Geologists find evidence of at least six of these major breaks in the earth crust,-marking the beginnings of the Archeozoic Era, when life originated, the proterozoic Era, or age of invertebrates, the Paleozoic Era or age of fish dominance, the Mesozoic Era or age of reptile dominance, the Cenozoic Era or age of mammal dominance, and the present Psychozoic Era or age of man.
"Unexplored!"
Allen Chaffee
In the proterozoic, there are two periods, viz.
"The-Grand-Canyon-of-Arizona-how-to-see-it"
James, George Wharton