Plate Tectonics

Alfred Wegener

Published The Origin of Continents and Oceans (1915)

Father of “Continental Drift”

Evidence for Plate Tectonics

Jigsaw Fit of Continental Shelves

Mesosaurus (Late Paleozoic to Early Mesozoic)

Evidence for Plate Tectonics

Fossil Correlation Across Seas

Evidence for Plate Tectonics

Rock Correlation Across Seas

Evidence for Plate Tectonics

Rock Correlation Across Seas

Differences in Ancient Climates

Evidence for Plate Tectonics

Glacial Imprints in Rocks in Tropics

WW2 – Sonar – mapping seafloor

North Pole

South Pole

Magnetite (Fe3O4)

Minerals retain their magnetic moment when they are cooled below the Curie Temperature

Magnetic Reversals North

South

Magnetic Reversal

s Through Geologic

Time

Magnetic Polarity Time Scale established back to about 180 million yrs

Earth’s Magnetic Flux Lines

Intensity of Magnetism

N

S

Magnetic Stripes on the

Seafloor

Age of seafloor determined – led to acceptance of Plate Tectonics

15 Tectonic Plates

Tectonic Motions

Location of World’s Major Volcanoes

Lithosphere – The rigid outer layer of the Earth, including the crust and part of the upper mantle

Asthenosphere – The portion of the upper mantle below the lithosphere that is easily deformed

Subduction

The thrusting of oceanic plate into the

mantle at a plate boundary

Continent-Ocean Plate Orogeny

Juan de Fuca Plate

Mt. St. Helens, Before 1980

Ocean-Ocean Plate Orogeny

Many mountain belts are built by Ocean-Continent AND

Continent-Continent collisions.

Mountain Building (Orogenesis)

Continent-Continent Collisions

Continent-Continent Orogeny

Mt. Makalu, Nepal

Divergent plate boundaries

Birth of an Ocean at

a Divergent

Margin

Transform (or Strike-Slip) Faults

San Andreas:

A Transform Fault on Land

Hot Spots

Tectonic Motions

Convection

The transfer of heat by

the movement of

matter.

Convection Cell

Double-Layer Convection

Depressurized Melting