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A History of the Theory of
Plate Tectonics
 German meteorologist,
geophysicist and polar researcher
 Was puzzled by how the shapes
of the continents seemed to fit
together like a jigsaw puzzle (as
others had before in history)
 After studying multiple lines of
evidence, proposed Continental
Drift Theory in 1915
• Theorized that millions of years ago the continents
were connected as a single supercontinent he called
Pangaea and separated over time to their current
positions
• Couldn’t explain the mechanism that caused the
continents to move
 Corresponding shapes of
the continental shelves
 Fossils – distribution of
extinct organisms
 Glacial geology –
evidence of glaciers in
warm regions of Earth
And now, a music video
interlude…
 1950 ‘s – More complete theory of continental movement
built on Wegener’s ideas
 New evidence to support continental drift:
 Discovery of underwater plate boundary ridges where
new crust is formed (like the Mid Atlantic Ridge)
 Paleomagnetic evidence
 Earth’s magnetic field reverses every few thousand
years
 Leaves traces in the rocks of emerging crust –
“bands” that move out from the plate boundary
 New data on global distribution of volcanoes and
earthquakes
 Convection currents in Earth’s
mantle.
 Old crust is pushed into the mantle
(subduction), melts and sinks because it’s
cooler and denser. Molten magma rises
because it’s hotter and less dense.