PLATE TECTONICS
Boundaries
Convergent: Converge to a point, magma moves down (moving towards each other)
On land, forms mountain ranges like Himalayas
On land moving toward ocean plate, ocean plate moves under because more density (can cause oceanic trenches)
Basalt makes up majority of ocean crust
Has earthquakes, no volcanoes
Ocean-ocean, ocean-continental, continental-continental
Ex. Ring of Fire
Divergent: Moving away, magma moves up and cools
Forms volcanoes + new landmass with magma eruptions (i.e volcanic islands)
Continental-continental
Ex. Mid Atlantic Ridge
Transform: Move parallel to one another
Many earthquakes around this area, no volcanoes
Continental-continental
Ex. San Andreas Fault
Pacific Plate is sliding past the North American Plate
Moves every ~120 years; it's been ~160 years since it moved (so “CA is doomed”)
Seafloor spreading: formation of ocean crust as a result of magma pushing upward and outward from the mantle to the surface
EARTHQUAKES
Focus: area where energy is released (where the earthquake beings)
Seismic waves travel outward in all directions from the focus
Epicenter: directly above the focus, on Earth’s surface
Measured by the Richter scale
1- very weak (not felt)
4- you can feel it
8- collapse of buildings
Recorded by a seismograph
Waves
Body waves
P waves: travel through earth; Caused by expansion & contraction of bedrock
Weaker shocks compared to S waves (but moves much faster)
Can travel through solids and liquids
The more rigid the material, the faster the p wave
S waves: produced when material moves vertically/horizontally and travels only within the uppermost layers of the earth
Can only travel through solids
Cannot be detected on the other side of Earth because they can't travel through the liquid outer core
Typically causes the most destruction
Lag time: differences in arrival times of P and S waves (Increases with distance from epicenter)
Surface waves: produce rolling / swaying motion
(NOT ON TEST)
Slower than P or S waves
Cause ground motion and damage
Occur when P and S waves transfer energy to surface
Rayleigh waves: ground shakes in an elliptical pattern (similar to ocean waves)
Love waves: horizontal; moves surface from side to side, perpendicular to p wave
Same frequency, > 1.0 Hz = Rayleigh wave is 2x as strong as love wave
Same frequency, < 1.0 Hz = Love wave is stronger than Rayleigh wave
Severity depends on:
Amount of potential energy that has been stored
Distance from epicenter (closer = stronger)
How far below the surface the movement occurred
Makeup of the rock material
VOLCANOES
~500 active volcanoes on Earth; at least 50 eruptions a year
Two types
Shield: Wide; lava oozes out slowly
Composite/Stratovolcanoes: Steeper & more violent
Lava: molten magma that emerges from the volcano; very slow
Pyroclastic flow: poisonous ash cloud that emerges during an eruption; travels over 100 mph (DEADLIER THAN LAVA)
Creates new land where life can flourish
Ring of Fire: ~90% of earthquakes; ~75% of volcanoes are located here (others are located at hotspots where the crust is thinner, ex Hawaii)
Boxing Day tsunami, 2004: > 250,000 people died
Caused by a megathrust earthquake (most powerful type)
Alaska, March 1964: NA’s biggest recorded earthquake
So powerful ground movements were observed in Florida (~4000 mi away)
In AK, there are ~1500 earthquakes every month
Earthquakes that occur in the ocean are shallower; gets deeper as you go inland
Creates a “dipping” feature - drops below the ground
Subduction: Sea floor slides under the land
As it moves, the top sedimentary layers are “scraped off” and pushed up (can form mountains)
Sea bed brings water in contact with the magma → creates magma plumes that create explosive volcanoes
TSUNAMIS
Tsu = harbor; nami = wave → harbor wave
Caused by volcanoes, landslides, or earthquakes under the ocean floor
Oceanic and continental plate collide → pressure builds
Oceanic plate (heavy) slides under the continental plate
Action is mirrored on the surface of the water (some water rises up while the rest goes down = wave) → Gravity pulls it back down
Seismic waves still travel through the water (up to 970 km/hr)
Extends much deeper than regular ocean waves
Can travel up to 16,000 km (carries a lot of water and has a lot of energy)
As they reach the shore, they slow down and pack together → water level rises
Earthquake with a magnitude > 7.5 to generate a massive tsunami
2004 tsunami was caused by a 9.0 tsunami
Can sometimes be predictable (ex. receding waves)
ROCKS
Types
Igneous
Intrusive: slow magma cooling (ex. granite)
Extrusive: rapid lava cooling (ex. obsidian)
Shiny and glasslike (no crystal formation)
Basalt: has gas bubbles (cools slower than obsidian)
Hard, no layers
Sedimentary
Classic: compacted broken rocks (ex. sandstone)
Conglomerate: sand and pebbles are visible
Chemical: compacted dissolved minerals (ex. limestone)
Often found near oceans and lakes (contains fossils)
