This lecture will help you understand:

1. This lecture will help you understand: • How plate tectonics and the rock cycle shape the Earth • Geologic hazards • Mineral resources • Mining methods and impacts • Sustainable use of minerals

2. Central Case: Mining for…cell phones? • Cell phones and other high-tech products must contain tantalum. • Coltan: tantalum found with another mineral (columbite) • In eastern Congo, men dig in streambeds, panning for coltan. • The Democratic Republic of the Congo has been at war since 1998. • 5 million people died and millions fled. • Soldiers seized control of mining operations and forced farmers and others to work, while taking most of the ore. • The war caused ecological havoc, dead wildlife, and deforestation. • Profits from coltan sales financed the war. • Corporations assure consumers they did not use coltan from the Congo.

3. We use raw materials from the Earth • We take raw materials from the lithosphere and turn them into products. • The physical processes in the lithosphere shape Earth’s landforms. • Geology: the study of Earth’s physical features, processes. and history • Two processes are fundamentally important: the rock cycle and plate tectonics.

4. The rock cycle Rock cycle: heating, melting, cooling, breaking, and reassembling of rocks and minerals Important in the formation and conservation of soil, mineral resources, fossil fuels, and other resources Rock: any solid aggregation of minerals Affect soils and influence a region’s plant community Mineral: any naturally occurring solid element or inorganic compound A crystal structure A specific chemical composition Distinct physical properties

5. Rock cycle

6. Igneous rock Magma: the molten, liquid state of rock Lava: magma released from the lithosphere Igneous rock: forms when magma cools Two classes, depending on how rock solidifies: Intrusiverock: magma that cools slowly below Earth’s surface (i.e., granite) Extrusiverock: magma ejected from a volcano (i.e., basalt)

7. Sedimentary rock Sediments: particles of rock are blown by wind or washed away by water Sedimentary rock: sediments are pressed together (compaction) or dissolved minerals seep through sediment layers and bind sediment particles (cementation) Lithification: formation of rock through the processes of compaction and cementation

8. Formation of sedimentary rock Sedimentary rock is classified by the way it forms. Clastic sedimentary rock: forms from physically eroded material (sandstone, shale) Chemical sedimentary rock: formed as dissolved minerals precipitate from water or as calcite settles to ocean bottoms (Limestone and rock salt) Physical compaction and chemical transformation form: Fossils Fossil fuels

9. Metamorphic rock Metamorphic rock: great heat or pressure on a rock changes its form Deep underground, high temperatures reshape crystals and change a rock’s appearance and physical properties. Foliated rock: heat and pressure causes layers (slate) Nonfoliated rock: not layered (marble)

10. Earth consists of layers • Crust: a thin, brittle, low-density rock • Covers Earth’s surface • Mantle: thick layer of denser rock • Aesthenosphere: the upper mantle containing soft rock, melted in some areas • Core: dense, consists mostly of iron • Earth’s heat drives convection currents in the mantle • Pushes soft rock upward and downward… • Dragging large plates of lithosphere • Plate tectonics: the movement of lithospheric plates

11. Earth’s layers

12. The Earth has 15 major tectonic plates… …that move 2-15 cm (1-6 in.) per year. Movement of these plates influences climate and evolution.

13. Pangaea: the supercontinent At least twice in Earth’s history, all landmasses were joined in one supercontinent. Pangaea: the supercontinent that occurred 225 million years ago

14. There are 3 types of plate boundaries • Divergent plate boundaries: magma surging upward to the surface pushes them apart, creating new crust as it cools and spreads • Transform plate boundary: two plates meet, slipping and grinding alongside one another • Friction spawns earthquakes along slip-strike faults

15. Tectonic plates can collide Convergent plate boundaries: when plates collide Subduction: one plate of crust slides beneath another Magma erupts through the surface in volcanoes, forming volcanic mountain ranges (the Cascades in Washington). Two colliding plates of continental crust may lift material from both plates. Resulted in the Himalaya and Appalachian mountains

16. Tectonics creates Earth’s landforms • The processes of plate tectonics build mountains; shape oceans, islands, and continents; and create earthquakes and volcanoes. • Topography shapes climate by altering patterns of rainfall, wind, ocean currents, heating, and cooling. • These patterns affect weathering and erosion and the ability of plants and animals to inhabit different regions (biomes). • Helps shape evolution by causing extinctions through limiting suitable habitat

