Geology and Nonrenewable Mineral Resources

 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.

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

Fig. 15-3, p. 337 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 Collision between two continents Tectonic plate Oceanic tectonic plate Oceanic crust

 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.

Figure 15-4

 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

Fig. 15-4, p. 338

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

 Weathering is an external process that wears the earth’s surface down. Figure 15-6

 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.

 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

 Examples are fossil fuels (coal, oil), metallic minerals (copper, iron), and nonmetallic minerals (sand, gravel). Figure 15-7

 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).

Fig. 15-8, p. 343 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

 The extraction, processing, and use of mineral resources has a large environmental impact. Figure 15-9

Fig , p. 344 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

 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.

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

 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

 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

 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

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 Scarring and disruption of the land surface  Subsidence  Toxin laced mining wastes  Air pollution  Acid deposition from smelting gases Figure 15-15

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.

 Depletion curves for a renewable resource using three sets of assumptions.  Dashed vertical lines represent times when 80% depletion occurs. Figure 15-16

 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

 Seawater  Continental shelf deposits  Hydrothermal vent deposits  Manganese nodules Figure 15-17

Fig , p. 351 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.

 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.

Figure 15-19