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Title: Learning Objectives


1
Learning Objectives
  • Meaning of Environmental Geology
  • Scientific Method
  • Cultural/Environmental Awareness
  • Environmental Ethics
  • Environmental Crisis?
  • Sustainability
  • Systems Environmental Unity
  • Uniformitarianism

2
Environmental Ethics
  • What does this mean?
  • Environmental consciousness
  • Existence of relationships between the physical
    environment and civilization
  • Motivation for concept? e.g., The Quiet Crisis
  • Land Ethic Responsibility to the total
    environment as well as society
  • Meaning / scope?
  • Limits?
  • Perspective

3
Environmental Crisis
  • Meaning?
  • Increasing demands on diminishing resources
  • Demands accelerate as the population grows
  • Increasing production of wastes
  • Factors
  • Overpopulation
  • Urbanization
  • Industrialization
  • Low regard for environmental/land ethics
  • Inadequacy of institutions to cope with
    environmental stresses

4
Fundamental Concepts
  1. Population Growth
  2. Sustainability
  3. Systems
  4. Limitation of Resources
  5. Uniformitarianism
  6. Hazardous Earth Processes
  7. Geology as a Basic Environmental Science
  8. Obligation to the Future

5
Eight Fundamental Concepts
  • 1. Overpopulation 1 environmental problem
  • 2. Environmental objective sustainability
  • 3a The earth is (essentially) a closed system
    with respect to materials
  • 3b Solutions to environmental problems require
    understanding of feedback and rates of change in
    systems
  • 4a. The earth is the only sustainable habitat we
    have
  • 4b. Its resources are limited
  • 5. Todays physical processes are modifying our
    landscape (and environment), and have operated
    throughout geologic time but magnitude and
    frequency are subject to natural and man-induced
    changes
  • Earth processes that are hazardous to people have
    always existed
  • An understanding of our environment requires an
    understanding of the earth sciences (and related
    disciplines)
  • The effects of land use tend to be cumulative.
    Thus, we have an obligation to those who follow
    us.

6
Systems
  • System Any part of the universe selected for
    study
  • Concept of systems
  • Earth as a system (w/ component systems)
  • Atmosphere (air)
  • Hydrosphere (water)
  • Lithosphere (rock, soil)
  • Biosphere (life)
  • Interactions of these parts conditions of the
    environment
  • Changes in magnitude or frequency of processes in
    one part causes changes in other parts, e.g., ?

7
System Feedback
  • Negative System adjusts to changed conditions to
    reestablish steady state, e.g., river
  • Positive Changes in a system that cause
    significant modifications of a system, and result
    in amplification of the changes

8
Uniformitarianism
  • The past is the key to the present
  • We can gain understanding of geologic processes,
    systems, etc. in the past by understanding how
    they work today
  • Examples
  • Mountain building/topography/landscape
  • Erosion
  • Water cycles
  • Climate
  • Relationships between life environment

9
Uniformitarianism cont
  • Key concept in interpreting geologic
    observations, e.g.,
  • Glacial processes
  • Marine fossils on mountain tops
  • Volcanism elsewhere in the solar system
  • Ore, petroleum deposits
  • Key for using geologic knowledge to understand
    natural earth processes in historical and
    predictive modes

10
Chapter Summary
  • Environmental Geology ?
  • Consideration of time in geologic sciences
  • Cultural basis for environmental degradation
    (explain)
  • Ethical
  • Economic
  • Political
  • Religious
  • Environmental problems not confined to any one
    political or social system
  • Land ethic ?
  • Immediate cause of environmental crisis
  • Overpopulation
  • Urbanization
  • Industrialization
  • (what do these mean whats the relationship?)

