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What's the Difference? New Zealand American Submarine Ring of Fire 2007 What’s The Difference? FOCUS SEATING ARRANGEMENT Volcanic processes at convergent and divergent Classroom style if students are working individu- tectonic plate boundaries ally, or groups of two to four students GRADE LEVEL MAXIMUM NUMBER OF STUDENTS 9-12 (Earth Science) 30 FOCUS QUESTION KEY WORDS How do volcanic processes differ at convergent Volcano and divergent tectonic plate boundaries? Caldera Hot spot LEARNING OBJECTIVES Ring of Fire Students will be able to compare and contrast Asthenosphere volcanoes at convergent and divergent plate Lithosphere boundaries. Magma Fault Students will be able to identify three geologic Transform boundary features that are associated with most volcanoes Convergent boundary on Earth. Divergent boundary Subduction Students will be able to explain why some volca- Tectonic plate noes erupt explosively while others do not. BACKGROUND INFORMATION MATERIALS The Submarine Ring of Fire is an arc of active vol- Copies of “Submarine Volcanism Worksheet,” canoes that partially encircles the Pacific Ocean one copy for each student or student group Basin, including the Kermadec and Mariana Islands in the western Pacific, the Aleutian Islands AUDIO/VISUAL MATERIALS between the Pacific and Bering Sea, the Cascade (Optional) Computer projection equipment to Mountains in western North America, and numer- show downloaded video materials ous volcanoes on the western coasts of Central America and South America. These volcanoes TEACHING TIME result from the motion of large pieces of the One or two 45-minute class periods, plus time for Earth’s crust known as tectonic plates. student research 1 New Zealand American Submarine Ring of Fire 2007 – Grades 9-12 (Earth Science) Focus: Volcanic processes at convergent and divergent tectonic plate boundaries oceanexplorer.noaa.gov Tectonic plates are of portions of the Earth’s outer The third type of plate boundary occurs where crust (the lithosphere) about 5 km thick, as well as tectonic plates slide horizontally past each other, the upper 60 - 75 km of the underlying mantle. and is known as a transform plate boundary. As The plates move on a hot flowing mantle layer the plates rub against each other, huge stresses called the asthenosphere, which is several hundred are set up that can cause portions of the rock kilometers thick. Heat within the asthenosphere cre- to break, resulting in earthquakes. Places where ates convection currents (similar to the currents that these breaks occur are called faults. A well-known can be seen if food coloring is added to a heated example of a transform plate boundary is the San container of water). These convection currents Andreas fault in California. See animations of cause the tectonic plates to move several centime- different types of plate boundaries at: http://www. ters per year relative to each other. seed.slb.com/en/scictr/watch/living_planet/plate_boundaries/ plate_move.htm. The junction of two tectonic plates is called a “plate boundary.” Three major types of plate The volcanoes of the Submarine Ring of Fire result boundaries are produced by tectonic plate move- from the motion of several major tectonic plates. ments. If two tectonic plates collide more or less The Pacific Ocean Basin lies on top of the Pacific head-on they form a convergent plate boundary. Plate. To the east, along the East Pacific Rise, new Usually, one of the converging plates will move crust is formed at the oceanic spreading center beneath the other, which is known as subduction. between the Pacific Plate and the western side Deep trenches are often formed where tectonic of the Nazca Plate. Farther to the east, the east- plates are being subducted, and earthquakes are ern side of the Nazca Plate is being subducted common. As the sinking plate moves deeper into beneath the South American Plate, giving rise to the mantle, fluids are released from the rock caus- active volcanoes in the Andes. Similarly, conver- ing the overlying mantle to partially melt. The new gence of the Cocos and Caribbean Plates pro- magma (molten rock) rises and may erupt violent- duces active volcanoes on the western coast of ly to form volcanoes, often forming arcs of islands Central America, and convergence of the North along the convergent boundary. These island arcs American and Juan de Fuca Plates causes the vol- are always landward of the neighboring trenches. canoes of the Cascades in the Pacific Northwest. For a 3-dimensional view of a subduction zone, visit: http://oceanexplorer.noaa.gov/explorations/03fire/logs/sub- On the western side of the Pacific Ocean, the duction.html. Pacific Plate converges against the Philippine Plate and Australian Plate. Subduction of the The junction of two tectonic