Chapter 11 Geology, Minerals, and Mining

1. Chapter 11 Geology, Minerals, and Mining

2. This lecture will help you understand: Earth’s internal structure and plate tectonics Rocks and the rock cycle Geologic hazards Mineral resources Mining methods Impacts of mining Reclamation and mining policy Sustainable use of minerals

3. Central Case Study: Mining for … Cell Phones? • Cell phones and other high-tech products contain tantalum • Coltan: columbite + tantalum • Since 1998, the war in the • Democratic Republic of the Congo has killed 5 million • Soldiers controlled mining operations and forced farmers and others to work, while taking most of the ore • People entered national parks, killing wildlife and clearing rainforests, causing ecological havoc • Profits from coltan sales financed the war • Most tantalum from the Congo goes to China

4. Geology • We extract raw minerals from beneath our planet’s surface • Turning them into products we use everyday • Geology: the study of Earth’s physical features, processes, and history • A human lifetime is just the blink of an eye in geologic time • Our planet consists of many layers • Most geologic processes occur near the surface

5. Our plant consists of layers • Core: solid iron in the center • Molten iron in the outer core • Mantle: less dense, elastic rock • Aesthenosphere: very soft or melted rock • Lithosphere: harder rock that contains the mantle and crust • Crust: the thin, brittle, low-density layer of rock

6. Plate tectonics shapes geography • Plate tectonics: movement of lithospheric plates • Heat from inner Earth drives convection currents • Pushing the mantle’s soft rock up (as it warms) and down (as it cools) like a conveyor belt • The moving mantle drags the lithosphere • Continents have combined, separated, and recombined over millions of years • Pangaea: all landmasses were joined into one supercontinent 225 million years ago

7. Earth has 15 major tectonic plates Movement of these plates influences climate and evolution

8. Different types of plate boundaries Divergent plate boundaries Rising magma (molten rock) pushes plates apart Creating new crust Transform plate boundaries Two plates meet, slipping and grinding Friction spawns earthquakes along strike-slip faults Fault: a fracture in the crust

9. Tectonic plates can collide • Convergent plate boundaries: where plates collide • Subduction: one plate slides beneath another • Molten rock erupts through the surface in volcanoes • Ocean crust slides beneath continental crust • Two plates of continental crust collide, lifting material • Built the Himalaya and Appalachian Mountains

10. Tectonics creates Earth’s landforms • Tectonics builds mountains • Shapes the geography of oceans, islands, and continents • Some large lakes formed in immense valley floors • Topography created by tectonics shapes climate • Altering patterns of rain, wind, currents, heating, cooling, which …. • Affect rates of weathering and erosion and the location of biomes, which … • Affect evolution and extinction

11. The rock cycle alters rock • Rock cycle: the heating, melting, cooling, breaking, and reassembling of rocks and minerals • Rock: any solid aggregation of minerals • Mineral: any element or inorganic compound • Has a crystal structure, specific chemical composition, and distinct physical properties • Rocks help determine soil characteristics • Which influence the region’s plant community • Helps us appreciate the formation and conservation of soils, minerals, fossil fuels, and other natural resources

12. Different types of rocks • Magma: molten, liquid rock • Lava: magma released by a volcano • Igneous rock: formed when magma cools • Sediments: rock particles formed by physical erosion • Or chemically from precipitation of substances • Sedimentary rock: formed as sediments are pressed together and bound by dissolved materials • Compaction and transformation also create fossils • Metamorphic rock: rock deep underground is subjected to great heat or pressure, changing its form

13. The rock cycle

14. Geologic and natural hazards Most of Earth’s volcanoes and earthquakes occur along the “ring of fire” • Some consequences of plate tectonics are hazardous • Cause geologic hazards, such as earthquakes and volcanoes • Circum-Pacific belt: the “ring of fire” • An arc of subduction zones and fault systems

15. Earthquakes result from tectonic movement Buildings can bebuilt or retrofittedto decrease damage • Earthquake: a release of pressure along plate boundaries and faults • Some can do tremendous damage to life and property • Especially with loose or saturated soils • Cities built on landfills are vulnerable

16. Volcanoes • Lava can flow slowly or erupt suddenly • Pyroclastic flow: fast-moving cloud of gas, ash, and rock • Buried Pompeii in A.D. 79 • Volcano: molten rock, hot gas, or ash erupts through Earth’s surface • Can cool and create a mountain • Lava can exit in rift valleys, ocean ridges, subduction zones, or hot spots (holes in the crust)

17. Volcanoes have environmental effects • Ash blocks sunlight • Sulfur emissions lead to sulfuric acid • Block radiation and cool the atmosphere • Large eruptions can decrease temperatures worldwide • Mount Tambora’s eruption caused the 1816 “year without a summer” and killed 70,000 • Yellowstone National Park is the site of the most recent “mega-eruption” (640,000 years ago) • 2010’s eruption in Iceland disrupted air travel throughout Europe

