Additional reporting by Alina Bradford, Live Science contributor.Anne M. 14, 2021, by Live Science Staff Writer Patrick Pester. Watch this short video on YouTube about plate tectonics and continental drift, from National Geographic (opens in new tab).Learn more about Alfred Wegener from the NASA Earth Observatory (opens in new tab).Learn more about the history of continental drift and plate tectonics from the U.S.He died in 1930 at age 50 just two days after his birthday while on a scientific expedition in Greenland (opens in new tab), according to the University of Berkeley (opens in new tab). Despite his incredible continental drift evidence, Wegener never lived to see his theory gain wider acceptance. In fact, plates moving together created the highest mountains in the world, the Himalayans, and the mountains are still growing due to the plates pushing together, even now, according to National Geographic (opens in new tab). For example, the Appalachian Mountains (United States) and Caledonian Mountains (Scotland) fit together, as do the Karoo strata in South Africa and Santa Catarina rocks in Brazil. He also matched up rock formations on either side of the Atlantic Ocean like puzzle pieces. Wegener knew that fossil plants and animals such as mesosaurs (opens in new tab), a freshwater reptile found only in South America and Africa during the Permian period, could be found on many continents. Wegener then assembled an impressive amount of continental drift evidence to show that Earth's continents were once connected in a single supercontinent. He was intrigued by the interlocking fit of Africa's and South America's shorelines. Tectonic plates of the Earth (Image credit: USGS) (opens in new tab)Ī map of the continents inspired Wegener's quest to explain Earth's geologic history. Related: Plate tectonics are 3.6 billion years old, oldest minerals on Earth reveal (opens in new tab) What evidence is there for continental drift? Magnetic (opens in new tab) minerals aligned in ancient rocks on continents also showed that the continents have shifted relative to one another. Alternating patterns of magnetic anomalies on the ocean floor indicated seafloor spreading (opens in new tab), where new plate material is born. In the 1960s, scientists discovered plate edges through magnetic surveys of the ocean floor and through the seismic listening networks built to monitor nuclear testing, according to Encyclopedia Britannica (opens in new tab). Plate tectonics is like a modern update to continental drift. For instance, as geophysicists began to realize that continental rocks were too light to sink down to the ocean floor, prominent paleontologists instead wrongly suggested that the similarities between fossils had been overestimated, Frankel said. Researchers argued over the land bridges right up until the plate tectonics theory was developed from the 1950s to the 1970s, Frankel said. And to account for the identical fossils discovered on continents such as South America and Africa, scientists invoked ancient land bridges, now vanished beneath the sea. They thought Earth's incredible mountains were created because our planet had been cooling and shrinking since its formation, Frankel said. When Wegener proposed continental drift, many geologists were contractionists.
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