Sep 4, 2014; Seattle, WA, USA; General view of Mt. Rainier. Mandatory Credit: Kirby Lee-Imagn Images Kirby Lee-Imagn Images

Hundreds of Miniature Earthquakes Rock Mt. Rainier

Originally posted on Outdoors on SI | By John Waechter | Last updated Jul 18, 2025 5:15 PM ET

Small earthquakes have rocked the active volcano Mt. Rainier in the Cascade Mountain Range this month, sending shockwaves around the 14,410-foot mountain. The United States Geological Survey reported that over 350 earthquakes rattled Rainier from July 8 to July 10.

Geologists refer to such activity as a ‘swarm’ of earthquakes, which are not uncommon, but this particular swarm was massive. While jolting, the series has not caused any damage, restricted hiking and climbing in the area, or altered the current alert level, which remains normal.

The Cascade Mountain Range region typically experiences approximately nine small earthquakes each month. So the July swarm caught the attention of the experts who monitor the sensitive area. Swarms usually occur once per year, but this swarm was far more substantial than average.

A Massive Amount of Miniature Earthquakes Shake Mt. Rainier

The Pacific Northwest Seismic Network tracks all swarms, noting that one of the most significant shocks registered 2.3 on the Richter scale. This swarm appears to be calming down after two days of substantial miniature earthquake activity.

Lou Bodenhemier reported in ExplorersWeb that the last comparable earthquake swarm occurred in 2009, when approximately 120 miniature events were detected in the Rainier region. The current swarm amounts to around three times that occurrence, though experts are not sounding any major alarms at this point.

“We’ve only been monitoring it [Rainier] for 40, maybe 50 years now. So just because it’s the most significant one we’ve seen on equipment doesn’t mean this hasn’t happened in the past,” cautioned Alex Iezzi, a geophysicist with the Cascades Volcano Observatory.

The Cascade Mountain Range: ‘Pacific Ring of Fire’

The Ring of Fire is a path along the Pacific Ocean where the majority of the Earth’s active volcanoes reside, attracting mountaineering adventurers.

Mountaineers flock to the Pacific Northwest annually to challenge the iconic Cascade mountains, known as the ‘Pacific Ring of Fire’. The Cascade Mountain Range, located in western North America, stretches from southern British Columbia through Washington and Oregon to Northern California. The diverse ecosystems of this mountain range support a wide range of wildlife, including black bears, elk, and mountain goats.

The range features active volcanoes with significant geothermal activity. This group of ancient and rugged mountains is prone to erupting at any time, hence the combustible name. The Cascade Mountains are relatively young in geological terms, with their formation primarily occurring over the past 40 million years. However, the high volcanic peaks within the range have formed within the last few million years. These alluring and climbable peaks include:

The Cascade Mountains

Mount Rainier: Mt. Rainier stands at 14,411 ft. and is the highest peak in the Cascade Range and the state of Washington. This active stratovolcano is the most glaciated mountain in the lower 48 US states.

Mount St. Helens: Mount St. Helens was once the fifth-highest peak within the Cascade Range, standing at 9,677 ft. That all changed in 1980 when the volcano erupted, and the mountain's stature was reduced by approximately 1,300 ft. Mt. St. Helens now reaches 8,366 ft.

Mount Adams: This stratovolcano rises to 12,281 ft., making it the second-highest peak in Washington State. It is known for its symmetrical appearance and less frequent eruptions.

Mount Hood stands at 11,240 feet, making it the highest peak in Oregon. It’s a potentially active stratovolcano and an excellent destination for climbing and skiing.

Mount Jefferson, located in Oregon, reaches an elevation of 10,497 feet. This stratovolcano is less accessible than most of the prominent members of ‘The Ring of Fire’.

Mount Baker: This northern Washington peak rises to 10,781 ft. It is the 2nd most glaciated mountain in the lower 48 US states, making it a formidable mountaineering challenge. Beyond its potential volcanic activity, Mt. Baker is among the snowiest places on Earth.

Lassen Peak, located in Northern California, reaches an elevation of 10,457 ft. It resides in the southernmost part of the Cascade Range and last erupted in the early 20th century.

This article first appeared on Outdoors on SI and was syndicated with permission.

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