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UM GEO 101N - Plate Tectonics continued
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Geo 101N 1st Edition Lecture 6Outline of Last Lecture I. New Observational Dataa. Harry Hessb. SonarII. Discovery of Sea Floor SpreadingIII. Magnetic FieldOutline of Current Lecture IV. Magnetic AnomaliesV.Plate Tectonics continueda. Acceptanceb. Plate Layersc. MarginsCurrent LectureI. Marine Magnetic Anomaliesa. Differences between the actual strength @ any given point and the actual strength; recorded in sea floor basaltsb. Stronger = positive anomalies; “normal” polarity (current)c. Weaker = negative anomalies; reversed d. Chron: the time interval between successive reversals; reversals do not occur regularlye. Stripes are cause by the cooling of basalts & placement of the magnetic poles at the timef. Width of the stripes is relative to the duration of each chron; indicates that the rate of seafloor spreading has been semi-constant for @ least 4.5 billion yearsII. Acceptancea. The modern plate tectonic theory evolved in the 1960’sb. Previous research provided the foundations; Wegner, Hess/Dietz, Vine & Matthewsc. By 1968 evidence for tectonics was overwhelmingd. Changed the views of most geologistsIII. Layersa. Lithosphere Plate: crust & top (cooler) part of the upper mantlei. Rigid; when forced it bends or breaksb. Asthenosphere: soft “plastic” layer the lithosphere floats onThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.i. Warmer mantle (>1280ᵒC)c. Active margin = plate boundary; earthquakes are commond. Passive margin = just the boundary between continental crust and oceanic, no plate boundaryi. Continental crust is thinner than its continental


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UM GEO 101N - Plate Tectonics continued

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