How are volcanoes created |
Answer:
Volcanoes are formed usually near plate boundaries, most commonly divergent/constructive plate boundaries, such as the Mid-Atlantic Ridge. Here the crust is moving apart and causing melting due to a decrease in pressure. The magma rises, filling the cracks in the crust and forms fissure volcanoes and sea mounts, which are submarine volcanoes.
Volcanoes also form at convergent/destructive boundaries, like the the rim of the Pacific ocean known as the Ring of Fire, which contains about 68% of Earth's subaerial volcanoes. A volcano here is formed when a denser, colder oceanic plate, subducts under another plate, either a continental or warmer oceanic plate. The subducted plate will melt under the high temperatures in the mantle. This will form magma, which will in turn form cracks in the plates, which allows the magma to flow out from the mantle into the crust and sometime onto Earth's surface. The lava (when magma reaches the surface it is called lava) will then harden and form layers, slowly forming a volcano.
A shield volcano is formed when there is mafic lava, which has a low silica content, making it less viscous and in turn means it flows quickly over a large area before it cools and hardens; whereas a felsic-lava or composite volcano is formed when there is felsic lava, with a high silica content which in turn increases it's viscosity which means it flows slowly over a small area before it hardens.
Another reason for the formation of volcanoes is the mantle plume theory. A mantle plume is situated beneath the plate, which means it does not move as the plate moves. It is magma source, and magma spews out of it onto Earth's surface to form volcanoes. However, the volcano is situated above the plate, so the volcano moves along with the plate. Since the mantle plume does not move, the volcano becomes extinct as it is cut off from its magma source. A new volcano then forms on top of the hot spot and the cycle continues. Some examples are the Hawaii chain islands and Yellowstone.
Volcanoes are mainly formed along the edge of plates, and most often occur at mid ocean ridges.
Volcanoes also form at convergent/destructive boundaries, like the the rim of the Pacific ocean known as the Ring of Fire, which contains about 68% of Earth's subaerial volcanoes. A volcano here is formed when a denser, colder oceanic plate, subducts under another plate, either a continental or warmer oceanic plate. The subducted plate will melt under the high temperatures in the mantle. This will form magma, which will in turn form cracks in the plates, which allows the magma to flow out from the mantle into the crust and sometime onto Earth's surface. The lava (when magma reaches the surface it is called lava) will then harden and form layers, slowly forming a volcano.
A shield volcano is formed when there is mafic lava, which has a low silica content, making it less viscous and in turn means it flows quickly over a large area before it cools and hardens; whereas a felsic-lava or composite volcano is formed when there is felsic lava, with a high silica content which in turn increases it's viscosity which means it flows slowly over a small area before it hardens.
Another reason for the formation of volcanoes is the mantle plume theory. A mantle plume is situated beneath the plate, which means it does not move as the plate moves. It is magma source, and magma spews out of it onto Earth's surface to form volcanoes. However, the volcano is situated above the plate, so the volcano moves along with the plate. Since the mantle plume does not move, the volcano becomes extinct as it is cut off from its magma source. A new volcano then forms on top of the hot spot and the cycle continues. Some examples are the Hawaii chain islands and Yellowstone.
Volcanoes are mainly formed along the edge of plates, and most often occur at mid ocean ridges.