EARTHQUAKES! Tectonics, Faulting and Earthquakes

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2 Name: Student Number: Tectonics, Faulting and Earthquakes Purpose: To illustrate how the Earth s lithosphere is deformed by tectonic forces, and use real-time earthquake data from the internet to explore the relationship between earthquakes and plate tectonic boundaries. Introduction: We live on huge tectonic plates that shift and interact with one another. Plates can produce tensional stress, pulling the crust apart as two plates go their separate ways. Compressional stress can be produced when two plates collide, large volcanoes or mountain ranges can result from this stress. Shear stress can twist the crust as two plates slide past one another. All of this pushing, pulling and twisting of rock can produce a lot of friction and cracking. As rocks crack or shift with all this motion, energy is released in the form of EARTHQUAKES! Candy Bar Tectonics An easy and tasty way to illustrate plate tectonics is using candy bars, such as Snickers or Mars I think a mini Mars bar produces the best example. This simple activity is a great discussion starter for any lesson on plate tectonics! Procedure: Have students wash their hands before starting this activity! They should use a fingernail, straightedge or butter knife to make a few breaks in the "crust" or top of the candy bar. To illustrate tension (associated with normal faults) have them gently and slowly pull on the edges of the candy bar. They will notice that the "plates" move apart to reveal the caramel/nuts or "asthenosphere". To illustrate the force of compression (associated with reverse and thrust faults) have the students push on both ends of the candy bar to squeeze it together. They should notice the plates colliding and possible see one slide over the top of another. To illustrate the force of shearing (associated with lateral fault) have the students push the plates back together, then slide one half of the candy bar forward and the other backwards. 1. Label the part of the candy bar to correspond to the mechanical layers of the Earth.

3 2. Use your fingernail, straightedge, or butter knife to make small cracks in the surface of your Earth. What do we call the cracks in the Earth s surface? What do we call the large pieces of Earth s crust? 3. Tension is a force that pulls on the plates of Earth s crust causing them to move apart. Slowly pull on the ends of your candy bar. What happens? (list two things you observed) What type of fault was created? Draw a cross-section (a view from the side): Which tectonic plate boundary does this represent? 4. Compression is a force that pushes on the plates of Earth s crust causing them to move together. Slowly push the ends of your candy bar towards one another. What happens? (list two things you observed) What type of fault was created?

4 Draw a cross-section (a view from the side): Which tectonic plate boundary does this represent? 5. Shearing is a force that pushes on the plates of Earth s crust causing one to move in one direction and the other plate in the opposite direction. Slowly push one end of your candy bar towards you and the opposite end away from you. What happens? (list two things you observed) What type of fault was created? Draw a map (a view looking down onto the table top): Why did we not draw a cross-section like before? Which tectonic plate boundary does this represent?

5 Plot Real-Time Earthquake Data There are two ways of doing this activity. The first is quick and all-digital, the second would likely take a couple weeks and involves using a small world map to manually plot individual real-time earthquakes by their latitude and longitude. Either can be accomplished individually or in a small group OR as a class. Procedure: Use one of the web sites listed below to see all of the earthquakes that have occurred over the last 7 or 30 days which were larger than a 2.5 Magnitude, and answer the questions provided. o o First option uses INTERACTIVE MAPS online USGS (Earthquake Hazards Program, For Kids) Latest Quakes Or IRIS Seismic Monitor Use the settings and list options to display earthquake data and plate boundaries. Recent earthquakes (last 7 days or 30 days) be sure to start with the plate boundaries not appearing. Second option would use TEXT-BASED earthquake data USGS Earthquake Bulletin Magnitude Greater Than 2.5 Earthquakes From Around the World OR IRIS List of Earthquakes (last 30 days) Note that in the first two columns you will see the time and date for each earthquake. Note that in the second two columns you will see the latitude and longitude coordinates for the epicentre of the earthquake. A latitude of + corresponds to degrees North and a latitude of - corresponds to degrees South, a longitude of + corresponds to degrees East and a longitude of - corresponds to degrees West. Use the latitude and longitude coordinates to plot a dot on your world map which represents the epicentre of the earthquake. For older students, use a blue star if the earthquake occurred near the surface (less than 100 km) and use a red star if it occurred deep (greater than 100 km) in the earth (you will see the depth measurements in the table.) NOTE: You can use the links that appear in the last column of the table to assist you in finding the locations of the earthquakes if using the latitude and longitude coordinates is too difficult. Use a map of the current tectonic plate boundaries to compare/contrast and answer the following questions. Study the map online or the one you have produced that displays the recent earthquake events. See if you can answer these questions: 6. Do the earthquakes appear to occur all over the earth's surface or only in isolated regions? Is there a recognizable pattern to where earthquakes seem to occur?

6 7. If such a pattern does exist, could you use it to determine where high risk earthquakes zones are located? If so, name several high risk zones: Now, compare the earthquake map to a tectonic plate map, and answer these questions: 8. Do you see any relationship between the earthquake map and the tectonic boundaries? Why so or why not? 9. Identify the locations of shallow and deep earthquakes, and examine the types of boundaries (i.e. convergent, divergent, transform) that exist between certain plates using the figure provided. See if you can answer the following questions: Deep earthquakes seem to correlate to a particular type of plate boundary. Which one and why?

7 10. Do shallow earthquakes seem to correlate to any particular type of plate boundary? If so, what type of boundary and why? 70

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