Download SEA-FLOOR SPREADING & SUBDUCTION

SEA-FLOOR SPREADING
&
SUBDUCTION
SEA-FLOOR SPREADING
MID-OCEAN RIDGE
OCEANIC CRUST
OCEANIC CRUST
MOLTEN
MATERIAL
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Where two plates move AWAY from each
other, sea-floor spreading occurs.
Molten material rises through the midocean ridge. (caused by convection
currents rising in the mantle.)
As it rises it pushes the older oceanic crust
out of the way.
When the molten material cools, it
hardens into brand new oceanic crust.
This process is constantly, but very slowly,
adding more ocean floor at the M.O.R as it
pushes the older crust away.
SUBDUCTION
DEEP OCEAN
TRENCH
CONTINENTAL
CRUST
OCEANIC CRUST
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Where two plates are moving towards each
other, subduction occurs.
As new ocean floor is being made at the
M.O.R., the older ocean floor is getting
pushed away.
When the more dense OCEANIC crust
collides with the less dense CONTINENTAL
crust, the oceanic sinks below the
continental forming a deep ocean trench.
The oceanic crust that sinks back into the
mantle heats up and become molten
material again.
This process is constantly happening very
slowly, and has been for millions of years.