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.

• There are about 1500 active volcanoes in the world that have erupted in the past 10,000 years.
• The biggest volcano in the world is Mauna Loa in Hawaii.
• More than 80% of the Earth’s surface is volcanic in origin.
• The rock debris carried by the blast of Mount St. Helen’s eruption traveled as fast as 250 miles per hour!
• More than half of the world’s active volcanoes above sea level encircle the Pacific Ocean to form the “Ring of Fire”
• Jupiter’s Moon Io is the most volcanic place in the solar system.

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.