Newest Volcano Notice Including Mount Rainier

Earthquake activity at Mount Rainier has returned to typical rates of seismicity, after the earthquake swarm that began on July 8, 2025.  The Volcano Alert Level and Aviation Color Code for Mount Rainier remained at NORMAL/GREEN throughout the swarm, as the activity was related to the volcano's hydrothermal system. The swarm resulted in over 1,350 located earthquakes and thousands of additional earthquakes too small to locate. The average depth of the earthquakes was about 2.8 miles (4.5 km) beneath the summit of the volcano. The largest earthquake of the swarm was a magnitude 2.42 on July 11, 2025. 

An earthquake swarm is a group of earthquakes that happen close together in both time and location. When the swarm began, it quickly reached a maximum rate of about 40 earthquakes per hour. Over the next several weeks, the rate of earthquakes decreased. The shift from an earthquake swarm to typical rates of activity isn’t marked by a single moment, but rather a gradual decrease interpreted through scientific review over time. After carefully reviewing the data, scientists from the U.S. Geological Survey Cascades Volcano Observatory (CVO) and the Pacific Northwest Seismic Network (PNSN) have determined that earthquake activity has returned to typical rates for Mount Rainier, which has averaged about 10 earthquakes per month for the last several decades. The hydrothermal processes that are believed to have caused the swarm may be continuing at levels too small to generate detectable seismicity. Therefore, there is a small chance of brief increases in seismic activity under the volcano in future days to months. A volcano’s hydrothermal system is how water underground interacts with the heat of a volcano – this process creates features that can be observed at the surface like hot springs and steam vents. Earthquakes, hot springs and steam vents remind us that Mount Rainier is an active volcano.

Recent activity

Additionally, in coordination with Mount Rainier National Park, CVO scientists conducted a helicopter gas survey of Mount Rainier on August 4, 2025. The results showed that the compositions and emission rates of gases emitted from active steam vents on Mount Rainier were broadly consistent with previous measurements. Similarly, the geodetic network did not record any unusual inflation or deflation at the volcano during the earthquake swarm.

What we are doing

Mount Rainier is monitored by a dense network of seismometers, infrasound sensors, GPS stations, and webcams. The USGS CVO and PNSN will continue to monitor Mount Rainier and release updates as needed.