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Geology and Nonrenewable Resources Chapters 14 Living in the Environment, 16th Edition, Miller Advanced Placement Environmental Science Edited by Ms. Wilkins, Original slide show from La Canada High School Dr. E A View of Earth Earth’s four spheres » Solid Earth » Hydrosphere » Atmosphere » Biosphere Distribution of Elements More than 100 elements in entire Earth, but 99% of Earth's mass is made up of only 8 elements Whole Earth: Fe>O>Si>Mg>Ni>S>Ca>Al (others constitute < 1%) Earth's crust O>Si>Al>Fe>Mg>Ca>K>Na (other constitute <1%) Composition of Earth’s Crust Earth’s Crust Oxygen 46.6% All others 1.5% Magnesium 2.1% Silicon 27.7% Potassium 2.6% Sodium 2.8% Calcium 3.6% Iron 5.0% Fig. 10.4, p. 213 Aluminum 8.1% Earth Structure Has huge economic and Political consequences Important to understand the distribution of elements and minerals determined during earths formation. Compositional layers Core Minerals unevenly distributed because of density Also, isolated sites- ex diamonds must be exposed to extreme heat and pressure. - Fe,Ni. Mantle - compositionally homogenous, made up of peridotite rock Crust - compositionally heterogeneous, lots of rock types Rock Cycle Recycles scarce minerals and elements http://www.cotf.edu/ete/modules/msese/earthsysflr/rock.html Igneous Rock formed by cooling and crystallization of magma If the cooling occurs at the surface, it is called extrusive igneous If the cooling occurs in the Earth, it is called intrusive igneous Extrusive igneous usually cools fairly rapidly and therefore has smaller crystals than intrusive Examples: Granite, Basalt, Quartz, Mica, Feldspar, Obsidian http://hvo.wr.usgs.gov/hazards/dds24167_L.jpg Sedimentary Rock Rock formed by the piling of material over time Sediment is compressed, heated and chemically changed over long period of time Examples: Sandstone, Shale, Gypsum, Limestone, Chalk http://realgar.mcli.dist.maricopa.edu/alan/pix/grand-canyon.jpg Metamorphic Rock Igneous or sedimentary rock subjected to tremendous pressure and heat Examples: Slate, Marble, Quartzite Lithosphere Lithosphere is divided into plates (about 13 major plates and several smaller ones). Consists of rigid, brittle crust and uppermost mantle. Plate tectonics explains wide range of geological phenomenon (volcanism, earthquakes, orogenesis, fossil distributions, etc.) Evidence for Continental Drift Coastline fit Alignment of mountain ranges Similar Rock Sequences Fossils Modern Fauna Ancient climates Evidence for Continental Drift Idea was revived in 1950’s and developed into Plate Tectonics Theory of plate tectonics accepted by nearly all geologists. Plate tectonics explains wide range of geological phenomenon (volcanism, earthquakes, orogenesis, fossil distributions, etc.) Plate Tectonics Bathymetric observations during WWII and earthquake data set stage for Plate Tectonics. These observations are now combined to form the theory of plate tectonics. Plate Boundaries Defined Depths by earthquake data. of earthquakes indicate types of boundaries. Plate Boundaries Plate Boundaries Divergent Boundaries – Places where plates are coming apart Convergent Boundaries – Places where plates crash or crunch together Transform Boundaries – Places where plates slide past each other Convergent Boundaries Crust destroyed at convergent margins, mountain building Three types: – Ocean-Ocean – Ocean-Continent – Continent-Continent Ocean-Ocean Convergent Boundaries Deep oceanic trenches Ocean-Ocean Convergent Boundaries Earthquakes define zone dipping into mantle (Benioff zone) Zones around Pacific dipped about 45o toward the continents Ocean-Continent Boundaries Heat added to crust by magmas causes regional and contact metamorphism Heat added also produced more felsic magma types by crustal assimilation/fractional crystallization Stratovolcanoes built on continental crust => continental volcanic