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Chapter 1 Lecture
Natural Hazards
Fourth Edition
Introduction to
Natural Hazards
Tim Frazier
The University of Idaho
© 2015 Pearson Education, Inc.
Learning Objectives
• Explain the difference between a disaster and a
catastrophe.
• Discuss the role of history in the understanding of
natural hazards.
• Discuss the components and processes of the
geologic cycle.
• Apply the scientific method to a natural hazard of
your choice.
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Learning Objectives, cont.
• Synthesize the basics of risk assessment.
• Explain how much of the damage caused by natural
hazards is often related to decisions people make
before, during, and after a hazardous event.
• Explain why the magnitude of a hazardous event is
inversely related to its frequency.
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Learning Objectives, cont.
• Summarize how natural hazards are linked to one
another and to the physical environment.
• Give reasons why increasing population and poor
land-use practices compound the effects of natural
hazards and can turn disasters into catastrophes.
• Explain how events we view as hazards provide
natural service.
• Summarize links between climate change and
natural hazards.
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Earthquake in Haiti, 2010: A Human-Caused
Catastrophe?
• Haiti recognized as an environmental catastrophe
waiting to happen
– What were once disasters are now catastrophes due to
increasing population and poor land-use choices
• Haiti’s population increased dramatically in recent decades
• About 90 percent of country deforested
• Island venerable to hurricanes and other high-intensity
storms as well as earthquakes
• Four hurricanes and tropical storms hit the island
within a month’s time two years before the
earthquake
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Deforestation in Haiti
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Earthquake in Haiti, 2010: A Human-Caused
Catastrophe?
• Earthquake became a catastrophe
– Eighty-five percent of people in Port-au-Prince lived in
slum conditions
– Poor conditions lead to 190,000 destroyed or damaged
• Killed a quarter million people
• Two million homeless with poor sanitation and water quality
• Reason for catastrophe was clear: heavy human
footprint
– Large number of poorly constructed buildings
– Population grew so fast
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Collapsed Buildings in Haiti
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1.1 Why Studying Natural Hazards Is
Important
• Have experienced large, costly, and deadly natural
hazards since 1995
– Deadliest tsunami caused by earthquake in Indian Ocean
– Tsunami in Japan caused by largest and costliest
earthquake in recorded history
– Catastrophic flooding in different areas of the world
– Volcanic eruptions that shut down international airports
– Worst tornado outbreak in U.S. history
– Etc.
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Processes: Internal and External
• Processes
– Physical, chemical, and biological ways in which events
affect Earth’s surface
• Internal processes come from forces within Earth
– Plate tectonics
– Result of internal energy of Earth
• External processes come from forces on Earth’s
surface
– Atmospheric effects
– Energy from the Sun
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Hazard, Disaster, or Catastrophe
• Hazard
– Natural process or event that is a potential threat to human
life or property
• Disaster
– Hazardous event that occurs over a limited time in a
defined area
– Criteria:
1)
2)
3)
4)
Ten or more people killed
100 or more people affected
State of emergency is declared
International assistance is requested
• Catastrophe
– Massive disaster that requires significant amount of money
or time to recover
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Major Hazards in the United States
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Hazard, Disaster, or Catastrophe, cont.
• During past half century, there has been a dramatic
increase in natural disasters (Figure 1.6a):
– Examples: Haitian earthquake, Indonesian tsunami,
Hurricane Katrina
• United Nation: 1990’s “International Decade for
Natural Hazards Reduction”
– Mitigation
• Reduce the effects of something
• Natural disaster preparation
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Numbers, Effects, and Causes of Worldwide
Natural Disasters
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Death and Damage Caused by Natural
Hazards
• Effects of hazards can differ and change with time
because of changes of patterns of human land use
• Natural hazards that cause the greatest loss on
human life may not cause the most property
damage
• Hazards vary greatly in their ability to cause
catastrophe
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Potential for Humans to Influence Selected
Natural Hazards in the United States
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1.2 Role of History in Understanding
Hazards
• Natural hazards are repetitive
• History of an area gives clues to potential hazards
– Maps, historical accounts, climate and weather data
– Rock types, faults, folds, soil composition
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1.3 The Geologic Cycle
• Geologic conditions govern the type, location, and
intensity of natural processes
• Collectively, processes are called geologic cycle
– Subcycles:
•
•
•
•
Tectonic cycle
Rock cycle
Hydrologic cycle
Biogeochemical cycle
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The Tectonic Cycle
• Refers to large-scale processes that deform Earth’s
crust and produce landforms
• Driven by forces within Earth
• Involves the creation, destruction, and movement of
tectonic plates
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The Rock Cycle
• Rocks are aggregates of one or more minerals
• Recycling of earth materials and linked to all other
cycles
– Tectonic cycle: heat and energy
– Biogeochemical cycle: materials
– Hydrologic cycle: water for erosion and weathering
• Rocks classified according to how they were formed
in the rock cycle
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The Rock Cycle, cont.