plates that are mov- Pacific Plate creates the Mariana Trench (which ing apart is called a divergent plate boundary. includes the Challenger Deep, the deepest known Magma rises from deep within the Earth and area of the Earth’s ocean) and the Kermadec erupts to form new crust on the lithosphere. Trench. As the sinking plate moves deeper into Most divergent plate boundaries are underwater the mantle, new magma is formed as described (Iceland is an exception), and form submarine above, and erupts along the convergent bound- mountain ranges called oceanic spreading ary to form volcanoes. The Mariana and ridges. While the process is volcanic, volcanoes Kermadec Islands are the result of this volcanic and earthquakes along oceanic spreading ridges activity, which frequently causes earthquakes as are not as violent as they are at convergent plate well. The movement of the Pacific Ocean tectonic boundaries. View the 3-dimensional structure of plate has been likened to a huge conveyor belt a mid-ocean ridge at: http://oceanexplorer.noaa.gov/ on which new crust is formed at the oceanic explorations/03fire/logs/ridge.html. spreading ridges, and older crust is recycled to 2 New Zealand American Submarine Ring of Fire 2007 – Grades 9-12 (Earth Science) oceanexplorer.noaa.gov Focus: Volcanic processes at convergent and divergent tectonic plate boundaries the lower mantle at the convergent plate bound- and the Submarine Ring of Fire 2004 back- aries of the western Pacific. For more informa- ground essay, “Submarine Volcanism 2004” tion on plate tectonics, visit the NOAA Learning (http://oceanexplorer.noaa.gov/explorations/04fire/background/ Objects Web site (http://www.learningdemo.com/noaa/). volcanism/volcanism.html). If students do not have Click on the links to Lessons 1, 2 and 4 for inter- internet access, you will also need to download active multimedia presentations and Learning diagrams of the structure of mid-ocean ridges Activities on Plate Tectonics, Mid-Ocean Ridges, and subduction zones (http://oceanexplorer.noaa.gov/ and Subduction Zones. See the satellite and sonar explorations/03fire/logs/ridge.html and http://oceanexplorer. survey animation of the Mariana Arc Volcanic noaa.gov/explorations/03fire/logs/subduction.html), as well Chain at: http://oceanexplorer.noaa.gov/explorations/04fire/ as reference materials cited on the “Submarine background/marianaarc/media/sat_em_islands_video.html. Volcanism Worksheet.” You may also want to visit the Magic Mountain Web pages (http:// Beginning in 2002, Ocean Exploration expe- oceanexplorer.noaa.gov/explorations/02fire/logs/magicmoun- ditions have undertaken systematic mapping tain/welcome.html) to see the “landscape” around and study in previously-unexplored areas of the an active hydrothermal site, and/or view first- Submarine Ring of Fire. Visit ever footage of a submarine volcano in the act • http://oceanexplorer.noaa.gov/explorations/02fire/logs/ of erupting live red lava: http://www.oceanexplorer. magicmountain/; noaa.gov/explorations/06fire/logs/april29/april29.html. • http://www.oceanexplorer.noaa.gov/explorations/03fire/; • http://www.oceanexplorer.noaa.gov/explorations/04fire/; 2. Briefly review the concepts of plate tectonics • http://www.oceanexplorer.noaa.gov/explorations/05fire/; and continental drift, and introduce the New and Zealand American Submarine Ring of Fire • http://oceanexplorer.noaa.gov/explorations/06fire/welcome. 2007 Expedition. Be sure students understand html the distinction between mid-ocean ridges and for more information about the many discover- subduction zones. You may want to show stu- ies, as well as still and video imagery, from dents the streaming video lessons available in these expeditions. The New Zealand American Lessons #1, 2, and 4 on the following NOAA Submarine Ring of Fire 2007 Expedition is Learning Object site: http://www.learningdemo.com/ focused on detailed exploration of hydrothermal noaa/. systems at Brothers Volcano in the Kermadec Arc, an area where tectonic plates are converging 3. Provide each student or student group with a more rapidly than any other subduction zone in copy of the “Submarine Volcanism Worksheet,” the world. and have students answer the worksheet ques- tions. In this lesson, students will investigate the char- acteristics of volcanoes at mid-ocean ridges 4. Lead a discussion of students’ responses and convergent plate boundaries, and make to questions on the worksheet. The correct inferences to account for observed differences responses are: between volcanoes at these locations. (1) What are three geologic features that LEARNING PROCEDURE account for most volcanoes on Earth? 1. To prepare for this lesson, review the introduc- Oceanic spreading centers at divergent tory essays for the New Zealand American
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