The Amazon rainforest produces more than 20% the world's oxygen supply.
182
The Sahara desert expands at about 1km per month.
90
It takes a drop of ocean water more than 1,000 years to circulate around the world.
61
An earthquake on Dec. 16, 1811 caused parts of the Mississippi River to flow backwards.
243
Australia's Great Barrier Reef is 1,250 miles long!
45
A waterfall known as The Devil's Kettle empties water into a hole and nobody knows where it ends up!
18