11
Chapter Summary cont
  • Environmental Problems mean what?
  • Solutions to environmental problems require what?
  • Scientific understanding (of what?)
  • Fostering social, economic, and ethical behavior
    to allow implementation (Explain)

12
Earth Materials Processes
  • Focus
  • Geologic materials and processes most important
    to the study of the environment
  • Objectives
  • Acquire a basic understanding of the geologic
    cycle and its subcycles (tectonic, rock,
    hydrologic, biogeochemical)
  • Review of some of the important mineral and rock
    types and their environmental significance
  • Appreciation/significance of geologic structures
  • Appreciation of the landforms, deposits, and
    environmental problems resulting from wind and
    glacial processes

13
  • Observations/Correlations
  • Types and spatial distribution of plate
    boundaries
  • Correlation between plate boundaries and
    volcanoes ( earthquakes)

14
Two Types of Crust/Lithosphere
  • Oceanic (O)
  • forms 70 of earths crust
  • constitutes sea-floor bedrock 30 km thick
  • made of primary volcanic basalt
    density2.7-3.0
  • Young No old oceanic crust
  • Continental (C)
  • Thicker (100 km)
  • Composition Less dense sediment/granite
  • floats on denser mantle material
  • Older
  • Mantle
  • Primary material (from which basalts are derived)
  • Underlies crust

15
Main Types of Plate Boundaries
  • Divergent (splitting apart)
  • Convergent (colliding)
  • Third Type Transform (e.g., lateral offset)

16
Types Plate Motion, Plate Boundaries, and
Examples of Associated Landforms/Features
  • Divergent (separating)
  • O-O sea-floor spreading/mid-ocean ridges
  • C-C Continental rifts Red Sea, Rio Grande
    Mississippi river valleys, E. African (Kenyan)
    Rift Valley
  • Convergent (colliding)
  • O-O Island arc Subduction Japan, Aleutians
  • O-C Continental margin Subduction Cascades,
    Andes
  • C-C Continental collision Himalayas, Alps,
    Appalachians
  • Others Obduction Accreted terrain

17
Other Important Types/Features
  • Hot Spots
  • Hawaiian Islands
  • Yellowstone, Snake River Plain, Columbia River
    Plateau
  • Flood Basalt Provinces (within continents)
  • Columbia River Basalts
  • India, S. Africa, Greenland, Brazil, Germany,
    etc.

18
Hydrologic Cycle
19
Summary
  • Earth is differentiated and dynamic
  • Manifestation of dynamic earth processes in
    lithosphere plate tectonics
  • Two types of crust oceanic continental
  • Centers/Zones where crust is formed (spreading)
    or destroyed (subducted) or accreted define plate
    boundaries
  • Two types of plate boundaries
  • Divergent (splitting/spreading)
  • Convergent

20
Chapter (Section) Objectives
  • Review of some of the important mineral and rock
    types and their environmental significance
  • Relationships between atoms, minerals, rocks,
    rock materials
  • Basic silicate building block(s)
  • Properties of rocks minerals
  • Basic rock types, basis for classification,
  • Why this stuff is important the types of
    information they provide
  • Appreciation/significance of geologic structures
  • Layering
  • Folds
  • Faults
  • Other structures (joints, dikes/sills, etc.)

21
  • Rock
  • A solid, cohesive aggregate of grains of one or
    more minerals
  • Mineral
  • Naturally occurring crystalline inorganic
    substance with a definite chemical composition
    element or compound with a systematic arrangement
    of atoms / molecular structure (e.g., sulfur,
    salt, silicates such as feldspar)
  • Crystallinity
  • Atomic arrangement imparts specific physical and
    chemical properties
  • Physical properties of minerals
  • color, hardness, cleavage, specific gravity,
    streak, etc.

22
  • Relationship between
  • Atoms
  • Molecules
  • Minerals
  • Rocks
  • Landforms

23
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24
Rock Strength Stess-Strain Relationships
25
Relationship between Rock Types and Plate
Tectonics
26
  • Rock Cycle- Cycle of melting, crystallization,
    weathering/erosion, transportation, deposition,
    sedimentation, deformation metamorphism, repeat
    of crustal materials.

