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Although the term aeon may be used in reference to a period of a billion years (especially in geology, cosmology and astronomy), its more common usage is for any long, indefinite period. Aeon can also refer to the four aeons on the geologic time scale that make up the Earth's history, the Hadean , Archean , Proterozoic , and the current aeon, Phanerozoic .
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).
- What Is Geologic dating?
- Hadean
- Archean
- Proterozoic
- Phanerozoic
Geologic dating allows scientists to better understand ancient history, including the evolution of plant and animal life from single-celled organisms to dinosaurs to primates to early humans. It also helps them learn more about how human activity has transformed the planet. (c) 2013 Andrew Alden, licensed to About.com, Inc. (fair use policy). Data ...
The oldest of the geologic eons is the Hadean, which began about 4.6 billion years ago with the formation of Earth and ended about 4 billion years ago with the appearance of the first single-celled organisms. This eon is named after Hades, the Greek god of the underworld, and during this period the Earth was extremely hot. Artist renderings of the ...
The next geologic eon, the Archean, began about 4 billion years ago. During this period, the cooling of the Earth's crust allowed for the formation of the first oceans and continents. Scientists are not exactly sure what these continents looked like since there is so little evidence from the period. However, some believe the first landmass on Earth...
The Proterozoic eon began about 2.5 billion years ago and ended about 500 million years ago when the first complex lifeforms appeared. During this period, the Great Oxygenation Event transformed the Earth's atmosphere, allowing for the evolution of aerobic organisms. The Proterozoic was also the period in which the Earth's first glaciers formed. So...
The most recent geologic eon is the Phanerozoic, which began about 540 million years ago. This eon is very distinct from the previous three—the Hadean, Archean, and Proterozoic—which are sometimes known as the Precambrian era. During the Cambrian period—the earliest part of the Phanerozoic—the first complex organisms appeared. Most of them were aqu...
- Andrew Alden
Sep 13, 2024 · The geologic time scale is the “calendar” for events in Earth history. It subdivides all time into named units of abstract time called—in descending order of duration— eons, eras, periods, epochs, and ages. The enumeration of those geologic time units is based on stratigraphy, which is the correlation and classification of rock strata.
- The Editors of Encyclopaedia Britannica
Dec 6, 2023 · The Geologic Time Scale is divided into several large units of time, including eons, eras, periods, and epochs. The largest unit of time is the eon, which is divided into eras. Eras are further divided into periods, and periods are divided into epochs. Each unit of time is defined by specific events and changes that took place on Earth, such as ...
eon, Long span of geologic time. In formal usage, eons are the longest portions of geologic time (era s are the second-longest). Three eons are recognized: the Phanerozoic Eon (dating from the present back to the beginning of the Cambrian Period), the Proterozoic Eon, and the Archean Eon. Less formally, eon often refers to a span of one billion ...
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Aug 3, 2023 · Definition of Eon. “Eon,” also spelled as “aeon,” refers to the largest division of the geologic time scale, superseding eras. It signifies an indefinitely long period, often used to describe billion-year timescales in the field of geology and cosmology [1]. Eons are divided into eras, which are further segmented into periods, epochs ...
