Geography Reference
In-Depth Information
Hemisphere's winter—but now it is summer in the Southern Hemisphere. Because of this tilt away from
the sun, the North Pole or Arctic is plunged into near darkness while Antarctica enjoys near total day-
light—or the midnight sun. Of course, the situation then reverses itself, season after season, year in year
out.
What's So Hot About the Equator?
This is fairly simple. The equator is the one place on earth where the sun's rays are unaffected by the tilt
of the earth. The equator is always exposed to the sun and receives direct solar rays year-round in spite of
the season.
This means air at the equator is warmed more than at the poles. The equatorial air is warm and moist.
That's why you find rain forests in the equatorial regions.
So how can there be snow at the equator? Simply because the weather stew is also affected by altitude.
Although it is hot at sea level at the equator, it can get very cold as you move up into mountains. Some
equatorial mountains, such as Mount Kilimanjaro in East Africa and the Andean peaks in Ecuador, are
snow-covered year-round.
If the Equator Is So Hot, Why Are There No Deserts on the Equator?
So the equator gets the most sunshine. That means it should have the most deserts, right?
Many people hear the word
desert
and picture an old movie about the French Foreign Legion. A soldier
in tattered khakis, lips cracked and parched, drags himself slowly through the dunes, croaking “Water.” Or
we conjure up cartoons of people stuck in the desert, envisioning unlikely mirages of soda fountains and
waterfalls.
While most of us might equate the word “desert” with “hot,” that isn't an accurate association. Tech-
nically speaking, a desert is an almost barren tract of land in which rain or other forms of precipitation
are so scanty or irregular that most vegetation won't grow, except for extremely poor grass and low brush.
Specifically, a desert is an area that receives less than ten inches of precipitation a year. In other words,
deserts may not be hot, but they are dry.
Although there are low-lying “desert” islands along the equator where rain-bearing winds simply pass
over, the major desert zones lie in two belts on either side of the equator. The warm, moist equatorial air
that keeps the rain forests wet, flows toward the poles. As the air rises, it cools and dries. By the time it
reaches the latitude of 30˚—both north or south of the equator—this cool, dry air begins to sink, warm up,
and flow back toward the equator. These dry cells of air are responsible for the belts of desert and arid land
found around the Tropics of Cancer and Capricorn.
The world's deserts can be divided into subtropical deserts—such as the Sahara and Arabian
deserts—and mid-latitude deserts such as the Gobi in Mongolia. Less familiar is the notion of a
cold desert
where water is unavailable because it is trapped in the form of ice. This means that the snowy vistas of
Antarctica and Greenland actually qualify as deserts.
Whether too cold or too hot, high in the mountains or below sea level, sandy or rocky, all deserts are
linked by conditions highly unwelcome to life. Aridity and extreme climates make farming and raising
animals all but impossible except with sophisticated irrigation systems. Sparsely populated and seemingly
