The volcano sent superheated clouds of debris cascading down its slopes and lava streams flowing for miles.
Residents of more than two dozen villages have been living in temporary shelters outside a 3-mile danger zone, some for months.
Many of their homes and farms have been blanketed with a thick layer of ash and other debris while they’ve been gone.
Indonesian geologists say magma beneath Sinabung is rising from deep within the Earth, swelling the size of the lava dome near its peak.
That dome occasionally collapses, triggering pyroclastic clouds and gushes of lava.
Sinabung roared to life in 2010 after lying mainly dormant for 400 years.