Sea-Floor Spreading Notes Plate Tectonics

Tectonic Plate Boundary Review:

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.

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

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

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

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.

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

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

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