Akilia island
Encyclopedia
Akilia Island is an island in southwestern Greenland
, about 22 kilometers south of Nuuk
(Godthåb), at 63.933°N 51.667°W. Akilia is the location of a rock formation that has been proposed to contain the oldest known sedimentary rock
s on Earth,
and perhaps the oldest evidence of life on Earth
.
supracrustal sequence located at the south-western tip of the island. The sequence has been dated as no younger than 3.85 billion years old - that is, in the Hadean
eon - based on the age of an igneous band that cuts the rock.
The supracrustal sequence contains layers rich in iron
and silica
, which are variously interpreted as banded iron formation
, chemical sediments from submarine hot springs, or hydrothermal
vein deposits. Carbon
in the rock, present as graphite
, shows low levels of carbon-13
,
which may suggest an origin as isotopically
light organic matter derived from living organisms.
However, this interpretation is complicated because of high-grade metamorphism
that affected the Akilia rocks after their formation. The sedimentary origin, age and the carbon content of the rocks have been questioned.
If the Akilia rocks do show evidence of life by 3.85 Ga, it would challenge models which suggest that Earth would not be hospitable to life at this time. Research is ongoing.
Greenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...
, about 22 kilometers south of Nuuk
Nuuk
Nuuk, is the capital of Greenland, the northernmost capital in North America and the largest city in Greenland. Located in the Nuup Kangerlua fjord, the city lies on the eastern shore of the Labrador Sea and on the west coast of Sermersooq. Nuuk is the largest cultural and economic center in...
(Godthåb), at 63.933°N 51.667°W. Akilia is the location of a rock formation that has been proposed to contain the oldest known sedimentary rock
Sedimentary rock
Sedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution....
s on Earth,
and perhaps the oldest evidence of life on Earth
Life on Earth
Life on Earth: A Natural History by David Attenborough is a television natural history series made by the BBC in association with Warner Bros. and Reiner Moritz Productions...
.
Geology
The rocks in question are part of a metamorphosedMetamorphism
Metamorphism is the solid-state recrystallization of pre-existing rocks due to changes in physical and chemical conditions, primarily heat, pressure, and the introduction of chemically active fluids. Mineralogical, chemical and crystallographic changes can occur during this process...
supracrustal sequence located at the south-western tip of the island. The sequence has been dated as no younger than 3.85 billion years old - that is, in the 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 - based on the age of an igneous band that cuts the rock.
The supracrustal sequence contains layers rich in iron
Iron(II) oxide
Iron oxide, also known as ferrous oxide, is one of the iron oxides. It is a black-colored powder with the chemical formula . It consists of the chemical element iron in the oxidation state of 2 bonded to oxygen. Its mineral form is known as wüstite. Iron oxide should not be confused with rust,...
and silica
Silicon dioxide
The chemical compound silicon dioxide, also known as silica , is an oxide of silicon with the chemical formula '. It has been known for its hardness since antiquity...
, which are variously interpreted as banded iron formation
Banded iron formation
Banded iron formations are distinctive units of sedimentary rock that are almost always of Precambrian age. A typical BIF consists of repeated, thin layers of iron oxides, either magnetite or hematite , alternating with bands of iron-poor shale and chert...
, chemical sediments from submarine hot springs, or hydrothermal
Hydrothermal circulation
Hydrothermal circulation in its most general sense is the circulation of hot water; 'hydros' in the Greek meaning water and 'thermos' meaning heat. Hydrothermal circulation occurs most often in the vicinity of sources of heat within the Earth's crust...
vein deposits. Carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
in the rock, present as graphite
Graphite
The mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek γράφω , "to draw/write", for its use in pencils, where it is commonly called lead . Unlike diamond , graphite is an electrical conductor, a semimetal...
, shows low levels of carbon-13
Carbon-13
Carbon-13 is a natural, stable isotope of carbon and one of the environmental isotopes. It makes up about 1.1% of all natural carbon on Earth.- Detection by mass spectrometry :...
,
which may suggest an origin as isotopically
Stable isotope
Stable isotopes are chemical isotopes that may or may not be radioactive, but if radioactive, have half-lives too long to be measured.Only 90 nuclides from the first 40 elements are energetically stable to any kind of decay save proton decay, in theory...
light organic matter derived from living organisms.
However, this interpretation is complicated because of high-grade metamorphism
Metamorphism
Metamorphism is the solid-state recrystallization of pre-existing rocks due to changes in physical and chemical conditions, primarily heat, pressure, and the introduction of chemically active fluids. Mineralogical, chemical and crystallographic changes can occur during this process...
that affected the Akilia rocks after their formation. The sedimentary origin, age and the carbon content of the rocks have been questioned.
If the Akilia rocks do show evidence of life by 3.85 Ga, it would challenge models which suggest that Earth would not be hospitable to life at this time. Research is ongoing.