Rangers have been forced to say there is no evidence Yellowstone's supervolcano is about to blow, after a YouTube video of a herd of bison dashing through the park sparked fears of an imminent eruption.
The video , filmed by Leo Leckie, who has been studying Yellowstone for two decades, led to speculation the herd had sensed volcanic activity beneath the park's caldera.
Nearly 150,000 people have watched the video since it was posted.
The internet rumours gathered pace when a 4.8-magnitude earthquake - the largest to hit the area in more than 30 years - was recorded weeks after the video was shot.
But Al Nash, a spokesman for Yellowstone National Park, said: "We have heard about some pretty wild rumours - including one concerning the animals.
"We do have bison, elk and other animals that have moved outside the park recently, but they're doing that because we're in the depths of winter and food is a little hard to find in places.
"At this time of year, they tend to migrate to lower elevations where they think there might be something to eat that's easier to get at.
"When the snow melts off and things start to green up, those very same animals will walk right back into the park."
According to the US Geological Service (USGS), there has been an uplift in earthquake activity around Yellowstone's caldera.
The supervolcano last exploded into life 70,000 years ago and an eruption is likely to deposit huge quantities of ash across much of the country.
Yellowstone lies in the middle of the North American plate - one of several which make the so-called 'ring of fire', which stretches around the Pacific Ocean.
There are fears recent tremors in Chile and Los Angeles, California, both of which lie on the horseshoe-shaped boundary, could be a precursor for the huge earthquake scientists have long been predicting.
However, Mr Nash said there were "no signs" tectonic activity was about to cause Yellowstone's volcano to erupt.
"We see between 1,000 and 3,000 earthquakes a year in Yellowstone and most of them are so small no one ever feels them," he said.
"We've had this recent earthquake near the Norris geyser basin, but there were no injuries or damage and ... it's just part of the geology of Yellowstone."