The
Amazon is the greatest river in the world by so many measures; the
volume of water it carries to the sea (approximately 20% of all the
freshwater discharge into the oceans), the area of land that drains into
it, and its length and width. It is one of the longest rivers in the
world and, depending upon who you talk to, is anywhere between
6,259km/3,903mi and 6,712km/4,195mi long.
For
the last century the length of the Amazon and the Nile Rivers have been
in a tight battle for title of world's longest river. The exact length
of the two rivers varies over time and reputable sources disagree as to
their actual length. The Nile River in Africa is reported to be anywhere
from at 5,499km/3,437mi to 6,690km/4,180mi long. But there is no
question as to which of the two great rivers carries the greater volume
of water - the Amazon River.
At
its widest point the Amazon River can be 11km/6.8 mi wide during the
dry season. The area covered by the Amazon River and its tributaries
more than triples over the course of a year. In an average dry season
110,000 square km of land are water-covered, while in the wet season the
flooded area of the Amazon Basin rises to 350,000 square km. When the
flood plains and the Amazon River Basin flood during the rainy season
the Amazon River can be up to 40km/24.8 mi wide. Where the Amazon opens
at its estuary the river is over 325km/202 mi wide!
Because
the Amazon drains the entire Northern half of the South American
continent (approx. 40% landmass), including all the torrential tropical
rains that deluge the rainforests, it carries an enormous amount of
water. The mouth of the Amazon River, where it meets the sea, is so wide
and deep that ocean-going ships have navigated its waters and traveled
as far inland as two-thirds the way up the entire length of the river.
So,
how did the Amazon get to be so big? The first reason has to do with
its location - right at the equator. Around the "belt line" of the earth
lies a warm, tropical zone where over 400 in/1016cm of rain fall every
year. That averages out to more than an inch (3cm) of rain, everyday! A
lot of water falls onto the land surrounding the river, what is called
the "Amazon River drainage basin". A good way to understand what a
drainage basin is to think of the whole northern half of the continent
of South America as a shallow dish, or saucer. Whenever rain falls and
lands anywhere in the river basin it all runs into the lowest place in
the pan, which happens to be the Amazon River. The sheer volume of rain
in the Amazon jungle, as well as the slope of the surrounding land,
combine to create the enormous river known as the Amazon.
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