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Volcanoes-Activity Sheet 90 points As always, I t’s all about relationships. As you prepare for exam-2, review the content below and formulate relationships between types of volcanoes, volcanic processes, types of lava flows and volcanic hazards. In many cases, don’t memorize, but explain in your own words and develop a picture in your mind regarding volcanic concepts using the proper terminology. Please make sure you take a look at the probable exam essay questions at the end of this activity sheet. It’s recommended that you view the plate tectonic lecture in its entirety before answering questions. Define the following volcano terminology: Viscosity- - How well a material flows volcanic bombs- Emanate right from the opening of the caldera part of the volcano Crater- pyroclastic flow- . A dense destructive mass of very hot ash, lava fragments, and gases ejected explosively from a volcano and typically flowing downslope at great speed Volatiles- Components of magma that are dissolved until it reaches the surface Nuee-Ardente- travel 200 mph, ash cloud filled with volatiles Vent- Pahoehoe lava- V ery fluid like lava Lahars- (mud flows) one has to envision in a felsic volcano, as the magma rises to the top of the volcano it starts to heat the surrounding snow. shield volcano- a broad domed volcano with gently sloping sides, characteristic of the eruption of fluid, basaltic lava volcanic pipe (diatreme)- diatreme is a general term used to describe a volcanic vent or pipe that formed Aa lava: Thick lava that comes out the volcano slowly volcanic flank- Sides of the volcano composite volcano- Stratovolcano that is a conical volcano built up by man layers parasitic cone- Cone shaped accumulation of volcanic material Ash- volcanic conduit- pipe of the volcano that allows magma to move up from the magma chamber through the conduit cinder cone - cone formed around a volcanic vent by fragments of lava thrown out during eruptions Dike- the magma is cutting across the layers Sill- a type of igneous rock feature that is parallel to an overlying rock material Laccolith - a mass of igneous rock, typically lens-shaped, that has been intruded between a rock Batholith - a very large igneous intrusion extending deep in the earth’s crust stock- . 1. Mt. St. Helens is the only volcano that has erupted in the Continental US within the last 100 years. Relationship Question: a. Draw a map showing California, Oregon and Washington State and show the geographical location of Mt. St.Helens b. Which mountain range is Mt. St. Helens part of? Cascade Range

2. Types of volcanic lava eruptions, type of volcano and if the volcano is either explosive or non-explosive is all about VISCOSITY Relationship Questions: a. In your own words, describe a liquid that has viscosity -- What is viscosity? i. How well material flows b. Describe at least 3 types of liquids with high viscosity and 3 types of liquids having low viscosities that you have interacted with over your lifetime i. Glass, Molasses, jelly c. How can you change the high viscosity of chocolate sauce to low viscosity? i. By heating it up Why does heating up a liquid change most liquids to a lower viscosity heat melts some particles of the liquid and makes it less thick a. What happens to oil viscosity in a car as the engine heats to operation temperature? i. Oil becomes more fluid b. Do molasses and peanut butter have viscosity? (explain) i. Yes they are really thick c. Does glass have viscosity? (explain) 3. Factors influencing the volcanic eruption and type of volcano Relationship Questions: Using terms High or Low viscosity, High or Low temperature, low or high silica, volatiles, explosive, fluid, and Low or High viscosity, fill in the blanks to make the statements below correct. a. A mafic lava flow creates a fluid flow that is concentrated with l ow Silica and forms Nonexplosive types of lava flows b. A felsic lava flow creates a Pasty flow that is concentrated with High silica and forms an explosive type of lava flows. c. High silica content in a felsic type volcano inhibits the movement of High silica creating An explosive of volcanic eruption. d. Low silica content in a mafic type volcano allows free movement of Low viscosity creating a nonexplosive volcanic eruption e. Viscosity is controlled with temperature. High temperature creates Explosive eruptions and volatiles and lower temperatures creates Nonexplosive . 4. Typically, volcanoes will emit a combination of volatile compositions. Relationship Questions: a. List in order of highest to lowest percentage of gas concentrations emitted by a typical volcanic eruption Water/ vapor 70% Carbon dioxide 15% Sulfur 5% Nitrogen 5% Hydrogen -1% b. Explain what is meant by “gas content of a typical eruption is 1-6% of total magma weigh i. The more magma you have the more volatile the gas c. How does volcanic eruptions worldwide contribute to our current composition of the earth’s atmosphere?? i. It has gasses that come out onto the atmosphere Mafic type lava flows: 1. Explain the differences between a basaltic Aa and basaltic Pahoehoe lava flow in terms of high/low volatile content a. Pahoehoe is very fluid, thin, broadsheets, they move from 10-300 km/hr and high volatile gas content 2. What is a “good” way to differentiate the differences between an Aa and pahoehoe flow?

