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Encyclopedia > Geologic period

In geology, a period or age is a time span of many millions of years that are assumed to have had similar characteristics. In general, the duration of Periods/Ages tend to get longer the further one travels into the past.


Geologic Period/Age boundaries are generally set at some distinct worldwide event such as a mass extinction. For example, the boundary between the Cretaceous period and the Palaeogene period is set at an extinction event that marked the demise of the dinosaurs and of many marine species.


See also


  Results from FactBites:
 
Encyclopedia4U - Geologic timescale - Encyclopedia Article (343 words)
All of these terms are usually treated as a subset of the Proterozoic rather than a period between the Paleozoic and the Proterozoic.
This is largely due to uncertainties in radiometric dating and the problem that deposits suitable for radiometric dating seldom occur exactly at the places in the geologic column where we would most like to have them.
5) In common usage the Tertiary-Quaternary and Paleogene-Neogene-Quaternary Periods are treated as equivalents to the Mesozoic and Paleozoic Periods.
List of time periods - Wikipedia, the free encyclopedia (328 words)
The geologic timescale covers the extent of the existence of Earth, from about 4600 million years ago to the present day.
These names differ across different countries; in particular, the division of the Carboniferous period into Mississippian and Pennsylvanian is purely a North American distinction.
Periodization for a discussion of the tendency to try to fit history into non-overlapping periods.
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