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Philosophy and Fundamental Concepts (unfinished from last lecture) •Concept 5: Uniformitarianism (James Hutton) •The present is the key to the past •Uniformity of Process, not magnitude and frequency •EG-The present is the key to the future GLY 2030Cat Siccar Point, Scottish coast Unconformity 1 Tectonics and Geologic Cycles – Tectonic, Rock, Hydrologic, Biogeochemical Part 1: The Tectonic Cycle Alfred Wegener German Meteorologist Gathered Evidence from Geologic Literature dared to challenge current geologic assumptions that continents were fixed in place Fit of Continents / Matching Geologic Units Locations of Past Glaciations Locations of Past Equatorial Regions Distribution of Fossils Continental Drift Hypothesis Pangaea = “all land” “pan-gee-ah” Alfred Wegener (1880-1930) Pacific Northwest Tibet South America South Atlantic Japan Arabian Peninsula Oceanic trench Andes Interior Continental shelf Conventions in Geology - Shape Referring to Differences in Topography Elevation: height above sea level Relief: elevation difference Slope: steepness 1st piece of Evidence: Earth Shape revealed by sea floor mapping Oceanic fracture zones Continental shelves Submerged ridges and island arcs Plateaus Linear island chains Continents Deep ocean trenches Mid-ocean ridges Oceanic plateaus 2nd piece of Evidence: Locations of Moderate to Strong earthquake locations (1973-2000) EQ in belts Mid-ocean ridges Southern Eurasia Trenches Mountain belts Sparse in some regions 3rd Piece of Evidence: Volcanic Activity around the Pacific Ocean 3rd Piece of Evidence: Global Distribution of Volcanic Activity Belts Mid-ocean ridges (not all shown) Island arcs next to trenches Oceanic islands Red Sea and East Africa Mountain belts next to trenches Sparse in some regions Compare the distribution of earthquakes (yellow), volcanoes (orange), and high elevations (brown) EQ, volcanism, or mtn. building = tectonic activity Belts of tectonic activity divide lithosphere into tectonic plates Earth’s Magnetic Field Normal magnetic field Liquid outer core contains convection currents Reversed magnetic field Magnetometer Data Collection Magnetometer Data Analysis Magnetic Data Analysis Paleomagnetic Record Magnetic Data Analysis and Comparison with Rock Record 4th Piece of Evidence: Magnetic Striping of Sea Floor Time 1: normal polarity Observe how magnetic reversals are recorded by a mid-ocean ridge Show movie of seafloor striping Time 2: reversed polarity Build series of magnetic stripes over time 4th Piece of Evidence: Magnetic Striping of Sea Floor 10.02.d Blackboard Exercise: Calculate Sea floor spreading rate… 5th Piece of Evidence: Sediment Thickness Pattern Thickest along passive continental margins Thinnest near mid-ocean ridges Thick offshore of large rivers