The subduction dichotomy of strong plates and weak
... curvature and with the appropriate radius. Figure 4 shows the radius of curvature calculations for the same model over time. For each of the three methods, the relative size of the resultant radii of curvature changes during the model run. The first movement of the slabs is due to the slabs relaxing ...
... curvature and with the appropriate radius. Figure 4 shows the radius of curvature calculations for the same model over time. For each of the three methods, the relative size of the resultant radii of curvature changes during the model run. The first movement of the slabs is due to the slabs relaxing ...
Age, spreading rates, and spreading asymmetry of the world`s ocean
... hot spots. We also use the new age grid to compute global residual basement depth grids from the difference between observed oceanic basement depth and predicted depth using three alternative age-depth relationships. The new set of grids helps to investigate prominent negative depth anomalies, which ...
... hot spots. We also use the new age grid to compute global residual basement depth grids from the difference between observed oceanic basement depth and predicted depth using three alternative age-depth relationships. The new set of grids helps to investigate prominent negative depth anomalies, which ...
Seismic evidence for a chemical heterogeneity in the midmantle: A
... of the mineral assemblages of basalt at mid-lower mantle conditions is still not enough to provide robust inference. Moreover, slab associated high-velocity anomalies (hereafter referred to as HVAs) are not observed by global tomographic models [van der Hilst et al., 1997; Grand et al., 1997; Fukao ...
... of the mineral assemblages of basalt at mid-lower mantle conditions is still not enough to provide robust inference. Moreover, slab associated high-velocity anomalies (hereafter referred to as HVAs) are not observed by global tomographic models [van der Hilst et al., 1997; Grand et al., 1997; Fukao ...
Derived From a Flow Model of Subduction
... Department o• Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts A simple viscous flow model of a subduction zone is used to calculate the deformation within continental lithosphere above a subducting slab. Our formulation accounts for two forces that dominate the deformation ...
... Department o• Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts A simple viscous flow model of a subduction zone is used to calculate the deformation within continental lithosphere above a subducting slab. Our formulation accounts for two forces that dominate the deformation ...
the origin of modern chiapanecan volcanic arc in southern mexico
... America trench (MAT). The subducting Cocos slab lies ~ 200 km below the MCVA, whereas the majority of subduction related volcanic arcs are located where the slab is at ~ 100 km depth. Second, although there is a little variation of the slab dip beneath Chiapas (40 - 45°) (Rebollar et al., 1999), the ...
... America trench (MAT). The subducting Cocos slab lies ~ 200 km below the MCVA, whereas the majority of subduction related volcanic arcs are located where the slab is at ~ 100 km depth. Second, although there is a little variation of the slab dip beneath Chiapas (40 - 45°) (Rebollar et al., 1999), the ...
PT Teacher Clarification
... 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. ...
... 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. ...
Non-hotspot formation of volcanic chains
... (W150 km) lineations [11], although this correlation is not perfect and some chains cross from troughs onto crests [11], while in other places, volcanic activity in an active ¢eld covers several troughs and crests [10]. The Polynesian island chains instead typically fall on the crests of medium wave ...
... (W150 km) lineations [11], although this correlation is not perfect and some chains cross from troughs onto crests [11], while in other places, volcanic activity in an active ¢eld covers several troughs and crests [10]. The Polynesian island chains instead typically fall on the crests of medium wave ...
Isostasy
... Distribution of elevations: two preferred elevations => fundamental difference between ocean and continents Continents ~ granite (2.67), oceans ~ basalts (3.3) => idea that Earth’s elevations are supported hydrostatically ...
... Distribution of elevations: two preferred elevations => fundamental difference between ocean and continents Continents ~ granite (2.67), oceans ~ basalts (3.3) => idea that Earth’s elevations are supported hydrostatically ...
22.1 Earth`s Structure - Weird Science With Mrs. Niki
... • The mantle is composed mainly of silicates. It is rich in iron and magnesium, and so is denser throughout than the crust. ...
... • The mantle is composed mainly of silicates. It is rich in iron and magnesium, and so is denser throughout than the crust. ...
unit plan - Achievement First
... Plates collide, move apart, or slide past on another. Most volcanic activity and mountain building occur at the boundaries of these plates, often resulting in earthquakes. The interior of Earth is hot. Heat flow and movement of material within Earth cause sections of Earth’s crust to move. This may ...
... Plates collide, move apart, or slide past on another. Most volcanic activity and mountain building occur at the boundaries of these plates, often resulting in earthquakes. The interior of Earth is hot. Heat flow and movement of material within Earth cause sections of Earth’s crust to move. This may ...
Tectonically asymmetric Earth - Dipartimento di Scienze della Terra
... invoked for microplates, and the effects of adjacent plates. GPS data of the last decades have shown that plates now move at speeds and trends quite similar to those of the geologic past (based on magnetic anomalies and subduction zones age constraints), confirming the existence of a sort of “tectoni ...
