Imaging the mantle transition zone beneath eastern and central
... found that the lithosphere beneath the Precambrian Ordos and Sichuan basins has substantially high seismic velocities and the high velocity regions extend to at least 250 km deep. The 410-km beneath the two basins are ∼10 km shallower than the surrounding areas, suggesting the shoaling of the 410-km ...
... found that the lithosphere beneath the Precambrian Ordos and Sichuan basins has substantially high seismic velocities and the high velocity regions extend to at least 250 km deep. The 410-km beneath the two basins are ∼10 km shallower than the surrounding areas, suggesting the shoaling of the 410-km ...
6 2D thermo-mecanical finite element models of n Contents
... to more than 40 km, which we correlate with the steepening (up to 40°) of the subducting slab (Fig. 6.2-E). The thinnest oceanic crust (∼25 km) is seen below the trench area. Northward, thickening occurs in relation to the Troodos Ophiolite, the detachment depth of which is uncertain. This crustal t ...
... to more than 40 km, which we correlate with the steepening (up to 40°) of the subducting slab (Fig. 6.2-E). The thinnest oceanic crust (∼25 km) is seen below the trench area. Northward, thickening occurs in relation to the Troodos Ophiolite, the detachment depth of which is uncertain. This crustal t ...
2003108 - Geological Society of America
... (as inferred from earthquakes by Pardo and Suárez, 1995) are included for reference. Approximate locations of Deep Sea Drilling Project legs 66 (L66), 67 (L67), and 84 (L84) are also indicated. Our geochemical database for the MVB (411 individual samples) concerns a wider area to the East and to the ...
... (as inferred from earthquakes by Pardo and Suárez, 1995) are included for reference. Approximate locations of Deep Sea Drilling Project legs 66 (L66), 67 (L67), and 84 (L84) are also indicated. Our geochemical database for the MVB (411 individual samples) concerns a wider area to the East and to the ...
A tensile, flexural model for the initiation of subduction
... necessary to balance the component of the plate’s weight directed down the margin slope. We show that this tension can more than offset ridge push. In our model, an important additional tension arises from basal shear tractions resisting the plate’s motion away from the mid-ocean ridge, although the ...
... necessary to balance the component of the plate’s weight directed down the margin slope. We show that this tension can more than offset ridge push. In our model, an important additional tension arises from basal shear tractions resisting the plate’s motion away from the mid-ocean ridge, although the ...
Structural style and tectonic evolution of the easternmost Gulf of
... Observations from distal rifted margins in present day magma-poor rifted margins led to the discovery of hyperextended crust and exhumed sub-continental mantle. This finding allowed to better figure out how thinning process are accommodate by tectonic structures, forming various crustal domains, as ...
... Observations from distal rifted margins in present day magma-poor rifted margins led to the discovery of hyperextended crust and exhumed sub-continental mantle. This finding allowed to better figure out how thinning process are accommodate by tectonic structures, forming various crustal domains, as ...
Why subduction zones are curved - Harvard John A. Paulson School
... While small loads lead to a gentle flattening of the sphere, initiation of a dimpled indentation occurs only when the applied load crosses a threshold. This implies, for example, that an intact eggshell can support much larger normal loads than a flat sheet of the same thickness and stiffness becaus ...
... While small loads lead to a gentle flattening of the sphere, initiation of a dimpled indentation occurs only when the applied load crosses a threshold. This implies, for example, that an intact eggshell can support much larger normal loads than a flat sheet of the same thickness and stiffness becaus ...
Chapter 7 Plate Tectonics
... Scientists also divide Earth into five layers based on physical properties. The outer layer is the lithosphere. It is a cool, stiff layer that includes all of the crust and a small part of the upper mantle. The lithosphere is divided into pieces. These pieces move slowly over Earth’s surface. The as ...
... Scientists also divide Earth into five layers based on physical properties. The outer layer is the lithosphere. It is a cool, stiff layer that includes all of the crust and a small part of the upper mantle. The lithosphere is divided into pieces. These pieces move slowly over Earth’s surface. The as ...
Slide 1 - Fort Thomas Independent Schools
... continental drift. He provided abundant geologic and paleontologic evidence to show that the continents were once united into one supercontinent he named Pangaea. Unfortunately, Wegener could not explain how the continents moved, and most geologists ignored his ideas. • The hypothesis of continental ...
... continental drift. He provided abundant geologic and paleontologic evidence to show that the continents were once united into one supercontinent he named Pangaea. Unfortunately, Wegener could not explain how the continents moved, and most geologists ignored his ideas. • The hypothesis of continental ...
Unit 1 – Plate Tectonics – april 2012GLC
... The boundary between two plates that are moving apart is called a divergent plate boundary or a spreading center because the plates are diverging, or spreading apart. As the plates spread apart, the gap between them is filled with magma that oozes up from the hot mantle. The molten rock cools slowly ...
... The boundary between two plates that are moving apart is called a divergent plate boundary or a spreading center because the plates are diverging, or spreading apart. As the plates spread apart, the gap between them is filled with magma that oozes up from the hot mantle. The molten rock cools slowly ...
