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Text on this page is printable and can be used according to our Terms of Service. Any interactives on this page can only be played while you are visiting our website. You cannot download interactives. These tectonic plates rest upon the convecting mantle, which causes them to move.
The movements of these plates can account for noticeable geologic events such as earthquakes, volcanic eruptions, and more subtle yet sublime events, like the building of mountains.
Teach your students about plate tectonics using these classroom resources. The theory of plate tectonics revolutionized the earth sciences by explaining how the movement of geologic plates causes mountain building, volcanoes, and earthquakes. Join our community of educators and receive the latest information on National Geographic's resources for you and your students. Skip to content. Twitter Facebook Pinterest Google Classroom. Encyclopedic Entry Vocabulary.
Continental drift describes one of the earliest ways geologist s thought continent s moved over time. Today, the theory of continental drift has been replaced by the science of plate tectonics.
The theory of continental drift is most associated with the scientist Alfred Wegener. He called this movement continental drift. Wegener, trained as an astronomer , used biology , botany , and geology describe Pangaea and continental drift. For example, fossil s of the ancient reptile mesosaurus are only found in southern Africa and South America.
Mesosaurus, a freshwater reptile only one meter 3. The presence of mesosaurus suggests a single habitat with many lakes and rivers. Wegener also studied plant fossils from the frigid Arctic archipelago of Svalbard, Norway. Alfred Wegener proposed that the continents were once united into a single supercontinent named Pangaea, meaning all earth in ancient Greek.
He suggested that Pangaea broke up long ago and that the continents then moved to their current positions. He called his hypothesis continental drift. Besides the way the continents fit together, Wegener and his supporters collected a great deal of evidence for the continental drift hypothesis.
For one, identical rocks of the same type and age are found on both sides of the Atlantic Ocean. Wegener said the rocks had formed side-by-side and that the land had since moved apart.
Mountain ranges with the same rock types, structures, and ages are now on opposite sides of the Atlantic Ocean. Wegener concluded that they formed as a single mountain range that was separated as the continents drifted. Ancient fossils of the same species of extinct plants and animals are found in rocks of the same age but are on continents that are now widely separated.
Wegener proposed that the organisms had lived side by side, but that the lands had moved apart after they were dead and fossilized. He suggested that the organisms would not have been able to travel across the oceans. For example, the fossils of the seed fern Glossopteris were too heavy to be carried so far by wind. The reptile Mesosaurus could only swim in fresh water.
Cynognathus and Lystrosaurus were land reptiles and were unable to swim. Grooves and rock deposits left by ancient glaciers are found today on different continents very close to the equator. Today glaciers only form on land and nearer the poles. Later, recovering from wounds he suffered while fighting for Germany during World War I, he developed his idea in a book, The Origin of Continents and Oceans , published in German in When it was published in English, in , the intellectual fireworks exploded.
But it was the Americans who came down hardest against continental drift. The most poignant attack came from a father-son duo. Chamberlin had launched his career with an iconoclastic attack on establishment thinking.
He went on to define a distinctly democratic and American way of doing science, according to historian Naomi Oreskes. By the s, Chamberlin was the dean of American science and his colleagues fawned that his originality put him on a par with Newton and Galileo. Rollin T. For decades afterward, older geologists warned newcomers that any hint of an interest in continental drift would doom their careers. Wegener took the assault as an opportunity to refine his ideas and address valid criticisms.
When critics said he had not presented a plausible mechanism for the drift, he provided six of them including one that foreshadowed the idea of plate tectonics.
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