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Lecture Outlines Physical Geology, 14/e Plummer, Carlson & Hammersley Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Introducing Geology, the Essentials of Plate Tectonics, and Other Important Concepts Physical Geology 14/e, Chapter 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Who Needs Geology? Geology—the scientific study of Earth Physical geology • the study of Earth’s materials, • changes of the surface and interior of the Earth, • and the forces that cause those changes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Supplying Things we need Resources We Use Nonmetals • ~7100 kg/person/year Metals • ~216 kg/person/year Energy • 3600 liters petroleum • 3000 kg coal • 2300 cubic meters natural gas • 0.1 kg of uranium Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Protecting the environment Understanding geology can help us lessen or prevent damage to the environment—just as it can be used to find the resources in the first place. Dwindling resources can encourage disregard for ecological damage caused by extraction activities. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Avoiding Geologic Hazards Earthquakes, volcanic eruptions, landslides, floods and tsunamis are the most dangerous geologic hazards. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Avoiding Geologic Hazards Volcanoes—ash flows and mudflows can overwhelm populated areas and disrupt air traffic Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Avoiding Geologic Hazards Landslides, floods, and wave erosion Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Earth Systems Atmosphere—the gases that envelop the Earth Hydrosphere—water on or near the Earth’s surface Biosphere—all living or once-living materials Geosphere—the solid rocky Earth Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. An overview of Physical Geology Earth’s heat engines External — energy from the Sun • primary driver of atmospheric and hydrospheric circulation • controls weathering of rocks at Earth’s surface Internal — heat moving from hot interior to cooler exterior • primary driver of most geospheric phenomena Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Earth’s Interior Compositional Layers Crust —very thin outer rocky shell Mantle—hot solid that flows slowly over time; Fe-, Mg-, Si-rich minerals Core •Outer core - metallic liquid; mostly iron •Inner core - metallic solid; mostly iron Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Earth’s Interior Mechanical Layers Lithosphere •Rigid/brittle outer shell of Earth •Composed of both crust and uppermost mantle •Makes up Earth’s tectonic plates Asthenosphere •Plastic zone on which the lithosphere floats Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Theory of Plate Tectonics Continental Drift Hypothesis • Originally proposed in early 20th century by Alfred Wegener to explain the “fit of continents”, matching rock types and fossils across ocean basins, etc. • Insufficient evidence found for driving mechanism; hypothesis initially rejected Plate Tectonics Theory • Originally proposed in the late 1960s • Included new understanding of the sea- floor and explanation of driving force • Describes lithosphere as being broken into plates that are in motion • Explains origin and distribution of volcanoes, fault zones and mountain belts Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Tectonic plate Boundaries Divergent boundaries • Plates move apart • Magma rises, cools and forms new lithosphere • Typically expressed as midoceanic ridges Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Tectonic Plate boundaries Transform boundaries • Plates slide past one another • Fault zones, earthquakes mark boundary • San Andreas fault in California Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Tectonic Plate boundaries Convergent boundaries • Plates move toward each other • Mountain belts and volcanoes common • Oceanic plates may sink into mantle along a subduction zone, typically marked by a deep ocean trench Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Surficial Processes Uplift • Volcanic and/or tectonic forces build crust up above sea level • Removal of material by erosion allows isostatic uplift of underlying rocks Weathering and Erosion • Rainfall and glaciers flow down slopes • Moving water, ice and wind loosen and erode geologic materials, creating sediment Deposition • Loose sediment is deposited when transport agent loses its carrying power • Earlier sediments get buried and harden into sedimentary rock Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Geologic time Deep Time • Most geologic processes occur gradually over millions of years • Changes typically imperceptible over the span of a human lifetime • Current best estimate for age of Earth is ~4.55 billion years Geologic Time and the History of Life • • • • 544 million years: complex life forms first became abundant 230 million years: reptiles became abundant 65 million years: dinosaurs became extinct 3 million year: humans Nothing hurries geology — Mark Twain Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. End of Chapter 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.