Chapter 15

1. Chapter 15 Geology and Nonrenewable Mineral Resources

2. GEOLOGIC PROCESSES • The earth is made up of a core, mantle, and crust and is constantly changing as a result of processes taking place on and below its surface. • The earth’s interior consists of: • Core: innermost zone with solid inner core and molten outer core that is extremely hot. • Mantle: solid rock with a rigid outer part (asthenosphere) that is melted pliable rock. • Crust: Outermost zone which underlies the continents.

3. GEOLOGIC PROCESSES • Major features of the earth’s crust and upper mantle. Figure 15-2

4. Spreading center Collision between two continents Ocean trench Oceanic tectonic plate Oceanic tectonic plate Plate movement Plate movement Tectonic plate Oceanic crust Oceanic crust Subduction zone Continental 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 Mantle Two plates move towards each other. One is subducted back into the mantle on a falling convection current. Hot outer core Inner core Fig. 15-3, p. 337

5. GEOLOGIC PROCESSES • Huge volumes of heated and molten rack moving around the earth’s interior form massive solid plates that move extremely slowly across the earth’s surface. • Tectonic plates: huge rigid plates that are moved with convection cells or currents by floating on magma or molten rock.

6. The Earth’s Major Tectonic Plates Figure 15-4

7. The Earth’s Major Tectonic Plates • The extremely slow movements of these plates cause them to grind into one another at convergentplate boundaries, move apart at divergent plate boundaries and slide past at transform plate boundaries. Figure 15-4

8. Fig. 15-4, p. 338

9. GEOLOGIC PROCESSES • The San Andreas Fault is an example of a transform fault. Figure 15-5

10. Wearing Down and Building Up the Earth’s Surface • Weathering is an external process that wears the earth’s surface down. Figure 15-6

11. MINERALS, ROCKS, AND THE ROCK CYCLE • The earth’s crust consists of solid inorganic elements and compounds called minerals that can sometimes be used as resources. • Mineral resource: is a concentration of naturally occurring material in or on the earth’s crust that can be extracted and processed into useful materials at an affordable cost.

12. General Classification of Nonrenewable Mineral Resources • The U.S. Geological Survey classifies mineral resources into four major categories: • Identified: known location, quantity, and quality or existence known based on direct evidence and measurements. • Undiscovered: potential supplies that are assumed to exist. • Reserves: identified resources that can be extracted profitably. • Other: undiscovered or identified resources not classified as reserves

13. General Classification of Nonrenewable Mineral Resources • Examples are fossil fuels (coal, oil), metallic minerals (copper, iron), and nonmetallic minerals (sand, gravel). Figure 15-7

14. GEOLOGIC PROCESSES • Deposits of nonrenewable mineral resources in the earth’s crust vary in their abundance and distribution. • A very slow chemical cycle recycles three types of rock found in the earth’s crust: • Sedimentary rock (sandstone, limestone). • Metamorphic rock (slate, marble, quartzite). • Igneous rock (granite, pumice, basalt).

15. Erosion Transportation Weathering Deposition Igneous rock Granite, pumice, basalt Sedimentary rock Sandstone, limestone Heat, pressure Cooling Heat, pressure, stress Magma (molten rock) Melting Metamorphic rock Slate, marble, gneiss, quartzite Fig. 15-8, p. 343

16. ENVIRONMENTAL EFFECTS OF USING MINERAL RESOURCES • The extraction, processing, and use of mineral resources has a large environmental impact. Figure 15-9

17. Natural Capital Degradation Extracting, Processing, and Using Nonrenewable Mineral and Energy Resources Steps Environmental effects Mining Disturbed land; mining accidents; health hazards, mine waste dumping, oil spills and blowouts; noise; ugliness; heat Exploration, extraction Processing Solid wastes; radioactive material; air, water, and soil pollution; noise; safety and health hazards; ugliness; heat Transportation, purification, manufacturing Use Noise; ugliness; thermal water pollution; pollution of air, water, and soil; solid and radioactive wastes; safety and health hazards; heat Transportation or transmission to individual user, eventual use, and discarding Fig. 15-10, p. 344

18. ENVIRONMENTAL EFFECTS OF USING MINERAL RESOURCES • A variety of methods are used based on mineral depth. • Surface mining: shallow deposits are removed. • Remove overburden • Discard as waste material (spoils) • Examples: • Open-pit mining, area strip mining, contour strip mining, mountain-top removal • Subsurface mining: deep deposits are removed.

19. Open-pit Mining • Machines dig holes and remove ores, sand, gravel, and stone. • Toxic groundwater can accumulate at the bottom. Figure 15-11

20. Area Strip Mining • Earth movers strips away overburden, and giant shovels removes mineral deposit. • Often leaves highly erodible hills of rubble called spoil banks. • Succession slow after mining – no topsoil • Desertification in arid areas Figure 15-12

21. Contour Strip Mining • Used on hilly or mountainous terrain. • Unless the land is restored, a wall of dirt is left in front of a highly erodible bank called a highwall. Figure 15-13

22. Mountaintop Removal • Machinery removes the tops of mountains to expose coal. • Resulting waste rock and dirt are dumped into the streams and valleys below. • Causes flood hazards • Leaches toxic metals into waterways • Increasing in WV and KY Figure 15-14

23. Case Study – Kayford Mt, WV before after Larry Gibson on the issue A positive view

24. Mining Impacts • Scarring and disruption of the land surface • Subsidence • Toxin laced mining wastes • Air pollution • Acid deposition from smelting gases Figure 15-15

25. SUPPLIES OF MINERAL RESOURCES The future supply of a resource depends on its affordable supply and how rapidly that supply is used. • Never completely run out • Economic depletion – costs more to find, extract, transport, and process the remaining deposit than it is worth. • Options: • Recycle/reuse • Waste less • Use less • Find a substitute • Do without • A rising price for a scarce mineral resource can increase supplies and encourage more efficient use.

26. SUPPLIES OF MINERAL RESOURCES • Depletion curves for a renewable resource using three sets of assumptions. • Dashed vertical lines represent times when 80% depletion occurs. Figure 15-16

27. MINING TRENDS • Mining no longer a free market • Subsidized for depletion • Consumer pays via taxes • New technologies can increase the mining of low-grade ores at affordable prices, but harmful environmental effects can limit this approach. • Biomining – slow, but environmentally less destructive • Ocean mineral resources • Cost too much to extract • Squabbles over who owns them (i.e. deposits in international waters) • Environmental effects are poorly understood

28. Sources of Minerals from the Ocean • Seawater • Continental shelf deposits • Hydrothermal vent deposits • Manganese nodules Figure 15-17

29. Solutions Sustainable Use of Nonrenewable Minerals • Do not waste mineral resources. • Recycle and reuse 60–80% of mineral resources. • Include the harmful environmental costs of mining and processing minerals in the prices of items (full-cost pricing). • Reduce subsidies for mining mineral resources. • Increase subsidies for recycling, reuse, and finding less environmentally harmful substitutes. • Redesign manufacturing processes to use less mineral resources and to produce less pollution and waste. • Have the mineral-based wastes of one manufacturing process become the raw materials for other processes. • Sell services instead of things. • Slow population growth. Fig. 15-18, p. 351

30. Case Study: The Ecoindustrial Revolution • Growing signs point to an ecoindustrial revolution taking place over the next 50 years. • The goal is to redesign industrial manufacturing processes to mimic how nature deals with wastes. • Industries can interact in complex resource exchange webs in which wastes from manufacturer become raw materials for another.

31. Case Study: The Ecoindustrial Revolution Figure 15-19