Sine et al.
... seismometers (La RISTRA 1.5) were deployed from the NW end of the La RISTRA 1.0 array, crossed the CP, and extended into the GB at 20 km intervals. The combined La RISTRA 1.0 and 1.5 experiments facilitate imaging of crust and upper mantle seismic structure across a 1400 km transect encompassing fo ...
... seismometers (La RISTRA 1.5) were deployed from the NW end of the La RISTRA 1.0 array, crossed the CP, and extended into the GB at 20 km intervals. The combined La RISTRA 1.0 and 1.5 experiments facilitate imaging of crust and upper mantle seismic structure across a 1400 km transect encompassing fo ...
Ocean Upper Mantle Initiative: The oceanic lithosphere and its
... does the thicker plate cause large compressional stresses in the thinner plate, and may this generate intraplate thrust earthquakes? What is our understanding of intraplate earthquakes in general, and are they affected by asthenospheric mantle flow? These questions are not only of fundamental import ...
... does the thicker plate cause large compressional stresses in the thinner plate, and may this generate intraplate thrust earthquakes? What is our understanding of intraplate earthquakes in general, and are they affected by asthenospheric mantle flow? These questions are not only of fundamental import ...
Lesson Plans for Plate Tectonics
... (use motion demos below Dynamic Earth map on website for today’s lab.) Classwork, Part 2: Obtain and look over the “‘I Can’ Plate Tectonics Objectives – Learning Target Analysis” sheet (T/Q) to determine where you are in your learning. 3 Nov: Classwork, part 1: Organize binders and locate the “Inter ...
... (use motion demos below Dynamic Earth map on website for today’s lab.) Classwork, Part 2: Obtain and look over the “‘I Can’ Plate Tectonics Objectives – Learning Target Analysis” sheet (T/Q) to determine where you are in your learning. 3 Nov: Classwork, part 1: Organize binders and locate the “Inter ...
A tensile, flexural model for the initiation of subduction
... Lay 1986). Pulses of tectonic stress associated with broader plate reorganizations have also been called upon (Erickson & Arkani-Hamed 1993). Major tectonic events, such as the India-Asia collision, and complex plate interactions, as in the western Pacific, d o appear to cause polarity reversals, tr ...
... Lay 1986). Pulses of tectonic stress associated with broader plate reorganizations have also been called upon (Erickson & Arkani-Hamed 1993). Major tectonic events, such as the India-Asia collision, and complex plate interactions, as in the western Pacific, d o appear to cause polarity reversals, tr ...
Geology: Effect of subducting sea-floor roughness on fore
... Fault kinematics and uplift in the Costa Rican fore arc of the Middle America convergent margin are controlled to a large extent by roughness on the subducting Cocos plate. Along the northwest flank of the incoming Cocos Ridge, seafloor is characterized by short wavelength roughness related to north ...
... Fault kinematics and uplift in the Costa Rican fore arc of the Middle America convergent margin are controlled to a large extent by roughness on the subducting Cocos plate. Along the northwest flank of the incoming Cocos Ridge, seafloor is characterized by short wavelength roughness related to north ...
Geological Society of America Bulletin
... region batholith was sheared off and displaced deeper into the mantle. The lithosphere beneath the greater Sierra Nevada batholith to the north was left intact until mid-Miocene time, when fragments of it were entrained as volcanic xenoliths. The Laramide slab was evidently segmented into a shallow ...
... region batholith was sheared off and displaced deeper into the mantle. The lithosphere beneath the greater Sierra Nevada batholith to the north was left intact until mid-Miocene time, when fragments of it were entrained as volcanic xenoliths. The Laramide slab was evidently segmented into a shallow ...
The Farallon-Aluk ridge collision with South America: Implications
... active plates transform margins, it can be stated that once the collision of a divergent ridge enables the coupling of the divergent ocean-floor to the continental crust through a transform fault, then the subducted plate detaches (or unzips), leaving a slab window behind. This new situation should r ...
... active plates transform margins, it can be stated that once the collision of a divergent ridge enables the coupling of the divergent ocean-floor to the continental crust through a transform fault, then the subducted plate detaches (or unzips), leaving a slab window behind. This new situation should r ...
On the origin of El Chichón volcano and subduction of
... been proposed to occur along deep faults where oceanic plates bend upon entering into subduction (Peacock, 2001; Ranero et al., 2003) or along transform faults (Omori et al., 2002). Ranero et al. (2003) and Omori et al. (2002) suggest that partial serpentinization of the upper mantle offshore Nicara ...
... been proposed to occur along deep faults where oceanic plates bend upon entering into subduction (Peacock, 2001; Ranero et al., 2003) or along transform faults (Omori et al., 2002). Ranero et al. (2003) and Omori et al. (2002) suggest that partial serpentinization of the upper mantle offshore Nicara ...
Plate tectonics - Free
... The key principle of plate tectonics is that the lithosphere exists as separate and distinct tectonic plates, which ride on the fluid-like (visco-elastic solid) asthenosphere. Plate motions range up to a typical 10–40 mm/year (MidAtlantic Ridge; about as fast as fingernails grow), to about 160 mm/year ...
