Where did all the sand come from in the Sahara desert ?

Question

Must have been one h*ll of a beach !

Answer 1

The sand is primarily derived from weathering of Cretaceous sandstones in North Africa. When these sandstones were deposited in the Cretaceous, the area where they are now was a shallow sea. The original source of the sand was the large mountain ranges that still exist in the central part of the Sahara. These mountains are volcanic and intrusive, and the granite rock weathers out to leave behind quartz sand grains that are carried by rivers to the sea. These sand deposits eventually formed into sandstone, and as they were uplifted began to weather and break down into sand again.

Only about 10% of the Sahara is actually covered by sand, and parts of the Sahara are in fact covered by soil. More than half of the area comprises soils known as yermosols, with shallow profiles over gravel or pebble beds. These soils have been developing over the past 50 million years.
http://www.worldwildlife.org/wildworld/profiles/terrestrial/pa/pa1327_full.html
http://www.1911encyclopedia.org/Sahara

Recent work using remote sensing radar has revealed ancient river beds under the sands of the Sahara.
http://www.agu.org/sci_soc/evans.html

Pollen records indicate that the Sahara was covered by savanna and steppe vegetation as recently as 5,500 years ago.
http://www.ncdc.noaa.gov/paleo/abrupt/story4.html

Answer 2

This is the true answer. Sand is rock that has been eroded to the point that is is small. Sand in reality is many very small rocks. The Sahara Desert was at one point, underwater. The whole thing didn'e emerge at once. It was a beach that simply followed the shore as the water moved away. This made it very large. Note that just because there is lots of sand, that doesn't necessarily make something a Desert. The Sahara is a Desert because of how little rain there is. Little Rain means little vegetation, and little vegetation means that there is nothing left to hold the soil in place, and so the sand takes over. It is for this reason that the Sahara is still growing. (See source)

Answer 3

Deserts have characteristic low rainfall and arid environments. There is also more windy conditions in these arid environments. This combination results in wind blown erosion which breaks down rocks into sand, and additionally, heavy evaporation also creates more rigid conditions making erosion more rapid and consistent. The Sahara receives less than 10 inches a year in rain fall. That is what produces the sand in the Sahara. This isn't a complete answer, but if your really interested, check out a geology textbook and search the net and take a college class in geology.

Answer 4

The reason the Sahara is a desert is because of the cold water around it brought in by the oceanic conveyer. The cold sea immediately north of the Sahara condenses rain clouds and moisture before they can reach Africa; that is why the region turned into dry desert and receives such little rainfall.
The cold ocean also causes the temperature to drop dramatically in the night. So the Sahara experiences scorching heat during the day and bitter cold during the night. This constant heating and cooling caused all the rocks and minerals in the area to expand in the heat of the day and suddenly cool and contract in the night. Over hundreds of years the expanding and contracting rocks fractured into powdery sand. (This expanding contracting effect is the reason ceramic and glass ware crack if you put it in the refrigerator with very hot food in them.)

Since we are on the subject of deserts; the glass roses found in the desert are caused by lightning striking the sand. Rare as it maybe thunder clouds do form occasionally in the desert.

Answer 5

As water erodes rock from high to low, the rock gets crushed into particles. These particals are sorted into very fine powder which gets washed away very easily, to bolders which can only be moved by big floods. The sand is just small enough to get picked up by the wind. Becuase it is made of silica it is very stable and hard. The sand in the Sahara genearlly may be created by the rivers, washed to the Atlantic Ocean, then washed up onto the beaches to be blown onto the land. Finer grains will be blown into dust, heavier grains cannot be moved by air, and thus only those grains that are just in the right size range get blown into Sahara dunes.

Answer 6

Sand is silicone dioxide, so it is not the fossilized remains of organic matter. It is rock hardened from molten interior core materials that rose up through cracks in the earth's crust. It originally became solid rock. Sand is formed when the waves of the ocean pound rocks together for millions of years, pulverizing them to bits. The reason there is sand in the Sahara is that that part of Africa was once covered by ocean.

Answer 7

The most natural and healthy diet for humans is an omnivorous diet, and not a plant based diet, or a meat-based diet per se. The Paleo Diet can be very widely varied and omnivorous for the most part, but the most important thing is that it’s unprocessed, and avoids the worst foods that agriculture brought mankind… refined inflammatory vegetable oils, refined grains (some are worse than others), and sugar! Learn here https://tr.im/XlXVC

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Answer 8

Sahara has been a fertile land in the past. The sand is what remains from the soil after it has been eroded for a long time because of natural climate changes.

Answer 9

Also it is what´s left after the lighter soils, with organic humus components, and the fine clayparticles have been blown away by the winds. With no humidity or vegetation to bind the soil a desert is an easy prey for winderosion.

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Answer 10

Sand is the end product of the process of erosion of mountains and land forms. Mountains are formed by uplift of the earth's upper mantle, and as soon as they form, they are subject to erosion by wind, water, ice and chemical reaction. It starts off as chunks and boulders falling from the mountain, carried down stream in fast flowing water from a spring melt, eventually into a river carving out canyons etc. All of this levels the land over millions of years. The sediment is gradually broken down into finer and finer particles from boulders to silt over millenia to form sand. In a desert situation, it is a combination of erosion of both surrounding landforms, climate change and erosion of soil.
The sahara desert is blown west into the atlantic, providing nutrients for ocean life and sand for the eastern seaboard of USA, bringing with it microorganisms etc.