17. Geologic hazards

18. Earthquakes result from movement • Earthquakes: places in the Earth’s crust (faults) where built-up pressure is relieved • Most earthquakes are not felt, but some do enormous damage. • Cities built on landfills are very vulnerable. • To minimize damage: build strong buildings with built-in flexibility

19. Volcanoes arise from rifts, subduction, or hot spots • Volcano: where molten rock, hot gas, or ash erupts through Earth’s surface • Can create a mountain • Lava can extrude in a rift valley, midocean ridges, or over subduction zones • Hot spots: plugs of molten rock erupt through the crust • Create island chains

20. Effects of volcanoes • Pyroclastic flow: a fast-moving cloud of toxic gas, ash, and rock • Mount Vesuvius erupted and buried Pompeii in 79 A.D. • Ash blocks sunlight. • Sulfuric emissions cause a haze that cools the atmosphere. • Cause crop failures

21. Landslides are a form of mass wasting • Mass wasting: the downslope movement of soil and rock due to gravity • Landslide: A severe and often sudden instance of mass wasting, where large amounts of rock or soil collapse and flow downhill • Occurs naturally, but is also caused by human practices that expose or loosen soil • Mudslides: heavy rains saturate the soil and cause movement of soil, rock, and water • Lajars: mudslides caused when volcanic eruptions melt snow and sends volumes of mud downslope

22. Mass wasting can be devastating • In 1998, in Nicaragua and Honduras, over 11,000 people died from mudslides. • In 1985, over 21,000 people died from a lahar that buried the town of Armero, Colombia.

23. Tsunamis: an immense wave of water • A tsunami can travel thousands of miles across oceans. • Triggered by earthquakes, volcanoes, or landslides • In 2004, 230,000 people were killed in countries around the Indian Ocean from a massive tsunami. • The U.S. also has had tsunamis. • To decrease impacts, natural vegetation should be left in place (i.e., mangrove forests).

24. We can worsen natural hazards • People face other natural hazards: • Floods, coastal erosion, wildfire, tornadoes, hurricanes • We worsen the impacts of natural hazards. • People live in susceptible areas due to population pressure or choice. • Use of landscapes increases the frequency or severity of hazards: damming rivers to control floods, suppressing natural fires, clear-cutting forests. • Climate change will change precipitation, leading to more floods, fire, mudslides, etc.

25. We can mitigate natural hazards • Thoroughly understand geology and ecology • Thoughtful use of technology, engineering, and policy • Earthquake-resistant buildings • Early warning systems • Conserving coastal forests, reefs, marshes • Better forestry and mining practices • Zoning regulations and building codes • Mitigating climate change

26. Minerals and mining • Geologic processes and catastrophes influence the distribution of rocks and minerals. • We depend on a wide variety of minerals for products and technologies. Minerals are non-renewable, so we need to conserve them and mitigate environmental and social impacts of mining.

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

28. We also mine nonmetallic minerals and fuels • Nonmetallic minerals include sand, gravel, phosphates, limestone, gemstones. • People in developing countries often suffer war and exploitation because of the developed world’s appetite for minerals. • Substances are mined for fuel. • Uranium for nuclear power • Coal, petroleum, natural gas are not minerals (they consist of organic matter), but they are also mined.

29. Economically useful mineral resources

30. A mining method: strip mining • Layers of surface soil and rock are removed to expose the mineral resource. • Overburden: overlying soil and rock that is removed by heavy machinery • After resource extraction, each strip is refilled with the overburden. • Used for coal, sand, gravel, and oil sands • Destroys natural communities over large areas, triggers erosion • Acid drainage: sulfuric acid forms and flows into waterways

31. A mining method: subsurface mining • Accessing deep concentrations of a mineral through tunnels and shafts • The deepest mines extend 4 km (2.5 mi) • Used for zinc, lead, nickel, tin, gold, copper, diamonds, phosphate, salt, coal • The most dangerous form of mining • Injury and death from dynamite blasts and collapsed tunnels • Toxic fumes and coal dust can be fatal • Acid drainage and polluted groundwater

32. A mining method: open pit mining • Used with widespread, evenly distributed minerals • Terraced so men and machines can move • Used for copper, iron, gold, diamonds, coal, clay • Quarries: open pits for clay, gravel, sand, stone (limestone, granite, marble, slate) • Huge amounts of waste rock are removed to obtain small amounts of minerals. • Habitat loss, aesthetic degradation, acid drainage, fill with toxic water One Utah mine is 4 km (2.5 mi) across and 1.2 km (0.75 mi) deep.

