Plate boundary deformation between the Pacific and North America
... and magnitude of the total motion accommodated across the zone, however, was unchanged. The small differences in local magnitudes of velocity are a consequence of the fact that all the events since 1994 had a magnitude less than 5.4, where it appears that only earthquakes with magnitudes higher than ...
... and magnitude of the total motion accommodated across the zone, however, was unchanged. The small differences in local magnitudes of velocity are a consequence of the fact that all the events since 1994 had a magnitude less than 5.4, where it appears that only earthquakes with magnitudes higher than ...
Cascadia subducting plate fluids channelled to fore
... inferred to be subducted, that involve a substantial amount of porosity water. Most of the porosity should collapse and the fluid be expelled at shallow depth, although low-grade metamorphosed sediments may continue to a much greater depth. The upper crust has high porosity in both fracture and vesic ...
... inferred to be subducted, that involve a substantial amount of porosity water. Most of the porosity should collapse and the fluid be expelled at shallow depth, although low-grade metamorphosed sediments may continue to a much greater depth. The upper crust has high porosity in both fracture and vesic ...
Numerical comparison of different convergent plate contacts
... pressures and which initially do not contribute to the forcing. The remaining density anomalies (i.e. slab pull forces) are used to drive model deformation and are instantaneously applied at the beginning of the model calculation. The initial bending stresses are not included since we assumed a pre- ...
... pressures and which initially do not contribute to the forcing. The remaining density anomalies (i.e. slab pull forces) are used to drive model deformation and are instantaneously applied at the beginning of the model calculation. The initial bending stresses are not included since we assumed a pre- ...
Mantle Melting Beneath Mid-Ocean Ridges The Harvard community
... say, elements that are incompatible with the crystals remaining in the solid mantle, called “magmaphile” elements) have concentrations that are inversely proportional to the extent of melting. The most abundant element with this behavior is sodium. High extents of melting lead to liquids with low so ...
... say, elements that are incompatible with the crystals remaining in the solid mantle, called “magmaphile” elements) have concentrations that are inversely proportional to the extent of melting. The most abundant element with this behavior is sodium. High extents of melting lead to liquids with low so ...
Magmatic constraints on geodynamic models of subduction in the
... significantly later than the end of basin closure and the onset of continental collision along the Inner Carpathian arc that is thought to have taken place during the Miocene (9–5 Ma). Migration of magmatic activity from NW to SE along the arc may be explained by a corresponding migration of the mag ...
... significantly later than the end of basin closure and the onset of continental collision along the Inner Carpathian arc that is thought to have taken place during the Miocene (9–5 Ma). Migration of magmatic activity from NW to SE along the arc may be explained by a corresponding migration of the mag ...
Andesite and dacite genesis via contrasting processes: the geology
... that some dacites and andesites in recent-arc environments are derived directly from the partial melting of the subducted lithosphere. These cases exist where young and relatively hot oceanic crust is subducting. E1 Valle volcano is unique in that apparently it displays two distinct periods of andes ...
... that some dacites and andesites in recent-arc environments are derived directly from the partial melting of the subducted lithosphere. These cases exist where young and relatively hot oceanic crust is subducting. E1 Valle volcano is unique in that apparently it displays two distinct periods of andes ...
LOW RES
... orthogonal convergence rates determined using the NUVEL1A plate motion model [DeMets et al., 1994]. For the mantle wedge, we use a simple dynamical flow model of Newtonian viscous corner flow [Batchelor, 1967] driven by a no-slip boundary condition along the top of the subducting plate. Mantle-wedge ...
... orthogonal convergence rates determined using the NUVEL1A plate motion model [DeMets et al., 1994]. For the mantle wedge, we use a simple dynamical flow model of Newtonian viscous corner flow [Batchelor, 1967] driven by a no-slip boundary condition along the top of the subducting plate. Mantle-wedge ...
Isostasy and Flexure of the Lithosphere
... depth. Thus, the deflection of a plumb line near a mountain range may well be small, as Bouguer had suspected. Little more appears to have been said on the matter for a further 100 years. The statements made by Boscovich on the compensation of mountains therefore had little impact with leading geolog ...
