Backarc spreading - If an island arc forms a short distance away from a continent, it may eventually move farther away from the continent by a process called backarc spreading. The Sea of Japan apparently formed by backarc spreading where it is believed that a large blob of hot mantle rose and spread to widen the backarc region. Backarc spreading may occur in a continent behind a magmatic arc.
Such spreading will thin a continental crust and create a region of high heat flow as is the case for the Basin and Range in Nevada. Divergent Plate Boundaries - these boundaries form where plates are breaking apart to move away from each other. The breakup of lithosphere starts in the continental portion of lithospheric plates, a process now taking place along the east Africa Rift Zone. Continental Rifts - When a supercontinent such as Pangaea breaks up, a diverging boundary can be found in the middle of a continent.
In the early stages of continental breakup, the center of a continent is elevated which stretches the crust, making it thinner above the uplift. Tension produces normal faults on either side of a rift valley which is a central graben.
Central Africa has a rift valley which is marked by high heat flow and basaltic volcanism. As divergence continues, the continental crust on the upper part of the lithospheric plate is infilled with basalt to form oceanic crust. New York: Elsevier, pp.
Formation and evolution of Archaean Cratons: insights from Southern Africa. In Ebinger, C. London: Geological Society, pp. Xenolith constraints on seismic velocities in the upper mantle beneath southern Africa.
G-cubed , 5 , 1—32, doi Jordan, T. Composition and structure of the continental tectosphere. Nature , , — Continents as a chemical boundary layer. MacGregor, I. Roberts Victor eclogites: ancient oceanic crust. Journal of Geophysical Research , 91 , — Morgan, P. The thermal structure and thermal evolution of the continental lithosphere.
Physics and Chemistry of the Earth , 16 , — Pollack, H. Cratonization and thermal evolution of the mantle. Earth and Planetary Science Letters , 80 , — Ritsema, J. It is continental crust which hs the greater buoyancy, so when it meets another plate of continental crust neither can subduct. Instead, they collide, crumple and fold, making them thicker and higher. An example of this is the collision between the Indo-Australian plate and the Eurasian plate, which has formed the Himalayas.
Had the Indo-Australian plate been oceanic plate, which is thinner and less buoyant, it would have been subducted. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams?
Learn more. Asked 1 year, 10 months ago. Sign In. Advanced Search. Skip Nav Destination Article Navigation. Close mobile search navigation Article navigation. Volume 7, Number 1. Previous Article Next Article. Article Navigation. Research Article January 01, Subduction of continental lithosphere: Some constraints and uncertainties Peter Molnar ; Peter Molnar. Google Scholar.
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