ERTH1052 Lab 9 Natural Disasters worksheet

Name: ___________________________________ ERTH 1050/1052 Lab 9 – Natural Disasters Moviestar Volcano: Mt Ngauruhoe in New Zealand played the role of Mt Doom in the Lord of the Rings movies. Introduction Nothing on Earth leaves us as humbled as the occurrence of a natural disaster. Whether it is a landslide that washes away an entire city block within minutes, or a volcanic ash plume that blocks out the Sun, natural disasters provide drastic reminders that we live in and are subject to Earth’s dynamic environment. Different places must cope with the risk of different natural disasters and many Earth scientists occupy themselves with the risk of natural disasters: studying the conditions for natural disasters, anticipating them, and managing risk. Objectives . When you’re done with this lab, you should be able to: 1. Understand what the “angle of repose” is 2. Explain the role of water and substrate type in mass movement 3. Understand risk factors in earthquakes, wildfires and floods 4. Understand how zoning can mitigate natural disaster risk 5. Calculate the recurrence rate of volcanic eruptions (and other natural disasters) Materials 3 ramps, 3 cups, 3 trays, tablespoons, sand, gravel, water, laminated map of “Huskyville”, protractor

Part I: Mass Movement Mass movements are the downslope or downward movement of a solid, continuous or discontinuous mass, under the influence of gravity. It’s one of the main processes that matter gets moved around the world. For our part, mass movements can be a hazard, since a person or infrastructure getting caught up in the downward movement of rocks, sediment or soil, can have disastrous consequences. But not all matter is equal, and different materials will start to move under different conditions. For example, solid rock can be at a right (90 ° ) angle to the landscape, or even higher, without falling over. However, if you tried to make a right angle using marbles, you’re in for a frustrating experience. The resting angle of a material, the maximum angle that a pile of that material can make with a horizontal plane without moving, is known as the angle of repose . Let’s experiment with the angle of repose of material. You’re going to create three different mixtures of sand, gravel and water in a cup today, hypothesize which mixture will have the highest angle of repose, and then test it using the ramp, tray and protractor. Creating the mixtures: fill one cup halfway with water, one cup halfway with sand, one cup halfway with gravel. Then, discuss with your group what the rest of each cup is going to be filled with. This can be ANY mixture of water, sand or gravel. You can also decide to not include one of the ingredients into the mixture. Make the mixture, stir thoroughly, then answer the following questions. 1.1. Experimental Setup Question. How much water, sand or gravel did you add to the cups? Give your answer in tablespoons. [2pts] Water Sand Gravel Cup 1 ½ cup Cup 2 ½ cup Cup 3 ½ cup 1.2. Interpretation Question. Before doing anything, which mixture do you think has the highest angle of repose? Explain in one sentence. [1 pt] 1.3. Hypothesizing Question. Formulate a Null Hypothesis about the angle of repose of your mixtures. The Null Hypothesis is always that there will be no difference in experimental conditions. This way, if you DO observe a difference in experimental conditions, we know the Null Hypothesis needs to be rejected. [1 pt]

1.6. Interpretation Question . Do you reject or accept your H0 hypothesis from Q1.3? Explain! [1 pt] 1.7. Interpretation Question . Did your expected mixture indeed have the highest angle of repose (from Q1.2)? If no, explain what might have caused this, and if yes, explain how you might have reduced its angle of repose. [1 pt] Part II: Huskyville Huskyville is an imaginary town that has to deal with hazards of three natural disasters. 1) Earthquakes: Huskyville lies on an active fault line, 2) Floods: part of the town is on the floodplain of the White Oak River, and 3) Wildfires: Huskyville gets seasonally dry, so forest fires can break out. Huskyville doesn’t have rules regulating where one can build, and as a result, people have built homes and businesses in high risk areas. The Huskyville city council now wants to change that, creating three zones. Zone 1: low risk zone for important infrastructure such as hospitals, schools, governmental buildings and energy infrastructure, Zone 2: medium risk zone for low density residential and commercial infrastructure, and Zone 3: high risk zones for natural space and agricultural land. The Huskyville city council is hiring geological consultants in order to best assign zones to the town. You will take on the role of those geological consultants. In front of you, you have three maps: a topographic, a substrate (soil / bedrock), and depending on your assigned expertise: a drainage, fault and a vegetation map. 2.1. Interpretation Question. Study the maps in front of you (topography, substrate & special expertise map). Discuss with your group and write down what the best combination of topography, substrate & (depending on your expertise) proximity to streams, faults or vegetation type would look like. Explain your answer. [2 pts]

2.2. Interpretation Question. The grid below corresponds to the gridcells on each of your maps. Fill in 1, 2 or 3 for what you and your group members have agreed upon are the best places for zones 1, 2 and 3. Choose five gridcells for Zone 1, eight gridcells for Zone 2, and twelve gridcells for Zone 3. [4 pts] 2.3. Collaboration Question. Send one group member to the front of the class to fill in your zoning scheme on the grid that your instructor has put on the board. Meanwhile, have a look at the zoning schemes that groups with other expertises have come up with. Which expertise zoning scheme conflicts the most with yours? Why do you think that is? [2 pts]