Organic: bompacted biogenic matter (ex. coal)
Crumbly, layered
Metamorphic
Transformation of other rocks under intense heat and pressure
Relatively hard, may or may not have layers
Can have crystals
Foliated: layered (ex. slate)
Non-foliated: no layers (ex. marble; comes from limestone)
Rock Cycle: continuous process of formation, breakdown, and reformation or rocks
Igneous / sedimentary rock + deformation (heat & pressure) = metamorphic rock
Any rock + weathering & erosion = sediments
Sediments + lithification (compaction & cementation) = sedimentary rock (ex. coal)
Metamorphic / igneous rock + melting = magma
Magma + crystallization (cooling) = igneous rock
Connections to mining
Mineral deposits form from igneous processes (ex. cooling of magma chambers)
Sedimentary layers contain coal, oil, and gas reserves
Metamorphic processes concentrate valuable resources (like gemstones)
Structure of the Earth
Core: innermost zone; made mostly of iron and nickel (liquid outer layer and solid inner layer)
Mantle: above the core; contains magma
Magma: molten rock
Asthenosphere: layer of Earth located in the outer part of the mantle; composed of semi-molten rock
Lithosphere: outermost layer; includes the mantle and crust
Crust: chemically distinct outermost layer of the lithosphere
MINING
Earth’s crust = 45% O, 27% Si, 8% Al
Terms
Ore: concentrated accumulations of minerals from which economically valuable materials can be extracted
Overburden: soil and rock that covers the ore (land that needs to be removed before excavation)
Metals: Elements that can conduct electricity & heat (Cu, Ni, Al, Au)
Reserve: Known quantity of a resource that can be recovered
Spoils: materials removed to extract ore (the rock that is removed to access ore)
Spoil banks: holes that were filled with waste (cheap & easy; susceptible to erosion, causes sediment runoff)
Gangue: unwanted part of the ore; left over after extracting valuable minerals (after processing)
Tailings: piles of gangues (after the gangue is processed and finely ground)
Subsidence: gradual collapse of land due to underground coal mining
Rare earth metals: Sc, Y, lanthanides
Sc: alloys with Al, used in tech, baseball bats, and military jets
Widely distributed throughout rocks concentrated enough to get a commercially viable deposit
Types
Surface: cheap, safe, very destructive
Open-pit mining: large visible pit (ex. quarries)
Material is removed using large equipment
Resource is close to surface
Degrades landscape, affects air and water quality
Strip mining: removes strips of soil and rock
Similar to open-pit, but not as deep
Remove material, extract resource, return spoils / tailings
Area strip mining: flat terrain (can cause erosion)
Contour strip mining: mountainous areas (terraces are cut into the mountain)
Mountaintop removal: uses explosives to expose seams of minerals
Tailings are deposited in nearby regions
Causes deforestation and carbon emissions (burning of coal)
Placer mining: looking for minerals / metals in river sediments
Subsurface: expensive, dangerous, less damage to the environment
Underground coal mining: open shafts into the earth that “follows” the coal
AMD can drain out of mines
The ground above each shaft could collapse
Room and pillar: pillars of coal are left to support the cavern, creating “rooms” of coal (to prevent collapse)
Can cause water pollution and changes in groundwater flow patterns
Longwall mining: extracts minerals using a shearer
Good for ores that form horizontal deposits
Shaft mining: vertical tunnel straight into the deposit
Top of excavation is at the ground surface = shaft
Top of excavation is underground = winze / subshaft
Slope and drift mining (for coal)
Slope = diagonally sloping access shafts
Drift = Horizontal access tunnels
In situ: for radioactive U
Dredging: sand is removed from the ocean floor
Can be used to restore beaches
Destroys benthic ecosystems
Solution mining: pumping water into subsurface mineral deposits to bring dissolved minerals to the surface
Hydraulic fracturing: fracking
Creates fractures in rock by injecting a fluid that forces them open
Allows more oil and gas to flow out
Mine adit: entrance to an underground mine; serves as an entrance, drainage area, tunnel ventilation
Steps
Prospecting: finding places where there is ore
Mine exploration & development: whether the ore can be extracted economically
Mining: extraction of ore
Beneficiation: separate ore from rock
Smelting / refining: extract pure mineral from ore
Heat bleaching: takes low grade ore and extracts / concentrates the rare earth metals they contain
Transportation: brining mineral to market
Marketing & sales: finding buyers to sell the mineral
Impacts
Air: Dust particles, methane / CO2 (fossil fuels)
Soil: increases erosion (loss of vegetation), loss of topsoil in strip-mined regions
Biodiversity: habitat destruction
Health: Increased regulation to reduce health risks
