Earth Science Chapter 1 - Earth Science ES 121 Chapter 1...

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Earth Science ES 121 Chapter 1 Plate Tectonics Alfred Wegener is credited with developing the hypothesis of continental drift. Wegener proposed that all of the continents were originally united in a single supercontinent that he named Pangaea. One of the most compelling pieces of evidence for a supercontinent is Mesosaurus Mesosaurus , a freshwater reptile, is found only in Permian-aged rocks of Brazil and South Africa. Lystrosaurus and Cynognathus are land-dwelling reptiles that occur only in Triassic deposits of Gondwanaland. The primates of Madagascar are more similar to those of India than those of Africa The Australian marsupials are related to the American opossum, but later evolved independently from the placental mammals of the Americas. The Glossopteris flora occurs in rocks of similar age in India, Australia, Africa, Antarctica and South America. Some mountain ranges, such as the Appalachians, seemingly end at the coastline of one continent only to continue on another continent across the ocean There is extensive evidence of glaciation in rocks of Late Paleozoic age in the southern continents. The striations indicate that the glaciers radiated out from a central location. One of the main problems most geologists had with the continental drift hypothesis was that they could not understand how continental crust could move through oceanic crust As a naval captain, Harry Hess had made many geophysical measurements of the sea floor. Hess suggested that seafloor separates at mid-ocean ridges where upwelling magma forms new crust. By 1968, these developments led to the acceptance of plate tectonics. Earth’s lithosphere is broken into pieces called plates. Oceanic crust is much thinner than continental crust. The lithosphere rides on the asthenosphere, which is weak. This weak asthenosphere allows Earth’s rigid lithosphere to move. The tectonic plates of Earth. Movement is in cm/yr.
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