... invoked for microplates, and the effects of adjacent plates. GPS data of the last decades have shown that plates now move at speeds and trends quite similar to those of the geologic past (based on magnetic anomalies and subduction zones age constraints), confirming the existence of a sort of “tectoni ...
The Emperor Seamounts: Southward Motion
... rapid (over 40 mm yr −1) motion of the Hawaiian hotspot plume during Late Cretaceous to Early Tertiary times (81-47 Ma). Evidence for motion of the Hawaiian plume affects models of mantle convection and plate tectonics, changing our understanding of terrestrial dynamics. The concept of an age-progre ...
... rapid (over 40 mm yr −1) motion of the Hawaiian hotspot plume during Late Cretaceous to Early Tertiary times (81-47 Ma). Evidence for motion of the Hawaiian plume affects models of mantle convection and plate tectonics, changing our understanding of terrestrial dynamics. The concept of an age-progre ...
Weathering, Erosion and Mass Movement
... rocks in same direction as the wave travels • are refracted by Earth’s core • are refracted, or bent, by Earth’s outer core. • Absence of this kind of waves results in a ...
... rocks in same direction as the wave travels • are refracted by Earth’s core • are refracted, or bent, by Earth’s outer core. • Absence of this kind of waves results in a ...
Unit 1 – Plate Tectonics – april 2012GLC
... Paleoglaciation: Evidence suggests that vast ice sheets existed in South America, Africa, India, Australia, and Antarctica about 250 million years ago. However, many of these areas are tropical today. The current position of the continents would lead one to believe that glaciers must have existed in ...
... Paleoglaciation: Evidence suggests that vast ice sheets existed in South America, Africa, India, Australia, and Antarctica about 250 million years ago. However, many of these areas are tropical today. The current position of the continents would lead one to believe that glaciers must have existed in ...
PDF (Chapter 10. Isotopes)
... various processes in a planet's history. The unstable isotopes most useful in geochemistry have a wide range of decay constants, or half-lives, and can be used to infer processes occurring over the entire age of the Earth (Table 10-1). In addition, isotopes can be used as tracers and in this regard ...
... various processes in a planet's history. The unstable isotopes most useful in geochemistry have a wide range of decay constants, or half-lives, and can be used to infer processes occurring over the entire age of the Earth (Table 10-1). In addition, isotopes can be used as tracers and in this regard ...
Ch9.1 - What Is the Ocean Floor Like (Part 1)
... beneath the ocean. s The continents are made of continental crust. s Continental crust is made mostly of granite. s It is about 20-30 miles thick. s Oceanic crust is thinner and denser than continental crust. s The crust below the ocean is about 3-6 miles thick and is made mostly of basalt. ...
... beneath the ocean. s The continents are made of continental crust. s Continental crust is made mostly of granite. s It is about 20-30 miles thick. s Oceanic crust is thinner and denser than continental crust. s The crust below the ocean is about 3-6 miles thick and is made mostly of basalt. ...
Divergent Boundaries Undersea mountains forty
... – Seamounts and volcanic islands • Submarine volcanoes are called seamounts – Over a million seamounts exist – Found in all ocean floors but most common in the Pacific – Many form near oceanic ridges or over a hot spot ...
... – Seamounts and volcanic islands • Submarine volcanoes are called seamounts – Over a million seamounts exist – Found in all ocean floors but most common in the Pacific – Many form near oceanic ridges or over a hot spot ...
PDF (Chapter 12. The Shape of the Earth, Heat Flow and Convection)
... Older seafloor does not follow this simple relationship, being shallower than predicted. There are large portions of the ocean floor whose depth cannot be explained by simple thermal models; these include oceanic islands, hotspot swells, aseismic ridges and oceanic plateaus as well as other areas wh ...
... Older seafloor does not follow this simple relationship, being shallower than predicted. There are large portions of the ocean floor whose depth cannot be explained by simple thermal models; these include oceanic islands, hotspot swells, aseismic ridges and oceanic plateaus as well as other areas wh ...
Iceland is cool: An origin for the Iceland volcanic province in the
... mid-Atlantic ridge (MAR) where it crosses the Caledonian suture. In the context of a plume, this is a coincidence. For a mantle plume currently beneath Iceland to have been fixed relative to other Atlantic and Indian ocean hotspots, it must have migrated southeastwards at a rate of ~ 2 cm/a relative ...
... mid-Atlantic ridge (MAR) where it crosses the Caledonian suture. In the context of a plume, this is a coincidence. For a mantle plume currently beneath Iceland to have been fixed relative to other Atlantic and Indian ocean hotspots, it must have migrated southeastwards at a rate of ~ 2 cm/a relative ...
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.