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Geology

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Convergent plates slam together, form largest mountains in the world ... Desert Soil (hot, dry climate) Grassland Soil (semiarid climate) Alkaline, dark, and rich ... – PowerPoint PPT presentation

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Title: Geology


1
Geology
  • Chapter 10

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

14
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

16
Types of rock
  • Igneous
  • Granite, pumice, basalt
  • Sedimentary
  • Shale, sandstone, limestone (coral reef)
  • Metamorphic
  • Slate, marble, quartzite

17
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

19
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

21
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.

22
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
23
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

25
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

26
Water
Water
High permeability
Low permeability
Sandy soil
Clay soil
27
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)

28
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
29
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
30
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!)

31
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

32
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

33
Fig. 10.21, p. 228
Desertification of arid and semiarid lands
34
Areas of serious concern
Areas of some concern
Stable or nonvegetative areas
Global soil erosion
Fig. 10.19, p. 226
35
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

38
Evaporation
Transpiration
Evaporation
Evaporation
Waterlogging
Less permeable clay layer
Fig. 10.22, p. 229
39
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

40
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

41
Control planting and strip cropping
Fig. 10.24b, p. 230
42
Alley cropping
Fig. 10.24c, p. 230
43
Fig. 10.24a, p. 230
Terracing
44
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

45
Windbreaks
Fig. 10.24d, p. 230
46
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

47
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

48
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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