Geochemical evidence for interaction between oceanic crust and
... Cenozoic basalts from China, it has been commonly hypothesized that they were derived from partial melting of the convective asthenosphere or lithosphere–asthenosphere interaction (e.g., Zou et al., 2000; Xu et al., 2005; Tang et al., 2006). Such a hypothesis presumes that the depleted mantle source ...
... Cenozoic basalts from China, it has been commonly hypothesized that they were derived from partial melting of the convective asthenosphere or lithosphere–asthenosphere interaction (e.g., Zou et al., 2000; Xu et al., 2005; Tang et al., 2006). Such a hypothesis presumes that the depleted mantle source ...
Gulf of Mexico tectonic history: Hotspot tracks, crustal
... and Uchupi, 1982; Ebeniro et al., 1986, 1988; Nakamura et al., 1988; Kim et al., 2000). In the central parts of the basin, refraction depths and velocities represent oceanic basement and upper mantle. Crustal thicknesses range from about 5 to 8 km (3.1 to 5.0 mi) in these deeper parts of the basin, ...
... and Uchupi, 1982; Ebeniro et al., 1986, 1988; Nakamura et al., 1988; Kim et al., 2000). In the central parts of the basin, refraction depths and velocities represent oceanic basement and upper mantle. Crustal thicknesses range from about 5 to 8 km (3.1 to 5.0 mi) in these deeper parts of the basin, ...
Ducea, M. N., Kidder, S. B., Chesley, J. T., and
... Subduction of oceanic plates is a major plate tectonic process that has operated for much of the Earth’s history. During subduction, dense oceanic lithosphere is returned to the mantle primarily owing to its negative buoyancy. In the process, sedimentary sequences that were either deposited on the o ...
... Subduction of oceanic plates is a major plate tectonic process that has operated for much of the Earth’s history. During subduction, dense oceanic lithosphere is returned to the mantle primarily owing to its negative buoyancy. In the process, sedimentary sequences that were either deposited on the o ...
Tectonophysics_2009_Crustal and upper mantle velocity
... medium around the east Himalayan foreland. High-velocity anomalies in the lower crust might be explained as intrusions of mantle material or remaining patches of ancient oceanic crust. Keywords: wide-angle seismic reflections, P-wave velocity model, geodynamic implications, Yunnan, Southwest China. ...
... medium around the east Himalayan foreland. High-velocity anomalies in the lower crust might be explained as intrusions of mantle material or remaining patches of ancient oceanic crust. Keywords: wide-angle seismic reflections, P-wave velocity model, geodynamic implications, Yunnan, Southwest China. ...
Crustal geophysical research helps constrain the nature of mantle
... in this Table, the main difference is the thicker crust with respect to that of normal oceanic crust. Regardless of crustal thickness variations, the ratio of Layer 2 thickness versus total crustal thickness is quite uniform (around 25 %), indicating that Layer 3 accommodates most of the crustal ove ...
... in this Table, the main difference is the thicker crust with respect to that of normal oceanic crust. Regardless of crustal thickness variations, the ratio of Layer 2 thickness versus total crustal thickness is quite uniform (around 25 %), indicating that Layer 3 accommodates most of the crustal ove ...
Consulta: creatorFacets:"Le Pichon, Xavier" Registros recuperados
... fig. 1b). The role of these currents in the formation of large sediment ripples has been demonstrated in some recent studies [(2), (3)]. As in the southern Atlantic Ocean, the observations suggested that their influence had been of importance since the Eocene era (6). From a sedimentological point o ...
... fig. 1b). The role of these currents in the formation of large sediment ripples has been demonstrated in some recent studies [(2), (3)]. As in the southern Atlantic Ocean, the observations suggested that their influence had been of importance since the Eocene era (6). From a sedimentological point o ...
readingetal_geology_.. - Research School of Earth Sciences
... function work of Clitheroe et al. (2000) and the active source studies of Drummond (1988) and/or Collins et al. (2003). The Pilbara craton shows a very sharp, shallow Moho at 32 km with a velocity gradient in the lower crust. The Moho becomes deeper toward the south of the craton beneath the Hamersl ...
... function work of Clitheroe et al. (2000) and the active source studies of Drummond (1988) and/or Collins et al. (2003). The Pilbara craton shows a very sharp, shallow Moho at 32 km with a velocity gradient in the lower crust. The Moho becomes deeper toward the south of the craton beneath the Hamersl ...
A model for the layered upper mantle
... ing requires a major revision of our views on mantle convection. Gasparik (1993) proposed that a significant transport by convection may only occur in the presence of an interstitial melt. This study concluded that the expected mantle temperatures are higher than the temperatures of the volatile sol ...
... ing requires a major revision of our views on mantle convection. Gasparik (1993) proposed that a significant transport by convection may only occur in the presence of an interstitial melt. This study concluded that the expected mantle temperatures are higher than the temperatures of the volatile sol ...
The transition from diffuse to focused extension: Modeled evolution
... Two distinct stages of extension are recognized in the West Antarctic Rift system (WARS). During the first stage, beginning in the Late Cretaceous, extension was broadly distributed throughout much of West Antarctica. A second stage of extension in the late Paleogene was focused primarily in the Vic ...