18. Landslides are a form of mass wasting • Landslide: a severe, sudden mass wasting • Large amounts of rock or soil flow downhill • Mass wasting: the downslope movement of soil and rock due to gravity • Occurs naturally but can be caused by humans when soil is loosened or exposed • Mudslides: soil, rock, and water movement caused by saturated soil from heavy rains • Lahars: extremely dangerous mudslides • Caused when volcanic eruptions melt snow

19. Mass wasting events can be colossal and deadly

20. Tsunamis • Tsunami: huge volumes of water are displaced by: • Earthquakes, volcanoes, landslides • Can travel thousands of miles across oceans • Damage coral reefs, coastal forests, and wetlands • Saltwater contamination makes it hard to restore them • Agencies and nations have increased efforts to give residents advance warning of approaching tsunamis • Preserving natural vegetation (e.g., mangrove forests) decreases the wave energy of tsunamis

21. One dangerous tsunami On March, 2011, an earthquake off Japan triggered a massive tsunami • The earthquake and tsunami killed 9,000 people and caused hundreds of millions of dollars in damage • Radioactive material escaped from a nuclear power plant

22. We worsen the impacts of natural hazards • We also face other natural hazards: floods, coastal erosion, wildfire, tornadoes, and hurricanes • Overpopulation: people must live in susceptible areas • We choose to live in attractive but vulnerable areas • Coastlines, mountains • Engineered landscapes increase frequency or severity of hazards • Damming rivers, suppressing fire, clear-cutting, mining • Changing climate through greenhouse gases changes rainfall patterns, increases drought, fire, flooding, storms

23. We can reduce impacts of natural hazards • We can decrease impacts of hazards through technology, engineering, and policy • Informed by geology and ecology • Building earthquake-resistant structures • Designing early warning systems (tsunamis, volcanoes) • Preserving reefs and shorelines (tsunamis, erosion) • Better forestry, agriculture, mining (landslides) • Regulations, building codes, insurance incentives discourage development in vulnerable areas • Mitigating climate change may reduce natural hazards

24. Earth’s mineral resources We mine and process mineral resources for countless products

25. We use mined materials extensively A child born in 2009 will use 2.9 million lb of mined resources over its life We don’t notice how many mined resources we use The average American uses 37,000 lb of new minerals and fuels every year This level of consumption shows the potential for recycling and reuse

26. We obtain minerals by mining • We obtain minerals through the process of mining • Mining: in the broad sense, it is the extraction of any nonrenewable resource • Fossil fuels, groundwater, and minerals • Mining: in relation to mineral, it is the systematic removal of rock, soil, or other material • To remove the minerals of economic interest • Because minerals occur in low concentrations, concentrated sources must be found before mining is begun

27. We extract minerals from ores Metal: an element that is lustrous, opaque, and malleable and can conduct heat and electricity Ore: a mineral or grouping of minerals from which we extract metals Economically valuable metals from ore include: Copper, iron, lead, gold, aluminum Tantalite ore is mined, processed into tantalum, and used in electronic devices

28. We process metals after mining ore • Most minerals must be processed after mining • After the ore is mined, rock is crushed, and the metals are isolated by chemical or physical means • The material is processed to purify the metal • Alloy: a metal is mixed, melted, or fused with another metal or nonmetal substance • Steel is an alloy of iron and carbon • Smelting: heating ore beyond its melting point, then combining it with other metals or chemicals • Modifies the strength, malleability, etc., of metals

29. Environmental costs of processing minerals • Processing minerals has environmental costs • Most methods are water- and energy-intensive • Chemical reactions and heating to extract metals from ores emit air pollution and toxic wastes • Tailings: ore left over after metals have been extracted • Pollute soil and water • Contain heavy metals or chemicals (cyanide, sulfuric acid) • Surface impoundments: store slurries of tailings • Accidents release pollutants into the environment

30. We also mine nonmetallic minerals and fuels Sand and gravel provides fill and construction materials Phosphates provide fertilizer Limestone, salt, potash, etc., are also mined “Blood diamonds” are mined and sold to fund, prolong, and intensify wars in Angola and other areas Poor people are exploited for mine labor Substances are mined for fuel Uranium is used in nuclear power Coal, petroleum, natural gas, oil sands, oil shale, methane hydrate are not minerals (they are organic)

31. Economically important mineral resources

32. Mining methods and their impacts • Mining provides jobs and money for communities • It provides raw materials for products we use • Mining has environmental and social costs • Large amounts of material are removed during mining, disturbing lots of land • Different mining methods are used to extract minerals • The method used depends on economic efficiency

33. Strip mining removes surface soil and rock Strip mining: removal of layers of soil and rock to expose the resource just below the surface Overburden: soil and rock that is removed by heavy machinery After extraction, each strip is refilled with the overburden For coal, oil sands, sand, gravel Causes severe environmental impacts • Strip mining destroys natural communities over large areas and triggers erosion

34. Accesses deep pockets of a mineral through tunnels and shafts up to 2.5 miles deep Zinc, lead, nickel, tin, gold, diamonds, phosphate, salt, coal The most dangerous form of mining Dynamite blasts, collapsed tunnels Toxic fumes and coal dust Collapsed tunnels cause sinkholes Subsurface mining: underground work

