As they examined possible fixes, park officials warned visitors not to hike into the affected area, where the danger of stepping through solid-looking soil into boiling-hot water was high.
"There are plenty of other great places to see thermal features in the park," Yellowstone spokesman Al Nash said. "I wouldn't risk personal injury to see these during this temporary closure."
However, the damage to Firehole Lake Drive is unusually severe and could take several days to fix. The 3.3-mile loop six miles north of Old Faithful takes visitors past Great Fountain Geyser, White Dome Geyser and Firehole Lake.
Unusually warm weather for Yellowstone — with high temperatures in the mid-80s — has contributed to turning the road into a hot, sticky mess.
"We've got some ideas. We're going to try them. Our maintenance staff has really looked at the issue," Nash said.