33. A mining method: placer mining • Using running water, miners sift through material in modern or ancient riverbeds. • Congo’s coltan miners, California’s gold rush of 1849 • Used for gold, gems • Debris is washed into streams, making them uninhabitable for fish and other life. • Disturbs stream banks, causes erosion, and harms riparian plant communities

34. A mining method: mountaintop removal • Entire mountaintops are blasted off and the waste is dumped into valleys. • Mainly for coal in the Appalachian Mountains • Economically efficient • In 2002, President Bush loosened regulations, allowing dumping of waste into valleys and streams. • Deforestation, degrades and destroys vast areas, pollutes waterways, erosion, mudslides, flash floods An area the size of Delaware has already been removed.

35. Mountaintop removal is socially devastating • Mine blasting cracks foundations and walls. • Floods and rock slides affect properties. • Overloaded coal trucks speed down rural roads. • Coal dust causes illness. • Local politicians do not help. • High efficiency mining reduces the need for workers.

36. A mining method: undersea mining • Minerals are extracted from the ocean floor using large hydraulic dredges. • Used for sulfur, phosphorite, calcium carbonate (for cement), silica (insulation and glass), copper, zinc, silver, gold • Manganese nodules: small, ball-shaped ores scattered across the ocean floor • Mining them is currently uneconomical.

37. Restoration of mined sites • In some countries (i.e., U.S. and Canada), companies must “reclaim” (restore) vegetation on mined sites after mining. • Other nations (i.e., Congo) have no regulations. • The U.S. 1977 Surface Mining Control and Reclamation Act mandates that companies: • Must post bonds before mining to ensure restoration • Remove structures, replace overburden, and replant vegetation when mining is complete

38. Restored sites can still have problems • Complex communities are simplified. • Forests, wetlands, etc., are replaced by grasses. • Essential symbioses are eliminated and often not restored.

39. The General Mining Act of 1872 • Government policy plays a role in mining through this controversial law. • It encourages mining on federal lands by letting any U.S. citizen stake a claim on any public land for a few dollars per acre. • The public gets no compensation for any minerals found. • Once a person owns the land, that land can be developed for any reason, having nothing to do with mining. • Supporters of the Act say it encourages a domestic industry that is risky and provides essential products. • Critics say it virtually gives the land for free to private interests. • So far, efforts to amend the Act have failed in Congress.

40. Minerals must be processed to be useful • Alloy: a substance formed by mixing, melting, and fusing minerals (i.e., steel = iron + carbon) • Smelting: removes metal from ore using heat and chemicals • Melting and reprocessing the metal produces the strength, malleability, or other characteristics desired. • Processing minerals impacts the environment. • Water and energy intensive • Toxic air pollution • Tailings: heavy metals and chemicals in the ore left after the metal has been extracted

41. Minerals are non-renewable and scarce • Once we have mined all known reserves, minerals will be gone. • i.e., Indium, used in LCD screens, might only last 32 more years • Reserve estimates, however, are uncertain. • New discoveries, technologies, consumption patterns, and recycling will affect mineral supplies.

42. We can use minerals sustainably • Challenges facing us regarding minerals • Finite supply and environmental damage • The solutions? Recycling • i.e., 72% of our lead comes from recycled materials • Steel, iron, platinum, etc., for auto parts • Gold, nickel, germanium, tin, and chromium • 50% of aluminum is recycled • Affected by recycling efforts and facilities

43. Conclusion Plate tectonics and the rock cycle shape Earth’s terrain and form the foundations for biotic patterns. Geologic processes can threaten our lives and property. We mine mineral resources by various methods. We need to minimize the environmental and social impacts of mining. Maximize recycling and sustainable use of minerals