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The Hadean (/ h eɪ ˈ d iː ə n, ˈ h eɪ d i ə n / hay-DEE-ən, HAY-dee-ən) is the first and oldest of the four known geologic eons of Earth's history, starting with the planet's formation about 4.6 billion years ago [4] [5] (estimated 4567.30 ± 0.16 million years ago [2] set by the age of the oldest solid material in the Solar System — protoplanetary disk dust particles — found as ...
The Cryptic era is an informal term for the earliest geologic evolution of the Earth and Moon.It is the oldest (informal) era of the Hadean eon, and it is commonly accepted to have begun close to about 4.533 billion years ago when the Earth and Moon formed, and lasted to about 4.15 billion years ago.
A revised proposal in 2012 [2] suggested the Chaotian as the first era of the Hadean representing the time between the formation of the Solar System c. 4.567 Ga [3] and the oldest preserved crustal material on Earth, a detrital zircon c. 4.404 Ga [4] from the Jack Hills of the Narryer terrane in Western Australia.
The first eon in Earth's history, the Hadean, begins with the Earth's formation and is followed by the Archean eon at 3.8 Ga. [2]: 145 The oldest rocks found on Earth date to about 4.0 Ga, and the oldest detrital zircon crystals in rocks to about 4.4 Ga, [34] [35] [36] soon after the formation of the Earth's crust and the Earth
In particular, it is sometimes found that the Hadean eon is subdivided into the Cryptic era and Basin Groups 1-9 (which collectively make up the Pre-Nectarian), and the Nectarian and Lower Imbrian. The first lifeforms (self replicating RNA molecules, see RNA world hypothesis ) may have evolved on earth around 4 bya during this era.
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The Precambrian is an informal unit of geologic time, [3] subdivided into three eons (Hadean, Archean, Proterozoic) of the geologic time scale. It spans from the formation of Earth about 4.6 billion years ago to the beginning of the Cambrian Period, about 538.8 million years ago , when hard-shelled creatures first appeared in abundance.
Prehistoric warfare refers to war that occurred between societies without recorded history.. The existence—and the definition—of war in humanity's hypothetical state of nature has been a controversial topic in the history of ideas at least since Thomas Hobbes in Leviathan (1651) argued a "war of all against all", a view directly challenged by Jean-Jacques Rousseau in a Discourse on ...