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Earth Shakes, Rattles, and Rolls Plate Tectonics Earthquakes What is the relationship between the earth’s plates, volcanoes, and earthquakes? Plates http://www.extremescience.com/PlateTectonicsmap.htm Earthquakes Volcanoes http://hsv.com/scitech/earthsci/quake.htm Let’s look at those maps again. http://www.teachersdomain.org/ass et/ess05_int_tectonic/ Plates Volcanoes Earthquakes Earthquakes and Volcanoes are found where plates meet. Evidence Wegener used to support theory of continental drift: • Continents fit like a puzzle • Fossil evidence • Rocks were similar in Africa and South America • Evidence Antarctica once had a tropical climate SUPERCONTINENT PANGAEA How did geologists explain how the earth’s plates moved? To see how geologists believe the plates moved go to the sites below. Notice the Atlantic Ocean seafloor spreading (Handout). Seafloor spreading • More! Label the following: •Trench •Ridge •Crust •Mantle •Outer core •Inner core Use p. 92 (Fig. 10.5) to help! Convection currents in the magma move the earth’s crust. Convection currents in the Earth's mantle are what drive plate motions. Convection currents are driven by the simple fact that hot things (such as gases and liquids) rise while cool things fall. VIDEO • http://www.youtube.com/watch?v=QDqskltCixA Convection currents in action! At left, two animal cookies represent two of the Earth's tectonic plates. At right, the two plates have moved apart, much like what happens at a divergent margin. The chocolate pudding represents the Earth's mantle. The heat source beneath the pot created convection cells in the chocolate pudding. Think of the cookie on the left as South America, and the cookie on the right as Africa. Over time they have moved apart. You'll see this again. http://images.google.com/imgres?imgurl=http://visearth.ucsd.edu:16080/VisE _teach/Kimball/untitled18.jpg&imgrefurl=http://visearth.ucsd.edu:16080/VisE _teach/Kimball/Kimball2.html&h=200&w=308&sz=35&tbnid=sEa1xg46QV MJ:&tbnh=72&tbnw=110&start=9&prev=/images%3Fq%3DCONVECTION %2BCURRENTS%26hl%3Den%26lr%3D%26sa%3DN Earthquakes How do we measure the intensity of an earthquake? epicenter The point on the surface of Earth that is right above the focus of an earthquake http://www.harcourtschool.com/glossary/science/define/gr4/epicent er4c.html Seismograph measures or the strength of an earthquake Seismograph records energy waves of the earth Richter Scale Earthquake Magnitudes Less than 3.5 Effects Generally not felt 3.5-5.4 Rarely causes damage. Under 6.0 Slight damage to well-designed buildings. 6.1-6.9 Destructive to about 100 kilometers across 7.0-7.9 Major earthquake. Serious damage over larger areas. 8 or greater Great earthquake. Each number is 10X stronger than the previous number. How much stronger is the 3 than the 1? 100 Times How much stronger is the 8 than the 1? 10,000,000 Write the number in scientific notation. 106 Richter Magnitude 1.0 to 3.9 Number of Earthquakes per year 900,000 + 4.0-4.9 6200 5.0-5.9 800 6.0-6.9 226 7.0-7.9 18 8.0-8.9 Less than 2 Can you think of a recent earthquake? Haiti http://www.youtube.com/watch?v= 79S-6UqGCbU Earthquakes in the ocean cause 30’ Wall of Water Destruction