Composite volcano

Definition

A composite volcano, also known as a stratovolcano, is a steep, conical volcano characterized by its layered structure of alternating lava flows, ash, and other volcanic debris. These volcanoes are typically associated with explosive eruptions due to the viscosity of their magma, which can trap gas and lead to pressure build-up before an eruption occurs. Composite volcanoes are often found at convergent plate boundaries and can create significant volcanic landforms and products.

5 Must Know Facts For Your Next Test

1. Composite volcanoes are often characterized by their steep slopes and symmetrical shape, making them visually striking geological features.
2. The eruptions of composite volcanoes can vary greatly, from explosive events that produce pyroclastic flows to quieter lava flows.
3. Examples of well-known composite volcanoes include Mount St. Helens in the United States and Mount Fuji in Japan.
4. The alternating layers of lava and tephra contribute to the composite structure, which provides strength and stability to these volcanoes.
5. Composite volcanoes can pose significant hazards to nearby populations due to their explosive potential and the dangers associated with pyroclastic flows, ashfall, and lahars.

Review Questions

• What are the main characteristics that distinguish composite volcanoes from other types of volcanoes?
  • Composite volcanoes are distinct from other types, such as shield or cinder cone volcanoes, primarily due to their steep slopes, layered structure of lava and tephra, and their propensity for explosive eruptions. The viscosity of their magma leads to gas build-up, resulting in powerful eruptions that can produce pyroclastic flows. In contrast, shield volcanoes have gentle slopes created by low-viscosity lava flows, while cinder cone volcanoes are smaller and formed mainly by ejected tephra.
• Discuss the role of tectonic plate boundaries in the formation of composite volcanoes.
  • Composite volcanoes typically form at convergent plate boundaries where an oceanic plate subducts beneath a continental plate. This process causes melting of the mantle, leading to magma generation that rises through the crust. The interaction between the subducting plate and the overlying continental crust contributes to the explosive nature of eruptions from composite volcanoes, as the magma can become highly viscous due to the incorporation of water and other volatile components.
• Evaluate the environmental impact and risks associated with living near composite volcanoes.
  • Living near composite volcanoes poses significant risks due to their potential for explosive eruptions and associated hazards such as ashfall, pyroclastic flows, and lahars. These eruptions can devastate surrounding landscapes, disrupt air travel due to ash clouds, and lead to loss of life and property. Additionally, the long-term environmental impacts may include changes to local ecosystems, soil degradation from ash deposits, and contamination of water sources. Understanding these risks is crucial for effective disaster preparedness and risk management in areas prone to volcanic activity.

Related terms

Magma: Magma is molten rock located beneath the Earth's surface, which can rise to form volcanic eruptions when it reaches the surface.

Tephra: Tephra refers to the fragments of volcanic rock and ash that are ejected during explosive eruptions and can accumulate around the volcano.

Caldera:

A caldera is a large depression formed when a volcano erupts and collapses, often resulting in a significant change in the landscape.