Mount Rainier was experiencing “the most significant seismic activity” at the volcano in more than 15 years as an “earthquake swarm” hit the site starting on Tuesday, according to the U.S. Geological Survey’s Cascades Volcano Observatory.
The swarm — hundreds of small earthquakes hitting the same area in quick succession — started around 1:30 a.m. local time Tuesday and was continuing into Wednesday, data showed.
But there was no cause for concern, according to the Cascades Volcano Observatory, which monitors volcanoes across Washington, Oregon and Idaho. Some of the earthquakes were too small to even locate.
“Earthquakes are too small to be felt at the surface and will likely continue for several days,” the observatory said in a news release Tuesday. “There would be no damage caused by such small events.”
The last time Mount Rainier saw a large swarm was over a three-day period in 2009, when 1,000 earthquakes hit, with the largest being a magnitude 2.3.
Swarms usually occur once or twice a year, but they are not usually comprised of so many earthquakes, the observatory said. Scientists, however, are still learning about the volcano, which is active and has only been well-monitored since the 1980s.
The observatory noted that current warm temperatures at Mount Rainier are not connected to the small earthquakes, and said they are likely being caused by water movement around the crust above the magma chamber.
Mount Rainier, which rises to 14,410 feet above sea level, has not significantly erupted over the last 500 years, according to the U.S. Geological Survey.
