Ch 8 – Earth Systems

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Warm-up: Do the MathPlate Movement

If two cities lie on different tectonic plates, and those plates are moving so that the cities are approaching each other, how many years will it take for the two cities to be situated adjacent to each other?

Los Angeles is 630 km (380 miles) southeast of San Francisco. The plate under Los Angeles is moving northward at about 36 mm per year relative to the plate under San Francisco.

Given this average rate of plate movement, how long will it take for Los Angeles to be located next to San Francisco?

Do the Math - ANSWER

Geologic Earth• Magma moves in convection

cells (hot, less dense material rises, cooler more dense material falls)

• Large plates flow on top of molten magma creating the geologic features we see on earth.– Continental crust is less dense

than oceanic crust, so when they meet, continental crust will be thrust above oceanic crust

Plate Tectonics• The earth is composed of

12 tectonic plates that move very slowly over the surface of the earth– Composed of the crust, the

outermost part of the mantle (together called the lithosphere)

– Most geologic activity occurs at the plate boundaries

Divergent Boundaries• Plates moving AWAY from each,

creating new land • The earth sinks forming a valley or

magma to rises into the open space creating a ridge– mid ocean ridges – A deep underwater

mountain range formed by diverging oceanic plates• Example: Mid-Atlantic Ridge

– rift valleys - A long, straight, deep valley produced by the separation of crustal plates• Example: Great Rift Valley

Convergent Boundaries• Plates move toward each other, often destroying

land • Ocean- continental and ocean-ocean plates

collide forming:– Subduction zones (when the MORE dense plate is

pushed underneath the LESS dense plate) forming volcanoes and a trench

– Ex: The Mariana Trench, Indian Plate and Burma Plate (site of 2004 earthquake and Tsunami).

• Continental-Continental plates collide resulting in:– Compression (when they mush together and push up)

forming mountain ranges– Ex: Himalayan Mountains (Indo-Australian Plate and

the Eurasian Plate)

Transform Fault• When plates slide past each other• Result in major fault lines where

earthquakes occur– Pressure builds up and when that

pressure if released suddenly, an earthquake occurs

– Examples: • North American and Pacific plate slide

paste each other forming the San Andreas fault

• Motagua Fault in Guatemala

Hot Spot• An area where the

underlying mantle is abnormally hot, causing the plate above it to melt

• Form chains of volcanoes – Examples:

» Hawaiian Islands» Yellowstone» Galapagos Islands

Ring of Fire• Extremely

geologically active zone around the Pacific plate

About 90% of the world's earthquakes and 89% of the world's largest earthquakes occur along the Ring of Fire

Volcanoes• An opening in the earth which allows hot

magma, gases and ash to reach the surface of the earth

• Usually occur at convergent and divergent plate boundaries and hot spots

• Forms new land which eventually leads to new habitat

• Warning signs: gas releases, small earthquakes moving toward the volcano, changes in the shape of the volcano

• Evacuating the area is the best way to save lives.• Pyroclastic flows (hot mixture of gas, ash and

rocks) are the most dangerous

Volcanoes – Environmental Impacts• Pros:

– Creates new land– Releases nutrients (ash fertilizes soil)– Commercially valuable products (pumice, metals,

stones)• Cons:

– Fast moving lava and gases threaten human lives– Lava and ash damage property and impact the economy– Ash can reduce agriculture yields and reduce incoming

sunlight globally (reduces global temps)– Volcanoes are natural sources of CO2 (global warming)

and SOx (acid rain and smog)– Can cause earthquakes, tsunamis, landslides, and mud

slides

Earthquakes• Occur when plates move suddenly due to a build-

up of pressure• Stored energy is released as seismic waves that

can damage property and threaten lives

• Occur at all types of plate boundaries and fault lines within plates

• Warning signs: usually none, earthquakes are very difficult to predict

• Strong building codes and emergency planning are the best way to protect lives

Earthquakes - Impacts• Primary: earth moving and shaking

• Secondary: landslides, avalanches, tsunamis, fires, floods, soil liquifaction

• Environmental: – Collapse of buildings and loss of human life

– Creation of toxic dust and debris that threaten humans and other life (asbestos, heavy metals,

