Why is there sand in the deserts and whats underneath ?

[Larry the boss]

[Zaroku]

Buried Dino’s and oil!

Maybe secret burial chambers for Pharos?

[OldTerry]

Using my copy and paste skills I have answers - sand was washed in by rivers or ******s in distant, less arid times – often before the area became a desert. Once a region becomes arid, there’s no vegetation or water to hold the soil down. Then the wind takes over and blows away the finer particles of clay and dried organic matter. What’s left is desert sand.

Whats under the desert? - The desert extends downward until which time it encounters an underwater body of water of molten rock. This encounter happens at varying depths.

I do know that the desert is a good place to find a meal, due to the sandwhiches there.