Latest news with #HollyWeiss-Racine
Yahoo
10-07-2025
- Science
- Yahoo
Mount Rainer is rattled by more than 300 earthquakes. It's the largest swarm in years.
More than 300 earthquakes have erupted at Washington's Mount Rainier this week, the largest earthquake swarm at the volcano since 2009. As of Thursday, July 10, 334 earthquakes had been identified at Mount Rainier by the Pacific Northwest Seismic Network (PNSN), Cascades Volcano Observatory Public Information Officer Holly Weiss-Racine told USA TODAY. The swarm, a cluster of earthquakes occurring in the same area in rapid succession, began in the early morning of Tuesday, July 8. Scientists do not have any concerns about the earthquakes, the Cascades Volcano Observatory states. The largest so far was recorded at a magnitude of 2.3 on Wednesday, July 9. Weiss-Racine said the rate peaked at 26 earthquakes per hour on the morning of July 8 and has decreased to "a few" per hour on the morning of July 10. The PNSN is continuing to locate earthquakes a part of the swarm. Updates are shared on the PNSN website at The earthquake swarm is not dangerous to hikers on the mountain and has posed no indication for concern, the Cascades Volcano Observatory wrote in a news release. As of July 10, the largest earthquake in the swarm was recorded at a magnitude of 2.3. According to Michigan Technological University, earthquakes of a 2.5 or less magnitude are common – millions happen each year – and are not usually felt. Earthquake guide: Earthquakes happen all the time, you just can't feel them. About nine earthquakes per month are common at Mount Rainier, according to the Cascades Volcano Observatory. Earthquake swarms typically occur one or two times a year at the volcano but are not as large. The last large earthquake swarm at Mount Rainier occurred in 2009 and lasted for three days. The swarm resulted in more than 1,000 earthquakes and the largest was of a 2.3 magnitude, according to the U.S. Geological Survey. The Cascades Volcano Observatory states that Mount Rainier is not "due" for an eruption and no signs point to an eruption at this time. But generally, earthquakes can be related to subsequent volcanic eruptions, according to the U.S. Geological Survey. However, the circumstances have to be just right. For a volcano to be triggered into eruption by earthquakes, a volcano must have enough "eruptible magma" and significant pressure within its magma storage, the U.S. Geological Survey states. Mount Rainier hasn't had a major eruption, with strong geologic evidence, in the past 1,000 years, Weiss-Racine said. Greta Cross is a national trending reporter at USA TODAY. Story idea? Email her at gcross@ This article originally appeared on USA TODAY: Mount Rainier experiences more than 300 earthquakes in 2 days
USA Today
10-07-2025
- Science
- USA Today
Mount Rainer is rattled by over 300 earthquakes. It's the largest swarm in years.
The last large earthquake swarm at Mount Rainier occurred in 2009. During that time, more than 1,000 earthquakes rattled the volcano. More than 300 earthquakes have erupted at Washington's Mount Rainier this week, the largest earthquake swarm at the volcano since 2009. As of Thursday, July 10, 334 earthquakes had been identified at Mount Rainier by the Pacific Northwest Seismic Network (PNSN), Cascades Volcano Observatory Public Information Officer Holly Weiss-Racine told USA TODAY. The swarm, a cluster of earthquakes occurring in the same area in rapid succession, began in the early morning of Tuesday, July 8. Scientists do not have any concerns about the earthquakes, the Cascades Volcano Observatory states. The largest so far was recorded at a magnitude of 2.3 on Wednesday, July 9. Weiss-Racine said the rate peaked at 26 earthquakes per hour on the morning of July 8 and has decreased to "a few" per hour on the morning of July 10. The PNSN is continuing to locate earthquakes a part of the swarm. Updates are shared on the PNSN website at Is the earthquake swarm dangerous? The earthquake swarm is not dangerous to hikers on the mountain and has posed no indication for concern, the Cascades Volcano Observatory wrote in a news release. As of July 10, the largest earthquake in the swarm was recorded at a magnitude of 2.3. According to Michigan Technological University, earthquakes of a 2.5 or less magnitude are common – millions happen each year – and are not usually felt. Earthquake guide: Earthquakes happen all the time, you just can't feel them. Are earthquakes common at Mount Rainier? About nine earthquakes per month are common at Mount Rainier, according to the Cascades Volcano Observatory. Earthquake swarms typically occur one or two times a year at the volcano but are not as large. When was the last sizeable earthquake swarm at Mount Rainier? The last large earthquake swarm at Mount Rainier occurred in 2009 and lasted for three days. The swarm resulted in more than 1,000 earthquakes and the largest was of a 2.3 magnitude, according to the U.S. Geological Survey. Can the earthquake swarm cause a volcanic eruption? The Cascades Volcano Observatory states that Mount Rainier is not "due" for an eruption and no signs point to an eruption at this time. But generally, earthquakes can be related to subsequent volcanic eruptions, according to the U.S. Geological Survey. However, the circumstances have to be just right. For a volcano to be triggered into eruption by earthquakes, a volcano must have enough "eruptible magma" and significant pressure within its magma storage, the U.S. Geological Survey states. When was the last time Mount Rainier erupted? Mount Rainier hasn't had a major eruption, with strong geologic evidence, in the past 1,000 years, Weiss-Racine said. Greta Cross is a national trending reporter at USA TODAY. Story idea? Email her at gcross@
San Francisco Chronicle
08-07-2025
- Science
- San Francisco Chronicle
Mt. Rainier rattled by rare, ongoing ‘earthquake swarm'
Geologists detected hundreds of small earthquakes at Mount Rainier Tuesday in the largest earthquake swarm measured there in more than 15 years. 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.
