Geology

1
Geology
2
Earths 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

3
35 km (21 mi.) avg., 1,200C
Crust
100 km (60 mi.) 200 km (120 mi.)
Low-velocity zone
Crust
Mantle
Lithosphere
Solid
10 to 65km
2,900km (1,800 mi.) 3,700C
Asthenosphere (depth unknown)
100 km
Outer core (liquid)
200 km
Core
5,200 km (3,100 mi.), 4,300C
Inner core (solid)
Fig. 10.2, p. 212
4
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)

5
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

6
Plate tectonics

• The lithosphere is broken into many large plates
  which move due to convection currents within the
  asthenosphere
• Remember continental drift (Pangaea)

7
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
SOUTH AMERICAN PLATE
Transform fault
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
8
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)

9
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
10
Fracture zone
Transform fault
Lithosphere
Asthenosphere
Transform fault connecting two divergent plate
boundaries
Fig. 10.6c, p. 215
11
Lithosphere
Asthenosphere
Oceanic ridge at a divergent plate boundary
Fig. 10.6a, p. 215
12
Abyssal hills
Folded mountain belt
Abyssal floor
Oceanic ridge
Trench
Abyssal floor
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
13
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

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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
15
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 earths crust

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Types of rock

• Igneous
• Granite, pumice, basalt
• Sedimentary
• Shale, sandstone, limestone (coral reef)
• Metamorphic
• Slate, marble, quartzite

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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
18
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 lt 5, damaging 5-6, destructive 6-7, major
  7-8, great over 8
• Aftershock reduced shaking after original
  movement

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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

20
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

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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.

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Lords and ladies
Oak tree
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
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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

24
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

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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

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Water
Water
High permeability
Low permeability
Sandy soil
Clay soil
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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)

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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
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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
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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!)

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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

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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

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Fig. 10.21, p. 228
Desertification of arid and semiarid lands
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Areas of serious concern
Areas of some concern
Stable or nonvegetative areas
Global soil erosion
Fig. 10.19, p. 226
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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

36
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

37
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

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Evaporation
Transpiration
Evaporation
Evaporation
Waterlogging
Less permeable clay layer
Fig. 10.22, p. 229
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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

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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

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Control planting and strip cropping
Fig. 10.24b, p. 230
42
Alley cropping
Fig. 10.24c, p. 230
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Fig. 10.24a, p. 230
Terracing
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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

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Windbreaks
Fig. 10.24d, p. 230
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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

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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

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See you on the farm!

• Remember without farming we all starve
• But unless we change our farming practice we
  continue to damage our environment