Impact Crater Formation, Shock Metamorphism, and Distribution of Impact Ejecta
As previously mentioned, an integral part of the cratering process is the formation and widespread distribution of ejecta. In order to comprehend how the distribution, thickness, and nature of an impact ejecta layer varies with distance from its source crater, one needs to understand the cratering process. Thus, we begin this chapter with a brief review of cratering mechanics. This leads into a discussion of shock metamorphism, which occurs during the cratering process and which is important in the identification of impact craters and distal ejecta layers. At the end of the chapter we briefly discuss some theoretical and experimental data on how ejecta, including the degree of shock metamorphism of the ejecta, vary with distance from the source crater. This last subject is addressed again in Chap. 10, but in Chap. 10 we compare observations on how distal ejecta vary with distance from source craters with theoretical and experimental data of how the thickness and nature of distal ejecta should vary with distance from the source crater.