The Upper Mantle Geoid: Implications for Continental Structure and
... (degree/order up to 2159) is shown in Figure 1a. This geoid is the height of the geoid above/below the chosen reference ellipsoid, so the polar flattening and equatorial bulge (ellipticity) of the geoid doesn’t show in (Figure 1a) because this field is the difference between a (near) ellipsoidal ge ...
... (degree/order up to 2159) is shown in Figure 1a. This geoid is the height of the geoid above/below the chosen reference ellipsoid, so the polar flattening and equatorial bulge (ellipticity) of the geoid doesn’t show in (Figure 1a) because this field is the difference between a (near) ellipsoidal ge ...
Full text PDF - Geochemical Perspectives
... leading role in this narrative, Ted Ringwood, George Wetherill, George Tilton (who taught me Pb isotopic analysis during his sabbatical at Carnegie), Tom Aldrich, Carl Hedge, Shen-Su Sun, Keith O’Nions (“Sir Keith”), Gil Hanson and Mike O’Hara (who is assigned the role of villain in this narrative, ...
... leading role in this narrative, Ted Ringwood, George Wetherill, George Tilton (who taught me Pb isotopic analysis during his sabbatical at Carnegie), Tom Aldrich, Carl Hedge, Shen-Su Sun, Keith O’Nions (“Sir Keith”), Gil Hanson and Mike O’Hara (who is assigned the role of villain in this narrative, ...
Zoned mantle convection
... Geochemists observe the outcome of these processes, that is the isotopic heterogeneities, and use either empirical or statistical methods (All³egre et al. 1987; Hart et al . 1992; White 1985; Zindler & Hart 1986) to de ne the minimum number of `mantle components’ that can account for the modern iso ...
... Geochemists observe the outcome of these processes, that is the isotopic heterogeneities, and use either empirical or statistical methods (All³egre et al. 1987; Hart et al . 1992; White 1985; Zindler & Hart 1986) to de ne the minimum number of `mantle components’ that can account for the modern iso ...
Dynamical geochemistry of the mantle
... The second argument is that seismic tomography detects subducted lithosphere extending from surface subduction zones through the transition zone and deep into the lower mantle (Grand et al., 1997). The associated mass flow implies that a compositional difference would be removed within less than a b ...
... The second argument is that seismic tomography detects subducted lithosphere extending from surface subduction zones through the transition zone and deep into the lower mantle (Grand et al., 1997). The associated mass flow implies that a compositional difference would be removed within less than a b ...
Mantle mixing - Earth and Environmental Sciences
... core of the convection cell this heterogeneity is barely deformed at all. The dramatic difference in mixing efficiency between two different heterogeneities with slightly different initial condition is maintained over long computational time in this convection model, as is illustrated in Figure 2. T ...
... core of the convection cell this heterogeneity is barely deformed at all. The dramatic difference in mixing efficiency between two different heterogeneities with slightly different initial condition is maintained over long computational time in this convection model, as is illustrated in Figure 2. T ...
Radiogenic Isotope Geochemistry of the Mantle
... A principal objective of geology is to understand how the Earth evolved from its initial state to its present one. Radiogenic isotope geochemistry is uniquely suited for this sort of study because an isotope ratio such as 87Sr/86Sr is a function not only of the differentiation processes which fracti ...
... A principal objective of geology is to understand how the Earth evolved from its initial state to its present one. Radiogenic isotope geochemistry is uniquely suited for this sort of study because an isotope ratio such as 87Sr/86Sr is a function not only of the differentiation processes which fracti ...
Intracratonic asthenosphere upwelling and lithosphere rejuvenation
... negative fractionation (TbN/YbN 0.1–0.4). LREE patterns are often upward concave with LaN/NdN varying from 0.6 to 3 and generally mimic, at lower level, those of the coexisting clinopyroxene. In H58D, the REE patterns of clinopyroxene are variable from nearly flat to LREE enriched. The lowest LREE p ...
... negative fractionation (TbN/YbN 0.1–0.4). LREE patterns are often upward concave with LaN/NdN varying from 0.6 to 3 and generally mimic, at lower level, those of the coexisting clinopyroxene. In H58D, the REE patterns of clinopyroxene are variable from nearly flat to LREE enriched. The lowest LREE p ...
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 ...
FREE Sample Here
... A) a massive nickle iron asteroid that was the nucleus upon which Earth condensed B) the left over nickle and iron that would not fit into the earlier formed crust and mantle C) molten iron and nickle that separated from silicates and sank due to its higher density D) high density radioactive carbon ...
... A) a massive nickle iron asteroid that was the nucleus upon which Earth condensed B) the left over nickle and iron that would not fit into the earlier formed crust and mantle C) molten iron and nickle that separated from silicates and sank due to its higher density D) high density radioactive carbon ...
