A team of scientists this week announced the discovery of a massive canyon that has been hidden underneath Greenland‘s ice sheet for millions of years. The canyon is longer (460 miles) than the Grand Canyon and is nearly 2,600 feet deep in some places. The discovery has been outlined in the latest issue of the journal Science.

“One might assume that the landscape of the Earth has been fully explored and mapped,” said Jonathan Bamber, lead author of the paper and a professor of physical geography at the University of Bristol. “Our research shows there’s still a lot left to discover.”

Bamber and his colleagues collected decades worth of radar data to map the surface of Greenland, which is covered under an ice sheet a mile thick. Much of the data was collected by NASA‘s IceBridge project, an airborne which was able to use a depth sounder to measure the thickness of Greenland’s ice.

The canyon extends from the middle of Greenland to the fjords at the island’s northern edge. Bamber and his colleagues believe the canyon could help to usher sub-glacial meltwater from Greenland’s interior to the coast.

“It is quite remarkable that a channel the size of the Grand Canyon is discovered in the 21st century below the Greenland ice sheet,” said Michael, an IceBridge project scientist at NASA’s Goddard Space Flight Center. “It shows how little we still know about the bedrock below large continental ice sheets.”

(Image courtesy NASA)