A string of small volcanic islands is most likely to form at a convergent plate boundary, specifically a subduction zone. In a subduction zone, one tectonic plate is forced beneath another plate into the Earth's mantle. As the subducting plate sinks, it begins to melt due to the increasing temperature and pressure. This melting of the subducting plate creates magma, which eventually rises to the surface as volcanoes. Over time, these volcanic eruptions build up and form a chain of volcanic islands. One famous example is the "Ring of Fire" in the Pacific Ocean, which is a string of volcanoes and volcanic islands formed by the subduction of the Pacific Plate beneath other plates.
