A volcano is a mountain with a hole where lava (hot, liquid rock) comes from a magma chamber under the ground. Most volcanoes have a volcanic crater at the top. When a volcano is active, materials come out of it. The materials include lava, steam, gaseous sulphur compounds, ash and broken rock pieces.
When there is enough pressure, the volcano erupts. Some volcanic eruptions blow off the top of the volcano. The magma comes out, sometimes quickly and sometimes slowly. Some eruptions come out at a side instead of the top.
Volcanologists are scientists who study volcanoes using methods from geology, chemistry, geography, mineralogy, physics and sociology.
A traditional way to classify or identify volcanoes is by its pattern of eruptions. Those volcanoes which may erupt again at any time are called active. Those that are now quiet called dormant (inactive). Those volcanos which have not erupted in historical times are called extinct.
An active volcano is currently erupting, or it has erupted in the last 10,000 years. An example of an active volcano is Mount St. Helens in the United States (US).
A dormant volcano is “sleeping,” but it could awaken in the future. Mount Rainier in the United States is considered dormant.
An extinct volcano has not erupted in the past 10,000 years. Edinburgh Castle in Scotland is located on top of an extinct volcano.
Mount Etna is a volcano on the east coast of Sicily, part of southern Italy. It is the largest active volcano in Europe. Mount Etna erupts every few years. Etna’s most destructive eruption started on 11 March 1669. It produced lava flows that destroyed ten villages and reached the town of Catania five weeks later, on 15 April. Many buildings were destroyed, but it killed few people.