Final answer:
Island arcs are created by the subduction of one tectonic plate beneath another, leading to a series of volcanic eruptions that form a linear belt of islands, such as those in the Ring of Fire. These geologically active regions can also be hotspots for biological diversity through processes like allopatric speciation and adaptive radiation.
Step-by-step explanation:
Island arcs are formed by tectonic activity, specifically when an oceanic plate collides with another oceanic or continental plate and subducts beneath it. This subduction causes volcanic eruptions along the subduction zone, and the resulting volcanoes emerge over time as an island arc. A notable example of this is the Ring of Fire in the Pacific Ocean, which is a major area of earthquakes and volcanic activity that has indeed influenced both the landscape and human history in significant ways.
While many islands, such as the Bahamas, are formed by the rise of coral reefs, island arcs are typically volcanic in origin. Similarly, back arc basins form near volcanic arcs due to extension caused by mantle convection behind a subduction zone, providing further context to the dynamic geological activity that creates island arcs. Additionally, island chains like these provide conditions conducive to allopatric speciation and adaptive radiation, as seen in the example of Darwin's finches on the Galápagos Islands.