Rodinia

Rodinia, the oldest known supercontinent, which formed about 1,100 million years ago and broke apart about 750 million years ago during the Proterozoic Eon of geological history. The name is derived from the Russian word meaning “motherland”. It is difficult to know whether any older continent or supercontinent might have existed because the Earth’s surface has been subject to much change since then. As a result, very few rocks representing part of the original Rodinian crust are still exposed on the Earth’s surface, although such rocks have been identified in Australia, China, Scandinavia, Africa, Greenland, North America, and the Middle East. It is very difficult to date these rocks because there are no hard-shelled fossils within them, and other methods are not so reliable on rocks of this great age. These rocks, particularly the carbonate and iron-rich sediments, indicate that atmospheric oxygen levels were rising during this time. Glacial dropstone sediments show that Earth went through an ice age just before Rodinia started to break up. About 1 billion years ago, following the formation of Rodinia by the amalgamation of Proterozoic plates, there was a major mountain-building phase called the Grenville Orogeny. Shear zones reveal that crustal extension took place later. Radiometric dates from basalts within rift zones indicate that the supercontinent split about 750 million years ago to form the Panthalassic Ocean. One of the new large crustal units became Laurentia, ancestral to present-day North America.