ATHENS, Greece — Multiple earthquakes are rattling Santorini, a volcanic island in Greece, prompting authorities to dispatch rescuers with tents, a sniffer dog and drones, and to shut schools on four islands.

Greece sits on multiple fault lines and is often rattled by earthquakes. Santorini is visited by about three million people annually, including many British tourists. One of the largest volcanic eruptions in history, around 1600 BC, formed the island in its current shape, while the last eruption in the area occurred in 1950.

More than 200 tremors have been registered since Friday between the Greek volcanic islands of Santorini and Amorgos.