Mount Aso in Kumamoto Prefecture is experiencing its first magmatic eruption in 21 years, the Metrological Agency's regional headquarters in Fukuoka announced Thursday.
The nation's largest active volcano has been spewing ash since Tuesday. The last magmatic eruption was recorded in February 1993.
The agency said its scientists have confirmed via helicopter that the smoke and fumes spewed by the volcano formed a 1,500-meter-high column at around 11:30 a.m. Thursday. Scoria, which are porous, dark volcanic rocks formed when gases are released from magma, have also been observed, a sign that a magmatic eruption is taking place.