The document describes the major geologic eras of Earth's history, including the Precambrian, Paleozoic, Mesozoic, and Cenozoic eras. It notes the types of life, landforms, and any major extinction events that occurred during each era. The Precambrian era saw the emergence of single-celled and then multicellular life. During the Paleozoic, hard-shelled creatures developed and land plants evolved as the continents merged into Pangaea. The Mesozoic was the age of dinosaurs until an asteroid impact caused a mass extinction. Finally, the Cenozoic is our current era dominated by mammals.