Only 182 impacts have been ‘confirmed’ on the earth. This number may be very low for two reasons. First, numerous impact craters are observed on the moon and other inner solar system bodies. Second, terrestrial impacts have been significantly modified by erosion and the emplacement of lava flows and thick sedimentary cover. The large Vredefort and Sudbury impact structures illustrate the extent of this alteration. Based on this evidence, other impact features may be difficult to identify. Other factors hindering the confirmation of past impacts, especially in the Precambrian, include overly stringent requirements for impacts, thick Phanerozoic cover, and the fact that until recent decades few geologists have been looking for impacts. Indirect evidence for other impacts, especially during the Precambrian, include cratonic basins, other circular or arc-shaped features, impact spherule layers, and other subtle geological and geochemical features. Thousands of impacts may have occurred during the Precambrian. It is likely that many Precambrian sedimentary rocks are Flood deposits, such as black shale, quartz arenite, phosphate-rich rocks, or those with diagnostic fossil traces, such as raindrop imprints. This suggests that many Precambrian impacts occurred during the Flood. These may have contributed to the energy needed to start and sustain the Genesis Flood.
Some creation scientists believe Precambrian sedimentary rocks are from the Flood, while others believe they are pre-Flood. The latter group also believes that the pre-Flood/ Flood boundary is at or slightly below the Precambrian/Cambrian boundary1,2 (assuming the geological column for sake of discussion). If the Precambrian is pre-Flood, where does it fit into biblical Earth history? The pre-Flood world is commonly seen as a generally benign geological period,3which I agree with. So, the Precambrian is believed to be mostly a record of Creation Week.3,4
I have previously argued for a large number of unidentified terrestrial impacts, based on the size/frequency diagram of moon craters as well as other inner solar system bodies that have not been resurfaced. Based on that analysis, more than 36,000 impacts producing craters greater than 30 km (some very large) could have struck Earth during its history.5 Spencer updated this number to 58,000 based on newer data from the Lunar Reconnaissance Orbiter, and discussed that a crater-size cutoff of 30 km would eliminate most secondary craters caused by ejecta from large impacts.6 These data suggest that the solar system intersected a homogenous distribution of impactors in the past, assuming all impacts occurred about the same time.
Continue reading at CMI