– Loss of sanitation systems leading to the spread of water-borne diseases and illness

– Disruption of human systems (energy, water, transportation, food distribution, etc)

– Economic impacts associated with damage, loss of productivity, and clean-up

Tsunamis• Large series of waves caused by

sudden movement in the ocean floor (usually an earthquake, volcano, landslide or glacier fall)

• Wave is often undetectable out at sea, but grows into a wall of water as ocean becomes more shallow close to shore

• Often occur far from the initial disturbance

• Warning signs: Detection of a major disruption like an earthquake or volcano. Water being sucked rapidly out to sea

• Best way to minimize loss of life is to have an effective warning system so people can evacuate

Tsunamis - impacts• Major flooding of coastal and low-lying areas• Major loss of buildings and other infrastructure• Loss of life from drowning or impact with debris• Longer term impacts include:

– Loss of sanitation leading to the spread of water-borne diseases and illness

– Disruption of human systems (energy, water, transportation, food distribution, etc)

– Economic impacts associated with damage, loss of productivity, and clean-up

– Environmental Impacts– Contamination of water supplies with salt

water– Loss of beach areas due to erosion– Disruption to fishing populations

The Rock Cycle

Geology Big Ideas• Geologic disasters are a natural part of living

on earth• Preparedness is a key to survival• Disaster often offer an important period of

growth and renewal: new nutrients, new land, open niches, etc

MINING AND RESOURCES

Composition of the Earth

The crust is composed primarily of OXYGEN (O2)

The atmosphere is composed primarily of NITROGEN (N2)

AtmosphereCrust

How is ORE Removed?• SURFACE: http://www.youtube.com/watch?v=2LQwxTm94Ps

– Removal of the earth on top of resources to access minerals– Safer but causes more habitat destruction– Examples include: Open-Pit Mining, Dredging, Area Strip Mining,

Contour strip mining• SUBSURFACE http://www.youtube.com/watch?v=Bk-jrbCi7Sc&feature=related

– Digging underground creating tunnels and rooms underground to obtain minerals

– Less direct habitat destruction, but much more dangerous– Examples include: underground coal mining: long walling and

room and pillar

Mining Vocabulary• Overburden – rock and soil over a desired resource

(basically habitat )• Spoils – disturbed earth left over from removing

overburden from a mining site• Ore – rock that contains a valuable resource (mixture of

resource, rock and other solids)• Gangue - the part of the ore that is not the desired

resource (waste)• Tailings - the leftover material from separating the gangue

from the valuable material (theoretically all gangue, but traces minerals remain) Often stored in tailing ponds

Environmental Impacts of SURFACE MINING

• Disruption of habitat and land surface• Increased erosion from loss of vegetation and disruption of soil• Wind or water erosion of toxin-laced waste• Acid mine drainage• Loss of wildlife due to habitat loss/fragmentation and toxic releases

Most surface mining land can be restored but is costly and never quite the same

Acid Mine Drainage (AMD)• When rocks are exposed to the elements (wind

and water) acid runoff is created• It is a somewhat natural process (rain and the

exposed rocks just make acid mine drainage) but we expose the rocks.

