What are volcanoes?
A volcano is an opening in the Earth’s crust that allows magma, hot ash and gases to escape. Volcanoes can look like mountains or small hills, depending on what type they are.
Magma is molten rock - rock that is so hot it has turned into liquid. When magma reaches the surface of the Earth it is called lava and comes out of the volcano as a volcanic eruption, along with gases and ash.
Most volcanic eruptions are caused by tectonic plates moving towards each other, which usually produces violent eruptions. Other volcanoes, such as Mauna Loa in Hawaii are caused by hot spots in the Earth’s crust. These do not erupt violently and lava usually flows slowly out of them.
Eruptions from volcanoes can be very dangerous. They can produce:
- pyroclastic flows - fast moving clouds of hot ash, gas and rock
- ash clouds - small pieces of rock and glass that can be carried in the air for many kilometres
- volcanic bombs - large bits of very hot rock blown out of a volcano
Volcanoes can, however, help people living near them earn money by bringing in tourists to the area and improving the soil so that crops can be grown.