Geologic time scale

Precambrian

Includes Hadean, Archaean, and Proterozoic Eons.

Hadean Eon

Earth's surface was liquid rock and boiling sulfur.

Archean Eon

Series of volcanic eruptions. Long chains of small islands.

Proterozoic Eon

First evidence of oxygen build-up. Eukaryotic forms rise.

Phanerozoic

Includes Paleozoic, Mesozoic, and Cenozoic Eras.

Paleozoic Era - Key Event

Formation of Pangea. Explosion of different life forms.

Cambrian Period

"Explosion of life." Trilobites appear.

Ordovician Period

Dominated by marine invertebrates.

Silurian Period

First land plants appear.

Devonian Period

"Age of Fishes."

Carboniferous Period

Seed plants and reptiles appear.

Permian Period

Mass extinction event; 90% of Earth species vanish.

Mesozoic Era - Nickname

"Age of Dinosaurs." Land masses remain together.

Triassic Period

Dinosaurs evolve alongside reptiles and mammals.

Jurassic Period

Tectonic shifts occur. Dinosaurs dominate.

Cretaceous Period

Rise of angiosperms (flowering plants).

Cenozoic Era - Nickname

"Age of Mammals." Land masses move to current positions.

Paleogene Period

Extinction of non-avian dinosaurs.

Neogene Period

Rise of diverse large and small mammals.

Miocene Epoch

Distinct flora and fauna develop.

Pliocene Epoch

The development of ice caps, the drying of the Mediterranean, and the joining of the Americas.

Quaternary Period

Evolution of the human genus.