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Geology . Earth’s Structure. Name the zones of the earth Crust, mantle, core Now do it again with more detail Crust, lithosphere, asthenosphere, mantle, outer core, inner core. 35 km (21 mi.) avg., 1,200˚C. Crust. 100 km (60 mi.) 200 km (120 mi.). Low-velocity zone. Crust. Mantle.

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Earth s structure
Earth’s Structure

  • Name the zones of the earth

    • Crust, mantle, core

  • Now do it again with more detail

    • Crust, lithosphere, asthenosphere, mantle, outer core, inner core


35 km (21 mi.) avg., 1,200˚C

Crust

100 km (60 mi.)

200 km (120 mi.)

Low-velocity zone

Crust

Mantle

Lithosphere

Solid

10 to 65km

2,900km

(1,800 mi.)

3,700˚C

Asthenosphere

(depth unknown)

100 km

Outer core

(liquid)

200 km

Core

5,200 km (3,100 mi.), 4,300˚C

Inner

core

(solid)

Fig. 10.2, p. 212


What is in each zone
What is in each zone

  • Core – mostly iron and a little nickel, inner solid and outer is liquid

  • Mantle – mostly iron, silicon, oxygen, and magnesium, mostly rigid except near surface which is plastic (asthenosphere)

  • Crust – mostly oxygen, silicon, aluminum, and iron (by weight)


Convection below
Convection below

  • Heat from the formation of the earth combined with energy from radioactive decay gives way to convection currents of rock (very slow) or mantle plumes in which hot rock rises


Plate tectonics
Plate tectonics

  • The lithosphere is broken into many large plates which move due to convection currents within the asthenosphere

  • Remember continental drift (Pangaea)


Divergent ( ) and

transform fault ( )

boundaries

Reykjanes

Ridge

EURASIAN

PLATE

EURASIAN PLATE

Mid-

Atlantic

Ocean

Ridge

ANATOLIAN

PLATE

JUAN DE

FUCA PLATE

NORTH

AMERICAN

PLATE

CARIBBEAN

PLATE

CHINA

SUBPLATE

Transform

fault

ARABIAN

PLATE

PHILIPINE

PLATE

PACIFIC

PLATE

AFRICAN

PLATE

COCOS

PLATE

Mid-

Indian

Ocean

Ridge

Transform

fault

SOUTH

AMERICAN

PLATE

Carlsberg

Ridge

East Pacific

Rise

AFRICAN

PLATE

INDIAN-AUSTRLIAN PLATE

Southeast Indian

Ocean Ridge

Transform

fault

Southwest Indian

Ocean Ridge

ANTARCTIC PLATE

Plate motion

at convergent

plate boundaries

Plate motion

at divergent

plate boundaries

Convergent

plate boundaries

Fig. 10.5b, p. 214


Plate boundaries
Plate boundaries

  • Divergent – plates move apart, form mid ocean ridges

  • Convergent – plates slam together, form largest mountains in the world

    • Subduction is a type of convergent where one plate dives beneath another and usually creates trenches and volcanoes nearby

  • Transverse – slide sideways past each other (San Andreas Fault)


Trench

Volcanic island arc

Lithosphere

Rising

magma

Asthenosphere

Subduction

zone

Trench and volcanic island arc at a convergent

plate boundary

Fig. 10.6b, p. 215


Fracture zone

Transform

fault

Lithosphere

Asthenosphere

Transform fault connecting two divergent plate boundaries

Fig. 10.6c, p. 215


Lithosphere

Asthenosphere

Oceanic ridge at a divergent plate boundary

Fig. 10.6a, p. 215


Abyssal

hills

Folded mountain belt

Abyssal

floor

Oceanic

ridge

Abyssal

floor

Trench

Craton

Volcanoes

Continental

rise

Oceanic crust

(lithosphere)

Continental

slope

Abyssal plain

Continental

shelf

Abyssal plain

Continental crust

(lithosphere)

Mantle (lithosphere)

Mantle

(lithosphere)

Mantle (asthenosphere)

Fig. 10.3, p. 213


Erosion and weathering
Erosion and Weathering

  • These are the external processes

  • Erosion is the moving of rock material from one place to another (deposition)

