Ur

Ur is a supercontinent that formed 3 billion years ago in the early Archean eon. Ur joined with the continents Nena and Atlantica about one billion years ago to form the supercontinent Rodinia. Ur survived as a single unit until it was sundered when the supercontinent Pangaea broke apart about 208 million years ago into Laurasia and Gondwana.

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

Ur may have been preceded by one other supercontinent, Vaalbara, which is suggested to have formed about 3.6 Bya (billion years ago).

History of Ur

* ~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.

References

* In the beginning, there was Ur
* Carl Zimmer, In times of Ur - The Top 100 Science Stories of 1996 - Earth's first continent, Discover, Jan, 1997