pohjakausi

Pohjakausi refers to the geological period of the Precambrian eon that falls after the Archean and before the Proterozoic. It is a less commonly used term compared to its divisions, the Paleoproterozoic, Mesoproterozoic, and Neoproterozoic eras. The Precambrian itself is the earliest part of Earth's history, spanning from the formation of the planet approximately 4.5 billion years ago up to the beginning of the Cambrian period, about 541 million years ago. The Precambrian is generally divided into the Hadean, Archean, and Proterozoic eons.

The term pohjakausi, if used, would encompass the significant geological events that occurred during this vast stretch of time. This includes the formation of the first continents, the development of early life forms, the Great Oxidation Event, and the assembly and breakup of supercontinents like Rodinia. The precise boundaries and subdivisions of the Precambrian can vary slightly depending on the geological timescale being used, but the general progression of events remains consistent. Understanding this ancient history is crucial for comprehending the long-term evolution of Earth's crust, atmosphere, and biosphere.