Ever been mesmerized by the swirling colors of Grand Prismatic Spring and wondered what fuels that otherworldly boil? It turns out that beneath the wild expanse of Yellowstone National Park lies one of the most closely watched volcanic systems on Earth.

Scientists at Yellowstone National Park have uncovered a large, underground magma cap that is likely crucial to containing one of Earth's largest volcanic systems. Hidden 2.4 miles (3.8km) beneath Yellowstone's northeast caldera, the cap acts as a lid for the intense heat and pressure below it, which could otherwise cause large-scale eruptions.