principal source of the proof that mantle geochemical heterogeneities do in fact exist. The basic problem is one of trying to elucidate three-dimensional domai ...
... Inferring domain sizes of mantle heterogeneities based on observations of erupted basalts is a very complex issue, though this avenue is the principal source of the proof that mantle geochemical heterogeneities do in fact exist. The basic problem is one of trying to elucidate three-dimensional domai ...
Simulating the thermochemical magmatic and tectonic evolution of
... Table 2]. The heat production rate H of the samples is intermediate between E-MORB and OIB on Earth: relative to a plausible bulk silicate Earth heat production rate HBSE = 5.2 " 10#12 W/kg, four samples range between 14 and 33 HBSE, with one outlier at 102 HBSE. [5] An episodic resurfacing scenario ...
... Table 2]. The heat production rate H of the samples is intermediate between E-MORB and OIB on Earth: relative to a plausible bulk silicate Earth heat production rate HBSE = 5.2 " 10#12 W/kg, four samples range between 14 and 33 HBSE, with one outlier at 102 HBSE. [5] An episodic resurfacing scenario ...
Major and trace analysis of basaltic glasses by laser-ablation ICP-MS
... [1] We use the Multipole–Boundary Element Method (MP-BEM) to simulate regional and global geodynamics in a spherical 3-D setting. We first simulate an isolated subducting rectangular plate with length (Llitho) and width (Wlitho) varying between 0.5 and 2 times the radius of the Earth (REarth) and wi ...
... [1] We use the Multipole–Boundary Element Method (MP-BEM) to simulate regional and global geodynamics in a spherical 3-D setting. We first simulate an isolated subducting rectangular plate with length (Llitho) and width (Wlitho) varying between 0.5 and 2 times the radius of the Earth (REarth) and wi ...
Mantle plume
A mantle plume is a mechanism proposed in 1971 to explain volcanic regions of the earth that were not thought to be explicable by the then-new theory of plate tectonics. Some such volcanic regions lie far from tectonic plate boundaries, for example, Hawaii. Others represent unusually large-volume volcanism, whether on plate boundaries, e.g. Iceland, or basalt floods such as the Deccan or Siberian traps.A mantle plume is posited to exist where hot rock nucleates at the core-mantle boundary and rises through the Earth's mantle becoming a diapir in the Earth's crust. The currently active volcanic centers are known as ""hot spots"". In particular, the concept that mantle plumes are fixed relative to one another, and anchored at the core-mantle boundary, was thought to provide a natural explanation for the time-progressive chains of older volcanoes seen extending out from some such hot spots, such as the Hawaiian–Emperor seamount chain.The hypothesis of mantle plumes from depth is not universally accepted as explaining all such volcanism. It has required progressive hypothesis-elaboration leading to variant propositions such as mini-plumes and pulsing plumes. Another hypothesis for unusual volcanic regions is the ""Plate model"". This proposes shallower, passive leakage of magma from the mantle onto the Earth's surface where extension of the lithosphere permits it, attributing most volcanism to plate tectonic processes, with volcanoes far from plate boundaries resulting from intraplate extension.