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Learning Objectives
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Meaning of “Environmental Geology”
Scientific Method
Cultural/Environmental Awareness
Environmental Ethics
Environmental Crisis?
Sustainability
Systems; Environmental Unity
Uniformitarianism
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
Environmental Crisis
• Meaning?
– Increasing demands on diminishing resources
– Demands accelerate as the population grows
– Increasing production of wastes
• Factors
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Overpopulation
Urbanization
Industrialization
Low regard for environmental/land ethics
Inadequacy of institutions to cope with environmental
stresses
Fundamental Concepts
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Population Growth
Sustainability
Systems
Limitation of Resources
Uniformitarianism
Hazardous Earth Processes
Geology as a Basic Environmental Science
Obligation to the Future
Eight Fundamental Concepts
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3a
3b
Overpopulation = #1 environmental problem
Environmental objective = sustainability
The earth is (essentially) a closed system with respect to materials
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. It’s resources are limited
5. Today’s 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
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Earth processes that are hazardous to people have always existed
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An understanding of our environment requires an understanding of the earth
sciences (and related disciplines)
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The effects of land use tend to be cumulative. Thus, we have an obligation to
those who follow us.
Systems
• System: Any part of the universe selected for study
• Concept of “systems”
• Earth as “a system” (w/ component systems):
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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., ?
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
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:
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Mountain building/topography/landscape
Erosion
Water cycles
Climate
Relationships between life & environment
Uniformitarianism con’t
• Key concept in interpreting geologic observations,
e.g.,
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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
Chapter Summary
• Environmental Geology = ?
• Consideration of time in geologic sciences
• Cultural basis for environmental degradation (explain)
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Ethical
Economic
Political
Religious
• Environmental problems not confined to any one political or social
system
• Land ethic = ?
• Immediate cause of environmental crisis:
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Overpopulation
Urbanization
Industrialization
(what do these mean; what’s the relationship?)
Chapter Summary con’t
• Environmental “Problems” mean what?
• Solutions to environmental problems require
what?
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– Scientific understanding (of what?)
– Fostering social, economic, and ethical behavior to
allow implementation (Explain)
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
Observations/Correlations:
• Types and spatial distribution of plate boundaries
• Correlation between plate boundaries and volcanoes (+ earthquakes)
Two Types of Crust/Lithosphere:
• Oceanic (O):
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forms 70% of earth’s crust
constitutes sea-floor bedrock; ~30 km thick
made of primary volcanic “basalt”; density=2.7-3.0
Young; No old oceanic crust
• Continental (C):
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Thicker (~100 km)
Composition: Less dense sediment/granite
“floats” on denser mantle material
Older
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– Primary material (from which basalts are derived)
– Underlies crust
Main Types of Plate Boundaries
• Divergent (splitting apart)
• Convergent (colliding)
• Third Type = Transform
(e.g., lateral offset)
Types Plate Motion, Plate Boundaries, and
Examples of Associated Landforms/Features
• Divergent (separating):
O-O
C-C
sea-floor spreading/mid-ocean ridges
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
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.
Hydrologic Cycle
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
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.)
•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.
• Relationship between:
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Atoms
Molecules
Minerals
Rocks
Landforms
Rock Strength: Stess-Strain Relationships
Relationship between Rock
Types and Plate Tectonics
Rock Cycle- Cycle of melting, crystallization, weathering/erosion, transportation,
deposition, sedimentation, deformation ± metamorphism, repeat of crustal materials.
