(nautil.us) – We are in the 21st century, have been to the moon, landed a robot on Mars and still, the ocean floor is basically a blank slate. Most of the mapping of the ocean has been done by satellites. The world’s largest geographic feature is an underwater mountain range that runs 40,000 miles and the Mariana Trench is 7 miles deep, taller than Mt. Everest. The largest waterfall is not on Earth but below on the seafloor between Greenland and Iceland. There is now an effort to map more of the ocean. You can learn more at seabed2030.org. Read more here.