1. Water flowing through mine tailings collects sulfuric acid and iron deposits

2. Acidic water leaches out of mining areas into watersheds

3. Contaminates water supplies; decreases pH of surface waters

AMD Chemistry• Rock called pyrite (FeS2) is often found in coal beds• When pyrite is exposed to water, Iron ions (Fe2+ and Fe3+) and

sulfate ions (SO42-) are released

• Sulfate ions increase the number of H+ ions in water, decreasing the pH of the water

• Acidic pH increases the leaching of toxic metals into the water (Pb, Hg, and Cu)

• Low water pH and heavy metal contamination reduces the populations of aquatic invertebrates (base of the food chain)

• http://ca.pbslearningmedia.org/resource/envh10.sci.life.eco.toxicmines/contaminating-the-rockies/

Yellow boy – acid mine drainage that returns to a pH of 3 and above causes the formation of Iron(III) hydroxide precipitate

Chokes aquatic life and blocks sunlight

AMD Treatment• Lime neutralization – lime/limestone (CaCO3) is

added to the AMD to neutralize the acidic runoff• Constructed Wetlands – wetlands constructed

with limestone to treat AMD

http://www.ket.org/education/video/watersolutions/acmdremediation.htm

Processing

Smelting• Separates metal from other elements

in ore using high temperatures• Leads to air pollution and acid rain– SO2 and particulates which may

contain a range of heavy metals and acidity

• http://www.hippocampus.org/AP%20Environmental%20Science “Ore Processing”

Heap-Leach Extraction• Ore is broken into small pieces

and put in a pile called a heap• A leaching solution such as

cyanide (gold) or sulfuric acid (copper) is added to pull minerals out

• Leads to water pollution and cyanide releases

• Cyanide is extremely toxic to both humans and wildlife

• Sulfuric acid reduces pH

Issues in Mining: Economics

The situation• Mineral prices are low because the government subsidizes

mining and provides tax breaks to companies that provide US jobs– Mining companies are generally not responsible for full

repair of environmental degradation– Some operations are granted exemptions from

environmental laws (CWA and CAA)– Mining companies can use federal lands at a very low

cost for resource development (Mining Law of 1872)

ViewpointsEnvironmentalists

Increase prices with taxes:• Provide government revenue

for clean-up of old sites and to account for loss of resources

• Create Incentives for efficient energy use

• Promote pollution prevention in the mining process

• Encourage recycling and reuse

Mining InterestsKeep subsidies & low taxes to • Keep mineral prices low to

support economic development and innovation

• Encourage companies to keep mining operations in the US

- other countries have less strict regulations and cheaper labor- mining provides important jobs and revenue for the US

Mining Methods

Open Pit Mining• Removing minerals by

digging them out of the earth's surface and leaving an open pit

• Overburden is dumped back into the pit to restore the land post mining

• Gold, coal, diamonds, marble, gravel, sand, etc

Dredging• Buckets scrape underwater minerals– Also performed to clear sediment

from harbors, ports and behind dams

• Disturbs benthic habitats• Releases heavy metals and other

contaminants into the water (re-enter food chain)

•Increases turbidity – (the cloudiness of the water) cloudy water absorbs more heat, chokes fish and blocks sunlight for photosynthesis

Area Strip Mining• Used where land is flat– Remove overburden layer– Remove mineral– Replace overburden

• Wavy uneven ground called Spoil banks form without remediation increases erosion, hard to re-vegetate (no topsoil)

• Coal or tar sands

Contour Strip Mining• Hilly or mountainous

terrain only• Cut terraces following the

topography• Leaves a highwall without

restoration– Increases erosion– Fragments habitat

• Coal and tar sands

Mountain top Removal• Blast the top off a mountain to retrieve

minerals• Coal Mining• Environmental impacts:

– Explosion: air pollution, noise pollution, earthquakes.

– In general: Loss of mountain habitat, topography changes and loss of vegetation. Difficult to remediate due to poor soil conditions in mountainous areas.

• Pros– Safer for miners and you get more coal

1987

2011http://eros.usgs.gov/#/About_Us/Views_of_the_News

Underground Coal Mine• Mine shafts and tunnels• Very dangerous• Requires less land, produces less

mineral• Dangers: – Mine Collapse– Black lung disease– Ventilation problems leading to

gas buildups• CO/CO2 = suffocation• Methane/hydrogen

sulfide/Coal dust = explosion• Pros – less habitat destruction

Long Wall Room and Pillar