1. SEAFLOOR SPREADING Atlantic Getting Bigger B40b

2. SEAFLOOR SPREADING Idea that the ocean bottom is getting larger. Atlantic Ocean Proposed by Harry Hess Evidence in rocks on ocean floor.

3. MID-ATLANTIC RIDGE mid-ocean ridge found running down center of Atlantic Ocean series of mountains on either side

4. ROCK AGES 1 - youngest rocks nearest the ridge oldest rocks next to continents identical pattern on both sides THEREFORE: new rocks are forming (B3, Figure 9)

5. 2 - oldest rocks on ocean floor = 200 million years old oldest rocks on continents = 4.6 billion years old THEREFORE: new rocks are forming (B3, Figure 9)

6. MAGNETIC REVERSAL INDICATORS rocks on ocean bottom reflect earth’s magnetic reversals THEREFORE: new rocks areforming (B3, Figure 10)

7. ASSIGNMENT Draw a section of the ocean floor and mantle flanking the mid-Atlantic ridge. Use different colors to represent different rock ages. Label: mid-Atlantic ridge and direction of plate movement.