Timeline of the geologic history of the United States

Time line chart.
This time line of the geologic history of the United States chronologically lists important events occurring within the present political boundaries of United States (including territories) before 12,000 years ago. This time line segment may include some events that occurred outside these borders that profoundly influenced later American life and its present landscape. It also includes evidence of Native American communities predating the Clovis culture.
Because of the inaccuracies inherent in radiocarbon dating and other methods of interpreting the geologic (and archaeological) record, most dates in this time line represent approximations that may vary considerably from source to source. The assumptions implicit in geologic dating methods also may yield a general bias in the dating in this time line.