EARTHSC 2GG3 Chapter Notes - Chapter 5: Shield Volcano, Continental Crust, Hot Spring
29 Sep 2016
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Volcanic activity or volcanism, is directly related to plate tectonics, with most volcanoes being located near plate boundaries. This relationship exists because spreading or sinking lithospheric plates at plate boundaries interact with other earth materials to produce molten rock, called magma within the earth, or lava when it erupts onto the earth"s surface. Volcanoes are constructed around an opening, called a vent through which lava and other volcanic material are extruded onto the surface. It is a misconception that the plates move around on an ocean of molten rock. This is not true with the exception of the outer core deep within earth"s interior; the planet is composed of solid rock. Most magma comes from the asthenosphere, the weak layer that underlies the lithospheric plates. The asthenosphere is weak and able to flow because it is close to its melting temperature, not because it is actually molten.
