Scientists believe that they have discovered the longest canyon on Earth to date. It is estimated to be around 750 km (450 miles) long. It’s not a very easy canyon to visit as it sits under Greenland’s ice sheet. About 80% of Greenland is covered with ice, and the ice in places is as thick as 3 km (2 miles). The canyon is believed to have been carved out by a river that flowed in the area over 4 million years ago, before all the ice showed up. Greenland is not a country – it has been a part of Denmark for about 300 years. You can watch a video about the canyon here.
Image Credits: nasa.gov for Greenland’s canyon images
Sources: http://www.bristol.ac.uk, http://svs.gsfc.nasa.gov