Geological Society of America Bulletin
... biotic changes, including the onset of Northern Hemisphere glaciations, the strengthening of the Gulf Stream current (e.g., Burton et al., 1997; Haug et al., 2001; Lear et al., 2003), the Great American Interchange of land mammals (Marshall et al., 1982), and an increase in Caribbean molluscan diver ...
... biotic changes, including the onset of Northern Hemisphere glaciations, the strengthening of the Gulf Stream current (e.g., Burton et al., 1997; Haug et al., 2001; Lear et al., 2003), the Great American Interchange of land mammals (Marshall et al., 1982), and an increase in Caribbean molluscan diver ...
the Zero Paradox Noble Gas Mantle
... before being lost to space (Allègre et al., 1986; Torgersen, 1989b). For the other noble gases, such as Ar, the atmosphere becomes their final resting place. The other important feature of noble gases is that they are highly depleted in the Earth relative to Solar abundances. This results in small n ...
... before being lost to space (Allègre et al., 1986; Torgersen, 1989b). For the other noble gases, such as Ar, the atmosphere becomes their final resting place. The other important feature of noble gases is that they are highly depleted in the Earth relative to Solar abundances. This results in small n ...
Characteristic thermal regimes of plate tectonics
... From a geological perspective, we may break down into several components the question of when plate tectonics began on Earth. For example, we may ask when did the lithosphere first behave as a mosaic of plates—that is, a mosaic of largely torsionally rigid lithosphere elements bounded by zones of ge ...
... From a geological perspective, we may break down into several components the question of when plate tectonics began on Earth. For example, we may ask when did the lithosphere first behave as a mosaic of plates—that is, a mosaic of largely torsionally rigid lithosphere elements bounded by zones of ge ...
PDF (Chapter 3. The Crust and Upper Mantle)
... Moho is a sharp seismological boundary and in some regions appears to be laminated. There are three major crustal types-continental, transitional and oceanic. Oceanic crust generally ranges from 5 to 15 km in thickness and comprises 60 percent of the total crust by area and more than 20 percent by v ...
... Moho is a sharp seismological boundary and in some regions appears to be laminated. There are three major crustal types-continental, transitional and oceanic. Oceanic crust generally ranges from 5 to 15 km in thickness and comprises 60 percent of the total crust by area and more than 20 percent by v ...
Driving the upper plate surface deformation by slab
... induced by the down-going slab dominates the deep dynamics during the first subduction event (Fig. 4a). This toroidal flow occurs both below C1 and through the opening slab window. At the surface, extensional and compressional deformation occurs in the back-arc and collisional domain, respectively. Cr ...
... induced by the down-going slab dominates the deep dynamics during the first subduction event (Fig. 4a). This toroidal flow occurs both below C1 and through the opening slab window. At the surface, extensional and compressional deformation occurs in the back-arc and collisional domain, respectively. Cr ...
Earth Sciences Department
... • To write field reports & laboratory reports based on original observations. ...
... • To write field reports & laboratory reports based on original observations. ...
Geology - SCERT - Government of Kerala
... What differences in crystal size might you expect between two rocks, one formed at surface and the other at depth? ...
... What differences in crystal size might you expect between two rocks, one formed at surface and the other at depth? ...
Origins of the plume hypothesis and some of its
... from below. Hot material rises buoyantly through the mantle through cylindrical lowviscosity conduits. The deep part of the issue would be settled if one could resolve the structure at midmantle depths. Seismic data do provide evidence that such conduits exist in the expected places (Montelli et al. ...
... from below. Hot material rises buoyantly through the mantle through cylindrical lowviscosity conduits. The deep part of the issue would be settled if one could resolve the structure at midmantle depths. Seismic data do provide evidence that such conduits exist in the expected places (Montelli et al. ...
Author`s personal copy
... waves. At the first arrivals this wave is weak, whereas at the later ones its intensity increases at offsets of 800–1300 km (Figs. 2 and 4). Sometimes, the records of PL continue the multi-phase record of PN2; therefore, these waves are difficult to separate (Figs. 2 and 3). The PL waves are refractio ...
