Transcript Sea Floor Spreading Expanding Earth or Plate Tectonics

Sea Floor Spreading
Expanding Earth or
Plate Tectonics
Mr. Clement Cheng
Continental Drift Theory
Objection 1
No one could explain how continents could
be moved
Objection 2
Wegener was not a physical geologists but a
climatologist.
Sea Floor Spreading
• Proposed by Hess in 1960
• New discoveries about the deep ocean floor
formulated
Evidence 1 The Mid-oceanic
Ridge
Evidence 2: Magnetic Anomaly
How are magnetic anomalies
generated?
Evidence 3: Young Ocean Floor
(JODIES)
Evidence 4: Heat Flow
Important Point to Note:
Sea-floor spreading is the
mechanism that generates
divergent plate boundaries;
creates oceanic crust and
separates continents.
1. Divergent Plate Boundaries
2. Generating Oceanic Crust
3. Leading to Continental Drift
Actual Examples
So?????
• Expanding earth
• OR
• Another mechanism for subduction zone in
order to maintain steady-state equilibrium