10 of the tributaries flowing into the Amazon river are as big as the Mississippi river.
41
It takes a drop of ocean water more than 1,000 years to circulate around the world.
61
More than a dozen men have stood on the surface of the moon, but only three have been to Challenger Deep in the Marianas Trench, the deepest known spot in the ocean.
17
The average ice berg weighs 20,000,000 tons!
54
An earthquake on Dec. 16, 1811 caused parts of the Mississippi River to flow backwards.
243
The Niagara Falls moves upstream at an average rate of about 295ft a century!
48