arc Deep-sea trench and accretionary wedge (melange) along coast of continent Examples: Andes, Cascades, Central America Ocean-Continent Boundaries Magmas produced in mantle wedge above subducting slab Much ascending magma stalls in continental crust > batholith (roots of volcanic arc) Transform Boundaries Most fracture zones connect segments of mid-ocean ridges Areas of different water depth on each side of fracture zone Shallow earthquakes occur on transforms between sections of mid-ocean ridge Transform Boundaries Connect other plate margins (convergent and divergent) San Andreas Fault - on land transform (Pacific plate sliding north relative to North America) Hot Spots Columns of hot material rising through mantle (plumes). Hot spot fixed in position underneath moving lithospheric plates Driving Forces of Plate Tectonics Plate movement due to Earth's attempt to lose internal heat Conduction *Convection Driving Forces of Plate Tectonics Plate movement due to Earth's attempt to lose internal heat Conduction & Convection Gravity-driven sliding Plate slide down sides of mid-ocean ridge Gravity gives the push, not magmas at ridge Ridge push is probably the main force on plates Flow of material associated with hot spot plumes drives plates Columns of rising material vs. convection cells Chaotic convection in mantle (plumes of rising material) EARTHQUAKES http://www.howstuffworks.com/earthquake6.htm Earthquakes Most destructive forces on Earth. But it is buildings and other human structures that cause injury and death, not the earthquake itself 1988 - Soviet Armenia: magnitude 6.9, 25,000 people died 1985 - Mexico City: magnitude 8.1, 9500 people 1989 - Loma Prieta, CA: magnitude 7.1, 40 people died 1995 - Kobe, Japan: magnitude 7, ~6000 people died 30,000 earthquakes occur worldwide annually that are strong enough to be felt Typically only 75 of them are considered to be significant Vibration of earth produced by rapid release of energy (seismic waves) with radiate in all directions from the source (focus) Like ripples from dropping a stone in a pond, energy dissipates with distance Earthquakes don't occur randomly. Occur on faults or fractures within the earth Explained by plate tectonics. Most occur on plate boundaries Sometimes in plate interiors if enough stress is built up Types of Waves Earthquake waves = seismic waves. Recorded on seismometers on seismographs. Types of Waves Surface waves - travel on Earth's surface, away from epicenter. – Very slow waves. Cause a lot of damage, rolling feeling at end of earthquake Body Waves - travel through Earth's interior, spread outward from focus Body Waves P waves: Pressure or compressional waves. Vibrate parallel to direction of wave travel like a slinky. Fast travel: 4-7 km/sec (15,000 mph) P is primary, or first wave to arrive at recording station S waves: Shear waves. Vibrates perpendicular to direction of wave travel. Like snapping a rope Slower than P wave: 2-5 km/sec (11,000 mph) So S is secondary, or second wave to arrive at recording station VOLCANOES http://georoc.mpch-mainz.gwdg.de/volcano.gif Volcanoes • Located at plate boundaries & EQ zones (why ?) • Result in surface pyroclastic and extrusive rocks • Pyroclastic : particles thrown into air during eruption - settle to form ash, tuff & agglomerate • Magma extruded to surface to form extrusive igneous rocks (lava), e.g rhyolite, andesite & basalt (type depends on acidity) – Acidic : viscous, flows poorly – Basic : more fluid - flows on very gentle slopes over vast areas, e.g basalt plains of Victoria Volcanoes Basic parts of a volcano Crater (depression at the summit of a volcano, connected by a vent or pipe to the magma chamber below) Caldera (crater more than 1 km in diameter, formed at the summit of a volcano when lava is drained from an underground magma chamber, causing the summit of the volcano to be unsupported, and to collapse) Sedimentary rock Sediments glued together Igneous rock Heat Metamorphic rock Heat and pressure http://volcano.und.nodak.edu/vwdocs/vw_hyperexchange/parts.html Shield Volcano Mauna Loa, on the Big Island of Hawaii, is the largest active volcano in the world. It last erupted in 1984. Mauna Loa erupted 14 times in the 20th Century, and 37 times since 1832. Mauna Loa is the most massive mountain on Earth, rising to an elevation of 13,677 feet above sea level, or 31,677 feet above the sea floor. Its volume is 10,000 miles3. 