Volcanic arc

Definition

A volcanic arc is a chain of volcanoes formed above a subducting tectonic plate, typically located near oceanic trenches. These arcs are the result of the melting of the subducted plate as it descends into the mantle, leading to magma formation and subsequent volcanic activity. Volcanic arcs often align with convergent plate boundaries, reflecting the dynamic nature of plate tectonics.

5 Must Know Facts For Your Next Test

1. Volcanic arcs are commonly found along the edges of tectonic plates, especially in regions where oceanic plates are subducting beneath continental plates.
2. The Andes mountain range in South America and the Cascade Range in North America are well-known examples of volcanic arcs.
3. The process of subduction not only leads to volcanic activity but also causes frequent earthquakes due to the movement of tectonic plates.
4. Volcanic arcs can significantly influence local climates and ecosystems due to their eruptions and ash fallout.
5. These arcs often contain stratovolcanoes, which are characterized by steep profiles and explosive eruptions due to the viscous nature of their magma.

Review Questions

• How does the process of subduction lead to the formation of a volcanic arc?
  • Subduction occurs when an oceanic plate converges with a continental plate, causing the denser oceanic plate to be forced underneath. As the oceanic plate descends into the mantle, it begins to melt due to increasing temperature and pressure. This melting generates magma, which can rise through the overlying continental crust, resulting in the formation of a volcanic arc at the surface as a chain of active volcanoes.
• Discuss the relationship between volcanic arcs and tectonic plate boundaries, providing examples of specific volcanic arcs.
  • Volcanic arcs are primarily associated with convergent plate boundaries, particularly where an oceanic plate subducts beneath a continental plate. For instance, the Andes mountain range represents a significant volcanic arc formed due to the Nazca Plate subducting beneath the South American Plate. Similarly, the Cascade Range in the Pacific Northwest of the United States is another example, resulting from the Juan de Fuca Plate subducting beneath the North American Plate.
• Evaluate how volcanic arcs contribute to geological hazards and their implications for nearby communities.
  • Volcanic arcs pose significant geological hazards such as explosive eruptions, ash fall, pyroclastic flows, and lava flows, which can impact surrounding communities severely. The risks associated with these hazards necessitate effective monitoring and emergency preparedness plans for populations living near these arcs. Additionally, eruptions can lead to long-term environmental changes, affecting air quality, agriculture, and water sources, thereby influencing local economies and public health.

Related terms

subduction zone: A subduction zone is an area where one tectonic plate is being forced under another, leading to geological phenomena such as earthquakes and volcanic activity.

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

trench: A trench is a deep, elongated depression in the ocean floor that forms at convergent plate boundaries, marking the location of subduction.