Geology and Oceanography

The Oxford Companion to the... Animal Sciences A Dictionary of Earth Sciences A Dictionary of Ecology Further reading

Geological Time Scale

Animal Sciences | 2002 | Copyright

Geological Time Scale

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

Bibliography

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. <http://pubs.usgs.gov/gip/fossils/contents.html>.

Cite this article
Pick a style below, and copy the text for your bibliography.

MLA
Chicago
APA

"Geological Time Scale." Animal Sciences. 2002. Encyclopedia.com. 26 May. 2012 <http://www.encyclopedia.com>.

"Geological Time Scale." Animal Sciences. 2002. Encyclopedia.com. (May 26, 2012). http://www.encyclopedia.com/doc/1G2-3400500159.html

"Geological Time Scale." Animal Sciences. 2002. Retrieved May 26, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1G2-3400500159.html

Learn more about citation styles

geologic time-scale

A Dictionary of Earth Sciences | 1999 | | Copyright

geologic time-scale A two-fold scale that subdivides all the time since the Earth first came into being into named units of abstract time, and subdivides all the rocks formed since the Earth came into being, into the successions of rock formed during each particular interval of time. The branch of geology that deals with the age relations of rocks is known as chronostratigraphy. The concept of a geologic time-scale has been evolving for the last century and a half, commencing with a relative time-scale (mainly achieved through biostratigraphy), to which it has gradually become possible to assign dates (see DATING METHODS) which are, nonetheless, subject to constant revision and refinement. Since the first International Geological Congress in Paris in 1878, one of the main objectives of stratigraphers has been the production of a complete and globally accepted stratigraphic scale to provide a historical framework into which all rocks, anywhere in the world, can be fitted (see STANDARD STRATIGRAPHIC SCALE; CHRONOSTRATIGRAPHIC SCALE; UNIFIED STRATIGRAPHIC SCALE). Such a standard scale is still a long way off, but the names for geologic-time units and chronostratigraphic units down to the rank of period/system are in common use; many epoch/series and age/stage names are still regionally variable. See Time Scales gives an outline geologic time-scale employing currently common names and dates (though they are not necessarily universally accepted).

Cite this article
Pick a style below, and copy the text for your bibliography.

MLA
Chicago
APA

AILSA ALLABY and MICHAEL ALLABY. "geologic time-scale." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. 26 May. 2012 <http://www.encyclopedia.com>.

AILSA ALLABY and MICHAEL ALLABY. "geologic time-scale." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. (May 26, 2012). http://www.encyclopedia.com/doc/1O13-geologictimescale.html

AILSA ALLABY and MICHAEL ALLABY. "geologic time-scale." A Dictionary of Earth Sciences. 1999. Retrieved May 26, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O13-geologictimescale.html

Learn more about citation styles

geologic time-scale

A Dictionary of Ecology | 2004 | | Copyright

geologic time-scale A twofold scale that subdivides all the time since the Earth first came into being into named units of abstract time, and subdivides all the rocks formed since the Earth came into being into the successions of rock formed during each particular interval of time. The branch of geology that deals with the age relations of rocks is known as chronostratigraphy. The concept of a geologic time-scale has been evolving for the last century and a half, commencing with a relative time-scale (mainly achieved through biostratigraphy), to which it has gradually become possible to assign dates which are, nonetheless, subject to constant revision and refinement. Since the first International Geological Congress in Paris in 1878, one of the main objectives of stratigraphers has been the production of a complete and globally accepted stratigraphic scale to provide a historical framework into which all rocks, anywhere in the world, can be fitted. Such a standard scale is still a long way off, but the names for geologic-time units and chronostratigraphic units down to the rank of period/system are in common use; many epoch/series and age/stage names are still regionally variable.

Cite this article
Pick a style below, and copy the text for your bibliography.

MLA
Chicago
APA

MICHAEL ALLABY. "geologic time-scale." A Dictionary of Ecology. 2004. Encyclopedia.com. 26 May. 2012 <http://www.encyclopedia.com>.

MICHAEL ALLABY. "geologic time-scale." A Dictionary of Ecology. 2004. Encyclopedia.com. (May 26, 2012). http://www.encyclopedia.com/doc/1O14-geologictimescale.html

MICHAEL ALLABY. "geologic time-scale." A Dictionary of Ecology. 2004. Retrieved May 26, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O14-geologictimescale.html

Learn more about citation styles

Geologic Timescale

The Columbia Encyclopedia, 6th ed. | 2011 | Copyright

Geologic Timescale

Not an era but the time preceding the Cambrian.

