1. Geology and Nonrenewable Minerals
By Danya, Kimmy, and Porter

2. Case Study General Mining Law of 1872
Made to encourage exploration and mining and develop the West
Earn rights to mine the land if you pay to maintain it
Modified in 1992 – requires mining companies to post bonds to cover full cost of clean up in case they go bankrupt
Mining companies don’t like
Environmentalists want stricter cleanup requirements
On all US public lands except parks and wilderness
Oil and natural gas companies have to pay royalties for damages to environment but mining companies don’t

3. Key Concepts Earth’s major geological processes Rocks and rock cycles
Finding and extracting mineral resources
Harmful environmental effects
Limited supply of mineral resources

4. Geological Processes
Geology – science devoted to the study of dynamic processes occurring on Earth’s surface and in its interior
Surface and interior are constantly changing (slowly on a human time scale)
Energy from sun, Earth’s interior, and flowing water create continents, mountains, valleys, plains, and ocean basins

5. Earth’s Structure Three Zones:
Core – innermost zone, intensely hot, solid inner part surrounded by liquid core of molten material
Mantle – thick, solid zone surrounding the core, mostly solid rock but has an asthenosphere of partly melted rock
Crust – outermost and thinnest layer, consists of continental crust (underlies the continents) and oceanic crust (under ocean basins)

6. Internal and External Geologic Processes
Tectonic plates – various sized areas of Earth’s lithosphere that move slowly around the asthenosphere
15 plates
Move at about the rate at which fingernails grow
Plates colliding, breaking apart and sliding form mountains, ridges, and trenches
Theory of plate tectonics

7. Types of Boundaries
Divergent plate boundary – plates move in opposite directions
Convergent plate boundary – plates pushed together
Subduction – an oceanic and continental plate collide, oceanic plate is denser so it sinks below continental plate at subduction zone
Trenches form at boundaries between two converging plates
Transform fault – plates slide and grind past one another along a fracture in the lithosphere

8. Processes on Earth’s Surface
External processes – changes that occur from energy from sun and gravity
Erosion – material is dissolved, loosened, or worn away from one part of Earth’s surface and deposited elsewhere
Weathering – physical, chemical, biological processes that break down rocks and minerals into smaller pieces that can be eroded
Physical or mechanical weathering – large rock broken into smaller fragments (ex. Frost wedging)
Chemical weathering – chemicals decompose a mass of rock
Biological weathering – conversion of rock/minerals into smaller pieces through action of living things (ex. Lichens)
WHAT IS FROST WEDGING
lichens

9. Rocks and Rock Cycles
Mineral – element or inorganic compound that occurs naturally and is solid with a regular internal crystalline structure (ex. Salt, mica, quartz, diamond)
Rock – solid combination of one or more minerals that is part of Earth’s crust (ex. Limestone, quartzite)

10. Rock Types and the Rock Cycle
Igneous rock – forms below or on Earth’s surface when magma wells up from upper mantle and cools (Ex. Granite)
Sedimentary rock – forms from sediment when existing rocks are weathered and eroded into small pieces and transported by water, wind, or gravity. This builds up over time and pressure and dissolved minerals binds the sediments together.
Metamorphic rock – preexisting rock is subjected to high temperature, pressure, or chemically active fluids that change the properties and appearance of the rock
Rock cycle – interaction of physical and chemical processes that change rocks from one type to another

11. Nonrenewable Mineral Resources
Nonrenewable mineral resources – 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
-Metallic Mineral Resources (iron, copper, aluminum)
-Nonmetallic Mineral Resources (salt, clay, sand, phosphate, soil)
-Energy Resources (coal, oil, natural gas, uranium)
Ore – rock containing one or more metallic minerals to be mined profitably

12. 4 Categories of Nonrenewable Mineral Resources
Identified Resources (location, quantity, and quality known)
Undiscovered Resources (assumed to exist but location and quality unknown)
Reserves (identified resources from which a usable nonrenewable mineral can be extracted profitably at current prices)
Other Resources (undiscovered resources and resources not classified as reserves)

13. Identifying Promising Mineral Deposits (By Air)
Aerial photos and satellite images that reveal protruding rock formations (outcrops) associated with certain minerals
Planes equipped with…
Radiation-measuring equipment to detect radioactive minerals
Magnometer to find magnetic minerals
Gravimeter to measure differences in gravity produced by differences in density between an ore deposit and the surrounding rock

14. Identifying Promising Mineral Deposits (On the Ground)
Drilling a deep well and extracting core samples
Seismic surveys
Chemical analysis of water and plants

15. Removing Mineral Deposits
Shallow mineral deposits are removed by surface mining
Removing soil, subsoil, and other strata and then extracting a mineral deposit found fairly close to the earth’s surface
Deep deposits are removed by subsurface mining
Extraction of a metal ore or fuel resource such as coal from a deep underground deposit

16. Surface Mining
Mechanized equipment strips away the overburden (layer of soil and rock overlying a mineral deposit)
Discards it as waste material called spoils
Extracts about 90% of the nonfuel mineral and rock resources and 60% of the coal used in the U.S.

