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/watch?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=GyMLlLxbfa4

DISTRIBUTION OF EARTHQUAKES

DISTRIBUTION OF VOLCANOES

PLATE TECTONICS

PLATE BOUNDARIES

HOW DOES IT EXPLAIN THIS?

MID OCEAN RIDGE

TRENCH

ABYSSAL PLAIN

SEAMOUNTS/VOLCANIC ISLANDS