Older crust underlies Iceland
... The requirement for older, submerged crust beneath the younger lavas is in full agreement with the crustal accretion model of Palmason (1973, 1980). This model shows how the volcanic pile subsides beneath the weight of new erupted lavas as crustal accretion proceeds. Lavas may flow for long distance ...
... The requirement for older, submerged crust beneath the younger lavas is in full agreement with the crustal accretion model of Palmason (1973, 1980). This model shows how the volcanic pile subsides beneath the weight of new erupted lavas as crustal accretion proceeds. Lavas may flow for long distance ...
Earthquake size distribution in subduction zones
... Earthquake size distribution in subduction zones linked to slab buoyancy Tomoaki Nishikawa* and Satoshi Ide The occurrence of subduction zone earthquakes is primarily controlled by the state of stress on the interface between the subducting and overriding plates. This stress state is influenced by t ...
... Earthquake size distribution in subduction zones linked to slab buoyancy Tomoaki Nishikawa* and Satoshi Ide The occurrence of subduction zone earthquakes is primarily controlled by the state of stress on the interface between the subducting and overriding plates. This stress state is influenced by t ...
The asthenosphere low-velocity layer Over 100 years ago, Airy and
... part of the mantle is probably far from being casual and is connected with a velocity decrease of seismic waves " (Gorslikov, 1958, p. 28). " The most probable reason for this phenomenon is a transition from a crystalline state into an amorplious condition " (Gorshkov, 1958, p. 109). These results g ...
... part of the mantle is probably far from being casual and is connected with a velocity decrease of seismic waves " (Gorslikov, 1958, p. 28). " The most probable reason for this phenomenon is a transition from a crystalline state into an amorplious condition " (Gorshkov, 1958, p. 109). These results g ...
Plate Tectonics: This works as a result of hot mantle asthenosphere
... because the basaltic component of the slab (now eclogite) is ca. 0.2 0.1 g/cc more dense than the enclosing host pyrolite to depths of 650 km, and exerts a strong ’slab-pull’ force at subduction zones. The harzburgite part of the plate may also be slightly more dense initially because it is cold, bu ...
... because the basaltic component of the slab (now eclogite) is ca. 0.2 0.1 g/cc more dense than the enclosing host pyrolite to depths of 650 km, and exerts a strong ’slab-pull’ force at subduction zones. The harzburgite part of the plate may also be slightly more dense initially because it is cold, bu ...
The Oceanic Phosphorus Cycle - Center for Microbial Oceanography
... Mg, Al, and Fe, which are known to be weakly soluble59,62 while the organic P fraction has not been well characterized. Anthropogenic P sources may be associated with more soluble components.63 The atmospheric P flux over the ocean is quite variable in space and time, ranging from 0.9 µmol m-2 day-1 ...
... Mg, Al, and Fe, which are known to be weakly soluble59,62 while the organic P fraction has not been well characterized. Anthropogenic P sources may be associated with more soluble components.63 The atmospheric P flux over the ocean is quite variable in space and time, ranging from 0.9 µmol m-2 day-1 ...
New bathymetry and magnetic lineations identifications in the
... The seafloor spreading of the South China Sea (SCS) was previously believed to take place between ca. 32 and 15 Ma (magnetic anomaly C11 to C5c). New magnetic data acquired in the northernmost SCS however suggests the existence of E–W trending magnetic polarity reversal patterns. Magnetic modeling de ...
... The seafloor spreading of the South China Sea (SCS) was previously believed to take place between ca. 32 and 15 Ma (magnetic anomaly C11 to C5c). New magnetic data acquired in the northernmost SCS however suggests the existence of E–W trending magnetic polarity reversal patterns. Magnetic modeling de ...
The Oceanic Phosphorus Cycle
... Mg, Al, and Fe, which are known to be weakly soluble59,62 while the organic P fraction has not been well characterized. Anthropogenic P sources may be associated with more soluble components.63 The atmospheric P flux over the ocean is quite variable in space and time, ranging from 0.9 µmol m-2 day-1 ...
... Mg, Al, and Fe, which are known to be weakly soluble59,62 while the organic P fraction has not been well characterized. Anthropogenic P sources may be associated with more soluble components.63 The atmospheric P flux over the ocean is quite variable in space and time, ranging from 0.9 µmol m-2 day-1 ...
cntists think and work and how a hypothesis a n bt proposed
... ROdF matches show when continents were together; once the continents split, the new rocks formed are dissimilar. Paleomagnetic evidence indicates the direction and rate of drift, allowing maps of old continental positions, such as figure 4.2, to be drawn. Although Pangaea split up 200 million years ...
... ROdF matches show when continents were together; once the continents split, the new rocks formed are dissimilar. Paleomagnetic evidence indicates the direction and rate of drift, allowing maps of old continental positions, such as figure 4.2, to be drawn. Although Pangaea split up 200 million years ...
