Plate Tectonics

Alfred Wegener

Father of plate tectonics "badass of plate tectonics".

- Saw a fit of South America and Africa (fit = geographic distribution of similar rock types, fossils, and ancient climates).

Observed:

1) Geographic mapping/fit "puzzle piece fit"

2) Matching geologic units; sediment, patterns of rocks, etc.

3) Distribution of fossils and modern day organisms

4) Distribution of climate belts. Evidence of ancient glaciers and rocks underneath.

Pangea

Supercontinent

Continent drift caused the continents we see today.

Wegener's Problem

1) Unrealistic mechanism for driving plate motion

2) Passive role of oceanic crust

Evidence for Plate Tectonics

Variations in magnetism of seafloor rocks.

Symmetric patterns of age of seafloor crust across plate tectonic ridges.

Formation of magnetic lava crystals

Magnetic minerals crystalize in lavas and align themselves parallel to Earth's magnetic field.

Fun fact: Oldest oceanic crust is ~200 million years old

Reversals in Earth's magnetic field

Preserved in lava flows! They reveal age of seafloor crust.

Hot Spots

Reveal plate motion in relation to relatively fixed mantle plumes.

Operations of Plate Tectonics

Lithosphere

Consists of continental crust / oceanic crust and lithospheric mantle.

Asthenosphere

Weak, partially molten, capable of allowing plates to flow on it.

Divergent

Important for life on earth! Separating plates.

Convergent

Important for life on earth! Coming together of plates.

Transform

Ex. San Andreas fault.

Slab Pull

Cauases actual movement of plate tectonics