GEO109_SCI210_Lab+5+_Volcanoes+SP23 (1)

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Jan 9, 2024

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NAME: ________________ Table _ GEO 109L – Earth, Environment, & Society Lab SCI 210L – The Dynamic Earth Lab Lab Exercise 5 – Volcanoes & Viscosity Introduction In an earlier lab you observed, classified, and identified examples of Igneous Rocks. This week we will take a closer look at extrusive igneous rocks and the processes that form them. Often referred to as volcanic igneous rocks, the processes that form these extrusive igneous rocks are often violent and can cause harm to the populations that live near the eruption site. In order to gain a better understanding of the factors that influence the formation of extrusive igneous rocks, and thus the eruptions that may threaten us, you will experiment with a representation of igneous magmas/lavas. The significance of Melt Viscosity: Viscosity is an important property of magmas for several reasons:  it determines, in part, how rapidly a magma can move from its source region to the surface of the earth  it influences how fast crystals rise or sink in magma  it helps volcanologists predict whether the lava flow from a volcano will move very quickly, and hence be life threatening, or will move very slowly and not be life threatening  it is an important factor in determining the explosiveness of an eruption Materials:  Corn syrup  Glass beakers  Hot plate  Ice  Water  Sand  Straws  Ramp surface  Lava/syrup tray Lab Exercise: This lab investigates how certain factors can affect the viscosity of a volcanic melt. A magma or lava flow behaves differently depending on the temperature, dissolved water, gas content (bubbles), and percent of solid material (phenocrysts, visible crystals) it contains. You will experiment with three variables – temperature, liquids, and solids – and record how changes in these variables affect the thickness and flow of the representative solutions, as a model for how a volcanic melt would similarly be affected. Part 1: Physical Factors that Affect Viscosity – Temperature, Water, Solids, and Bubbles Lab 5 | 1

NOTE: Today’s lab can create a “sticky” situation so please be careful not to spill the materials and be sure you have on the lab station only the materials you’ll need for the experiment. Also, you’ll need to allocate time and labor at the conclusion of lab for adequate clean up. At the beginning of lab, your lab group (table) will be assigned a physical factor that is observed to affect the properties of a “lava.” Two groups each will be assigned temperature, water, and solids, and will receive additional instructions per their assigned factor. The instructions will detail how to prepare three "lava" setups with different viscosity solutions using the clear corn syrup provided. Every group will share their data on the classroom board so comparisons can be made. At the end of lab, we will discuss as a class how varying each factor affected the rate of flow for each set up and group. 1) Circle the viscosity factor your group is investigating below. Make sure to follow the setup instructions (provided in lab) for your group’s factor. Temperature Water Solids 2) Take a moment and discuss with your group, which of the three syrup variations for YOUR GROUP’S FACTOR do you think will have the highest, intermediate, and lowest viscosities. Again, this will depend on what factor your groups is working with. The three syrup set-ups will be described on the instructions sheets provided. Which variation will have the Highest viscosity? __________________ Which variation will have the Intermediate viscosity? __________________ Which variation will have the Lowest viscosity? ____________________ Part 2: Viscosity Experiment Set-up Individual group viscosity experiments: Each table will complete a different experiment by varying a specific factor that affects viscosity of a magma/lava (represented in lab by corn syrup). Follow the set-up instructions provided for your table. You will have instructions that vary either temperature, amount of water, or amount of solids. Bubble Test 3) Before pouring the syrup out of your beakers , complete a bubble test in each of your three beakers. You will be observing how much force it took for you to blow bubbles with a straw, how long it took for those bubbles to move up in the syrup, and a description of the type of bubbles. Record your observations in the table following. You only need to describe how the three set-ups (beakers) compare to each other in a relative sense. For example, which set-up was the easiest to blow bubbles into, the hardest, and in the middle. You do not need to take absolute measurements or quantify anything for this test. FACTOR SET-UPs (Each row corresponds to Relative force required to blow bubbles in syrup Relative time for bubbles to travel up to the syrup-air Description of bubble formation (coalescence into large bubbles? 2

NAME: ________________ Table _ one of your beakers – label each) (harder, easier, etc) interface (slower, faster, etc) many small bubbles?) 1– Control (Unaltered) 2 3 Pour Test 4) Now you will perform tests to observe the changes in viscosity for each beaker and gather data to compute the viscosity of each. a) Ensure your ramp is set up with an incline at approximately 40 degrees. b) Make sure the end of your ramp is placed in the catch tray, and covered with plastic wrap for easier clean up. c) In the table following, record how long it takes for each type of syrup to reach the bottom of the incline after each pour. d) In addition, estimate the thickness of the flow at the indicated point on the inclined board (your board will be marked) – about ¼ of the way down – and observe the overall shape of the flow. e) It will help if you divide up the duties so that you have individuals doing the following tasks: Pourer, timer and flow thickness observer. 1. Pour the entire beaker out fairly quickly. 2. Measure from the starting point to the point when the leading edge contacts the end of the board. 3. During the flow, have at least one person look sideways at the flow to estimate the thickness towards the top (in millimeters and then convert to centimeters). 4. Consider capturing each of your pours on video (smartphone). You can delete after lab. YOU CAN RECORD YOUR RESULTS IN THE HARD COPY PROVIDED FACTOR SET-UPs (Each row corresponds to one of your beakers – label each) Distance Traveled (cm) Time of Travel (s) Velocity (cm/s) Estimated Thickness at marked area (cm) 1– Control (Unaltered) 2 3 5) Make sketches of each of the three "lava" lobes in your experiment, showing how the width of the lobe varies along its length. Record the maximum width of each flow and use this to help you determine if the flows are Lab 5 | 3

