Unit 8

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”)– 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

• 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– 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– 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 – 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– 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• 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

• 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• 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

Soil Conservation

• 1985 Farm Act – strategy to reduce soil erosion in the US

• Reduce erosion & restore fertile land– 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 – planting a row of trees or shrubs on perimeters

– 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