Merapi's deadly eruptions continued as Indonesia struggles to recover from a 7.7-magnitude earthquake that triggered a 10-foot (3-meter) tsunami.
The earthquake resulted from the subduction of one of the Earth's rocky plates below another (a process called thrust faulting).
More than 320,000 people have fled to evacuation centers about 12.4 miles (20 kilometers) from the volcano, according to the Indonesian National Disaster Management Agency.
Pyroclastic flows — scorching rivers of gas and rock — are the biggest threat, and several were spotted flowing down the mountain over the weekend and were observed by NASA satellites.
Merapi constantly dumps volcanic ash during its eruptions on the fields below.