What term describes curving chains of mostly volcanic islands across the seafloor?

The term that describes curving chains of mostly volcanic islands across the seafloor is "arcs." These formations are typically associated with subduction zones where one tectonic plate moves under another and is forced into the mantle, creating volcanic activity that leads to the formation of islands.

As magma rises from these subducted plates, it can create a series of volcanoes that appear as an arc shape due to the dynamics of plate movements and the angle at which the subduction occurs. This pattern is commonly observed in regions such as the Aleutian Islands in Alaska or the Mariana Islands in the Pacific Ocean, where the volcanic activity results in a chain of islands forming an arc.

In contrast, ridges refer to underwater mountain ranges formed by the upwelling of magma at divergent plate boundaries, trenches are deep underwater valleys formed where one plate is subducting under another, and rifts are areas where tectonic plates are moving apart, leading to the formation of new crust.