DEVELOPMENT OF A THEORYPage 47 of INB

ESSENTIAL QUESTION

Explain the evidence used to support seafloor spreading.

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)

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

HOW DID A COMPASS PROVE SEAFLOOR SPREADING?Outer core of Earth creates a magnetic field

Reverses every hundred

thousand to few million years

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

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.

LESSON 2-3

Seafloor Spreading Theory