1 Lecture 24: Convergent boundaries November 22, 2006
... Convergent boundaries are characterized by consumption of oceaninc crust in subduction zones, with attendant arc volcanism, metamorphism and uplift. During their early phases, convergent boundaries are initiated by the rupture and sinking of oceanic crust , probably related to a change in plate moti ...
... Convergent boundaries are characterized by consumption of oceaninc crust in subduction zones, with attendant arc volcanism, metamorphism and uplift. During their early phases, convergent boundaries are initiated by the rupture and sinking of oceanic crust , probably related to a change in plate moti ...
No Slide Title
... • Oceanic plate • Trench • Fore-arc ridge (melange) • Fore-arc basin • Continental plate with volcanic mountain range (e.g. Andes) ...
... • Oceanic plate • Trench • Fore-arc ridge (melange) • Fore-arc basin • Continental plate with volcanic mountain range (e.g. Andes) ...
SubFac abstract from Robert J. Stern
... strongly extensional convergent plate boundary, particularly in the southern IBM where these effects are maximized. Off-ridge volcanism was common during mid- and Late Cretaceous time on the Pacific Plate now outboard of southern IBM. As a result, there are significant differences in the bulk compos ...
... strongly extensional convergent plate boundary, particularly in the southern IBM where these effects are maximized. Off-ridge volcanism was common during mid- and Late Cretaceous time on the Pacific Plate now outboard of southern IBM. As a result, there are significant differences in the bulk compos ...
Partial melting
... Seafloor spreading leads to the formation of new crust that, compared to continental crust, is relatively enriched in iron and magnesium and depleted in silica (SiO2) (because it reflects the chemistry of the mantle). As two plates continue to move apart, the rock in the seafloor grows older as its ...
... Seafloor spreading leads to the formation of new crust that, compared to continental crust, is relatively enriched in iron and magnesium and depleted in silica (SiO2) (because it reflects the chemistry of the mantle). As two plates continue to move apart, the rock in the seafloor grows older as its ...
PowerPoint Presentation - How and why does subduction occur?
... How and why does subduction occur? Convergence One plate sinks beneath the other Dense oceanic crust sinks into mantle ...
... How and why does subduction occur? Convergence One plate sinks beneath the other Dense oceanic crust sinks into mantle ...
Izu-Bonin-Mariana Arc
The Izu-Bonin-Mariana (IBM) arc system is an outstanding example of a plate tectonic convergent boundary. IBM extends over 2800 km south from Tokyo, Japan, to beyond Guam, and includes the Izu Islands, Bonin Islands, and Mariana Islands; much more of the IBM arc system is submerged below sealevel. The IBM arc system lies along the eastern margin of the Philippine Sea Plate in the Western Pacific Ocean. It is most famous for being the site of the deepest gash in Earth's solid surface, the Challenger Deep in the Mariana Trench. The IBM arc system formed as a result of subduction of the western Pacific plate. The IBM arc system now subducts mid-Jurassic to Early Cretaceous lithosphere, with younger lithosphere in the north and older lithosphere in the south, including the oldest (~170 million years old, or Ma) oceanic crust. Subduction rates vary from ~2 cm (1 inch) per year in the south to 6 cm (~2.5 inches) in the north. The volcanic islands that comprise these island arcs are thought to have been formed from the release of volatiles (steam from trapped water, and other gases) being released from the subducted plate, as it reached sufficient depth for the temperature to cause release of these materials. The associated trenches are formed as the oldest (most western) part of the Pacific plate crust increases in density with age, and because of this process finally reaches its lowest point just as it subducts under the crust to the west of it.The IBM arc system is an excellent example of an intra-oceanic convergent margin (IOCM). IOCMs are built on oceanic crust and contrast fundamentally with island arc built on continental crust, such as Japan or the Andes. Because IOCM crust is thinner, denser, and more refractory than that beneath Andean-type margins, study of IOCM melts and fluids allows more confident assessment of mantle-to-crust fluxes and processes than is possible for Andean-type convergent margins. Because IOCMs are far removed from continents they are not affected by the large volume of alluvial and glacial sediments. The consequent thin sedimentary cover makes it much easier to study arc infrastructure and determine the mass and composition of subducted sediments. Active hydrothermal systems found on the submarine parts of IOCMs give us a chance to study how many of earth's important ore deposits formed.