Karson, J.A., and Lawrence, R.M., 1997.
... almost entirely by magmatic accretion. On slow-spreading ridges, the magma budget is more variable. In some places, magmatic construction appears to dominate. Elsewhere, the neovolcanic zone and upper crustal basaltic rock units are discontinuous, and faulting plays a much more important role. In so ...
... almost entirely by magmatic accretion. On slow-spreading ridges, the magma budget is more variable. In some places, magmatic construction appears to dominate. Elsewhere, the neovolcanic zone and upper crustal basaltic rock units are discontinuous, and faulting plays a much more important role. In so ...
VERTIGO (VERtical Transport In the Global Ocean): A study of
... A major finding in VERTIGO is the considerably lower transfer efficiency (Teff) of particulate organic carbon (POC), POC flux 500/150 m, at ALOHA (20%) vs. K2 (50%). This efficiency is higher in the diatomdominated setting at K2 where silica-rich particles dominate the flux at the end of a diatom bloom, ...
... A major finding in VERTIGO is the considerably lower transfer efficiency (Teff) of particulate organic carbon (POC), POC flux 500/150 m, at ALOHA (20%) vs. K2 (50%). This efficiency is higher in the diatomdominated setting at K2 where silica-rich particles dominate the flux at the end of a diatom bloom, ...
EPSL Effects of relative plate motion on the deep structure and
... subducted lithosphere below the Izu-Bonin arc is not continuous in a simple way to the slab below the Mariana arc. The age of subducting lithosphere is an important control in the subduction process [19], but the increase from about 135 Ma at the northern Izu-Bonin trench to over 150 Ma at the Maria ...
... subducted lithosphere below the Izu-Bonin arc is not continuous in a simple way to the slab below the Mariana arc. The age of subducting lithosphere is an important control in the subduction process [19], but the increase from about 135 Ma at the northern Izu-Bonin trench to over 150 Ma at the Maria ...
Unit 1 – Plate Tectonics – april 2012GLC
... benefit, too. Scientists determined that the ocean floor was not flat and featureless, but covered with trenches, crevasses, mountain ridges and volcanoes! After the war when trans-Atlantic telephone cables were being laid, engineers found an undersea mountain range. Oceanographers determined that t ...
... benefit, too. Scientists determined that the ocean floor was not flat and featureless, but covered with trenches, crevasses, mountain ridges and volcanoes! After the war when trans-Atlantic telephone cables were being laid, engineers found an undersea mountain range. Oceanographers determined that t ...
The composition of the continental crust
... xenoliths. A one to one mixture of felsic granulites from Archaean and post-Archaean terrains with not much difference between the two age-divided groups has a tonalitic chemical composition. Mafic xenoliths from the lower crust contain element abundances o f average N - M O R B (Hofmann, 1988) with ...
... xenoliths. A one to one mixture of felsic granulites from Archaean and post-Archaean terrains with not much difference between the two age-divided groups has a tonalitic chemical composition. Mafic xenoliths from the lower crust contain element abundances o f average N - M O R B (Hofmann, 1988) with ...
Subduction styles in the Precambrian
... materials (e.g. rock type or melt) which appear in subsequent figures. For the continental crust, the sediments and the mantle two layers with the same physical properties are distinguished using different colors to better illustrate the deformation. Letters in blocks show rheology which is used for ...
... materials (e.g. rock type or melt) which appear in subsequent figures. For the continental crust, the sediments and the mantle two layers with the same physical properties are distinguished using different colors to better illustrate the deformation. Letters in blocks show rheology which is used for ...
Accumulation of Th, Pb, U, and Ra in marine phytoplankton and its
... we exclude the D. tertiolecta and O. woronichinii data to avoid any possible pH artifacts, thesegeometric means are not altered appreciably (in fact, they increase about twofold). The geometric mean DWCFs in phytoplankton cultures are comparable to those measured in surface ocean particulates and in ...
... we exclude the D. tertiolecta and O. woronichinii data to avoid any possible pH artifacts, thesegeometric means are not altered appreciably (in fact, they increase about twofold). The geometric mean DWCFs in phytoplankton cultures are comparable to those measured in surface ocean particulates and in ...
Diapirs as the source of the sediment signature in arc lavas
... in partial melts of metasediment, but many of these elements are relatively immobile in aqueous fluids1 . The enrichment of these elements, and their correlation with the flux and composition of subducted sediments, has been interpreted to reflect a ‘sediment melt’ signature in arc lavas2–4 . Subduc ...
... in partial melts of metasediment, but many of these elements are relatively immobile in aqueous fluids1 . The enrichment of these elements, and their correlation with the flux and composition of subducted sediments, has been interpreted to reflect a ‘sediment melt’ signature in arc lavas2–4 . Subduc ...