a. Aa is more notable for its heat than pahoehoe 3. Would you regard an Aa and Pahoehoe a “fluid” or “pasty” type flow --- Explain a. Pahoehoe is a fluid type flow because of the high volatile gasses as opposed to the Aa Felsic type lava flows: 1. Describe the following types of “felsic” eruptions: Volcanic bombs- emanate right from the opening the caldera part of the volcano Nuee-Ardente- travel 200 mph, ash cloud filled with volatiles, they roll down the flanks lahar- (mud flows) one has to envision in a felsic volcano, as the magma rises to the top of the volcano it starts to heat the surrounding snow Ash- Microscopic glass What is a “good” way to differentiate the differences between the type of flows described above? Rhyolitic magmas which are high In silica, are very pasty 2. What “volcanic” factors are involved in differentiating between a mafic (basaltic) lava from a felsic (rhyolitic) lava? Think: viscosity, silica content, volatile content, temperature, fluid flow, explosive flow. a. Mafic magmas are low in silica and contain more dar, magnesium, and iron-rich mafic minerals. Felsic magmas are higher in silica and contain lighter-colored minerals such as quarts and orthoclase 3. How does the factors above (number 3) give rise to various types of volcanoes found on earth? a. all volcanoes are different and knowing how to identify them will make it easier 5. Draw a diagram showing a picture of a typical volcano and label the following characteristics: flanks, volcanic conduit, crater, volcanic base, magma chamber, vent, parasitic cone, and volcanologist that studies volcanoes. 6. There a three major types of volcanoes (stratocomposite, shield, cinder cone) Shield, Composite, Cinder cone Relationship Questions : a. Discuss why three major types of volcanoes are found on the earth’s surface i. Shield Volcano is found in Hawaii. Formed by the accumulation of fluid basaltic flows with low silica content. (BasalticComposition) Low Viscosity. Less than 1% pyroclastic debris. Non-explosive eruptions pahoehoe flows aa flows. ii. Stratovolcano is formed from layering deposits of ash, lava, and pyroclastic flows. High silica content(70%)- Rhyolitic composition) high viscosity flows. Abundant pyroclastic activity, deadly airborne debris, explosive eruption- very hazardous. iii. Cinder Cones: (Scoria Cones) exist all over the earth's surface (by the 1000’s) characteristic of volcanic fields (Flagstaff, AZ., approx 600). Very high steep angled flanks 30-40 degrees. Average 100ft- 1000ft high. b. Draw a picture depicting each volcano type and draw the diagram accurate to the characteristics described in the above answer. c. Fill in the chart below:

