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The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochronology (a scientific branch of geology that aims to determine the age of rocks).
Geologic time shown in a diagram called a geological clock, showing the relative lengths of the eons of Earth's history and noting major events The geological history of Earth follows the major geological events in Earth's past based on the geologic time scale , a system of chronological measurement based on the study of the planet's rock ...
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 .
[2] [3] [4] Two or more radiometric methods can be used in concert to achieve more robust results. [5] Most radiometric methods are suitable for geological time only, but some such as the radiocarbon method and the 40 Ar/ 39 Ar dating method can be extended into the time of early human life [6] and into recorded history. [7]
This is a list of official and unofficial names for time spans in the geologic timescale and units of chronostratigraphy.Since many of the smallest subdivisions of the geologic timescale were in the past defined on regional lithostratigraphic units, there are many alternative names that overlap.
The Great Valley Sequence of California is a 40,000-foot (12 km)-thick group of related geologic formations that are Late Jurassic through Cretaceous in age (150–65 Ma) on the geologic time scale. These sedimentary rocks were deposited during the late Mesozoic Era in an ancient seaway that corresponds roughly to the outline of the modern ...
Historical geology or palaeogeology is a discipline that uses the principles and methods of geology to reconstruct the geological history of Earth. [1] Historical geology examines the vastness of geologic time, measured in billions of years, and investigates changes in the Earth , gradual and sudden, over this deep time .
Fossil footprints from this time period were also preserved in eastern states like Alabama, Georgia, West Virginia, Ohio, and Pennsylvania where Carboniferous fossil footprints are known. [35] Dimetrodon. The world's continents were joined as Pangaea throughout all of the Permian. Volcanic activity occurred on the west coast.