Continental arc

Definition

A continental arc is a curved chain of volcanoes that form along the edge of a continental plate, typically at a convergent boundary where an oceanic plate is subducting beneath it. This geological feature arises due to the melting of the subducted oceanic plate, which generates magma that rises to create volcanic activity on the continental crust above. The formation of continental arcs is closely linked to the processes of magmatism and the tectonic interactions at convergent boundaries.

5 Must Know Facts For Your Next Test

1. Continental arcs are typically found at convergent boundaries where an oceanic plate is being forced beneath a continental plate, leading to intense geological activity.
2. The magma that forms in continental arcs often has a higher silica content than that from oceanic arcs, resulting in more explosive volcanic eruptions.
3. Some well-known examples of continental arcs include the Andes Mountains in South America and the Cascade Range in the Pacific Northwest of the United States.
4. The presence of continental arcs is an indicator of ongoing tectonic processes and can significantly impact regional geology and ecosystems.
5. Continental arcs not only contribute to volcanic activity but also lead to the uplift and formation of mountain ranges over geological timescales.

Review Questions

• How does the process of subduction contribute to the formation of a continental arc?
  • Subduction occurs when an oceanic plate converges with a continental plate, causing the denser oceanic plate to be forced underneath. As it sinks into the mantle, this oceanic crust undergoes high-pressure and high-temperature conditions, which lead to its partial melting. The resultant magma rises through the continental crust, resulting in volcanic activity that creates a curved chain of volcanoes known as a continental arc.
• Compare and contrast continental arcs with volcanic island arcs in terms of their formation and geological features.
  • Continental arcs form at convergent boundaries where an oceanic plate subducts beneath a continental plate, while volcanic island arcs occur where one oceanic plate subducts beneath another oceanic plate. Continental arcs typically produce more explosive volcanoes due to their higher silica content in magma compared to island arcs. Additionally, continental arcs contribute to the uplift of land and mountain ranges, while volcanic island arcs primarily consist of chains of islands formed from erupted lava.
• Evaluate the impact that continental arcs have on local ecosystems and geological processes over time.
  • Continental arcs significantly influence local ecosystems by creating diverse habitats through varying volcanic landscapes. The nutrient-rich soils formed from volcanic ash can enhance vegetation growth, supporting various animal species. Additionally, these geological features are integral to tectonic processes, contributing to mountain-building events and altering landscapes over geological timescales. The ongoing volcanic activity can also reshape ecosystems repeatedly, demonstrating the dynamic interplay between geology and biology in these regions.

Related terms

subduction zone: A subduction zone is an area where one tectonic plate moves under another, leading to significant geological activity, including earthquakes and volcanic eruptions.

volcanic island arc: A volcanic island arc is a chain of volcanic islands that forms on an oceanic plate as it subducts beneath another oceanic plate, typically creating a series of explosive volcanoes.

magma generation: Magma generation refers to the process by which molten rock is produced within the Earth, often due to the melting of rocks in subduction zones or hotspots.