Is the Amazon the World's Largest River?

Everyone knows that the Amazon River is one of Earth's most astonishing wonders, but were you aware that it has an underground counterpart? In 2011, scientists discovered something incredible well below the Amazon: an aquifer (an underground layer of water-bearing permeable rock) of nearly equal length and roughly double the Amazon's width that has unofficially been called the Hamza River. The researchers discovered the aquifer after examining data from hundreds of oil wells dug along the river several decades ago. Based on thermal readouts, the scientists believe the Hamza -- which runs west to east -- mostly lies 13,000 feet (3,962 m) under the surface. While the find is startling and impressive, the Hamza can't compare in many ways to its above-ground partner. Only about 1 million gallons (3,900 cubic meters) of water rush through it per second, compared with 35 million gallons (133,000 cubic meters) for the Amazon. It's also considerably slower: It can take a full year for the water in the Hamza to travel 330 feet (100.5 m), while the Amazon flows that far in an hour.

For the record, although the Amazon is the largest river in the world by discharge volume of water, it is generally considered to be the second-longest, after the Nile.

All about the Amazon:

• Although Brazil contains 60 percent of the Amazon, the river's source is believed to be in the Andes Mountains of Peru.
• The Amazon River supplies 20 percent of the fresh water that flows into the world's oceans.
• The mouth of the Amazon River is more than 200 miles (320 km) wide.