A mountain that opens under the Earth's surface into a pool of molten rock, also known as magma, is called a volcano. When pressure builds from the magma, a volcano erupts, spilling the molten rock onto the Earth's surface.
Volcanoes are like huge safety valves that help release built up pressure from inside the Earth. When a volcano releases magma from inside the Earth, called an eruption, the magma then becomes known as lava, which is very hot, measuring between 1,148 and 1,204 degrees C.
Causes of Eruptions
Inside the Earth, there are huge slabs of rock called plates that fit together like a puzzle to form the Earth's surface. Sometimes, the plates move, allowing magma inside the earth to force its way up to the Earth's surface and erupt through a volcano.
Amount of Volcanoes
In 2010, scientists estimate that there are around 1,500 active volcanoes throughout the world. An active volcano is one that is erupting or has erupted since scientists have recorded them. There are also at least 80 volcanoes throughout the world that are underwater.