What causes volcanoes eruptions??

Many volcanoes occur in subduction zones. These are areas where oceanic crust is being subducted under continental crust. As the crust is thrust under the continent, it melts through friction and proximity to the mantle, resulting in large pockets of magma. This magma then erupts under pressure in the form of lava, ash, steam, and super-heated mud.

As magma rises toward the surface, gas bubbles form int he magma. As the magma rises higher and higher, the bubbles get bigger and bigger. When the magma reaches the surface, the bubbles expand very fast . . . and an explosive eruption happens.

the earth plates are moving under ground by an earthquake somewhere in the world