List of time periods - Wikipedia, the free encyclopedia
The categorization of time into discrete named blocks is called periodization. This is a list of such named time periods as defined in various fields of study. Major categorization systems include ...
en.wikipedia.org/wiki/List_of_time_periods
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The first geologic time scale was proposed in 1913 by the British geologist Arthur Holmes (1890 - 1965). This was soon after the discovery of radioactivity, and using it, Holmes estimated that the Earth was about 4 billion years old - this was much greater than previously believed.
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www.enchantedlearning.com/subjects/Geologictime.html
www.enchantedlearning.com/subjects/Geologictime.html
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All modern phyla evolved by this time. Foundation plans for higher animals include true tissues, a form of embryo development called gastrulation, ... [7] 13.7 billion years ago:; Big Bang and origin of universe! Before the big bang, no time or space exists. Within 3 minutes of the big bang, there is still no light and no...
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www.ecotao.com/holism/bp.htm
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The Earth is very old -- 4.5 billion years or more -- according to recent estimates. This vast span of time, called geologic time by earth scientists, is difficult to comprehend in the familiar time units of months and years, or even centuries.
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pubs.usgs.gov/gip/geotime/geotime.html
pubs.usgs.gov/gip/geotime/geotime.html
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Although Boltwood's ages have since been revised, they did show correctly that the duration of geologic time would be measured in terms of hundreds-to-thousands of millions of years. ... The mathematical expression that relates radioactive decay to geologic time is called the age equation and is:
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pubs.usgs.gov/gip/geotime/radiometric.html
pubs.usgs.gov/gip/geotime/radiometric.html
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In order to be familiar with the last great Ice Age, one must understand the timeframe in which it occurred. With evidence suggesting that the Earth is 4.5 billion years old, geologists have divided the history of the Earth into units called eras. ... Within those eras are even smaller units of time called periods and epochs.
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www.tarpits.org/education/guide/geology/time.html
www.tarpits.org/education/guide/geology/time.html
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When one mentions "geologic time" to a geoscientist, that person immediately starts to think in terms of millions to billions of years. The Earth organized as a large accreted body between 4.5 and 4.6 billion years ago.
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rst.gsfc.nasa.gov/Sect2/Sect2_1b.html
rst.gsfc.nasa.gov/Sect2/Sect2_1b.html
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According to the Divisions of Geologic Time -- Major Chronostratigraphic and Geochronologic Units (USGS Fact Sheet 2007-3015, March 2007), for many years the term "Precambrian" was used for the division of time older than the Phanerozoic Eon (which includes the Cenozoic, Mesozoic, and Paleozoic Eras, see above).
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vulcan.wr.usgs.gov/Glossary/geo_time_scale.html
vulcan.wr.usgs.gov/Glossary/geo_time_scale.html
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The Earth has been around for approximately four and a half billion years! The geologic time scale is the timeline that describes all this time.
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www.windows.ucar.edu/tour/link=/earth/past/geologic_tim...
www.windows.ucar.edu/tour/link=/earth/past/geologic_time.html
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