Volcanoes: Types and Definitions

Volcano Definition

• Volcanoes are natural openings on Earth's surface where molten rocks, smoke, gases, and ashes are ejected.
• Mayon Volcano in Albay, Philippines is a popular example of a perfect cone volcano.

Volcano Parts

• Volcanoes have three parts:
  • Base
  • Slope
  • Summit, where the crater is located.
• Crater is a funnel-shaped depression formed by explosive eruptions.
• Caldera is formed when a part of the crater wall collapses after an explosive eruption, often triggered by emptying of the magma chamber beneath the volcano.
• Magma is molten rock beneath the Earth's crust.
• Lava is magma that has been ejected from a volcano.

Volcano Classifications

• Volcanoes can be classified by shape and eruption type.

Volcano Types by Shape

• Shield Volcano: Formed by accumulation of lava flows, broad with a slightly domed structure resembling a warrior's shield.
  • Example: Mauna Loa in Hawaii
• Cinder Cone Volcano: Built from ejected lava fragments, steep slopes, wide crater, most abundant type.
  • Example: Mount Paricutin in Mexico
• Composite Volcano (Stratovolcano): Large, nearly perfect slope structure formed by alternating solidification of lava and pyroclastic deposits.
  • Example: Mayon Volcano in the Philippines

Volcano Types by Eruption

• Phreatic: Steam-driven eruption caused by hot rocks contacting water, also known as hydrothermal eruption.
  • Example: Taal Volcano eruption in January 2020
• Phreatomagmatic: Violent eruption caused by interaction between water and magma, resulting in a fine ash eruption.
• Strombolian: Periodic weak to violent eruptions characterized by fountain lava.
• Vulcanian: Tall eruptions reaching up to 20 kilometers high, with pyroclastic flow and ash tephra.
• Plinian: Extremely explosive eruption of gas and pyroclastic material, intensely violent.
  • Example: Mount Pinatubo eruption in 1991

Volcano Activity Levels

• Active Volcano: Has a record of eruption.
• Inactive Volcano: Shows no activity and no record of eruption.
  • Example: Mount Kanlaon in Negros Occidental, Philippines

Volcano Significance

• Volcanoes contribute to life on Earth by keeping the Earth warm and providing water, essential for sustaining life.