Adakitic magmas: modern analogues of Archaean granitoids
... 1995; Blais et al., 1997.. However, if plate tectoniclike processes operated, secular compositional changes in magmatism and tectonic regimes indicate that in detail, the processes were different from modern ones. Most of the differences result from greater Archaean heat production, inducing higher ...
... 1995; Blais et al., 1997.. However, if plate tectoniclike processes operated, secular compositional changes in magmatism and tectonic regimes indicate that in detail, the processes were different from modern ones. Most of the differences result from greater Archaean heat production, inducing higher ...
Week 9a
... of the added [H+] reacts with carbonate (CO32–) ion to convert it to bicarbonate (HCO3–). Because most of the added [H+] would be consumed in this way, the change in pH is much less than it would otherwise be. But this process also consumes some carbonate ion; therefore this pH buffering capacity wo ...
... of the added [H+] reacts with carbonate (CO32–) ion to convert it to bicarbonate (HCO3–). Because most of the added [H+] would be consumed in this way, the change in pH is much less than it would otherwise be. But this process also consumes some carbonate ion; therefore this pH buffering capacity wo ...
North Atlantic ecosystem sensitivity to Holocene shifts in Meridional
... surface/atmospheric processes and rates of deep water formation. Holocene climate changes, however, remain poorly documented due to a lack of high-resolution paleoclimate records, and their impacts on marine ecosystems remain unknown. We present a 4500 year absolute-dated sea surface radiocarbon rec ...
... surface/atmospheric processes and rates of deep water formation. Holocene climate changes, however, remain poorly documented due to a lack of high-resolution paleoclimate records, and their impacts on marine ecosystems remain unknown. We present a 4500 year absolute-dated sea surface radiocarbon rec ...
A slab in depth: Three-dimensional geometry and evolution of the
... included; however, we have applied a constant error for each hypocenter by using a sphere size that is equal to ±15 km in X, Y and Z. [ 5 ] Within the Sumatra, Banda and Molucca regions, earthquake hypocenters are recorded to maximum depths of up to 650 to 670 km. Accordingly, both earthquake hypoce ...
... included; however, we have applied a constant error for each hypocenter by using a sphere size that is equal to ±15 km in X, Y and Z. [ 5 ] Within the Sumatra, Banda and Molucca regions, earthquake hypocenters are recorded to maximum depths of up to 650 to 670 km. Accordingly, both earthquake hypoce ...
Atlantic volcanic margins: a comparative study
... Abstract: Volcanic margins in the Atlantic Ocean reveal a series of common crustal units and structural features developed during continental extension and break-up. We suggest that four main crustal zones can be recognized on volcanic margins. This tectono-magmatic zonation implies a history of dev ...
... Abstract: Volcanic margins in the Atlantic Ocean reveal a series of common crustal units and structural features developed during continental extension and break-up. We suggest that four main crustal zones can be recognized on volcanic margins. This tectono-magmatic zonation implies a history of dev ...
A new seafloor electromagnetic station with an Overhauser magnetometer,
... amplitude of the sine curve obtained at the first sea experiment was as large as 25 nT. However, the amplitude rapidly decreased to 9 or 7 nT in the second experiment conducted 6 and 7 months after the first experiment, respectively, while the sinusoidal change was not recognizable any more in the t ...
... amplitude of the sine curve obtained at the first sea experiment was as large as 25 nT. However, the amplitude rapidly decreased to 9 or 7 nT in the second experiment conducted 6 and 7 months after the first experiment, respectively, while the sinusoidal change was not recognizable any more in the t ...
A geological model for the structure of ridge segments in slow
... thatIC cruststartswell abovethe [Bonatti,1976]. In anyof thesecases, pasttheactiveoffset,it becomes better coupled toOCcruston age-depth curveandinitiallysubsides at faster-than-normal sideof thediscontinuity. Thusexcess relative rates. However,otherdatafrom the NorthAtlantic [Collette, theopposite ...
... thatIC cruststartswell abovethe [Bonatti,1976]. In anyof thesecases, pasttheactiveoffset,it becomes better coupled toOCcruston age-depth curveandinitiallysubsides at faster-than-normal sideof thediscontinuity. Thusexcess relative rates. However,otherdatafrom the NorthAtlantic [Collette, theopposite ...
