APES Chp 10 Power point.ppt

APES Chp 10

GEOLOGIC PROCESSES

• The earth is made up of a core, mantle, and crust and is constantly changing as a result of processes taking place on and below its surface.

• The earth’s interior consists of:

– Core: innermost zone with solid inner core(Fe, Ni) and molten outer core that is extremely hot. (Fe)

– _{Mantle: solid rock with a rigid outer part}

(asthenosphere) that is melted pliable rock.

Internal Earth Processes

• Dependent upon heat & gravity

Theory of Plate Tectonics

• Huge volumes of heated and molten rock

moving around the earth’s interior form

massive solid plates that move extremely

slowly across the earth’s surface.

Fig. 15-3, p. 337 Spreading center Ocean trench Plate movement Subduction zone Oceanic crust Continental

crust Continental crust Material cools

as it reaches the outer mantle Cold dense material falls back through mantle Hot material rising through the mantle Mantle convection cell

Two plates move towards each other. One is subducted back into the mantle on a falling convection current. Mantle Hot outer core Inner core

Plate moveme nt Collision between two continents Tect onic plat e

Oceanic te

Movement of plates produces:

• Mountains, oceanic ridges, etc.

• Volcanoes &

earthquakes likely to be found at plate

Plate Tectonics

•

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Animation: Plate Margins

3 types of plate boundaries

• The extremely slow movements of these plates cause them to grind into one another at

Convergent Boundaries

•

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Divergent Boundaries

•

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Transform Fault

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GEOLOGIC PROCESSES

• The San

External Geologic Processes

• Dependent upon energy from sun & gravity 1. Erosion – material is dissolved, loosened, or

worn away from one part of earth’s surface and deposited somewhere else

caused mainly by water, wind, anthropogenic 2. Weathering

Wearing Down and Building Up

the Earth’s Surface

• Weathering

is an

external

process that

wears the

MINERALS, ROCKS, AND THE

ROCK CYCLE

• The earth’s crust consists of solid

inorganic elements and compounds

called minerals that can sometimes be

used as resources.

Examples:

• Fossil fuels oil, coal

• Metallic minerals Cu, Fe

GEOLOGIC PROCESSES

• Deposits of nonrenewable mineral

resources in the earth’s crust vary in their

abundance and distribution.

• A very slow chemical cycle recycles three

types of rock found in the earth’s crust:

Natural Hazards

• Earthquakes: fracturing of earth’s crust

produces fault, abrupt movement along fault Focus: pt of initial movement

Epicenter: pt on surface above focus

Richter scale – magnitude, amount of energy Seismograph

<4 insignificant - >8 great

Primary effects: shaking, vertical/horizontal displacement of ground

Predicting and Reducing Loss

• Predict through history, strain in rock

• Use lasers to detect slight movement

along faults

• Reducing loss: enforce building codes in

high risk areas

Volcanoes

• Magma reaches earth’s surface

Explosive eruptions

• Mt. St. Helens, Mt. Pinatubo

Ejects soot, ash, gases high into troposphere SO₂ remains in

atmosphere, can be converted to H₂SO₄

Can reflect sun’s energy and cool earth

Year without summer: 1815 Mt. Tambora in Indonesia North Carolina: frost in

Quiet Eruptions( shield cones)

• At divergent boundaries – creates “hot spots”

• Iceland

Benefits of volcanoes

• Weathering of lava produces highly fertile soil

Reducing Hazards

• Better land use planning

• Better prediction through history, bulging of

Soil: Formation and Types

• Complex mixture of eroded rock, minerals, organic matter, water, air, microorganisms • Renewable, but produced slowly

Soil profile

• Space or pores in layers contain water and N₂ and O₂

• Infiltration – precipitation that percolates down through the layers and into spaces

Soil Texture

• Clay – very fine particles • Silt – fine particles

• Sand -medium size particles

• Gravel – coarse to very coarse particles

Porosity

• Measure of average number and spacing of pores

• Need fine particles for water retention and coarse particles for air spaces

Permeability

Loam – equal mixtures of sand, silt, clay, humus – good for crops, holds water but not too tightly for plants to absorb

Sand – good for crops with low water needs – peanuts, strawberries

Acidity/Alkalinity

• Measured by pH

• Influences uptake of soil nutrients

• Too acid – neutralize with lime

SOIL EROSION AND DEGRADATION

• Soil erosion is the movement of soil components,

especially surface litter and topsoil, by wind or water.

