Science Olympiad Dynamic Planet Practice Test

What is an island arc?

1. A submerged volcanic island

2. A string of volcanoes formed by the subduction of oceanic plates

3. A type of coral reef

4. A linear chain of mountains

The correct answer is: A string of volcanoes formed by the subduction of oceanic plates

An island arc is characterized as a string of volcanoes formed by the subduction of oceanic plates. This geological process occurs when one tectonic plate, typically an oceanic plate, is forced beneath another plate, which can also be oceanic. As the subducted plate descends into the mantle, it melts and generates magma, which rises to the surface, resulting in the formation of volcanoes. Over time, the continuous volcanic activity leads to the emergence of a series of islands that form an arc-like shape, usually parallel to the trench created by the subduction zone. This phenomenon is commonly observed in areas such as the Pacific Ring of Fire. The other options do not accurately define an island arc. A submerged volcanic island is a specific volcanic landform that may eventually contribute to an island arc but does not represent the arc itself. A type of coral reef refers to a marine structure formed by coral polyps and has no relation to tectonic activities or volcanic formations. A linear chain of mountains could refer to mountain ranges formed by a variety of geological processes, including continental collision, but it does not imply the volcanic activity associated with subduction that is characteristic of island arcs.