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? Factors
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 Population Growth Sustainability Systems
Limitation of Resources
Uniformitarianism
Hazardous Earth Processes
Geology as a Basic Environmental Science
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. 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
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 con’t
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; what’s the relationship?)

11. Chapter Summary con’t 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 earth’s crust
constitutes sea-floor bedrock; ~30 km thick
made of primary volcanic “basalt”; density=
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. A solid, cohesive aggregate of grains of one or more minerals Mineral:
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

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: Implications for finding them in high mountains?
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 con’t Sandstone Foliated Metamorphic Rocks
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

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)

47. Land Use & Other Soil Problems
Urbanization
Off-Road Vehicles
Soil Pollution
Desertification
Others

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

49. Summary/Overview Definitions of soil Variables (explain)
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 = Probability x Consequence
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 (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 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

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

62. 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 = v x W x D
(At constant slope)

64. 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 •

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 Downstream 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 Objectives
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

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)

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)
>1.0 = stable
<1.0 = unstable
Subject to changed conditions (see example; fig. 6.4)

77. Causes of Landslides Real Causes Immediate causes (triggers)
Driving Forces > Resisting Forces
Immediate causes (triggers)
Earthquake shocks
Vibrations
Sudden increase in water
External Causes
Slope loading
Steepening
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 Slope and topography Water Rock Type
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)

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

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

87. Causes of Landslides Real Causes Immediate causes (triggers)
Driving Forces > Resisting Forces
Immediate causes (triggers)
Earthquake shocks
Vibrations
Sudden increase in water
External Causes
Slope loading
Steepening
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

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

95. 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

96. 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

99. 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 = quake  g

100. Elastic Rebound Model

101. Elastic Rebound

102. Dilatancy-Diffusion Model/Fault Valve Mechanism

103. Earthquakes Caused by Human Activity
Reservoir-induced seismicity
Deep waste disposal
Nuclear explosions

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

105. 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

106. 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

107. Response/Prediction Options

108. 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

109. 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

110. Volcanism Correlations

111. 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

113. 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)

114. Volcanic Products

115. Volcanic Hazards Lava flows Pyroclastic (hot debris) Hazards: Gases
Falls
tephra
ash
pyroclastic (ash) flows
explosive blasts
Gases
Debris & Mud Flows
Others

116. Volcanic Products

117. 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).

118. Volcanic Hazards Lava flows Pyroclastic (hot debris) Hazards: Gases
Falls
tephra
ash
pyroclastic (ash) flows
explosive blasts
Gases
Debris & Mud Flows
Others

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