Understanding Magma: Viscosity, Types, and Volcano Eruptions

Chpt 5 Lab Activity 5.1 page 79 question 1, 2, 3, 4, 5, 6, 7, 8 1. Define magma. Molten Rock beneath Earth’s surface 2. List these magmas in order from the lowest to highest silica content: basaltic (mafic), rhyolitic (felsic), and andesitic (intermediate). A. Basaltic (Mafic) B. Andesitic (Intermediate) C. Rhyolitic (Felsic) 3. Based on their silica content, which of these magmas is the most viscous? Least viscous? Most viscous: Rhyolitic Least viscous: Basaltic 4. Which of these magmas tend to produce effusive (quiescent) eruptions? Basaltic 5. Which of these magmas produce the most explosive eruptions? Andesitic magmas. 6. What two types of volcanoes are associated with eruptions of fluid basaltic lavas? Shield volcanoes and cinder Cone volcanoes 7. With what type of volcano are andesitic (intermediate) magmas most associated?

Composite volcanoes 8. Fill in each blank with the number of the image that illustrates each of the following volcano-related phenomena.

a. Lava fountain 3 b. Fluid lava flow 2

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c. Volcanic dome 5 d. Pyroclastic material (tephra) 4 e. Eruption column 1 f. Silica-rich lava flow 6 Activity 5.2 page 80-81 question 2, 3, 4, 5, 6 2. What factor contributes to the gentle slope’s characteristic of shield volcanoes? low lava viscosity 3. What are the small “hills” covered in vegetation in the foreground of this image? (Hint: See Figure 5.5.) Lava Flow 4. Figure 5.4 is an image of an eruption on Kilauea, a small shield volcano located on the flanks of Mauna Loa. Would you describe the lava as having a low or high viscosity? Explain your reasoning. Low viscosity, it low silica and gas concentration but a high temperature. 5. Does the lava shown in Figure 5.4 most likely have a low or high silica content? Low Silica 6. Based on your answer to Question 5, what is the likely composition of the magma that formed Kilauea? Basaltic form of magma, low viscosity and it has the least concentration of gas but the greatest temperature.

Activity 5.3. page 82 question 1, 2, 3, 4, 5, 6, 7, 8, 9 1. Using a protractor, measure the slope of SP Crater. (Note: Use the dashed horizontal line to align the bottom of your protractor.) 30 degrees ° 2. How does the slope of SP Crater compare to the slope you determined for Mauna Loa in Activity 5.2? The difference is huge. The slope in the crater is higher. 3. Using the scale, measure the height of SP Crater from its base to the crater rim, indicated with an arrow. Round your answer to the nearest 100 feet. 1200 ft 4. Based on your answer to Question 3, compare the size of a cinder cone to the size of a shield volcano. Cinder Cones are smaller, Shields can go to 2000 ft

5. Based on Figure 5.5, compare the size of the crater of a typical cinder cone to the overall size of the volcano. Compared to it its tiny, a crater can be over 1000 meters 6. What is the name for the ejected lava fragments that include pea- to walnut-sized pieces? Scoria 7. Given the nature of the materials that make up a cinder cone and the steepness of its slopes, describe what it would be like to climb from the base to the rim. Very difficult- too steep and the looseness of the rock. 8. Using Figure 5.7 and a piece of string, measure the length of the flow from SP Crater by following the curve along the center of the flow. 11.8 km Figure 5.7Satellite view of SP Crater to accompany Questions 8 and 9. (NASA) 9. Would you describe the lava that produced this flow as fluid or viscous? Explain. Viscous, it looks think and extends for a long way. Activity 5.4 page 83 question 1, 2, 3 1. Would you describe this as an effusive or explosive eruption? Explain your reasoning.

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explosive eruption- higher magma viscosity, higher pressure. With pyroclastic material. 2. What name is given to the plume rising from the volcano? Eruption Plume 3. List the primary materials that compose the Mount St. Helens plume. volcanic ash, pumice, and gas

Activity 5.5 A. page 86-87 question 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 1. Based on the image in Figure 5.11, what type of volcano is Mount Rainier? Strato-volcano 2. This image also shows that the upper portion of Mount Rainier is covered with snow and glacial ice. How might this snow and ice contribute to future volcanic hazards? Lahars are predominant. When the Coldwater mixes with the hot rock, it turns into something like concrete. Which is thick and flows quickly. 3. What term is used for mudflows that form on volcanoes? Lahars and debris flow 4. Can mudflows be triggered when a volcano is not erupting? Explain. Yes, with loose volcanic debris, a torrential downpour can cause the debris to get loose and start to pour down the hillsides 5. Notice in Figure 5.12 that the Osceola Lahar was confined mainly to river valleys until it reached the Puget Lowland, where it began to spread out. What was the probable cause of this change? Lahars usually flow with or where Rivers and streams flow. It gives it a directional way to flow

