Complete Geography Discusson Post Lesson 11

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Arbogast, Discovering Physical Geography, Chapter 12, Earth's Internal Structure, Rock Cycle, and Geologic Time, pages 304-331.

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Earth’s Rocks and Minerals Global Physical Environment GEOG 121 Dr. Christopher Atkinson Interior Earth Layers • Surface to 6370 km: 3 Earth Layers that Comprise the Interior – Composition – Thickness Composition of the Earth’s Crust • Oxygen – 47% • Silicon – 28% • Aluminum – 8.1% • Iron – 5% Mineral vs. Rock • Mineral (Quartz) – Natural substance – Chemical configuration – Crystalline • Rock (Granite) – Mass of consolidated mineral matter Source: statesymbolsusa.org; University of Texas Rock Outcrop • Defined: Rocks exposed at the Earth’s surface Source: Big Stone National Wildlife Refuge 3 Types of Rocks • Igneous – Fire • Sedimentary – Water • Metamorphic – Heat and Pressure Rock Type #1 • Igneous: “Fire rock” Igneous Rocks: 2 Types • Intrusive – Molten Material: Magma • Inside the Earth • Extrusive – Molten Material: Lava • At the surface Source: Wikipedia Images Plutons: Intrusive Igneous Rock • 4 Different Types of Plutons – Batholiths – Dike – Sill – Laccolith – Other igneous rock classifications: 1) cooling rates; and, 2) mineral composition • Shiprock in New Mexico Sources: University of Wisconsin; Explore Volcanoes Cooling Rates: Intrusive and Extrusive Rocks • Slow Cooling – Large rock crystals – Example: granite • Fast Cooling – Small rock crystals – Example: volcanic glass (obsidian) Source: Wikipedia Images Mineral Composition • Felsic Rocks (Granite) – High silica content – Low melting temperatures – Lighter colors • Mafic Rocks (Basalt) – Low silica content – High melting temperatures – Darker colors Source: Wikipedia Images Rock Type #2 • Sedimentary: “Layered rock” Sedimentary Rocks • Characteristics – Material: rock fragments – Transport: wind or water – Becoming Solid: lithification – Lithification: • Compaction • “Cemented” 3 Types of Sedimentary Rocks • Clastic • Chemically Precipitated • Organic Clastic Sedimentary Rocks • Characteristics – Fragments from other rocks – Accumulate and lithify • Examples – Sandstone → – Siltstone – Claystone Source: statesymbolsusa.org Chemically Precipitated Sedimentary Rocks • Formation – Carbonate precipitation – Accumulation of marine organisms • Examples – Limestone (caves) – Evaporites (salt flats) Bonneville Salt Flats Source: Wikipedia Images Mystery Cave: Southeastern Minnesota Chemically Precipitated Rocks Source: Minnesota Department of Natural Resources: Mystery Cave Organic Sedimentary Rocks • Formation – Carboniferous Period – Coal: water and oxygen decrease; material solidifies • Examples – Coal – Petroleum – Natural gas Metamorphic Rocks • Altered Rocks – Heat – Pressure • Examples – Marble – Quartzite – Gneiss Blue Mounds State Park 90-foot Sheer Cliff Quartzite Northeast of Luverne, Minnesota Source: Blue Mounds State Park, MN DNR How Do Rocks Change? • Rock Cycle – Weathering • Example – Heat and Pressure • Example – Crystallization • Example Earth’s Inner Structure and Geologic Time Global Physical Environment GEOG 121 Dr. Christopher Atkinson Lithosphere • Solid Earth • Defined: “The outer solid portion of the Earth that is 44 miles (71 km) thick and comprises the uppermost portion of the asthenosphere and crust. What is Inside Earth? • Earthquakes tell us. – Seismic waves • Cooler rocks: waves travel faster • Stories tell us. – Fictional accounts from the 19th Century Jules Verne, 1864 Sources: Wikipedia, Audio Books Online, Nostalgic Radio 3 Layers of the Earth • Crust • Mantle • Core Source: physics.org Crust • 2 Types – Continental • Thickness: ≤ 37 miles (60 km) • Composition: Sial – Silicon and Aluminum (crust is lighter) – Granite – Oceanic • Thickness: ≤ 5 miles (8 km) • Composition: Sima – Silicon and Magnesium – Basalt Thick Continental Crust Mount Everest: 29,029 ft (8850 m) Sir Edmund Hillary Sources: Wikipedia Images; Amazon Source: NOAA Marianas Trench: 36,000 ft (10,976 m); 6.8 mi (11.0 km) Mantle • 2 Regions – Upper • Thickness: 260 miles (419 km) • Composition: Molten Rock – Highly viscous – Lower • Thickness: 1385 miles (2234 km) • Composition: Iron, magnesium, and silicon oxides Asthenosphere • Top Portion of Upper Mantle – Thickness: 25 to 105 miles (40-170 km) below surface – Composition: Molten rock – Importance: Magma for Volcanoes • Convection Currents Core • 2 Regions – Outer • Thickness: 1398 miles (2255 km) • Composition: Molten iron • Importance: Produces Earth’s magnetic field – Protects from solar wind – Inner • Thickness: 760 miles (1226 km) • Composition: Solid iron, some nickel • Notable: Extreme pressure (3 million atmospheres) – 44,100,000 pounds per square inch Mechanism of Solar Wind Protection Breaks Down Hilary Swank Aaron Eckhart Must travel to the Earth’s core to “jump start” the core and save Earth. 2003 Aurora Borealis (Northern Lights) Source: imdb.com Geologic Time • 3 Time Sequences in Geology – Era: longest – Period: second longest – Epoch: shortest Important • Page 339 (#1-13) • For example: Carboniferous – Coal forms from plants How to Tell Geologic Time? • Radioactive Isotopes – Half life of elements • Carbon 14: 5730 years – 50% left: 5730 years have passed Source: University of Pennsylvania Relative Geologic Time: Sequence in Perspective • Page 341 (Relate to my family) – Compared to 1 year of time (Earth Formation: Jan. 1) – December 31 • • • • • • 1 was born 0.12 seconds before midnight My sister was born 0.11 seconds before midnight My Dad was born 0.19 seconds before midnight My Mom was born 0.19 seconds before midnight My Grandpa (Mom) was born 0.29 seconds before midnight My Grandma (Mom) was born 0.29 seconds before midnight Relative Geologic Time: Sequence in Perspective • Page 341 (Earth Events) – Compared to 1 year of time (Earth Formation: Jan. 1) – December 31 • Melting of continental glaciers: 27.8 minutes before midnight • Formation of Grand Canyon: 5 am • First ancestral humans: 6 pm Thinking About the Landscape via Geology • Grand Canyon – Slow downcutting with a rising Colorado Plateau? • Uniformitarianism – Flash flood of epic magnitude? • Creationism • Shiprock • Devils Tower Sources: Grand Canyon National Park; Devils Tower National Monument; Wikipedia Images Why Care About the Geologic Timeline? • Study At Past Gives Hits to the Future – PETM: Paleocene-Eocene Thermal Maximum • • • • 56 million years ago Summer Water Temperature at North Pole: 74 F Animals became smaller Massive carbon release (> 1500 ppm) – Earth warmed 9 F° (5 C°) – Equivalent of burning all Earth reserves of coal, oil, and natural gas – National Geographic, October 2011 (Matt Huber, page 108109)
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The Geological Timeline
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