Some lithospheric plates consist of both continental and oceanic lithosphere. Both dehydration and partial melting occurs along the 1,000 ☌ (1,830 ☏) isotherm, generally at depths of 65 to 130 km (40 to 81 mi). This releases water into the hotter asthenosphere, which leads to partial melting of asthenosphere and volcanism. As the relatively cool subducting slab sinks deeper into the mantle, it is heated, causing hydrous minerals to break down. The force of gravity helps drive the subducting slab into the mantle.
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Subduction begins when this dense crust converges with less dense crust. As this new crust is pushed away from the spreading center by the formation of newer crust, it cools, thins, and becomes denser. These convection cells bring hot mantle material to the surface along spreading centers creating new crust.
![continental continental convergent boundary continental continental convergent boundary](http://rereber-earthquakes.weebly.com/uploads/1/5/1/6/15166996/3027509.gif)
Convection cells are the result of heat generated by the radioactive decay of elements in the mantle escaping to the surface and the return of cool materials from the surface to the mantle. Plate tectonics is driven by convection cells in the mantle.
![continental continental convergent boundary continental continental convergent boundary](https://i.ytimg.com/vi/F9uGSuyMclc/maxresdefault.jpg)
The geologic features related to convergent boundaries vary depending on crust types. Convergent boundaries occur between oceanic-oceanic lithosphere, oceanic-continental lithosphere, and continental-continental lithosphere. These collisions happen on scales of millions to tens of millions of years and can lead to volcanism, earthquakes, orogenesis, destruction of lithosphere, and deformation. The subduction zone can be defined by a plane where many earthquakes occur, called the Wadati–Benioff zone. One plate eventually slides beneath the other, a process known as subduction. The goals of these studies include identification of mineral resources, natural hazard mitigation, assessment of long-term fault behaviour and interpretation and visualisation of prior tectonic events.Simplified diagram of a convergent boundaryĪ convergent boundary (also known as a destructive boundary) is an area on Earth where two or more lithospheric plates collide. These studies consider processes ranging from deformation at microscopic scales to the forces controlling convergence over 1000’s of km. In Norway past episodes (400-500 million years before present) of both subduction and continental convergence are responsible for the formation of the Norwegian Caledonian Mountains.Īt NGU, processes at convergent plate boundaries are examined through field studies of ancient plate boundaries within Norway and computer simulations of subduction and continental convergence. During convergence between two continental plates of similar density (continental collision), neither plate is able to sink and large mountain ranges form as the tectonic plates thicken to accommodate convergence.Īt short time scales ( 100 million years), the cumulative effect of these processes may produce large topographic features such as the modern Himalayan mountain range and Andes volcanic mountain chain.
![continental continental convergent boundary continental continental convergent boundary](https://www.nps.gov/subjects/geology/images/convergent-plate-boundary_Accretion-10x.jpg)
This process, known as subduction, is responsible for abundant volcanic activity and the strongest recorded earthquakes on Earth. During convergence between an oceanic and continental plate, the denser oceanic plate sinks beneath the more buoyant continental plate.