Ur (continent)

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Ur was a supercontinent that formed 3,000 million years ago (3 billion) in the early Archean eon; perhaps the oldest continent on Earth, half a billion years older than Arctica, but it may have been preceded by one other supercontinent, Vaalbara, which is suggested to have formed about 3,600 to 3,100 million years ago.1 Ur joined with the continents Nena and Atlantica about 1,000 million years ago (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.2

Formation and breakup

Rocks that made up Ur are now parts of Africa, Australia, and India.2

In the early period of Ur's existence, it was probably the only continent on Earth. Thus Ur is considered to be a supercontinent, even though it was probably smaller than Australia is now. Current day New Zealand has a vague resemblance to Ur, but rotated 90 degrees out of phase, and is about 1000 km too far South. When Ur was the only continent on Earth, all other land was in the form of small granite islands and small land-masses like Kenorlanddubious that were not large enough to be continents.

Timeline

  • ~3 billion years ago, Ur formed as the only continent on Earth.
  • ~2.8 billion years ago, Ur was a part of the major supercontinent Kenorland.
  • ~2 billion years ago, Ur was a part of the major supercontinent Columbia.
  • ~1 billion years ago, Ur was a part of the major supercontinent Rodinia.
  • ~550 million years ago, Ur was a part of the major supercontinent Pannotia.
  • ~300 million years ago, Ur was a part of the major supercontinent Pangaea.
  • ~208 million years ago, Ur was torn apart into parts of Laurasia and Gondwana.
  • ~65 million years ago, the African part of Ur was torn apart as part of India.
  • ~Present, Ur is part of Australia and Madagascar.

Notes

References

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