What is a volcano?
A volcano is a conical hill or mountain formed by material from the mantle being forced through an opening or vent in the Earth's crust. Volcanoes are found in three states: extinct, dormant and active. An extinct volcano will never erupt again. A dormant volcano has not erupted in 2000 years. An active volcano has erupted recently and is likely to erupt again.There are three main types of volcano - composite or strato, shield and dome.Composite volcanoes, sometimes known as strato volcanoes, are steep sided cones formed from layers of ash and lava flows. The eruptions from these volcanoes may be a pyroclastic flow rather than a flow of lava. A pyroclastic flow is a superheated mixture of hot steam, ash, rock and dust. A pyroclastic flow can travel down the side of a volcano at very high speeds with temperatures over 400 degrees celsius. Composite volcanoes can rise over 8000 feet.