Part III: A Civilization-Ending Natural Disaster Asteroids often get depicted in popular media as the way that civilization and possibly humanity ends. However, the real killer was inside the house all along , since volcanoes, and more specifically supervolcano eruptions are much more likely to pose a global threat. In the next exercise, you will learn how geologists calculate the likelihood of a volcanic eruption, and how that allows them to estimate how frequent a supervolcano eruption might be. Alaska and the Aleutian Islands are a very volcanically active region. If you open up the provided spreadsheet “ERTH_Volcano.xlsx” on HuskyCT, and open the tab with “Alaska”, you’ll see a list of all the active volcanoes there, the years they’ve erupted, and the “Volcanic Explosivity Index” (VEI) of those eruptions. VEI is a measure for the severity of the eruption, classified by the height of the ash plume and the volume of volcanic ejecta (see the table below). VEI 0 1 2 3 4 5 6 7 8 Plume height (km) <0.1 0.1-1 1-5 3-15 10-25 >25 >25 >25 >25 Ejecta volume (km 3 ) <10 -5 10 -5 -10 -3 10 -3 -10 -2 10 -2 -0.1 0.1-1 1-10 10-10 2 10 2 -10 3 >10 3 3.1. Excel Question. In the Alaska tab in Excel, the number of eruptions with VEI = 2 is counted, but those for VEI = 3 and VEI = 4 is not. If you click on cell F2, where the number of eruptions with VEI = 2 is counted, you’ll find out a hack to have Excel count for you. What is this function called? [0.5 pts] 3.2. Excel Question. See if you can apply this function to count the number of VEI = 3 and VEI = 4 eruptions in Alaska and the Aleutian Islands. [0.5 pts] VEI = 3: _________ eruptions, VEI = 4: _________eruptions 3.3. Excel Question. How many years do you have records for in this Excel spreadsheet? HINT: the function =MIN() and =MAX() give you the minimum and maximum value of a range of numbers. [1pt] 3.4. Calculation Question. In column G, it says “recurrence interval”, which refers to the amount of time between volcanic eruptions of a certain size. You can calculate it by dividing the number of years on

record by the number of volcanic eruptions of a certain size. What is the recurrence interval for the three VEI levels listed here? Give your answer in YEARS. [2 pts] VEI = 2 recurrence interval: __________, VEI = 3 recurrence interval: ___________, VEI = 4 recurrence interval: ____________ 3.5. Excel Question. Now, we’re going to predict the recurrence interval of larger eruptions, based on the information that we have. First, create a scatter plot with VEI on the x-axis and recurrence interval on the y-axis. Second, right click on one of the three points (doesn’t matter which) and select “Add Trendline”. A straight line now appears that sort of runs halfway between the three points that you have. Third, right-click on the trendline and select “Format Trendline”. Under “Trendline Options” toggle from “Linear” to “Exponential” (since the relationship between size and recurrence rate of volcanic eruptions is exponential, not linear). Finally, you can predict the recurrence interval of larger eruptions by entering “2” in the box that says “Forecast Forward”. Now read off the graph: what are approximately the recurrence intervals of VEI = 5 and VEI = 6 eruptions in Alaska? Give your answer in years. [2pts] VEI = 5 recurrence interval: ____________, VEI = 6 recurrence interval: _____________ 3.6. Interpretation Question. Oddly, no VEI = 5 eruptions have been observed in Alaska in the 20th and 21st century. However, the Novarupta eruption of 1912 was VEI = 6. How does this affect your answer in Q3.5. Explain your answer. [1 pt] 3.7. Calculation Question. Let’s get a sense of scale of how much material a volcano can erupt. Ejecta refers to any pyroclastic particle that becomes airborne during an explosive volcanic eruption (so mostly ash, but not lava flows). Look up in the table on the previous page the volume of ejecta the 1912 Novarupta eruption would have put in the atmosphere. The total area of the UCONN Storrs campus is about 3 km 2 . How deep a layer of volcanic ejecta would the UCONN Storrs campus be covered in, if all of the ejecta from the Novarupta eruption were distributed evenly over this area? Give your answer in kilometers AND in feet. [2 pts] 3.8. Excel Question . A supervolcano eruption is a VEI = 8 eruption. They are extremely rare on the timescale of civilizations, but surprisingly common on geologic timescales. In the Excel spreadsheet, go to the tab labeled “World”. Repeat the steps in Q3.5 in order to predict the recurrence intervals of VEI = 7 and VEI = 8 eruptions. Give your answer in years. [2 pts] VEI = 7 recurrence interval: ___________, VEI = 8 recurrence interval: ____________