Plate
Tectonics
A Brief History of Plate Tectonics
1508 - Leonardo da Vinci
“Sufficient for us is the testimony of things produced in the salt waters
and now found again in the high mountains, sometimes far from the
sea.”
1596 - Abraham Ortelius : “Thesaurus Geographicus ”.
1620 - Sir Francis Bacon
1780 - Benjamin Franklin
Fossils that don’t match
present climates .
1910 - Frank B. Taylor : C. drift but weaker evidence.
1912 - Alfred Wegener : Put it all together (but no driver).
1915 - Wegener’s book “Origin of Continents and Oceans”.
1
Snider-Pellegrini’s Jigsaw Puzzle Map
(1858)
Wegner’s Pangaea Hypothesis
1. geologic column
2. fossil record
3. climate record
a. glaciers
b. corals
2
Wegner’s Fossil Evidence
Wegner’s
Glacial
Evidence
3
Fossil Coral Reef
Distribution
•If the continents didn’t drift,
then corals must have been
growing in cold, even polar,
waters! (or VERY different
climate than what we now
see.)
Fossil Coral Reefs
Range of
Modern Corals
Key Evidence since Wegner
for Plate Tectonics
1. Paleomagnetism of rocks (1940’s )
a. Curie Point = 580° C
Magma
Cooling to 700°C
Minerals Crystallize
Further Cooling to Curie Pt : 580° C
Magnetite molecules line up
Additional cooling
Atomic arrangement "frozen"
4
5
2. "polar wandering"
3. 1962 Sea-floor spreading - Harry Hess
sea-floor ridges of Atlantic
6
4. late 1960’s Vine-Matthews-Morley test of
Hess’ hypothesis
a. paleomagnetism
b. magnetic pole reversals
7
c. oceanic crust
Implications of sea-floor spreading:
Ocean crust age
8
5. Hotspots
The Hawaiian Islands and
Emperor Seamount chains
show how the Pacific Plate
has moved relative to a
stationary “hot spot”.
6. Seismic studies of earth’s crust
1. asthenosphere is ductile
2. lithosphere is rigid & strong enough to form
slabs
9
7. 1990’s Further evidence of plate
tectonics = measures of plate movement
(GPS)
Formation and Breakup of Pangaea…
10
Pangaea
Breakup of Pangaea
11
Modern continents take shape
Again…
12
Plate Margins
Plate Margins
13
Types of Plate
Margins
Mechanisms of
Plate Tectonics
14