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Continental Drift Theory and
Plate Tectonics
Continental Drift Theory
• Proposed in 1912 by
• Theory - 200 million years
ago the Earth was one
giant continent called
• From this one continent
today's continents broke
apart and drifted into their
current locations.
• How did Wegener
support his theory?
Support For Continental Drift
• The Shapes Match
• The continents look as if they were pieces
of a giant jigsaw puzzle
• The Plants and Animals Match
• Identical fossil species along the coastal
parts of Africa and South America.
• Rocks Match - These broad belts match
when the end of the continents are joined.
Clues from the Ocean on
Continental Drift
• According to scientists, how does lava get
to the ocean floor?
• How do scientists explain why ocean floor
is older farther away from the mid ocean
Why Few People Believed
• It was difficult to conceive that large
continents could plow through the sea
floor to move to new locations.
• What kind of forces could be strong
enough to move such large masses of
solid rock over such great distances?
Theory of Plate Tectonics
• The theory of plate tectonics states that
the Earth's outer shell is not one solid
sheet of rock but a series of large and
small moving plates.
• What did scientists realize when they
“connected the dots?”
What is a Tectonic Plate?
• A tectonic plate is a
massive, irregularly
shaped slab of solid
• Plate size can vary
greatly, from a few
hundred to thousands
of kilometers across
How do the Plates Move?
• No one knows for
sure but most think
that the plate driving
force is the slow
movement of hot,
softened mantle that
lies below the rigid
How do plates affect us?
Natural Disasters such as:
Volcanoes (Ring of Fire)
In Conclusion….
• What have we learned today?