We will begin by exploring the Pre-Archaean, Archaean, Proterozoic and Phanerozoic, which are major divisions of the Geologic Time Scale.
Click on each of the highlighted divisions to find out more.
These three periods of time are referred to as Erasthe Paleozoic, the Mesozoic, and the Cenozoic.
Click on each of them to find out more.
Cenozoic means "recent life." Mammals, birds, flowering plants,
and the ray-finned fishes all became more abundant during this time. |
Mesozoic means "middle life." Dinosaurs, cycads, and ferns
were abundant during the Mesozoic. |
Paleozoic means "ancient life." Many animals of today originated
then (during the Cambrian), like certain corals and brachiopods. Some, like relatives of the sponge and trilobites
originated then, but later went extinct. |
Proterozoic means "before animal life" which is actually not
accurate, but most of the organisms were pretty simple. In addition to
bacteria, we find things like algae and unusual worm-like creatures. |
Archean means original or ancient. This is a time when the first single-celled organisms, like bacteria, began to evolve. |
Pre-Archean refers to the time before the Archean. There is
no evidence for life at that time. |
The Phanerozoic Eon encompasses the period of abundant, complex life on Earth. It began with the start of the Cambrian period, 544 million years ago, when most of the major groups of animals first appear in the fossil record, and continues through today. |