There are three types of volcanoes: active volcanoes that are currently erupting like Kilauea in Hawaii, dormant volcanoes that are currently sleeping but could erupt again, and extinct volcanoes that were thought unable to erupt but sometimes become reactivated like the volcano on Anatahan Island in 2003. Volcanoes have various parts including a magma chamber, vent, crater cone, and eject ash and gas clouds and lava when erupting. The eruption of Mount Vesuvius in 79 AD buried the city of Pompeii under ash, preserving it as a lost city until its rediscovery.