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Alfred Wegener (1910 ) Continental Drift Continental Drift Evidence Q. 1) Who studied sea-floor spreading and when? Harry Hess (1960’s) Sea Floor Spreading Q. 2) What is sea-floor spreading? The theory that molten from mid-ocean ridges creates new crust and spreads older crust apart. Q. 3) What is subduction? When older crust is pushed into a deep-sea trench and sinks back towards the mantle. Sea Floor Spreading Evidence The next slide will walk through the evidence… 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) Evidence #1 – Molten material (what pushes crust apart) = North = North MID OCEAN RIDGE OLD NEW Sea Floor Spreading MANTLE NEW OLD Sea Floor Spreading Evidence #2 – Magnetic stripes Proves molten rock comes out of MOR. The pattern can only shift in liquid (not solid crust).