Lesson 6 (Pdf)
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U.S. Department of the Interior U.S. Geological Survey OLCANOES AND PEOPLE A .fig. I LESSON B Mount Rainier Snow-capped Mount Rainier rises behind Tacoma, Washington. Although Mount Rainier has not erupted in the past 500 years, scientists consider it one of the most hazardous volcanoes in the Cascade Range. Relative to other types of natural disas- more than a century had elapsed since a or even centuries. For example, one erup- ters, such as earthquakes, floods, hurri- major eruption; most people were not tive phase began in 1480 and lasted for canes, and tornados, volcanic eruptions aware of its dangers. Mount St. Helens is about 300 years. Based on that history, occur infrequently. Of the 1,500 active one of more than 65 active or potentially scientists anticipate that Mount St. volcanoes on land, approximately 50-60 active volcanoes in the continental Helens will continue to erupt episodically erupt each year. Approximately 1 million United States, Alaska, and Hawaii. Only for decades to come before it returns to a people have been killed by volcanic erup- Indonesia and Japan have more! dormant stage. tions during the past 2,000 years. Scientists of the U.S. Geological The eruption of Mount St. Helens Survey continue to monitor Mount St. served as a reminder that other dormant United States Has Many Active Volcanoes Helens and other volcanoes in the volcanoes can come to life again. Mount Because many of the most hazardous vol- Cascade Range. They know from its past Shasta in Northern California, for exam- canoes have not erupted during recent eruptive history that many of Mount St. ple, probably last erupted in 1786. On a historic times, people erroneously con- Helens' eruptions have occurred in con- geological time scale, this very recent sider them extinct. For Mount St. Helens, centrated periods of time lasting decades volcanic activity suggests that magma is Activity 1 61Gaimg a Legend fig. 2 45 minutes Cascade Eruptions Students create a legend that explains the existence of Mount St. Helens. Mount Baker Glacier Peak linjpinalt Key teaching points Mount Rainier 1. Mount St. Helens has been a fact of life for people living in its shadow ever Mount St. Helens *WI 100100111.14011 since humans began populating the Mount Adams Pacific Northwest more than 10,000 Mount Hood years ago. There have been dozens of Mount Jefferson eruptions during the past 4,500 years. Three Sisters Newberry Volcano 2. Before there were scientific explana- Crater Lake tions for why volcanoes erupted, people Mount McLoughlin developed stories to explain the presence Medicine Lake Volcano s Vit and behavior of volcanoes. Mount Shasta 14110,110 ISZIGAWG 3. The Yakima Indians called the vol- Lassen Peak IS NI cano "Tah-one-lat-clah" (Fire Mountain). 4,000 2,000 present years ago years ago The Cowlitz people called it "Lawetlatla" (Person from Whom Smoke Comes). Its Eruptions in the Cascades have occurred at an average rate of one to two per centu- modern name, Mount St. Helens, was ry during the last 4,000 years. Four of those eruptions would have caused consider- given to the volcano in 1792 by Captain able damage and loss of life if they had occurred today without warning. George Vancouver of the British Royal Navy. still present beneath the volcano. On canic hazards maps, this information is average, it has erupted once every 300 vital for communities in volcanically Materials years over the past 3,500 years. The active areas to use for land use and emer- None required. chance is 1 in 25 to 30 that it will erupt in gency preparedness planning. Knowing a any one decade and 1 in 3 or 4 within a volcano's past is crucial to forecasting its Procedures person's lifetime. future behavior. 1. Tell the legend below that was created by the Yakima people. (Before European Forecasting Future Eruptions Benefits Often Overlooked settlement in the 19th century, the Scientists have improved their ability to Because of the destructive nature of a Yakima people had considerable territory predict the time of a volcanic eruption, volcanic eruption, we tend to overlook a on the Yakima and Columbia Rivers in but estimating the size and style of an volcano's benefits. Magma circulates and Eastern Washington. Today, descendants eruption remains a difficult challenge. deposits many valuable elements, such as of these people live on the Yakima Indian Despite this challenge, scientists try to gold, silver, zinc, sulfur, and copper. Reservation in south-central assess the potential consequences of a Magma heats ground water systems that Washington.) future eruption by reconstructing a vol- can be tapped to produce geothermal cano's history, which includes the pat- power. This heated ground water can also Two tribes lived across the river from one tern, magnitude, and frequency of