... depth. Thus, the deflection of a plumb line near a mountain range may well be small, as Bouguer had suspected. Little more appears to have been said on the matter for a further 100 years. The statements made by Boscovich on the compensation of mountains therefore had little impact with leading geolog ...
Percolating Through Volcanic Subsurface Rocks, Seawater is
... The Upflow Zone Buoyancy forces cause the hot fluids to rise rapidly toward the seafloor, much as hot air causes a balloon to rise in the atmosphere. Initially, the upflow is focused along a conduit of high permeability, such as a fault surface. As it reaches shallow depths, the flow may continue t ...
... The Upflow Zone Buoyancy forces cause the hot fluids to rise rapidly toward the seafloor, much as hot air causes a balloon to rise in the atmosphere. Initially, the upflow is focused along a conduit of high permeability, such as a fault surface. As it reaches shallow depths, the flow may continue t ...
39. crustal structure along the leg 152 drilling transect
... crust thins from approximately 28 km thick to almost zero over a maximum distance of 40 km. Variations in present-day crustal thickness are much less because of accretion of thick igneous crust during breakup. Most of the thinning of the continental crust takes place within only 25 km from the mid-s ...
... crust thins from approximately 28 km thick to almost zero over a maximum distance of 40 km. Variations in present-day crustal thickness are much less because of accretion of thick igneous crust during breakup. Most of the thinning of the continental crust takes place within only 25 km from the mid-s ...
On the origin of noble gases in mantle plumes
... magma should be 1500 £ 10¡12 mol g¡1 . Assuming that helium is incompatible and that the newly formed oceanic crust comes from ca. 10% partial melting gives a 4 He content of ca. 150 £ 10 ¡12 mol g¡1 . The uncertainty on this value is at least a factor of two, but we consider for numerical applicati ...
... magma should be 1500 £ 10¡12 mol g¡1 . Assuming that helium is incompatible and that the newly formed oceanic crust comes from ca. 10% partial melting gives a 4 He content of ca. 150 £ 10 ¡12 mol g¡1 . The uncertainty on this value is at least a factor of two, but we consider for numerical applicati ...
Scientific Ocean Drilling of Mid-Ocean Ridge and Ridge
... processes, the seawater-crust chemical exchange and heat flux, and the diversity of subseafloor microbiology. The remainder of the morning of Day 1 was devoted to talks on the engineering and technology of ocean crustal drilling, including an overview of the history of DSDP/ODP/IODP projects, new te ...
... processes, the seawater-crust chemical exchange and heat flux, and the diversity of subseafloor microbiology. The remainder of the morning of Day 1 was devoted to talks on the engineering and technology of ocean crustal drilling, including an overview of the history of DSDP/ODP/IODP projects, new te ...
︎PDF - Fabio Crameri
... lithosphere-scale weak channel maintained by such a mechanism and/or by actual weak sediment that has been advected down into the subduction zone is thought to be key in inducing realistic, single-sided subduction by providing lubrication at the plate interface [Lenardic and Kaula, 1994; Tagawa et a ...
... lithosphere-scale weak channel maintained by such a mechanism and/or by actual weak sediment that has been advected down into the subduction zone is thought to be key in inducing realistic, single-sided subduction by providing lubrication at the plate interface [Lenardic and Kaula, 1994; Tagawa et a ...
Science Article PDF - Geological Society of America
... and tectonic elements are shown in blue (for older features) and green (younger features). Arrows indicate North America (NA) absolute motion and oceanic plate relative motions. Transform (solid) and subduction (toothed) plate boundaries are shown near western coastline. This hotspot system initiate ...
... and tectonic elements are shown in blue (for older features) and green (younger features). Arrows indicate North America (NA) absolute motion and oceanic plate relative motions. Transform (solid) and subduction (toothed) plate boundaries are shown near western coastline. This hotspot system initiate ...
Crustal structure of the ultra-slow spreading Knipovich Ridge, North
... north of a topographic high occurring at *76°300 N. Based on the bathymetry available at this time we believed that underlying crust could be amagmatic. However, a study by Hellevang and Pedersen (2005) demonstrated the magmatic nature of the entire ridge segment. The first line, acquired along an a ...
