Mount Rainier was experiencing "the most significant seismic activity" at the volcano in more than 15 years as an "earthquake swarm" hit the site starting on Tuesday.

Mount Rainier on Tuesday experienced its largest seismic activity since 2009, with a swarm of small earthquakes detected. According to the United States Geological Survey, hundreds of earthquakes were recorded.

Seismologists are closely monitoring Mount Rainier after a swarm of earthquakes struck the Pacific Northwest’s tallest volcano this week.