Major Earthquake Swarm Hits Mount Rainier, 1,010 Recorded Since July 8

MOUNT RAINIER, Washington — An earthquake swarm at Mount Rainier, which began on July 8, 2025, is now regarded as one of the largest ever recorded for the volcano. As of July 25, geologists have documented 1,010 small earthquakes.

The swarm began early on Tuesday morning, with the most significant tremor measuring 2.4 in magnitude on July 11. Seismologists with the Pacific Northwest Seismic Network are continuing to analyze data, stating that more tremors may yet be accounted for.

According to the U.S. Geological Survey Cascades Volcano Observatory (USGS), Mount Rainier typically experiences about nine earthquakes each month. While swarms occur once or twice a year, this particular event has far surpassed previous swarms in both magnitude and frequency.

The earthquake activity peaked at 41 events per hour on July 8, but has since slowed significantly, with only a few events per hour reported by July 25. USGS indicates that this seismic activity poses no threat to the public, maintaining the volcano’s color alert level at green.

Experts believe the current swarm relates to fluid movement along fault lines beneath the volcano. The USGS stated that these minor earthquakes are too small to be felt at the surface, explaining that ‘these events are too small to feel and the shaking from these is too small to trigger any additional activity from cliff faces or glaciers.’

Millennia of history indicate that while Mount Rainier has not erupted in over 1,000 years, it remains one of the most active volcanoes in the Pacific Northwest. The USGS monitors the volcano closely due to its proximity to large cities like Seattle and Tacoma, where lahars and pyroclastic flows could pose significant threats in the event of an eruption.

Experts caution that an eruption is not imminent, as they emphasized, ‘The volcano is not ‘due’ for an eruption and we do not see any signs of a potential eruption at this time.’ Nonetheless, researchers continue to monitor the seismic activity with great interest.