SiO2 Viscosity “Fluid” or “Explosiv e ” Type of lava flow Chemical Compositi on n Brief Volcano Descriptio n. Shield Volcano Very Low Low Nonexplosi ve fluid Basaltic magma Found in Hawaii Cinder Cone Low Low Explosive Fluid pressure Can form a parasitic type of cone Composit e Volcano 70% High explosive pasty Abundant pyroclastic activity Formed from layering deposits of ash, lava 7. Research the internet and find 3 “famous” volcanoes that have been in the news. For each volcano you find, describe the “geological” characteristics using the above chart. In other words, what type of volcano does your choice reveal? Kilauea, hawaii- 1924. Lassen Peak- 1915 Mount Vesuvius- 79 A.D. 8. Throughout geologic history, live volcanic activity does not last forever, however evidence of volcanic activity is present on the earth’s surface by observing various types of volcanic landforms. Relationship Questions: a. Construct and draw diagrams depicting caldera’s, volcanic fissures and exposed volcanic features such as volcanic necks, pipes, volcanic flows, diatremes, and lava domes (plug domes). i. Caldera’s (cooking pot): larger depressions in excess of 1 mile diameter. 1. Formed the following ways Collapse of the summit following an explosive silica rich eruption (Crater Lake). Collapse of a shield volcano from drainage of central magma chamber (Hawaiian

Islands). Collapse of a large area from the discharge of colossal volumes of high silica rich pyroclastic materials. \ ii. Volcanic Pipes and Neck (diatreme) 1. Diatremes extend to depths of 200 km (125 miles) o Magma ascends rapidly with little alteration. 2. Characteristics of high P/T minerals o Considered “windows” to the Earth’s interior 3. Best known diatremes are the Kimberlite diatremes of South Africa Diamond bearing. b. For each volcanic feature above, list at least 3 distinctive characteristics that differentiates each type of volcanic feature. c. For each feature listed in (a), research and find a representative geographic location on earth where that feature exists. Caldera - it is commonly called the ring of Fire. Volcanic fissure- - Iceland and the great rift valley in Africa Volcanic neck - Ship rock in New Mexico and Devil’s tower in Wyoming Volcanic pipe- Vertical conduit beneath a volcano through which magma once passed on its journey Volcanic flow- Diatreme- Southeastern British Columbia, Canada Lava Dome - in the crater of large composite volcanoes d. Draw a diagram that shows the following igneous rock features associated with volcanism and non-volcanism. Given each term, indicate if the feature is extrusive or intrusive bodies of solidified igneous rocks. 1. Batholith: a very large igneous intrusion extending deep in the earth’s crus 2. Laccolith: a mass of igneous rock, typically lens-shaped, that has been intruded between rock 3. strata causing uplift 4. Stock: Irregular igneous body less than 40 square miles 5. Dike: a mushroomed type shape dome igneous 6. Sill: of igneous rock feature that is parallel to an overlying rock material 9. Plate tectonic processes are paramount when describing the physical and compositional characteristics of volcanoes and volcanic activity. Relationship Questions. a. Using the completed chart in question 6, add a new column, to the left of the volcanic description, that says “plate tectonic setting”. In the plate tectonic setting column, “briefly” describe the typical plate boundary setting responsible for each type of volcano. Types of Volcanoes Plate Tectonic Setting Composite Shield Cinder Cone

b. How does each tectonic boundary (divergent/convergent) provide the “chemistry (mafic or felsic” -- ie silica content) that allows the composite and shield volcano to exist? ---- Loaded critical thinking question. If you can answer this, you are in the league of volcanologists!! And the forefront of plate tectonics i. Divergent: plates separated resulting from basaltic magma ascending into fractures. 1. Convergence- Oceanic plate subducts beneath ocean plate. Melting subducted plate ascends upwards forming shield type of volcanoes basaltic c. List at least three famous, in the news, volcanoes and describe the plate tectonic setting. Based on the news descriptions, how does this now match your knowledge of the occurrence and activity of volcanoes? i. Kilauea, hawaii- 1924. ii. Lassen Peak- 1915 iii. Mount Vesuvius- 79 A.D. 10. Are Volcanoes and volcanic activity geologic hazards? Explain Yes the way the temperature of the ground rises Relationship Questions a. When does volcanic activity become hazardous? Think: population b. All volcanic activity is potentially dangerous ----- however, which of the two (shield or composite) poses the biggest threat? WHY? And explain c. How do volcanologists begin to predict a volcanic eruption threat? d. Which volcanoes today, in the news, are currently being monitored and pose a potential threat? e. Which volcanoes are active today in the continental US?

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