Presentation on theme: "Geology and Nonrenewable Minerals Chapter 14. Core Case Study: Environmental Effects of Gold Mining Gold producers South Africa Australia United States."— Presentation transcript:
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 “there’s gold in them thar hills”
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) 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 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.
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
The Earth Beneath Your Feet Is Moving (2) Three types of boundaries between plates Divergent plates Magma Oceanic ridge and continental rift valleys Convergent plates Subduction Subduction zone Trench Transform fault; e.g., San Andreas fault
Fig. 14-3, p. 346 Spreading center Ocean trench Plate movement Subduction zone Oceanic crust Continental crust Material cools as it reaches the outer mantle Cold dense material falls back through mantle Hot material rising through the mantle Mantle convection cell Two plates move towards each other. One is subducted back into the mantle on a falling convection current. Mantle Hot outer core Inner core Plate movement
Fig. 14-4, p. 347 EURASIAN PLATE NORTH AMERICAN PLATE ANATOLIAN PLATE JUAN DE FUCA PLATE CARIBBEAN PLATE PHILIPPINE PLATE CHINA SUBPLATE AFRICAN PLATE ARABIAN PLATE INDIA PLATE PACIFIC PLATE COCOS PLATE SOUTH AMERICAN PLATE NAZCA PLATE AUSTRALIAN PLATE SOMALIAN SUBPLATE SCOTIA PLATE ANTARCTIC PLATE Transform faults Divergent plate boundaries Convergent plate boundaries
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 on land Transform fault- 2 plates slide past one another
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) (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 en&NR=1&v=56nWTyDTLZc en&NR=1&v=56nWTyDTLZc
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)
Fig. 14-6, p. 348 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
Volcanoes Release Molten Rock from the Earth’s Interior Volcano Fissure- vent or crack Magma Lava 1980: Eruption of Mount St. Helens ( Mountt Pinatubo) 1991: Eruption of Mount Pinatubo- Philipines Benefits of volcanic activity- forms mountains, lakes (Crater Lake, OR), fertile soils
Fig. 14-7, p. 349 Extinct volcanoes Eruption cloud Ash Ash flow Lava flow Mud flow Landslide Central vent Magma conduit Magma reservoir Solid lithosphere Upwelling magma Partially molten asthenosphere Acid rain
Earthquakes Are Geological Rock-and- Roll Events (1) Earthquake Seismic waves Focus Epicenter Magnitude Amplitude
Earthquakes Are Geological Rock-and- Roll Events (3) Foreshocks and aftershocks Primary effects of earthquakes
Major Features and Effects of an Earthquake
Fig. 14-8, p. 350 Liquefaction of recent sediments causes buildings to sink Two adjoining plates move laterally along the fault line Earth movements cause flooding in low-lying areas Landslides may occur on hilly ground Shock waves Epicenter Focus
Areas of Greatest Earthquake Risk in the United States
Fig. 14-9, p. 350 Highest risk Lowest risk
Areas of Greatest Earthquake Risk in the World
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 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)
Formation of a Tsunami and Map of Affected Area of Dec 2004 Tsunami
Fig , p. 352 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 India Thailand Sri Lanka Malaysia Earthquake Sumatra Indonesia December 26, 2004, tsunami Burma
Shore near Gleebruk in Indonesia before and after the Tsunami on June 23, 2004
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
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.
There Are Three Major Types of Rocks (1) Earth’s crust Composed of minerals and rocks Three broad classes of rocks, based on formation 1.Sedimentary (made of sediments) Sandstone and shale (compacted sediments) Dolomite and limestone (compacted shells and skeletons) Lignite and bituminous coal (compacted plant remains)