... north of a topographic high occurring at *76°300 N. Based on the bathymetry available at this time we believed that underlying crust could be amagmatic. However, a study by Hellevang and Pedersen (2005) demonstrated the magmatic nature of the entire ridge segment. The first line, acquired along an a ...
An ultraslow-spreading class of ocean ridge
... unrecognized class of accretionary plate boundary structure and can assume any orientation, with angles relative to the spreading direction ranging from orthogonal to acute. These amagmatic segments sometimes coexist with magmatic ridge segments for millions of years to form stable plate boundaries, ...
... unrecognized class of accretionary plate boundary structure and can assume any orientation, with angles relative to the spreading direction ranging from orthogonal to acute. These amagmatic segments sometimes coexist with magmatic ridge segments for millions of years to form stable plate boundaries, ...
An ultraslow-spreading class of ocean ridge
... unrecognized class of accretionary plate boundary structure and can assume any orientation, with angles relative to the spreading direction ranging from orthogonal to acute. These amagmatic segments sometimes coexist with magmatic ridge segments for millions of years to form stable plate boundaries, ...
... unrecognized class of accretionary plate boundary structure and can assume any orientation, with angles relative to the spreading direction ranging from orthogonal to acute. These amagmatic segments sometimes coexist with magmatic ridge segments for millions of years to form stable plate boundaries, ...
Crustal structure of the Hatton and the conjugate east Greenland
... margins is unhelpful because there is some igneous activity on all rifted margins; indeed, by the time that seafloor spreading has started, the crust adjacent to all rifted margins is 100% igneous, as it generates oceanic crust. But the volcanic versus nonvolcanic distinction remains useful in place ...
... margins is unhelpful because there is some igneous activity on all rifted margins; indeed, by the time that seafloor spreading has started, the crust adjacent to all rifted margins is 100% igneous, as it generates oceanic crust. But the volcanic versus nonvolcanic distinction remains useful in place ...
The Caribbean Ocean Plateau – an overview
... Jamaica, Belize, Trinidad, Aruba, Curaçao and northern and western Colombia are stratigraphically and petrologically linked to this plateau. They were emplaced during compression at the end of the Santonian. Fossils within the complex are dated mainly Albian through Santonian, but there are Campania ...
... Jamaica, Belize, Trinidad, Aruba, Curaçao and northern and western Colombia are stratigraphically and petrologically linked to this plateau. They were emplaced during compression at the end of the Santonian. Fossils within the complex are dated mainly Albian through Santonian, but there are Campania ...
Inclusions in Sublithospheric Diamonds
... Gasparik 2002). However, plate tectonics, the standard model in Earth sciences, provides a mechanism in accord with the petrological, geochemical, and geophysical constraints on the composition of Earth’s mantle and the evidence against the long-term survival of extreme compositional stratification. ...
... Gasparik 2002). However, plate tectonics, the standard model in Earth sciences, provides a mechanism in accord with the petrological, geochemical, and geophysical constraints on the composition of Earth’s mantle and the evidence against the long-term survival of extreme compositional stratification. ...
A model to explain the various paradoxes associated with mantle
... FIG. 2. The Plate Model. High R basalts contain a component from a high 3HeyU reservoir rather than a high 3He-undegassed reservoir. Magma degasses CO2 and He at shallow depth that are partially trapped in fluid inclusions or vugs in refractory (U, Th-poor) shallow mantle, (high 3HeyU). The 3Hey4He ...
... FIG. 2. The Plate Model. High R basalts contain a component from a high 3HeyU reservoir rather than a high 3He-undegassed reservoir. Magma degasses CO2 and He at shallow depth that are partially trapped in fluid inclusions or vugs in refractory (U, Th-poor) shallow mantle, (high 3HeyU). The 3Hey4He ...
mcrinterpslide - Northwestern University
... of heating a pot of water on a stove. As the water on the bottom gets hotter, it expands, becomes less dense, and rises to the top. Once it gets there, it cools, becomes denser, and sinks again. This process of hot fluid rising and cold fluid sinking is called convection. ...
... of heating a pot of water on a stove. As the water on the bottom gets hotter, it expands, becomes less dense, and rises to the top. Once it gets there, it cools, becomes denser, and sinks again. This process of hot fluid rising and cold fluid sinking is called convection. ...
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.