Mount Asama, a volcano on the border of Japan’s Gunma and Nagano prefectures has erupted On April 2, 2017.
People in the vicinity immediately took to Twitter to share impressive pictures of the raging coloseus that hadn’t explosed since 2009. Asamayama (also known as Asama and Azumayama) has been relatively quiet since an eruption during January-February 2009.
Based on JMA monthly reports, there was no exceptional activity during 2011-2013. However, during 2014, the frequency of shallow volcanic earthquakes and tremors occurring immediately under the summit crater began to increase. In late April 2015, volcanic seismicity further increased. Because of this increase in activity and the possibility of a small eruption, JMA raised the Alert Level on 11 June from 1 to 2 (on a scale of 5), and warned people not to approach the crater. The volcano remained in “a somewhat active state” in 2016 through at least September, and JMA kept the Alert Level at 2 through that time. Very small eruptions were reported by JMA from the summit crater on 16 and 19 June 2015 that generated ashfall to the NE within 4 km of the crater. Scientists aboard an overflight later that day observed the crater venting white to blue-white gas.