Mount Rainier is an active stratovolcano 45 miles southeast of Tacoma and 60 miles south-southeast of Seattle. Its last eruption was "a light dusting of ash" in 1894, the USGS said in a report. Large eruptions haven't occurred for more than 1,000 years.

A swarm of hundreds of small earthquakes have been detected rumbling deep below Mt. Rainier in Washington State early Tuesday morning, though geologists stress there is no cause for concern.

Mount Rainier, the active volcano towering above southwestern Washington state, started rumbling — very lightly — on Tuesday. A swarm of small earthquakes was detected under the mountain triggering focused monitoring from officials. But researchers have determined there is no current threat of an eruption.