1. DEVELOPMENT OF A THEORY Page 47 of INB

2. ESSENTIAL QUESTION  Explain the evidence used to support seafloor spreading.

3. SONAR  Echo sounding technology developed during WWII used to map the ocean floor.  Showed mountains in the middle of the ocean.  Called mid-ocean ridge (MOR)

4. SEAFLOOR SPREADING  New crust forms along the MOR as older crust is pulled away.  New crust forms as pillow lava  Sediment are deposited on older rocks to make bottom smooth

7. HOW DID A COMPASS PROVE SEAFLOOR SPREADING?  Outer core of Earth creates a magnetic field  Reverses every hundred thousand to few million years

9. HOW DID A COMPASS PROVE SEAFLOOR SPREADING?  Rocks act like a compass and align with the magnetic field  Parallel patterns in the magnetic signature on both sides of the MOR

11. HOW DID A COMPASS PROVE SEAFLOOR SPREADING?  Each pair of stripes had similar composition, age, and magnetic character  This proved seafloor spreading.  Which proved the continents were moving.

12. LESSON 2-3 Seafloor Spreading Theory