by A sudden swarm of earthquakes rattled Mount Rainier in the early hours of Tuesday morning, with hundreds of small quakes detected in just a few hours — marking the volcano’s most significant seismic activity since 2009.
The U.S. Geological Survey (USGS) and Cascade Volcano Observatory (CVO) are closely monitoring the situation, though scientists emphasize there’s no current threat of eruption.
“These earthquakes are a reminder that Mount Rainier is an active volcano,” said Weston Thelen, a research seismologist with the CVO, in a statement to Newsweek. “Based on our observations, we think the most likely cause of the earthquakes is water moving around the crust above the magma chamber.”
Why It Matters
Located just 45 miles southeast of Tacoma and 60 miles from Seattle, Mount Rainier looms over a heavily populated region. Although the volcano last released only a “light dusting of ash” in 1894, its potential for future activity keeps it under constant observation. Tuesday’s earthquake swarm — far exceeding the usual monthly average of nine quakes — has naturally stirred public concern.
However, the USGS has reassured the public that there is no indication of an impending eruption. The volcano’s alert level remains NORMAL, and its aviation color code is GREEN, indicating no unusual volcanic activity.
What to Know
- The swarm began at 1:29 a.m. local time on Tuesday.
- The largest earthquake recorded so far was only a magnitude 1.6, well below the threshold for human detection.
- For perspective, damage generally doesn’t occur until earthquakes reach a magnitude of 4.0 or higher.
- Earthquake swarms occur once or twice a year at Mount Rainier, but rarely with this intensity. The last comparable swarm was in 2009, involving more than 1,000 quakes over three days.
USGS scientists believe the swarm is linked to fluid circulation interacting with preexisting faults, not magma movement.
What Happens Next
Monitoring will continue around the clock. Thelen noted that it’s unclear how long the swarm will last or whether it might intensify, but emphasized that such events are not unusual for Mount Rainier.
“While swarms can be unsettling, especially in a region with a volatile geological history, there is currently no cause for alarm,” Thelen said.
Authorities are advising residents to stay informed through official USGS updates, and not to rely on speculation or social media rumors.