Lecture 12: Surface Processes I
... • However, geochemistry only samples the surface, so inferences Depth about depths within the Earth are indirect, and must be supplemented by geological or geophysical constraints. Interior • In some cases, mantle samples are directly available as xenoliths or peridotite massifs, but mostly the mant ...
... • However, geochemistry only samples the surface, so inferences Depth about depths within the Earth are indirect, and must be supplemented by geological or geophysical constraints. Interior • In some cases, mantle samples are directly available as xenoliths or peridotite massifs, but mostly the mant ...
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... that characterize the Caribbean and the easternmost Scotia Sea may be produced by viscous coupling to the predicted Pacific outflow through the gaps, and the Caribbean floor slopes in the predicted direction. If mantle outflow does pass through the gaps in the Pacific perimeter, it must pass beneath ...
... that characterize the Caribbean and the easternmost Scotia Sea may be produced by viscous coupling to the predicted Pacific outflow through the gaps, and the Caribbean floor slopes in the predicted direction. If mantle outflow does pass through the gaps in the Pacific perimeter, it must pass beneath ...
Oceanic nickel depletion and a methanogen famine before the Great
... in dissolved form, as opposed to particulate material (that is, volcanic ash or clastic sediment). Supporting this are low concentrations of lithophile elements in BIF samples selected for this study (see Methods). Furthermore, the Cr/Ni ratios in Archaean BIF are lower than in Archaean basalts, kom ...
... in dissolved form, as opposed to particulate material (that is, volcanic ash or clastic sediment). Supporting this are low concentrations of lithophile elements in BIF samples selected for this study (see Methods). Furthermore, the Cr/Ni ratios in Archaean BIF are lower than in Archaean basalts, kom ...
What are Phytoplankton?
... microscopic, animal-like zooplankton to multi-ton whales. Small fish and invertebrates also graze on the plant-like organisms, and then those smaller animals are eaten by bigger ones. Phytoplankton can also be the harbingers of death or disease. Certain species of phytoplankton produce powerful biot ...
... microscopic, animal-like zooplankton to multi-ton whales. Small fish and invertebrates also graze on the plant-like organisms, and then those smaller animals are eaten by bigger ones. Phytoplankton can also be the harbingers of death or disease. Certain species of phytoplankton produce powerful biot ...
Quantity and bioavailability of sediment organic matter as signatures
... sediment organic carbon is not an easy task, and generally implies several operational assumptions. The biopolymeric fraction of sediment organic carbon, measured as the sum of protein, carbohydrate and lipid carbon (BPC), has often been reported as the fraction of TOC potentially available to benth ...
... sediment organic carbon is not an easy task, and generally implies several operational assumptions. The biopolymeric fraction of sediment organic carbon, measured as the sum of protein, carbohydrate and lipid carbon (BPC), has often been reported as the fraction of TOC potentially available to benth ...
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... 21) The top of the asthenosphere is closest to Earth's surface ________. A) along a mid-ocean ridge B) above a deep mantle hot spot C) along a transform fault D) along a subduction zone Answer: A Diff: 2 22) New oceanic crust and lithosphere are formed at ________. A) divergent boundaries by submari ...
... 21) The top of the asthenosphere is closest to Earth's surface ________. A) along a mid-ocean ridge B) above a deep mantle hot spot C) along a transform fault D) along a subduction zone Answer: A Diff: 2 22) New oceanic crust and lithosphere are formed at ________. A) divergent boundaries by submari ...
compositional and thermal differences between lithospheric and
... Institute of the Earth’s Crust, Siberian Branch of RAS, Irkutsk, Russia Abstract: The lower part of lithosphere in collisional orogens may delaminate due to density inversion between the asthenosphere and the cold thickened lithospheric mantle. Generally, standard delamination models have neglected ...
... Institute of the Earth’s Crust, Siberian Branch of RAS, Irkutsk, Russia Abstract: The lower part of lithosphere in collisional orogens may delaminate due to density inversion between the asthenosphere and the cold thickened lithospheric mantle. Generally, standard delamination models have neglected ...
