Plate Tectonics. Rearranging Earth’s Surface. Tectonic Processes. GOAL: To understand the processes behind the distribution of Earth’s continents and oceans. Tectonic Processes. Alfred Wegener and how a scientific paradigm operates Structure of Earth allows continents to move
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Tectonic Processes GOAL: To understand the processes behind the distribution of Earth’s continents and oceans
Tectonic Processes • Alfred Wegener and how a scientific paradigm operates • Structure of Earth allows continents to move • Types of Plate Interactions • Divergence • Convergence • Transform 4. Hot Spots
1. Alfred Wegener and how a scientific paradigm operates "Scientists still do not appear to understand sufficiently that all earth sciences must contribute evidence toward unveiling the state of our planet in earlier times, and that the truth of the matter can only be reached by combing all this evidence. . . It is only by combing the information furnished by all the earth sciences that we can hope to determine 'truth' here, that is to say, to find the picture that sets out all the known facts in the best arrangement and that therefore has the highest degree of probability. Further, we have to be prepared always for the possibility that each new discovery, no matter what science furnishes it, may modify the conclusions we draw." Alfred Wegener. The Origins of Continents and Oceans (4th edition)
Until 1960s – Utter Rejection by Geologists Dr. Rollin T. Chamberlin of the University of Chicago said, "Wegener's hypothesis in general is of the footloose type, in that it takes considerable liberty with our globe, and is less bound by restrictions or tied down by awkward, ugly facts than most of its rival theories." American Association of Petroleum Geologists organized a symposium specifically in opposition to the continental drift hypothesis. "Utter, damned rot!" W.B. Scott, President of the American Philosophical Society
Why the opposition & shift? • An example of how a discipline can get “locked into” a pathway of mental thinking for decades (paradigm), rejecting the idea of moving continents. • An example of how a discipline protects its “turf” – rejecting the thoughts of a meteorologist. • Enough time for the opponents to die, and a bunch of new geologists in the 1960s to challenge “the establishment”. • Reminder throughout this class that ideas shift and much depends on the mental framework of the scientist
2. Structure of Earth allows continents to move Wegener could not answer a fundamental question of HOW continents could move. But geology advanced to the point to begin to understand Earth’s internal structure & how it allows continental drift
Structure and Internal Energy • Knowledge of Earth’s Interior is incomplete – we’ve only explored about 1/1000 of Earth’s radius • Inferential knowledge through monitoring of shockwaves transmitted through Earth from earthquakes or human-made explosions • Four main zones of the Earth’s Interior • Earth’s Core: Deepest part of the Earth • Inner Core: supposedly solid, dense (iron/nickel or iron/silicate • Outer Core: (molten) liquid shell beneath the mantle that encloses the inner core
Structure and Internal Energy (cont.) • Earth in Cross Section 3. Earth’s Mantle: Surrounds the outer core, largest of all four shells; believe 3 zones within mantle • Lithosphere: uppermost zone of mantle & crust together • Asthenosphere: “plastic” layer; below lithosphere • Mesosphere: rigid part of mantle; below asthenosphere 4. Earth’s Crust: outermost layer; mixed rock types • Mohorovičić discontinuity (Moho): boundary between earth’s crust & mantle