... Two distinct stages of extension are recognized in the West Antarctic Rift system (WARS). During the first stage, beginning in the Late Cretaceous, extension was broadly distributed throughout much of West Antarctica. A second stage of extension in the late Paleogene was focused primarily in the Vic ...
The Variscides
... This zone may continue in the South Portuguese zone which exposes a Late Devonian to Early Carboniferous volcanosedimentary basin and massive sulphide deposits. - The Giesen and Lizard Ophiolites represent Middle-Late Devonian ocean floor obducted onto the Rhenohercynian Zone. They mark the suture b ...
... This zone may continue in the South Portuguese zone which exposes a Late Devonian to Early Carboniferous volcanosedimentary basin and massive sulphide deposits. - The Giesen and Lizard Ophiolites represent Middle-Late Devonian ocean floor obducted onto the Rhenohercynian Zone. They mark the suture b ...
Is the rate of supercontinent assembly changing with time?
... We still have many questions regarding the supercontinent cycle, such as when it began, has continental crust grown in volume with time, and has the period of the cycle been constant or has it changed with time. The timescale of assembly and dispersal of supercontinents is still not well constrained ...
... We still have many questions regarding the supercontinent cycle, such as when it began, has continental crust grown in volume with time, and has the period of the cycle been constant or has it changed with time. The timescale of assembly and dispersal of supercontinents is still not well constrained ...
ppt
... areas where the continental crust has been thickened by orogeny, either continental arc subduction or collision of sialic masses. Many granites, however, may post-date the thickening event by tens of millions of years. 2) Because the crust is solid in its normal state, some thermal disturbance is re ...
... areas where the continental crust has been thickened by orogeny, either continental arc subduction or collision of sialic masses. Many granites, however, may post-date the thickening event by tens of millions of years. 2) Because the crust is solid in its normal state, some thermal disturbance is re ...
The Mw 6.5 offshore Northern California earthquake of 10 January
... Mendocino Fault Zone on the south, and Cascadia Subduction zone on the east (Figure 1a). This region has the highest rate of large earthquakes in the contiguous United States, having hosted more than 16 M > 6 earthquakes in the last 40 years. The exceptionally high rate is likely due to the strong i ...
... Mendocino Fault Zone on the south, and Cascadia Subduction zone on the east (Figure 1a). This region has the highest rate of large earthquakes in the contiguous United States, having hosted more than 16 M > 6 earthquakes in the last 40 years. The exceptionally high rate is likely due to the strong i ...
Project Earth Science: Geology - National Science Teachers
... of volcanoes and earthquakes suggested that continents were just parts of enormous “plates” that make up outer Earth. They proposed that as these plates moved and their edges interacted, earthquakes were generated, and magma rose to the surface between plates, producing volcanoes. Many geoscientist ...
... of volcanoes and earthquakes suggested that continents were just parts of enormous “plates” that make up outer Earth. They proposed that as these plates moved and their edges interacted, earthquakes were generated, and magma rose to the surface between plates, producing volcanoes. Many geoscientist ...
The Great Rift Valley
... A rift valley forms where the Earth’s crust, or outermost layer, is spreading or splitting apart. This kind of valley is often narrow, with steep sides and a flat floor. Rift valleys are also called grabens, which means “ditch” in German. While there is no official distinction between a graben and a ...
... A rift valley forms where the Earth’s crust, or outermost layer, is spreading or splitting apart. This kind of valley is often narrow, with steep sides and a flat floor. Rift valleys are also called grabens, which means “ditch” in German. While there is no official distinction between a graben and a ...
Scientific Ocean Drilling: Accomplishments and Challenges
... holes provide additional opportunities to monitor conditions such as temperature, pressure, and fluid flow in the subseafloor through placement of sensors in the borehole. The process of collecting data from boreholes is complicated by the fact that drilling can disturb natural conditions and result ...
... holes provide additional opportunities to monitor conditions such as temperature, pressure, and fluid flow in the subseafloor through placement of sensors in the borehole. The process of collecting data from boreholes is complicated by the fact that drilling can disturb natural conditions and result ...
Review of the Lithium Isotope System as a Geochemical Tracer
... The Li isotopic composition of river water is not highly sensitive to that of the bedrock, in contrast to radiogenic isotopic ratios used to monitor chemical weathering (Huh et al., 1998). There is thus promise in using the evolution of the Li isotope ratio of seawater to assess past changes in the ...
... The Li isotopic composition of river water is not highly sensitive to that of the bedrock, in contrast to radiogenic isotopic ratios used to monitor chemical weathering (Huh et al., 1998). There is thus promise in using the evolution of the Li isotope ratio of seawater to assess past changes in the ...
The Cretaceous and Cenozoic tectonic evolution of
... to compare our plate model evolution to seismic tomography. In particular, slabs observed at depths shallower than ∼ 1000 km beneath northern Borneo and the South China Sea are likely to be remnants of the proto-South China Sea basin. ...