2. Cinder cones Erupt pyroclastic material Steep slopes (30 to 40 degrees) Not very long lived. Typically small, less than 1000 feet tall Often parasitic on larger volcanoes Examples: Paricutin in Mexico, Sunset crater in Arizona Cinder cones Composite Volcano Sedimentary rock Chemical and physical weathering Igneous rock Heat –magma (lava) Metamorphic rock Heat and pressure Yellowstone Caldera Eruptions from Volcanoes May produce ejecta, (lava rock or ash), molten lava, and/or toxic gases. Gases: H2O, CO2, SO2, HCl Occur when pressure within magma chamber forces molten magma up through a conduit and out a vent. Benefits: new landforms, minerals, and nutrients from broken down lava Eruption of Mount Saint Helens, May 18, 1980 The eruption of Mount Saint Helens was the most destructive in the history of the United States Mount Saint Helens is located in southwest Washington in the Cascade Range, a mountain range dominated by periodically active volcanic peaksIn Images include pre-eruption activity and posteruption effects such as the blast area, mud flows, ash fall, and altered terrain http://www.ngdc.noaa.gov/seg/hazard/slideset/31/31_thumbs.html Minerals and Rocks What is a mineral? – naturally occurring, inorganic, solid element or compound with a definite chemical composition and a regular internal crystal structure What is rock? – solid, cohesive, aggregate of one or more minerals – Each rock type has a characteristic mixture of minerals What is an Ore? – Rock with large concentration of a particular maineral to make it profitable – High and low grade ores » NON- Metalic Mineral Sand, gravel, limestone » Metalic Aluminum, Steel, manganese, cobalt, chromium, Copper, Gold Mining: Extract Ore from Ground Types of Mining: • Surface Mining: Scoop ore off surface or earth. • cheap. • safe for miners. • large environmental destruction. • Underground Mining: Use of shafts to reach deeply buried ores. • expensive. • hazardous for miners. • less environmental damage. Average Concentration of Valuable Metals in the Crust Aluminum ~8% Iron ~5% most Fe and Al is in silicate minerals and is not used as an ore Titanium 0.44% Nickel 75 ppm or 0.0075% Zinc 70 ppm or 0.0070% ppm = Copper 55 ppm 0.0055% parts per million Lead 13 ppm or 0.0013% Silver 0.07 ppm Gold 0.004 ppm Strip Mining strip-mining: scoop off rock overburden, and then scoop off ore material. • Economics of strip mining depend on stripping ratio • Large land area can be involved, especially for coal and bauxite. Surface Mining open pit mining: • circular hole in ground, with ramp circling down along sides, allows deeper ore to be reached. Gold in Quartz A large quartz boulder with a lot of visible gold. Usually, the gold is much finer and hard to see. Placer Deposition Panning for gold in a placer deposit Aeolian Placers The "diamond crawl" in a deflation basin, Diamond Area No 1, Namibia Diamond concentrations were increased by wind erosion Cassiterite tin oxide ore mineral, SnO2. It is generally opaque but is translucent in thin crystals. Its luster and multiple crystal faces produce a desirable gem. Cassiterite has been the chief tin ore throughout ancient history and remains the most important source of tin today US General Mining Law of 1872 Acid Mine Drainage Nonrenewable Mineral Resource Depletion Curves Source: Miller, G. Tyler, Living In The Environment. (2000) Wadsworth Publishing. New York.