... The key principle of plate tectonics is that the lithosphere exists as separate and distinct tectonic plates, which ride on the fluid-like (visco-elastic solid) asthenosphere. Plate motions range up to a typical 10–40 mm/year (MidAtlantic Ridge; about as fast as fingernails grow), to about 160 mm/year ...
Internal forces: plate tectonics
... they stop moving; this is the convergent margin. In this zone the advancing edge of a plate meets another plate and is driven under it, often with violent consequences, creating volcanoes and earthquakes (and possibly tsunamis). For this reason they are often known as destructive margins. The bounda ...
... they stop moving; this is the convergent margin. In this zone the advancing edge of a plate meets another plate and is driven under it, often with violent consequences, creating volcanoes and earthquakes (and possibly tsunamis). For this reason they are often known as destructive margins. The bounda ...
Growth and mixing dynamics of mantle wedge plumes
... Recent work suggests that hydrated partially molten thermal-chemical plumes that originate from subducted slab as a consequence of Rayleigh-Taylor instability are responsible for the heterogeneous composition of the mantle wedge. We use a two-dimensional ultrahighresolution numerical simulation invo ...
... Recent work suggests that hydrated partially molten thermal-chemical plumes that originate from subducted slab as a consequence of Rayleigh-Taylor instability are responsible for the heterogeneous composition of the mantle wedge. We use a two-dimensional ultrahighresolution numerical simulation invo ...
Dynamics of continental collision: influence of the plate contact
... Vos et al. 2007). This implies that when crust and mantle lithosphere subduct, their speed and direction can be different. This process, known as delamination, was proposed originally by Bird (1978) to explain some of the tectonic features in the Himalayas and it is, indeed, a suitable mechanism to ...
... Vos et al. 2007). This implies that when crust and mantle lithosphere subduct, their speed and direction can be different. This process, known as delamination, was proposed originally by Bird (1978) to explain some of the tectonic features in the Himalayas and it is, indeed, a suitable mechanism to ...
Creation and evolution of the oceanic lithosphere: contributions from
... sheeted dikes are underlain by gabbro and mantle peridotite. But gabbros and mantle peridotites are exposed on the seafloor at slow spreading ridges, even in wide regions where the seismic structure appears to be “normally” layered. In addition, many ophiolite volcanic rocks have chemical affinities ...
... sheeted dikes are underlain by gabbro and mantle peridotite. But gabbros and mantle peridotites are exposed on the seafloor at slow spreading ridges, even in wide regions where the seismic structure appears to be “normally” layered. In addition, many ophiolite volcanic rocks have chemical affinities ...
Dynamical effects of subducting ridges: insights from 3
... after the plateau has been entirely incorporated into the subduction zone. We compare experiments with the present-day subduction zone below South America. Experiments suggest that a modest ridge perpendicular to the trench such as the present-day Juan Fernandez ridge is not buoyant enough to modify ...
... after the plateau has been entirely incorporated into the subduction zone. We compare experiments with the present-day subduction zone below South America. Experiments suggest that a modest ridge perpendicular to the trench such as the present-day Juan Fernandez ridge is not buoyant enough to modify ...
Plate Tectonics PuzzleMap User Guide
... Plate tectonics is a key standards-based topic taught in earth science classrooms throughout the United States. The purpose of this map is to help educators (teachers, museum tour guides, etc.) teach students about the forces that are responsible for earthquakes, mountains, volcanoes, and other natu ...
... Plate tectonics is a key standards-based topic taught in earth science classrooms throughout the United States. The purpose of this map is to help educators (teachers, museum tour guides, etc.) teach students about the forces that are responsible for earthquakes, mountains, volcanoes, and other natu ...
(43.5-46°S): Implications for Magma Genesis
... below Palena may be only as deep as 110 km. Ignoring these uncertainties in slab depth below the volcanic front and back-arc MEC in this region of the SSVZ, it is still clear that the LA Palena group basalts occur at about the same distance behind the volcanic front and at the very same depth above ...
... below Palena may be only as deep as 110 km. Ignoring these uncertainties in slab depth below the volcanic front and back-arc MEC in this region of the SSVZ, it is still clear that the LA Palena group basalts occur at about the same distance behind the volcanic front and at the very same depth above ...
Oceanic trench
The oceanic trenches are hemispheric-scale long but narrow topographic depressions of the sea floor. They are also the deepest parts of the ocean floor. Oceanic trenches are a distinctive morphological feature of convergent plate boundaries, along which lithospheric plates move towards each other at rates that vary from a few mm to over ten cm per year. A trench marks the position at which the flexed, subducting slab begins to descend beneath another lithospheric slab. Trenches are generally parallel to a volcanic island arc, and about 200 km (120 mi) from a volcanic arc. Oceanic trenches typically extend 3 to 4 km (1.9 to 2.5 mi) below the level of the surrounding oceanic floor. The greatest ocean depth to be sounded is in the Challenger Deep of the Mariana Trench, at a depth of 11,034 m (36,201 ft) below sea level. Oceanic lithosphere moves into trenches at a global rate of about 3 km2/yr.