A Volcanic arc is a succession of volcanoes extending in a line over a vast area (typically several hundred kilometres), more or less in the shape of an arc.
A volcanic arc is caused by subduction, i.e. the sliding of an oceanic plate under another plate (continental or oceanic). The sliding action causes folds in the upper plate, generating seismic and volcanic activity.
The ring of fire is a succession of volcanic arcs stretching around the Pacific ocean rim, from New Zealand to South America via the Aleutian islands. The Lesser Antilles form a volcanic arc and there is also one around the Mediterranean.