Studying tree rings helped scientists pinpoint when Mount Rainier last sent a lahar down its steep slopes, which could help planners anticipate future mudflows.

“Volcanoes are now more closely monitored. We have a good chance now of determining when a volcano becomes restless,” says Don Swanson, a volcanologist reflecting on the lessons learned from the 1980 ...

America’s deadliest volcano has just rattled through more than 1,000 tiny earthquakes in a matter of days, a drumbeat of tremors that has revived old fears about catastrophic mudflows racing down its ...

An outpouring of magma isn’t the biggest risk to people downhill from Mount Rainier. The active volcano’s greatest danger comes from lahars — amalgams of mud, rock and water that are as dense as wet ...