system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is the sand in the Sahara desert not like regular soil, and where does it come from?
gpt
Because no sand is like regular soil. Soil is from the decomposing of biological matter. Sand is from the erosion of stone, and the breakdown of corral by angel fish and other corral eaters. 

The Sand in the Sahara come from when it was the bottom of a shallow sea, and the wind erosion of rock outcroppings.