An ancient supercontinent has been pieced together by an international team of geologists led by John Rogers, of the University of North Carolina. The giant landmass, which they have named Columbia, would have spread across the face of the Earth more than one and a half billion years ago.
Their theory is that it fragmented into smaller pieces before reassembling into another supercontinent called Rodinia. Later on, it reformed again into a huge landmass scientists now call Pangea. The researchers base their conclusions on rocks from India, East Africa and Saudi Arabia. The specimens were collected during a joint Indian and U.S. study.
?I named the supercontinent Columbia because some of the best evidence for its existence is in the Columbia River region of western North America,? says Rogers. ?Starting at about 1.8 billion years ago, all of the continents existing at that time began to collide into a single land area.?
Based on magnetic and geologic evidence, it is believed that the east coast of India became attached to western North America, with southern Australia pushed up against western Canada. Most of present South America rotated so that the western edge of Brazil aligned with eastern North America, forming a continental margin that extended into the southern edge of what is now Scandinavia. ?This formed an area that stretched about 8,000 miles from southern South America to northern Canada and was about 3,000 miles across at its widest part,? says Rogers.
The researchers say the evidence the team collected suggests Columbia began to break up about 1.5 billion years ago, and its fragments then moved around the Earth independently for several hundred million years. About a billion years ago, the fragments came together again to form a new supercontinent, called Rodinia.
This lasted until about 700 million years ago, before it too broke into several fragments. Scientists think these chunks moved around independently until about 250 million years ago, when yet another supercontinent emerged, now called Pangea. This began to break up almost immediately to form the world?s present continents.
In 1912, German meteorologist Alfred Wegener first put forward the theory of continental drift to describe the movement of major landmasses across the surface of the planet. At first, skeptics criticized him cruelly, but his theory later became accepted and is now known as plate tectonics, which says that continents move extremely slowly, like pieces of a puzzle, squeezing together and pulling apart to form oceans and landmasses of various sizes. Movements deep within the Earth drive this process, although the exact mechanism is still unknown.
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To see images of Columbia and Pangea, click here.
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