Re: Why isn't Rodinia called Pangaea any more?

Rodinia and Pangea were two different supercontinents, rather than two different names for the same supercontinent. They were both formed from some of the same continental fragments, but they formed at different periods in time. The information below was obtained from Dr. Christopher Scotese's excellent website on plate motions, called "The Paleomap Project". Dr. Scotese is one of the world's leading researchers on paleogeopgraphy (the study of the ancient positions of different land masses and their characteristics). Go to the web site at :

http://www.cscotese.com/earth.htm

and click on the links to the different times and look at the maps then click on the link to "More Info" in the upper left of each screen.

Rodinia was a supercontinent formed about 1100 million years ago (that's 1,100,000,000 years). 750 million years ago, Rodinia broke into three pieces that drifted apart as a new ocean formed between the pieces. Then, about 600 million years ago, those pieces came back together with a big crunch known as the Pan-African orogeny (mountain building event). This formed a new supercontinent, with the name of Pannotia. By about 550 million years ago, Pannotia was breaking up into several small fragments, Laurentia (the core of what is now North America), Baltica (northern Europe), and Siberia, among others, and one very large piece. This large piece, containing what would become China, India, Africa, South America, and Antarctica, was called Gondwana. It is considered a supercontinent in its own right because it is so big, but it is only part of the earlier supercontinents. Over the next 200 million years many of the small pieces came together to form another large continent called Laurasia. Laurasia and Gondwana joined approximately 275 million years ago to form the supercontinent of Pangea. The breakup of Pangea is still going on today and contributes in the formation of the Atlantic Ocean. Eventually a new supercontinent will form and then it will break apart and so on.

As you can see, the earth's continents have seen a lot of action over time. There were probably some supercontinents formed in the 4300 million years of earth's history that came before Rodinia was formed, however, we have a much harder time understanding the history of rocks that old because there were not very many life forms to help determine the age of the rocks and because so much has happened to the rocks since they formed that the record of the original events is not very clear any more (imagine that five different people each taped over different parts of your favorite video and then from the little pieces that were left of the original, you had to go back and try to put the whole story together - geologists who do this work are a lot like detectives.

I hope this is helpful and that you post more of your questions.

Davis Smith, Ph.D., La Salle University, Philadelphia, PA