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Continental Drift
• Alfred Wegener developed
the idea of continental
drift
• Continental drift is the
theory that continents
can drift apart from one
another and have done so
in the past
Sea-Floor Spreading
• New oceanic
lithosphere is created
as older materials are
pushed away
• mid ocean ridge in the
Atlantic ocean
Magnetic Reversals
• Earth’s magnetic poles
change
• Rock records the
direction of Earth’s
magnetic field
Plate Motion
• Ridge Push – oceanic
plate slides downward
• Convection – hot
material rises and
cooler material sinks
Plate Motion (cont.)
• Slab Pull – the sinking
oceanic plate sinks and
pull the rest of the
plate with it
Convergent Boundary
• Occurs when two
tectonic plates push into
each other
• Continental-Continental:
Mountains
• Continental-Oceanic and
Oceanic-Oceanic:
Subduction
Divergent Boundary
• When two tectonic
plates move away from
each other
• mid-atlantic ridge
Transform Boundary
• When two tectonic
plates slide past one
another
• San Andreas
Fault