What is formed at oceanic-oceanic convergent boundaries?

At oceanic-oceanic convergent boundaries, one tectonic plate is subducted beneath another, leading to the formation of volcanic island arcs. This process occurs because the denser oceanic plate is forced down into the mantle under the lighter plate. As it descends, the subducted plate melts due to increased temperature and pressure, creating magma that rises to the surface and forms volcanoes. Over time, these volcanic activities can accumulate to create islands that constitute an arc shape, hence the term "volcanic island arcs."

Mountains are typically formed at continental-continental convergent boundaries and are not the primary feature of oceanic-oceanic convergence. Continental rift zones occur at divergent boundaries where a continent is splitting apart, while mid-ocean ridges are formed at divergent boundaries where two oceanic plates are moving away from each other. Therefore, the correct answer highlights the distinctive geological features formed specifically through the interactions of oceanic plates at convergent locations.