UNIVERSITY OF SOUTH ALABAMA Today’s Agenda...The Plate Tectonics Revolution Earth has a magnetic field (and it isn’t constant) The Plate Tectonics Revolution 1669 lava flow magnetic

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MAS 603: Geological OceanographyMAS 603: Geological Oceanography

Lecture 1: Introductions; Lecture 1: Introductions; Geological ThinkingGeological Thinking

UNIVERSITY OF SOUTH ALABAMA TodayToday’’s Agendas Agenda

A) Introductions• Syllabus (assessment etc.)• Additional subject material (student choice)• Introduction to geology and plate tectonics

TodayToday’’s Agendas Agenda SyllabusSyllabus

SyllabusSyllabus SyllabusSyllabus

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SyllabusSyllabus SyllabusSyllabus

SyllabusSyllabus Class WebsiteClass Website

http://http://www.southalabama.edu/geology/haywickwww.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: 1658

Archbishop James Ussher: determined the age of the Earth using biblical criteria

Clever thinkers: 1638-1687

Nicholas Steno: Principles of Superposition, Original Horizontality and Lateral Continuity


James Hutton: The Father of Geology and the originator of “Uniformitarianism”

One of Hutton’s water colour cross-sections

unconformity

William “Strata” Smith: the Father of Stratigraphy (and English Geology)


William “Strata” Smith: the Father of Stratigraphy (and English Geology)

Affectionately called “The Map”Clever thinkers: 1769-1839

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Charles Lyell: Wrote Principles of Geology.


Charles Darwin: formations of atolls and evolution


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:

Alfred Wegener: continental drift and the concept of Pangaea

The Earth

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The Earth

Even back in the 1700’s, mariners commented on the apparent jigsaw puzzle fit of South American and Africa.

Wegener’s hypothesis:

300 million years ago, the continents were all grouped together into a “supercontinent” he called Pangaea

His supporting evidence?

Matching rock types and fossils*

* types and ages

And the reaction?

And the reaction?

…Widespread Rejection

Mountain Building Before Plate Tectonics

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Mountain Building Before Plate Tectonics

1) Expanding Earth2) Contracting Earth3) Worlds in Collision (Velikovsky)

4) Lateral Accretion

Redemption would eventually occur for Wegener

Redemption would eventually occur for Wegener

…after World War II

The Plate Tectonics Revolution

Technological developments during the war increased our understanding of the world’s oceans.

Radar, sonar, and depth sounding revealed that the ocean bottoms were not flat planes


And the single most important piece of evidence for plate tectonics was also discovered around the end of WWII…


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And the single most important piece of evidence for plate tectonics was also discovered around the end of WWII…

…. Paleomagnetism


Earth has a magnetic field

(and it isn’t constant)


1669 lava flow magnetic field

(same as today +/-declination shifts)


Mt Etna eruption of 1669 Source: http://boris.vulcanoetna.com/gifs/image/Etna1669a.jpg


Mt Etna eruption of 1669 Source: http://boris.vulcanoetna.com/gifs/image/Etna1669a.jpg

Older lava flows (1 million years) magnetic field

Reversed compared to today

Paleomagnetism shows that the ocean floor youngest near the ridges and oldest near the

continents

The Plate Tectonics

Revolution

Paleomagnetism

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The outer part of the Earth is broken up into several large tectonic plates


And where they “rub” against one another, you get…Earthquakes

…Volcanoes (active, dormant and extinct)


…and mountain belts


http://shadow.eas.gatech.edu/~anewman/classes/geodynamics/misc/Worldmap.gif

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

The Plate Tectonics Revolution1963-1968 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


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So how does it all work?

The Earth

Internal “guts”of the Earth


Four Major “Geophysical” Layers


Four Major “Geophysical” Layers1) The Crust (5-35 km thick; rigid rock)


Four Major “Geophysical” Layers1) The Crust2) The Mantle (2865 km; rigid to ductile rock)

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Four Major “Geophysical” Layers1) The Crust2) The Mantle3) The Outer Core (2200 km; liquid metal)


Four Major “Geophysical” Layers1) The Crust2) The Mantle3) The Outer Core4) The Inner Core (1270 km; solid metal)

Heat exchange gives rise to Convection Currents

Asthenosphere

Cooler

Hotter

1928 - British geologist Arthur Holmes proposed that convection currents in the mantle could be moving things

More History of the Theory of Plate Tectonics

Cooler

Hotter

The Plate Tectonics Mechanism

Rising convection currents stress the rigid outer layer of the Earth.


Crust

Mantle

Geophysical layers

Rising convection currents stress the rigid outer layer of the Earth. This layer consists of the crust and the outer most mantle

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Crust

Mantle

Geophysical layers

Tectonic layers

Lithosphere:

Athenosphere:

Collectively, the rigid outer most part of the Earth (about 100 km thick) is called the Lithosphere

Cooler

Hotter


It is postulated that the convection currents can eventually break up the lithosphere into separate plates

Tension


Asthenosphere

Hence the term “plate tectonics” Divergent Plate Boundaries

Convergent Plate Boundaries

Transform Fault Plate Boundaries

San

And

reas

Fau

lt

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Hot Spots

Hot Spots

Next Week’s lecture1. New developments in plate tectonics

2. Evolution of ocean basins (Wilson cycle)

Documents

UNIVERSITY OF SOUTH ALABAMA Today’s Agenda...The Plate Tectonics Revolution Earth has a magnetic field (and it isn’t constant) The Plate Tectonics Revolution 1669 lava flow magnetic