Lesson 5: Natural Hazards
This is the third of three lessons that introduce key geologic topics in order to provide essential background for the more focused discussions of specific hazards and resources we'll be having later in the semester.
This week we'll examine natural hazards. We'll review the circumstances under which they lead to disasters, how we assess the risks they pose, and what strategies we can use to lessen the damage and loss of life they cause. In the weeks ahead we'll focus mostly on geologic hazards, but it's important to realize that in many instances it is "secondary" hazards—such as fires (as after the 1994 Northridge earthquake, at right) and building collapses—that pose the most serious threats to life and property. Although we cannot prevent hazardous geologic events we can minimize the tolls they take by moving people out of threatened areas and strengthening buildings and infrastructure. Following through on the decision to make such changes is often difficult and expensive, however, and point out that—when it comes to protecting people from geologic hazards—human values may play just as large a role as geologic knowledge.
As you read through the introduction to natural hazards in our text and work through the earthquake hazard assessment exercise in Hazard City it will be helpful to take careful notes. Writing out both major points and key supporting details in your own words or making neatly labeled drawings of key features will help you better understand the significance of what you've read and spot any gaps in your knowledge. Having complete notes will also make it easier for you to review for this week's quiz and and access what you've learned when you want to refer back to it later in the semester. Be sure that you are prepared to meet the learning objectives outlined below before you move on to the quiz at the bottom of the page.
Weekly Learning Objectives
Upon successful completion of this week's lesson, a student is expected to be able to:
- Decide whether a geologic event is better described as a disaster or a catastrophe and explain his or her reasoning;
- List the two key pieces of information needed to determine the risk posed by a natural hazard and calculate this risk;
- Predict how the frequency of a hazardous event (e.g., earthquake, volcanic eruption or flood) is likely to be related to its magnitude, and describe how much events of different magnitudes typically contribute to the planetary changes caused by geologic processes;
- Contrast a prediction from a forecast of a hazardous natural event, and briefly describe the information needed to make a useful prediction or forecast;
- Distinguish natural hazards whose consequences are likely to be affected by human activities (e.g. deforestation and climate change) from those that are not, and briefly describe the roles that human activities play in changing the affected processes;
- Differentiate between reactive and anticipatory (proactive) responses to hazardous natural events.
Reading and Browsing Assignment
- Read Chapter 5, and focus on the general principles mentioned above rather that the details of specific examples. Even though these ideas may seem a little vague or general right now we will return to them as we examine specific examples later during the semester.
- Browse through the NaturalHazards.org website. In addition to providing background information on specific hazards this site also has an link to current natural hazard advisories in any area you choose. See, for example, if you can find out what the current hazard status is for volcanoes here in the High Cascades.
- Finally, check out EarthAlerts for an interactive map on which icons will take you to brief summaries about a wide range of natural hazards that have recently occurred around the world.
Exercise 5: Earthquake Damage Assessment (Due by 9:00 AM on 19-Sep-2011)
After you have read the chapter please go to the Hazard City site and work through version 1 of the Earthquake Damage Assessment exercise. Remember, to get to Hazard City point your browser to the mygeoscienceplace site, scroll down to the icon for our textbook, click on it and log in. Then click on "Hazard City" in the left-hand column, scroll down to Earthquake Damage Assessment and click on version 1 to view an outline of the activity. To start the exercise click on the introduction and read through it carefully. Even though the introductory text mentions "buttons at the bottom of the page", you'll need to use the back button on your browser to return to the outline page so that you can access the other parts of the assignment. When you bring up the map of Hazard City just click on a neighborhood to see a description of the homes there. Be sure to write down the percentages of buildings rendered uninhabitable and the numbers of people who will need shelter from each neighborhood as you work through the exercise. (You may want to print the report form provided and fill in the data as you go.) Once you have gathered all of the required data go to the "Assignments, Tests, and Surveys" area in Etudes and use what you have learned to answer the questions in Exercise 5. When you answer questions that ask for numerical results please (1) give your answers in number rather than text form (i.e. 50 rather than fifty); and (2) always round to the nearest whole number. Finally, don't worry if you submit your exercise and Etudes comes back with a score that seems too low. Different people may read the graphs in the exercise slightly differently and as long as your percentages are reasonable (±1-2%) and your values are calculated and rounded correctly I will give you credit when I review your submission. Details are critical in this exercise, so allow about an hour to work through it.
Quiz 5: Geologic Hazards (Due by 9:00 AM on 19-Sep-2011.)
After you feel you have met the learning outcomes outlined above, please complete Quiz 5 in the Etudes "Assignments, Tests, and Surveys" area. There are ten questions, each worth one point. If you can answer all of them correctly it means that you know your way around the basics of natural hazards pretty well and are ready to move on to a more detailed look at the causes and potential hazards posed by earthquakes next week. Like all of our weekly quizzes, this one is timed (you'll have 30 minutes) and must be completed in one "sitting" (that is, you will only be granted access once.) So, be sure you're ready to complete your quiz when you start it—and be sure you're using Firefox. Good luck.