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Geology and Nonrenewable Minerals chapter 14 Core Case Study: Environmental Effects of Gold Mining Gold producers • • • • South Africa Australia United States Canada Cyanide heap leaching- controversial • Extremely toxic to birds and mammals • Ponds can leak or overflow • 2000: Collapse of a dam retaining a cyanide leach pond • Impact on organisms and the environment Gold Mine with Cyanide Leach Piles and Ponds in South Dakota, U.S. GOLD IN GEORGIA Has been found in 37 counties 1829-1933 The gold rush started near Dahlonega. By 1940, gold was harder to find and many miners left for California 14-1 What Are the Earth’s Major Geological Processes and Hazards? Concept 14-1A Gigantic plates in the earth’s crust move very slowly atop the planet’s mantle, and wind and water move the matter from place to place across the earth’s surface. Concept 14-1B Natural geological hazards such as earthquakes, tsunamis, volcanoes, and landslides can cause considerable damage. The Earth Is a Dynamic Planet What is geology? (dynamic processes that occur on the Earth’s surface and in its interior) http://ngm.nationalgeographic.com/video/player#/?titleID=how-big-is-7billion Three major concentric zones of the earth • Core – solid inner core and liquid outer core • Mantle • Including the asthenosphere – partly melted rock that flows • Crust • Continental crust • Oceanic crust: 71% of crust Planet Earth: Lithosphere Lithosphere - Earth’s crust and upper mantle Thickness varies from 10 to 200 km 1. Oceanic crust – floor of deep ocean basins - Composed of basalt (igneous). Also iron, magnesium and calcium. - Thin (4-5 km) and young. 2. Continental crust -- forms continents. - Composed of granite (igneous). Also silicon, aluminum, sodium and potassium. - Thickness 35 to 70 km. - Old crust. The Lithosphere The crust and the upper layer of the mantle together make up a zone of rigid, brittle rock called the Lithosphere. The Crust The crust is composed of two rocks. The continental crust is mostly granite. The oceanic crust is basalt. Basalt is much denser than the granite. Because of this, the less dense continents ride on the denser oceanic plates. The Mantle The Mantle is the largest layer of the Earth. The middle mantle is composed of very hot dense rock that flows like asphalt under a heavy weight. The movement of the middle mantle (asthenosphere) is the reason that the crustal plates of the Earth move. Convection Currents The middle mantle "flows" because of convection currents. Convection currents are caused by the very hot material at the deepest part of the mantle rising, then cooling and sinking again --repeating this cycle over and over. Convection Currents The next time you heat anything like soup or water in a pan you can watch the convection currents move in the liquid. When the convection currents flow in the asthenosphere they also move the crust. The crust gets a free ride with these currents, like the cork in this illustration. The Outer Core The core of the Earth is like a ball of very hot metals. The outer core is so hot that the metals in it are all in the liquid state. The outer core is composed of the melted metals of nickel and iron. The Inner Core The inner core of the Earth has temperatures and pressures so great that the metals are squeezed together and are not able to move about like a liquid, but are forced to vibrate in place like a solid. (Ni, Fe, Au, Pt and U) Let’s Review! • What are the 3 concentric zones of the earth? • CRUST, MANTLE AND CORE • What is the main rock that comprises the continental crust? • GRANITE • What is the main rock that comprises the oceanic crust? • BASALT • The crust and upper mantle make up the _____. • LITHOSPHERE • What makes the crustal plates move? • CONVECTION CURRENTS • The layer of the mantle that flows and is responsible for these convection currents is the _____. • ASTHENOSPHERE Volcanoes Abyssal hills Abyssal Oceanic ridge floor Abyssal floor Trench Folded mountain belt Craton Abyssal plain