Environmental Geology

DYNAMIC PLANET

A Layered Sphere 3 major concentric

zones

Crust, Mantle, & Core

CRUSTCRUST = 1) continental crust & 2) oceanic crust (8

elements make up ~99% of the earth’s crust

MANTLEMANTLE = largest zone; solid; rich in iron (abundant)

CORECORE = inner core (solid) & outer core (liquid); made

mostly of iron

INTERNAL & EXTERNAL EARTH PROCESSESGeologic changes originating from the earth’s

interior are called internal processes – that build the earth’s surface

Two main types of movement occur in the asthenosphere:

1) Convection cells – large volumes of heated rock

moving in a pattern

2) Mantle plumes – rock flows upward as if in a column and

then radiates outward

Tectonic Processes

Plates (100km thick) are composed of the crust and (100km thick) are composed of the crust and the outermost part of the mantle (top of the the outermost part of the mantle (top of the

asthenosphere) known as the ) known as the lithosphere. Plates move approximately 2-15cm/year.

Tectonic Processes

Spreading Subduction Lateral Sliding

Constructive (sea floor spreading)

Destructive (subduction zones)

Conservative

Ridges/Rifts Trenches No major impact

Yes Yes No

Ridges/Rifts VolcanoesTrench

Earthquakes

GEOLOGIC HAZARDS

Earthquakes - Sudden movements of the earth’s crust that occur along faults where one rock mass slides past another. (Transform Fault Boundary)

Gradual movement - creep.• When friction prevents creep, stress builds up until

eventually released with a sudden jerk. Frequently occur along subduction zones Tsunami - Seismic sea swells.

Volcanoes

Volcanoes and undersea magma vents are the sources of most of the earth’s crust.

Many of world’s fertile soils are weathered volcanic material.

• Human / Environmental Dangers

Volcanic AshMudslidesSulfur Emissions

HAWIIAN VOLCANO SYSTEM

MT. ST. HELENS

Pangea

Geologists suggest that several times in earth’s history most, or all, of the continents gathered to form a single super-continent, Pangea, surrounded by a single global ocean.

Fig. 15-4a, p. 338

EURASIAN PLATEEURASIAN PLATENORTH NORTH

AMERICAN AMERICAN PLATEPLATE

ANATOLIAN ANATOLIAN PLATEPLATE

JUAN DE JUAN DE FUCA PLATEFUCA PLATE

CHINA CHINA SUBPLATESUBPLATE

CARIBBEAN CARIBBEAN PLATEPLATE

PHILIPPINPHILIPPINE PLATEE PLATE

ARABIAN ARABIAN PLATEPLATEAFRICAAFRICA

N PLATEN PLATEPACIFIPACIFI

C C PLATEPLATE

SOUTH SOUTH AMERICAN AMERICAN

PLATEPLATENAZCNAZCA A

PLATEPLATE

INDIA-INDIA-AUSTRALIAAUSTRALIA

N PLATEN PLATE

SOMALIASOMALIAN N

SUBPLATESUBPLATE

ANTARCTIC PLATEANTARCTIC PLATE

Divergent plate boundaries

Convergent plate boundaries

Transform faults

Plate Activity….helps?

Recycle: Rock Cycle

Primary and Secondary Successsion

Minerals-distribution and creation

Divergent Evolution

ROCKS AND MINERALS

A mineral is a naturally occurring, inorganic, solid element or compound with a definite chemical composition and regular internal crystal structure.A rock is a solid, cohesive, aggregate of one or more minerals.

Each rock has a characteristic mixture of minerals, grain sizes, and ways in which the grains are held together.

Minerals

Most nonrenewable

Single Elements (Au, Ag, C) Compounds (SiO2, NaCl)

Fossil Fuels-Coal, oil, natural gas

Metallic minerals

Nonmetallic- (sand/quartz)

Identified

Undiscovered Nanotech pg 335

Reserves

Uneven distribution

Rock Types

Rock Cycle - Cycle of creation, destruction, and metamorphosis.

Three major rock classifications:• Igneous

• Sedimentary

• Metamorphic

Fig. 15-8, p. 343

Erosion

Transportation

Weathering

Deposition

Igneous rock Granite,

pumice, basaltSedimentary

rock Sandstone, limestone

Heat, pressure

Cooling

Heat, pressure, stress

Magma (molten rock)

Melting

Metamorphic rock Slate, marble,

gneiss, quartzite

Weathering

Mechanical - Physical break-up of rocks into smaller particles without a change in chemical composition.

Chemical - Selective removal or alteration of specific components that leads to weakening and disintegration of rock.

Oxidation

Sedimentation - Deposition of loosened material.

Fig. 15-6, p. 340

Parent material (rock)

Biological weathering (tree

roots and lichens)

Chemical weathering

(water, acids, and gases)

Physical weathering (wind, rain, thermal

expansion and contraction, water

freezing)

Particles of parent material

Sedimentary Rock

Deposited materials that remain in place long enough, or are covered with enough material for compaction, may again become rock.

