Island Arcs – Curved Chains of Volcanic Islands

🔹 Definition:

An island arc is a curved chain of volcanic islands that forms along a subduction zone, where an oceanic plate sinks beneath another oceanic plate. This process results in volcanic activity, earthquakes, and the formation of a deep ocean trench parallel to the arc.

🔹 Formation Process:

1. Subduction Begins:

   • At convergent plate boundaries, one oceanic plate is forced beneath another.

   • The descending plate enters the mantle, forming a trench (e.g., Mariana Trench).

2. Melting of Subducted Plate:

   • Water and sediments from the subducting plate lower the melting point of the mantle above it.

   • This generates magma through partial melting.

3. Volcanism:

   • The magma rises and forms a chain of volcanic islands on the overriding plate.

   • These islands are usually curved due to the spherical geometry of Earth.

🔹 Features of Island Arcs:

🔹 Examples of Island Arcs:

🔍 Difference Between Island Arc and Volcanic Arc:

• Island Arc: Oceanic–oceanic subduction; islands form in ocean.

• Volcanic Arc: Oceanic–continental subduction; volcanoes form on land (e.g., Andes Mountains).