Today s s Agenda. Syllabus. Syllabus. Syllabus. MAS 603: Geological Oceanography. Lecture 1: Introductions; Geological Thinking

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1 UNIVERSITY OF SOUTH ALABAMA Today s s Agenda MAS 603: Geological Oceanography Lecture 1: Introductions; Geological Thinking Today s s Agenda Syllabus A) Introductions Syllabus (assessment etc.) Additional subject material (student choice) Introduction to geology and plate tectonics Syllabus Syllabus 1

2 Syllabus Syllabus Syllabus Class Website Lecture 1: Geological Thinking Geological Thinking First geologists date back to the days of early hominids 2

3 Clever thinkers: AD 79 Clever thinkers: 1658 Pliny the Younger: first documented Geological report (eruption of Mt. Vesuvius in AD 79 Archbishop James Ussher: determined the age of the Earth using biblical criteria Clever thinkers: Clever thinkers: 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: Clever thinkers: Affectionately called The Map William Strata Smith: the Father of Stratigraphy (and English Geology) William Strata Smith: the Father of Stratigraphy (and English Geology) 3

4 Clever thinkers: Clever thinkers: Charles Lyell: Wrote Principles of Geology. Charles Darwin: formations of atolls and evolution Clever thinkers: Clever thinkers: 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 4

5 The Earth Wegener s hypothesis: Even back in the 1700 s, mariners commented on the apparent jigsaw puzzle fit of South American and Africa. 300 million years ago, the continents were all grouped together into a supercontinent he called Pangaea His supporting evidence? And the reaction? Matching rock types and fossils* * types and ages And the reaction? Mountain Building Before Plate Tectonics Widespread Rejection 5

6 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 Technological developments during the war increased our understanding of the world s oceans. 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 6

7 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 Older lava flows (1 million years) magnetic field Mt Etna eruption of 1669 Source: (same as today +/- declination shifts) Mt Etna eruption of 1669 Source: Reversed compared to today The Plate Tectonics Revolution Paleomagnetism shows that the ocean floor youngest near the ridges and oldest near the continents Paleomagnetism 7

8 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 J. Tuzo Wilson was the first to describe global tectonics in terms of rigid surface "plates, and recognized ocean evolution ( Wilson Cycle ) 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 8

9 So how does it all work? The Earth Internal guts of the Earth Internal guts of the Earth Four Major Geophysical Layers Internal guts of the Earth Internal guts of the Earth Four Major Geophysical Layers 1) The Crust (5-35 km thick; rigid rock) Four Major Geophysical Layers 1) The Crust 2) The Mantle (2865 km; rigid to ductile rock) 9

10 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 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. Cooler Rising convection currents stress the rigid outer layer of the Earth. This layer consists of the crust and the outer most mantle Geophysical layers Crust Mantle Hotter 10

11 The Plate Tectonics Mechanism Collectively, the rigid outer most part of the Earth (about 100 km thick) is called the Lithosphere The Plate Tectonics Mechanism It is postulated that the convection currents can eventually break up the lithosphere into separate plates Tectonic layers Lithosphere: Geophysical layers Crust Tension Cooler Athenosphere: Mantle Hotter The Plate Tectonics Mechanism Hence the term plate tectonics Divergent Plate Boundaries Asthenosphere Convergent Plate Boundaries Transform Fault Plate Boundaries San Andreas Fault 11

12 Hot Spots Hot Spots Next Week s lecture 1. New developments in plate tectonics 2. Evolution of ocean basins (Wilson cycle) 12