27
Classification of Igneous Rocks By Physical
Criteria
28
Types / Classification of Sedimentary Rocks
  • Clastic Formed from the mechanical and/or
    chemical weathering of other rock materials
  • Sandstone, shale
  • conglomerate
  • Chemical Formed as inorganic precipitates (i.e.,
    water saturated with respect to chemical
    compounds)
  • Limestone (Ca-carbonates (caliche)
  • Other salts, e.g., sulfates, hydroxides, halogen
    salts (e.g., NaCl)
  • Silica
  • Organic Formed from (and including) organic
    material such as
  • Fossil materials (typically shells, diatoms,
    etc.) exoskeletons, or endoskeletons of aquatic
    (e.g., marine) organisms
  • Organic and/or chemical cements (carbonate,
    silica, phosphates)
  • Combinations
  • e.g., Clastic or organic sediment with chemical
    cement

29
Significance of Rock Types to Environmental
Geology
  • Type and origin or rock provides insight into
    present or past environmental conditions (e.g.,
    flood deposits, volcanic mudflows)
  • Differences in rock types can have important
    environmental implications (e.g., strata/layers)
  • Physical Properties
  • Strength
  • Planes of weakness
  • Porosity, permeability
  • Chemical Properties
  • Tendancy to dissolve (solubility), leach, or react

30
Examples
  • Limestone
  • Typically formed in a reef or deep marine setting
  • Highly stable in arid climates, unstable in wet
    climates
  • Poor aquifer material
  • Highly conducive to formation of ore deposits
    when adjacent to igneous magams or hydrothermal
    fluids
  • Implications for finding them in high mountains?

31
Examples cont
  • Sandstone
  • Formed as near-shore marine and desert
    environments (w/ noteable differences)
  • Moderate strength
  • Generally porous and permeable
  • Foliated Metamorphic Rocks
  • Implies formation under conditions of directed
    tectonic forces
  • Have potential planes of weakness
  • Others (See charts/figures)

32
Types of Geologic Structures
  • Stratification (Layers Layering)
  • Folding/Tilting
  • Faulting
  • Other Structures
  • fractures
  • joints
  • crosscutting from forceful injections
    (dikes/sills)

33
Significance of Layering/Tilting
  • Basic geologic structure
  • Planar reference boundaries that define strata
    (boundaries between/within rock materials)
  • Implications for landforms/topography?
  • Potential pathways

34
Significance of Fault Folds
  • Areas of broken and/or disrupted crust
  • Usually associated with topographic features
  • Usually results in exposure of different types of
    rock materials at surface
  • Indicative of past and/or present forces
  • Potential for environmental hazard?
  • Often associated with natural resources
    (minerals, petroleum, etc.)
  • Effects on fluid pathways (as preferrential
    pathways or barriers)

35
Other Structures
  • Fractures
  • Joints
  • Crosscutting material from forceful injections
  • Dikes (cross-cuts layering)
  • Sills (parallel to layering)

36
Summary / Review
  • Building blocks of rock materials atoms,
    molecules, minerals, rocks/rock materials
  • Most abundant minerals are silicates
  • Basic building block is the silica tetrahedra
  • Rock properties determined by properties of
    component materials (minerals)
  • Three main classes of rocks
  • Igneous Formed from molten material
  • Sedimentary Clastic, chemical, organic,
    combinations
  • Metamorphic foliated, non-foliated

37
Summary / Review
  • Rock type provides various types of information
  • Environment/setting in which they were formed
  • Tectonic implications
  • Implications for natural hazards
  • Physical, chemical properties
  • Etc.
  • Geologic Structures
  • Layering, tilting
  • Folding
  • Faulting
  • Other types (fractures, jointing, cross-cutting
    features)
  • Implications/significance of geologic structures

