Civilizations exists by geological consent, subject to change without notice Will Durant

Geology and Mineral Resources Unit 11

Earth is a Dynamic Planet Geology: study of processes taking place in earth’s interior and on its surface. core: hot, solid center of planet mantle: surrounds core; rocky near interior, magma (molten rock) near exterior-asthenosphere crust: thinnest, outermost zone -continental crust (includes continental ocean shelf) -oceanic crust: 71% of crust lithosphere: crust and rigid mantle

Oceanic crust (lithosphere) Abyssal plain Continental slope Folded mountain belt Volcanoes Abyssal plain Abyssal floor Oceanic ridge Abyssal floor Abyssal hills Trench Craton Oceanic crust (lithosphere) Abyssal plain Continental slope Continental shelf Continental rise Mantle (lithosphere) Continental crust (lithosphere) Mantle (lithosphere) Figure 15.2 Natural capital: major features of the earth’s crust and upper mantle. The lithosphere, composed of the crust and outermost mantle, is rigid and brittle. The asthenosphere, a zone in the mantle, can be deformed by heat and pressure. Mantle (asthenosphere) Fig. 15-2, p. 336

Tectonic Plates Tectonic plates: plates of lithosphere created by convection currents in mantle move slowly on top of asthenosphere interaction of plate boundaries create earthquakes, volcanoes, mountains

The Earth’s Major Tectonic Plates Figure 15-4

Tectonic plate Inner core Spreading center Collision between two continents Oceanic tectonic plate Ocean trench 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 Figure 15.3 Natural capital: the earth’s crust is made up of a mosaic of huge rigid plates, called tectonic plates, which move around in response to forces in the mantle. 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

Plate Boundaries 3 types of plate boundaries: divergent: oceanic plates moving apart, molten rock flows up into the void, creates oceanic ridges (and new crust) ex. Mid-Atlantic Ridge convergent: colliding plates -subduction zone: denser oceanic plate sinks beneath a continental plate ex. “Ring of Fire” in Western Pacific Ocean -trench: colliding oceanic plates -mountains: colliding continental plates ex. Himalayas

Plate Boundaries Transform fault: plates sliding past each other ex. San Andreas Fault (California), New Madrid Fault (us)

Transform fault Rising magma Trench Volcanic island arc Transform fault Lithosphere Rising magma Subduction zone Lithosphere Lithosphere Asthenosphere Asthenosphere Asthenosphere Figure 15.4 Natural capital: the earth’s major tectonic plates. The extremely slow movements of these plates cause them to grind into one another at convergent plate boundaries, move apart from one another at divergent plate boundaries, and slide past one another at transform plate boundaries. QUESTION: What plate are you floating on? Divergent plate boundaries Convergent plate boundaries Transform faults Fig. 15-4b, p. 338

Internal Geologic Processes form mountains, volcanoes, earthquakes

Internal Geologic Processes volcanoes: weak area in crust -magma reaches surface through a fissure -release lava, ash, CO₂ and SO₂ gases ex. Mount Pinatubo earthquakes: movement of plates at transform boundaries -seismic wave: outward movement of energy from focus of quake -epicenter: earth’s surface above focus -tsunamis: ocean floor faults that suddenly rise or fall

External Geologic Processes driven by solar radiation, gravity weathering: physical, chemical, biological processes that break down rock into soil -rock: solid combination of one or more mineral -rock types: sedimentary, igneous, metamorphic

Erosion Transportation Heat, pressure, stress Magma (molten rock) Weathering Deposition Igneous rock Granite, pumice, basalt Sedimentary rock Sandstone, limestone Heat, pressure Cooling Heat, pressure, stress Magma (molten rock) Figure 15.8 Natural capital: the rock cycle is the slowest of the earth’s cyclic processes. The earth’s materials are recycled over millions of years by three processes: melting, erosion, and metamorphism, which produce igneous, sedimentary, and metamorphic rocks. Rock from any of these classes can be converted to rock of either of the other two classes, or can be recycled within its own class. QUESTION: List three ways that the rock cycle benefits your lifestyle. Melting Metamorphic rock Slate, marble, gneiss, quartzite Fig. 15-8, p. 343

Mineral Resources Mineral resource: useful inorganic material from crust; 2 major types: 1. metallic (aluminum, gold, lead, nickel, silver) -ore: rock containing concentration of valued mineral; may be high-grade (lots of mineral) or low-grade (small amounts of mineral) 2. nonmetallic (sand, limestone, talc, clay, salt) all minerals are considered nonrenewable country’s standard of living is tied to mineral availability

Mineral Use Al: packaging, structural material in cars, planes Fe: make steel for buildings, vehicles Cu: electrical, communications wiring Au: electronics, jewelry, medical implants Sand: glass, bricks, concrete Limestone: concrete, cement

