Dynamic Earth Volcano Lab - Google EarthTm Name: ___________________ Goal: To be able to describe and identify the common volcano types, and relate volcano types with associated volcanic hazards, tectonic setting, and geographic location. Volcano shape is strongly controlled by eruptive style, which in turn is controlled by magma composition and tectonic setting. This lab is intended to give you the opportunity to examine volcanoes from around the globe, and to interpret the tectonic settings in which they form. To learn more about volcanoes, check out the following websites: the Smithsonian Institution Global Volcanism Program: http://volcano.si.edu/, Volcano World: http://volcano.oregonstate.edu/; USGS Volcanic Hazards Program http://volcanoes.usgs.gov/. Volcanoes! 1. Navigate to Chile, in South America (you can go directly there by typing in the coordinates in the search bar at the upper left side of the screen -33.25, -70.35). Center the image so that the capital, Santiago, is in your screen at an eye altitude of ~1000 km (the names of the capitols will appear as you zoom in). Make sure that north is at the top of the image. 2. Tilt the image so that you can look northward along the South American coast. Briefly describe the major tectonic features (landforms) that you see. 3. Now navigate to Descabeza (you can go directly there by typing in the coordinates in the search bar at the upper left side of the screen -35.58, -70.75). a) Describe the size and shape of the volcano by filling in the spaces, below: Maximum height (elevation) of the volcano above sealevel: ___________________________ meters. Base elevation of the volcano: _____________________________ meters. Relief (maximum elevation – base elevation) = _____________________meters total height. Base width: _____________________ meters. Average slope of volcano ((relief ÷ ½width)*100%):_______ b) Sketch and describe the overall shape of Descabeza. c) Describe the likely composition (mafic, intermediate, felsic) of this volcano, based on your observations. Explain your answer. d) Describe the major geologic hazards associated with this volcano. What do the deposits look like for each hazard, and what specific areas of the landscape are most impacted by each hazard? 1 e) Zoom out and examine the region. Describe the likely tectonic setting of the volcanoes of the Andes mountains (crust types and relative motion). Hint: is there a deep ocean trench to the west of the mountains? f) After the lecture on volcanoes, speculate on the volcano type, based on size, shape, and composition. 4. Navigate to Mt. St. Helens (46.1958, - 122.1821) in southern Washington, USA. a) Maximum height (elevation) of the volcano above sea level: ___________________________ meters. Base elevation of the volcano: _____________________________ meters. Relief (maximum – base elevation) = _____________________meters total height. Base width: _____________________ meters. Average slope of volcano ((relief ÷ ½width)*100%):_____ b) Sketch and describe the overall shape of Mt. St. Helens: c) Describe the likely composition of this volcano, based on your observations. Explain your answer. d) Describe the major geologic hazards associated with this volcano. What do the deposits look like for each hazard, and what specific areas of the landscape are most impacted by each hazard? e) Zoom out and examine the region. Are there any other volcanoes nearby? Describe the likely tectonic setting of the volcanoes of the Cascade Range. Support your answer with observations on the major tectonic landforms of the region. f) After the lecture on volcanoes, speculate on the volcano type, based on size, shape, and composition. 2 5. Navigate to Mauna Loa on the BIG island of Hawaii (central Pacific Ocean) (19.4715, -155.59039). a) Maximum height (elevation) of the volcano: ___________________________ meters above sea level. Base elevation of the volcano: _____________________________ meters above sea level. Relief (maximum – base elevation) = _____________________meters, total height. Base width: _____________________ meters. Average slope of volcano ((relief ÷ ½width)*100%):_____ b) Sketch and describe the overall shape of Mauna Loa. c) Describe the likely composition of this volcano, based on your observations. Explain your answer. d) Describe the major geologic hazards associated with this volcano. What do the deposits look like for each hazard, and what specific areas of the landscape are most impacted? e) Zoom out and examine the region. Describe the likely tectonic setting of the Hawaiian Islands. (Hint: think back to your tectonic homework). Support your answer with observations on the major tectonic landforms of the region. f) After the lecture on volcanoes, speculate on the volcano type, based on size, shape, and composition. 3 6. Navigate to Mt. Fujiyama, Japan (35.364, 138.731). a) Maximum height (elevation) of the volcano above sealevel :___________________________ meters. Base elevation of the volcano: _____________________________ meters. Relief (maximum – base elevation) = _____________________meters total height. Base width: ________________ meters. Average slope of volcano ((relief ÷½width)*100%) = ________ b) Sketch and describe the overall shape of Mt. Fujiyama: c) Describe the likely composition of this volcano, based on your observations. Explain your answer. d) Describe the major geologic hazards associated with this volcano. What do the deposits look like for each hazard, and what specific areas of the landscape are most impacted? How do the volcanic risks here compare with those around Mt. St. Helens? Begin by defining volcanic risk, then compare the two locations. e) Zoom out and examine the region. Describe the likely tectonic setting of the volcanoes in Japanese region. Support your answer with observations on the major tectonic landforms of the region. f) After the lecture on volcanoes, speculate on the volcano type, based on size, shape, and composition. 