Volcano Terminology and Types

Defining Volcano Terminology

• A volcano is an opening in the Earth's surface where molten rock, smoke, gases, and ash are ejected.
• Mayon Volcano in the Philippines is an active volcano and notable for its perfect cone shape.
• A crater is a funnel-shaped depression at the top of a volcano formed by an explosive eruption.
• A caldera is a large volcanic crater formed when the magma chamber beneath a volcano empties and the surrounding rock collapses.
• Magma is hot, fluid, or semi-fluid material beneath or within the Earth's crust, typically made of molten rock.
• Lava is the molten rock that is ejected from a volcano.

Types of Volcanoes Based on Shape

• Shield volcanoes are broad, slightly domed structures formed by the accumulation of fluid lava flows. They resemble a warrior's shield, hence the name.
  • Example: Mauna Loa in Hawaii
• Cinder cone volcanoes are built from ejected lava fragments. They have steep slopes, wide craters, and are the most common type of volcano. Also known as scoria cones.
  • Example: Mount Parícutin in Mexico
• Composite volcanoes are tall, nearly perfect cone-shaped structures formed by alternating layers of lava and pyroclastic deposits (rock fragments ejected from a volcano). They are also known as stratovolcanoes.
  • Example: Mayon Volcano in the Philippines

Types of Volcanic Eruptions

• Phreatic eruptions are steam-driven explosions caused by the contact of hot rocks with water.
  • Example: Taal Volcano eruption in January 2020.
• Phreatomagmatic eruptions are violent eruptions caused by the interaction of water and magma.
• Strombolian eruptions are characterized by periodic, weak to violent eruptions with fountaining lava.
• Vulcanian eruptions are characterized by tall, explosive eruptions reaching up to 20 kilometers high, with pyroclastic flows and ash.
• Plinian eruptions are the most explosive type of eruption, with large amounts of gas and pyroclastic materials.
  • Example: Mount Pinatubo eruption in 1991.

Volcano Activity Classification

• Active Volcanoes have a record of eruption.
• Inactive Volcanoes show no activity and have no record of eruption.
  • Example: Mount Kanlaon in Negros Occidental, Philippines.

Importance of Volcanoes

• Volcanoes have a significant role in sustaining life on Earth.
• They release heat and gases that contribute to the Earth's atmosphere and help regulate climate.
• Volcanic activity also creates fertile soil, contributing to agriculture.