• Igneous rocks
– Form from crystallization of magma
• Sedimentary rocks
– Rocks are weathered into sediment by wind and water
– Deposited sediment undergoes lithification
• Metamorphic rocks
– Rocks are changed through extreme heat, pressure, or
chemically active fluids
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The Rock Cycle
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The Hydrologic Cycle
• Movement of water between atmosphere and
oceans and continents driven by solar energy
• Processes include: evaporation, precipitation,
surface runoff, and subsurface flow
• Water is stored in compartments such as oceans,
atmosphere, rivers, stream, etc.
– Residence time is estimated average time that a drop of
water spends in any compartment
– Only a small amount of water is active at any given time
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Hydrologic Cycle
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The World’s Water Supply (Selected
Examples)
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Biogeochemical Cycles
• Transfer of chemical elements through a series of
reservoirs
• Related to the three previous cycles
– Tectonic cycle: water from volcanic processes; heat and
energy required
– Rock and hydrological cycles: involved in transfer and
storing of chemical elements
• Rates of transfer of important chemical elements are
only approximate
– Carbon, Nitrogen, Phosphorus
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1.4 Fundamental Concepts for
Understanding Natural Processes as
Hazards
1. Science helps us predict hazards.
2. Knowing hazard risks can help people make
decisions.
3. Linkages exist between natural hazards.
4. Humans can turn disastrous events into
catastrophes.
5. Consequences of hazards can be minimized.
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1. Science Helps Us Predict Hazards: Science
and Natural Hazards
• Science is body of knowledge that has resulted from
investigations and experiments
• Scientific Method
– Formulation of a question
– Hypothesis is a possible answer to a question and is
testable
– Data is taken to test the hypothesis
• Scientific investigation has improved understanding
of natural disasters
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1. Science Helps Us Predict Hazards: Hazards
Are Natural Processes
• They are a result of natural forces
– Become hazardous when people live or work near the
process and land-use changes amplify their effects
• It is possible to control some of these processes to
some degree
– Most are NOT within our control
• Best approach to reduction is to identify the
processes and delineate the geographic areas
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1. Science Helps Us Predict Hazards: Forecast,
Prediction, and Warning of Hazardous Events
• Uniformitarianism
– “The present is the key to the past”
• Human interaction has an effect on geologic
processes
– “The present is the key to the future”
• Environmental Unity
– One action causes others in a chain of actions and events
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1. Science Helps Us Predict Hazards: Forecast,
Prediction, and Warning of Hazardous Events,
cont.
• Prediction
– Specific date, time, and magnitude of event
• Forecast
– Range of probability for event
• Some hazards can be predicted; most can be
forecasted
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1. Science Helps Us Predict Hazards: Forecast,
Prediction, and Warning of Hazardous Events,
cont.
• Identify the location of probable event
– Most hazardous areas can be mapped
– Example: volcanoes and earthquake events are located
• Determine probability of event
– Estimated based on past events and current conditions
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1. Science Helps Us Predict Hazards: Forecast,
Prediction, and Warning, cont.
• Observe precursor events
– Events that precede a hazardous event
– Example: earthquakes often precede volcanic eruptions
• Forecast or predict event
– Forecast gives certainty of event
– Prediction will give an estimated time for events
• Warning the public
– Involves statements to media and public at large
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Hazard Prediction or Warning
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2. Knowing Hazards Risks Can Help People
Make Decisions
• Risk = (probability of event) x (consequences)
• Consequences: damages to people, property,
economics, etc.
