List of Geologic Timescale

Related articles: Cambrian period Cambrian period
[Lat. Cambria=Wales], first period of the Paleozoic geologic era (see Geologic Timescale, table) extending from approximately 570 to 505 million years ago.
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, Carboniferous period Carboniferous period
, fifth period of the Paleozoic era of geologic time (see Geologic Timescale, table), from 350 to 290 million years ago. Historical Geology of the Period
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, Cenozoic era Cenozoic era
, last major division of geologic time (see Geologic Timescale, table) lasting from 65 million years ago to the present. The Cenozoic is divided into the Tertiary (from 65 million years ago until 2 million years ago) and Quaternary (2 million years ago to the
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, Cretaceous period Cretaceous period
, third and last period of the Mesozoic era of geologic time (see Geologic Timescale, table), lasting from approximately 144 to 65 million years ago. The Cretaceous was marked, in both North America and Europe, by extensive submergences of the continents.
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, Devonian period Devonian period
, fourth period of the Paleozoic era of geologic time between 408 and 360 million years ago (see Geologic Timescale, table). It was named (1838) by the geologists Sir Roderick Impey Murchison and Adam Sedgwick for Devonshire, England, where they first
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, epoch epoch,
unit of geologic time that is a subdivision of a period. The Pleistocene and Holocene epochs, for example, are divisions of the Quaternary period. Epoch is also used to describe a short length of geologic time during a special occurrence, such as the glacial epoch.
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, geologic timescale 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.
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, Holocene epoch Holocene epoch
or Recent epoch,
most recent of all subdivisions of geologic time, ranging from the present back to the time (c.11,000 years ago) of almost complete withdrawal of the glaciers of the preceding Pleistocene epoch.
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, Jurassic period Jurassic period
[from the Jura Mts.], second period of the Mesozoic era of geologic time, lasting from 213 to 144 million years ago. At the start of the Jurassic most of the continents were joined together until the Atlantic began to form and the Americas split off from Africa.
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, Mesozoic era Mesozoic era
[Gr.,=middle life], major division of geologic time (see Geologic Timescale, table) from 65 to 225 million years ago. Great crustal disturbances that marked the close of the Paleozoic and the beginning of the Mesozoic eras brought about drastic changes in the
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, Miocene epoch Miocene epoch
, fourth epoch of the Tertiary period in the Cenozoic era of geologic time (see Geologic Timescale, table), lasting from around 24.6 to 5.1 million years ago.
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, Ordovician period Ordovician period
[from the Ordovices, ancient tribe of N Wales], second period of the Paleozoic era of geologic time (see Geologic Timescale, table) from 505 to 438 million years ago.
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, Paleozoic era Paleozoic era
, a major division (era) of geologic time (see Geologic Timescale, table) occurring between 570 to 240 million years ago. It is subdivided into six periods, the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian (see each listed individually).
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, Permian period Permian period
[from Perm, Russia], sixth and last period of the Paleozoic era (see Geologic Timescale, table) from 250 to 290 million years ago. Historical Geology of the Period
The Lower Permian
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, Pleistocene epoch Pleistocene epoch
, 6th epoch of the Cenozoic era of geologic time (see Geologic Timescale, table). According to a classification that considered its deposits to have been formed by the biblical great flood, the epoch was originally called the Quaternary.
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, Pliocene epoch Pliocene epoch
, fifth epoch of the Cenozoic era of geologic time (see Geologic Timescale, table), from 5.1 to 2 million years ago. By the beginning of the Pliocene, the outlines of North America were almost the same as in recent time.
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, Precambrian Precambrian,
name of a major division of geologic time (see Geologic Timescale, table), from c.5 billion to 570 million years ago. It is now usually divided into the Archean and Proterozoic eons. Precambrian time includes 80% of the earth's history.
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, Quaternary period Quaternary period
, younger of the two geologic periods of the Cenozoic era of geologic time (see Geologic Timescale, table) from 2 millon years ago to the present. Comprising all geologic time from the end of the Tertiary period to the present, it is divided into the
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, Silurian period Silurian period
[from the Silures, ancient tribe of S Wales, where the period was first studied; named by the British geologist R. I. Murchison], third period of the Paleozoic era of geologic time (see Geologic Timescale, table) lasting from 405 to 435 million years ago.
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, tertiary tertiary
, in the Roman Catholic Church, member of a third order. The third orders are chiefly supplements of the friars—Franciscans (the most numerous), Dominicans, and Carmelites.
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, Tertiary period Tertiary period
, name for the major portion of the Cenozoic era, the most recent of the geologic eras (see Geologic Timescale, table) from around 26 to 66 million years ago. The name Tertiary was first applied about the middle of the 18th cent.
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, Triassic period Triassic period
, first period of the Mesozoic era of geologic time (see Geologic Timescale, table) from 205 to 250 million years ago.

Throughout the Triassic, E North America, as a result of the mountain-building episode that formed the Appalachians in the late Paleozoic
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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  
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
Precambrian1     >4,000 600
1 Not an era but the time preceding the Cambrian.
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