Updated | Yellowstone supervolcano has been hit by a series of earthquakes, with more 400 recorded since June 12. The latest was recorded on Monday, June 19, with a magnitude 3 earthquake striking 8.6 miles north northeast of West Yellowstone, Montana.

The swarm began last week, and on June 15 saw a magnitude 4.5 earthquake take place in Yellowstone National Park. “The epicenter of the shock was located in Yellowstone National Park, eight miles north-northeast of the town of West Yellowstone, Montana,” scientists from the University of Utah, which monitors Yellowstone Volcano, said in a statement.

“The earthquake was [reportedly] felt in the towns of West Yellowstone and Gardiner, Montana, in Yellowstone National Park, and elsewhere in the surrounding region.”

This earthquake was the largest to have hit Yellowstone since March 30, 2014, when a magnitude 4.8 earthquake was recorded 18 miles to the east, near the Norris Geyser Basin.

“[The 4.5] earthquake is part of an energetic sequence of earthquakes in the same area that began on June 12,” the statement continued. “This sequence has included approximately thirty earthquakes of magnitude 2 and larger and four earthquakes of magnitude 3 and larger, including today’s magnitude 4.5 event.”

As of June 19, 464 events had been recorded. Most of these ranged in the magnitude of 0 to 1, with five less than zero, indicating they occurred at depths ranging from about 0 miles to about 9 miles. “This is the highest number of earthquakes at Yellowstone within a single week in the past five years, but is fewer than weekly counts during similar earthquakes swarms in 2002, 2004, 2008 and 2010,” scientists said.

yellowstone usgs Map shows the magnitude 3 earthquake that struck Yellowstone on June 19. USGS

The University of Utah is part of the Yellowstone Volcano Observatory (YVO), which monitors volcanic and earthquake activity in Yellowstone National Park. Seismic activity at volcanoes can signal an eruption is due to take place, although predicting exactly when a volcano will erupt is, at present, impossible.

Experts at the U.S. Geological Survey (USGS) say the risk of an eruption at Yellowstone supervolcano is low—the current volcano alert level remains normal and the aviation color code, which provides information on the potential risk to fights, is green—meaning the volcano is in a normal, non-eruptive state.

A spokesperson from the USGS and YVO tells Newsweek the current activity appears to be “slowly winding down” and that “no other geological activity has been detected.”

The probability of a large eruption at Yellowstone in the next year is currently calculated at one in 730,000.

yellowstone View of the ‘Grand Prismatic’ hot spring in Yellowstone National Park. Mark Ralston/AFP/Getty Images

But what would happen if it did erupt? In 2014, scientists with the USGS published a report where they modeled what would happen if a large, explosive eruption took place at the supervolcano. Their findings showed most of the country would be covered in a blanket of ash, with some areas being buried up to a meter deep.

However, the USGS also said that if Yellowstone were to erupt, it would likely be far smaller than the one modeled. They also described what would concerning signs of activity would constitute: “Yellowstone hasn’t erupted for 70,000 years, so it’s going to take some impressive earthquakes and ground uplift to get things started,” the team said in a press release.

“Besides intense earthquake swarms (with many earthquakes above M4 or M5), we expect rapid and notable uplift around the caldera (possibly tens of inches per year). Finally, rising magma will cause explosions from the boiling-temperature geothermal reservoirs. Even with explosions, earthquakes and notable ground uplift, the most likely volcanic eruptions would be the type that would have minimal effect outside the park itself.”

This story has been updated with the current number of events since the swarm began, per a statement from the USGS on June 19, and an explanation about earthquakes with a magnitude of less than zero.