|
Ur was a supercontinent that formed (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 . 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. ==Formation and breakup== Rocks that made up Ur are now parts of Africa, Australia, and India.〔 In the early period of Ur's existence, it was probably the only continent on Earth, and as such is considered a supercontinent, though it was probably smaller than present day Australia. When Ur 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ur (continent)」の詳細全文を読む スポンサード リンク
|