Possible Causes of Tectonic
Plate Motion
Tectonic vs. Lithospheric Plates
• A tectonic plate is a piece of lithosphere
that moves around on top of the
asthenosphere.
Tectonic vs. Lithospheric Plates
• A lithospheric plate is a piece of
lithosphere that moves around on top of
the asthenosphere.
Tectonic vs. Lithospheric Plates
• How are tectonic and lithospheric plates
different?
– THEY ARE NOT!
– Different names for the same thing!
Three Possible Driving Forces
• Convection
• Slab Pull
• Ridge Push
Convection
• Hot, less dense material rises while cooler,
more dense material sinks.
• The hot material cools and the cool
material warms up and the cycle
continues.
• As the mantle moves, tectonic plates are
dragged sideways.
• Occurs in the mantle
Slab Pull
• Oceanic lithosphere is more dense than
the asthenosphere.
• When the edge of the oceanic plate sinks,
the rest of the plate is pulled with it.
• Occurs at subduction zones
Ridge Push
• Oceanic lithosphere is higher at the ridge
than where it sinks beneath continental
lithosphere.
• Oceanic plates slide down the lithosphereasthenosphere boundary during ridge
push.
• Occurs at divergent boundaries
How far do they move?
• Tectonic plates move just centimeters per
year