Wind, fossils and canyons

Moving air is a strong force of erosion, especially in a desert where there are few plants to hold the soil. Wind picks up sand and carries it along. When flying sand hits a rock, it wears the rock down like sandpaper and carves strange shapes. In Egypt’s White Desert, wind and sand have carved tall chalk rocks into odd forms. Wind also builds. Dunes are hills of sand piled up by the wind, and they are usually found in groups. Grains bounce up the side that faces the wind, tumble over the top and roll down the other side, so the whole dune creeps forward. Dunes form where the wind slows down or meets an obstacle and drops its sand. This is why they are always changing. The Western Desert of Egypt has huge fields of dunes.