What is the Archean Eon?
The Archean Eon is the second geologic eon in the Earth’s history, beginning at the end of the Hadean Eon 3800 million years ago (mya) and extending to the start of the Proterozoic Eon 2500 mya. Unlike more recent eons when life was abundant, the Archean is defined by arbitrary date limits rather than the presence or absence of certain fossils. It would be safe to say that the Archean eon was a very long time ago, as is reflected in its name, which means old. The origin of life happened sometime in the early Archean, approximately 3.5 billion years ago. This is corroborated by fossil evidence in the form of stromalites, the remnants of simple microorganisms which created thick layers of biotic muck as they died. The Archean begins shortly after a drawn-out series of events called the Late Heavy Bombardment, during which pieces of solar debris which had not yet formed into planets were getting drawn into the gravity well that is the Earth. Some biologists believe that this bombardment w