38
Learning Objectives
  • Soils terminology processes
  • Interaction of water in soil processes, soil
    fertility
  • Classification of soils (familiarity)
  • Engineering properties of soil
  • Relationships between land use and soils
  • Sediment pollution
  • Desertification

39
Roles of Soils in the Environment
  • Land use planning (suitability)
  • Soil erosion
  • Agriculture
  • Waste management (interactions between waste,
    soil, water)
  • Natural hazards land use planning in terms of
  • Floods
  • Landslides, slope stability
  • Earthquakes

40
Soil Formation
  • Soil formation begins with weathering
  • Weathering Physical and/or chemical breakdown
    of rocks (open system)
  • Physical (mechanical) Processes Big ones to
    little ones
  • Abrasion
  • thermal (expansion/contraction)
  • frost wedging
  • Chemical Processes Dissolution (congruent,
    incongruent w/residue)
  • Soil Formation depends on
  • Climate
  • Topography
  • Parent material
  • Time/age of soil
  • Organic processes

41
Soil Profile Development
  • Variables
  • Parent material
  • Climate
  • Topography
  • Time (Soil age / extent of development)
  • Organic activity

42
Soil Horizons
43
Climatic Effects on Soil Formation
44
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45
Land Use Other Soil Problems
  • Human activities affect soils by influencing
    patterns, amounts, and intensity of
  • Surface-water runoff
  • Erosion
  • Sedimentation
  • Conversion/manipulation of natural areas
    surface water
  • (see Figures 3.12, 3.13)

46
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47
Land Use Other Soil Problems
  • Urbanization
  • Off-Road Vehicles
  • Soil Pollution
  • Desertification
  • Others

48
Corrective Measures
  • Erosion Controls
  • Terracing, contour stripping
  • Vegetation barriers
  • Water/sediment basins/reservoirs
  • Characterization planning
  • Pollution abatement
  • Treament, e.g., bioremediation
  • Others?

49
Summary/Overview
  • Definitions of soil
  • Roles of soils in environmental geology
  • Land use planning
  • Waste disposal
  • Evaluation of natural hazards
  • Formed from rock interactions in the hydrologic
    cycle (explain)
  • Variables (explain)
  • Climate
  • Topography
  • Parent material
  • Time
  • Organic activity
  • Soil processes form distinctive layers (horizons)
  • Soil Properties
  • Color
  • Texture (particle size)
  • Structure (peds)

50
Learning Objectives
  • Conditions that make some natural processes
    hazardous
  • Benefits of hazardous natural processes
  • Types of natural hazards
  • Prediction of natural disasters
  • Perception and adjustments to natural hazards
  • Impact and recovery from natural disasters and
    catastrophes

51
Natural Processes as Hazards
  • Natural hazards Natural processes
  • Types/examples
  • Earthquakes
  • Rivers flooding
  • Mass movement (e.g., landslides, mudslides,
    avalanches)
  • Volcanic activity
  • Coastal hazards
  • Others
  • Cyclones, tornados, hurricanes
  • Lightning
  • Radon
  • Etc.

?
52
Benefits of Natural Hazardous
  • Natural hazards that have benefits
  • Flooding
  • Landslides
  • Volcanism
  • Earthquakes
  • Explain

?
53
Risk Assessment
  • Risk Probability x Consequence
  • E.g., risk of death from smoking cigarettes
  • Consequence Death (could be other effects)
  • Probability Frequency of this consequence in a
    population
  • Must be calculated for various scenarios/events,
    e.g., earthquake of various magnitudes, proximity
    to population centers, structures (nuclear plant,
    dam)

?
54
Acceptable risk
  • There is risk associated with everything
  • There is no such thing as zero risk, only
    different levels of risk
  • e.g., Everyone is exposed to risks everyday
    (e.g., driving, radon)
  • Levels of Acceptable Risk are, therefore,
    established
  • Examples of Acceptable Risk Levels are used in
    toxicology human health risk assessments
  • e.g., Increased acceptable risk from exposure to
    cancer-causing chemicals is typically 10-6 (risk
    of death from natural levels of radon 10-3 )
  • What do these numbers mean?

