Download Evidence after wegener

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