JMA reported that the sulfur dioxide emission rate at Minamidake crater (at Aira Caldera?s Sakurajima volcano) was somewhat high on 16 April at 1,600 tons/day.
An explosion on 17 April generated a plume that rose 2 km above the crater rim and ejected material as far as 900 m.
During 19-22 April plumes from two events rose as high as 1.4 km.
The Alert Level remained at 3 (on a 5-level scale).
Source: Japan Meteorological Agency (JMA)