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Geology: Processes, Hazards, and Soils

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Title: Geology: Processes, Hazards, and Soils


1
Geology Processes, Hazards, and Soils
Chapter 10 G. Tyler Millers Living in the
Environment 13th Edition
2
Key Concepts
  • Internal geologic processes
  • External geologic processes
  • Minerals, rocks, and the rock cycle
  • Earthquakes and volcanoes
  • Soil structure and formation
  • Soil conservation

3
Geologic Processes
Earths internal structure
Fig. 10-2 p. 204
4
Eight Most Common Chemical Elements ()
WHOLE EARTH WHOLE EARTH CRUST CRUST
Iron 33.3 Oxygen 45.2
Oxygen 29.8 Silicon 27.2
Silicon 15.6 Aluminum 8.2
Magnesium 13.9 Iron 5.8
Nickel 2.0 Calcium 5.1
Calcium 1.8 Magnesium 2.8
Aluminum 1.5 Sodium 2.3
Sodium 0.2 Potassium 1.7
5
Features of the Crust
6
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)
7
Internal Earth Processes
  • Geological changes originating from the earths
    interior
  • Residual heat from the earths core
  • Radioactive decay in the earths crust
  • Convection cells
  • Mantle plumes

8
Spreading center
Oceanic tectonic plate
Oceanic tectonic plate
Ocean trench
Collision between two continents
Plate movement
Plate movement
Tectonic plate
Oceanic crust
Oceanic crust
Subduction zone
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
Mantle
Two plates move towards each other. One is
subducted back into the mantle on falling
convection current.
Hot outer core
Inner core
9
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
PHILIPPINE PLATE
ARABIAN PLATE
PACIFIC PLATE
AFRICAN PLATE
COCOS PLATE
Mid- Indian Ocean Ridge
SOUTH AMERICAN PLATE
Transform fault
Carlsberg Ridge
East Pacific Rise
SOMALIAN SUBPLATE
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
10
Plate Tectonics
  • Theory explaining the movement of tectonic plates
    and the processes that occur at their boundaries.
  • more commonly referred to as continental drift

11
Tectonic Plate Boundaries
  • Divergent boundary
  • Convergent boundary
  • Subduction zone
  • Transform fault

12
Divergent Boundary
Lithosphere
Asthenosphere
Oceanic ridge at a divergent plate boundary
13
Trench
Volcanic island arc
Lithosphere
Rising magma
Asthenosphere
Subduction zone
Trench and volcanic island arc at a convergent
plate boundary
Convergent Boundary
14
Fracture zone
Transform fault
Lithosphere
Asthenosphere
Transform fault connecting two divergent plate
boundaries
Transform Faults
15
Ring of Fire
Volcanoes
Earthquakes
16
Natural Hazards Earthquakes
  • Features
  • Shock waves
  • Focus and epicenter
  • Magnitude
  • Richter Scale
  • 1(insignificant) to 9 (great) 10X
  • Aftershocks
  • Primary Effects
  • shaking
  • Secondary Effects
  • Rockslides, fires, and flooding
  • tsunamis

17
Expected Earthquake Damage
Fig. 10-10 p. 211
18
Natural Hazards Volcanic Eruptions
  • Ejecta (rock and ash)
  • Molten lava
  • Gases

19
External Earth Processes
  • Weathering breakdown of solid rock
  • Mechanical (physical) weathering
  • Frost wedging
  • Chemical weathering
  • Oxidation
  • Hydrolysis
  • Erosion process by which earth particles are
    moved from one place and deposited in another
  • Wind
  • Water

20
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
Landforms resulting from external processes
21
Minerals and Rocks
  • Minerals
  • Naturally occurring
  • Crystalline structure
  • Inorganic
  • Solid
  • Rocks solid, cohesive, aggregate of one or more
    crystalline minerals
  • Igneous (granite, lava)
  • Sedimentary (limestone, sandstone)
  • Metamorphic (marble, slate)

22
Rock Cycle
  • Cycle of creation, destruction, and
    metamorphosis.
  • Three major rock classifications
  • Igneous
  • Sedimentary
  • Metamorphic

