A volcano is a mountain that has lava come from a magma chamber under the ground.
Types of Volcanoes:
  1. Shield Volcano: Formed by fluid low-silica mafic lava. (E.g. Mauna Kea in Hawaii).
  2. Composite Volcano: AKA Strato Volcanoes. Unlike shield volcanoes, these have a steep profile and periodic eruptions. (E.g. Mount Fuji in Japan and Vesuvius).
  3. Caldera Volcano: A caldera is a basin-like feature formed by collapse of land after a volcanic eruption. It is most dangerous category of volcanoes. They have coolest lava with temperature ranging from 650 to 800o C.
Based on pattern of eruption:
  1. Active: Currently erupting or it has erupted in the last 10,000 years. (E.g. Mount St. Helens in US).
  2. Dormant: Sleeping but could awaken in the future. (E.g. Mount Rainier in US).
  3. Extinct: Has not erupted in the past 10,000 years. (E.g. Edinburgh Castle in Scotland).
# Key Points
  • Volcanoes are formed by the movement of tectonic plates.
  • Most volcanoes have a volcanic crater at the top. When a volcano is active, materials (lava, steam, gaseous sulfur compounds, ash and broken rock pieces) come out of it.
  • When there is enough pressure, the volcano erupts.
  • Volcanoes are found on planets other than Earth (E.g. Olympus Mons on Mars).
  • The world's biggest volcano is named Mauna Loa in Hawaii.