The time interval between 3800-2500 million years ago. The Archean is one of the Precambrian time intervals.
the first three billion years plus of life's history up to the Paleozoic
the earlier part of Precambrian time.
a term meaning ancient, which has been applied to the oldest rocks of the Precambrian. basement: a set of rocks, usually of igneous or metamorphic rock, that is overlain by younger sedimentary strata. A crustal layer beneath a sedimentary one. The ancient continental igneous rock base that lies beneath Precambrian rocks.
the time from 3,800 million years to 2,500 million years ago; earth's crust formed; unicellular organisms are earliest forms of life
used of the earliest known rocks
adjective implying conditions between 2.5 billion years ago and 4.0 billion years ago. The oldest rocks are about 4.0 billion years old defining the older boundary. The younger boundary is defined by an apparent difference in geological attributes of rocks older than 2.5 billion years and younger than 2.5 billion years. These differences may be due to our incomplete knowledge of the rock record rather than to a dramatic change in the Earth.
The period in the history of the Earth from 4000 million years ago to 2500 million years ago, part of the Precambrian. The Archean is preceeded by the Hadean and followed by the Proterozoic. The earliest fossil evidence for life on Earth appears during the Archean period.
The period in Earth's history between 2.5 billion years ago and 4.0 billion years ago.
(see Geological Timescale)
A geologic period in Earth's history marked by the emergence of life, about 3.8 billion to 2.5 billion years ago.
The period of Earth's history 3.8 to 2.4 billion years ago.
The oldest rocks of the Precambrian era, older than about 2,500 million years.
An era in geologic time covering the early part of Precambrian time.
Major eon of the Precambrian from 4.0 to 2.5 billion years ago [LCOTE
An eon of geologic time extending from about 3800 to 2500 million years ago. Derived from the Greek archaios meaning "ancient".
The earliest dated pre-cambrian rock on earth, dating from 3.8 billion years ago.
Term applied to the oldest rocks of the Precambrian, of more than 2600 million years.
The Archean (IPA: , also spelled Archaean, formerly called the Archaeozoic (IPA: ), also spelled Archeozoic) is a geologic eon before the Proterozoic, 2500 Mya(million years ago). Instead of being based on stratigraphy, this date is defined chronometrically. The lower boundary has not been officially recognized by the International Commission on Stratigraphy, but it is usually set to 3800 Mya at the end of the Hadean eon.