4 7. Navigate to Mt. Alayta, Ethiopia (12.887, 40.573). a) Maximum height (elevation) of the volcano above sea evel :___________________________ meters. Base elevation of the volcano: _____________________________ meters. Relief (maximum – base elevation) = _____________________meters total height. Base width: _________________ meters. Average slope of volcano ((relief ÷ ½width)*100%):_________ b) Sketch and describe the overall shape of Mt. Alayta: c) Describe the likely composition of this volcano, based on your observations. Explain your answer. d) Describe the major geologic hazards associated with this volcano. What do the deposits look like for each hazard, and what specific areas of the landscape are most impacted? e) Zoom out and examine the region. Describe the likely tectonic setting of the volcanoes in the region (crust type and motion). Support your answer with observations on the major tectonic landforms of the region. f) After the lecture on volcanoes, speculate on the volcano type, based on size, shape, and composition. 5 8. Navigate to Aniakchack, Alaska (56.901, -158.142). a) Maximum height (elevation) of the volcano above sea level :___________________________ meters. Base elevation of the volcano: _____________________________ meters. Relief (maximum – base elevation) = _____________________meters total height. Base width: ________________ meters. Average slope of volcano ((relief ÷ ½width)*100%):_________ b) Sketch and describe the overall shape of Aniakchack: c) Describe the likely composition of this volcano, based on your observations. Explain your answer. d) Describe the major geologic hazards associated with this volcano. What do the deposits look like for each hazard, and what specific areas of the landscape are most impacted? e) Zoom out and examine the region. Describe the likely tectonic setting of the volcanoes in the region (crust type and motion). Support your answer with observations on the major tectonic landforms of the region. f) After the lecture on volcanoes, speculate on the volcano type, based on size, shape, and composition. 6 9. Plot your measured values for the volcanoes examined in this lab, on the graphs below. Width (km) 200 180 160 140 120 100 80 60 40 20 0 Descabeza Mt. St. Helens Mt. Fuji Mauna Loa Mt. Alayta Aniakchack Relief (m) 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0 Descabeza Mt. St. Helens Mt. Fuji Mauna Loa Mt. Alayta Aniakchack 7 Slope (%) 50 45 40 35 30 25 20 15 10 5 0 Descabeza Mt. St. Helens Mt. Fuji Mauna Loa Mt. Alayta Aniakchack Felsic Intermediate Mafic Composition 0 Descabeza Mt. St. Helens Mt. Fuji Mauna Loa Mt. Alayta Aniakchack 8 Summarize volcano type/composition relationships. Go back to your answer for question ‘f’ for each volcano examined in lab, and make sure you have a good answer! Then use your observations and interpretations to complete the following statements and questions. Use Tables 1-3, on the next page, for appropriate terms. ➢ Shield volcanoes usually have a_____________ shape, _________slope, and a _____________composition. The most common hazard(s) are: ➢ Shield volcanoes commonly form in these tectonic settings: Explain your answer (relate volcano type to magma composition – where does the magma come from?) ➢ Composite volcanoes usually have a_____________ shape, _________slope, and a ___________composition. The most common hazard(s) are: ➢ The most common tectonic setting of composite volcanoes is at: ___________________boundaries. Explain your answer (relate volcano type to magma composition – where does the magma come from?) ➢ Caldera volcanoes usually have a_____________ shape, _________slope, and a _____________composition. The most common hazard(s) are: ➢ Caldera volcanoes commonly form in these tectonic settings: Explain your answer (relate volcano type to magma composition – where does the magma come from?) 9 Table 1 Shapes Wide dome Steep cone Open crater with raised rim Table 2 Slopes Low (0 – 10 %) Moderate (11 – 20%) Steep (>20%) Table 3 Composition Mafic Intermediate - Felsic Felsic 10 Volcanoes Factors determining the “violence” or explosiveness of a volcanic eruption • Composition of the magma • Temperature of the magma • Dissolved gases in the magma • The above three factors control the viscosity of a given magma, which in turn controls the nature of an eruption Viscosity • Viscosity is a measure of a material’s resistance to flow (e.g., higher viscosity materials flow with greater difficulty) • Factors affecting viscosity • Temperature – hotter magmas are less viscous • Composition – silica (SiO2) content Higher silica content = higher viscosity (e.g., felsic lava such as rhyolite) • Amount of dissolved gasses (don’t worry about why) Viscosity and Magma • Fluid basaltic lavas generally produce quiet eruptions • Highly viscous lavas (rhyolite or andesite) produce more explosive eruptions Materials Extruded During and Eruption • Lava flows • Dissolved gasses • Pyroclastic material Lava flows • Basaltic lavas are much more fluid and produce • Pahoehoe lava (resembles a twisted or ropey texture) • Aa lava (rough, jagged blocky texture) Pillow Lava Figure 16.18 Dissolved Gases most abundant “stuff ” that’s erupted • One to six percent of a magma by weight • Mainly water vapor and carbon dioxide Pyroclastic Materials • “Fire fragments” • Ash and dust – fine, glassy fragments • Pumice – porous rock from “frothy” lava • Lapilli – walnut-sized material • Cinders – pea-sized material • Blocks – hardened or cooled lava • Bombs – ejected as hot lava General features of volcanoes • Crater or Caldera – steep-walled depression at the summit (crater is >1 km, caldera