General Classification of Nonrenewable Mineral Resources U.S. Geological Survey (USGS) classifies mineral resources into 4 major categories: Identified: known location, quantity, quality based on direct evidence. Undiscovered: potential supplies are assumed to exist. Reserves: identified resources that can be extracted profitably. Other: undiscovered resources not classified as reserves

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

Mining Methods of removing minerals, fossil fuels: surface (strip) mining: depends on resource sought, topography -involves removal of vegetation and overburden: overlying soil, rock -excess soil is dumped in spoils on land

Mining (cont’d) mountaintop removal: exposes coal seams -requires draglines (trucks with huge buckets) -spoils are dumped in valleys, rivers, streams open-pit: creates huge holes to remove metals (copper), sand, stone

Mining (cont’d) subsurface: underground metals, coal are removed through tunnels, shafts -requires explosives, exposure to poisonous gases, methane, lung-damaging dust

Environmental Effects of Mining (almost all degradation by mining is long-term) Strip mining: loss of topsoil, spoil banks are easily eroded. Return to ecosystem is slow. Mountain top removal: destroys forests, buries streams, toxic wastewater can release mercury, arsenic, loss of property value, well contamination. (mercury used to separate gold from stream sediments represents the 2nd worst human-related source of mercury pollution)

Environmental Effects of Mining Sub-surface mining: degrades biodiversity (especially in rainforest). Clean up is possible, but costly. Smelting: heating ores to release metals emits large quantities of sulfur dioxide-acid rain/acid mine drainage, green- house gases

Environmental Effects of Mining Cyanide Solution Mining/Heap-Leach Extraction: runoff of cyanide in gold extraction creates toxic ponds (can infiltrate groundwater)

Human Health Impacts of Mining Black-lung disease: inhalation of coal dust from subsurface mining Mercury poisoning: ingestion of Hg from fish Cyanide poisoning: exposure to smoke, or ingestion in water.

Mineral Availability Abundant: Al, Fe Scarce: Mn, Cr, Co, Pt (strategic metals) (-South Africa is largest producer of Cr, Pt -US relies on these for economy, military, but has limited reserves) US, Canada, Russia, South Africa, Australia supply most of world’s mineral resources China has most of rare earth metals

Minerals from the Ocean Occur in low concentrations Include Cu, Fe, W (tungsten), Pt, diamonds Rarely mined due to: -expense of extraction -rights disputes -concern about disruption to food chain -risk to food supply near coast

Black smoker White smoker Sulfide deposits Magma White clam White crab Figure 15.17 Natural capital: hydrothermal deposits form when mineral-rich superheated water shoots out of vents in solidified magma on the ocean floor. After mixing with cold seawater, black particles of metal compounds precipitate out and build up as chimneylike mineral deposits around the vents. A variety of organisms, supported by bacteria that produce food by chemosynthesis, exist in the dark ocean around these black smokers. White crab Tube worms Fig. 15-17, p. 350

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

Sustainable Mineral Use Substitution: silicon, plastics, ceramics can replace some metals Nanotechnology; create materials out of atoms, molecules Recycle, reuse: ex. recycling Al produces 95% less air, water pollution Reduce mining subsidies/increase subsidies for recycling Include cost of environmental damage from mining in prices of items.

Core Case Study: The Nanotechnology Revolution Nanotechnology uses science and engineering to create materials out of atoms and molecules at the scale of less than 100 nanometers. -little environmental harm -does not use nonrenewable resources -potential biological concerns (nanoparticles can cross the placenta, penetrate lung tissue, etc) Figure 15-1

US Mining Laws The General Mining Law of 1872: encouraged exploration, mining of minerals -enables corporations to obtain large tracts of public land cheaply without paying royalties or cleanup fees The Surface Mining Control and Reclamation Act of 1977: requires mined land to be restored to pre-mining conditions -proper disposal of mining wastes -re-contouring land -replanting vegetation Restored areas are known as brownfields

Exam Focus Major geologic processes occurring within the earth and on its surface Rocks, and how are they recycled by the rock cycle Type of formation from diverging ocean plates Type of formation from converging continental plates Example of transform fault Weathering from wind, water, heat

Exam Focus (cont’d) Definition of an ore (high and low-grade); definition of an alloy Classification of minerals (renewable/non) Types of mining and harmful environmental and human health effects results from each -specifically mining source of air and water pollution associated with heating ores -disease associated with subsurface mining Environmental effects of smelting Nonmetal used in glass, bricks, concrete

Exam Focus 4 reasons the ocean is not mined for minerals Ways minerals can be used sustainably Which mineral substitute still uses oil, fossil fuels Know the US Surface Mining Control and Reclamation Act of 1977