Possible density segregation of subducted oceanic
... subduction zones, the slip speed ranges from 20– 80 mm/yr as long as the serpentinite layer is thicker than ∼ 1 km. These differential velocities are comparable to overall subduction velocities, so relative sliding across the serpentinite layer is significant. Using a higher viscosity of N 10 20 Pas ...
... subduction zones, the slip speed ranges from 20– 80 mm/yr as long as the serpentinite layer is thicker than ∼ 1 km. These differential velocities are comparable to overall subduction velocities, so relative sliding across the serpentinite layer is significant. Using a higher viscosity of N 10 20 Pas ...
Ancient recycled mantle lithosphere in the Hawaiian plume: Osmium
... composition of the plume has always been inferred from the compositions of the erupted lavas. It has been suggested that recycled (i.e. previously subducted) basaltic oceanic crust (with or without sediments) is part of this plume and responsible for the enriched isotopic compositions of the Hawaiia ...
... composition of the plume has always been inferred from the compositions of the erupted lavas. It has been suggested that recycled (i.e. previously subducted) basaltic oceanic crust (with or without sediments) is part of this plume and responsible for the enriched isotopic compositions of the Hawaiia ...
Thermal thickness of the Earth`s lithosphere: a numerical model
... (1) the depth to the oceanic bottom is 3 km; (2) the total crust thickness is 6.5 km; (3) the mean crust den sity is 2850 kg/m3; (4) the thickness of the mantle lithosphere is 0.85 km; (5) the density of the upper mantle is 3300 kg/m3; and (6) the freeair gravity anomaly is 9.705 × 10–5 m/c2. The ...
... (1) the depth to the oceanic bottom is 3 km; (2) the total crust thickness is 6.5 km; (3) the mean crust den sity is 2850 kg/m3; (4) the thickness of the mantle lithosphere is 0.85 km; (5) the density of the upper mantle is 3300 kg/m3; and (6) the freeair gravity anomaly is 9.705 × 10–5 m/c2. The ...
Oceanic microplate formation records the onset of India
... 1999; Replumaz et al., 2004; Hafkenscheid et al., 2006). Additionally, global mantle convection modeling combined with seismic tomography analysis has enabled the testing of existing end-member kinematic models (Zahirovic et al., 2012). There is growing support for a complex multiple collision model ...
... 1999; Replumaz et al., 2004; Hafkenscheid et al., 2006). Additionally, global mantle convection modeling combined with seismic tomography analysis has enabled the testing of existing end-member kinematic models (Zahirovic et al., 2012). There is growing support for a complex multiple collision model ...
Jackson and Gunnarss..
... sediments were deposited, or the lack of data to identify structures or the features being masked by later extension. Magnetic data on the Alpha Ridge display an interesting and perhaps significant feature. Calculations of depths to magnetic basement (Kovacs and Vogt, 1982) show a basement depressio ...
... sediments were deposited, or the lack of data to identify structures or the features being masked by later extension. Magnetic data on the Alpha Ridge display an interesting and perhaps significant feature. Calculations of depths to magnetic basement (Kovacs and Vogt, 1982) show a basement depressio ...
CatWardellThesis - University of Washington
... The elevation of the ridges decreases with distance from the axial valley, with the exception of some ridges at the north of the Pacific-Rivera spreading center and those to the west of it. The presence of the overlapping spreading center to the north of the survey area may have resulted in the com ...
... The elevation of the ridges decreases with distance from the axial valley, with the exception of some ridges at the north of the Pacific-Rivera spreading center and those to the west of it. The presence of the overlapping spreading center to the north of the survey area may have resulted in the com ...
PDF format - gemoc - Macquarie University
... data from individual sulfides removes much of the ambiguity inherent in whole rock studies due to the usual presence of at least two generations of sulfide within the same rock. It also allows for a relatively rapid acquisition of a large data-set compared to conventional methods, 72 samples in the ...
... data from individual sulfides removes much of the ambiguity inherent in whole rock studies due to the usual presence of at least two generations of sulfide within the same rock. It also allows for a relatively rapid acquisition of a large data-set compared to conventional methods, 72 samples in the ...
Earth: An Introduction to Physical Geology, 10e (Tarbuck/Lutgens
... B) cool, rigid layer of crust and upper mantle that forms the tectonic plates C) deforms mainly by brittle fracturing and faulting D) partial melting of rising granitic plumes produces huge volumes of basaltic magma Answer: A Diff: 1 ...