Oceanic crust (lithosphere) Mantle (lithosphere) Continental Continental shelf slope Continental rise Continental crust (lithosphere) Mantle (lithosphere) Mantle (asthenosphere) Fig. 14-2, p. 346 The Earth Beneath Your Feet Is Moving (2) Three types of boundaries between plates • Divergent plates • Oceanic ridge and continental rift valleys • EX: Mid-Atlantic Ridge, East Pacific Rise, East African Great Rift Valley • Convergent plates • Subduction, subduction zone • Trench • EX: Cascade Mt Range (Ca to Wa- Mt. St. Helens) • Transform faults • Sliding of plates past each other • EX: San Andreas Fault Spreading center Ocean trench Subduction Oceanic crust Oceanic crust zone Continental crust Continental crust Material cools Cold dense as it reaches material falls the outer back through mantle mantle Mantle Hot material rising convection through the cell mantle Two plates move towards each other. One is subducted back into the mantle on a falling convection current. Mantle Hot outer core Inner core Fig. 14-3, p. 346 EURASIAN PLATE JUAN DE FUCA PLATE NORTH AMERICAN PLATE CARIBBEAN PLATE ANATOLIAN PLATE CHINA SUBPLATE AFRICAN PLATE PACIFIC PLATE COCOS PLATE NAZCA PLATE Divergent plate boundaries PACIFIC PLATE SOUTH AMERICAN PLATE SOMALIAN SUBPLATE SCOTIA PLATE PHILIPPINE PLATE ARABIAN PLATE INDIA PLATE AUSTRALIAN PLATE ANTARCTIC PLATE Convergent plate boundaries Transform faults Fig. 14-4, p. 347 PLATES • Move at about the rate a fingernail grows • Mountains, earthquakes and volcanoes occur at plate boundaries • Divergent- ridges in ocean/rifts on land • Convergent- subduction/trenches in oceans and mountains (orogonic belt) on land • Transform fault- 2 plates slide past one another (San Andreas Fault) The San Andreas Fault as It Crosses Part of the Carrizo Plain in California, U.S. Mount Everest Base Camp Himalayas Khumbu Icefall Mount Everest Mt Everest- tallest mountain on land (29,029 ft = 8848 m) 1.6-3.9 (4-10 cm) inches higher every year Everest is part of the Himalaya mountain range along the border of Nepal and Tibet. At 9,800 feet, for example, there's about 2/3 of the oxygen in the air than at sea level. At 20,000 ft, there is roughly half the oxygen content in the air. At 29,035ft, the summit of Everest, there is only a third of the oxygen in the air. At the summit, the temperature can be 100°F below zero. But on a good summit day, a climber can expect around -15°F On May 29, 1953, Tenzing Norgay Sherpa of Nepal & Edmund Percival Hillary of New Zealand climbed to the summit of Everest via the Southeast Ridge Route http://www.youtube.com/watch?feature=endscre en&NR=1&v=56nWTyDTLZc Divergent boundaries Africa’s Great Rift Valley The oceanic ridge is a continuous submarine mountain chain extending approximately 80,000 km (50,000 miles) through all the world’s oceans Some Parts of the Earth’s Surface Build Up and Some Wear Down Internal geologic processes • Generally build up the earth’s surface External geologic processes (driven by the sun and influenced by gravity) • Weathering (key in soil formation) • Physical, Chemical, and Biological processes that break down rock • Erosion • • • • Wind Flowing water Human activities Glaciers- (formed the Great Lakes) Parent material (rock) Biological weathering (tree roots and lichens) Chemical weathering (water, acids, and gases) Physical weathering (wind, rain, thermal expansion and contraction, water freezing) Particles of parent material Fig. 14-6, p. 348 Volcanoes Release Molten Rock from the Earth’s Interior Volcano • Fissure- vent or crack • Magma • Lava 1980: Eruption of Mount St. Helens (Mount Pinatubo) 1991: Eruption of Mount Pinatubo- Philippines Benefits of volcanic activity- forms mountains, lakes (Crater Lake, OR), fertile soils Extinct volcanoes Eruption cloud Ash flow Ash Acid rain Lava flow Mud flow Landslide Central vent Magma conduit Magma reservoir Fig. 14-7, p. 349 Earthquakes Are Geological Rock-andRoll Events (1) Earthquake • Seismic waves- vibrations caused by earthquakes • Focus • Epicenter • Magnitude – amount of