Eons, Eras, Periods, and Epochs
4.6-4.0 Billion Years Ago
4.0-2.5 Billion Years Ago
2.5 Billion - 542 million years ago
542 million years ago - present
This precambian time period was defined by the formation of rock through volcanic explosion and a molten surface.
The Hadean Eon
This eon began with an atmosphere of methane droplets followed by the rise of cyanobacteria which produced free oxygen through photosynthesis.
The Archean Eon
The final precambrian eon where the earth's temperature dropped steaply and cells became more specialized leading to the first eukaryotic organisms.
The Proterozoic Eon
This eon saw an explosion of life leading to the world as we know it today. It is studied in three eras, twelve periods, and several epochs.
The Phanerozoic Eon
This period saw creatures with exoskeletons like trilobites which followed by vascular plants and amphibians.
The Paleozoic Era
The Paleozoic Era
The Mesozoic Era
The TriassicPeriodThis period lasted from 251-199 million years ago. Most of the continents were still merged in super-continent Pangaea. This time was dominated by reptiles, but the first mammals appeared at the end of this period.
The JurassicPeriodThis period lasted from 199 to 145 million years ago. Pangaea split into smaller continents. This is when dinosaurs came to dominate the planet.
The CretaceousPeriodThis period 145 to 66 million years ago, and it saw one of Earth's mass extinctions where many groups such as dinosaurs died out.
The Cenozoic Era
The Paleogene PeriodThis period stretched from 66 to 23 million years ago. This period has three epochs the Paleocene, the Eocene, and the Oligocene. During this period mammals began to take control.
The Eocene PeriodThis period lasted from 23 to 2.58 million years ago, and is divided into the Miocene Epoch and the Pliocene Epoch.
The Quaternary PeriodThis period lasted from 2 million years ago to present. This period is divided into the Pleistocene Epoch and the Holocene Epoch, and it saw the rise of Homo sapiens and human civilizations.