Mt. Rainier rattled by rare, ongoing ‘earthquake swarm'
Beginning around 1:30 a.m., as many as several earthquakes a minute struck between 1 and 4 miles below the summit, in an ongoing swarm expected to last multiple days, according to the U.S. Geological Survey. The largest was a 1.7-magnitude quake, too small to feel at the surface or to cause any damage.
Authorities said the flurry of earthquakes below the 14,400-foot active volcano was not cause for concern. The volcano's alert level was listed as normal Tuesday afternoon.
It marks Mount Rainier's largest earthquake swarm since 2009, when geologists detected more than 1000 earthquakes over three days. The glacier-covered peak about 50 miles from Mount St. Helens typically sees about nine earthquakes a month, with smaller swarms occurring once or twice a year.
Earthquake swarms are clusters of temblors that strike the same area in rapid succession, as opposed to non-swarms, which usually come in the form of a large quake followed by smaller aftershocks. Though swarms can be caused by magma moving within a volcano, the phenomenon does not necessarily mean an eruption is imminent, according to the Pacific Northwest Seismic Network.
More often, geologists hypothesize, earthquake swarms happen when fluids flow through cracks in rock deep underground, causing pre-existing faults to slip. Tuesday's swarm looks similar to past swarms at Mount Rainier that likely stemmed from non-magma fluid motion, USGS spokesperson Holly Weiss-Racine said in an email.
Mount Rainier is located in the roughly 40 mile long Western Rainier Seismic Zone, an area where tectonic activity — not volcanic processes — causes frequent earthquakes. Though small earthquakes are common many miles beneath Rainier, very few have occurred within the volcano itself, according to the USGS. The largest earthquake recorded within Mount Rainier National Park was a magnitude 4.5 quake in 2006.
The USGS considers Mount Rainier the most threatening volcano in the Cascades and the third most dangerous volcano in the United States, because of its potential to trigger fast-moving mudflows that could threaten people and infrastructure as far as the Puget Lowlands. Geologists believe it last erupted about 1,000 years ago.
Try Our AI Features
Explore what Daily8 AI can do for you:
Comments
No comments yet...
Related Articles
Axios
3 hours ago
- Axios
Mount Rainier rattled by a swarm of quakes
Scores of tiny earthquakes rattled Mount Rainier this week, marking the largest swarm of earthquakes at the mountain since 2009, according to the U.S. Geological Survey. Why it matters: Even though scientists say there's no immediate cause for alarm, the uptick in seismic activity below what USGS calls the Cascade Range's " most dangerous volcano" has researchers and locals taking note.
Yahoo
4 hours ago
- Yahoo
Hundreds of small earthquakes recorded in Mount Rainier swarm for first time since 2009
PORTLAND, Ore. (KOIN) — Hundreds of small earthquakes have been detected at Mount Rainier in Washington in an earthquake swarm, the largest number seen in more than 15 years, according to geologists. The U.S. Geological Survey says the and started to detect the earthquakes just before 1:30 a.m. on Tuesday. Robert Atrops sentenced to life in prison for 1988 murder of estranged wife The earthquakes are currently numbering in the 'several hundred small events,' with the largest one reaching a 1.7-magnitude and the earthquakes hitting at depths of between 1.2 and 3.7 miles. 'Earthquake swarms are relatively common at Mount Rainier, typically occurring 1–2 times per year but usually with many fewer events than have been detected so far during the current swarm,' officials with USGS said in a . The last time , when the mountain saw more than 1,000 earthquakes in a three-day period, with the largest clocking a magnitude of 2.3. Homeowner scammed out of $33K by Silverton roofing contractor, police say So what's the cause of these earthquakes on Mount Rainier? 'Earthquake swarms like this have been attributed to circulation of hydrothermal fluids that are interacting with preexisting faults at shallow levels below the summit of the volcano,' according to USGS. Mount Rainier's GPS stations have not recorded any changes in ground deformation, which is a warning sign for potential eruption. Mount Rainier, which has the tallest Cascade Range peak at 14,409 feet, is listed as an 'active, ice-clad stratovolcano,' with strong geologic evidence of an eruption about 1,000 years ago. Copyright 2025 Nexstar Media, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.
Yahoo
4 hours ago
- Yahoo
Earthquake swarm strikes Mt Rainier in Washington state
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. The earthquake swarm started just before 1:30 a.m. local time, according to the U.S. Geological Survey's Cascades Volcano Observatory and the Pacific Northwest Seismic Network. Since the swarm began, hundreds of tiny earthquakes have occurred near the volcano's summit, with the largest's magnitude detected at 1.7. The earthquakes' origins have been recorded between 1.2 and 3.7 miles beneath the summit of the mountain. None have been felt on the surface, according to KPTV. Since Mount Rainier is an active volcano officials said the seismic activity wasn't abnormal and stressed there was no cause for alarm. The volcano's alert level has remained at normal, and its color code at green, which indicates typical activity. 'Mount Rainier typically sees about nine earthquakes per month,' the agencies said in a statement after the swarms were detected. 'Swarms like this happen once or twice a year, though this one is larger than usual.' The last significant earthquake at Mount Rainier occurred in 2009, and rumbled on for three days. More than 1,000 seismic events were recorded with the most substantial registering a 2.3 magnitude. Previous swarms have been attributed to fluids circulating under the mountain, and interacting with faults deep underground, and not volcanic activity. According to the U.S. Geological Survey, the last eruptive period for Mount Rainier occurred around 1,000 years ago, but even in that incident there were no lava flows. The last major destructive eruption to hit Washington state was not at Mount Rainier, but at Mount St Helens — approximately 50 miles away, but part of the same mountain range — in 1980. That eruption killed 57 people. The snowcapped Mount Rainier is located in Mount Rainier National Park, approximately 59 miles southeast of Seattle. The mountain is the highest peak in Washington state and on clear days is visible from Seattle.