• Acceptable Risk is the amount of risk that an
individual or society is willing to take
• Frequent problem is a lack of reliable data for either
the probability or consequences
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3. Linkages Exist Between Natural Hazards
• Hazards are linked to each other
– Some events may cause others
– Example: Hurricanes and flooding
• Hazards linked to earth materials
– Example: Some rock types are prone to landslides
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4. Humans Can Turn Disastrous Events into
Catastrophes: Examples of Disasters in
Densely Populated Areas
• Increases number of people at risk
– More loss of life compared to hazardous event in a less
dense area
• Examples
– Mexico City: 10,000 killed in 1985 8.0 earthquake
– Izmit, Turkey: more than 17,000 killed from 1999
earthquakes
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4. Humans Can Turn Disastrous Events into
Catastrophes: Population Growth as a
Factor in Hazards
• World’s population has more than tripled in the past
70 years
– Population grows exponentially
• Increases exposure to hazards, increased pollution,
reduced availability of food and clean drinking water,
and a greater need for waste disposal and energy
resources
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The Twentieth-Century Rapid Rise in Human
Population
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4. Humans Can Turn Disastrous Events into
Catastrophes: Magnitude and Frequency of
Hazardous Events
• Impact of hazards depend on
– Magnitude: Amount of energy released
– Frequency: Interval between occurrences
– Other factors: climate, geology, vegetation, population,
and land use
• Magnitude-frequency concept
– Frequency of an event inversely related to magnitude
• Land use affects magnitude and frequency of events
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5. Consequences of Hazards Can Be Minimized
• Primarily reactive in dealing with hazards
– Search and rescue
– Firefighting
– Providing emergency food, water, and shelter
• Need to increase efforts to anticipate disasters and
their effects
– Land-use planning limitations
– Hazard-resistant construction
– Hazard modification or control
• Total losses are direct losses and losses related to
human actions
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5. Consequences of Hazards Can Be Minimized:
Reactive Response
• Effects from a disaster can be
– Direct (felt by fewer individuals): people killed or
dislocated, buildings damaged, etc.
– Indirect (affect many more people): emotional distress,
donation of money or goods, taxes for recovery, etc.
• Recovery from disaster
– Emergency work
– Restoration of services and communication lines
– Reconstruction
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Recovery from Disaster
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5. Consequences of Hazards Can Be Minimized:
Anticipatory Response
• Options for avoiding and minimizing effects of
disasters depends on
– Perception of hazards
– Attitudes of people to be affected
– Awareness
• Anticipatory options include
–
–
–
–
–
Land-use planning
Insurance
Evacuation
Disaster preparedness
Artificial control
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1.5 Many Hazards Provide a Natural Service
Function
• There are some benefits to hazards
• Examples:
– Flooding provides nutrients for soil
– Landslides form dams to create lakes
– Volcanoes create new land
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1.6 Global Climate Change and Hazards
• Global climate change is likely to change the
incidence of some natural hazards
– Sea-level rise increases coastal erosion
– Deserts and semiarid regions are likely to expand
– Warmer ocean water is likely to increase storm activity
© 2015 Pearson Education, Inc.
Chapter 1 Summary
• Hazards involve repetitive events.
• Geological conditions and materials largely govern
the type, location, and intensity of natural processes.
• Subcycles of the geological cycle are the tectonic
cycle, rock cycle, hydrological cycle, and various
biogeochemical cycles.
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Chapter 1 Summary, cont.
• Five fundamental concepts establish a philosophical
framework for studying natural hazards:
1. Science helps us predict hazards.
2. Risk analysis is an important component in our
understanding of the effects of hazardous processes.
3. Linkages exist between different natural hazards as well
as between hazards and the physical environment.
4. Hazardous events that previously produced disasters are
now producing catastrophes.
5. Consequences of hazards can be minimized.
© 2015 Pearson Education, Inc.
Chapter 1 Summary, cont.
• Environmental unity states that one action often
leads to others in a sequence.
• Human population growth and poor land-use
decisions are turning former disasters into
catastrophes.
• The magnitude-frequency concept states that the
larger the magnitude of a natural process, the less
frequently it occurs.
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Chapter 1 Summary, cont.
• Consequences of a natural hazard event can
produce loss of life and property.
• Natural service functions refer to benefits provided
by a particular process.
• Global climate change will likely affect the frequency
and intensity of natural hazards.
© 2015 Pearson Education, Inc.