Download ENVIRONMENTAL SCIENCE

Chapter 12
Environmental Geology,
Processes, Minerals & Soils
Geology
• Geology is the study of the Earth’s dynamic
process with respect to it’s interior and
surface structure and features. Rocks,
minerals, chemicals, earthquakes, and
volcanoes are studied to reveal information
about our planet.
• Review the handout from Chapter 6 on the
geosphere.
Geosphere
• Core – central, innermost part of the Earth with a
solid part surrounded by hot, liquid molten
material
• Mantle – thick solid region that surrounds the core
and has zones of molten rock that flows
(asthenosphere)
• Crust – thin, outermost region of the geosphere
**Note that the lithosphere is composed of the upper
mantle and the crust!
Plate Tectonics
• Tectonic plates – constant movement of the rigid
plates due to heat (energy) flow of materials
• Plate tectonics is the theory that explains the
movement of the plates and the processes that
occur at their boundaries
• Plate motion has produced mountains, ocean
ridges, trenches and other features
– Plate movement provides many minerals we use as
resources
– Continental drift helps to explain migration and
evolutionary patterns
Global Geological Information
• Internal process that occur under the Earth’s
surface
• See figure 12-3 (a) for a map of earthquakes
and volcanoes along bands on the earth
• See figure 12-3 (b) for a map of plate
boundaries
Plate Boundaries
• Divergent plate boundaries – plates move in
opposite directions
• Convergent plate boundaries – plates move
toward each other
• Transform faults – plates that slide past
each other
Erosion & Weathering
• External process that happen on the Earth’s
surface
• Erosion is the process where matter is dissolved,
loosened or worn away from one place to another
(ex. streams)
• Weathering is the mechanical or chemical process
that provides change to the surface matter
– Mechanical – physical changes (ex. frost wedging)
– Chemical – decompose by reaction (ex. acid rain)
Rocks
• Minerals – elements & inorganic compounds that
occur naturally (ex. gold)
• Rocks – large continuous part of the earths crust &
many consist of 2 or more minerals
• Rock types – 3 broad classifications are:
– Igneous – formed from molten rock (ex. lava)
– Sedimentary – impaction of sediment (ex. shale)
– Metamorphic – rock that has been subjected to high
temperature, high pressure, chemical activity or a
combination of these (ex. marble)
Rock Cycle
• The rock cycle is the interaction of
processes that continuously change rocks
over time
– Recycles materials over millions of years
– Slowest of all Earth’s cycling processes
– Concentrates the Earth’s non-renewable
resources
Mineral Resources
• Non-renewable resources – mineral
resources that take millions to billions of
years to occur
• Ore is mineral resources mined for profit
– Metallic mineral – ex. iron & copper
– Nonmetallic mineral – ex. salt & clay
– Energy resources – ex. coal & oil
USGS Mineral Catagories
• The USGS has 4 classifications for non-renewable
mineral resources
– Identified resources – known location, quantity and
quality
– Undiscovered resources – assumed to exist with
unknown data
– Reserves – identified resource that can be extracted and
sold for a price
– Other reserves – undiscovered and identified resources
that are not classified as reserves
Detection Methods
• Several methods are used to detect minerals
– Aerial photos & satellite images - outcrops
– Radiation-measuring equipment – detect deposits
– Magnetometer – record changes in the Earth’s magnetic
field
– Gravimeter – measures differences in gravity due to
density differences in various ore deposits
– Underground methods – deep well drilling & core
samples
– Seismic surveys – analyzing shock waves by detonation
– Chemical analysis – leaching into water & plants
Mining
• Surface mining – equipment strips away the
surrounding and unwanted material called the
overburden (as waste it is called “spoil”)
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open-pit mining – equipment digs a hole & extracts ore
Dredging – draglines scrape up underwater minerals
Area strip mining – terrain flattened prior to digging
Contour mining – cuts terraces into the terrain
Mountain-top removal – explosives & powerful shovels
expose ore
• Sub-surface mining – deep vertical shafts,
explosives, heavy equipment used for extraction
Environmental Impacts of Mining
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Scarring & disruption of terrain
Collapse of land above mines
Toxin laced mining waste & air pollution
Acid mine drainage
Overall effects on the health of humans and
wildlife can be devastating
Mineral Supply
• Economic depletion – cost is more to find and
process than its worth on the open market
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Recycle or reuse
Waste less
Use less
Find a substitute
Do without
• Depletion time = depletion /time
• “Should we continue to mine?”
