Several other relatively small craters were also found to contain impactor fragments; for many years, these remnants were the only accepted evidence for impact origin.
On the Earth , however, which has been even more heavily impacted than the Moon, craters are continually erased by erosion and redeposition as well as by volcanic resurfacing and tectonic activity. Thus only about 120 terrestrial impact craters have been recognized, the majority in geologically stable cratons of North America, Europe and Australia where most exploration has taken place.