Classification of Igneous Rocks:
By Physical Criteria
Cooling Rate
Rapid
Setting:
- Extrusive, i.e., Volcanic
-Erupted; on the surface or very shallow
Characteristics/Features:
- Crystals: very small or absent
- Rock = Fine-grained or glassy
Further Subdivided By Eruptive Style:
-Explosive (w/ gas, water)
-Non-explosive (Hawiian-type)
Examples:
- Lava
- Ash
Slow
Setting:
- Intrusive (plutonic)
- Deep within the earth
Characteristics/Features:
- Crystals: Large
- Rock = Coarse-grained
Further Subdivided By Depth & Relative Grain-Size:
-Very deep = very slow = very large crystals
-Medium or shallow depth = medium-size crystals
Examples:
- Granite
- Gabbro
Types / Classification of Sedimentary Rocks
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Clastic: Formed from the mechanical and/or chemical
weathering of other rock materials
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Sandstone, shale
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conglomerate
Chemical: Formed as inorganic precipitates (i.e., water saturated
with respect to chemical compounds)
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Limestone (Ca-carbonates (caliche)
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Other salts, e.g., sulfates, hydroxides, halogen salts (e.g., NaCl)
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Silica
Organic: Formed from (and including) organic material such as:
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Fossil materials (typically shells, diatoms, etc.); exoskeletons, or endoskeletons of
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Organic and/or chemical cements (carbonate, silica, phosphates)
aquatic (e.g., marine) organisms
Combinations
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e.g., Clastic or organic sediment with chemical cement
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
Examples
• Limestone:
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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?
Examples con’t
• 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)
Types of Geologic Structures
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Stratification (Layers & Layering)
Folding/Tilting
Faulting
Other Structures
– fractures
– joints
– crosscutting from forceful injections
(dikes/sills)
Significance of Layering/Tilting
• Basic geologic structure
• Planar reference boundaries that define strata
(boundaries between/within rock materials)
• Implications for landforms/topography?
• Potential pathways
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)
Other Structures
• Fractures
• Joints
• Crosscutting material from forceful
injections
– Dikes (cross-cuts layering)
– Sills (parallel to layering)
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
Summary / Review
• Rock type provides various types of information
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Environment/setting in which they were formed
Tectonic implications
Implications for natural hazards
Physical, chemical properties
Etc.
• Geologic Structures:
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Layering, tilting
Folding
Faulting
Other types (fractures, jointing, cross-cutting features)
• Implications/significance of geologic structures
Learning Objectives
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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
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
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:
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Climate
Topography
Parent material
Time/age of soil
Organic processes
Soil Profile
Development
Variables:
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Parent material
Climate
Topography
Time (Soil age / extent
of development)
– Organic activity
Soil Horizons
Climatic
Effects on Soil
Formation
Land Use & Other Soil Problems
• Human activities affect soils by influencing
patterns, amounts, and intensity of:
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Surface-water runoff
Erosion
Sedimentation
Conversion/manipulation of natural areas &
surface water
(see Figures 3.12, 3.13)
Land Use & Other Soil Problems
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Urbanization
Off-Road Vehicles
Soil Pollution
Desertification
Others
Corrective Measures
• Erosion Controls
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Terracing, contour stripping
Vegetation barriers
Water/sediment basins/reservoirs
Characterization & planning
• Pollution abatement
– Treament, e.g., bioremediation
• Others?
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)
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
Natural Processes as Hazards
• Natural hazards = Natural processes
• Types/examples:
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Earthquakes
Rivers & flooding
Mass movement (e.g., landslides, mudslides, avalanches)
Volcanic activity
Coastal hazards
Others:
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Cyclones, tornados, hurricanes
Lightning
Radon
Etc.
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Benefits of Natural Hazardous
• Natural hazards that have benefits:
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Flooding
Landslides
Volcanism
Earthquakes
• Explain
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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)
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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?
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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:
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Storms
Fires
Floods
Drought (hydrologic cycle)
Food supply (fishing to agriculture)
Energy (e.g., demand vs. hydroelectric supply)
etc. (See Text Chart)
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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?
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Learning Objectives:
Rivers & 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
Main Topics
• River Systems/Processes
• Features & Landforms
• Flooding:
– Factors
– Prevention
– Case Studies
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
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
Key Parameters & Relationships
Continuity 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=vxWxD
(At constant slope)
Key Parameters & Relationships
Stream 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
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Balance (equilibrium) between deposition/erosion as
function of D (Q, velocity, etc.)