General Mining Law of 1872
• $500 payment & $100/20acres
• Management of timber & minerals
– Opens land for mineral development
– Sell off mineral rich public land
– Turn management over to state & local
governments
Mining Lower Grade Materials
• Achieved with current technologies
• Can be limited by
– Increase cost of mining large quantities of ore
– Availability of fresh water
– Environmental impact of increased waste &
pollution
– Environmental impact of disrupting the
ecosystem surrounding the mine
Microbes in Mining
• Bio-mining or in-situ mining is done by
inoculating an ore vein with microbes that act on a
specific ore
• Microbe loosens the ore and provides a means to
extract it by flooding the mine
• Flood water is filtered for the desired ore and
recycled back to the mine
• Ex. Copper ore is digested by thiobaccillus
ferroxidans
• Bio-mining is a slow process
Natural Hazards
• An ecosystem can be disrupted by natural hazards
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Volcanic eruption
Hurricanes
Tornadoes
Earthquakes
Floods
• Do the Natural Hazards Lab
• Prepare a poster or Power Point presentation that
compares & contrasts 2 natural hazards
Soil Resources
• Complex mixture of
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Eroded rock
Mineral nutrients
Decayed organic matter
Water
Air
Organisms (decomposers)
• Renewable resource
Mature Soil – Soil Zones
• Soil Profile – cross section view of the
horizontal zones in the soil O * Surface
covered with leaves
– A * Top soil is composed of a porous mixture
of decomposed matter and minerals
– B * Sub-soil composed of rocks and other
inorganic matter
– C * Parent mineral which lies above the
bedrock
Soil Types
• Infiltration – water percolates (seeps) into the
zones of soil
• Leaching – water picks up minerals as it infiltrates
and carries them to lower zones
• Soil types in different locations
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Desert
Grassland
Tropical rainforest
Deciduous forest
Coniferous forest
Soil Permeability & Porosity
• Soil permeability – the rate at which water
infiltrates the soil
• Soil porosity - # of pores/volume of soil
– Loams is best for growing crops & contain
equal parts of
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Clay – holds water
Sand – drains easily
Salt - minerals
Humus – organic matter
Soil pH and Nutrient Concentration
• Acidity (acidic) – pH is between 1-6.5
– If too acidic, neutralize with lime & fertilize
• Neutral – pH is around 7
• Alkalinity (basic) – pH is between 7.5 – 14
– If too basic, add sulfur
• Perform the soil lab
Soil Erosion
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Movement of soil from place to place
Loss of fertile land
Build up of soils on land and in water
Erosion is occurring faster than soil can form
Globally -15% erosion total and 40% of the
agricultural property has eroded
• US - 1/3 of the prime soil in the US has eroded
– USDA states the soil is eroding 16x faster than it forms
– USDA states conservation efforts are working
Desertification
• Desertification is the process of turning fertile
land into desert
– Drought – long periods without precipitation
– Unsustainable human activity – lack of conservation
efforts and respect for our land
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Overgrazing
Deforestation
Surface mining
Erosion
Salination
Soil compaction
Salination
• Salination occurs with a concentration of
salts in the soil
– Irrigation containing salts in the water
– Evaporation and transpiration processes leave
salts behind
– Salts build up to a critical level
Waterlogging
• Waterlogging occurs when there is too
much water remaining on land
– Precipitation & irrigation percolates downward
– Water table (underground water levels) rise
Little Sodus Bay (LSB)
Drumlin on LSB– Lake Ontario
Drumlin Erosion East of LSB
Soil Conservation
• 1985 Farm Act – strategy to reduce soil erosion in
the US
• Reduce erosion & restore fertile land
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Conservation tilling – disturb soil as little as possible
Terracing – reduce erosion on slopes
Contour farming – plant along contours of gentle slopes
Strip cropping – planting alternate strips of crops
Alley cropping – planting between shrubs and trees
Wind breaks
Gully reclamation – fast growing vines and shrubs
Restoring Soils
• Organic material
– Animal – dung, adds nitrogen to the soil and
stimulates bacterial & fungial action
– Green manure – green vegetation tilled into the
soil
– Compost – rich organic matter produced by
bacteria from decomposed organic matter in the
presence of oxygen
Important Nutrients
• Commercial fertilizers contain:
– Nitrogen (N) – important for protein production
in plants
– Potassium (K) - potash – primary agricultural
nutrient for food crops
– Phosphorous (P) – phosphates - essential
nutrient from rocks
Soil Lab