The "
early Earth" is a term usually defined as
EarthEarth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density...
's first billion years, or
gigayearA year is the amount of time it takes the Earth to make one revolution around the Sun...
. On the
geologic time scaleThe geologic time scale is a chronologic schema relating stratigraphy to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth...
, the "early Earth" comprises all of the
HadeanThe Hadean is the geologic eon before the Archean. It started at Earth's formation about 4.6 billion years ago , and ended roughly 3.8 billion years ago, though the latter date varies according to different sources. The name "Hadean" derives from Hades, Greek for "Underworld," referring to the...
eon (itself unofficially defined), as well as the
EoarcheanIn the geologic record the Eoarchean erathem 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 .It was formerly officially unnamed and usually referred to as the first part of the...
and part of the
PaleoarcheanThe 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...
eras of the
ArcheanThe Archean is a geologic eon before the Proterozoic and Paleoproterozoic, before 2.5 Ga . Instead of being based on stratigraphy, this date is defined chronometrically...
eon.
This period of
Earth's historyThe history of the Earth describes the most important events and fundamental stages in the development of the planet Earth from its formation to the present day during the last 4.54 billion years. Nearly all branches of natural science have contributed to the understanding of the main events of the...
, being its earliest, involved the planet's condensation from a
solar nebulaIn cosmogony, the nebular hypothesis is the most widely accepted model explaining the formation and evolution of the Solar System. It was first proposed in 1734 by Emanuel Swedenborg. Originally applied only to our own Solar System, this method of planetary system formation is now thought to be at...
and accretion from
meteoriteA meteorite is a natural object originating in outer space that survives an impact with the Earth's surface. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...
s, as well as the formation of the earliest
atmosphereThe Earth's atmosphere is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
and
hydrosphereA hydrosphere in physical geography describes the combined mass of water found on, under, and over the surface of a planet....
.
The "
early Earth" is a term usually defined as
EarthEarth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density...
's first billion years, or
gigayearA year is the amount of time it takes the Earth to make one revolution around the Sun...
. On the
geologic time scaleThe geologic time scale is a chronologic schema relating stratigraphy to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth...
, the "early Earth" comprises all of the
HadeanThe Hadean is the geologic eon before the Archean. It started at Earth's formation about 4.6 billion years ago , and ended roughly 3.8 billion years ago, though the latter date varies according to different sources. The name "Hadean" derives from Hades, Greek for "Underworld," referring to the...
eon (itself unofficially defined), as well as the
EoarcheanIn the geologic record the Eoarchean erathem 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 .It was formerly officially unnamed and usually referred to as the first part of the...
and part of the
PaleoarcheanThe 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...
eras of the
ArcheanThe Archean is a geologic eon before the Proterozoic and Paleoproterozoic, before 2.5 Ga . Instead of being based on stratigraphy, this date is defined chronometrically...
eon.
This period of
Earth's historyThe history of the Earth describes the most important events and fundamental stages in the development of the planet Earth from its formation to the present day during the last 4.54 billion years. Nearly all branches of natural science have contributed to the understanding of the main events of the...
, being its earliest, involved the planet's condensation from a
solar nebulaIn cosmogony, the nebular hypothesis is the most widely accepted model explaining the formation and evolution of the Solar System. It was first proposed in 1734 by Emanuel Swedenborg. Originally applied only to our own Solar System, this method of planetary system formation is now thought to be at...
and accretion from
meteoriteA meteorite is a natural object originating in outer space that survives an impact with the Earth's surface. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...
s, as well as the formation of the earliest
atmosphereThe Earth's atmosphere is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
and
hydrosphereA hydrosphere in physical geography describes the combined mass of water found on, under, and over the surface of a planet....
. It was also defined by the
emergence of lifeThis timeline of the evolution of life outlines the major events in the development of life on the planet Earth . For a thorough explanatory context, see the history of Earth, and geologic time scale...
and, later,
photosynthesisPhotosynthesis is a process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of Bacteria, but not in Archaea...
. The earliest supracrustals (such as the
Isua greenstone beltThe Isua greenstone belt is an Archean greenstone belt in southwestern Greenland dated at 3.8-3.7 Ga and contains the oldest known, well preserved, metavolcanic , metasedimentary and sedimentary rocks on Earth...
) date from the latter half of this period, about 3.8
gyaIn astronomy, geology, and paleontology, Gya is often used as an unit of time to denote length of time before the present. Specifically, one Gya is equal to 109 years ago....
, around the same time as peak
late heavy bombardmentThe Late Heavy Bombardment is a period of time approximately 3.8 to 4.1 billion years ago during which a large number of impact craters are believed to have formed on the Moon, and by inference on Earth, Mercury, Venus, and Mars as well...
.