moon’s gravity and the rotation of the Earth provide the force –Wegener: Continents plow through floor –Wegener: Seafloor Spreading Hess, 1962: Proposed that the ocean floor might be moving too (contrary •Harry to Wegener) floor moves away from the mid-atlantic ridge like a conveyer belt –Ocean 1.Ocean floor topography: technology, features in ocean floor were discovered: –Via 2.Seafloor sediments: sediment exists further from oceanic ridge –More 3.Age of Seafloor: rocks are far from ridge, younger rocks close –Older oceanic rocks are much younger than the continents --> where did the –Oldest ancient ocean floor go? must have subducted under continents •It fig 17-7, p. 450!!! –See 4.Paleomagnetism - the clincher study of ancient magnetic fields in the Earth. –The Earth’s magnetic field: compass needles and magnetic metals (e.g. iron) –Affects from solar wind. –Protects minerals can act like compass needles –Ferromagnesiam
–Wegener: moon’s gravity and the rotation of the Earth provide the force –Wegener: Continents plow through floor Seafloor Spreading •Harry Hess, 1962: Proposed that the ocean floor might be moving too (contrary to Wegener) –Ocean floor moves away from the mid-atlantic ridge like a conveyer belt 1.Ocean floor topography: –Via technology, features in ocean floor were discovered: 2.Seafloor sediments: –More sediment exists further from oceanic ridge 3.Age of Seafloor: –Older rocks are far from ridge, younger rocks close –Oldest oceanic rocks are much younger than the continents --> where did the ancient ocean floor go? •It must have subducted under continents –See fig 17-7, p. 450!!! 4.Paleomagnetism - the clincher –The study of ancient magnetic fields in the Earth. Earth’s magnetic field: –Affects compass needles and magnetic metals (e.g. iron) –Protects from solar wind. –Ferromagnesiam minerals can act like compass needles