Shown is the sequence of events thought to occur in the formation of a simple meteorite crater. The impact of the meteorite striking the ground creates shock waves, which move at a higher velocity than the existing elastic waves in the ground. A spherical shock front in the rocks outruns the penetrating meteorite and forms an expanding cavity. As the pressure behind the shock front rises, the rocks behind are strongly compressed. Depending on the properties of the rocks, segments are vaporized, melted, crushed, fragmented, or fractured. They are ultimately pushed outward and ejected, generally in a radial pattern. The increased density of the compressed rocks behind the shock front lasts until rarefaction, or decompression, waves allow progressive relaxation.