Why subduction zones are curved - Harvard John A. Paulson School
... (such as a ping‐pong ball) implies a direct relationship between slab dip and the radius of the subduction arc: the greater the radius of curvature of the arc, the steeper the dip of the downgoing slab. Although this analogy is commonly invoked as the explanation for subduction zone curvature [e.g., ...
... (such as a ping‐pong ball) implies a direct relationship between slab dip and the radius of the subduction arc: the greater the radius of curvature of the arc, the steeper the dip of the downgoing slab. Although this analogy is commonly invoked as the explanation for subduction zone curvature [e.g., ...
Fluvial erosion
... Progenitor star maybe several solar masses Provide shorter-lived radionuclides in local dust clouds ...
... Progenitor star maybe several solar masses Provide shorter-lived radionuclides in local dust clouds ...
Upper mantle flow in the western Mediterranean
... The Apennines–Maghrebides subduction zone was characterized, since the beginning, by fast radial eastward rollback, as evidenced by the migration of the subduction related calkalcaline volcanism and of the compressional front which induced widespread extensional tectonics accompanied by alkaline vol ...
... The Apennines–Maghrebides subduction zone was characterized, since the beginning, by fast radial eastward rollback, as evidenced by the migration of the subduction related calkalcaline volcanism and of the compressional front which induced widespread extensional tectonics accompanied by alkaline vol ...
Thermal evolution of the Earth as recorded by komatiites
... magmas (boninites), as well as the compositional overlap of boninites with basaltic komatiites interlayered with the komatiites (Fig. 1). The plume advocates dismiss the high-SiO2 compositions as formed by either fractionation or crustal contamination of komatiite magmas, while subduction advocates ...
... magmas (boninites), as well as the compositional overlap of boninites with basaltic komatiites interlayered with the komatiites (Fig. 1). The plume advocates dismiss the high-SiO2 compositions as formed by either fractionation or crustal contamination of komatiite magmas, while subduction advocates ...
Subduction zones: observations and
... The lithosphere of the Earth is the cold, top thermal boundary layer of the mantle. The conceptual picture of a plate as a passive raft that sits on top of the mantle neglects the fact that oceanic plates are created from and return to the mantle. It is generally accepted that the cold, negatively-b ...
... The lithosphere of the Earth is the cold, top thermal boundary layer of the mantle. The conceptual picture of a plate as a passive raft that sits on top of the mantle neglects the fact that oceanic plates are created from and return to the mantle. It is generally accepted that the cold, negatively-b ...
The heavy noble gas composition of the depleted MORB mantle
... To characterize the heavy noble gas composition of MORBs we present new He, Ne, Ar, and Xe abundances and isotopic compositions from the equatorial Mid-Atlantic Ridge. Both depleted MORBs nominally devoid of plume influence and more enriched MORBs thought to represent the influence of a HIMU mantle pl ...
... To characterize the heavy noble gas composition of MORBs we present new He, Ne, Ar, and Xe abundances and isotopic compositions from the equatorial Mid-Atlantic Ridge. Both depleted MORBs nominally devoid of plume influence and more enriched MORBs thought to represent the influence of a HIMU mantle pl ...
Tectonic fabric of the subcontinental lithosphere
... Fig. 1. Map showing location of investigations reported in this special volume. Short bars show fast-axis orientations from published SKS splitting analyses, a widely used technique to characterize seismic anisotropy of the upper mantle. Splitting parameters were obtained from a comprehensive list o ...
... Fig. 1. Map showing location of investigations reported in this special volume. Short bars show fast-axis orientations from published SKS splitting analyses, a widely used technique to characterize seismic anisotropy of the upper mantle. Splitting parameters were obtained from a comprehensive list o ...
Full-text PDF (final published version)
... recycled components in the mantle but should be highly sensitive to their prior presence at the surface, where redox-dependent isotope fractionation should be greatest. Along these lines, Mo isotope variations in magmatic rocks have attracted considerable interest to study the origin of enriched man ...
... recycled components in the mantle but should be highly sensitive to their prior presence at the surface, where redox-dependent isotope fractionation should be greatest. Along these lines, Mo isotope variations in magmatic rocks have attracted considerable interest to study the origin of enriched man ...
sample test
... c. Earth is slowly cooling and shrinking. d. the continents were once joined together in a single landmass. What is Pangaea? a. the name of a German scientist b. the name of the supercontinent that existed millions of years ago c. another name for continental drift d. the name of an ancient fossil W ...
... c. Earth is slowly cooling and shrinking. d. the continents were once joined together in a single landmass. What is Pangaea? a. the name of a German scientist b. the name of the supercontinent that existed millions of years ago c. another name for continental drift d. the name of an ancient fossil W ...
Continent-sized anomalous zones with low
... as well as convergence and consumption of older plates into Earth’s interior at subduction zones, is related to convective motions of the underlying mantle rock over geologic timescales. The mantle, which extends to about 2,900 km depth, just less than halfway to Earth’s centre (near 6,400 km), act ...