6. Using a string, measure the distance on Figure 5.12 from the top of Mount Rainier to the city of Kent, Washington, carefully following the easternmost path of the lahar. (Note: See the North arrow.) What is the maximum distance traveled by the Osceola Lahar? 70 km 7. Assuming that the Osceola Lahar traveled at an average speed of 30 kilometers (20 miles) per hour, how long would it have taken to travel from Mount Rainier to the town of Kent? Use your answer to Question 6 as the distance traveled. About 2.5 hrs 8. If monitoring stations were established around the base of Mount Rainier to send out a warning whenever a lahar is triggered, do you think that effort would have the potential to help save lives? Explain. Yes, because it is real time data and can help protect lives with the warnings 9. What material would be incorporated into a lahar that would allow scientists to date a prehistoric mudflow using carbon-14 dating? (See the section “Dating with Carbon-14” in Chapter 11 of your textbook, if needed.) its made up of volcanic rocks and ash and water once the water evaporates. And hardens. Lahars are newly formed produced volcanic rocks along with other elements. It may be used to “carbon date”. 10. What value is gained from dating prehistoric occurrences of lahars? It can determine the age or year of a prehistoric event(s).

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Activity 5.5. B. page 88-89 question 1, 2, 3, 4, 5, 6, 7, 8 1. What name is given to fast-moving currents of hot gases and volcanic material that move at very high speeds down the flanks of volcanoes? A pyroclastic flow

2. The average chemical composition of the ash from the Mount St. Helens eruption included about 65 percent silica. Describe where the magma that produced this eruption would fit within the range of compositions shown on the chart in Figure 5.1. It would be andesitic. 3. Did the magma that produced the May 18, 1980, eruption of Mount St. Helens have a relatively low or high silica content? Explain. 4. Use Figure 5.16, which shows the area destroyed by the lateral blast, to measure the distance from the center of Mount St. Helens to the farthest point that the blast reached, indicated by the letter A. (Note: It is estimated that it took the lateral blast less than 2 minutes to reach this location.) 30 km, 30,000 m 5. Use Figure 5.14 to determine how much volcanic ash blanketed the town of Ritzville, Washington. Between 2 to 5 inches 6. What is the furthest state from the volcano that received a measurable amount of volcanic ash during the Mount St. Helens eruption? (Use the distance scale if needed.) Oklahoma (self-note- I was a little kid I lived in Colorado and I woke up that morning and there was ash all over my dad’s car I Never forget that!) 7. In what general direction were the upper-level winds blowing during the eruption?

East 8. Which of the three types of volcanoes discussed pose the greatest threat to property and human life? A Composite volcano. Lab Report page 91-92 questions 1-16 all parts 1. Define magma . Molten rock underneath the earth surface. 2. What type of magma has the lowest silica content? Highest silica content? Lowest: Rhyolitic Highest: Basaltic 3. What type of magma has the lowest viscosity? Highest viscosity? Lowest: Basaltic Highest: Rhyolitic 4. Does the lava flow shown in Figure 5.17 have a high or low viscosity? Low Viscosity 5. What name is given to the nongaseous material ejected into the air by a volcanic eruption? Volcanic Ash 6. Which type of magma tends to produce effusive (quiescent) eruptions?

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Basaltic Magma 7. Which type of magma tends to produce lava domes? Rhyolitic magma 8. What two types of volcanoes are associated with eruptions of fluid basaltic lavas? Shield volcanoes, Cinder cone volcanoes 9. Describe the basic shape of a shield volcano. Shield volcano's structure is made up of lava flows. streams out in all directions. Like a warriors shield. 10. What type of volcano is shown in Figure 5.18? A Cinder Cone 11. What name is applied to the material being mined from the volcano shown in Figure 5.18? Iron, magnesium and calcium 12. Describe how the shape (slope) of a composite volcano changes from its base to its top. Steep slopes 13. What type of volcanos are Earth’s largest? Shield volcanos

14. What hazard does Mount Rainier pose to the Seattle–Tacoma metropolitan area? Due to the snow and the glacial ice a massive Lahar volcano is a major threat. 15. Figure 5.19 shows a profile view of Newberry Volcano as seen from Pilot Butte in Bend, Oregon. Based on its profile, shown with a blue line, what type of volcano is Newberry Volcano? a shield volcano 16. What are the small structures that are visible on the lower flanks of Newberry Volcano in Hills, from Cinder Cones.

Chpt 5 Lab

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