  • Weathering is the breaking down of rock by natural forces

    • Ice wedging, rain, wind, gravity

    • Chemical weathering, carbonic acid


Lake

Tidal

flat

Glacier

Spits

Shallow marine

environment

Stream

Barrier

islands

Lagoon

Dunes

Delta

Dunes

Beach

Shallow marine

environment

Volcanic

island

Coral reef

Continental shelf

Continental slope

Abyssal plain

Deep-sea fan

Continental rise

Fig. 10.7, p. 216


Rocks and minerals
Rocks and minerals

  • Mineral – an element or inorganic compound that occurs naturally, is solid, and has a regular crystalline internal structure

  • Rock – type of music meant to be played loud, also any material that makes up a large, natural, continuous part of the earth’s crust


Types of rock
Types of rock

  • Igneous

    • Granite, pumice, basalt

  • Sedimentary

    • Shale, sandstone, limestone (coral reef)

  • Metamorphic

    • Slate, marble, quartzite


Sedimentary Rock

Slate, sandstone,

limestone

Deposition

Transportation

Erosion

Heat,

pressure,

stress

Weathering

EXTERNAL PROCESSES

INTERNAL PROCESSES

Igneous Rock

Granite, pumice,

basalt

Metamorphic Rock

Slate, marble,

quartzite

Heat, pressure

Cooling

Melting

Magma

(molten rock)

Fig. 10.8, p. 217


Earthquake
Earthquake

  • Fault – break in the lithosphere

  • Focus – where the earthquake took place

  • Epicenter – location above focus at surface

  • Richter scale – used to measure magnitude, less than 3 is not felt, logarithmic scale, so each increase of 1 is a factor of 10

  • Minor < 5, damaging 5-6, destructive 6-7, major 7-8, great over 8

  • Aftershock – reduced shaking after original movement


Volcano it can happen here
Volcano – it can happen here!

  • Volcano - Wherever magma reaches the surface through a vent or fissure (also released are gases carbon dioxide, water vapor, hydrogen sulfide, ash, and other ejecta

  • Mt. St. Helens – worst US volcano disaster

  • Ring of fire – other than a song by Social D, this is the edge of the pacific plate where most volcanoes are located


Soil

  • Produced slowly (200-1000 years typically) by weathering of rock, deposition of sediments, and decomposition of organic matter

  • Soil horizons – separate zones within soil

  • Soil profile – cross-section view of soil


Horizons
Horizons

  • O horizon – surface litter

  • A horizon – top soil, made up of inorganic particles (clay, silt, sand) and humus (organic particles from decomposed organisms)

    • Dark topsoil is richer in nutrients

    • Releases water and nutrients slowly

    • Provides aeration to roots

    • Healthy soil contains many nematodes and bacteria, fungi, etc.


Lords and

ladies

Oaktree

Word

sorrel

Dog violet

Organic debris

Builds up

Earthworm

Grasses and

small shrubs

Rock

fragments

Millipede

Mole

Moss and

lichen

Fern

Honey

fungus

O horizon

Leaf litter

A horizon

Topsoil

Bedrock

B horizon

Subsoil

Immature soil

Regolith

Young soil

Pseudoscorpion

C horizon

Parent

material

Mite

Nematode

Actinomycetes

Root system

Red earth

mite

Fungus

Springtail

Mature soil

Bacteria

Fig. 10.12, p. 220


Poor topsoil
Poor topsoil

  • Grey, yellow and red are not the colors of healthy topsoil

  • Generally means that soil is lacking nutrients

  • Best soil is called loam with equal parts sand, silt, clay and humus

  • Leaching – dissolving and carrying nutrients (or pollutants) through soil into lower layers


B horizon and c horizon
B – horizon and C - horizon

  • B – Subsoil mostly broken down rock with little organic matter

  • C- parent material broken down rock on top of the bedrock


Soils
Soils

  • Texture – relative amount of different sized particles present (sand, silt, clay)

  • Porosity – volume of pore space in the soil

  • Permeability – the ability of water to flow through the soil


Water

Water

High permeability

Low permeability

Sandy soil

Clay soil


Soils1
Soils

  • Clay – high porosity, low permeability

  • Sand – high permeability, low porosity

  • Acidity is another factor

  • Where rain is low, calcium and other alkaline compounds may build up (sulfur can be added – turns to sulfuric acid by bacteria)


Forest litter

leaf mold

Acid litter

and humus

Acidic

light-

colored

humus

Humus-mineral

mixture

Light-colored

and acidic

Light, grayish-

brown, silt loam

Iron and

aluminum

compounds

mixed with

clay

Dark brown

Firm clay

Humus and

iron and

aluminum

compounds

Tropical Rain Forest Soil

(humid, tropical climate)

