Volcanoes

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 800^o C.

Classification

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.