Earthquakes and Related Phenomena
Introduction to Natural Hazards
Learning Objectives
After reading and studying this chapter, students should
▪ Understand why increasing population and changing land use increase the threat of loss of
life and property from a natural disaster to the level of a catastrophe
▪ Know the conditions that make some natural Earth processes hazardous to people
▪ Understand how a natural process that gives rise to disasters may also be beneficial to
people
Chapter Summary
This chapter focuses on the general topic of natural hazards and discusses the reasons that natural
processes adversely affect humans, the main methods of hazard reduction, and the nature of human
responses. The first section of the chapter focuses on the characteristics of potentially hazardous
natural processes, including magnitude and frequency and the benefits and adverse effects of natural
hazards. Subsequent sections discuss the evaluation and prediction of hazards, and the human
responses to hazards. The chapter closes with sections on the potential impacts of climate change,
population increase, and land-use changes on natural hazards.
Chapter Outline
I. Hazards, Disasters, and Natural Processes
A. Criteria used to define natural disaster—one or more of the following:
2. One hundred or more people are affected
4. There is a request for international assistance
B. Natural disasters are increasing in number
C. Natural disasters: loss of life and property damages
1. Natural disasters kill an average of 150,000 people, and cost $50 billion in property damage
each year
2. Disasters are worse due to increased population and land use patterns
D. Why natural processes are sometimes hazards
5
5
3. Environmental geologists are responsible for identifying hazards and giving that information to
4. Solutions to minimizing hazards are simple but can be hard to see
E. Magnitude and frequency (see: A Closer Look: The Magnitude-Frequency Concept)
1. Magnitude: amount of energy released in a disastrous event
3. The impact of a disastrous event is determined by many factors, including magnitude,
F. Benefits of natural hazards
1. examples include flood-delivered nutrients in floodplain soils, landslide-dammed mountain
G. Death and damage caused by natural hazards (see Table 5.1)
1. More deaths do not always mean more property damage
2. Potential of a natural hazard to produce a catastrophe is important
3. Effects of natural hazards change with time and land-use patterns
II. Evaluating Hazards: History, Linkages, Disaster Prediction, and Risk Assessment
A. Fundamental principles concerning natural hazards
1. Hazards are known from scientific evaluation
2. Risk analysis is an important component in understanding impacts resulting from
hazardous processes
4. Hazardous events that previously produced disasters are often now producing catastrophes
B. Role of history in understanding hazards
1. Hazards are repetitive events whose history provides information for reducing them
3. Geologists can “read the landscape”; environmental geologists can also identify landforms
associated with hazards
C. Linkages between hazardous events
1. Many hazards themselves are linked
2. Natural hazards and the characteristics of Earth materials can also be linked
D. Disaster forecast, prediction, and warning
1. Prediction–the date, time, and size of the event are specified
3. Forecasting and predicting hazards are important in minimizing their impacts
4. Effects of disasters can be reduced by:
a. Identifying the location where a hazardous event will likely occur
E. Risk assessment
Earthquakes and Related Phenomena
2. acceptable risk
3. problems and opportunities for risk assessment
a. lack of reliable data is often a major problem
III. The human response to hazards
A. Reactive response: impact of and recovery from disasters
1. direct effects of disaster
2. indirect effects of disaster: responses
3. stages of recovery
a. emergency work
B. Anticipatory response: perceiving, avoiding, and adjusting to hazards
1. hazard perception
2. land-use planning
3. insurance
5. disaster preparedness
C. Disaster preparedness
2. Training for evacuations
D. Artificial control of natural processes
1. attempts have met with mixed success
IV. Global climate and hazards
A. Global and regional climate change may significantly affect incidence of storms, landslides,
drought, fires
1. how climate change may affect magnitude and frequency of natural events
2. warming of oceans will channel more energy from ocean water into atmosphere
a. likely will increase hazardous weather-related processes
V. Population increase, land-use change, and natural hazards
A. Population increase and hazardous events
1. as population increases, need for planning to minimize losses from natural disasters also
increases
a. more people at risk of an event
b. forces more people into hazardous areas
B. Land-use change and hazardous events
1. past half-century has seen dramatic increase in great catastrophes
2. vast majority of natural disaster deaths between 1985–1995 were in developing world
Answers to Review Questions and Critical Thinking Questions
Review Questions
1. Better communication is needed between civil defense authorities and local authorities, and
population and land-use changes intensify impacts of natural hazards.
3. Magnitude refers to the scale of an event, while frequency refers to the length of time between
events.
5. Natural hazards are repetitive; therefore, historical and geological records are guides to hazard
reduction.
7. Identifying the location where a hazardous event will likely occur, determining the probability that an
event of a given magnitude will occur, and observing precursor events.
8. Forecasting: predicting when disaster will occur, on a scale of days to months, with a range of
10. Determine the probability of an event and determine the potential consequences, then determine the
acceptable level of risk. The latter task is typically very complicated.
12. Land-use planning, insurance, evacuation, disaster preparedness
14. Population growth increases the number of people potentially affected, and forces people into
Critical Thinking Questions
1. An answer to this question will depend strongly on the student’s location, but will generally require
research into natural hazard potential and community preparedness.
2. An answer to this question should focus on the balance between unnecessary concern (and
Earthquakes and Related Phenomena
3. This task, if roles are played well, should reveal differences between the motivations and approaches
of scientists and the media, and may reveal more productive means of communication.
4. A student undertaking this task will need to examine data concerning the history of flooding, the