Geologists studying the supervolcano complex fear a magnitude-7.0 or higher earthquake is an “under-appreciated hazard”. Michael Poland, the chief scientist in charge of the Yellowstone Volcano Observatory (YVO) stressed such earthquakes have happened before and will happen again. The Yellowstone expert said: “The biggest concern we have for Yellowstone is not with the volcano, it’s with earthquakes. “This is an under-appreciated hazard in the Yellowstone area. There can and will be in the future magnitude 7 earthquakes.”

Mr Poland said these powerful earthquakes occur “on a human life scale”, meaning they happen every 100 years or so. The last major Yellowstone earthquake, magnitude-7.3, struck in August 1959 and killed up 28 people in landslides. The so-called Hebgen Lake earthquake remains the strongest earthquake on record in Yellowstone. The quake is estimated to have moved more than 80 million tonnes of rock around, blocking off a river and creating a new body of water in Montana – Hebgen Lake.

Yellowstone volcano: A major earthquake is a bigger risk than eruption

A very similar magnitude-7.8 earthquake ripped through San Francisco, California, in 1906.

There can and will be in the future magnitude 7 earthquakes Michael Poland, Yellowstone Volcano Observatory

The earthquake collapsed vast sections of the city and killed roughly 3,000 people. In comparison, the Yellowstone supervolcano erupted two million, 1.3 million and 640,000 thousand years ago – hundreds of thousands of year before humans were even on the planet. Each year, anywhere between 1,000 and 3,000 earthquakes strike the Yellowstone National Park but most go unnoticed.

The weaker tremors typically strike deep beneath the park’s surface due to a high number of faults surrounding Yellowstone volcano. The US National Parks Service (NPS) said the earthquakes hit along fractures in the Earth’s crust where plate movement and volcanic activity peak. When the rock slips or breaks, seismic waves rush upwards to the surface in the form of tremors. The NPS said: “Yellowstone commonly experiences ‘earthquake swarms’ – a series of earthquakes over a short period of time in a localised area.

Yellowstone volcano: A magnitude 7.3 earthquake last struck Yellowstone in 1959

Yellowstone earthquake: The last volcano eruption took place 640,000 years ago