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The name "volcano" has its origin from the name of vulcan a god of fire in Roman mythology.
As pressure in the molten rock builds up it needs to escape somewhere. So it forces its way up fissures which are narrow cracks in the earths crust. Once the magma erupts through the earth’s surface it’s called lava.lava is liquid rock (magma) that flows out of a volcano. Fresh lava ranges from 1,300° to 2,200° F 700° to 1,200° C in temperature and glows red hot to white hot as it flows.
More then 5oo volcanoes vents have been identified in the state of california at least 76 of these vent have erupted some repeatedly mount shasta has been inhabited since at least 600 bc 9000 years of native american people
There are around 1510 'active' volcanoes in the world. We currently know of 80 or more which are under the oceans.The Earth's crust is made up of huge slabs called plates, which fit together like a jigsaw puzzle. These plates sometimes move.
Between the Earth's crust and the mantle is a substance called magma which is made of rock and gases.
When two plates collide, one section slides on top of the other, the one beneath is pushed down. magma is squeezed up between two plates.