Evidence after wegener: seafloor spreading and PALEOMAGNETISM 2/2/17 Evidence after wegener: seafloor spreading and PALEOMAGNETISM Objective: I will elaborate on the concepts of seafloor spreading and magnetic striping, used as evidence of continental movement. Page 57

Mid-Ocean Ridges 1940’s- submarine and sonar technology discovery of a worldwide underwater mountain range named Mid-Ocean Ridge

Mid-Ocean Ridges

Age of the Seafloor Scientists used radiometric dating of ocean core samples to find the age of oceanic crust crust was younger by mid-ocean ridges and older further away from the ridge

Seafloor Spreading Harry Hess developed the idea of seafloor spreading (1962) by analyzing the ages of oceanic crust Hess proposed that: new oceanic crust was being made at cracks in the Mid-Ocean ridge called rifts older seafloor pushed away from the ridge

Animation

Missing Mechanism seafloor spreading provided evidence of how continents moved ocean crust created at Mid-Ocean Ridges and destroyed somewhere else Wegener was redeemed!

Paleomagnetism Additional evidence for seafloor spreading Earth’s magnetic field has flipped many times in history when new crust is formed, it “locks in” the current magnetic field direction of Earth normal polarity- magnetic fields that point north reverse polarity- magnetic fields that point south

Paleomagnetism scientists noticed an alternating pattern of normal and reverse polarity in oceanic rocks proved that oceanic crust is created at different times, supporting seafloor spreading

Magnetic Striping and Symmetry

Output Activity (Page 56) Using the “Process of Science Flowchart”, you will map out the scientific journey taken to develop and confirm the ideas of Continental Drift. You must include: Wegener’s scientific path The first major discovery after Wegener The evidence after Wegener All four (4) branches of the flowchart must be used. Once finished, write a detailed summary of the Process of Science used by Wegener and the scientists that followed him