Eoarchean
Encyclopedia
In the geologic record
the Eoarchean erathem
icon (also spelled Eoarchaean) and the Eoarchean era in the geologic timescale correspond to one another in the dual system of classification of rock strata
laid down beginning 4000 Ma to 3600 Ma (million years ago).
era. It is the first part of the Archaean Eon, preceded by the "informal" Hadean
eon, during which the Earth was considered to be essentially molten.
The International Commission on Stratigraphy
currently does not recognize the lower boundary of the era which they've provisionally placed at 4000 nor that of the preceding Hadean Eon.
The Eoarchean was followed by the Paleoarchean
era.
The name comes from two Greek
words: eos (dawn) and archaios (ancient). The first supercontinent Vaalbara
appeared around the end of this period around 3600 ma.
Some interpretations of the fossil record suggest prokaryote
forms may have evolved from protobionts late in this era.
The oldest rock formation on earth, the Isua greenstone belt
, appeared during the Eoarchean around 3.8 billion years ago.
Geologic record
The geologic record in stratigraphy, paleontology and other natural sciences refers to the entirety of the layers of rock strata — deposits laid down in volcanism or by sediment deposition of weathering detritus including all its fossil content and the information it yields about the history...
the Eoarchean erathem
Erathem
In stratigraphy, paleontology, geology, and geobiology an erathem is the total stratigraphic record deposited during a certain corresponding span of time, an era in the geologic timescale....
icon (also spelled Eoarchaean) and the Eoarchean era in the geologic timescale correspond to one another in the dual system of classification of rock strata
Stratum
In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...
laid down beginning 4000 Ma to 3600 Ma (million years ago).
Chronology
It was formerly officially unnamed and usually referred to as the first part of the Early Archean (now an obsolescent name) together with the later PaleoarcheanPaleoarchean
The Paleoarchean is a geologic era within the Archaean. It spans the period of time 3600 Ma to 3200 Ma —the period being defined chronometrically and not referenced to a specific level in a rock section on Earth. The oldest ascertained life form is from this period....
era. It is the first part of the Archaean Eon, preceded by the "informal" Hadean
Hadean
The Hadean is the geologic eon before the Archean. It started with the formation of the Earth about 4.7 Ga and ended roughly 3.8 Ga, though the latter date varies according to different sources. The name "Hadean" derives from Hades, Greek for "Underworld", referring to the "hellish"...
eon, during which the Earth was considered to be essentially molten.
The International Commission on Stratigraphy
International Commission on Stratigraphy
The International Commission on Stratigraphy , sometimes referred to by the unofficial "International Stratigraphic Commission" is a daughter or major subcommittee grade scientific daughter organization that concerns itself with stratigraphy, geological, and geochronological matters on a global...
currently does not recognize the lower boundary of the era which they've provisionally placed at 4000 nor that of the preceding Hadean Eon.
The Eoarchean was followed by the Paleoarchean
Paleoarchean
The Paleoarchean is a geologic era within the Archaean. It spans the period of time 3600 Ma to 3200 Ma —the period being defined chronometrically and not referenced to a specific level in a rock section on Earth. The oldest ascertained life form is from this period....
era.
The name comes from two Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
words: eos (dawn) and archaios (ancient). The first supercontinent Vaalbara
Vaalbara
Vaalbara is theorized to be Earth's first supercontinent, beginning its formation about , completing its formation by about and breaking up by . The name Vaalbara is derived from the South African Kaapvaal craton and the West Australian Pilbara craton...
appeared around the end of this period around 3600 ma.
Some interpretations of the fossil record suggest prokaryote
Prokaryote
The prokaryotes are a group of organisms that lack a cell nucleus , or any other membrane-bound organelles. The organisms that have a cell nucleus are called eukaryotes. Most prokaryotes are unicellular, but a few such as myxobacteria have multicellular stages in their life cycles...
forms may have evolved from protobionts late in this era.
The oldest rock formation on earth, the Isua greenstone belt
Isua greenstone belt
The Isua Greenstone Belt is an Archean greenstone belt in southwestern Greenland. The belt is aged between 3.7 and 3.8 Ga, making it among the oldest rock in the world. The belt contains variably metamorphosed mafic volcanic and sedimentary rocks...
, appeared during the Eoarchean around 3.8 billion years ago.