Page 147 - Science Course 2 (Book 2)

Mo11-L3b: Why Plate Tectonics Move?

Rising mantle material at mid-ocean ridges creates What forces dominate plate motion?
the potential for plates to move away from the ridge
with a force called ridge push. What will scientists study next? This is a 3-D image
of seismic wave velocities from a new technique
called anisotropy.

Rising Magma

SLAB
MANTLE

Velocity of seismic wave
As a slab, or dense plate, sinks, it pulls on the rest of
the plate with a force called slab pull. SLOW FAST

SUMMARY
Why Plate Tectonics Move?

Mantle convection—the circulation of mantle
material due to density differences—drives
plate motion.
A Theory in Progress

Plate tectonics has become the unifying theory of
geology, but several unanswered questions remain.

Why is Earth the only planet in the solar system that
has plate tectonic activity?
Why do some earthquakes and volcanoes occur far
away from plate boundaries?

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