Sahara Desert
Read the following passage carefully.
The Sahara sets a standard for dry land. It’s the world’s largest desert. Relative humidity can drop into the low single digits. There are places where it rains only about once a century. There are people who reach the end of their lives without even seeing water come from the sky. Yet beneath the Sahara are vast aquifers of fresh water, enough liquid to fill a small sea. It is fossil water, a treasure laid down in prehistoric times, some of it possibly a million years old. Just 6,000 years ago, the Sahara was a much different place. It was green. Prehistoric rock art in the Sahara shows something surprising: hippopotamuses, which need year-round water. “We don’t have much evidence of a tropical paradise out there, but we had something perfectly livable,” says Jennifer Smith, a geologist at Washington University in St. Louis.
At times when the Northern hemisphere tilts sharply towards the sun and the planet makes its closest approach, the increased blast of sunlight during the North’s summer months can cause the African monsoon (which currently occurs between the Equator and roughly 178 N latitude) to shift to the North as it did 10.000 years ago, inundating North Africa.
Around 5,000 years ago the monsoon shifted dramatically Southward again. The prehistoric inhabitants of the Sahara discovered that their relatively green surroundings were undergoing something worse than a drought (and perhaps they migrated towards the Nile Valley, where Egyptian culture began to flourish at around the same time).
As the land dried out and vegetarian decreased, the soil lost its ability to hold water when it did rain. Fewer clouds formed from evaporation. When it rained, the water washed away and evaporated quickly. There was a kind of runaway drying effect. By 4,000 years ago the Sahara had become what it is today.
No one knows how human-driven climate change may alter the Sahara in the future. It’s something scientists can ponder while sipping bottled fossil water pumped from underground.
“It’s the best water in Egypt,” Giegengack said-clean, refreshing mineral water. If you want to drink something good, try the ancient buried treasure of the Sahara.
1. Answer the following questions.
(a) What is unbelievable about some places in the Sahara?
(b) What does the presence of hippopotamuses in Sahara tell us about the region?
(c) How was North Africa?
(d) Can Sahara ever change?
2. Answer the following questions by choosing the most appropriate option.
A. Remains of plants and animals turned into rock are called:
(i) stone (ii) gems
(iii) anthracite (iv) fossils
B. Scientists who study the layer of the earth are called
(i) geologists (ii) physicists
(iii) astronomers (iv) ornithologists
C. The verb form of ‘evaporation’ is:
(i) evaporate (ii) evaporating
(iii) evaporable (iv) evaporation
D. The noun form of ‘discovered’ is:
(i) discovery (ii) finding
(iii) found (iv) discovering
Answers :
1. (a) Some places in Sahara where it rains only once a century.
(b) That it was green once beneath the Sahara were vast aquifers of fresh water.
(c) An increased blast of sunlight during the summer months caused African monsoon to shift to the North 10,000 years ago.
(d) No one knows but scientists can ponder.
2. (A) (iv) Fossils
(B) (i) Geologists
(C) (i) evaporate
(D) (i) discovery
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