Scientists mapping the seafloor in the Arctic have made a startling discovery. Giant sinkholes.
Some of the sinkholes are larger than a city block.
The sinkholes are developing due to melting permafrost that has been submerged underneath the seabed.
These changes have occurred in less than a decade.
What is permafrost?
Permafrost is ground that continuously remains below freezing and can be located on land or under the ocean.