Transcript Document
Earth Shakes, Rattles, and Rolls Plate Tectonics Volcanoes 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. 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 How did geologists explain how the earth’s plates moved? Mid-Atlantic Ridge allows mantle to seep to surface through cracks and pushes plates of the earth apart. To see how geologists believe the plates moved go to the site below. Notice the Atlantic Ocean seafloor spreading. Seafloor spreading animation •Crust •Mantle •Outer core •Inner core Types of Mountains • Folded • Fault-block • Volcanic • Unwarped FOLDED MOUNTAINS http://www.cssd11.k12.co.us/dohnts/images/earth/fldmtn.jpg FOLDED MOUNTAINS •Appalachian Mountains in the eastern United States, and the Swiss Alps in Switzerland •form when two plates collide head on, and their edges crumble •consist mainly of sedimentary rocks, like limestone and shale FAULT-BLOCK MOUNTAINS FAULT-BLOCK MOUNTAINS •Consist of huge blocks of the earth's crust that have been tilted or pushed up along a fracture line called a fault •Sierra in California, Arizona is an example. • Created when a plate hits a fault and tips upside down, creating erosion and debris, which is at the base of the mountain. VOLCANIC MOUNTAIN NAMIBIA IN AFRICA Volcanic mountains •Formed when molten rock, or magma deep within the earth, erupts, and piles upon the surface •Made of basalt and rhyolite. •Takes place where two of the earth's tectonic plates collide. UNWARPED MOUNTAINS •Black Hills in South Dakota •form when tectonic forces lift the earth's crust into a broad bulge or dome raising it above its surroundings •Erosion causes peaks and valleys to form. 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 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. Convection currents in the magma move the earth’s crust. 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 http://uc.wisc.edu/news/features/quake/pwaves.html Go to this site to see an animation of the path of p waves and s waves http://www.pbs.org/wnet/savageearth/animations/earthquakes/ Earthquakes How do we measure the intensity of an earthquake? Seismograph measures or the strength of an earthquake Seismograph records energy waves of the earth Mercalli Scale I.People do not feel anything . V. •People feel movement. •Doors open •Pictures fall off wall. VII. •Some buildings lose bricks. •Difficulty driving. IX. Considerable damage to homes. Cracks in earth. XII. •Almost everything is destroyed. • The ground moves in waves or ripples. 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 Why is the Richter Scale more accurate than the Mercalli Scale? •The Richter Scale is objective and based on mathematical measurements. •The Mercalli scale is subjective and based on people’s perception and experience. •On Mercalli scale if the area is unihabited there is no way to measure the magnitude of the earthquake. 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 One Boy’s Experience – Eyewitness Account http://www.olympus.net/personal/gofamily/quake/famous/1906.html Jack London’s Eyewitness Account of San Franciso Earthquake http://sunsite.berkeley.edu/London/Writings/Journalism/sfearthquake.html Click on url to get complete texts San Francisco Earthquake 1906 Alaska Earthquake 1964 Earthquakes in the ocean cause 30’ Wall of Water Destruction Types of Volcanos • Composite • Cinder Cone • Shield •Vesuvius, Krakatoa, Fujiyama, and Mount St. Helens •tens of miles across and ten thousand or more feet in height. •have small craters in their summits http://images.google.com/imgres?imgurl=http://www.cotf.edu/ete/images/modules/volcanoes/typesb.GIF&imgrefurl=http://www.cotf.edu/ete/modules/volcano es/vtypesvolcan1.html&h=236&w=265&sz=14&tbnid=qZF0vXnHnOkJ:&tbnh=96&tbnw=107&start=19&prev=/images%3Fq%3Dcomposite%2Bvolcano%2 6hl%3Den%26lr%3D%26sa%3DN •consist almost entirely of loose, grainy cinders and almost no lava •small volcanoes •steep sides and usually have ahttp://images.google.com/imgres?imgurl=http://www.cotf.edu/ete/images/modules/volcanoes/t ypesb.GIF&imgrefurl=http://www.cotf.edu/ete/modules/volcanoes/vtypesvolcan1.html&h=23 6&w=265&sz=14&tbnid=qZF0vXnHnOkJ:&tbnh=96&tbnw=107&start=19&prev=/images% 3Fq%3Dcomposite%2Bvolcano%26hl%3Den%26lr%3D%26sa%3DN small crater on top •hundreds of miles across and many tens of thousands of feet high. •Mauna Loa •consist almost entirely of frozen lavas •large craters at their summits. http://images.google.com/imgres?imgurl=http://www.cotf.edu/ete/images/modules/volcanoes/typesb.GIF&imgrefurl=http://www.cotf.edu/ete/modules/volcanoes/vtypesv olcan1.html&h=236&w=265&sz=14&tbnid=qZF0vXnHnOkJ:&tbnh=96&tbnw=107&start=19&prev=/images%3Fq%3Dcomposite%2Bvolcano%26hl%3Den%26lr%3 D%26sa%3DN • largest single mountain in the world •30,000 +feet above the ocean floor • 100 miles across at its base. Image Resources For additional diagrams of volcanoes click below: http://www.enchantedlearning.com/subjects/volcano/labelvolc ano.shtml http://images.google.com/imgres?imgurl=http://www.cotf.edu/ete/images/modules/volcanoes/typesb.GIF&imgrefur l=http://www.cotf.edu/ete/modules/volcanoes/vtypesvolcan1.html&h=236&w=265&sz=14&tbnid=qZF0vXnHnOk J:&tbnh=96&tbnw=107&start=19&prev=/images%3Fq%3Dcomposite%2Bvolcano%26hl%3Den%26lr%3D%26sa %3DN