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© The Norwood Science Center 2005 NORWOOD SCIENCE CENTER Geology Grade 4 Background information: The movement of crustal plates provides the great forces that strain the Earth's crust causing earthquakes to occur. Probably no other natural event has been the cause of more deaths and destruction than earthquakes. Modern technology has given the scientists tools to study these events in detail. The theory of plate tectonics has provided scientists with the ability to explain why they occur. There is hardly a region on Earth where an earthquake will not occur, given sufficient time. Most serious earthquakes occur where the crustal plates come together. The boundaries between the plates are actually huge cracks in the crust. As the plates slowly move, their edges grind together. The plates move against each other along these cracks in crustal rocks. A place where the rock has moved on one or both sides of a crack is called a fault. Almost all large earthquakes take place when rocks suddenly snap along faults. If the rocks along a fault were constantly moving, their surfaces would soon be worn smooth. The rocks would slide gently like a well-oiled drawer. However, the rock surfaces are jagged. The sides of a fault area usually are locked together like a Earthquakes Gr. 4 © The Norwood Science Center 2005 sticky drawer. This causes stress. When the stress becomes too great, the rocks suddenly snap and slip along the fault. This movement causes a sudden release of the built-up stress causing an earthquake. There are a number of places in the world where earthquakes occur frequently. In this lesson, students will explore where earthquakes most often occur and find that they are related to crustal plate boundaries. Earthquakes Gr. 4 © The Norwood Science Center 2005 TITLE: EARTHQUAKES PURPOSE: Can you predict earthquake locations? MATERIALS: (per teacher) One crustal plate map of world with plate numbers Overhead of crustal plate map Overhead markers (per student) One crustal plate map of the world with numbers One earthquake coordinate worksheet Pencil PROCEDURE: Advanced preparation: 01. Teacher should prepare an overhead of the crustal plate map. Classroom lesson: 02. Pair students into teams. 03. Distribute one crustal plate map to each student. 04. Using the overhead, have students write the names of the seven major crustal plates of the Earth’s crust in the lower margin of their map: • #1 – Pacific Plate (on both sides of the map) • #2 – North American Plate • #3 – South American Plate • #4 – Antarctic Plate • #5 – African Plate • #6 – Eurasian Plate • #7 – Indian-Australian Plate Discuss with students that the areas on the map indicated with the jagged bold lines are the boundaries between these major crustal plates. 05. Earthquakes Gr. 4 © The Norwood Science Center 2005 07. Most serious earthquakes occur where the crustal plates come together. The boundaries between the plates are actually huge cracks in the crust. As the plates slowly move, their edges grind together. The plates move against each other along these cracks in crustal rocks. A place where the rock has moved on one or both sides of a crack is called a fault. 08. Distribute one earthquake coordinate worksheet to each student. Explain to the class that the coordinates given were derived from actual earthquake activity that occurred during those time periods. 09. Guide students in locating the first two positions where earthquakes occurred. 10. Discuss with students that magnitude indicates the power of an earthquake as measured on the Richter Scale. The scale uses numbers to show the amount of energy released by an earthquake. Each number on the scale represents ten times as much energy as the next lower number. For example, an earthquake with a magnitude of 5 is ten times stronger than an earthquake with a magnitude of 4. Most earthquakes are small with Richter measurements of four or less. Large earthquakes with values of eight or more usually take place only once every five to ten years. 11. Student teams should complete locating all earthquakes. Earthquakes Gr. 4 © The Norwood Science Center 2005 CONCLUSION: After locating all the earthquakes, have students answer the following questions: 01. Describe where the earthquakes are located. 02. Is there a relationship between the earthquake positions and the shape of the continents? 03. Describer how the locations of the earthquakes are related to crustal plate boundaries. 04. Complete the following sentence: The pattern we found for earthquake locations suggests that future earthquakes may occur … SOURCE: 01. Earth Science. Holt, Rinehart and Winston, New York, 1986. Earthquakes Gr. 4