1. Sea-Floor Spreading Notes
Plate Tectonics

2. Tectonic Plate Boundary Review:

3. 1. What is Seafloor Spreading?
A process that forms new seafloor.
Magma rises up on the ocean floor where it splits apart, this makes new ocean floor.

4. Seafloor Spreading occurs at mid-ocean ridges.
These are divergent boundaries.

5. Label: subduction zone, divergent boundary
Convection Cell
Convection Cell
Mantle
Mantle

7. 2. Where is the youngest oceanic crust located?
In the center of the ridge...

8. The youngest oceanic crust is in the center at mid oceanic ridges.
The older oceanic crust is near the continents at subduction zones.
The ages of the ocean floor “mirror” each other from the center.

9. Does the center of the ridge always show the current magnetic orientation of the north and south poles?
Yes, the current magnetic orientation is indicated at the center.
But, in the past, our compass needles pointed to the magnetic South, before that they pointed to the magnetic North
this is a cycle.
Magnetic iron in the lava points North or South. Lava forms bands of rocks on both sides of the mid-ocean ridge. They record periods of magnetic reversals N N

10. On the figure to the left, Label the magnetic orientations (North or South) on the bands of rocks along the mid ocean ridge
Label where the youngest and oldest oceanic crust is located

14. Identify the features/events
Convection current
Plate moving away from ridge
Plate is subducting OR subduction zone
Trench forming
Ridges forming at divergent boundary
Magma moving up
Volcano forming at subduction zone