• Soil erosion increases through activities such as farming, logging, construction, overgrazing, and off-road vehicles.

Types of Soil Erosion

• Soil erosion lowers soil fertility and can

overload nearby bodies of water with

eroded sediment.

– _{Sheet erosion: surface water or wind peel off}

thin layers of soil.

– _{Rill erosion: fast-flowing little rivulets of}

surface water make small channels.

Global Outlook: Soil Erosion

Global Soil Erosion

• China- eroded soil creates dust plumes- blocks sun, reduces visibility, increases air pollution in Japan, Korea, nw US

US Soil Erosion

• 1/3 of original topsoil has been washed or blown into waterways as a result of over cultivation,

over grazing and deforestation

Case Study: Soil Erosion in the

U.S. – Some Hopeful Signs

• Soil erodes faster than it forms on most

U.S. cropland, but since 1985, has been

cut by about 40%.

Ecological/Economic Effects of Soil Erosion

• Loss of organic matter & plant nutrients • Reduced ability to store water for crops • Increased use of costly fertilizer

• Increased flooding of valleys below eroded mountain slopes

Desertification

• Productive potential of arid/semi-arid land falls by 10%

Desertification: Degrading

Drylands

Reducing Desertification

• Reduce over grazing, deforestation, destructive forms of planting, irrigation, and mining

• Plant trees & grasses that anchor soil, hold

Salinization

and

Waterlogging

• Repeated

irrigation can

reduce crop

yields by

causing salt

buildup in the

soil and

Salinization and Waterlogging of

Soils: A Downside of Irrigation

• Example of high evaporation,

poor drainage, and severe

salinization.

• White alkaline salts have

Cleanup Prevention

Soil Salinization

Solutions

Reduce irrigation

Switch to salt-tolerant crops (such as barley, cotton,

sugarbeet)

Flush soil

(expensive and wastes water)

Stop growing crops for 2–5 years

Soil Conservation

• Conventional tillage – till up soil to make a

planting surface

• In midwest must do in Fall because

winters are too harsh to allow spring

planting

SUSTAINABLE AGRICULTURE

THROUGH SOIL CONSERVATION

• Modern farm machinery can plant crops

without disturbing soil (no-till and minimum

tillage.)

– Conservation-tillage farming:

• Increases crop yield.

• Raises soil carbon content. • Lowers water use.

Disadvantages of conservation tillage

• In some cases may increase pesticide use due to remaining plant stalks that harbor pests and fungal diseases

Other ways to reduce soil erosion

• Terracing, contour planting, strip

cropping, alley cropping, and windbreaks can

• Terracing – used on steep slopes

• Contour farming –

• Strip cropping –

planting strips of row crops and a cover

crop

• Alley Cropping (agroforestry)– several crops are

planted between rows of shrubs or trees

which provide shade, help retain moisture, and can provide

• Windbreaks or shelterbreaks – trees around the cropland that reduce wind erosion, help retain soil moisture, supply wood for fuel, provide

Gully Reclamation

• Restoring severely eroded land by:

Planting fast growing shrubs, vines, trees to stabilize soil

Building small dams at bottoms of gullies to collect silt and fill in channels

Land Classification

Maintaining Fertility: 2 types of fertilizers

• Fertilizers can help restore soil nutrients, but runoff of inorganic fertilizers can cause water pollution.

– _{Organic fertilizers: from plant and animal}

(fresh, manure, or compost) materials.

– _{Commercial inorganic fertilizers: Active}

Organic Fertilizers

• Animal manure

• Pros: improves soil structure, adds organic

nitrogen, stimulates beneficial soil bacT

and fungi

Organic Fertilizers

• Green manure • Crops grown

specifically to add nutrients to the soil • Legumes with

Organic Fertilizers

• Compost

• Humus-like material rich in organic matter and nutrients.

• Produced when

microorganisms break

Organic Fertilizers

• Spores of mushrooms, puffballs

• Crop rotation: rotate nutrient depleting

crops (corn, cotton) with legumes

Inorganic Fertilizers

• Include:

• Nitrogen as NH₄+, NO

3-, urea, potassium,

phosphorus as PO₄

Cons: Inorganic fertilizers

• if used exclusively, then humus not added to soil (reduces organic matter and soil’s ability to hold water); lowers oxygen content of soil; requires much energy for production, transportation,

application; releases N₂O a greenhouse gas,

causes water pollution and cultural eutrophication. • Rainwater seeping through soil with NO₃- can

leach into groundwater increasing [NO₃-] causing