Geology & Minerals Chapter 16

Geology The study of dynamic processes occurring on Earth’s surface & in its interior Core- innermost; intensely hot; inner solid surrounded by semisolid (molten) Mantle- surrounds core; most is solid rock Crust- outermost; thinnest layer

Movements in the Mantle Convection currents- movement of large amounts of rock (due to heat) in loops through the mantle like conveyor belt Mantle plume- mantle rock flows upward (like smoke from chimney)

Plate Tectonics Tectonic plate- huge rigid plate made of lithosphere Lithosphere- crust & uppermost mantle Asthenosphere- molten area of mantle beneath lithosphere Theory of Plate Tectonics- explains movement of plates & processes that occur where plates meet Importance- explains volcanoes, earthquakes, climates, mineral deposits, & patterns of evolution

Plate Boundaries Divergent boundary- plates move apart; results in rift valley surrounded by mountain range (typically in middle of ocean basin); new crust is created Transform Fault boundary- plates slide past each other without creating or destroying crust

Convergent boundary- plates move toward each other; subduction occurs; older crust is recycled into mantle Oceanic – Oceanic- trench (older crust is subducted); volcanic island arc Oceanic – Continental- trench (oceanic is subducted); continental volcanic arc (folded mountains) Continental – Continental- mountain range (isostatic balance – crust is too buoyant to be subducted)

Erosion & Weathering Erosion- process of dissolving, loosening, or wearing away of crust; material is deposited at new location Weathering- physical, chemical, biological processes that break down rocks & minerals

Types of Weathering Mechanical- breaks rock into smaller pieces Frost wedging- freeze/thaw cycle of water in the cracks of rocks Chemical- chemical reactions change rocks into simpler substances Water is most common agent Biological- rocks/minerals changed into smaller pieces by living things Lichen

Earthquakes Movement along a fault Shaking, damage to people, buildings, bridges, overpasses, dams, pipelines Rockslides, fire, flooding, tsunamis

Reducing the Hazards Locate active fault lines Map high-risk areas & establish building codes for building placement & design Increase research on prediction More earthquake resistant structures

Volcanoes Eruption- release of ejecta, lava, & gas into environment Cooler climate due to ash in atmosphere, covering of roads & villages, fire Scenery (Crater Lake, mountains), highly fertile soil (weathering of lava)

Reducing the Hazards Identify high-risk areas Develop evacuation plans Develop warning system

Rocks & Minerals Mineral- solid, inorganic substance with definite chemical composition & crystalline structure Rock- mineral or mineral-like matter that is naturally occurring Igneous- cooling & hardening of magma or lava Sedimentary- compaction & cementation of sediments Metamorphic- high temperatures/pressures or chemical reactions are applied to existing rock

Rocks All minerals are rocks. All rocks are NOT minerals. Igneous- granite, pumice, obsidian Sedimentary- sandstone, limestone, rock salt Metamorphic- slate, marble

Rock Cycle DRAW YOUR OWN. Be sure to include: Compaction/cementation weathering/erosion Heat/pressure/chemical rxn Cooling/hardening Melting Sediments Magma/lava All 3 types of rocks

Mineral Resources Nonrenewable materials that can be extracted from Earth’s crust Ore- can be mined for profit Identified resource- known location, quantity, quality Undiscovered- assumed to exist; unknown specific location, quantity, quality Reserves- identified areas where ore exists Other resources- undiscovered, identified but not as reserve

Locating Deposits Aerial photographs Satellite images Radiation measuring equipment Magnetometer- changes in magnetic field Gravimeter-density differences Seismic surveys- composition of buried layers Chemical analysis- leaching

Removing Deposits Subsurface mining- removes deeper deposits Surface mining- removes shallow deposits Open-pit mining- machine digs large hole Dredging- chain buckets & draglines scrape underwater Area-strip mining- used in flat areas, overburden is removed, power shovel removes mineral

Contour strip mining- (mountainous terrain) terraces cut, overburden removed, power shovel removes mineral Mountaintop removal- explosives, massive shovels, machinery remove top of mountain to expose mineral

Environmental Effects of Mining Scarring & disruption of land surface Subsidence Erosion of soil Large amounts of toxic solid waste Acid mine drainage

Economic Depletion Costs more to find, extract, transport, process remaining deposit than it is worth Choices: Recycle or reuse existing supplies Waste less Use less Find a substitute Do without

Free Market Plentiful resource = cheaper price Scarce resource = higher price Encourages exploration for new deposits Development of better mining technology Profitable to mine lower-grade ores Search for substitute Promote resource conservation

Why it does NOT work… Industry & government control supply & demand & prices Economic problems hinder new supplies of mineral resources

Mining on Public Lands