Cynthia P. Dimalanta, age 11, of San Diego, Calif., for her question:

How long is the Amazon River?

The world has three great rivers, which are of almost equal length the Nile, the Mississippi Missouri and the Amazon. Although the African Nile is a few miles longer, the volume of its waters cannot be compared with the Amazon. This great South American River carries far more water than the other two combined.

The Amazon's source flows from the icy waters of glacial lakes high in the western Andes Mountains. It flows Eastward, crossing South America at almost its widest point. Along the way it gathers countless streams and rivers flowing from the north and south. After a journey of 3,900 miles, the mighty Amazon empties into the Atlantic Ocean at the Equator.