LPREP IBT 3 E AudioScript
45
(Professor)
All of the great rivers of the world have been around much longer than
humanity, but what makes a river really old?
The
Nile River in Africa, which is several hundred million years old, is
believed to be the world’s oldest river. It’s also the longest, at 4,145
miles
in length. As an old river, it doesn’t change drastically in elevation for
most
of its length, and has a meandering path, a slow flow,
and a wide
flood plain.
Now, let’s discuss the young Colorado, which has deep,
narrow valleys
and a very rapid flow. I think you would appreciate the difference if you
sailed down the two rivers. The wide riverboats used on the Nile wouldn’t
make it down the rolling and boiling white water of the Colorado.
Let’s also take a look at the Amazon River in South America. It’s slightly
shorter than the Nile at just over 4,000
miles in length, but it carries more
water than any other river. And, although it is believed to be much
younger than
the Nile in absolute terms, we can observe in the Amazon
many of the characteristics that put it into the same age class.
Again, by identifying another major river by age, the
Columbia River in
the Pacific Northwest—which has the greatest flow of any river in North
America—we can see how,
unlike the Amazon, it still displays its relative
youth as it runs swiftly through high and spectacular mountain gorges.
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