* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Seafloor Spreading and Paleomagnetism
Survey
Document related concepts
Ocean acidification wikipedia , lookup
Post-glacial rebound wikipedia , lookup
Ionospheric dynamo region wikipedia , lookup
Geomagnetic reversal wikipedia , lookup
Geochemistry wikipedia , lookup
Hotspot Ecosystem Research and Man's Impact On European Seas wikipedia , lookup
Deep sea community wikipedia , lookup
Magnetotellurics wikipedia , lookup
History of geology wikipedia , lookup
History of navigation wikipedia , lookup
Oceanic trench wikipedia , lookup
Marine habitats wikipedia , lookup
Physical oceanography wikipedia , lookup
Large igneous province wikipedia , lookup
Geological history of Earth wikipedia , lookup
Transcript
Seafloor Spreading and Paleomagnetism Science Haters • Other scientists rejected Wegener’s hypothesis because he couldn’t explain what was causing the continents to move • Wegener suggested rotation of the Earth, but physicists said no • Wegener also thought the continents plowed through ocean floor but there was no evidence for that •Read pgs. 448-454 in blue book •Jot down the big ideas about “Seafloor Spreading” and “Paleomagnetism” on worksheet Holmes and Hess -proof for Wegener’s theory. Arthur Holmes in the 1940s-1950s: Seafloor spreading: new ocean crust is formed at ocean ridges and destroyed at deep sea trenches. Holmes proposed plate motion is thought to be caused by thermal convection currents in the asthenosphere. Convection Currents & Plate Motion Since the hotter material deep in the asthenosphere is less dense it slowly rises. As it reaches the base of the lithosphere it begins to cool, become more dense, and begins to sink. Rising convection currents will move plates apart (divergent). Sinking convection currents will move plates together (convergent). Plate Boundaries & Convection Currents Convergent Boundary Divergent Boundary Convection Currents in Mantle Subduction Zone: When one plate sinks beneath another. Seafloor Spreading – new ocean crust is formed at ocean ridges and destroyed at deep sea trenches. http://education.sdsc.edu/optiputer/flash/seafloorspread.htm Harry Hess – 1940s1960s: Used paleomagnetism and seafloor mapping to prove convection is a source for ‘continental drift’ Then came the Magnetometer. This could detect small changes in the magnetic field in rocks and map them. As new crust is created the iron bearing minerals point to where the magnetic pole is at that time. This is called Paleomagnetism Mid-Ocean Ridge This proved that new sea floor was being created at midocean ridges. Thus, the plates were moving. http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/p_paleomag.html