1. Alfred Wegener (1910 ) Continental Drift

2. Continental Drift Evidence

3. Harry Hess (1960’s) Sea Floor Spreading
Q. 1) Who studied sea-floor spreading and when?
Harry Hess (1960’s) Sea Floor Spreading

4. Q. 2) What is sea-floor spreading?
The theory that molten from mid-ocean ridges creates new crust and spreads older crust apart.

5. Q. 3) What is subduction?
When older crust is pushed into a deep-sea trench and sinks back towards the mantle.

6. Sea Floor Spreading Evidence
The next slide will walk through the evidence…

7. Harry Hess’s Sea Floor Spreading
Evidence #3 – Drilling Samples
Shows the age of crust is younger beside MOR –
proves new crust is added (& pushes sea-floor apart)
= North
Evidence #1 – Molten material
(what pushes crust apart)
MID OCEAN RIDGE
OLD
NEW
Sea Floor Spreading
MANTLE
Evidence #2 – Magnetic stripes
Proves molten rock comes out of MOR. The pattern can only shift in liquid (not solid crust).