Question

most of the land surface in a desert is Sandy why ?

Answer 1

Nearly all sand in deserts came from somewhere else – sometimes hundreds of kilometers away. This sand was washed in by rivers or streams 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.

Answer 2

it's due to intense heat and lack of water