Some 4,000 people live on Miyakejima, half of whom were evacuated from their homes two weeks ago when an eruption was thought to be imminent. The evacuation order was lifted after experts said magma was flowing away from the island under the seabed. Major eruption Miyakejima and other neighbouring islands have been rocked by more than 14,000 earthquakes in recent weeks. The last major eruption of Mount Oyama was in 1983 when 400 houses were destroyed. In 1940 the explosion 11 people were killed.
Japan is in one of the world's most active seismic zones.
Four of the earth's tectonic plates meet in the region, causing earthquakes, tidal waves and eruptions as they grate together. In late March, a volcano erupted on Mount Usu on Japan's northern island of Hokkaido for the first time in 22 years. The sky darkened as Mount Oyama blew.