23
External Processes
Heat, Pressure
Internal Processes
Heat, Pressure
Igneous Rock Granite, Pumice, Basalt
Magma (Molten Rock)
24
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25
Soil
  • Complex mixture of
  • eroded rock
  • mineral nutrients
  • decaying organic matter
  • water
  • air
  • micro-organisms
  • Renewable resource
  • Weathering of rocks
  • Sedimentation
  • Decomposition of organic matter

26
Soils Formation
  • Soil horizons
  • Soil profile

O horizon Leaf litter
A horizon Topsoil
Humus
B horizon Subsoil
C horizon Parent material
27
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)
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)
29
Soil Properties
  • Infiltration
  • Leaching
  • Porosity
  • Permeability

30
Soil Properties
  • Texture
  • Structure

31
Gravel 2-64 mm
Sand 0.05-2 mm
Silt 0.002-0.05 mm
Clay less than 0.002 mm
Soil Texture Triangle
32
Properties of Soils with Different Textures
Texture Nutrient Infiltration Water-Holding Aerati
on Tilth Capacity 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
Refer to Fig. 10-15 p. 215
33
Chemical Properties of Soil
  • pH
  • Fertility
  • 20 minerals needed for plant growth
  • Major Nutrients (N-P-K)
  • Nitrogen
  • Phosphorus
  • Potassium
  • Minor Nutrients
  • Soil Tests

34
Soil Erosion
  • The movement of soil components from one place to
    another by wind and water.
  • Sheet erosion water moves down a slope or
    across a field in a wide flow
  • Rill erosion surface water forms fast-flowing
    rivulets that cut channels in the soil
  • Gully erosion rivulets join together and cut
    channels wider and deeper until they become
    ditches and gullies.

35
Global Soil Erosion
  • flooding
  • sedimentation
  • loss of soil organic matter
  • reduced ability to store water
  • increased use of fertilizer

36
Desertification
Conversion of rangeland, rain-fed cropland, or
irrigated cropland to desert-like land, with a
drop in agricultural productivity of 10 or more.
  • Causes
  • Overgrazing
  • Deforestation
  • Surface mining
  • Erosion
  • Salinization
  • Soil compaction
  • Consequences
  • Worsening drought
  • Famine
  • Economic losses
  • Lower living standards
  • Environmental refugees

37
Soil Degradation
  • Salinization -
  • the accumulation of salt
  • Waterlogging
  • saturation of soil with irrigation water or
    excess precipitation so the water table rises
    close to the surface.

38
Solutions Soil Conservation
  • Conventional-tillage
  • Conservation tillage
  • Cropping methods
  • Windbreaks

39
Conventional tillage
  • Crop cultivation method in which a planting
    surface is made by plowing land, breaking up the
    exposed soil, and then smoothing the surface.

40
Conservation tillage
  • Crop cultivation in which soil is disturbed
    little (mini-mum tillage farming) or not at all
    (no-till farming) to reduce soil erosion, lower
    labor costs, and save energy.

41
Terracing
42
Contour planting and strip cropping
43
Alley cropping
44
Windbreaks
45
Soil Restoration
  • Crop Rotation
  • planting a field with different crops from year
    to year to reduce soil nutrient depletion.

46
Soil Restoration
  • Organic Fertilizers
  • Animal manure
  • Improves soil structure
  • Adds organic nitrogen
  • Stimulates beneficial soil bacteria and fungi
  • Green manure
  • Fresh and growing green vegetation
  • Compost
  • Microorganisms break down organic matter in the
    presence of oxygen

47
Soil Restoration
  • Commercial Inorganic Fertilizers
  • Nitrogen, Phosphorus and Potassium
  • N, P, K
  • Advantages
  • Easily transported, stored, and applied
  • Disadvantages
  • Not adding humus
  • Reducing organic matter content
  • Lowering oxygen content
  • Supply only 2 or 3 of the more than 20 nutrients
    needed
  • Require large amounts
  • Release nitrous oxides
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