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relatively “broad” or “narrow” in comparison to each other – and so which value of “n” to use in your calculations. 1 2 3 Max width ____ cm Max width ____ cm Max width ____ cm Sketch 1 Sketch 2 Sketch 3 Part 3: Calculating Velocity 6) Estimate the viscosities of the three different syrup mixtures based on Jeffreys equation (below). Record your results in the table following. Show all your work (use open space on next page). η = viscosity in poise (dyne s /cm = g /cm-s ) g is the gravitational constant (980 cm/s 2 ) ρ is density (1.4 g/cm 3 for the corn syrup; Note that adding water and/or sand does not significantly change the density of the solution so you can use this value for all three calculations. α is the angular measurement of the slope (no units) d is the thickness of the flow (in cm), n is a constant (3 for broad flows and 4 for narrow, channelized flows) V is the measured velocity (in cm/s). SHOW WORK FOR EACH (ex. on the back page of the lab) Part 4: Analysis of Experiment Results Once you completed these calculations, record your velocity and viscosity on the classroom board to share your results with the rest of the class for use in answering the questions following. Check your answers with the instructor before posting on the board. 4 FACTOR SET-UPs (Each row corresponds to one of your beakers – label each ) Calculated viscosity (poise) Rewrite your viscosity values using Significant Figures and Scientific Notation. 1 – Control 2 3

NAME: ________________ Table _ Copy the result for all groups from the board to the table below. Use Significant Figures/Scientific Notation for viscosity. Factors Group 1 - Velocity Group 2 - Velocity Group 1 - Viscosity Group 2 - Viscosity Water (1 tsp) Water (3 tsp) Solids (1 tbsp) Solids (2 tbsp) Hot (110°) Cold (50°) Control Flow (Unaltered) – Just list your group’s results Velocity: Viscosity Each group will record their viscosity results on the chalkboard. Review all results before answering the following questions. If you do not understand what a question is asking about the experiments, call your instructor over to clarify. 7) ACH Foods Inc. reports that Karo Light Corn syrup has a viscosity of 22-30 poise at 25 C (room temperature). How do your results for the unaltered corn syrup compare to the “official” viscosity range? Are the values within one order of magnitude of the reported value? So is it a significant difference? Explain. 8) Based on the results for all groups (on chalkboard), summarize the effect of changes in each factor (Temperature, Water, Solids) on the corn syrup. Temperature: Water: Solids: 9) Which of these factors had the greatest impact on the overall viscosity of corn syrup? Explain how you determined this. Lab 5 | 5

10) Develop a hypothesis that relates the amount and/or size of gas bubbles in a lava to the explosiveness of an eruption. Consider the relationship between the amounts and/or size of bubbles (and the ease of blowing them!) and viscosity ( think about your first bubble test – question 3 ). Ex. High Viscosity - Bubbles hard or easy to blow through (more of less force?) – so would it have more frequent small eruptions or less common, large explosions? Part 5: Connecting Corn Syrup to Molten rock and Volcanic Eruptions. Continuous Flow Eruptions 11) Take a look at the videos of Hawaiian basaltic (mafic) lava flows and rhyolitic (felsic) lava flows at Mount St. Helens – the links are included in Isidore Resources . NOTE – Pay attention to the time period covered by each video (time-lapse, real-time, or slow-motion) in order to correctly judge the speed of the flow. Continuous Flow Hawaii: https://www.youtube.com/watch?v=kWA6BZEs4vc Continuous Mount St. Helens. http://www.youtube.com/watch?v=h6B1myUKAS4 (post 1980) Describe the relative speed the lavas are flowing for each volcano and what the materials look like (how liquid; how solid? 12) Which eruption, Hawaii or Mt. St. Helens has: (you might also look at the figure on the last page of the lab that relates viscosity to rock type). Higher viscosity: ______________________ Lower viscosity: ______________________ Catastrophic Eruptions 13) View the following eruption videos. The first is from Mt. Etna, Italy (similar to Hawaii-style volcanoes) and the second (and third) from Mt. St. Helens. This time you will be viewing catastrophic eruptions from each (not continuous as in the previous videos). Again, note the time covered by each video (St. Helens is in slow-motion). Also note the scale of each eruption. USE Google Chrome as your browser to best view the videos. Mt. Etna, Italy (December 2015) https://www.youtube.com/watch?v=DazOdW6iqjE Mt. St. Helens (May 1980) Eruption begins: http://www.youtube.com/watch?v=bgRnVhbfIKQ 6

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NAME: ________________ Table _ and… Eruption continues at 3 minute mark in the following video: http://www.youtube.com/watch? v=Ec30uU0G56U 14) Take a look at the Handout showing the different eruptive styles volcanoes can have and identify eruptive styles (there maybe more than one) that would more closely match each volcano. Hawaii: _________________________ Mt. Etna: ________________________ Mt. St. Helens ______________________ 15) Discuss the relationship between viscosity, lava type (mafic/felsic), and explosiveness of eruptions by using the Hawaii, Mt Etna and Mt St. Helens eruptions as examples: Comparison to Mars 16) Compare the viscosity value of lava flow #1 from Elysium Mons, Mars obtained in your prelab to the graphic shown below. Viscosity of Mars lava flow (from pre-lab) _____________________ Use the chart below (carefully read it!), What type of lava (rhyolitic, basaltic, etc) do you think is present in lava flow #1? Circle the appropriate section of the chart. ____________________________ NOTE: Andesite lava is a mixture of rhyolitic and basaltic lava 17) How explosive do you think the Elysium Mons eruption was? Which volcano would Elysium Mons be most similar to, Hawaii, or Mt. St. Helens? Briefly explain your answer below. Lab 5 | 7

NAME: ________________ Table _ This page is left intentionally blank. Lab 5 | 9

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GEO109_SCI210_Lab+5+_Volcanoes+SP23 (1)

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