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The Geologic Time Scale
Phanerozoic Eon

(544 million years ago - Present)

The period of time, also known as an eon, between the end of the Precambrian and today, The Phanerozoic begins with the start of the Cambrian period, 544 million years ago. It encompasses the period of abundant, complex life on the Earth.

Era Period or System Epoch or Series
Cenozoic
(65 million years ago - Present)

"Age of Recent Life"

An era of geologic time from the beginning of the Tertiary period to the present. Its name is from Greek and means "new life."


Quaternary
(1.8 million years ago - Present)

The second period of the Cenozoic era. It contains two epochs: the Pleistocene and the Holocene. It is named after the Latin word "quatern" (four at a time).

The several geologic eras were originally named Primary, Secondary, Tertiary, and Quaternary. The first two names are no longer used. Tertiary and Quaternary have been retained but used as period designations.


Holocene
(8,000 years ago - Present)

An epoch of the Quaternary period. It is named after the Greek words "holos" (entire) and "ceno" (new).


Pleistocene
(1.8 million - 8,000 years ago)

"The Great Ice Age"

An epoch of the Quaternary period. It is named after the Greek words "pleistos" (most) and "ceno" (new).


Tertiary
(65 - 1.8 million years ago)

The first period of the Cenozoic era (after the Mesozoic era and before the Quaternary period).


Pliocene
(5.3 - 1.8 million years ago)

Final epoch of the Tertiary period. It is named after the Greek words "pleion" (more) and "ceno" (new).

Miocene
(23.8 - 5.3 million years ago)

A epoch of the upper Tertiary period. It is named after the Greek words "meion" (less) and "ceno" (new).


Oligocene
(33.7 - 23.8 million years ago)

An epoch of the early Tertiary period. It is named after the Greek words "oligos" (little, few) and "ceno" (new).


Eocene
(55.5 - 33.7 million years ago)

An epoch of the lower Tertiary period. Its name is from the Greek words "eos" (dawn) and "ceno" (new).


Paleocene
(65 - 55.5 million years ago)

Earliest epoch of the Tertiary period. It is named after the Greek words "palaois" (old) and "ceno" (new).



Era Period or System Epoch or Series
Mesozoic
(248 - 65 million years ago)

"Age of Medieval Life"

An era of geologic time between the Paleozoic and the Cenozoic. The word Mesozoic is from Greek and means "middle life."


Cretaceous
(145 - 65 million years ago)

"The Age of Dinosaurs"

The final period of the Mesozoic era. The name is derived from the Latin word for chalk ("creta") and was first applied to extensive deposits of this age that form white cliffs along the English Channel between Great Britain and France.


Late or Upper
Early or Lower
Jurassic
(213 - 145 million years ago)

The middle period of the Mesozoic era. It is named after the Jura Mountains between France and Switzerland, where rocks of this age were first studied.


Late or Upper
Middle
Early or Lower
Triassic
(248 - 213 million years ago)

The earliest period of the Mesozoic era. The name Triassic refers to the threefold division of rocks of this age in Germany.

The Break-up of the continent Pangea ... MORE


Late or Upper
Middle
Early or Lower

Era Period or System Epoch or Series
Paleozoic
(544 - 248 million years ago)

"Age of Ancient Life"

An era of geologic time, from the end of the Precambrian to the beginning of the Mesozoic. The word Paleozoic is from Greek and means "old life."


Development of the Eastern Piedmont ... Taconic Orogeny ... MORE


Permian
(286 - 248 million years ago)

The final period of the Paleozoic era. It is named after the province of Perm, Russia, where rocks of this age were first studied.


Late or Upper
Early or Lower
Carboniferous
(360 - 286 million years ago)

A period of time in the Paleozoic era that includes the Pennsylvanian and Mississippian periods.
Pennsylvanian*
(325 - 286 million years ago)

"The Coal Age"

A period of the Paleozoic era. It is named after the state of Pennsylvania where rocks of this age are widespread.


Late or Upper
Middle
Early or Lower
Mississippian*
(360 - 325 million years ago)

A period of the Paleozoic era. It is named after the Mississippi River valley, which contains good exposures of rocks of this age.

Late or Upper
Early or Lower
Devonian
(410 - 360 million years ago)

A period of the Paleozoic era. It is named after Devonshire, England, where rocks of this age were first studied.

Late or Upper
Middle
Early or Lower
Silurian
(440 - 410 million years ago)

A period of the Paleozoic. It is named after a Celtic tribe called the Silures.

Late or Upper
Middle
Early or Lower
Ordovician
(505 - 440 million years ago)

The second earliest period of the Paleozoic era. It is named after a Celtic tribe called the Ordovices.

Late or Upper
Middle
Early or Lower
Cambrian
(544 - 505 million years ago)

The earliest period of the Paleozoic era. It is named after Cambria, the Roman name for Wales, where rocks of this age were first studied.

Late or Upper
Middle
Early or Lower

Precambrian

(Beginning of earth - 544 million years ago)

All geologic time before the beginning of the Paleozoic era. This includes about 90% of all geologic time and spans the time from the beginning of the earth, about 4.5 billion years ago, to 544 million years ago. Its name means "before Cambrian."


Resources:
Table by: Lyn Topinka, USGS/CVO, 1997, 2000, 2001
Mostly modified from: "U. S. Geological Survey, Paleontology website: http://geology.er.usgs.gov/paleo/", with additional comments from other sources (listed below)
  1. U. S. Geological Survey, Paleontology website: http://geology.er.usgs.gov/paleo/, 1997 and January 2001
  2. Newman, Geologic Time Online Edition: USGS General Interest Publication, version 1.2
  3. Newhall and Dzurisin, 1988, Historical Unrest at Large Calderas in the World: USGS Bulletin 1855
  4. Schlee, Our Changing Earth: USGS General Interest Publication, Online Version, January 2001
  5. Swanson, et.al., 1989, Cenozoic vulcanism in the Cascade Range and Columbia Plateau, Southern Washington and Northermost Oregon, AGU Field Trip Guidebook T106
  6. U. S. Army Corps of Engineers, Portland District, and the U. S. Department of the Interior, U. S. Geological Survey, The Geologic History of the Columbia River Gorge: Information Broshure
  7. The Geologic Story of the Ocoee River: USGS General Interest Publication, July 1996
  8. U. S. National Park Service Website - Geology Fieldnotes; Rocky Mountain National Park, Colorado, April 2000

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04/22/02, Lyn Topinka