Scientists have discovered ancient microorganisms thriving in Yellowstone National Park’s harshest environments ... s acidic hot springs. These archaea, believed to be some of the oldest ...

Editor’s Note: This story accompanies the May 2016 issue of National Geographic magazine, devoted entirely to America’s first national park. Find more at natgeo ...

"Sinkholes are most common in what geologists call, 'karst terrain'," the US Geological Survey explains. "These are regions ...