Composite volcano

Definition

A composite volcano, also known as a stratovolcano, is a tall, conical volcanic structure characterized by a combination of explosive eruptions and lava flows. These volcanoes typically form from alternating layers of ash, tephra, and solidified lava, making them steep-sided and visually striking. Their eruptions can be quite violent due to the high viscosity of their magma, which can trap gas and pressure until it is released.

5 Must Know Facts For Your Next Test

1. Composite volcanoes are known for their explosive eruptions, which can result in pyroclastic flows that are extremely dangerous.
2. They typically have a symmetrical shape with steep sides due to the accumulation of lava flows and tephra over time.
3. Famous examples of composite volcanoes include Mount St. Helens in the United States and Mount Fuji in Japan.
4. The eruptions of composite volcanoes can affect climate patterns by releasing large amounts of ash and sulfur dioxide into the atmosphere.
5. Composite volcanoes often have a central vent or crater where eruptions occur, along with possible secondary vents on their flanks.

Review Questions

• How do the eruptive styles of composite volcanoes differ from those of shield volcanoes?
  • Composite volcanoes are characterized by explosive eruptions due to their viscous magma, which traps gases until pressure builds up. In contrast, shield volcanoes have low-viscosity magma that allows gases to escape easily, resulting in more gentle lava flows. This difference leads to the steep profile of composite volcanoes versus the broad, gently sloping shape of shield volcanoes.
• Discuss the role of magma composition in determining the eruptive behavior of composite volcanoes.
  • The composition of magma in composite volcanoes is primarily andesitic to rhyolitic, which contains higher levels of silica. This high silica content increases the viscosity of the magma, leading to more explosive eruptions as gas bubbles become trapped. The pressure buildup from these trapped gases can result in violent explosions, producing pyroclastic flows and ash clouds that pose significant hazards to nearby areas.
• Evaluate the potential hazards associated with living near composite volcanoes and propose measures for risk mitigation.
  • Living near composite volcanoes poses several hazards, including explosive eruptions, pyroclastic flows, and ashfall, which can damage property and harm human health. To mitigate these risks, it is crucial to establish comprehensive monitoring systems to detect signs of volcanic activity. Communities should also develop emergency response plans that include evacuation routes and education on the dangers associated with volcanic eruptions. Long-term planning must consider land use restrictions in high-risk areas to reduce potential impacts on populations.

Related terms

Magma: Magma is molten rock found beneath the Earth's surface that can rise to form volcanic eruptions.

Tephra:

Tephra refers to any volcanic rock material ejected into the air during an explosive eruption, including ash, pumice, and volcanic bombs.

Caldera:

A caldera is a large depression formed when a volcano erupts and collapses, often creating a basin that can fill with water or become a site for new volcanic activity.