SPENCER SUTTON / SCIENCE PHOTO LIBRARY SPENCER SUTTON / SCIENCE PHOTO LIBRARY
Illustration of the sequence of events as an impact crater forms. At top (excavation stage), the impactor (bolide), such as an asteroid, hits the surface, losing a lot of its kinetic energy. This lost kinetic energy heats and vaporizes the bolide and the rocks at the surface (end excavation stage) Some of the kinetic energy is dissipated as sound and light, and some is transferred to the surface, deforming it and throwing rock upwards and outwards (modification stage) as the blast wave widens the crater and forms the crater walls. The blast ejecta forms a blanket around the crater, with the rock layers (strata) reversed. This strata reversal is shown in the diagram at bottom (final crater), where the energy of impact has dissipated and the ground at the point of impact has rebounded, leaving a central peak.
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