When people hear about a natural disaster happening in Japan, they most often assume that it’s another earthquake. And with an earthquake happening almost every day, they are mostly guessing correctly. What is often forgotten however, is that Japan is also the home of many volcanoes, and most of them are just dormant and can erupt again at any time.
This is just what happened late yesterday night, when Mt. Asama erupted and sent a pillar of smoke some 1800 metres into the sky. Mt. Asama is 2568 metres high and one of the most active volcanoes in Japan; the last eruption was 10 years ago. Since the volcano is on the borders of Gunma and Nagano prefecture, it is a popular hiking spot, but the region is not very densely populated.
Still, the government has forbidden access to the volcano as a whole, and is trying to evacuate all hikers that are in the area. Judging from the youtube video below, taken today, the situation has cooled down a little.
See also this interesting article at Kyodo News, which is relatively level-headed and includes a great map of the many other (and so far quiet) volcanoes in the area and a link to the Japan Meteorological Agency and their volcanic warning page just below the map.