Download Seafloor Spreading Lesson

Convection
Cell
Mantle
Convection
Cell
Mantle
Magma rises up on the ocean floor where it
splits apart, this makes new ocean floor.
•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.
N
N
Magnetic iron in
the lava points
North or South.
Lava forms bands
of rocks on both
sides of the midocean ridge. They
record periods of
magnetic
reversals
Convection
Currents in the Mantle