sahara desert -science piolo

8/9/2019 Sahara Desert -Science Piolo

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The Sahara is the biggest desert in the world

Its parched, forbidding landscape took shape over thousands of years, but even today,the Sahara is constantlychanging.

Why is this desert soimportant to Africans? Howdo people survive its harsh,dry climate? And is theSahara getting bigger, orsmaller?

y studying satellite photos,some scientists have cometo believe that the Sahararegularly shrinks and grows.

In the early !"#$s, theSahara%s southern edgee&panded into the Sahel, adry band that separates thedesert from the savanna. ut by the mid'!"#$s this area was green and wet again.

(he Sahara receives less than three inches of rain a year) *hicago%s annual precipitation,its combined rainfall, snow and sleet, is ++.+ inches -#.# cm/. 0ven in the Sahara%swettest areas, it may rain twice one week and not rain again for years.

1or centuries caravaneers have traveled through the Sahara desert. 0ven though there

are many oases in the Sahara, the desert is so immense that travelers may go for daysto reach them.

2ases make trade possible between the ports of 3orth Africa and savanna marketsfurther south. Without these wet rest stops for humans and animals, crossing the desertwould be almost impossible.

As the world%s biggest desert, the Sahara covers a third of the African continent'an areaabout the si4e of the 5nited States.

(he Sahara6 1acts, *limate and Animals of the 7esert


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8im Ann 9immermann, :iveScience *ontributor ; September !


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Climate and geography of the Sahara

(he Sahara>s northeasterly winds can reach hurricane level and often give rise to sandstorms and dust devils. Half of the Sahara receives less than an inch of rain per year, andthe rest receives up to inches -!$ centimeters/ per year. (he infreuent rain is usuallytorrential.

(he highest peak in the Sahara is the volcano 0mi 8oussi -!!,s other mountains and mountainranges include the AFr Bountains, Hoggar -Ahaggar/ Bountains, Saharan Atlas, (ibestiBountains, Adrar des Iforas and the Ced Sea hills.

(he Hoggar Bountains in Algeria are in the central Sahara.*redit6 Gichugin 7mitry; ShutterStock

Bany people imagine the Sahara as dotted with sand dunes, and the desert does haveits share of ergs, which are large areas of shifting sand dunes, with some of some ofthem reaching ="$ feet -!#$ meters/. However, most of the Sahara is characteri4ed asrocky hamada, a type of desert landscape that has very little sand and is made up of

primarily barren, hard, rocky plateaus.

With the e&ception of the 3ile Civer, the Sahara>s rivers and streams are irregular orseasonal. (he 3ile crosses the desert from its origins in central Africa to empty into theBediterranean.

(he central part of the Sahara has e&tremely limited vegetation. (he northern andsouthern reaches of the desert, along with the highlands, have areas of sparse grasslandand desert shrub, with trees and taller shrubs.
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(he Adda& nasomaculatus, also known as the screwhorn antelope, is the Sahara%s largest indigenousmammal

Animals of the Sahara

(housands of years ago, the Sahara had enough water so that people and animals were

able to survive on the edge of the desert. (here is evidence that the area was able tosustain river animals such as crocodiles. 1ossils of dinosaurs, including Afrovenatorobaria and 2uranosaurus, have also been discovered in the desert.

Grehistoric rock paintingsalso depict cattle, giraes, elephants and lions that roamed aonce'lush Sahara.

(oday, there is little water or vegetation to sustain life in most part of the Sahara. Somee&ceptions include the 3ile Jalley, a few oases, and the northern highlands, whereBediterranean plants such as the olive tree are found to grow. (he change occurred inabout !$$ .*., after shifts in the 0arth%s a&is increased temperatures and decreased

precipitation.

*amels, most often associated with the Sahara, were introduced to the desert around


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Codents, snakes and scorpions thrive in the desert environment. (he desert is home tothe deathstalker scorpion, which can be nearly inches -!$ cm/ in length. Its dangerousvenom contains large amounts of agito&in and scyllato&in.

Among the $'plus species of rodents in the Sahara is the Eerboa, related to the mouse,rat and suirrel. (o keep cool, the Eerboa burrows underneath the desert%s sands to morehumid soils.

(heAddax nasomaculatus, also known as the screwhorn antelope, is the Sahara%s largestindigenous mammal. It travels in small herds throughout the Western Sahara, Bauritaniaand *had. Instead of drinking water, it sucks moisture from the desert grasses andbushes. Its oversi4ed hooves make the adda& adept at moving through the Sahara%sloose sand.

ackals and several types of hyenas are among the carnivores that roam the Sahara.Weighing less than + pounds -!. kg/, the Ball 1ennec 1o& is another carnivore thatmakes its home in tunnels in the sand dunes during the day and comes out at night toprey on the rodents.

Kim Ann Zimmermann

(he Sahara6 1acts, *limate and Animals of the 7esert8im Ann 9immermann, :iveScience *ontributor ; September !


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who had small villages and farmed the land. (here were forests and grasslands in theSahara.

(hen, about ,$$$ years ago, the climate began to change. Within a few centuries, theSahara became the desert that it is today. Why? Scientists think that conditions in theatmosphere changed so that the Sahara got warmer and drier. As the climate changed,fewer and fewer plants grew there, and the people had to move to places where therewas more water.

Satellite images help people make other discoveries in the Sahara. With these pictures,archaeologists can Pnd where ancient people had their settlements. GaleontologistsNscientists who study fossils to learn about prehistoric lifeNuse satellite images to helpthem Pnd the best places to search for clues to life millions of years ago.

What makes the Sahara a desert?

(he Sahara is one of the hottest places on 0arth. 0ven though temperatures there mayrise to !+ 1 -=K.K */, its dryness, not heat, that makes a place like the Sahara a desert.(he fro4en continent of Antarctica is so dry that some scientists consider it a desert, too.

As the world%s largest desert, the Sahara receives less than three inches -K. cm/ of raina year. 0ven in its wettest areas, rain may arrive twice in one week, then not return foryears.

sahara desert -science piolo

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