There’s a new milky blue pool in Yellowstone National Park.

Yellowstone National Park closed the Madison River, the Firehole River and the Gibbon River downstream of Norris Campground, as well as those rivers' tributaries, on July 12. Fishing draws about 50,000 visitors to Yellowstone each year, according to the park's website.

"The discovery emphasizes the dynamic nature of Yellowstone's thermal activity," Yellowstone Volcano Observatory's Mike Poland said.