Mount Aso (Aso-san) is the largest active volcano in Japan, and is among the largest in the world. It stands in Aso Kuju National Park in Kumamoto Prefecture, on the island of Kyushu. Its peak is 1592 m above sea level. Aso has one of the largest caldera in the world (25 km north-south and 18 km east-west). The caldera has a circumference of around 120 km (75 miles), although sources vary on the exact distance.
Mount Aso erupted in Japan, spewing ash and lava and cancelling dozens of flights in the region, the AP reports. This volcano, one of the world's largest, last blew its top 22 years ago. There has been increased seismic activity in the region since August, although it wasn't clear when or even if it would erupt.
Officials warned people not to approach the summit or get near Mount Aso, and according to the Japan Times visitors had been banned from going within 1 kilometer of the crater. The last time Mount Aso erupted, three people were killed and 11 more were injured. As of publication time, no injuries have been reported as a result of the recent eruption.
The ash reached an elevation of one kilometer (3,280 feet) and could cause continuing air delays, according to the Japan Meteorological Agency. Officials don't expect the eruption to worsen, however.