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Encyclopedia > Hadean
Hadean eon
Geologic timescale of the Precambrian
(millions of years ago)

(expand) The geologic time scale is used by geologists and other scientists to describe the timing and relationships between events that have occurred during the history of the Earth. ... The Precambrian is an informal name for the eons of the geologic timescale that came before the current Phanerozoic eon. ...

The name Hadean refers to the geologic period before 3800 million years ago (mya). The geologist Preston Cloud coined the term in 1972, originally to label the period before the earliest-known rocks. In the last decades of the 20th century geologists identified a few Hadean rocks from Western Greenland, Northwestern Canada and Western Australia. Some sources of information give other dates for the end of the Hadean 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 astronomy, geology, and paleontology, mya is an acronym for million years ago and is used as a unit of time to denote length of time before the present. ... A geologist is a contributor to the science of geology, studying the physical structure and processes of the Earth. ... Preston Ercelle Cloud, Jr. ... 1972 (MCMLXXII) was a leap year starting on Saturday (the link is to a full 1972 calendar). ... Sedimentary, volcanic, plutonic, metamorphic rock types of North America. ... (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999 in the... Motto: Cygnis Insignis (Distinguished by its swans) Nickname: Wildflower State Other Australian states and territories Capital Perth Government Governor Premier Const. ...


W. B. Harland later coined an almost synonymous term: the "Priscoan period".


The oldest known rock formations comprise somewhat altered sediments from Greenland dated around 3800 mya by a volcanic dike that penetrated the rocks after they were deposited. Individual zircon crystals redeposited in sediments in Western Canada and the Jack Hills region of Western Australia are much older. The oldest dated zircons date from about 4400 mya - very close to the hypothesized time of the Earth's formation. The Greenland sediments include banded iron beds. They contain possibly organic carbon and quite possibly indicate that photosynthetic life had already emerged at that time. The oldest known fossils (from Australia) date from a few hundred million years later. Eruption redirects here. ... A dike in geology refers to a tabular intrusive igneous body. ... Zircon is a mineral belonging to the group of nesosilicates. ... Quartz crystal A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ... Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of water or other liquid. ... Western Canada is a geographic region of Canada, also known as simply the West, generally considered to be west of the province of Ontario. ... The Jack Hills are located in the Narryer Terrane of the Yilgarn Craton, Western Australia, and comprise an 80 km long northeast-trending belt of folded and metamorphosed supracrustal rocks. ... Motto: Cygnis Insignis (Distinguished by its swans) Nickname: Wildflower State Other Australian states and territories Capital Perth Government Governor Premier Const. ... 2. ... An organic compound is any member of a large class of chemical compounds whose molecules contain carbon, with the exception of carbides, carbonates, carbon oxides and gases containing carbon. ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ... Leaf. ... Look up life and living in Wiktionary, the free dictionary. ... A fossil Ammonite Fossils (from Latin fossus, literally having been dug up) are the mineralized or otherwise preserved remains or traces (such as footprints) of animals, plants, and other organisms. ...


The etymology of the name "Hadean" is from Hades, Greek for "unseen" and suggesting the underworld. Hades, Greek god of the underworld, enthroned, with his bird-headed staff, on a red-figure vase made in the 4th century B.C. Hades (From , Hadēs, or , Háidēs, Greek for unseen) refers to both the ancient Greek abode of the dead and the god of that... // In the study of mythology and religion, the underworld is a generic term approximately equivalent to the lay term afterlife, referring to any place to which newly dead souls go. ...

Precambrian  
Hadean eon Archean eon Proterozoic eon Phanerozoic eon
Hadean eon
Cryptic Basin Groups Nectarian Lower Imbrian

  Results from FactBites:
 
Hadean - Wikipedia, the free encyclopedia (229 words)
The name Hadean refers to the geologic period before 3800 million years ago (mya).
In the last decades of the 20th century geologists identified a few Hadean rocks from Western Greenland, Northwestern Canada and Western Australia.
The etymology of the name "Hadean" is from Hades, Greek for "unseen" and suggesting the underworld.
Hadean Era (2137 words)
The Hadean Era was the first in Earth history, extending from the first formation of continental crust, which began some time around 4,200 Ma (Goodwin 1991, Condie 1997), becoming persistent soon after, to approximately 3,500 Ma.
The Hadean interval is widely recognised, in Europe and elsewhere, though not by the Precambrian Subcommission.
The Precambrian Subcommission, however, does not (at least not yet) recognise the Hadean; the oldest unit recognised by the Subcommission is the Archaean, with a lower boundary dated around 3,900 Ma.
  More results at FactBites »

 
 

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