According to monitoring services from the United States Geological Survey (USGS), 73 earthquakes have hit Yellowstone in the past 28 days. This equates to almost three earthquakes a day on average, with the strongest registering as a magnitude 1.7 on July 7. Although all of the earthquakes have been small, some experts warn it is not necessarily the size of an earthquake which is the indication of an upcoming volcanic eruption, but more the quantity of them.
Portland State University Geology Professor Emeritus Scott Burns said: “If you get swarms under a working volcano, the working hypothesis is that magma is moving up underneath there.”
But others disagree about whether an earthquake swarm near a volcano could be a sign of things to come.
Jamie Farrell at the University of Utah in Salt Lake City believes this is just part of the natural cycle for Yellowstone volcano, saying: “Earthquake swarms are fairly common in Yellowstone.”
Yellowstone‘s National Park Service said that the region usually has about 700 earthquakes a year, so 73 earthquakes in a single month is not unheard of.
In fact, on the upper scale, Yellowstone can experience up to 3,000 quakes in a year.
The USGS says: “Almost all earthquakes at Yellowstone are brittle-failure events caused when rocks break due to crustal stresses.
“Though we’ve been looking at Yellowstone for years, no one has yet identified ‘long-period (LP) events’ commonly attributed to magma movement.
“If LP events are observed, that will NOT mean Yellowstone is getting ready to erupt. LP earthquakes commonly occur at other volcanoes in the world, including volcanoes in California, that have not erupted for centuries or millennia.”
The Yellowstone supervolcano, located in the US state of Wyoming, last erupted on a major scale 640,000 years ago.
According to the USGS, the chances of a Yellowstone eruption is around one-in-730,000.