The floor of a continental sabkha is usually a hard-packed combination of sand, mud and salt. It is easy to walk or drive 4x4 vehicles across the dry, continental sabkha. However, after rains and flash-floods, the continental sabkha fill with shallow layers of water, and cannot be crossed until they dry out to form a new crust. When the ground is partly dried, a salt crust forms over soft mud or hollow cavities, and a vehicle will become stuck after breaking through the crust.