Data from the University of Utah’s seismograph stations show that dozens of quakes up to a magnitude of about 2.4 hit an area around Grizzly Lake throughout the day and at various depths. Michigan Technological University’s earthquake magnitude scale shows that earthquakes of a strength of 2.5 or less are usually not felt and tend to only be recorded by a seismograph.
Yellowstone is one of the most seismically active regions in the U.S, and swarms like this make up most of the earthquake activity in the park. On average, Yellowstone is hit by between 1,500 and 2,500 earthquakes every year.
The swarm of quakes came amid widespread park closures due to heavy flooding and rockslides due to what the U.S. National Park Service (NPS) described as “unprecedented amounts of rainfall.”
According to Al Jazeera, this is the first time all entrances to Yellowstone National Park have been closed to the public in 34 years. In 1988 the park was shut off following a series of wildfires that affected over a third of the park.
On Monday the NPS said all entrances to the park were temporarily closed due to the conditions, meaning no inbound traffic could access any of the park’s five entrances. The closures were expected to extend through Wednesday at least.
“Our first priority has been to evacuate the northern section of the park where we have multiple road and bridge failures, mudslides and other issues,” Yellowstone National Park superintendent Cam Sholly said in a statement.
Sholly added that the community of Gardiner, located on one of the park’s entrances, is currently isolated with residents lacking access to water or power in some areas and that the NPS is providing support.
“We will not know timing of the park’s reopening until flood waters subside and we’re able to assess the damage throughout the park,” Sholly said. “It is likely that the northern loop will be closed for a substantial amount of time. I appreciate the efforts of the Yellowstone team and partners to safely evacuate areas of the park and of our gateway community partners who are helping us through this major event.”
Photos posted online by the park show the extent of the flooding damage. Some show sections of roads submerged under murky water. Others show how parts of roads have collapsed into nearby rivers.