GO IN DEPTH

Earthquakes

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Materials

 
Earthquakes

Purpose

To verify that earthquakes follow the natural plate boundaries and that these boundaries help us predict where earthquakes are most likely to occur. To examine changes in the earth’s surface caused by earthquakes.


Context

Middle-school students should be able to explain how waves, wind, water, and ice shape and reshape the earth's land surface by eroding rock and soil in some areas and depositing them in other areas, sometimes in seasonal layers. The next step will be for them to examine how earthquakes are part of a system of crustal movements that also form and shape the surface of our planet.

Although the mechanisms of quakes have not been understood until recently, it has been possible to find out quite a bit about how they work by observing their effects. Students will track worldwide earthquake activity for a two-week period to distinguish patterns in the earth crustal activity that will identify the plate boundaries. The earth's outermost surface is broken into 12 rigid plates which are 60-200 km thick and float on top of a more fluid zone, much in the way that icebergs float on top of the ocean.

Students will learn how landforms like mountains and oceanic trenches are formed by the tectonic movements at plate boundaries. This lesson briefly reviews the devastating effects of the Great San Francisco Earthquake of 1906 and moves into the realm of present day earthquake study via the U.S. Geological Survey (USGS). Students will investigate and record all earthquakes on the planet above a 4.0 magnitude on the Richter scale. (If you plan to continue this lesson over a longer period of time, plot earthquakes from 5.0 and higher). They will plot the quakes and examine the data for patterns and trends. Through these exercises, students will begin to distinguish patterns that follow the “Ring of Fire.” During this same time period, students will investigate the different types of plate boundaries.


Motivation

Students are fascinated by natural disasters. This activity will allow them to view the direct effects of a devastating and famous earthquake that nearly destroyed San Francisco. Have students use their Great 1906 San Francisco Earthquake student esheet to tour the online museum for the Great San Francisco Earthquake of 1906. Students can fill out The Great 1906 San Francisco Earthquake Response Journal for this activity.

When the assignment is finished, ask students to move into Pair/Share groups and have them share their responses with one or two partners.

Then have students come back together as a group and share their thoughts and questions. A class chart can be created and posted for the duration of this lesson. This will give students an opportunity to share their own experiences with earthquakes and any fears or questions they may have at this time.

Before going on to the Development, ask students: "Do you think the people of San Francisco knew that they were at risk of an earthquake? Who is at risk now? How do we know?"


Development

Write the central question for this lesson in a visible place: "How will plotting current earthquakes and earthquake activity help us identify plate boundaries and possible future seismic activity?"

The Development of this lesson will occur over a two-week period, during which time students will work online to gather real-time data of global earthquakes. Over the course of this two-week period, they also will study plate tectonics and plate boundaries. In the end, students will be able to understand how the two activities are related.

Note: The rate of change with a violent earthquake is sudden and dramatic and the effects can be seen easily. But keep in mind that slower changes also occur along the plate boundaries. These slow, less visible changes take place quietly and go unnoticed for the most part but cause significant changes to the landscape. Mountain formation at a convergent boundary will cause very slow changes.

Part 1: Recording Earthquakes
Students should use the Earthquake Recording Sheet to track all global earthquakes that happen daily during a specific two-week period. Students should start with the date of the first day of this activity and then record the data each day for two weeks. This information can be found at the USGS Latest Earthquakes in the World—Past 7 days website. Students should record only those earthquakes that are a 4.0 magnitude or greater. If students are recording for a longer period of time, they should use 5.0 as their starting point. This information can be noted on the recording sheet. Students then use the longitude and latitude coordinates to plot these quakes on a world map. They should color code the quakes on the wall map and individual maps as follows:


Color Code Individual Maps
4.0 - 4.9 Yellow
5.0 - 5.9 Blue
6.0 - 6.9 Green
7.0 - 7.9 Red
> 8.0 Black

Classroom Wall Map
Use the colored Post-it® Notes to plot information on the classroom wall map.