?
55
Relationship Between Hazards and Climate Changes?
  • System interrelationships or feedback of annual
    weather and/or climate changes?
  • E.g., El Nino, La Nina, others
  • Global warming?
  • Connections between weather/climate and
  • Storms
  • Fires
  • Floods
  • Drought (hydrologic cycle)
  • Food supply (fishing to agriculture)
  • Energy (e.g., demand vs. hydroelectric supply)
  • etc. (See Text Chart)

?
56
Population, Land-Use and Natural Hazards
  • Effects of Population Increase
  • Proximity issues (e.g., quakes, volcanoes,
    floods)
  • Cause effect issues(Mexico City example)
  • Changing Land-Use Effects
  • Disruption of natural system buffers
  • Changed/exacerbated feedback
  • Examples
  • Yangtze River flooding
  • Hurricane in Central America
  • Reasons?

?
57
Learning ObjectivesRivers Flooding
  • Appreciation for river processes
  • Flood hazard
  • Nature extent
  • Upstream vs. downstream flooding
  • Effects of urbanization (in small drainage
    basins)
  • Main preventive adjustment measures
  • Environmental effects of channelization

58
Main Topics
  • River Systems/Processes
  • Features Landforms
  • Flooding
  • Factors
  • Prevention
  • Case Studies

59
Sediments in Rivers
  • Load Quantity of sediment carried in a river
  • Bed load moved along bottom
  • Suspended load carried in suspension
  • Dissolved load in solution

60
Slope Profiles
  • Slope or gradient
  • vertical drop /horizontal distance (e.g.,
    km/km)
  • Gradient angle tan-1 (gradient)
  • e.g., for gradient of 0.01, tan-1 (0.01)0.5o
  • Longitudinal profile
  • Graph of elevation vs. distance downstream

61
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62
Key Parameters RelationshipsContinuity Equation
  • Discharge (m3/sec)
  • Q volume of water passing a point per unit
    time
  • Velocity (m/sec)
  • Cross-sectional area (width x depth) (m2)
  • Q v x W x D
  • (At constant slope)

63
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64
Key Parameters RelationshipsStream Power
Capacity
  • Stream Power (P) ability to transport and/or
    erode sediment
  • P Q x slope x r where r 10-5 kg/m3 units
    of P (kg/sec)
  • P velocity x width x depth x slope x density
  • i.e., - narrower, shallower streams, have higher
    velocities erode
  • - wider, deeper streams, have lower
    velocities deposit
  • - Steeper gradients, higher velocities, erode
    vice-versa
  • Capacity total load that can be carried/time
    (e.g., kg/sec)
  • Competence largest particle (diam.) a river may
    transport

65
Balance (equilibrium) between deposition/erosion
as function of D (Q, velocity, etc.)
  • Along the longitudinal profile (headwaters vs.
    downstream)
  • Pools
  • Riffles
  • Bars

66
Balance (equilibrium) between deposition/erosion
as function of D (Q, v, x-sect. dimensions, etc.)
  • In response to land-use changes (e.g., dams)

67
Balance (equilibrium) between deposition/erosion
as function of D (Q, v, x-sect. dimensions, etc.)
  • Flooding (general)
  • Floodplains features

68
  • Upstream floods
  • Intense rainfall
  • Of short duration
  • Over relatively small area
  • E.g., flash floods
  • Downstream floods
  • Cover a wide area
  • Produced by storms of long duration
  • Saturated soil ? increased runoff
  • Contribution from many tributaries
  • E.g., regional storms, spring runoff

69
Factors That Affect Flooding
  • Rainfall (weather) events
  • Local vs. regional
  • Seasonal
  • 50, 100-year floods
  • Runoff (factors affecting infiltration)
  • Gradient
  • Vegetation
  • Human effects
  • Urbanization (e.g., paving, storm sewers)
  • Others?

