Crustal thickness of V-shaped ridges south of the Azores: -39
... 2. Gravity data were recorded with a Bodenseewerk GSS30 gravimeter. The Eötvos and drift corrections were removed to obtain the free-air gravity anomaly (FAA). The rms crossover error for the cruise data was ~1.8 mGal. FAA data from the FARA-SIGMA cruises [Detrick et al., 1995] and the NGDC data cat ...
... 2. Gravity data were recorded with a Bodenseewerk GSS30 gravimeter. The Eötvos and drift corrections were removed to obtain the free-air gravity anomaly (FAA). The rms crossover error for the cruise data was ~1.8 mGal. FAA data from the FARA-SIGMA cruises [Detrick et al., 1995] and the NGDC data cat ...
Lithospheric layering in the North American craton
... passive seismic studies30–32 are found beneath most of these suture zones and generally indicate a subduction direction normal to the suture trends. We note that the fast-axis directions in lithospheric layer 1 and in the asthenosphere (layer 3) are comparable, similar both to surface geological tre ...
... passive seismic studies30–32 are found beneath most of these suture zones and generally indicate a subduction direction normal to the suture trends. We note that the fast-axis directions in lithospheric layer 1 and in the asthenosphere (layer 3) are comparable, similar both to surface geological tre ...
VS and density structure beneath the Colorado Plateau constrained
... [1] The Colorado Plateau is a physiographic province in the western US with an average elevation of 1.9 km where, in contrast to neighboring provinces, there is little evidence of large scale tectonic deformation or magmatism. Recent availability of Earthscope/ USArray seismic data allow us to bett ...
... [1] The Colorado Plateau is a physiographic province in the western US with an average elevation of 1.9 km where, in contrast to neighboring provinces, there is little evidence of large scale tectonic deformation or magmatism. Recent availability of Earthscope/ USArray seismic data allow us to bett ...
Thermal state of the lithosphere in the Danube Basin and its relation
... surface is also observed in the opposite direction namely on the contact zone of the Inner Carpathian units with the Transdanubian Central Range block. In both these neighbouring geological units the terrestrial heat flow densities are smaller than the value of the 50 mW/m 2 . This is evidently visib ...
... surface is also observed in the opposite direction namely on the contact zone of the Inner Carpathian units with the Transdanubian Central Range block. In both these neighbouring geological units the terrestrial heat flow densities are smaller than the value of the 50 mW/m 2 . This is evidently visib ...
Episodic Tremor and Slip
... at higher frequencies. The swarm of seismic sources results in many overlapping signals on a seismogram (Figure 2, box B), making it difficult to discern individual P and S waves typically used to estimate key details about the earthquake source. Nevertheless, detailed processing techniques have bee ...
... at higher frequencies. The swarm of seismic sources results in many overlapping signals on a seismogram (Figure 2, box B), making it difficult to discern individual P and S waves typically used to estimate key details about the earthquake source. Nevertheless, detailed processing techniques have bee ...
Geochemistry, Geophysics, Geosystems
... investigated the influence of the crustal composition on the strength and Te by constructing a set of possible end-member strength models, using ‘‘soft’’ and ‘‘hard’’ rheology for the continental crust. They found that the largest differences between the end-member models in terms of the estimated st ...
... investigated the influence of the crustal composition on the strength and Te by constructing a set of possible end-member strength models, using ‘‘soft’’ and ‘‘hard’’ rheology for the continental crust. They found that the largest differences between the end-member models in terms of the estimated st ...
Thinning of continental backarc lithosphere by flow
... the volcanic arc region, as most water is driven from the subducting plate at shallow depths. It is difficult to explain observations of thin lithosphere hundreds of kilometers behind the arc with this mechanism, unless slab-derived water can be carried far into the backarc, perhaps by transport in t ...
... the volcanic arc region, as most water is driven from the subducting plate at shallow depths. It is difficult to explain observations of thin lithosphere hundreds of kilometers behind the arc with this mechanism, unless slab-derived water can be carried far into the backarc, perhaps by transport in t ...
Mid-ocean ridges
... A map of the ocean basins (Fig. 5.1) shows that their most conspicuous topographic feature is the system of mid-oceanic ridges, the crests of which rise on average 1000- 3000 m above the adjacent ocean floor. Such ridges extend through all the major ocean basins, with a total length in excess of 60 ...
... A map of the ocean basins (Fig. 5.1) shows that their most conspicuous topographic feature is the system of mid-oceanic ridges, the crests of which rise on average 1000- 3000 m above the adjacent ocean floor. Such ridges extend through all the major ocean basins, with a total length in excess of 60 ...
Density structure and geometry of the Costa Rican subduction zone
... presents a heterogeneous crustal structure due to diverse origins and ages as well as plate-hot spot interactions which originated the Cocos Ridge, a structure that converges with the Caribbean Plate in southeastern Costa Rica. The complex structure of the oceanic plate directly influences the dynam ...
... presents a heterogeneous crustal structure due to diverse origins and ages as well as plate-hot spot interactions which originated the Cocos Ridge, a structure that converges with the Caribbean Plate in southeastern Costa Rica. The complex structure of the oceanic plate directly influences the dynam ...
Mantle flow in regions of complex tectonics: Insights from Indonesia
... perhaps most tectonically stable region in the study area today, as there is currently no active subduction around the island and, hence, little seismicity compared to the rest of Indonesia. The mid-Eocene (45 Ma ago), however, saw the onset of subduction of the Proto-South China Sea in the Sarawak ...
... perhaps most tectonically stable region in the study area today, as there is currently no active subduction around the island and, hence, little seismicity compared to the rest of Indonesia. The mid-Eocene (45 Ma ago), however, saw the onset of subduction of the Proto-South China Sea in the Sarawak ...
