Fossil records have taught us much about the past. Geologists have organized the Earth’s history into geologic time intervals (stages). These intervals of time are called “ERAS”
These eras are based on the strata’s of rock (oldest rock on the bottom and youngest on top)
4 Major Divisions 1. Precambrian Era - (4600 - 600 million years ago) Earth forming, first signs of simple life 2. Paleozoic Era - (600 - 225 million years ago) First reptiles, plants, fish with jaws, insects 3. Mesozoic Era - (225 - 60 million years ago) Dinosaurs rule, then die, first flowering plants & mammals, 4. Cenozoic Era - (60 million years ago - current day) Appearance of most modern day species, first grasses 2 - 3 million years ago first appearance of human like species |