Plate Tectonic - Earthquakes (5)  Post Lab
 OBJECTIVES: Analyzing earthquakes around the world. Predicting future earthquake by looking at data. VOCABULARY: earthquakes Mercalli Scale Richter Scale MATERIALS: worksheet relief map of the world Students use a worksheet to identify global patterns in the occurrence of earthquakes. San Fernando, 1971
 BACKGROUND: Earthquakes have occurred for as long as the Earth has had a solid crust. They will continue until the Earth turns into a solid rock. Our great grandchildren will have to live with the possibilities of earthquakes. Students should realize that earthquakes generally recur in the same locations. It is reasonable to assume that if one earthquake strikes an area, there will probably be more. Earthquakes are caused by stresses from plate movement. Most earthquakes thus occur at plate boundaries, where pieces of the lithosphere converge, diverge, or slide past each other. This is also true for most volcano related earthquakes, as most volcanoes form at plate boundaries as well. In particularly, earthquakes and volcanoes are very common along the "Ring of Fire", the belt of converging plate boundaries that circles the Pacific Ocean. PROCEDURE: Explain to the class that earthquakes tend to recur in the same areas, and that these areas are usually at or near plate boundaries. Explain the map on the worksheet to the class. This global map shows all the large earthquakes that occurred between 1904 and 1980. The Richter Scale magnitude of each earthquake is listed for each event.    Have the students complete the worksheet. You may want the students to trace the general area where large earthquakes have historically occurred. This looks particularly dramatic with a colored pencil or pen. You may want to trace along with the class.    Ask the students if these areas will have earthquakes again. The answer is yes, because where plates meet there will be stress until they stop moving.    Instruct the students to write about the areas that are free from earthquakes, and to explain why no earthquakes occur there.    If you have a relief map of the world, point out that the areas that have many earthquakes often have high mountains: these are either volcanoes or compressional mountain ranges. The latter form at converging plate boundaries. ANSWERS: Many earthquakes have occurred along the rim of the Pacific Ocean, especially in the following areas: Southern Alaska, Japan, and Chile. The area between China and India also has had many large earthquakes (This is the Himalaya Mountains, a compressional mountain range).    Large earthquakes are not likely to occur in Australia, the eastern coast of North America and South America, and in the interior of Africa.