energy released • Amplitude – size of seismic waves Earthquakes Are Geological Rock-andRoll Events (2) Richter scale – a logarithmic scale recorded by a seismograph. Measures the amplitudes of the waves produced. An earthquake of magnitude 5 has 10X more ground shaking than a magnitude of 4. It is the energy though that knocks down buildings and causes damage. A magnitude of 5 releases 32X more energy than a magnitude 4 eq. • • • • • • Insignificant: <4.0 Minor: 4.0–4.9 Damaging: 5.0–5.9 Destructive: 6.0–6.9 Major: 7.0–7.9 Great: >8.0 Earthquakes Are Geological Rock-andRoll Events (3) Foreshocks and aftershocks http://earthquake.usgs.gov/learn/animations/animation.php?fla sh_title=Foreshocks%2C+Mainshocks%2C+and+Aftershocks+F lash+Animation&flash_file=aftershock&flash_width=400&flash_ height=275 Primary effects of earthquakes Due to the shaking and the resulting damage to buildings/infrastructure and due to loss of life or injury, land displacement Secondary effects Rock slides, flooding, liquefaction of sediments, fires, and tsunamis Reduce damage by mapping faults, strengthening building codes, preparing emergency teams, storing supplies and educating the public Liquefaction of recent sediments causes buildings to sink Landslides may occur on hilly ground Two adjoining plates move laterally along the fault line Earth movements cause flooding in low-lying areas Shock waves Focus Epicenter Fig. 14-8, p. 350 Areas of Greatest Earthquake Risk in the United States Areas of Greatest Earthquake Risk in the World EQ TRIVIA! There are over 1 million eq a year There are over 10,000 eq in California a year. San Andreas Fault is over 800 miles long. Earthquakes on the Ocean Floor Can Cause Huge Waves Called Tsunamis Tsunami, tidal wave Can travel as fast as a jet plane Detection of tsunamis buoys, pressure recorder December 26, 2004: Indian Ocean tsunami • Magnitude of 9.15 earthquake • Waves as high as 100 feet, 228,000 were killed • Coral reefs and mangrove forests reduce wave impact. (mangrove forests had been cleared and many reefs have been damaged in last 30 years) Shore near Gleebruk in Indonesia before and after the Tsunami on June 23, 2004 http://www.youtube.com/watch?feature=player_ embedded&v=tUN_UTY0GNo#! Earthquake in seafloor swiftly pushes water upwards, and starts a series of waves Waves move rapidly in deep ocean reaching speeds of up to 890 kilometers per hour. As the waves near land they slow to about 45 kilometers per hour but are squeezed upwards and increased in height. Waves head inland causing damage in their path. Undersea thrust fault Upward wave Bangladesh Burma India Thailand Earthquake Malaysia Indonesia Sumatra Sri Lanka December 26, 2004, tsunami Fig. 14-11, p. 352 Gravity and Earthquakes Can Cause Landslides Mass wasting • Slow movement or • Fast movement • • • • Rockslides Avalanches Mudslides 1970, earthquake in Peru caused massive landslide that killed 17,000 people Effect of human activities such as forest clearing, road building and crop growing increases the frequency of and damage caused What do you remember?? What mountains were formed at a convergent boundary? CASCADES AND HIMALAYAS How were the Hawaiian Islands formed BY A HOT SPOT Name a feature at a divergent boundary AFRICAN RIFT VALLEY, OCEANIC RIDGE Name a famous transform fault SAN ANDREAS FAULT How are earthquakes recorded? RICHTER SCALE What is the tallest mountain on land? MOUNT EVEREST Name 3 factors of erosion WIND, WATER, GLACIERS AND HUMAN ACTIVITIES Study the following website. For site #3, take the quiz, save it as a word document, and send it to me through edmodo. http://www.geo.cornell.edu/hawaii/220/PRI/conti nental_puzzle.html http://www.wwnorton.com/college/geo/egeo2/co ntent/animations/2_6.htm (hotspots) www.learner.org/interactives/dynamicearth/index.h tml 14-2 How Are the Earth’s Rocks Recycled? Concept 14-2 The three major types of rocks found in the earth’s crust—sedimentary, igneous, and metamorphic—are recycled very slowly by the process of erosion, melting, and metamorphism.