A new study shows a volcanic eruption of Yellowstone may be even less likely than we thought: Scientists have discovered a magma cap that may play a role in relieving volcanic pressure underground.

A "breathing" cap of magma has been discovered by scientists just 4km under Yellowstone National Park. Yellowstone National Park is known to sit on a huge lake of active magma, which causes steaming geysers, hot springs and boiling mud pots.

A recent study discovered the exact location of the Yellowstone supervolcano's magma cap -- and hints at when it may erupt.