Continental Drift and Plate Tectonics PDF

36.4 A CONTINENTAL DRIFT THEORY Continental Drift Theory - Theory that continents were once part of a single landmass that broke apart and have moved to their present locations. Alfred Wegener (1880-1930) - First proposed the theory of continental drift - Found evidence...

36.4 A CONTINENTAL DRIFT THEORY Continental Drift Theory - Theory that continents were once part of a single landmass that broke apart and have moved to their present locations. Alfred Wegener (1880-1930) - First proposed the theory of continental drift - Found evidence for Pangaea “The Origin of the Continents and the Oceans” (1915) - Book that Alfred Wegener created German Translation: “Die Entstehung der Kontinente und Ozeane” WEGENER’S EVIDENCE Evidence A - Continents that seem to “fit together” like puzzle pieces Evidence B - Fossil Evidence (Fossils are remains of living things that lived long ago) Evidence C - Ancient Mountains and Rocks (Some mountain ranges on different continents seem to match) Evidence D - Paleoclimatic Evidence THE REJECTION OF THE CONTINENTAL DRIFT THEORY - Wegener’s theory was rejected by scientists because he couldn’t explain what force pushes or pulls the continents. He also couldn’t find the force that causes the continents to drift apart and because of this, he could not convince anyone and his theory was rejected. Wegener died in Greenland while he was on an expedition and at the time of his death, no one believed his hypothesis. SEA FLOOR SPREADING THEORY Harry Hess (1906-1969) - He was an American geologist and a United States Navy officer in WW2 who is considered on of the “founding fathers” of the unifying theory of plate tectonics - He developed the idea of seafloor spreading to explain the seafloor formation 1963 - Seafloor Spreading Theory 1964 - The History of Ocean Basins Seafloor Spreading Theory - How the once-joined continents had separated into the seven that exist today. - Theory that supports Wegener’s CDT Sonar (Sound Navigation And Ranging) - to map the ocean floor SEAFLOOR SPREADING EVIDENCE - A parallel pattern of rock material found at identical location on each side of the Mid-Atlantic Ridge reveals rock of the same geologic age and polarity Age of the Seafloor Mid-Ocean Ridges - Underwater mountain chains that run through the Earth’s Basins - Magma rises to the surface and solidifies and makes new crust forms - Older crust are pushed farther away from the ridge SUPPORTING EVIDENCE OF THE SST - There are active fractures in the lithosphere along the ocean floor - The age of the seafloor rock increases as you go further away from the mid-ocean ridge - The thickness of the sediment layers deposited on the seafloor increases as you go further away from the mid-ocean ridge. - Patterns of seafloor magnetism on either side of the mid-ocean ridge matches with one another 36.4 B PLATE TECTONIC THEORY Plate Tectonic Theory - Idea that the Earth’s lithosphere is broken into pieces called plates that move around the asthenosphere Convection Current - Driving force of plate tectonics in which hot, plastic-like material from the mantle rises to the lithosphere, moves horizontally, cools and sinks back to the mantle. - Convection currents provide enough energy to move the plates in the lithosphere CAUSES OF PLATE MOVEMENTS DRIVING MECHANISMS - Convection cells within the mantle - Pushing at the mid-oceanic ridges - Pulling at the subduction zones Ridge Push (Gravitational Sliding/Sliding Plate Force - Is a proposed driving force for plate motion in plate tectonics that occurs at mid-ocean ridges as the results of the rigid lithosphere sliding down the hot, raised asthenosphere below the mid-ocean ridges. Slab Pull - Is the pulling force exerted by a cold, dense oceanic plate plunging into the mantle due to its own weight. Slab Suction (Trench Suction) - occurs when a subducting slab drives flow in the lower mantle by exerting additional force down in the direction of the mantle’s convection currents.