1. 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

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

3. Mid-Ocean Ridges

4. 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

5. 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

6. Animation

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

8. 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

9. 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

10. Magnetic Striping and Symmetry

12. 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