... as well as convergence and consumption of older plates into Earth’s interior at subduction zones, is related to convective motions of the underlying mantle rock over geologic timescales. The mantle, which extends to about 2,900 km depth, just less than halfway to Earth’s centre (near 6,400 km), act ...
Impact origin for the greater Ontong Java Plateau?
... ridges, and seamount chains attributed to mantle plumes, and sampled by drilling, have experienced signi¢cant subaerial volcanism during construction (e.g., [37,38]). Yet all OJP basalts, either drilled or sampled from obducted Solomon Islands sections, erupted below sea level, and sediments deposit ...
... ridges, and seamount chains attributed to mantle plumes, and sampled by drilling, have experienced signi¢cant subaerial volcanism during construction (e.g., [37,38]). Yet all OJP basalts, either drilled or sampled from obducted Solomon Islands sections, erupted below sea level, and sediments deposit ...
Large-Scale Thermo-chemical Structure of the Deep Mantle
... no notable large-scale structure is observed, and the RMS seismic velocity variation is small, 0.5 % or less. Below the surface, anomalies of shear-wave velocity are well correlated with surface tectonics down to depths of about 200–300 km (Schaeffer and Lebedev, this volume). The ocean–continent di ...
... no notable large-scale structure is observed, and the RMS seismic velocity variation is small, 0.5 % or less. Below the surface, anomalies of shear-wave velocity are well correlated with surface tectonics down to depths of about 200–300 km (Schaeffer and Lebedev, this volume). The ocean–continent di ...
PDF (Chapter 12. The Shape of the Earth, Heat Flow and Convection)
... midocean ridges. The geoid reflects temperature and density variations in the interior, but these are not simply related to the surface expressions of plate tectonics. The largest departures of the geoid from a radially symmetric rotating spheroid are the equatorial and antipodal geoid highs centere ...
... midocean ridges. The geoid reflects temperature and density variations in the interior, but these are not simply related to the surface expressions of plate tectonics. The largest departures of the geoid from a radially symmetric rotating spheroid are the equatorial and antipodal geoid highs centere ...
Lithosphere and Asthenosphere
... The definition of the lithosphere is based on how Earth materials behave, so it includes the crust and the uppermost mantle, which are both brittle. Since it is rigid and brittle, when stresses act on the lithosphere, it breaks. This is what we experience as an earthquake. Although we sometimes refe ...
... The definition of the lithosphere is based on how Earth materials behave, so it includes the crust and the uppermost mantle, which are both brittle. Since it is rigid and brittle, when stresses act on the lithosphere, it breaks. This is what we experience as an earthquake. Although we sometimes refe ...
Mantle plumes and dynamics of the Earth interior — towards a new
... plumes as the assumption of the convection process in the Earth’s mantle, mantle convection versus data on both its viscosity and the existence of global seismic discontinuities, possibility of horizontal displacements of lithospheric plates above the discontinuous LVZ zone which disappears under de ...
... plumes as the assumption of the convection process in the Earth’s mantle, mantle convection versus data on both its viscosity and the existence of global seismic discontinuities, possibility of horizontal displacements of lithospheric plates above the discontinuous LVZ zone which disappears under de ...
The thermochemical structure and evolution of Earth`s mantle
... of values around eight times the atmospheric ratio, OIBs display a much wider scatter, with some (e.g. Loihi) having values up to 30 times the atmospheric ratio. This reservoir has generally been assumed to be primordial and outgassed, because ...
... of values around eight times the atmospheric ratio, OIBs display a much wider scatter, with some (e.g. Loihi) having values up to 30 times the atmospheric ratio. This reservoir has generally been assumed to be primordial and outgassed, because ...
Spherical Earth
The concept of a spherical Earth dates back to around the 6th century BC, when it was mentioned in ancient Greek philosophy, but remained a matter of philosophical speculation until the 3rd century BC, when Hellenistic astronomy established the spherical shape of the earth as a physical given. The paradigm was gradually adopted throughout the Old World during Late Antiquity and the Middle Ages. A practical demonstration of Earth's sphericity was achieved by Ferdinand Magellan and Juan Sebastián Elcano's expedition's circumnavigation (1519−1522).The concept of a spherical Earth displaced earlier beliefs in a flat Earth: In early Mesopotamian mythology, the world was portrayed as a flat disk floating in the ocean and surrounded by a spherical sky, and this forms the premise for early world maps like those of Anaximander and Hecataeus of Miletus. Other speculations on the shape of Earth include a seven-layered ziggurat or cosmic mountain, alluded to in the Avesta and ancient Persian writings (see seven climes).The realization that the figure of the Earth is more accurately described as an ellipsoid dates to the 18th century (Maupertuis).In the early 19th century, the flattening of the earth ellipsoid was determined to be of the order of 1/300 (Delambre, Everest). The modern value as determined by the US DoD World Geodetic System since the 1960s is close to 1/298.25.