like earthquakes, most volcanoes are located along the 'ring of fire', a 40,000-kilometre stretch that encircles the pacific ocean.
however, there are many other regions with active volcanoes scattered around the globe.
a volcano is usually a mountain topped by a crater.
it erupts when lava and gases come out of a vent from a chamber of magma deep in the ground.
far below always under pressure. when the pressure becomes very great, it forces the magma and gasses violently out of a crack or vent, shooting them high into the air together with pieces of rock, ash and soil from around the vent and the surface.