Geologic Record and History of Life on Earth

Vocabulary terms from the geologic record and history of life, covering eons, eras, periods, and epochs.

mya

Millions of years ago

bya

Billions of years ago

Hadeon Eon

The eon from approximately $4.6\,bya$ to $4\,bya$ representing the origins of earth.

Archaeon Eon

The geologic eon from $4\,bya$ to $2.5\,bya$ during which the earth’s crust formed and the oldest prokaryote fossils appeared.

Great Oxidation Event (GOE)

An event occurring around $2.46\,bya$ when the concentration of atmospheric oxygen began to increase.

Proterozoic Eon

The eon from $2.5\,bya$ to $541\,mya$ meaning ‐Earlier Life‐ where the oldest fossils of eukaryotic cells appeared.

Ediacaran period

A period from $635-542\,mya$ characterized by the appearance of diverse algae and soft bodied invertebrates.

Cambrian Explosion

A sudden increase in diversity in many animal phyla occurring during the Cambrian Period ($542-488\,mya$).

Devonian Period

The period from $416-359\,mya$ marked by the diversification of bony fishes and the appearance of the first tetrapods and insects.

Carboniferous Period

The period from $359-299\,mya$ involving the formation of extensive vascular plant forests, the appearance of seed plants, the origin of reptiles, and the dominance of amphibians.

Permian Period

The period from $299-251\,mya$ characterized by the radiation of reptiles and the extinction of many marine and terrestrial organisms at its conclusion.

Gymnosperms

Cone bearing plants that dominated the landscape during the Triassic and Jurassic periods.

Angiosperms

Flowering plants that appeared and diversified during the Cretaceous period ($145.5-65.5\,mya$).

Mesozoic Era

The era from $251-65.5\,mya$ encompassing the Triassic, Jurassic, and Cretaceous periods.

Oligocene Epoch

The epoch from $33.9-23\,mya$ that saw the origins of many primate groups.

Miocene Epoch

The epoch from $23-5.3\,mya$ involving the radiation of mammals and angiosperms, and the earliest direct human ancestors.

Pliocene Epoch

The epoch from $5.3-2.6\,mya$ characterized by the appearance of bipedal human ancestors.

Pleistocene Epoch

The epoch from $2.6-0.01\,mya$ featuring ice ages and the origins of the genus Homo.

Holocene Epoch

The epoch from $0.01\,mya$ to the present, representing historical time.