Where in the World Are All the Earthquakes?

Curry School of Education, University of Virginia www.teacherlink.org/content/science/ Where in the World Are All the Earthquakes? In this activity, students go to the United States Geological Survey (USGS) National Earthquake Information Center on the Internet and download actual seismic data for their birth date. Students then transfer this data to a spreadsheet and then project it onto a world map, from which they can make inferences concerning hot zones and tectonic plates Students typically learn about tectonic plates by looking at a map in a textbook. In this activity students manipulate and graph actual seismic data to discover the location of tectonic plates. Using the spreadsheet, students can easily plot a hundred or more earthquakes on a world map background, saving the time and tedium of hand plotting. The activity supports higher level thinking skills while using current information available on the Internet.

Virginia Standards of Learning addressed in this activity include: Earth Science.1 The student will plan and conduct investigations in which: Technologies, including computers, are used to collect, analyze, and report data and to demonstrate concepts and simulate experimental conditions; Scales, diagrams, maps, charts, graphs, tables, and profiles are constructed and interpreted A scientific viewpoint is constructed and defended. Earth Science.2 The student will demonstrate scientific reasoning and logic by: Analyzing how science explains and predicts the interactions and dynamics of complex Earth systems; Evaluating evidence for scientific theories related to plate tectonics, the structure of the Earth, and its ancient age and origin; Earth Science.3 The student will investigate and understand how to read and interpret maps, globes, models, charts, and imagery. Key concepts include location by latitude and longitude and topographic profiles. Earth Science. 8 The student will investigate and understand geologic processes including plate tectonics. Key concepts include: Processes (faulting, folding, volcanism, metamorphism, weathering, erosion, deposition, and sedimentation) and their resulting features; and Tectonic processes (subduction, rifting and sea floor spreading, and continental collision). Computer with compatible spreadsheet program (Microsoft Excel, Appleworks, etc.) Internet access worldmap.gif file (Save this map to your desktop before beginning this activity) 2

NOTE TO TEACHERS: These procedures are written to show you how you might use these technologies to teach science concepts. Suggested questions, approaches, and expected answers are all provided. Therefore, these activity descriptions should be used as a guide for your instructional planning, rather than as a step-by-step activity guide for students. Getting Started Where are some places in the world where you've heard of earthquakes occurring? When we hear about earthquakes in the United States, many of them seem to be occurring in the Pacific Coast states. It seems from what we hear in the media that earthquakes are concentrated in certain areas of the world. Is this a real pattern or just an artifact of selective reporting by the media? Are earthquakes distributed evenly around the globe or concentrated in specific areas? One way to find out would be to plot lots of real earthquake data on a map of the world to see where they are occurring. Accessing the Data The earthquake database utilized in this activity is available at the United States Geological Survey (USGS) National Earthquake Information Center web site (http://neic.usgs.gov). You can access the earthquake database by clicking on Earthquake Search in the bulleted list. 3

Scroll down to Select the Search Area and select Global (Worldwide). Select Output Format: 3. Screen file format of 80 columns, then scroll down the screen to the Optional Search Parameters. Obviously, you can't work with all the earthquake data ever collected, so you need to work with a practical data set. You might find it interesting to select the earthquake data from your birthdate. MAGNITUDE Magnitude readings of earthquakes use the Richter scale, with magnitudes ranging from 0.1-9.9. The scale is logarithmic, so that, for example, an earthquake with the magnitude of 3 is ten times more powerful than an earthquake with a magnitude of 2. If you were born April 26, 1986, you would set the parameters as follows and click on Submit Search: 4

Transferring the Data You'll probably see anywhere from 20 to 100 data entries for individual earthquakes listed for your birthdate. It's unlikely that you will be able to answer the research question by looking at raw data, however. You need to manipulate the data in some way. One way to do this is by plotting the earthquake locations on a world map. You could do this by drawing dots on a paper map, but it is much easier to do with a spreadsheet. First, transfer the earthquake data into a spreadsheet. (The examples shown here use a Microsoft Excel spreadsheet.) Highlight the data table beginning with the column headings and copy. 5

Next, open Excel and paste the data into a new spreadsheet. Save the spreadsheet to the desktop, using your name as the filename. The spreadsheet may not separate the columns correctly. If not, you can select the first column and convert "Text to Columns," a command found under Data on the pull-down menu. Choose "fixed width," select Next, and the data should be converted neatly into columns. 6

Now look at the data you have: Year, Month, Day, Origin Time, Latitude, Longitude, Depth, and Magnitude. Obviously, there's more information here than you need to plot the locations of the earthquakes. Which data do you need to answer the research question: Are earthquakes distributed evenly around the globe or concentrated in specific areas? Since you will be adding earthquake data for other dates later in the activity, we recommend that you keep the Year, Month, Data, Latitude, and Longitude columns. You may delete all the remaining columns. 7

Graphing the Data Now that you have the relevant data in the right format, you can create a scatterplot graph of the earthquake locations superimposed on a map of the world. To do this, highlight the Latitude and Longitude columns and select the Chart Wizard icon. 8

For chart type, choose "XY (Scatter)" and select Next. Click on the Series tab. The default value is to set the first column of data from the left as the X-values (Column D in this example), and the next column as the Y-values. For this graph, you will need to reverse the order of those settings. Set the longitude column as your X-Values and the latitude column as the Y-Values. 9

Click Next, give the graph a title, and label each axis. Turn off the legend and click on Next. Save as a new chart. Your graph will look something like this, but it's still not ready to be superimposed on the world map. 10

