Ur (continent)
Encyclopedia
Ur was a supercontinent that formed (3 billion) in the early Archean
eon; the oldest continent on Earth, half a billion years older than Arctica
. Ur joined with the continents Nena
and Atlantica
about (1 billion) to form the supercontinent Rodinia
. Ur survived as a single unit until it was sundered when the supercontinent Pangaea
broke apart into Laurasia
and Gondwana
.
Ur may have been preceded by one other supercontinent, Vaalbara
, which is suggested to have formed about .
, Australia
, and India
.
In the early period of its existence, it was probably the only continent on Earth, and is considered to be a supercontinent
, even though it was probably smaller than Australia is now. When it was the only continent on Earth, all other land was in the form of small granite islands and small land-masses like Kenorland
that were not large enough to be continents.
Archean
The Archean , also spelled Archeozoic or Archæozoic) is a geologic eon before the Paleoproterozoic Era of the Proterozoic Eon, before 2.5 Ga ago. Instead of being based on stratigraphy, this date is defined chronometrically...
eon; the oldest continent on Earth, half a billion years older than Arctica
Arctica
Arctica was an ancient continent which formed approximately 2.5 billion years ago in the Neoarchean era.Arctica consisted of the Canadian and Siberian shields, and is now roughly situated in the Arctic around the current North Pole.- History :...
. Ur joined with the continents Nena
Nena (supercontinent)
Nena was an ancient minor supercontinent that consisted of the cratons of Arctica, Baltica, and East Antarctica. Forming about 1.8 billion years ago, the continent was part of the global supercontinent, Columbia. Nena is an acronym that derives from Northern Europe and North...
and Atlantica
Atlantica
Atlantica is the name given to an ancient continent that formed during the Proterozoic about from various 2 Ga cratons located in what is now West Africa and eastern South America....
about (1 billion) to form the supercontinent Rodinia
Rodinia
In geology, Rodinia is the name of a supercontinent, a continent which contained most or all of Earth's landmass. According to plate tectonic reconstructions, Rodinia existed between 1.1 billion and 750 million years ago, in the Neoproterozoic era...
. Ur survived as a single unit until it was sundered when the supercontinent Pangaea
Pangaea
Pangaea, Pangæa, or Pangea is hypothesized as a supercontinent that existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the component continents were separated into their current configuration....
broke apart into Laurasia
Laurasia
In paleogeography, Laurasia was the northernmost of two supercontinents that formed part of the Pangaea supercontinent from approximately...
and Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
.
Ur may have been preceded by one other 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...
, which is suggested to have formed about .
Formation and breakup
Rocks that made up Ur are now parts of AfricaAfrica
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
, Australia
Australia (continent)
Australia is the world's smallest continent, comprising the mainland of Australia and proximate islands including Tasmania, New Guinea, the Aru Islands and Raja Ampat Islands...
, and India
Indian subcontinent
The Indian subcontinent, also Indian Subcontinent, Indo-Pak Subcontinent or South Asian Subcontinent is a region of the Asian continent on the Indian tectonic plate from the Hindu Kush or Hindu Koh, Himalayas and including the Kuen Lun and Karakoram ranges, forming a land mass which extends...
.
In the early period of its existence, it was probably the only continent on Earth, and is considered to be a supercontinent
Supercontinent
In geology, a supercontinent is a landmass comprising more than one continental core, or craton. The assembly of cratons and accreted terranes that form Eurasia qualifies as a supercontinent today.-History:...
, even though it was probably smaller than Australia is now. When it was the only continent on Earth, all other land was in the form of small granite islands and small land-masses like Kenorland
Kenorland
Kenorland was one of the earliest supercontinents on Earth. It is believed to have formed during the Neoarchaean Era ~2.7 billion years ago by the accretion of Neoarchaean cratons and the formation of new continental crust...
that were not large enough to be continents.
Timeline
- ~3 billion years ago, Ur formed as the only continentContinentA continent is one of several very large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents—they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia.Plate tectonics is...
on EarthEarthEarth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
. - ~2.8 billion years ago, Ur was a part of the major supercontinent KenorlandKenorlandKenorland was one of the earliest supercontinents on Earth. It is believed to have formed during the Neoarchaean Era ~2.7 billion years ago by the accretion of Neoarchaean cratons and the formation of new continental crust...
. - ~2 billion years ago, Ur was a part of the major supercontinent ColumbiaColumbia (supercontinent)Columbia, also known as Nuna and Hudsonland, was one of Earth's oldest supercontinents. It was first proposed by J.J.W. Rogers and M. Santosh and is thought to have existed approximately 1.8 to 1.5 billion years ago in the Paleoproterozoic Era. Zhao et al...
. - ~1 billion years ago, Ur was a part of the major supercontinent RodiniaRodiniaIn geology, Rodinia is the name of a supercontinent, a continent which contained most or all of Earth's landmass. According to plate tectonic reconstructions, Rodinia existed between 1.1 billion and 750 million years ago, in the Neoproterozoic era...
. - ~550 million years ago, Ur was a part of the major supercontinent PannotiaPannotiaPannotia, first described by Ian W. D. Dalziel in 1997, is a hypothetical supercontinent that existed from the Pan-African orogeny about six hundred million years ago to the end of the Precambrian about five hundred and fifty million years ago. It is also known as the Vendian supercontinent...
. - ~300 million years ago, Ur was a part of the major supercontinent PangaeaPangaeaPangaea, Pangæa, or Pangea is hypothesized as a supercontinent that existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the component continents were separated into their current configuration....
. - ~208 million years ago, Ur was torn apart into parts of LaurasiaLaurasiaIn paleogeography, Laurasia was the northernmost of two supercontinents that formed part of the Pangaea supercontinent from approximately...
and GondwanaGondwanaIn paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
. - ~65 million years ago, the AfricaAfricaAfrica is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
n part of Ur was torn apart as part of India. - ~Present, Ur is part of Australia and Madagascar.