![]() For instance, the india-Asia collision has formed the huge uplifted Tibetan Plateau, a series of mountain ranges to the north including the Tien shan and Karakoram, and deformation of the continents extends far into Asia, as far as Lake Baikal. in continent-continent collisions, deformation may be very diffuse and extend beyond the normal limit of plate boundary deformation that characterizes other types of plate interactions. In some cases, subduction brings two continental plates together and they collide, forming huge mountain belts like the Himalayan mountain chain. Often, slices of the old ocean floor are caught in these collision zones (these are called ophiolites), and the process by which they are emplaced over the continents is called obduction (opposite of subduction). suture zones are complex and include folded and faulted sequences of rocks that form on the two colliding terranes and in any intervening ocean basin. Mountain belts or orogens typically mark the places where lithospheric plates have collided, and the zone that they collided along is referred to as a suture. Since the plates are in constant motion, island arcs, continents, and other terranes often collide with each other. A simple model for the origin of the continental crust is that it represents a bunch of island arcs which formed at different times and which collided during plate collisions. Island arcs are extremely important for understanding the origin of the continental crust because the magmas and sediments produced here have the same composition as the average continental crust. These volcanoes form a volcanic arc, either on a continent or over an oceanic plate, depending on which type of crust the overlying plate is composed of. since subduction zones are long narrow zones where large plates are being subducted into the mantle, the melting produces a long line of volcanoes above the down-going plate. These melts then move upward to intrude the overlying plate, where the magma may become contaminated by melting through and incorporating minerals and elements from the overlying crust. As the oceanic slabs sink downward, they experience higher temperatures that cause the release of water and other volatiles from the subducting slab, generating melts in the mantle wedge overlying the subducting slab. There are no volcanoes at a conservative plate boundary.Oceanic lithosphere is being destroyed by sinking back into the mantle at the deep ocean trenches in a process called subduction. ![]() The earthquakes at a conservative plate boundary can be very destructive as they occur close to the Earth's surface. When the pressure is released, it sends out huge amounts of energy causing an earthquake. Pressure builds up because the plates are still trying to move. As the plates try to move, friction occurs and plates become stuck. Conservative plate boundariesĪt a conservative plate boundary, the plates slide past each other in opposite directions, or in the same direction but at different speeds. Landforms at a divergent plate boundary include ocean ridges, eg the Mid-Atlantic ridge (where the Eurasian plate and the North Atlantic plate are moving apart from each other under the Atlantic Ocean), rift valleys eg the East African Rift Valley and shield volcanoes. Rising magma can also create shield volcanoes. The movement of the plates over the mantle can cause earthquakes. When this happens the magma from the mantle rises up to make (or construct) new crust. Divergent plate boundariesĪt a divergent plate boundary - also known as a constructive plate boundary, the plates move apart from one another. Earthquakes can occur at collision boundaries. If two continental plates collide, neither can sink and so the land buckles upwards to form fold mountains. ![]() The volcanic eruptions are often violent, with lots of steam, gas and ash. Convergent boundary movement is divided into two types, subduction and collision, depending on the density of the involved plates. The magma escapes through weaknesses in the rock and rises up through a composite volcano, also known as a stratovolcano. The pressure of the magma builds up beneath the Earth's surface. When the plate sinks into the mantle it melts to form magma. This happens because the oceanic plate is denser (heavier) than the continental plate. This is known as subduction and results in the formation of an ocean trench. ![]() The plates move towards one another and this movement can cause earthquakes and volcanoes.Īs the plates collide, the oceanic plate is forced beneath the continental plate. Convergent plate boundariesĪ convergent plate boundary also known as a destructive plate boundary, usually involves an oceanic plate and a continental plate. The point at which two plates meet is called a plate boundary or margin.
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