Formed from crystals that precipitate out of, or grow from, a solution.• Shale• Dolomite• Sandstone• Limestone (calcium carbonate)

Metamorphic Rock

Pre-existing rocks modified by heat, pressure, and chemical agents.

Chemical reactions can alter both the composition and structure of rocks as they are metamorphosed.• Marble (from limestone)• Quartzite (from sandstone)• Slate (from mudstone and shale)

Igneous Rocks

Most common type of rock in earth’s crust.Solidified from magma extruded onto the surface from volcanic vents.

• Quick cooling of magma produces fine-grained rocks.

Basalt• Slow cooling of magma produces coarse-grained

rocks.

Granite

Mining

1.) Surface Mining: 90% nonfuel, 60% coal

-open pit

-strip mining: contour/mountian top removal-Clean Water Act

Surface Mining Control and

Reclamation Act 1977

2.)Subsurface Mining

Higher grade orelower grade

Subsidence

¾ of solid wastes=MINING

Fig. 15-13, p. 346

Undisturbed land

Overburden

Highwall Coal seam Overburden Pit

Bench

Coal seam

Spoil banks

Fig. 15-9, p. 344

Surface mining

Metal ore Separation of ore from

gangue

Smelting Melting metal

Conversion to product

Discarding of product

(scattered in environment)

Recycling

Fig. 15-10, p. 344

Natural Capital Degradation

Extracting, Processing, and Using Nonrenewable Mineral and Energy Resources

StepsSteps Environmental effectsEnvironmental effects

Mining Disturbed land; mining accidents; health hazards,

mine waste dumping, oil spills and blowouts; noise; ugliness;

heat

Exploration, extraction

Processing

Solid wastes; radioactive material; air, water, and soil pollution; noise; safety and health hazards; ugliness;

heat

Transportation, purification,

manufacturing

Use

Noise; ugliness; thermal water pollution; pollution of

air, water, and soil; solid and radioactive wastes;

safety and health hazards; heat

Transportation or transmission to individual user,

eventual use, and discarding

Fig. 15-16, p. 348

A Mine, use, throw away; no new discoveries; rising

prices

Recycle; increase reserves by improved mining technology,

higher prices, and new discoveriesB

Pro

duct

ion

Recycle, reuse, reduce consumption; increase reserves by improved

mining technology, higher prices, and new

discoveriesC

Present Depletion time A

Depletion time B

Depletion time C

Time

Getting More Minerals from the Ocean

Hydrothermal deposits form when mineral-rich superheated water shoots out of vents in solidified magma on the ocean floor.

Figure 15-17Figure 15-17

Fig. 15-18, p. 351

Solutions

Sustainable Use of Nonrenewable Minerals

• Do not waste mineral resources.

• Recycle and reuse 60–80% of mineral resources.

• Include the harmful environmental costs of mining and processing minerals in the prices of items (full-

cost pricing).

• Reduce subsidies for mining mineral resources.

• Increase subsidies for recycling, reuse, and finding less environmentally harmful substitutes.

• Redesign manufacturing processes to use less mineral resources and to produce less pollution and waste.

• Have the mineral-based wastes of one manufacturing process become the raw materials for other processes.

• Sell services instead of things.

• Slow population growth.

SOIL LAYERSSoil is formed by the weathering of rocksweathering of rocks,

deposition of sedimentsediment by erosion, and decompositiondecomposition of organic material by

microorganisms

Leaf litter layer – leaves, animal waste, insects & decomposers; typically dark brown or black in

color (organic content)Topsoil – humus (decomposed

organic matter; porous; inorganic minerals; root systems; insects &

decomposersSubsoil – inorganic matter;

broken down rock mixture of sand, silt, clay, and gravel

Parent material – baseline beginning of the bedrock that lies

below

Simplified Soil Food Web

Water Water

High permeability Low permeability

Fig. 10.17, p. 224

100%clay100%clay

IncreasingIncreasingpercentage siltpercentage silt

IncreasingIncreasingpercentage claypercentage clay

00

2020

4040

6060

8080

8080

6060

4040

2020

00100%sand100%sand 8080 6060 4040 2020 100%silt100%silt

Increasing percentage sandIncreasing percentage sand

Infiltration – downward movement of water through

soil (percolation)

Leaching – as water seeps down it dissolves soil

components (nutrients) in upper layers & carries it to

lower layersSoil texture determines porosity and permeability

Loam – roughly equal mixtures of

clay, sand, silt, and humus (best soil for growing most

crops)

Texture Nutrient Infiltration Water-Holding Aeration TilthCapacity Capacity

Clay Good Poor Good Poor Poor

Silt Medium Medium Medium Medium Medium

Sand Poor Good Poor Good Good

Loam Medium Medium Medium Medium Medium

PROPERTIES OF SOILS

pH of the soil impacts the ability of nutrients by plantsIf soil is too acidic lime is sometimes but it accelerates decomposition of

organic matter so more organic fertilizer will also be used to maintain fertility

In arid regions that have alkaline soils sulfur may be added which will slowly be converted to sulfuric acid by bacteria