70
Flood Damage Prevention/ Control
  • Physical barriers
  • Levees/bank stabilization
  • Dams
  • Retention ponds
  • Floodplain regulation
  • Optimizing floodplains w/ minimal flood damage
  • Balance of natural resource w/ natural hazard
  • Zoning
  • Diversion channels/reservoirs
  • River management (plans to minimize bank erosion,
    etc.
  • Flood hazard mapping
  • Channelization

71
Channelization
  • Engineered modification of stream channels
  • Straightening
  • Deepening
  • Widening
  • Clearing
  • Lining
  • Objectives
  • Flood control
  • Drainage
  • Erosion control
  • Improved navigation

72
Pros Cons of Chanelization
  • Pros (Benefits)
  • Same as objectives where benefits outweigh
    environmental damage/degradation
  • Cons (Adverse Effects)
  • Environmental Degradation
  • Wetland drainage
  • Vegetation elimination/decrease
  • Habitat effects
  • Erosion, siltation
  • River flow pattern effects
  • Aesthetic effects

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74
Learning Objectives
  • Gain a basic understanding of slope stability and
    mechanisms of slope failure
  • Understand the role of driving and resisting
    forces affecting slope stability
  • Understand factors that affect slope processes
  • Topography
  • Climate
  • Vegetation
  • Water
  • Time
  • (Gravity)
  • (rock type)
  • Understand how human use of land affect
    landslides slopes
  • Familiarization with identification, prevention,
    warning, correction of landslides
  • Appreciation for processes related to land
    subsidence (Part B)

75
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76
Slope Stability
  • Relationship between driving resisting forces
  • Driving forces (DF)
  • Weight of rock, soil
  • Weight of superimposed material
  • Vegetation
  • Fill
  • Buildings
  • Resisting forces (RF)
  • Shear-strength of slope material acting along
    potential slip planes
  • Cohesion
  • Internal friction
  • Ratio RF/DF Factor of Safety (FS)
  • gt1.0 stable
  • lt1.0 unstable
  • Subject to changed conditions (see example fig.
    6.4)

77
Causes of Landslides
  • Real Causes
  • Driving Forces gt Resisting Forces
  • Immediate causes (triggers)
  • Earthquake shocks
  • Vibrations
  • Sudden increase in water
  • External Causes
  • Slope loading
  • Steepening
  • Earthquake shocks
  • Internal Causes Causes that reduce shear
    strength

78
Functional Relationships
  • Relationship between downward force (gravity)
    Resistance force (shear stress)
  • Stress force / unit area
  • S shear stress
  • S C (p-u) tanq p total pressure
  • u fluid pressure (pore water
    pressure)
  • tan q coefficient of internal
    friction
  • q angle of internal friction
    (frict. resist.)
  • S C (sn -u) tanq sn normal stress (i.e.,
    normal to surface
  • or plane of discontinuity
  • C cohesion of material

79
Factors/Controls
  • Gravity
  • Weight (force) downslope component of the weight
    of the slope materials above the slip plane
  • Downward
  • Normal to surface or plane of discontinuity (sn)
  • Parallel to surface or plane of discontinuity
  • Angle of repose (slope angle)
  • Slope and topography
  • Water
  • Rock Type
  • Structure
  • Others? (Anthropogenic)

80
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81
Factors Resulting in Decreased Slope Stability
  • Increased pore pressure (affects sn) e.g.,
    Storms, fluctuating groundwater
  • Increased water content (reduces C, q)
  • Steepening of slopes (affects sn)
  • Loading of slopes (affects sn)
  • Earthquake shaking (reduces C, q)
  • Removal of material from the base of slopes
    (Directly reduces S)
  • Rivers, waves, man
  • Changes in vegetation
  • Change in chemical composition of pore water