Geologic Timescale

Era	Period	Epoch	Approximate duration (millions of years)	Approximate number of years ago (millions of years)

Cenozoic	Quaternary	Holocene	10,000 years ago to the present
	Quaternary	Pleistocene	2	.01
	Tertiary	Pliocene	11	2
		Miocene	12	13
		Oligocene	11	25
		Eocene	22	36
		Paleocene	71	58
Mesozoic	Cretaceous		71	65
	Jurassic		54	136
	Triassic		35	190
Paleozoic	Permian		55	225
	Carboniferous		65	280
	Devonian		60	345
	Silurian		20	405
	Ordovician		75	425
	Cambrian		100	500
Precambrian			>4,000	600

Cite this article
Pick a style below, and copy the text for your bibliography.

MLA
Chicago
APA

"Geologic Timescale." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. 26 May. 2012 <http://www.encyclopedia.com>.

"Geologic Timescale." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. (May 26, 2012). http://www.encyclopedia.com/doc/1E1-geotimeTABLE.html

"Geologic Timescale." The Columbia Encyclopedia, 6th ed.. 2011. Retrieved May 26, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-geotimeTABLE.html

Learn more about citation styles

geologic timescale

The Columbia Encyclopedia, 6th ed. | 2011 | Copyright

geologic timescale a chronological scale of earth's history used to measure the relative or absolute age of any part of geologic time. Of the numerous timescales, the most common is based on geologic time units, which divide time into eras, periods, and epochs. Each division is based on a specific set of geological or paleontological conditions that make it different from the other divisions, such as varying rock type or fossils within the strata. The largest unit is the eon; eons are subdivided into eras; eras into periods; and some, usually more recent periods, into epochs. In some timescales, epochs are further divided into ages. Each geologic time chart varies, depending on the latest findings dating rocks and fossils of that particular age, or on the country where the chart originated. For each unit and its subdivisions, which are listed in the table entitled Geologic Timescale , see separate articles.

Cite this article
Pick a style below, and copy the text for your bibliography.

MLA
Chicago
APA

"geologic timescale." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. 26 May. 2012 <http://www.encyclopedia.com>.

"geologic timescale." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. (May 26, 2012). http://www.encyclopedia.com/doc/1E1-geolog-ts.html

"geologic timescale." The Columbia Encyclopedia, 6th ed.. 2011. Retrieved May 26, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-geolog-ts.html

Learn more about citation styles

geological time

World Encyclopedia | 2005 | Copyright

geological time Time scale of the history of Earth. Until recently, only methods of relative dating were possible, by studying the correlation of rock formations and fossils. The largest divisions of geologic time are called eras, each of which is broken down into periods, which, in turn, are subdivided into series or epochs.

Cite this article
Pick a style below, and copy the text for your bibliography.

MLA
Chicago
APA

"geological time." World Encyclopedia. 2005. Encyclopedia.com. 26 May. 2012 <http://www.encyclopedia.com>.

"geological time." World Encyclopedia. 2005. Encyclopedia.com. (May 26, 2012). http://www.encyclopedia.com/doc/1O142-geologicaltime.html

"geological time." World Encyclopedia. 2005. Retrieved May 26, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O142-geologicaltime.html

Learn more about citation styles

geological time scale

geological time scale A time scale that covers the earth's history from its origin, estimated to be about 4600 million years ago, to the present. The chronology is divided into a hierarchy of time intervals: eons, eras, periods, epochs, ages, and chrons.

Cite this article
Pick a style below, and copy the text for your bibliography.

MLA
Chicago
APA

"geological time scale." A Dictionary of Biology. 2004. Encyclopedia.com. 26 May. 2012 <http://www.encyclopedia.com>.

"geological time scale." A Dictionary of Biology. 2004. Encyclopedia.com. (May 26, 2012). http://www.encyclopedia.com/doc/1O6-geologicaltimescale.html

"geological time scale." A Dictionary of Biology. 2004. Retrieved May 26, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O6-geologicaltimescale.html

Learn more about citation styles

Free newspaper and magazine articles

	A Geologic Time Scale 2004.(Book review) Magazine article from: Geoscience Canada; 12/1/2006
	Your salary in 2016.(THE STAKES 2008) Magazine article from: The Washington Monthly; 8/1/2008
	Earthly riches may be heaven-sent: meteorites possibly peppered planet with... Magazine article from: Science News; 10/8/2011