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Introduction to Geology 1 Geology ”Knowlege or study of the Earth." Physical geology examines the materials and processes of the Earth. Historical geology examines the origin and evolution of our planet through time. USES OF ROCK Source of power Source of minerals Source of soil Source of building and road making materials Source of industrial raw materials Source of gems and precious metals Geology in the News Geologic Hazards • Two die in 6.5 magnitude Earthquake near San Lois Obispo California • Earthquake triggers mudslides http://news.nationalgeographic.com/news/2003 San Andreas Fault Geology in the News 2 “Major Quake Likely to Strike San Francisco Bay Region Between 2003 and 2032” Dealing with Geologic Hazards: • Assessing Risks • Avoiding Risks • Preventing Damage • Predicting Impact http://quake.wr.usgs.gov/research/seismology/wg02/ Earthquake Bam, Iran • A Magnitude 6.5 Earthquake hits a stone- and mud-house city of 100,000 in Iran 12-26-03 – 30,000 Dead – 30,000 Refugees • US sends aid and releases sanctions • Relations improved Photos from AP Geological Hazards Volcanoes Landslides Earthquakes Geology in Engineering Slope Failure Risk Assessment and Control To prevent slope failure engineers must understand the geology that forms and controls the slope Geology in Engineering The Leaning Tower Straightens Up In Pisa the tilted one is back in business after an 11-year effort to keep it from collapsing Committee member John Burland, an engineer, promoted soil extraction as the best way to save the tower. Engineers use knowledge of geology to design, protect and correct structures www.smithsonianmag.si.edu What's the first thing that you notice about our planet when you see this image? ESS The Earth System What are some of the interactions between these spheres? The Earth System Hydrosphere: The oceans cover ~71% of our planet and represent 97% of all the water on our planet. Atmosphere: The thin blanket of air that covers our planet. It is not only the air we breathe, but protects us from harmful radiation from the sun. ESS The Earth System Biosphere: includes all life on Earth - concentrated at the surface. Plants and animals don't only respond the their environment but also influence it. Solid Earth (Lithosphere): The majority of the Earth system. ESS The Origin of the Earth Nebular Hypothesis: The Earth, the other 8 planets and the Sun accreted from a vast cloud of dust and gas (nebula). 1. Gravitational contraction (5 BYA) Rotates and flattens. 1. Solar fusion (4BYA) 2. Newly formed planets begin to differentiate a) heavier elements and chemical components sink to the center and rocky material formed the crust. Earth's Internal Structure The Earth's interior is characterized by a gradual increase in temperature, pressure and density with depth. At only 100 km depth, the temp is ~1300°C. At the Earth's center, the temperature is >6700°C. The pressure in the crust increases ~280 bars for every kilometer depth. Earth's Internal Structure The Earth consists of 3 major regions marked by differences in chemical composition. Crust (Lithosphere): rigid outermost layer of the Earth. Consists of two types: 1. oceanic - 3-15 km thick and is composed of basalt (igneous). Young (<180 million years old). 2. continental - up to 70 km thick and composed of a wide variety of rock types (ave. granodiorite). Ranges from young to old (>3.8 billion years old). Earth's Internal Structure Mohorovicic Discontinuity The “slip surface” boundary between the crust and the mantle. Mantle: comprises ~82% of the Earth by volume and is ~2900 km thick. • Change in composition occurs. • Asthenosphere is the soft, solid but “ductile” region just below the lithosphere. • The mantle is able to flow (plasticity) at very slow rates. Earth's Internal Structure Core: composed of iron, nickel and other minor elements. • Outer core is liquid, capable of flow and source of the Earth's magnetic field. • Inner core is solid FeNi. There is no major chemical difference between the outer and inner core.