Recently, Wisconsin geologists, both amateurs and professionals, calling themselves crater hunters, have been examining the evidence of craters of meteorite explosions upon earth's surface which was prevalent over other areas in North America back when Wisconsin and western Russia once shared the space south of the equator. It has been estimated that the rate of falling meteors were up to 100 times more than the rate today and with falling space rocks the size of a football field, hitting the planet every 10,000 years. The ancient bombardment occurred during the Ordovician Period.
Earth's geological history in terms of continental drift stretches out over a thousand million years with marked results in 500 million year intervals. Maps that depict these ages and drifts are an estimation. Each 500 million year interval was followed by about 100 million years of geological episodes called rifting as continents broke apart due to erosion and other natural phenomenon.