Deciduous Forest Soil

(humid, mild climate)

Coniferous Forest Soil

(humid, cold climate)

Fig. 10.15b, p. 223


Mosaic

of closely

packed

pebbles,

boulders

Alkaline,

dark,

and rich

in humus

Weak humus-

mineral mixture

Dry, brown to

reddish-brown

with variable

accumulations

of clay, calcium

carbonate, and

soluble salts

Clay,

calcium

compounds

Desert Soil

(hot, dry climate)

Grassland Soil

(semiarid climate)

Fig. 10.15a, p. 223


Soil erosion
Soil erosion

  • Causes – mainly water and wind

  • Human induced causes – farming, logging, mining, construction, overgrazing by livestock, off-road vehicles, burning, and more (go us!)


Soil erosion1
Soil erosion

  • Types

  • Sheet

    • Uniform loss of soil, usually when water crosses a flat field

  • Rill

    • Fast flowing water cuts small rivulets in soil

  • Gully

    • Rivulets join to become larger, channel becomes wider and deeper, usually on steeper slopes or where water moves fast


Global soil loss
Global soil loss

  • This is a major problem world wide

  • Have lost about 15% of land for agriculture to soil erosion

    • Overgrazing

    • Deforestation

    • Unsustainable farming

  • Also 40% of ag land is seriously degraded due to soil erosion, salinization, water logging and compaction


Moderate

Severe

Very Severe

Fig. 10.21, p. 228

Desertification of arid and semiarid lands


Areas of serious concern

Areas of some concern

Stable or nonvegetative areas

Global soil erosion

Fig. 10.19, p. 226


Desertification
Desertification

  • Turning productive (fertile) soil into less productive soil (10% loss or more)

    • Overgrazing

    • Deforestation

    • Surface mining

    • Poor irrigation techniques

    • Poor farming techniques

    • Soil compaction


Salinization
Salinization

  • As water flows over the land, salts are leached out

  • When water irrigates a field it is left to evaporate typically

  • This repeated process causes the dissolved salts to accumulate and possibly severely reduce plant productivity

  • Fields must be repeatedly flushed with fresh water to remove salt build up


Waterlogging
Waterlogging

  • When fields are irrigated they allow water to sink into the soil.

  • Winds can dry the surface

  • As more water is applied the root area of plants is over saturated reducing yield

  • As clay is brought to subsoil levels it can act as a boundary for water infiltration


Evaporation

Transpiration

Evaporation

Evaporation

Waterlogging

Less permeable

clay layer

Fig. 10.22, p. 229


Soil conservation
Soil conservation

  • Conservation tillage – (no till farming) disturb the soil as little as possible

  • Reducing erosion also helps – save fuel, cut costs, hold water, avoid compaction, allow more crops to be grown, increase yields, reduce release of carbon dioxide


Soil conservation1
Soil conservation

  • Terracing – making flat growing areas on hillsides

  • Contour farming – planting crops perpendicular to the hill slope, not parallel

  • Strip cropping – planting alternating rows of crops to replace lost soil nutrients (legumes)

  • Alley cropping – planting crops between rows of trees



Alley cropping

Fig. 10.24c, p. 230



Soil conservation2
Soil conservation

  • Gully reclamation – seeding with fast growing native grasses, slows erosion or “reverses” it

    • Also building small dams traps sediments

    • Building channels to divert water or slow water

  • Windbreaks – trees planted around open land to prevent erosion

    • Retains soil moisture (shade, less wind)

    • Habitats for birds, bees, etc.

  • Land classification – identify marginal land that should not be farmed


Windbreaks

Fig. 10.24d, p. 230


Soil fertility
Soil fertility

  • Inorganic fertilizers – easily transported, stored, and applied

    • Do not add humus – less water and air holding ability, leads to compaction

    • Only supply about 3 of 20 needed nutrients

    • Requires large amount of energy for production

    • Releases nitrous oxide (N2O) during production, a green house gas


Soil fertility1
Soil fertility

  • Organic fertilizers – the odor is a problem

  • Animal manure – difficult to collect and transfer easily, hard to store

  • Green manure – compost, aerates soil, improves water retention, recycles nutrients

  • Crop rotation – allows nutrients to return to soil, otherwise same crop continually strips same nutrient, keeps yields high, reduces erosion


See you on the farm
See you on the farm!

  • Remember without farming we all starve

  • But unless we change our farming practice we continue to damage our environment


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