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.
Glaciers erode the land by plucking and abrasion.
<span>The historic name given to the region known as the Levant was canaan</span>
The New York State bedrock contained salt, gypsum and hematite during the Silurian age. The Silurian age started around 443.8 million years ago. The bedrock gives scientists a clear indication of when each age started and ended. The Silurian age is also an important period in the evolution of life on the earth. During this age, life began to appear on the land in the form of small, moss-like, vascular plants. They started growing next to lakes, coastlines and streams. Small terrestrial arthropods also starting appearing during the Silurian age.
<span>
</span><span>
</span>