What is a volcanic arc?

A volcanic arc is indeed a chain of volcanoes that forms above a subducting tectonic plate. This geological feature emerges at convergent plate boundaries, where one tectonic plate is forced beneath another. As the subducting plate descends into the mantle, it undergoes melting due to the high temperatures and pressures encountered. The molten material, or magma, then rises to the surface, leading to the formation of volcanoes that are often aligned in a curved pattern, resulting in a volcanic arc.

This process is crucial in understanding plate tectonics, as it illustrates how the movement of tectonic plates influences volcanic activity and the distribution of volcanoes across the globe. The formation of a volcanic arc exemplifies the dynamic nature of Earth’s lithosphere and highlights the interactions between different tectonic plates in shaping our planet's geological features.

In contrast to the other options, underwater geysers do not specifically relate to the concept of subduction or volcanic activity. Erosion is a different process that involves the wearing away of landforms, and while tectonic uplift can create mountain ranges, it does not typically result in the formation of volcanic arcs, which are directly tied to the subduction processes.