THE BEGINNINGS OF PLATE
TECTONICS
EARTH SCIENCE’S UNIFYING THEORY
WHAT IS A UNIFYING THEORY?
Unifying theory: a theory that explains many natural phenomena
and ties things together in an overarching way
HOW DOES IT EXPLAIN THIS?
EARTH’S STRUCTURE
• Crust – the thin relatively light
outermost layer of the earth
• Mantle – thick layer of plastic rock
beneath the crust
• Outer Core – composed of liquid
iron and nickel
• Inner Core – solid composed of iron
and nickel
OCEANIC CRUST VS. CONTINENTAL CRUST
• Oceanic Crust – thin, dense,
composed mainly of basalt
• Continental crust – thick,
composed of granite
BUOYANCY!
THE BEGINNINGS OF PLATE TECTONICS
Alfred Wegener – a German
meteorologist and polar explorer
who first proposed the theory of
continental drift.
https://www.youtube.com/watc
h?v=rDKiNwTwaNw
ALFRED WEGENER’S FINDINGS
• Evidence for continental drift:
• Continents fit together like
puzzle pieces
• Identical fossils found on
different continents
• Mountain ranges with
identical rocks found in
America and Europe
BUT HE HAD NO MECHANISM.
ALFRED WEGENER SONG
https://www.youtube.com/watch?v=T1-cES1Ekto
SEAFLOOR SPREADING – WEGENER’S MISSING
MECHANISM
• Seafloor spreading:
The theory that new ocean crust forms
at spreading centers on the ocean
floor which push the continents apart.
THE AGE OF THE SEA FLOOR
HARRY HESS
https://www.youtube.com/watch?v=G
yMLlLxbfa4
DISTRIBUTION OF EARTHQUAKES
DISTRIBUTION OF VOLCANOES
PLATE TECTONICS
PLATE BOUNDARIES
HOW DOES IT EXPLAIN THIS?
MID OCEAN RIDGE
TRENCH
ABYSSAL PLAIN
SEAMOUNTS/VOLCANIC ISLANDS