Credit:
Adapted from an activity by Robert A. Bauer: "GeoActivity HAZD-1" in Treworgy, J., ed. 2000. ISGS GeoActivities Series: Activities and Other Resources for Teaching Geology. Champaign, IL: Illinois State Geological Survey. See Print Resources below for ordering information.

Grade Level: 7-8

Purpose: To raise awareness of earthquakes in Illinois.

Suggested Goals:

1. To develop an awareness of the occurrences of earthquakes in Illinois and their past and potential future damage.
2. To look at the distribution of earthquakes in a central US region, including; Illinois, Missouri, Arkansas, Kentucky, Tennessee, Indiana, and Ohio.
3. To introduce the Mercalli intensity scale and the Richter magnitude scale and compare and contrast them with each other.

Objectives: On completion of this lesson, students will be able to:

1. To show, using real data, how the distribution of damage from an earthquake is dependent on regional geology.
2. Recognize the terms: earthquake, epicenter, intensity, magnitude, Modified Mercalli intensity scale, Richter magnitude scale, seismograph.

Background:
Before beginning this activity, the instructor needs to define for students both the Mercalli intensity scale and the Richter magnitude scale, comparing and contrasting them with each other (descriptions of both are available in the PDF download version of this lesson). Explain to students how geologic materials play a major role in the damage that can occur in an earthquake-affected area.

It has been known for decades that loose, unconsolidated surface materials can amplify earthquake ground motions that are traveling through the bedrock. This amplification causes more shaking and, hence, more damage to structures. Illinois has an abundance of loose, unconsolidated surface materials, particularly along the major river valleys.

The distribution of greatest intensities illustrated by the map clearly shows that the major river valleys of Illinois (Mississippi, Illinois, Ohio, and Wabash Rivers) are the areas with the greatest potential for damage from an earthquake.

Media coverage after major earthquakes often includes maps that show simple concentric rings of reduced damage spreading out from the epicenter. In reality, as this activity shows, the pattern of damage is much more complex and depends on geologic materials and distance.

On the map used for this activity, points labeled intensity 8 correspond to the epicenter of this earthquake, but that does not necessarily have to be the case. Local geology could have caused the severe damage in this locality by intensifying ground motions there while the epicenter could have been some distance away. The 1985 Mexico City earthquake provides an example of such a situation. The epicenter was off the coast of Acapulco, but little damage occurred in this area of exposed bedrock. The most severe damage occurred in Mexico City, located about 150 miles away, which was built on thick ancient lake deposits and fill.

Materials:

• Handouts for each student/group (included in the PDF download version of this lesson):
  • Midwest earthquake intensity map
  • Evaluating an Illinois Earthquake – Investigation Sheet
• Crayons, colored pencils, or markers (2 colors per student/group)

Procedure:

1. Discuss the Richter magnitude scale and Mercalli intensity scale; compare and contrast.
2. Examine the Midwest earthquake intensity map.
3. Complete the Evaluating and Illinois Earthquake Investigation Sheet.

Assessment:

1. Observe participation in discussions.
2. Evaluate answers to worksheet questions.

Print Resources:

• Treworgy, J., ed. 2000. ISGS GeoActivities Series: Activities and Other Resources for Teaching Geology. Champaign, IL: Illinois State Geological Survey. [This notebook, filled with lessons (geared for grades 4-12) and an abundance of background material, can be purchased for $20 from: ISGS, Attn: Order Dept., 615 East Peabody Dr., Champaign, IL 61820-6964 or from their Web site: http://www.isgs.uiuc.edu/isgsroot/servs/pubs/toc.htm

Lesson Specifics:

• Skills - investigation, observation, predicting, map reading, estimating, measuring
• Setting - classroom
• Time Required - one 40-minute class session
• Group size - whole class

Illinois State Board of Education Goals and Standards:

• 11.A.2b: Collect data for investigations using scientific process skills including observing, estimating and measuring.
• 11.A.2d: Use data to produce reasonable explanations.
• 11.A.2e: Report and display the results of individual and group investigations.
• 12.E.2a: Identify and explain natural cycles of the Earth's land, water and atmospheric systems (e.g., rock cycle, water cycle, weather patterns).