Cape Verde hotspot from the upper crust to the top of the lower mantle
... by a thermal reheating of the lithosphere and/or magmatic underplating and/or dynamic support of upwelling asthenosphere. A joint analysis of gravity (free air anomalies) and seismic data (wide angle seismic reflections) suggests that the first two reasons are unlikely for the Cape Verde archipelago ( ...
... by a thermal reheating of the lithosphere and/or magmatic underplating and/or dynamic support of upwelling asthenosphere. A joint analysis of gravity (free air anomalies) and seismic data (wide angle seismic reflections) suggests that the first two reasons are unlikely for the Cape Verde archipelago ( ...
Sulphur Emission and Transformations at Deep Sea Hydrothermal
... at., 1981) indicate that the emitted sulphur derives largely (up to 90%) from leaching as primary sulphide from basalts (Arnold and Sheppard, 1981) and the smaller portion from the geothermal reduction of seawater sulphate. The latter is largely removed by deposition as anhydrite during the downward ...
... at., 1981) indicate that the emitted sulphur derives largely (up to 90%) from leaching as primary sulphide from basalts (Arnold and Sheppard, 1981) and the smaller portion from the geothermal reduction of seawater sulphate. The latter is largely removed by deposition as anhydrite during the downward ...
Magmatic and tectonic evolution of the North Atlantic Journal of the
... Abstract: The primary aim of the present paper is (1) to review the tectonomagmatic evolution of the North Atlantic, and (2) constrain evolutionary models with new lithosphere strength estimates and interpretation of potential field data north of Iceland. Our interpretations suggest that the breakup ...
... Abstract: The primary aim of the present paper is (1) to review the tectonomagmatic evolution of the North Atlantic, and (2) constrain evolutionary models with new lithosphere strength estimates and interpretation of potential field data north of Iceland. Our interpretations suggest that the breakup ...
The Western Coastal Plains - erc
... characterized by an area of flat low lying land that is situated adjacent to a water body often a sea or ocean. It is also of note that coastal plains are separated from the interior of the larger land mass by other unique features. ...
... characterized by an area of flat low lying land that is situated adjacent to a water body often a sea or ocean. It is also of note that coastal plains are separated from the interior of the larger land mass by other unique features. ...
Plate Tectonics: A Unifying Theory
... As we stated in Chapter 1, plate tectonic theory has had significant and far-reaching consequences in all fields of geology because it provides the basis for relating many seemingly unrelated phenomena. The interactions between moving plates determines the location of continents, ocean basins, and ...
... As we stated in Chapter 1, plate tectonic theory has had significant and far-reaching consequences in all fields of geology because it provides the basis for relating many seemingly unrelated phenomena. The interactions between moving plates determines the location of continents, ocean basins, and ...
View/Open - Earth
... trace element composition suggests a rift-to-drift transition marked by magmatic activity with typical MORB signature, with no contamination by continental lithosphere, but with slight differences in mantle source composition and/or temperature between Thetis and Nereus. Eruption rate, spreading rat ...
... trace element composition suggests a rift-to-drift transition marked by magmatic activity with typical MORB signature, with no contamination by continental lithosphere, but with slight differences in mantle source composition and/or temperature between Thetis and Nereus. Eruption rate, spreading rat ...
Chapter 13 - The Theory of Plate Tectonics
... In 1960, geologists Harry Hess and Robert S. Dietz proposed an explanation of seafloor features. They hypothesized that the seafloor is in a constant state of creation and destruction through a process called seafloor spreading. In the theory of seafloor spreading, new crust emerges from the rif ...
... In 1960, geologists Harry Hess and Robert S. Dietz proposed an explanation of seafloor features. They hypothesized that the seafloor is in a constant state of creation and destruction through a process called seafloor spreading. In the theory of seafloor spreading, new crust emerges from the rif ...
Ocean Drilling Program Scientific Results Volume 124
... seaward of the Cotabato Trench. Another deep, the North Sulawesi Trench, extends parallel to the north arm of Sulawesi (Celebes) and reaches water depths of nearly 5500 m. Active earthquake seismicity associated with both the Cotabato and North Sulawesi trenches documents active subduction along the ...
... seaward of the Cotabato Trench. Another deep, the North Sulawesi Trench, extends parallel to the north arm of Sulawesi (Celebes) and reaches water depths of nearly 5500 m. Active earthquake seismicity associated with both the Cotabato and North Sulawesi trenches documents active subduction along the ...
The Virgin River Shear Zone in the Careen Lake Area: Field
... This paper presents results of fieldwork in the Careen Lake area of northern Saskatchewan which commenced this summer (Figure 1). The area was selected for study because it exhibits a well-exposed section across the Virgin River Shear Zone. This approximately 4.5 km wide zone of mytonitic rocks sepa ...
... This paper presents results of fieldwork in the Careen Lake area of northern Saskatchewan which commenced this summer (Figure 1). The area was selected for study because it exhibits a well-exposed section across the Virgin River Shear Zone. This approximately 4.5 km wide zone of mytonitic rocks sepa ...
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.