![]() Scientists did not accept Wegener’s theory of continental drift. These include Pannotia, which formed about 600 million years ago, and Rodinia, which existed more than a billion years ago. Today, scientists think that several supercontinents like Pangaea have formed and broken up over the course of the Earth’s lifespan. These pieces slowly assumed their positions as the continent we recognize today. Over millions of years, Pangaea separated into pieces that moved away from one another. By about 200 million years ago, this supercontinent began breaking up. Pangaea existed about 240 million years ago. Wegener discovered that the Appalachian Mountains of the eastern United States, for instance, were geologically related to the Caledonian Mountains of Scotland. South America and Africa were not the only continents with similar geology. The east coast of South America and the west coast of Africa seem to fit together like pieces of a jigsaw puzzle, and Wegener discovered their rock layers “fit” just as clearly. The presence of these fossils suggests Svalbard once had a tropical climate.įinally, Wegener studied the stratigraphy of different rocks and mountain ranges. These fossils were of tropical plants, which are adapted to a much warmer, more humid environment. These plants were not the hardy specimens adapted to survive in the Arctic climate. Wegener also studied plant fossils from the frigid Arctic archipelago of Svalbard, Norway. The presence of mesosaurus suggests a single habitat with many lakes and rivers. Mesosaurus, a freshwater reptile only one meter (3.3 feet) long, could not have swum the Atlantic Ocean. For example, fossils of the ancient reptile mesosaurus are only found in southern Africa and South America. Wegener, trained as an astronomer, used biology, botany, and geology describe Pangaea and continental drift. Wegener was convinced that all of Earth’s continents were once part of an enormous, single landmass called Pangaea. He called this movement continental drift. In the early 20th century, Wegener published a paper explaining his theory that the continental landmasses were “drifting” across the Earth, sometimes plowing through oceans and into each other. The theory of continental drift is most associated with the scientist Alfred Wegener. Today, the theory of continental drift has been replaced by the science of plate tectonics. ![]() In particular, it explains the Gondwanan distribution of fossils.Continental drift describes one of the earliest ways geologists thought continents moved over time. This concept explains why Earth does not expand through sea-floor spreading, why there is so little sediment accumulation on the ocean floor, and why oceanic rocks are much younger than continental rocks.įor a more detailed explanation, go to the Mountain Building section.Ĭontinental drift theory helps biogeographers to explain the disjunct biogeographic distribution of present-day life found on different continents but having similar ancestors. In effect, ocean basins are perpetually being "recycled," with the creation of new crust and the destruction of old oceanic lithosphere occurring simultaneously. As old oceanic crust is consumed at the trenches, new magma rises and erupts along the spreading ridges to form new crust. Many millions of years later, oceanic crust eventually descends at oceanic trenches in the mantle. Plate tectonics maintains that new oceanic crust continuously spreads away from mid-oceanic ridges in a conveyor-belt-like motion. Fragments drifted to where they are now located ( However, it was only during the 1960s, that the plate-tectonics theory was developed which allowed to explain the observations for large-scale motions of the Earth's lithospheric plates. In 1912, Alfred Wegener proposed that several continents had previously been one large continent, Pangaea which had broken apart.
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