A volcanic arc is a chain of volcanoes formed above a subduction zone, where one tectonic plate moves under another and sinks into the mantle. This process causes melting of the mantle material, leading to magma formation that rises to the surface, creating volcanoes. These arcs typically form along oceanic-continental or oceanic-oceanic plate boundaries. A well-known example of a volcanic arc is the Andes Mountains in South America, which features numerous active volcanoes due to the subduction of the Nazca Plate beneath the South American Plate.