17. Types of Surface Mining
Open-pit mining – machines dig holes and remove ores, sand, gravel, and stone
Area strip mining (used where terrain is flat) – an earthmover strips away the overburden, and a power shovel digs a cut to remove the mineral deposit. The trench is then filled with overburden, and a new cut is made parallel to the previous one.
Mountaintop removal – uses explosives, massive shovels, and even larger machinery called draglines to remove the top of a mountain to expose seams of coal underneath a mountain
Contour strip mining (used on hilly or mountainous terrain) – a power shovel cuts a series of terraces into the side of the hill. An earthmover removes the overburden, and a power shovel extracts the coal.

18. Subsurface Mining Pros and Cons
Pros – disturbs less than 1/10 as much land as surface mining and often produces less waste material
Cons – leaves much of the resource in the ground and is more dangerous and expensive than surface mining (cave-ins, explosions, diseases)

19. Environmental Problems With Mining
Scarring and disruption of the land surface
Subsidence (collapse of land above underground mines)
Toxin-laced mining wastes blown or deposited elsewhere by wind or water erosion
Acid mining drainage
Mining has polluted about 40% of Western watersheds
Emission of toxic chemicals into the air
Wildlife exposed to toxic mining wastes when they leak from holding ponds

20. Life Cycle of a Metal Resource
Surface mining > metal ore > separation of ore from gangue > smelting > melting metal > conversion to product (sometimes recycled) > discarding of product

21. Environmental Impacts of Mining Ore
Environmental impacts of mining an ore are affected by its percentage of metal content (grade)
More accessible, higher-grade ores used first
Gradually takes more time, money , energy, water, and other materials for lower-grade
Right now, it does not cost companies/consumers much
Full-cost pricing (proposed by environmentalists and economists) includes the cost of environmental harm done in the price of goods made from minerals

22. Supply of nonrenewable minerals:
Depends on: actual/potential supply of minerals and the rate we use it
Economically depleted: when it costs more to find, extract, transport, process remaining deposit than mineral is worth
Five choices: recycle/reuse, waste less, find substitute, do without

23. Depletion
Depletion time: how long it takes to use up certain proportion (80%) of reserves of mineral
Short depletion time assumes no recycling, reuse, or increase in reserves
Longer depletion assumes recycling, reuse, and increase in reserves

24. Economics and Politics
Standard economic theory says in competitive free market plentiful mineral resource is cheap when supply exceeds demand
No longer applies very well in developed countries
In US, mining companies get depletion allowances amounting to 5-22% of gross income
Hardrock mining companies can buy public land at 1872 prices and pay no royalties to government
b/w US mining companies had $6 billion in government subsidies.
In 1900 the average copper ore=5% copper, and now=.5% and copper costs less

25. Mining Lower-Grade Ores
Limiting factors: increased cost of mining and processing larger volumes of ore, availability of fresh water, environmental impacts of land disruption
To improve mining technology use microorganisms for in-place mining (removes desired metals without disturbing surroundings) also reduces air pollution
Once ore deposit is located, wells are drilled and the ore is fractured
Then ore is inoculated with bacteria to extract desired metal
The well is flooded with water then pumped to surface

26. Cont.
Currently more than 30% of all copper produced (more than $1 billion per year) comes from biomining
However: processing is slow, it can take decades to remove same amount of material that takes other methods only months/years

27. Science Case Study
Nanotechnology: uses science and engineering at atomic/molecular levels to build materials with specified properties
Uses abundant atoms (carbon, oxygen, hydrogen)
Molecular economy: possible way of the future
Because particles get smaller, they also become more reactive/potentially toxic
Can also breach some natural defenses in our bodies
Buckyballs (soccer ball-shaped forms of carbon) caused brain damage to fish within 48 hours

28. Minerals from the Ocean
Only magnesium, bromine, sodium chloride are abundant enough to be extracted profitably from seawater
Deposits of minerals on continental shelf: sand, gravel, phosphates, sulfur, tin, copper, iron, tungsten, silver, titanium, platinum, diamonds
Manganese-fich nodules: found on deep-ocean floor
Might be sucked up by giant vacuum pipes or scooped up by buckets
Have not been developed yet because of increased cost and squabbles over ownership/distribution of profits
Could cause less environmental harm than land mining

29. Finding Substitutes
Materials revolution: silicon/new materials (ceramics and plastics) are being developed as replacements
Ceramics re: harder, lighter, stronger, longer lasting/ can withstand intense heat
Plastics and composite materials are being used in auto and aerospace industries
Cost less to produce, can be molded, don’t need paint

30. THE END