Formatting the Plot Area For the data points to line up correctly with the world map we have provided, the axes of the graph must line up with the longitude and latitude on the map. You must set the scales exactly as instructed in the following. (If you use a different picture under the graph, you will have to figure out the correct maximum and minimum values.) Double click on the Y-axis of the graph and choose the Scale tab. Replace all the default values with the following: Minimum value = -90; Maximum value = 70; Major unit = 30; Minor unit = 10=; and Crosses at -90. 11

Next you will format the X axis in a similar manner, entering the following data: Minimum value = -180; Maximum value = 180; Major unit = 30; Minor unit = 10; and Crosses at -180. The graph should now look something like this: 12

You are now ready to set a prepared world map as the background to see where these earthquakes actually take place. This is done by right clicking in the plot area, and choosing "Format Plot Area." Next click on Fill Effects and select the Picture tab. Then click on Select Picture and locate the world_map.gif file you saved to your desktop. Select OK and then OK again, and your plot area should look similar to the following: Answering the Research Question As you look at the data, think back to the original research question. Likely, the earthquake data for only one date will not be enough to present a pattern. To get enough data for a pattern to emerge, add earthquake data from other days (try using the birthdates of at least five of your classmates). The more dates you add, the more obvious the pattern becomes. Go back to the USGS webpage (http://neic.usgs.gov/neis/epic/epic_global.html) and submit a search for each new birthdate. For each date, copy and paste the data to a new sheet in your spreadsheet. Then copy the latitude and longitude columns, and paste them at the ends of the latitude and longitude columns in Sheet 1 (your original data). Now create a new scatterplot graph using all of the combined data with the world_map.gif as the background. 13

As you look at your map, try to answer the following questions: Are there places where earthquakes occur more frequently? Why do you think earthquakes tend to occur in some areas and not in others? Where are earthquakes most common in the United States? (Be sure to consider Hawaii and Alaska.) Where would you live to avoid earthquakes in the United States? Now view the USGS seismicity map available at http://neic.usgs.gov/neis/general/seismicity/world.html. Compare the class map to the USGS earthquake map. This map illustrates all of the earthquake data collected 1975-1995, which outlines the tectonic plate boundaries. For more information about relationships between earthquake locations and tectonic boundaries, see http://www.seismo.unr.edu/ftp/pub/louie/class/100/plate-tectonics.html 14

You may find that not all the points on your graph fall along the plate boundaries, especially earthquakes located near the poles. Because the earth is a globe, any flat map of the earth will be somewhat distorted, and this distortion is greatest at the poles. Modifications The USGS collects data on earthquake and volcanoes to monitor geologic activity around the globe. In addition to plotting earthquake data, you may also to include volcano data on the world map. You can then compare the proximity of earthquake and volcanic activity. Through this activity, you should be able to identify that there is a relationship between the two phenomena. A world volcanic database is available at the National Geophysical Data Center (NGDC) (a division of the National Oceanic and Atmospheric Administration [NOAA]) (http://www.ngdc.noaa.gov/seg/hazard/volcano.shtml). Similar to the earthquake database used in this activity, filters are provided on the volcanic database so that you can input your birth year to gather volcanic data. Throughout the lesson, formative assessments can be made to determine students' ability to download data from an online database, import data into a spreadsheet, and create graphs. In addition, more formal assessments might include: Given the location of an earthquake (latitude and longitude) and a map showing tectonic plate boundaries, students should explain whether the earthquake is most likely the result of activity at plate boundaries or some other geologic phenomena. 15

A thrill seeking friend of yours says, "I really want to experience an earthquake!" Using the USGS earthquake database and your knowledge of earthquakes, suggest the top three destinations your friend might travel to for the best chance at an earth shaking holiday. Provide reasons to support your chosen destinations. Earthquake Data at NGDC http://www.ngdc.noaa.gov/seg/hazard/earthqk.shtml The National Geophysical Data Center (NGDC) provides extensive information about earthquakes including earthquake slide sets, earthquake databases, and information on strong earthquakes. Welcome to the U.S. Geological Survey Earthquake Hazards Program Website http://earthquake.usgs.gov/ This site serves as the gateway to the USGS Earthquake Hazards Program information including databases, information about recent earthquakes, information and lesson plans for teachers, student information, earthquake research and more. USGS General Earthquake Information http://neic.usgs.gov/neis/general/handouts/general_seismicity.html#world The United States Geological Survey (USGS) Earthquake Hazards Program world earthquake site including US and world earthquake databases, maps of the US and the world for graphing earthquake data, and a list of the strongest earthquakes and most recent earthquake events. NGDC Geologic Hazards Photos http://www.ngdc.noaa.gov/seg/fliers/se-0801.shtml This National Geophysical Data Center site provides slide sets on geologic hazards including earthquakes and volcanoes. Slides may be used online or ordered from NGDC. National Geophysical Data Center http://www.ngdc.noaa.gov/seg/hazard/volcano.shtml 16

The National Geophysical Data Center acquires and disseminates volcano data and slide sets. Plate Tectonics, the Cause of Earthquakes http://www.seismo.unr.edu/ftp/pub/louie/class/100/plate-tectonics.html This site explains the relationship between earthquakes and plate tectonics. Other interesting sites addressing plate tectonics include http://www.platetectonics.com http://www.ucmp.berkeley.edu/geology/tectonics.html http://www.branches.co.uk/earth/tectonic.htm Contact: Randy L. Bell Asst Professor of Science Education Curry School of Education University of Virginia Charlottesville, VA 22904 email: randybell@virginia.edu 17