NASA is keeping a close eye on a 70-mile-long rift in an Antarctica ice shelf that could produce a massive iceberg and indirectly lead to rising sea levels.

The crack in the Larsen C Ice Shelf is more than 300 feet wide and about a third of mile deep, according to the agency. Once the crack goes all the way across, it could produce an iceberg the size of Delaware.

Ice shelves are permanent floating sheets of ice that connect to a landmass, according to the National Snow and Ice Data Center.

Most of the world's ice shelves hug the coast of Antarctica. The Larsen C shelf is on the Antarctic Peninsula, the portion of the continent that juts out toward South America.