The geology of astroblemes

The geological structures of all the astroblemes known to exist in the USSR as of 1978 are described. The composition of various breccias and impactites is analyzed, and data on the metamorphism of rocks and minerals brought about by the impacts are presented. The structures of objects assumed to be of cosmic origin are briefly considered. A survey of geological data on the most thoroughly studied astroblemes in other countries is included. The mechanism governing the formation of impact craters is considered on the basis of an analysis of astrobleme structure and the type of rock found inside the astroblems. The morphology and internal structure of impact craters are shown to be dependent on the geological conditions obtaining in the area of crater formation.