... waves. At the first arrivals this wave is weak, whereas at the later ones its intensity increases at offsets of 800–1300 km (Figs. 2 and 4). Sometimes, the records of PL continue the multi-phase record of PN2; therefore, these waves are difficult to separate (Figs. 2 and 3). The PL waves are refractio ...
Depleted lithosphere, cold, trapped asthenosphere, and frozen melt
... section of the flat slab is characterized by low P-wave velocities, high S-wave velocities, and low Vp / Vs ratios. As the slab begins to transition to a more normal dip to the south, the mantle above it changes as well. Above this “transition zone”, the mantle is characterized by high P-wave veloci ...
... section of the flat slab is characterized by low P-wave velocities, high S-wave velocities, and low Vp / Vs ratios. As the slab begins to transition to a more normal dip to the south, the mantle above it changes as well. Above this “transition zone”, the mantle is characterized by high P-wave veloci ...
Hewitt/Lyons/Suchocki/Yeh, Conceptual Integrated Science
... Even though the temperature at depth is hotter than rock’s melting point, the rocks at depth are solid, because ...
... Even though the temperature at depth is hotter than rock’s melting point, the rocks at depth are solid, because ...
Labrador Sea and Baffin Bay opening and magmatism explained by
... conclusion that is concordant with the suggestion by Alsulami et al. (2015) that the role of a ...
... conclusion that is concordant with the suggestion by Alsulami et al. (2015) that the role of a ...
Archaean plate tectonics revisited 1. Heat flow, spreading rate, and
... the slab causing it to sink further ...
... the slab causing it to sink further ...
IM_chapter2 Plate Tectonics
... good non-technical summary of the controversy is discussed on about.com, which includes links to other articles: http://geology.about.com/od/platetectonics/a/nohotspots.htm Topic 5. Is Plate Tectonics Inevitable? Plate tectonics may be a necessary condition for life, so the existence of plate tecton ...
... good non-technical summary of the controversy is discussed on about.com, which includes links to other articles: http://geology.about.com/od/platetectonics/a/nohotspots.htm Topic 5. Is Plate Tectonics Inevitable? Plate tectonics may be a necessary condition for life, so the existence of plate tecton ...
Chapter 2 - Test Bank 1
... good non-technical summary of the controversy is discussed on about.com, which includes links to other articles: http://geology.about.com/od/platetectonics/a/nohotspots.htm Topic 5. Is Plate Tectonics Inevitable? Plate tectonics may be a necessary condition for life, so the existence of plate tecton ...
... good non-technical summary of the controversy is discussed on about.com, which includes links to other articles: http://geology.about.com/od/platetectonics/a/nohotspots.htm Topic 5. Is Plate Tectonics Inevitable? Plate tectonics may be a necessary condition for life, so the existence of plate tecton ...
Lecture 6 - Mantle and Basalts
... The enrichment of various minor and large-ion-lithophile elements in OIB’s suggests that their parent plumes originate in the lower mantle. There is good evidence that their source may include portions of subducted slabs that have descended to the mantle-core boundary. Much of the heat necessary for ...
... The enrichment of various minor and large-ion-lithophile elements in OIB’s suggests that their parent plumes originate in the lower mantle. There is good evidence that their source may include portions of subducted slabs that have descended to the mantle-core boundary. Much of the heat necessary for ...
Convergent plate margin dynamics
... radioactive decay (Holmes, 1928). The idea of sub-crustal convection in the Earth's mantle was not new and had already been proposed a century earlier (Hopkins, 1839; Fisher, 1881). In the beginning of the twentieth century it was proposed by several geoscientists that these mantle convection curren ...
... radioactive decay (Holmes, 1928). The idea of sub-crustal convection in the Earth's mantle was not new and had already been proposed a century earlier (Hopkins, 1839; Fisher, 1881). In the beginning of the twentieth century it was proposed by several geoscientists that these mantle convection curren ...
