Chapter 14 Geology and Nonrenewable Mineral Resources GEOLOGIC

Chapter 14 Geology and Nonrenewable Mineral Resources

GEOLOGIC PROCESSES Ø 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. Ø The earth’s interior consists of: l l l 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.

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

Te c pl toni at c e Collision between two continents ic n ecto t c i n Ocea plate Spreading Oceanic tectonic center plate nt Plate move ment Oceanic crust eme v o m ate Pl Subduction zone Continental crust Ocean trench Continental crust Material cools Cold dense as it reaches material falls the outer back through mantle Hot Mantle material convection rising cell through the 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. 15 -3, p. 337

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

The Earth’s Major Tectonic Plates Figure 15 -4

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

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

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

MINERALS, ROCKS, AND THE ROCK CYCLE Ø The earth’s crust consists of solid inorganic elements and compounds called minerals that can sometimes be used as resources. l 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.

General Classification of Nonrenewable Mineral Resources Ø The U. S. Geological Survey classifies mineral resources into four major categories: l l 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

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

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

GEOLOGIC PROCESSES The Rock Cycle Sedimentary rock formed by eroded layers pre-existing rock being deposited in layers. Ø Metamorphic rock formed when preexisting rock is under great heat & pressure Ø Igneous rock formed by pre-existing rock melting and cooling Ø

Rock Cycle

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

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 Use Solid wastes; radioactive material; air, water, and soil pollution; noise; safety and health hazards; ugliness; heat Transportation or transmission to individual user, eventual use, and discarding Noise; ugliness; thermal water pollution; pollution of air, water, and soil; solid and radioactive wastes; safety and health hazards; heat Transportation, purification, manufacturing Fig. 15 -10, p. 344

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ENVIRONMENTAL EFFECTS OF USING MINERAL RESOURCES Ø Minerals are removed through a variety of methods that vary widely in their costs, safety factors, and levels of environmental harm. Ø A variety of methods are used based on mineral depth. l l Surface mining: shallow deposits are removed. Subsurface mining: deep deposits are removed.

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

Area Strip Mining Ø Earth movers strips away overburden, and giant shovels removes mineral deposit. Ø Often leaves highly erodible hills of rubble called spoil banks. Figure 15 -12

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

Mountaintop Removal Ø Machinery removes the tops of mountains to expose coal. Ø The resulting waste rock and dirt are dumped into the streams and valleys below. Figure 15 -14

Mining Impacts Ø Metal ores are smelted or treated with (potentially toxic) chemicals to extract the desired metal. Figure 15 -15

SUPPLIES OF MINERAL RESOURCES Ø The future supply of a resource depends on its affordable supply and how rapidly that supply is used. Ø A rising price for a scarce mineral resource can increase supplies and encourage more efficient use.

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

SUPPLIES OF MINERAL RESOURCES Ø New technologies can increase the mining of low-grade ores at affordable prices, but harmful environmental effects can limit this approach. Ø Most minerals in seawater and on the deep ocean floor cost too much to extract, and there are squabbles over who owns them.

Getting More Minerals from the Ocean Ø Hydrothermal deposits form when mineral-rich superheated water shoots out of vents in solidified magma on the ocean floor. Figure 15 -17

USING MINERAL RESOURCES MORE SUSTAINABLY Ø Scientists and engineers are developing new types of materials as substitutes for many metals. Ø Recycling valuable and scarce metals saves money and has a lower environmental impact then mining and extracting them from their ores.

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

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

Case Study: The Ecoindustrial Revolution Figure 15 -19