82
Roles of Rock/Soil Type
  • Patterns of movement
  • Rotational slides (slumps)
  • occur along curved surfaces
  • Produces topographic benches (see fig.)
  • Commonly occur in weak rock types (e.g., shale)
  • Translational slides
  • Planar
  • Occur along inclined slip planes within a slope
    (6.2)
  • Fractures in all rock types
  • Bedding planes in rock slopes
  • Clay partings
  • Foliation planes (metamorphic rocks)
  • Soil Slips
  • Type of translation slide
  • Slip plane above bedrock, below soil
  • Colluvium

83
Role of Climate Vegetation
  • Controls nature/extent of ppt., moisture content
  • Vegetation effects (dependent on plant type)
  • Enhances infiltration/retards erosion
  • Enhanced cohesion
  • Adds weight to slope
  • Transpiration reduces soil moisture

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85
Minimizing Landslide Hazards
  • Identification of potential landslides
  • Prevention of Landslides
  • Drainage controls
  • Grading
  • Slope supports
  • Warning systems
  • Landslide correction

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87
Causes of Landslides
  • Real Causes
  • Driving Forces gt Resisting Forces
  • Immediate causes (triggers)
  • Earthquake shocks
  • Vibrations
  • Sudden increase in water
  • External Causes
  • Slope loading
  • Steepening
  • Earthquake shocks
  • Internal Causes Causes that reduce shear
    strength

88
Subsidence Learning Objectives
  • Understand the types of subsidence and the causes
    of each type
  • Key controls of subsidence processes, and
    mitigation
  • Human effects that promote or mitigate subsidence

89
Types of Subsidence
  • Subsidence at or near the surface (Volume
    losses)
  • Withdrawal of fluids
  • Underground Mining
  • Dissolution of limestone or salt deposits

90
Subsidence at or near the surface (Volume losses)
  • Above compressible (fine-grained) sediments
  • Associated with clayey soils
  • Draining or decomposition of organic deposits

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92
Learning objectives
  • Understand the relationship of earthquakes to
    faulting
  • Familiarization with earthquake wave (energy)
    terminology
  • Understand the concept of earthquake magnitude
    (and its calculation)
  • How seismic risk is estimated
  • Familiarization with the major effects of
    earthquakes
  • The prediction of earthquakes
  • Mitigation of earthquake damage

93
Earthquake Processes
  • Faults and Fault Movement
  • Relationship to plate tectonics
  • Geographic distribution
  • Relationship to plate boundaries
  • Shallow earthquakes
  • Deep earthquakes

94
Types of Plate Boundaries Seismicity
  • Transform-Margin Earthquakes
  • Intraplate Earthquakes
  • Basin and Range Mid-Continent
  • Divergent-Margin Earthquakes
  • Convergent-Margin Earthquakes

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Seismic Waves and Ground Shaking
  • Focus Point/area where rupture starts
  • Epicenter point on earths surface directly
    above the focus
  • Types of seismic waves
  • Body waves waves travel within the earth
  • P- waves Primary compression waves
  • S- waves Shear waves
  • Surface waves
  • L-(Love) waves horizontal ground movement
  • Rayleigh waves rolling motion

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Seismic Waves
  • WavesForms of energy release
  • Motion/propagation types
  • Frequency Number of waves passing a reference
    point/sec
  • Period Number of seconds between successive
    peaks
  • Amplitude Measure of ground motion
  • Attenuation/amplification

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Comparing/Measuring Earthquakes
  • Magnitude
  • Measure of energy released (log scale)
  • measurement scale Richter scale (0-10)
  • Intensity
  • Relative scale based on perceived damage
  • Modified Mercalli Scale (1-12)
  • Ground acceleration during earthquakes
  • Rate of change of horizontal or vertical velocity
    of the ground
  • Normalized/compared to earths gravity 9.8
    m/sec2 1g
  • e.g., M 6.0-6.9 quake ? 0.3-0.9 g

