The road was melting . Extreme heat from thermal features at Yellowstone National Park , created by the active volcano below the park , caused oil to bubble on a road surface on July 9 and damage it . Park crews had to close and repair the 3.3-mile loop road that takes visitors past White Dome Geyser , Great Fountain Geyser and Firehole Lake . Blame it on the Yellowstone Volcano . Yellowstone National Park -- a UNESCO World Heritage Site -- sits atop one of the world 's largest volcanoes , and some of the thermal spots have damaged the popular Firehole Lake Drive . The park features over 10,000 thermal spots , about half the world 's known thermal spots . Yellowstone : One of the first UNESCO World Heritage Sites . Although the volcano is active -- evidenced by the thermal features and 1,000 to 3,000 earthquakes annually -- park officials do n't expect a catastrophic eruption anytime in the next 1,000 or even 10,000 years . Yellowstone 's first supervolcanic eruption occurred 2.1 million years ago , and there were other Yellowstone supereruptions 1.3 million and 640,000 years ago . The park has instruments monitoring the volcano throughout the park , and there would be plenty of warning -- weeks or even months -- if an eruption were going to occur . In the meantime , enjoy the park ! Maintenance crews quickly repaired the road , and it was reopened to visitors Saturday . Summer in the park at Yellowstone .
It sits on top of one of the world 's largest mountains . Extreme heat from the volcano 's thermal areas damaged the popular road . No volcanic eruption is recorded for 1,000 years or more .