Imaging igneous rocks on the North Atlantic rifted continental margin
... of intrusive rocks, and thus of the temperature of the mantle from which they were formed, is seismic velocity; higher velocity rocks containing a greater MgO fraction are indicative of formation from mantle at a higher temperature (White & McKenzie 1989; Korenaga et al. 2000). High velocity materia ...
... of intrusive rocks, and thus of the temperature of the mantle from which they were formed, is seismic velocity; higher velocity rocks containing a greater MgO fraction are indicative of formation from mantle at a higher temperature (White & McKenzie 1989; Korenaga et al. 2000). High velocity materia ...
Constraints on the composition of the Aleutian arc lower crust from
... the active arc line, where colder temperatures are expected, making the stability of alpha quartz more plausible [Shen et al., 1993]. [17] The sensitivity of the expected mineral assemblages arising from different bulk compositions as a function of temperature and pressure was assessed by examining ...
... the active arc line, where colder temperatures are expected, making the stability of alpha quartz more plausible [Shen et al., 1993]. [17] The sensitivity of the expected mineral assemblages arising from different bulk compositions as a function of temperature and pressure was assessed by examining ...
Finite-frequency wave propagation through outer rise fault zones
... We modeled acoustic-wave propagation though 100, 200, and 500 m wide, serpentinized joints in a uniform, background mantle. Effective wave speeds in these models are anisotropic, with slower wave speeds in the joint-perpendicular direction and faster wave speeds parallel to joints, with wavefronts i ...
... We modeled acoustic-wave propagation though 100, 200, and 500 m wide, serpentinized joints in a uniform, background mantle. Effective wave speeds in these models are anisotropic, with slower wave speeds in the joint-perpendicular direction and faster wave speeds parallel to joints, with wavefronts i ...
Slow strain waves in blocky geological media from GPS and
... waves?” is directly linked with the detection of the main types of tectonic structures generating these waves. ...
... waves?” is directly linked with the detection of the main types of tectonic structures generating these waves. ...
Seismic wave speed structure of the Ontong
... data; the signal from earthquakes larger than Mw 5.5 are then removed from the time series. Using the one-day-long records, a cross correlation between station pairs is then calculated with one station acting as a “virtual” source. The cross correlated records are then summed into monthly stacks; th ...
... data; the signal from earthquakes larger than Mw 5.5 are then removed from the time series. Using the one-day-long records, a cross correlation between station pairs is then calculated with one station acting as a “virtual” source. The cross correlated records are then summed into monthly stacks; th ...
Introduction to Engineering Seismology Lecture 4 Dr. P
... The energy for the driving mechanisms of these drifting plates comes mainly from heat incessantly produced from the decay of radioactive elements in the rocks throughout the interior of the earth. The oceanic and continental crust makes up the top part of the plates. Each plate extends to a depth of ...
... The energy for the driving mechanisms of these drifting plates comes mainly from heat incessantly produced from the decay of radioactive elements in the rocks throughout the interior of the earth. The oceanic and continental crust makes up the top part of the plates. Each plate extends to a depth of ...
ON THE SCALE OF MANTLE CONVECTION The relative motion of
... on a number of arguments, including the belief that the ‘viscosity’ of the lower mantle is considerably greater than that of the upper mantle and that sinking lithospheric slabs do not penetrate deeper than the deepest earthquakes. While such models can produce reasonable agreement with geophysical ...
... on a number of arguments, including the belief that the ‘viscosity’ of the lower mantle is considerably greater than that of the upper mantle and that sinking lithospheric slabs do not penetrate deeper than the deepest earthquakes. While such models can produce reasonable agreement with geophysical ...
A petrologic case for Eocene slab break
... Fig. 1). Curiously, a suite of K-rich basaltic rocks also erupted in southeastern Tibet at 35–40 Ma (Chung et al., 1998; Fig. 1), i.e., coeval with early metamorphism of the Greater Himalayan Sequence, but the rocks are ordinarily only considered in tectonic models of Tibet. Four main tectonic model ...
... Fig. 1). Curiously, a suite of K-rich basaltic rocks also erupted in southeastern Tibet at 35–40 Ma (Chung et al., 1998; Fig. 1), i.e., coeval with early metamorphism of the Greater Himalayan Sequence, but the rocks are ordinarily only considered in tectonic models of Tibet. Four main tectonic model ...
Document
... tectonics, and explaining geological events and cycles that occur due to plate motion. Describing how landforms and rock layers are created, and understanding how the three types of plate boundaries cause different landforms. ...
... tectonics, and explaining geological events and cycles that occur due to plate motion. Describing how landforms and rock layers are created, and understanding how the three types of plate boundaries cause different landforms. ...
︎PDF - Fabio Crameri
... subduction and a free surface in both 3-D Cartesian and fully spherical geometry. Special focus is given to the spontaneous development of three-dimensional structures at the surface and in the upper mantle. We find that an arcuate shape is the natural form for trenches and slabs. Cartesian models a ...
... subduction and a free surface in both 3-D Cartesian and fully spherical geometry. Special focus is given to the spontaneous development of three-dimensional structures at the surface and in the upper mantle. We find that an arcuate shape is the natural form for trenches and slabs. Cartesian models a ...
GEOL 109 - Continuing Education
... a) Basalt is a volcanic rock rich in iron and magnesium. It has very fine grains (usually you can't see them without magnification) because it cools rapidly when mafic lava Page 7 of 35 ...
... a) Basalt is a volcanic rock rich in iron and magnesium. It has very fine grains (usually you can't see them without magnification) because it cools rapidly when mafic lava Page 7 of 35 ...
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.