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Sevier orogeny – Mountain-building episode in North America – Rocky Mountains, western North America, (140–50 Ma) Laramide orogeny – Period of mountain building in North America – Rocky Mountains, western North America, (40–70 Ma) Pasadena orogeny – Transverse Ranges, western North America, Pleistocene Period to present day
Elsewhere in North America, as in Illinois, the Yarmouth Soil also has developed over a variable number of multiple glacial - interglacial cycles. [4] [8] Thus, the presumption that the Yarmouth Soil, by which the Yarmouthian (Yarmouth) Interglacial was later defined, represents a single interglacial stage or period has been completely discredited.
Ancient history – Aggregate of past events from the beginning of recorded human history and extending as far as the Early Middle Ages or the Postclassical Era. The span of recorded history is roughly five thousand years, beginning with the earliest linguistic records in the third millennium BC in Mesopotamia and Egypt .
After the Cretaceous, a new era of geologic time began; the Cenozoic era, which means the era of "recent life". Traditionally, the first period of the Cenozoic was called the Tertiary , [ 131 ] however recent recommendations of the International Commission on Stratigraphy discourage its use, with the correspondent time span divided between the ...
The geologic time scale is a way of representing deep time based on events that have occurred throughout Earth's history, a time span of about 4.54 ± 0.05 Ga (4.54 billion years). [3] It chronologically organises strata, and subsequently time, by observing fundamental changes in stratigraphy that correspond to major geological or ...
Each period is marked below the era bar on top of its subdivided epochs and stages. Each stage is assigned an age in mya , an acronym for million years ago, which is the age at which it began. Most of these ages are derived from astronomical cycles in sediments, magnetic data, biostratigraphic data, and radiometric dating methods.
The term geon (for geological eon) refers to large, geologic units of time. Geologists traditionally subdivide Earth history into a hierarchy of named intervals: eons, eras, periods, etc. (e.g., the Jurassic Period of the Mesozoic Era). Historians subdivide the history of human activity into intervals that are comparatively much shorter.
Often applied to the trace mineral zircon in igneous rocks, this method is one of the two most commonly used (along with argon–argon dating) for geologic dating. Monazite geochronology is another example of U–Pb dating, employed for dating metamorphism in particular. Uranium–lead dating is applied to samples older than about 1 million years.