... B) cool, rigid layer of crust and upper mantle that forms the tectonic plates C) deforms mainly by brittle fracturing and faulting D) partial melting of rising granitic plumes produces huge volumes of basaltic magma Answer: A Diff: 1 ...
Earth-9th-Edition-Tarbuck-Test-Bank
... A) zone in the upper mantle that deforms by plastic flowage B) cool, rigid layer of crust and upper mantle that forms the tectonic plates C) deforms mainly by brittle fracturing and faulting D) partial melting of rising granitic plumes produces huge volumes of basaltic magma Answer: A Diff: 1 ...
... A) zone in the upper mantle that deforms by plastic flowage B) cool, rigid layer of crust and upper mantle that forms the tectonic plates C) deforms mainly by brittle fracturing and faulting D) partial melting of rising granitic plumes produces huge volumes of basaltic magma Answer: A Diff: 1 ...
Lithosphere, Earth`s Interior and Paleo-Environment
... several distinct mantle plumes, instead of a single large one, as the origin of volcanism in and around west Antarctica. These deep plumes may be responsible for feeding large regions of low seismic velocities in the asthenosphere. A high shear wave velocity anomalies is found at a depth of 25 to 20 ...
... several distinct mantle plumes, instead of a single large one, as the origin of volcanism in and around west Antarctica. These deep plumes may be responsible for feeding large regions of low seismic velocities in the asthenosphere. A high shear wave velocity anomalies is found at a depth of 25 to 20 ...
11. GEODYNAMIC EVOLUTION OF THE CÔTE D`IVOIRE
... crusts. During Late Cretaceous times, the transform margin experienced continuous subsidence leading to the progressive upslope migration of the reef. An increasing subsidence rate characterized the early Coniacian, close to the time when the first continent/ocean transform transition occurred. No s ...
... crusts. During Late Cretaceous times, the transform margin experienced continuous subsidence leading to the progressive upslope migration of the reef. An increasing subsidence rate characterized the early Coniacian, close to the time when the first continent/ocean transform transition occurred. No s ...
Abyssal plain
An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between 3000 and 6000 m. Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth’s surface. They are among the flattest, smoothest and least explored regions on Earth. Abyssal plains are key geologic elements of oceanic basins (the other elements being an elevated mid-ocean ridge and flanking abyssal hills). In addition to these elements, active oceanic basins (those that are associated with a moving plate tectonic boundary) also typically include an oceanic trench and a subduction zone.Abyssal plains were not recognized as distinct physiographic features of the sea floor until the late 1940s and, until very recently, none had been studied on a systematic basis. They are poorly preserved in the sedimentary record, because they tend to be consumed by the subduction process. The creation of the abyssal plain is the end result of spreading of the seafloor (plate tectonics) and melting of the lower oceanic crust. Magma rises from above the asthenosphere (a layer of the upper mantle) and as this basaltic material reaches the surface at mid-ocean ridges it forms new oceanic crust. This is constantly pulled sideways by spreading of the seafloor. Abyssal plains result from the blanketing of an originally uneven surface of oceanic crust by fine-grained sediments, mainly clay and silt. Much of this sediment is deposited by turbidity currents that have been channelled from the continental margins along submarine canyons down into deeper water. The remainder of the sediment is composed chiefly of pelagic sediments. Metallic nodules are common in some areas of the plains, with varying concentrations of metals, including manganese, iron, nickel, cobalt, and copper. These nodules may provide a significant resource for future mining ventures.Owing in part to their vast size, abyssal plains are currently believed to be a major reservoir of biodiversity. The abyss also exerts significant influence upon ocean carbon cycling, dissolution of calcium carbonate, and atmospheric CO2 concentrations over timescales of 100–1000 years. The structure and function of abyssal ecosystems are strongly influenced by the rate of flux of food to the seafloor and the composition of the material that settles. Factors such as climate change, fishing practices, and ocean fertilization are expected to have a substantial effect on patterns of primary production in the euphotic zone. This will undoubtedly impact the flux of organic material to the abyss in a similar manner and thus have a profound effect on the structure, function and diversity of abyssal ecosystems.