Mine collapse, fire, asphyxiation, pneumoconiosis, asbestosis, silicosis, metal poisoning (especially Hg), radiation exposure
Black lung: comes from inhaling coal dust (type of pneumoconiosis - CWP)
Water: contamination as a result of tailings, accidental drainage of rivers/lakes
Acid Mine Drainage (AMD): formation of acidic water in heavy metals
Can react with water to form sulfuric acid
pyrite + O2 + H2O = Fe(OH)3 + SO4 + H+ (NOT ON TEST)
pyrite + oxygen + water = iron (iii) hydroxide + sulfate + hydrogen ions
Different AMD flows in different mines have different amounts of rare earth metals because different plants / sediments were compressed into the coal
Has a heavy rare earth metal : total metal ratio of ~50% (largest mine only has a ratio of ~12%)
Treatment:
Add lyme to AMD to form a slurry (thin mix of liquid and sludge that will flow)
Moves through a clarifier, where the heavier particles and sludge settle to the bottom
Water moves to get treated, sludge goes to geotubes
Massive expensive for treatment (Can’t be thrown into a landfill because it can contaminate groundwater supplies)
Lets the water flow out, but keeps solids in
One tube has ~ $11,000 of rare earth metals
Regulation
MSHA (Mine Safety and Health Administration) enforces health standards
Mining Law of 1872 (General Mining Act):
Allows individuals / companies to recover ores and fuels from federal lands
Few provisions for environmental protection
Surface Mining Control and Reclamation Act (1977)
Land must be minimally disturbed during coal mining, then reclaimed
Regulates the environmental effects of coal mining
Created two programs to reclaim abandoned mines and to regulate active mines
Related laws:
Clean Air Act: regulates air emissions
Clean Water Act: regulates discharge of pollutants into water
Superfund Act: tax on chemical / petroleum industries
Resources
Metallic (ex. Au, Cu, Pd), non-metallic (ex. sand, gravel), energy resources (ex. coal, U)
Mineral reserve: economically mineable part of a measured mineral resource
Proven reserve: offers >90% probability of successful extraction
Probable reserve: ≥50% probability of extraction
Possible reserve: unproved deposits; probability of successful extraction ≥10%
Sustainability
Recycling items with important heavy metals
Reducing the amount of heavy metals in products (more efficient usage)
Economic Mineralogy
Minerals are important in domestic & international commerce
Gold, silver, diamond = jewelry, electronics, grinding
Gypsum, calcite = construction
Copper, hematite = electronics, manufacturing
Clay minerals = clay industry
Biggest consumers: US, Japan, Europe
Biggest producers: South America, South Africa, Russia, CHINA
Blood diamonds
Diamonds mined in a war zone and sold to finance war efforts
Includes diamonds mined during civil wars in Angola, Sierra Leone, and the Ivory Coast
LITHIUM MINING
SANTA ANA WINDS
Formation
High pressure builds over the Great Basin
Compression and heating of air
Canyon & valley effects: narrow passages amplify wind speed
Characteristics
Hot and dry (relative humidity < 10%)
Strong and gusty (can knock down trees and power lines)
Prolonged (can last for several days)
Occurs from early fall - winter
Air over the inland deserts cools (denser and heavier, so it sinks)
High pressure systems form over deserts (pushes the air outward)
Pressure is higher inland and lower near the coast, so air moves from desert areas towards lower-pressure coastal areas
Wind compresses as it passes through mountain passes (increases heat and speed)
Because of these conditions, it is very easy for fires to start
Brings very dry air to coastal areas (dries vegetation and makes them more flammable)
Lower ignition temperature: requires less heat to ignite; a very small spark / ember can easily start a fire
As vegetation dries, it undergoes pyrolysis (organic material like cellulose breaks down into flammable gases → mixes with oxygen and ignites)
Strong winds can fan small sparks, creating larger fires (can also carry embers, starting spot fires)
Fast winds provide a continuous supply of oxygen = burns hotter and faster
Hot air creates warm conditions where fires spread easily
Compression heating (air is compressed due to increasing pressure at low altitudes) causes adiabatic heating
This allows the air to hold more moisture, but because there isn’t any water for it to hold, humidity drops even further
Impact on CA wildfires
Created the perfect conditions for fire spread
High temperatures amplified fire intensity
Additional dangers
Power outages (winds can damage power infrastructure, like power lines)
Increase in respiratory issues (inhalation of dust and smoke)
Psychological stress (from wildfire threats)
Reduce risks
Infrastructure improvements (underground power lines, fire-resistant materials)
Community preparedness (evacuation plans, firebreaks)
Early warning systems (monitoring weather patterns)
Satellite monitoring (for fire prediction)