Volcanoes

1Deep beneath the surface of the Earth, rock is so hot that it melts and becomes a thick, flowing liquid called magma. Magma collects in underground chambers, building up enormous pressure over thousands of years. When the pressure becomes too great, the magma forces its way upward through cracks in the Earth's crust. The moment it reaches the surface, it is called lava.

2A volcano is an opening in the Earth's surface through which lava, ash and gases escape. Not all volcanoes look the same. Some have gentle slopes and produce slow, flowing rivers of lava. Others have steep sides and erupt with tremendous force, sending clouds of ash and rock high into the sky. The most explosive eruptions can be heard hundreds of kilometres away.

3Volcanoes are found all over the world, but they are most common along the edges of the enormous plates that make up the Earth's crust. This zone is called the Ring of Fire and it runs around the edges of the Pacific Ocean. Countries like Japan, Indonesia, the Philippines and parts of South America sit inside this zone and experience volcanic activity regularly.

4Although volcanoes can be extremely dangerous, they are also surprisingly useful. Volcanic soil is incredibly rich in minerals, making it some of the most fertile farmland in the world. Many communities have built their homes on the slopes of volcanoes for exactly this reason, knowing that the soil will help their crops grow. Volcanoes also create new land - the islands of Hawaii, for example, were built entirely from volcanic rock rising out of the sea over millions of years.

5Scientists who study volcanoes are called volcanologists. They use special equipment to measure changes in temperature, the movement of the ground and the gases released by a volcano. By watching these signs carefully, they can sometimes predict when an eruption is coming and warn people to evacuate. Their work is difficult and often dangerous, but it saves many lives.