Here's how it works:

1. Subduction: One denser oceanic plate subducts (dives) beneath the other.

2. Melting: As the subducting plate descends, it heats up due to friction and the increasing pressure. This causes the rock to partially melt.

3. Magma Rise: The molten rock, called magma, is less dense than the surrounding rock and rises towards the surface.

4. Volcanic Eruptions: The magma eventually erupts through the overlying plate, forming volcanoes.

5. Island Arc Formation: Over time, these volcanic eruptions create a chain of islands known as an island arc, which runs parallel to the convergent boundary.

Examples of island arcs include:

* The Mariana Islands in the western Pacific Ocean

* The Aleutian Islands off the coast of Alaska

* The Japanese Archipelago

These island arcs are typically characterized by:

* Volcanic activity: Frequent eruptions and geothermal activity

* Deep ocean trenches: A deep depression in the ocean floor where the subducting plate descends

* Earthquakes: Frequent and sometimes powerful earthquakes due to the movement of the plates