35. Acid drainage • Acid drainage: sulfide in newly exposed rock reacts with oxygen and rainwater • Produces sulfuric acid • Sulfuric acid leaches toxic materials from rock • Flows into streams, killing fish and other organisms • Pollutes groundwater used for drinking and irrigation • Although acid drainage is natural, mining greatly accelerates it by exposing many new rock surfaces at once

36. Open pit mining creates immense holes • Used with evenly distributed minerals • Terraced, so men and machines can move about • Copper, iron, gold, diamonds, coal • Quarries: open pits for clay, gravel, sand, stone (limestone, granite, marble, slate) • Huge amounts of rock are removed to get small amounts of minerals • Habitat loss, aesthetic degradation, acid drainage • Abandoned pits fill with water • Acid drainage forms if sulfur is present

37. The world’s largest open pit mine This Utah mine is 2.5 mi across and 0.75 mi deep; almost half a million tons of ore and rock are removed each day

38. Placer mining uses running water Using running water, miners sift through material in riverbeds Used for gold, gems Debris washes into streams They become uninhabitable for wildlife Disturbs stream banks Causes erosion Harms plant communities

39. Mountaintop removal reshapes ridges Entire mountaintops are blasted off “Valley filling”: dumping rock and debris into valleys For coal in the Appalachian Mountains of the eastern U.S. Degrades and destroys vast areas Pollutes streams; deforests areas; causes erosion, mudslides, flash floods, biodiversity loss An area the size of Delaware has already been removed

40. Mountaintop removal is devastating Mine blasting cracks foundations and walls Floods and rock slides affect properties Coal dust and contaminated water cause illness Lung cancer, heart and kidney disease, pulmonary disorders, hypertension, death The poor people of Appalachia suffer while we benefit from coal-produced electricity Critics argue that valley filling violates the Clean Water Act In 2010, the EPA introduced rules to limit damage

41. Solution mining dissolves resources • Solution mining (in-situ recovery): resources in a deep deposit are dissolved in a liquid and sucked out • Water, acid, or other liquids are injected into holes • Used for salt, lithium, boron, bromine, magnesium, potash, copper, uranium • Less environmental impact than other methods • Less surface area is disturbed • Acids, heavy metals, uranium can accidentally leak or leach out of rocks and contaminate groundwater

42. Ocean mining We extract minerals (e.g., magnesium) from seawater Minerals are dredged from the ocean floor Manganese nodules: small, ball-shaped ores scattered across the ocean floor These reserves may exceed all terrestrial reserves Logistical difficulties in mining have kept extractions limited, so far

43. Restoring mined sites only partly works Governments in developed countries require companies to reclaim (restore) surface-mined sites Reclamation aims to bring a site to a condition similar to its pre-mining condition Remove structures, replace overburden, replant vegetation The U.S. Surface Mining Control and Reclamation Act (1977) mandates restoration Companies must post bonds to cover restoration costs

44. Restoration of mined sites Even on restored sites, impacts may be severe and long-lasting Complex communities are simplified Forests, wetlands, etc., are replaced by grasses Essential symbioses are eliminated and often not restored Water can be reclaimed Moderate the pH Remove heavy metals

45. The General Mining Act of 1872 Encourages metal and mineral mining on federal land Any citizen or company can stake a claim on, or buy (for $5 per acre), any public land open to mining The public gets no payment for any minerals found Supporters say it encourages a domestic industry that is risky and requires investment to locate vital resources Critics say it gives valuable public land basically free to private interests People have developed the land (e.g., for condominiums) that have nothing to do with mining Efforts to amend the act have failed in Congress

46. Minerals are nonrenewable and scarce Many minerals are rare and could become unavailable Once known reserves are mined, minerals will be gone For example, indium, used in LCD screens, might last only 32 more years Gallium (for solar power) and platinum (fuel cells) are also scarce Estimating how long a reserve will last is hard New discoveries, technologies, consumption patterns, and recycling affect mineral supplies As minerals become scarcer, prices rise

47. Years remaining for selected minerals Time periods can increase if more reserves are found or decrease if consumption increases

48. We can use minerals sustainably Recycling minerals addresses: Finite supplies Environmental damage 35% of metals were recycled in 2009 from U.S. solid waste 35% of our copper comes from recycles sources Recycling decreases energy use It also lowers greenhouse gas emissions • Aluminum from raw sources uses 20 times more energy than from recycled sources

49. We can recycle metals from e-waste • Electronic waste (e-waste) from computers, printers, cell phones, etc., is rapidly rising • Recycling keeps hazardous wastes out of landfills while conserving mineral resources • Cell phones can be refurbished and resold in developing countries • Or their parts can be dismantled or refurbished • Today, only 10% of cell phones are recycled • Recycling reduces demand for virgin ores and reduces pressure on ecosystems

50. Conclusion • Geologic processes shape Earth’s terrain and form the foundation for living systems • We depend on minerals and metals to make our products • Mineral resources are mined by various methods • Contribute to material wealth • But cause extensive environmental damage (habitat loss, acid drainage, etc.) • Restoration and regulations help minimize the environmental and social impacts of mining • Recycling and sustainable use prolong mineral resources