Once all of the data has been plotted, ask students questions like these:

  • Is there one area that seems to be having more activity than another?
  • Is there a pattern to the size of the quakes?
  • How do you think the depth of the quake may affect the way a quake may be perceived on the surface?
  • Are you hearing about any of these quakes on the news?
  • If so, how did the quake affect the people of that region?
  • Can you begin to predict where there may be earthquake activity the next day?
  • How does this information relate to the other lessons you are learning?

    Answers will vary. Encourage students to explain their responses.

Every couple of days or so, check with students by placing the classroom wall map on the board and add data so students can compare their own data to the class.

Part 2: Understanding Plate Motions
The earth is covered by tectonic plates. The areas where these plates meet are called plate boundaries. There are four types of plate boundaries. Have students use their student esheet to go to Understanding plate motions to read definitions and explanations about these boundaries.

  • Divergent boundaries are where new crust is generated as the plates pull away from each other.
  • Convergent boundaries are where crust is destroyed as one plate dives under another.
  • Transform boundaries are where crust is neither produced nor destroyed as the plates slide horizontally past each other.
  • Plate boundary zones are broad belts in which boundaries are not well defined and the effects of plate interaction are unclear.

Now have students create a Plate Boundary Flipbook that demonstrates the three types of boundaries as shown in the illustration of the Main Types of Plate Boundaries image. You should let the students know which type of boundary you are looking for because there are several examples of each type on the webpage.

Adaptations: Students who have difficulties with this activity can either draw the examples and define the situation or cut and paste the pictures and copy the text.

Once students have completed the assignment, hold a class discussion about the different types of boundaries. If you are interested in delving into the issues of plate movements, What drives the plates? is another section of this website that covers the details of what drives the plate movements. This can move the discussion into a deeper realm of understanding plate movements.

Ask students:

  • Compare and contrast the outward features created by plate movement at divergent plate boundaries to those formed at convergent plate boundaries. Can you find real-life examples of this? (Divergent boundaries create cracks and fissures in the ground and magma from the earth’s interior can seep out. Examples would be the Great Rift Valley in Africa, as well as the rift in Iceland. The convergent boundaries act just in the reverse of that. Here plates crash up against one another and create towering mountain ranges like the Andes in South America and the Cascade Range in Washington state.)

Assessment

Print out a copy of the plate boundaries from the USGS Plates of the Earth site for each student and also show it on an overhead projector. Students should then compare their earthquake activity map to that of the plate boundaries. This particular map of the plate boundaries enables students to see the different types of plate boundaries that they studied in part 2.

Ask students:

  • Is there a pattern? What is this? (Possible answer: The pattern is that the earthquakes should become visible along the fault lines. Some students may notice that they tend to come in clusters of activity.)
  • Does the activity seem to differ depending on the type of boundary (i.e., is there more activity around convergent, divergent, or transform boundaries or is it the same)?
  • Compare the rate of visible change that might occur with a higher magnitude earthquake (6.0>) with more frequent, lesser magnitude quakes (< 3.0). (Possible answer: While the larger, more visible earthquakes show dramatic changes in the earth’s surface, the smaller, more frequent, and lesser felt quakes also cause changes to the earth’s surface. These changes are slower and less dramatic but can be the cause of entire mountain ranges.)

Compare and contrast the two maps using a T-chart.


Extensions

You can extend the ideas in this lesson by leading students through the Science NetLinks lesson entitled How Sedimentary Rocks are Formed.


The USGS Earthquake Hazards Program website used in this lesson contains several other activities and articles for teachers and students to explore:


Famous Earthquake Accounts by Mark Twain, Jack London, Charles Darwin, and John Muir provides some firsthand observations about earthquakes. After reading these accounts, have students write ones of their own if they have experienced an earthquake.


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Lesson Details

Grades Themes Project 2061 Benchmarks National Science Standards
AAAS Thinkfinity