Geoltimescale
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The geologic time scale is divided into eons, eras, and periods that together span Earth's history from its formation to the present day. It shows the development of life through time, from the earliest single-celled organisms in the Archean eon over 3 billion years ago to the rise and dominance of dinosaurs in the Mesozoic era and the emergence of modern plants and animals in the Cenozoic era. The Precambrian eons of Hadean, Archean, and Proterozoic comprise about 87% of geologic time.
Geoltimescale
- 1. GEOLOGIC TIME SCALE Time Units of the Geologic Time Scale Development of Plants and AnimalsEon Era Period Epoch PhanerozoicProterozoicArchean Hadean Quaternary Tertiary CenozoicMesozoicPalaeozoic Cretaceous Jurassic Triassic Permian Carboniferous Pennsylvanian Mississippian Devonian Silurian Ordovician Cambrian Collectively called Precambrian comprises about 87% of the geological time scale Holocene Pleistocene Pliocene Miocene Palaeocene Oligocene Eocene “Age of Reptiles” “Age of Amphibians” “Age of Fishes “Age of Invertebrates” Earliest Homo sapiens “Age of Mammals” Extinction of trilobites and many other marine animals First reptiles Large coal swamps Amphibians abundant First insect fossils Fishes dominant First land plants First fishes Trilobites dominant First multicelled organisms First one-celled organisms Age of oldest rocks Origin of the earth First flowering plants First birds Dinosaurs dominant 4600 Ma 3800 2500 505 438 410 360 320 286 248 208 145 65 0.01 1.6 5.3 23.8 33.7 55 Extinction of dinosaurs and many other species First organisms with shells First mammals First amphibians Earliest hominids 545 650 Abundant Ediacaran faunasVendian “Soft-bodied faunas”