Why is subduction on the Earth one-sided?
... However, in global mantle convection models, where this asymmetry is not prescribed, subduction is symmetrical, or “two-sided” (Figs. 1C and 1D), where downwelling involves materials from both plates (Tackley, 2000). Recent dynamic models of subduction process, operating with realistic viscoelasticp ...
... However, in global mantle convection models, where this asymmetry is not prescribed, subduction is symmetrical, or “two-sided” (Figs. 1C and 1D), where downwelling involves materials from both plates (Tackley, 2000). Recent dynamic models of subduction process, operating with realistic viscoelasticp ...
"postorogenie" magmatism
... tures, and thus are compositionally similar to suites found in extensional regimes. We propose that thinning of the lithospheric mantle, which may be an automatic response to orogenie lithospheric thicken· ing, is responsible for these magmatic suites. Mantle lithospheric thinning moves the asthenos ...
... tures, and thus are compositionally similar to suites found in extensional regimes. We propose that thinning of the lithospheric mantle, which may be an automatic response to orogenie lithospheric thicken· ing, is responsible for these magmatic suites. Mantle lithospheric thinning moves the asthenos ...
seismic waves - Gordon State College
... • The lithosphere includes the uppermost part of the upper mantle plus the crust. • The lithosphere is cool and rigid. —It does not flow but rides atop the plastically ...
... • The lithosphere includes the uppermost part of the upper mantle plus the crust. • The lithosphere is cool and rigid. —It does not flow but rides atop the plastically ...
Plate Tectonics: A Paradigm Under Threat
... It has been said that “a hypothesis that is appealing for its unity or simplicity acts as a filter, accepting reinforcement with ease but tending to reject evidence that does not seem to fit” (Grad, 1971, p. 636). Meyerhoff and Meyerhoff (1974b, p. 411) argued that this is “an admirable description ...
... It has been said that “a hypothesis that is appealing for its unity or simplicity acts as a filter, accepting reinforcement with ease but tending to reject evidence that does not seem to fit” (Grad, 1971, p. 636). Meyerhoff and Meyerhoff (1974b, p. 411) argued that this is “an admirable description ...
ON THE SCALE OF MANTLE CONVECTION The relative motion of
... sinking lithospheric slabs do not penetrate deeper than the deepest earthquakes. While such models can produce reasonable agreement with geophysical observations this does not mean that the models are correct or that other models could not satisfy the observations equally well. The object of this pa ...
... sinking lithospheric slabs do not penetrate deeper than the deepest earthquakes. While such models can produce reasonable agreement with geophysical observations this does not mean that the models are correct or that other models could not satisfy the observations equally well. The object of this pa ...
Age of the Earth
The age of the Earth is 4.54 ± 0.05 billion years (4.54 × 109 years ± 1%). This age is based on evidence from radiometric age dating of meteorite material and is consistent with the radiometric ages of the oldest-known terrestrial and lunar samples.Following the development of radiometric age dating in the early 20th century, measurements of lead in uranium-rich minerals showed that some were in excess of a billion years old.The oldest such minerals analyzed to date—small crystals of zircon from the Jack Hills of Western Australia—are at least 4.404 billion years old. Comparing the mass and luminosity of the Sun to those of other stars, it appears that the Solar System cannot be much older than those rocks. Calcium-aluminium-rich inclusions – the oldest known solid constituents within meteorites that are formed within the Solar System – are 4.567 billion years old, giving an age for the solar system and an upper limit for the age of Earth.It is hypothesised that the accretion of Earth began soon after the formation of the calcium-aluminium-rich inclusions and the meteorites. Because the exact amount of time this accretion process took is not yet known, and the predictions from different accretion models range from a few millions up to about 100 million years, the exact age of Earth is difficult to determine. It is also difficult to determine the exact age of the oldest rocks on Earth, exposed at the surface, as they are aggregates of minerals of possibly different ages.