THE EXPLOSION CRATERS OF THE MOON

Abstract

tated the subsidences that gave us the maria and the walled plains, but, with the possible exception of the central part of Mare Imbrium, they did little more. The adjective typical is used because some features which have been referred to as mountain walled differ from the true ones and should have been designated as ringed plains. Arzachel is an excellent example of such an error. It appears to show effects both of major explosion and of subsidence. The walled plains have little or no external walls. Ringed plains have definite ones and primarily are explosive in nature. They are the largest of the explosion craters. For the purposes of this study, any crater that has resulted from any sort of internal force will be spoken of as volcanic, even though some possible impact may have been an indirect cause, as in the cases of the craterlets near Copernicus and Tycho. Most of the data used in this study are shown on the photographic plates