• Along the longitudinal profile (headwaters vs. downstream)
– Pools
– Riffles
– Bars
Balance (equilibrium) between deposition/erosion as
function of D (Q, v, x-sect. dimensions, etc.)
In response to land-use changes (e.g., dams)
Balance (equilibrium) between deposition/erosion as
function of D (Q, v, x-sect. dimensions, etc.)
Flooding (general)
– Floodplains & features
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
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?
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
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Zoning
Diversion channels/reservoirs
River management (plans to minimize bank erosion, etc.
Flood hazard mapping
• Channelization
Channelization
Engineered modification
of stream channels
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Straightening
Deepening
Widening
Clearing
Lining
Objectives
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Flood control
Drainage
Erosion control
Improved navigation
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
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:
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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)
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)
– >1.0 = stable
– <1.0 = unstable
– Subject to changed conditions (see example; fig. 6.4)
Causes of Landslides
• Real Causes
– Driving Forces > 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
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
Factors/Controls
• Gravity
– Weight (force); downslope component of the weight of
the slope materials above the slip plane
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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)
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
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)
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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
Role of Climate & Vegetation
• Controls nature/extent of ppt., moisture content
• Vegetation effects (dependent on plant type)
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Enhances infiltration/retards erosion
Enhanced cohesion
Adds weight to slope
Transpiration reduces soil moisture
Minimizing Landslide Hazards
• Identification of potential landslides
• Prevention of Landslides
– Drainage controls
– Grading
– Slope supports
• Warning systems
• Landslide correction
Causes of Landslides
• Real Causes
– Driving Forces > 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
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
Types of Subsidence
• Subsidence at or near the surface: (Volume
losses)
• Withdrawal of fluids
• Underground Mining
• Dissolution of limestone or salt deposits
Subsidence at or near the surface:
(Volume losses)
• Above compressible (fine-grained)
sediments
• Associated with clayey soils
• Draining or decomposition of organic
deposits
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
Earthquake Processes
• Faults and Fault Movement
• Relationship to plate tectonics
– Geographic distribution
– Relationship to plate boundaries
• Shallow earthquakes
• Deep earthquakes
Types of Plate Boundaries & Seismicity
• Divergent-Margin Earthquakes
• Convergent-Margin Earthquakes
• Transform-Margin Earthquakes
• Intraplate Earthquakes
– Basin and Range; Mid-Continent
Seismic Waves and Ground Shaking
• Focus: Point/area where rupture starts
• Epicenter: point on earth’s 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
Seismic Waves
Waves=Forms 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
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 earth’s gravity; 9.8 m/sec2= 1g
– e.g., M =6.0-6.9 quake  0.3-0.9 g
lastic
ebound
Model
Elastic Rebound
Dilatancy-Diffusion
Model/Fault Valve
Mechanism
Earthquakes Caused by Human
Activity
• Reservoir-induced seismicity
• Deep waste disposal
• Nuclear explosions
Effects of earthquakes
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Ground shaking and rupture
Liquifaction
Landslides
Fires
Tsunamis
Regional changes in land elevation
Earthquake Damage
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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
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
Response/Prediction Options
Response to Earthquake Hazards
• Earthquake hazard-reduction programs
• Earthquakes and critical facilities
• Societal adjustments to earthquakes
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structural protection
land-use planning
increased insurance and relief measures
earthquake warning systems
perception of earthquake hazard
My Objectives
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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
Volcanism Correlations
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
Classification by magma type
• Two main end-member types:
1.Basaltic (equivalent of gabbro)
2.Rhyolitic (equivalent of granite)
– Other types
– Intermediate between basaltic and rhyolitic (andesitic)
– Exotic (alkaline)
Volcanic Products
• http://www.geology.sdsu.edu
/how_volcanoes_work/Hom
e.html
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.html
Volcanic Products
• http://www.geology.sdsu.edu
/how_volcanoes_work/Hom
e.html
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_wo
rk/Home.html
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.html
Case Histories
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Nevado del Ruiz
Mt. St. Helens
Long Valley Caldera
Mt. Pinatubo
Mt. Unzen, Japan