Geological provinces of the near side of the moon

Systematic geologic mapping of the near side of the Moon has provided the basis for defining and delineating the major geological provinces of the near side. From the nature of the provinces and their distribution patterns a general historical sequence evolves. Five main surface-shaping periods are recognized: (1) one of intense early impact cratering; (2) another, probably overlapping the first, during which the impact basins were formed; (3) a prolonged period of varied terra volcanism; (4) a short period of mare volcanism that resulted in filling of the multiring basins; and (5) a period of diminishing volcanic activity continuing up to the time of formation of the last ray craters.