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Elastic Rebound Model
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Elastic Rebound
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Dilatancy-Diffusion Model/Fault Valve Mechanism
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Earthquakes Caused by Human Activity
  • Reservoir-induced seismicity
  • Deep waste disposal
  • Nuclear explosions

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Effects of earthquakes
  • Ground shaking and rupture
  • Liquifaction
  • Landslides
  • Fires
  • Tsunamis
  • Regional changes in land elevation

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Earthquake Damage
  • Buildings Swaying, Pancaking
  • Broken pipelines (gas, water) electrical lines
  • Fires explosions (from pipelines storage
    tanks)
  • Shearing subsidence of sand fills
  • Quicksand, sand boils, sand volcanoes
  • Quickclays
  • Landslides

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Origins of Tsunamis
  • Sudden vertical displacement of seafloor (from
    dip-slip fault)
  • Momentary drop in local sea level
  • Water rushes into depression, but overcorrects,
    locally raising the sea level
  • Sea level locally oscillates before stabilizing
  • Oscillations are transmitted as long, low seismic
    sea waves

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Response/Prediction Options
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Response to Earthquake Hazards
  • Earthquake hazard-reduction programs
  • Earthquakes and critical facilities
  • Societal adjustments to earthquakes
  • structural protection
  • land-use planning
  • increased insurance and relief measures
  • earthquake warning systems
  • perception of earthquake hazard

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My Objectives
  • How are they formed?
  • How do they work?
  • Where do they occur, and why?
  • Main types of volcanic activity, eruptive styles,
    and products
  • Volcanic landforms
  • Volcanic hazards, prediction, mitigation
  • Relationships

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Volcanism Correlations
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Relationships Between Plate Tectonic
Mechanisms,Volcanic Styles Products
  • Basaltic magmas
  • Derived from melting of mantle
  • Ocean-ridge plume eruptions
  • Magmas w/o crustal contamination
  • More Si-rich magmas
  • Involve melting of crust, and/or flux-melting of
    mantle from de-watered subducted crust
  • Subduction-related
  • Mid-continent eruptions w/ crustal contamination

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Classification by magma type
  • Two main end-member types
  • Basaltic (equivalent of gabbro)
  • Rhyolitic (equivalent of granite)
  • Other types
  • Intermediate between basaltic and rhyolitic
    (andesitic)
  • Exotic (alkaline)

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Volcanic Products
  • http//www.geology.sdsu.edu/how_volcanoes_work/Hom
    e.html

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Volcanic Hazards
  • Lava flows
  • Pyroclastic (hot debris) Hazards
  • Falls
  • tephra
  • ash
  • pyroclastic (ash) flows
  • explosive blasts
  • Gases
  • Debris Mud Flows
  • Others
  • http//magic.geol.ucsb.edu/fisher/hazards.htm
  • http//volcanoes.usgs.gov/Hazards/What/hazards.ht
    ml

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Volcanic Products
  • http//www.geology.sdsu.edu/how_volcanoes_work/Hom
    e.html

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Caldera Eruptions
  • When an erupting volcano empties a shallow-level
    magma chamber, the edifice of the volcano may
    collapse into the voided reservoir, thus forming
    a steep, bowl-shaped depression called a caldera
    (Spanish for kettle or cauldron).

http//www.geology.sdsu.edu/how_volcanoes_work/Hom
e.html
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Volcanic Hazards
  • Lava flows
  • Pyroclastic (hot debris) Hazards
  • Falls
  • tephra
  • ash
  • pyroclastic (ash) flows
  • explosive blasts
  • Gases
  • Debris Mud Flows
  • Others
  • http//magic.geol.ucsb.edu/fisher/hazards.htm
  • http//volcanoes.usgs.gov/Hazards/What/hazards.ht
    ml

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Case Histories
  • Nevado del Ruiz
  • Mt. St. Helens
  • Long Valley Caldera
  • Mt. Pinatubo
  • Mt. Unzen, Japan
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