... to compare our plate model evolution to seismic tomography. In particular, slabs observed at depths shallower than ∼ 1000 km beneath northern Borneo and the South China Sea are likely to be remnants of the proto-South China Sea basin. ...
Geology First active hydrothermal vents on an ultraslow-spreading center: Southwest Indian Ridge
... widespread along all ultraslow-spreading ridges (German et al., 1998; Baker et al., 2004), at least in the magmatically robust regions. The 49°39′E active field is directly comparable, in lateral extent (at ~1000 m), to two of the largest known active hydrothermal fields from the slow-spreading Mid- ...
... widespread along all ultraslow-spreading ridges (German et al., 1998; Baker et al., 2004), at least in the magmatically robust regions. The 49°39′E active field is directly comparable, in lateral extent (at ~1000 m), to two of the largest known active hydrothermal fields from the slow-spreading Mid- ...
Small-scale upper mantle convection and crustal dynamics in
... convection of the upper mantle in driving deformation of the overlying crust in southern California. It is clear that present-day deformation in southern California is strongly influenced by plate interaction stresses; we show that much of the deformation that cannot be explained by plate interactio ...
... convection of the upper mantle in driving deformation of the overlying crust in southern California. It is clear that present-day deformation in southern California is strongly influenced by plate interaction stresses; we show that much of the deformation that cannot be explained by plate interactio ...
Dynamical effects of subducting ridges: insights from 3
... In the following, we model the subduction of a 80-km-thick lithosphere (∼50-Myr-old oceanic plate). In case the thickness of the oceanic crust is ‘normal’ (∼7 km), the 50-Myr-old oceanic lithosphere is negatively buoyant with respect to the asthenosphere, and its average buoyancy (ρ L ) Nature = −3 ...
... In the following, we model the subduction of a 80-km-thick lithosphere (∼50-Myr-old oceanic plate). In case the thickness of the oceanic crust is ‘normal’ (∼7 km), the 50-Myr-old oceanic lithosphere is negatively buoyant with respect to the asthenosphere, and its average buoyancy (ρ L ) Nature = −3 ...
Implications of Subduction Rehydration for Earth`s Deep
... composition that they call GLOSS. GLOSS contains about 7wt% of chemically bound water. If we assume an average sediment thickness of 500m and that the 8km thick crust is made of one kilometer of highly altered basalt (2.7wt% H2O), two kilometers of less hydrated (1wt% H2O) and 5km of almost dry rock ...
... composition that they call GLOSS. GLOSS contains about 7wt% of chemically bound water. If we assume an average sediment thickness of 500m and that the 8km thick crust is made of one kilometer of highly altered basalt (2.7wt% H2O), two kilometers of less hydrated (1wt% H2O) and 5km of almost dry rock ...
Crustal and upper mantle structure of southernmost South America
... search of the model space and enabling us to examine alternative local error minima. The vertical and transverse waveforms were used, extending from the P arrival to the surface waves, and the inversion was performed at either 0.005–0.06 Hz (larger events) or 0.02– 0.06 Hz (smaller events). The inve ...
... search of the model space and enabling us to examine alternative local error minima. The vertical and transverse waveforms were used, extending from the P arrival to the surface waves, and the inversion was performed at either 0.005–0.06 Hz (larger events) or 0.02– 0.06 Hz (smaller events). The inve ...
Plate tectonics
Plate tectonics (from the Late Latin tectonicus, from the Greek: τεκτονικός ""pertaining to building"") is a scientific theory that describes the large-scale motion of Earth's lithosphere. This theoretical model builds on the concept of continental drift which was developed during the first few decades of the 20th century. The geoscientific community accepted the theory after the concepts of seafloor spreading were later developed in the late 1950s and early 1960s.The lithosphere, which is the rigid outermost shell of a planet (on Earth, the crust and upper mantle), is broken up into tectonic plates. On Earth, there are seven or eight major plates (depending on how they are defined) and many minor plates. Where plates meet, their relative motion determines the type of boundary; convergent, divergent, or transform. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along these plate boundaries. The lateral relative movement of the plates typically varies from zero to 100 mm annually.Tectonic plates are composed of oceanic lithosphere and thicker continental lithosphere, each topped by its own kind of crust. Along convergent boundaries, subduction carries plates into the mantle; the material lost is roughly balanced by the formation of new (oceanic) crust along divergent margins by seafloor spreading. In this way, the total surface of the globe remains the same. This prediction of plate tectonics is also referred to as the conveyor belt principle. Earlier theories (that still have some supporters) propose gradual shrinking (contraction) or gradual expansion of the globe.Tectonic plates are able to move because the Earth's lithosphere has greater strength than the underlying asthenosphere. Lateral density variations in the mantle result in convection. Plate movement is thought to be driven by a combination of the motion of the seafloor away from the spreading ridge (due to variations in topography and density of the crust, which result in differences in gravitational forces) and drag, with downward suction, at the subduction zones. Another explanation lies in the different forces generated by the rotation of the globe and the tidal forces of the Sun and Moon. The relative importance of each of these factors and their relationship to each other is unclear, and still the subject of much debate.