A basic geologic principle. Processes that act upon the Earth today are the same processes that have acted upon it in the past. The present is the key to the past. Classically, the concept that the present is the key to the past; the principle that contemporary geologic processes have occurred in the same regular manner and with essentially the same intensity throughout geologic time, and that events of the geologic past can be explained by phenomena observable today. Also known as actualism; principle of uniformity.
No related terms.