Japan’s Mount Asama has erupted, throwing hot rocks out of the crater and depositing a fine layer of ash on parts of Tokyo, some 90 miles to the southeast.
Television footage showed white smoke rising from the 2,568-meter peak and experts are warning that a second eruption is possible.
The first explosion occurred at 1.51 am, according to Shomei Shirato, of the Japan Meteorological Agency, and was described as “small.” Rocks were thrown more than 1 km from the crater, although there have been no reports of injuries or serious damage.
The agency raised its alert level for the snow-capped volcano on Sunday after detecting signs of increased activity. Traffic in the area has been restricted and 45,000 local people warned to be ready to leave their homes should the danger intensify.
There were no signs of lava escaping from the crater of the volcano and experts from the National Institute of Advanced Industrial Science and Technology are trying to determine whether the initial eruption has eased the pressure within the volcano or is merely a precursor to a far larger explosion.
“Mount Asama has erupted in the past, but they have been mostly small events,” said Dr. Akira Takada, a volcano expert with the institute. “At the moment, we do not have enough data to predict whether there will be a larger eruption now.
“We are collecting and analysing ash from the volcano to try to determine the condition of the magma, but we do not have the answers right now to the interior system of the mountain,” he said.
Mount Asama has had frequent bouts of activity in recent years, with the last major eruption in September 2004.
Most worrying for the experts would be a repeat of the 1783 eruption, which caused the deaths of more than 1,500 people and widespread damage.
The 1783 eruption began with small scale activity in May, building up in intensity and scale before the main detonation in early August.
Japan – part of the Pacific “rim of fire” – has more than 100 active volcanoes and is regularly subject to seismic activity.