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. This means instead of having abundant lava flows that release the pressure inside the volcano the slow moving lava builds up in the vents, forms domes, and then usually violently erupts due to pressure build up.Oceanic lithosphere is being destroyed by sinking back into the mantle at the deep ocean trenches in a process called subduction. Magma in these kinds of volcanoes are very viscous so the magma does not flow easily. These types of volcanoes are very dangerous due to the viscosity of their magma. Due to this type of interaction it is possible for there to be an abundance of magma which will search for weak points in the crust through which to pass. There is partial melting that occurs as the subducting plate passes into the upper mantle releasing water and lowering the rock melting point. These volcanoes are common at this boundary because of the way subduction forces the mantle to act. This volcano erupted laterally which is common for these types of volcanoes and expelled a cloud of ash that blanketed the northwest United States of America. One such eruption that devastated numerous towns was of Mount St. These cones are highly dangerous if they were to erupt because of their expulsion of pyroclastic rock and especially the clouds of ash and gasses. ![]() The volcanoes that we observe along this convergent boundary are composite volcanoes that have been highly active for many years. These volcanoes are large cones made up of layers of erupted material and lava flows. Composite volcanoes or stratovolcanoes are large highly dangerous volcanoes that make up much of the Ring of Fire. ![]() They are characterized by lava flows that mainly occur before the volcano goes dormant. For this reason, they are very common and often lead to the creation of volcanic islands.Cinder cone volcanoes are more likely composed of small cinders of ejected lava fragments that have hardened into a cone around what was most likely a single erupting event. Shield volcanoes are formed by large basaltic lava flows and are usually large and originate as seamounts. Th ere are three types of volcanoes that have been classified in geology and each has its own distinct characteristics.
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