its past result in geysers and hot springs. another. Because they were.friendly and eruptions. The principal means of devel- Volcanoes are also responsible for some peaceful tribes, the Great Spirit built a oping this history is by mapping and dat- of the world's most fertile soils. And vol- bridge across the river for them. ing the different types of volcanic canoes continuously bring materials from Eventually, however the tribes began to materials that have been deposited by inside the Earth to the surface—recycling quarrel. The Great Spirit became angry. previous eruptions. Assembled into vol- on a grand scale. To punish the tribes he took away fire. The tribes prayed to the Great Spirit to return fire to them. Finally, the Great Spirit agreed. To restore fire, the Great Spirit had to go to an old woman named Loo-Wit who, because of her goodness, still had fire. Loo-Wit promised the Great Spirit that she would share her fire with the two tribes if the Great Spirit would Activity 2 Imre s a volcano in my Backyard! make her eternally young and beautiful. 45-minute work session 3. As a class, list the major eruptive Fire was restored, and the tribes were one followup project events (include avalanches, mudflows, peaceful for a short time. The chiefs of Using a volcanic hazard map of Mount and tephra falls) that occurred during the both of the tribes, however, fell in love Rainier, students reach conclusions about 1980 eruption of Mount St. Helens. with the beautiful Loo-Wit. The chiefs the potential hazards of future eruptions. began to quarrel and went to war. Once They then create educational materials 4. Using an overhead projector, show again, the Great Spirit became angry and about these hazards. students the eruptive history map of in retaliation he turned the two chiefs Mount Rainier (see Activity Sheet 6.2). into mountains. One became Mount Key teaching points Explain that scientists study past erup- Hood and one became Mount Adams. 1. Mount Rainier is located 35 kilome- tions to help them forecast future erup- Because Loo-Wit was so beautiful, the ters (21 miles) southeast of the Seattle- tions. Looking at this map, what type of Great Spirit made her into Mount St. Tacoma metropolitan area—an area that eruptive events have occurred ill the past. Helens—that Iray she could remain beau- has a population of 2.5 million. tiful forever 5. Distribute Activity Sheet 6.2. 2. Mount Rainier is an active volcano Tell students they will look at Mount 2. Students discuss how the legend dif- whose last major eruption was approxi- Rainier's history of volcanic mudflows fers from the way we now explain how mately 150 years ago. and forecast if there are any cities that volcanoes form. Are there similarities would be at risk during a future eruption. between the legend and scientific expla- 3. Mount Rainier has five times as much nations? snow and glacier ice as all the other 6. Discuss: What cities, if any, would be Cascades volcanoes combined. Mudflows at risk if there were a future eruption? Is 3. Ask students to imagine that they live are the most dangerous hazard. it possible, or practical, to eliminate all in a time and place where there are no risks to these cities? What things can he scientific explanations for why there is an 4. Throughout the volcano's history, done to reduce risks to life and property? active volcano near their community. there have been numerous mudflows. Conclude that public education is a major Students create and present orally a short Today, parts of Tacoma, Wash., and many activity. legend to explain why the volcano exists other smaller communities have been or erupts. built on top of these old flows—evidence Followup Project that they lie within the reach of future Students work individually or in teams to Extension mudflows that could originate from an develop a range of educational materials Do research from the journals of George eruption of Mount Rainier. and programs for the general public, Vancouver, John Fremont, and other especially school children. These might explorers to the Pacific Northwest to 5. An eruption of Mount Rainier could include posters; displays for schools, learn their descriptions of Mount St. kill hundreds of thousands of people and public libraries, and community centers; Helens and other volcanoes in the cripple the region's economy. brochures; public service announcements Cascade Range. Using these accounts as on TV and radio; and information on the a basis, students create their own diary Materials Internet. entries. Activity Sheet 6.2 Procedures Work Session 1. Review with students that Mount St. Helens is one of a number of active vol- canoes in the Cascade Range. Some oth- ers include: Mount Baker, Mount Rainier, and Mount Adams in Washington; Mount Hood, Mount Jefferson, and Crater Lake Osceola Mudflow in Oregon; and Mount Shasta and Lassen 2.