Encyclopedia Article

Geological Time Scale - Research Article from Macmillan Science Library: Animal Sciences

This encyclopedia article consists of approximately 2 pages of information about Geological Time Scale.
This section contains 312 words
(approx. 2 pages at 300 words per page)

Geologic Time Scale
Era Period Epoch Significant Events Million Years Before Present
Cenozoic Quartenary Holocene recorded human history, rise and fall of civilizations, global warming, habitat destruction, pollution mass extinction 0.01
Pleistocene Homo sapiens, ice ages 1.6
Tertiary Pliocene global cooling, savannahs, grazing mammals 5.3
Miocene global warming, grasslands, Chalicotherium 24
Oligocene 37
Eocene modern mammals flourish, ungulates 58
Paleocene 66
Mesozoic Cretaceous last of age of dinosaurs, modern mammals appear, flowering plants, insects 144
Jurassic huge plant-eating dinosaurs, carnivorous dinosaurs, first birds, breakup of Pangea 208
Triassic lycophytes, glossopterids, and dicynodonts, and the dinosaurs 245
Paleozoic Permian Permian ends with largest mass extinction in history of Earth, most marine inverterbrates extinct 286
Pennsylvanian vast coal swamps, evolution of amniote egg allowing exploitation of land 320
Missipian shallow seas cover most of Earth 360
Devonian vascular plants, the first tetrapods, wingless insects, arachnids, brachiopods, corals, and ammonite were also common, many new kinds of fish appeared 408
Silurian Coral reefs, rapid spread of jawless fish, first freshwater fish, first fish with jaws, first good evidence of life on land, including relatives of spiders and centipedes 438
Ordovician most dry land collected into Gondwana, many marine invertebrates, including graptolites, trilobites, brachiopods, and the conodonts (early vertebrates), red and green algae, primitive fish, cephalopods, corals, crinoids, and gastropods, possibly first land plants 505
Cambrian most major groups of animals first appear, Cambrian explosion 570
Proterozoic stable continents first appear, first abundant fossils of living organisms, mostly bacteria and archeobacteria, first eukaryotes, first evidence of oxygen build-up 2500
Archean atmosphere of methane, ammonia, rocks and continental plates began to form, oldest fossils consist of bacteria microfossils stromatolites, colonies of photosynthetic bacteria 3800
Hadean pre-geologic time, Earth in formation 4500


Foster, Robert. Geology. 3rd ed. Columbus, OH: Charles E. Merrill, 1976.

Stanley, Stephen. Earth and Life Through Time. New York: W. H. Freeman, 1989.

Toulmin, Stephen and June Goodfield. The Discovery of Time. New York: Harper & Row, 1965.

Internet Resources

United States Geological Survey. .

This section contains 312 words
(approx. 2 pages at 300 words per page)
Geological Time Scale from Macmillan. Copyright © 2001-2006 by Macmillan Reference USA, an imprint of the Gale Group. All rights reserved.
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