UNIVERSITY OF SOUTH ALABAMA
Today’s Agenda
MAS 603: Geological Oceanography
Lecture 1: Introductions;
Geological Thinking
Today’s Agenda
Syllabus
A) Introductions
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Syllabus (assessment etc.)
Additional subject material (student choice)
Introduction to geology and plate tectonics
Syllabus
Syllabus
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Syllabus
Syllabus
Syllabus
Class Website
http://www.southalabama.edu/geology/haywick
http://www.southalabama.edu/geology/haywick
Lecture 1: Geological Thinking
Geological Thinking
First “geologists” date back to the days of early hominids
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Clever thinkers:
AD 79
Pliny the Younger: first documented Geological report (eruption
of Mt. Vesuvius in AD 79
Clever thinkers:
1638-1687
Clever thinkers:
1658
Archbishop James Ussher: determined the age of the Earth using
biblical criteria
Clever thinkers:
1671-1743
unconformity
One of Hutton’s water colour cross-sections
Nicholas Steno: Principles of Superposition, Original Horizontality
and Lateral Continuity
James Hutton: The Father of Geology and the originator of “Uniformitarianism”
Clever thinkers:
1769-1839
Clever thinkers:
1769-1839
Affectionately called “The Map”
William “Strata” Smith: the Father of Stratigraphy (and English Geology)
William “Strata” Smith: the Father of Stratigraphy (and English Geology)
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Clever thinkers:
1797-1875
Charles Lyell: Wrote Principles of Geology.
Clever thinkers:
1809-1882
Clever thinkers:
1809-1882
Charles Darwin: formations of atolls and evolution
Clever thinkers:
1824-1907
Charles Darwin: formations of atolls and evolution
Lord Kelvin: determined the age of the Earth based upon how
long it took to cool a canon ball (20-40 million years).
Clever thinkers:
The Earth
Alfred Wegener: continental drift and the concept of Pangaea
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The Earth
Wegener’s hypothesis:
Even back in the 1700’s, mariners
commented on the apparent jigsaw puzzle
fit of South American and Africa.
His supporting evidence?
300 million years ago, the continents were all grouped together
into a “supercontinent” he called Pangaea
And the reaction?
Matching rock types and
fossils*
* types and ages
And the reaction?
Mountain Building Before Plate Tectonics
…Widespread Rejection
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Mountain Building Before Plate Tectonics
Redemption would eventually occur for
Wegener
1) Expanding Earth
2) Contracting Earth
3) Worlds in Collision (Velikovsky)
4) Lateral Accretion
Redemption would eventually occur for
Wegener
…after World War II
The Plate Tectonics Revolution
The Plate Tectonics Revolution
Technological developments during the war increased
our understanding of the world’s oceans.
The Plate Tectonics Revolution
And the single most important piece of
evidence for plate tectonics was also
discovered around the end of WWII…
Radar, sonar, and depth sounding revealed that the ocean
bottoms were not flat planes
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The Plate Tectonics Revolution
The Plate Tectonics Revolution
And the single most important piece of
evidence for plate tectonics was also
discovered around the end of WWII…
Earth has a
magnetic field
…. Paleomagnetism
(and it isn’t
constant)
The Plate Tectonics Revolution
The Plate Tectonics Revolution
Older lava flows
(1 million years)
magnetic field
1669 lava flow
magnetic field
(same as today +/declination shifts)
Reversed compared
to today
Mt Etna eruption of 1669
Mt Etna eruption of 1669
Source: http://boris.vulcanoetna.com/gifs/image/Etna1669a.jpg
Source: http://boris.vulcanoetna.com/gifs/image/Etna1669a.jpg
The Plate
Tectonics
Revolution
Paleomagnetism shows that
the ocean floor youngest near
the ridges and oldest near the
continents
Paleomagnetism
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The Plate Tectonics Revolution
The outer part of the Earth is broken up into several large
tectonic plates
The Plate Tectonics Revolution
The Plate Tectonics Revolution
And where they “rub” against one another, you get…
Earthquakes
The Plate Tectonics Revolution
http://shadow.eas.gatech.edu/~anewman/classes/geodynamics/misc/Worldmap.gif
…Volcanoes (active, dormant and extinct)
…and mountain belts
The Plate Tectonics Revolution
The Plate Tectonics Revolution
1963-1968 J. Tuzo Wilson was the first to
describe global tectonics in terms of rigid
surface "plates“, and recognized ocean
evolution (“Wilson Cycle”).
1963-1968 J. Tuzo Wilson was the first to
describe global tectonics in terms of rigid
surface "plates“, and recognized ocean
evolution (“Wilson Cycle”).
He characterized three basic plates boundaries
He characterized three basic plates boundaries
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The Earth
So how does it all work?
Internal “guts”
of the Earth
Internal “guts”
of the Earth
Four Major “Geophysical” Layers
Internal “guts”
of the Earth
Four Major “Geophysical” Layers
1) The Crust (5-35 km thick; rigid rock)
Internal “guts”
of the Earth
Four Major “Geophysical” Layers
1) The Crust
2) The Mantle (2865 km; rigid to ductile rock)
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Internal “guts”
of the Earth
Internal “guts”
of the Earth
Four Major “Geophysical” Layers
1) The Crust
2) The Mantle
3) The Outer Core (2200 km; liquid metal)
Four Major “Geophysical” Layers
1) The Crust
2) The Mantle
3) The Outer Core
4) The Inner Core (1270 km; solid metal)
More History of the Theory of Plate Tectonics
1928 - British geologist Arthur Holmes proposed that
convection currents in the mantle could be moving things
Cooler
Asthenosphere
Hotter
Heat exchange gives rise to
Convection Currents
The Plate Tectonics Mechanism
The Plate Tectonics Mechanism
Rising convection currents stress the rigid outer layer
of the Earth.
Rising convection currents stress the rigid outer layer
of the Earth. This layer consists of the crust and the
outer most mantle
Geophysical
layers
Cooler
Crust
Mantle
Hotter
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The Plate Tectonics Mechanism
The Plate Tectonics Mechanism
Collectively, the rigid outer most part of the Earth
(about 100 km thick) is called the Lithosphere
It is postulated that the convection currents can
eventually break up the lithosphere into separate plates
Geophysical
layers
Tectonic
layers
Tension
Crust
Lithosphere:
Athenosphere:
Cooler
Mantle
Hotter
The Plate Tectonics Mechanism
Divergent Plate
Boundaries
Hence the term “plate tectonics”
Asthenosphere
Transform Fault
Plate Boundaries
San Andreas Fault
Convergent Plate
Boundaries
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Hot Spots
Hot Spots
Next Week’s lecture
1. New developments in plate tectonics
2. Evolution of ocean basins (Wilson cycle)
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