Lab Power Point For Plp Analysis Of Magma Viscosity
- 1. LAB: *MAGMA VISCOSITY*
- 2. OVERVIEW Lava is molten rock that has been ejected onto the surface by a volcano. Magma is molten rock that exists below the earth’s surface. Magma comes in many varieties: *It can range from thin and runny to thick and oozy. *It can have a range of temperatures from low (cool) to high (searing hot). *It can range from low gas content to high gas content. *It can range from a low silica content to a high silica content. The type of magma plays a big part in the type of eruption a volcano may produce. In turn, the eruption of lava plays a major role in the formation of volcanoes, as material accumulates and forms thick layers and piles on the surface of the cone.
- 3. If the lava is runny, it will flow downhill easily and spread out to form a shield volcano. If it is thick, chunky, and oozy, the lava will not move downhill very fast and may cool and solidify before reaching the bottom. This builds a steeper volcano, possibly a cinder cone or even a composite volcano. SHIELD VOLCANO CINDER CONE VOLCANO COMPOSITE VOLCANO
- 4. VISCOSITY Viscosity is the resistance of a liquid material to flow. In other words, it refers to how easily a fluid can move when subjected to gravity. The ability to flow hinges on the consistency of the lava - how thin or how thick it is. *Low viscosity causes the lava to be thin and runny. *High viscosity causes the lava to be thick and oozy.
- 5. Temperature plays a part in this as well. *Low temperatures cause lava to thicken and become more viscous. *High temperatures cause lava to stay thin or less viscous. The amount of gases contained in magma will also affect its nature. *Low gas content allows the particles to stay condensed, making the magma thick. *High gas content spreads out the particles and makes the magma thin. Gas pressure within the volcano’s vent will be affected by the thickness of the magma: *If the magma is thin, gas pressure can bleed off easily, and there will be a quiet eruption. *If the magma is thick, gas pressure builds due to the magma becoming clogged in the vent. This causes a violent eruption.
- 6. The viscosity of the lava depends mostly on the silica content, which is the amount of silica in magma or lava. *Low silica content causes low viscosity. *High silica content causes high viscosity. Magma can be of three types: *basaltic – has a low level of silica. *granitic – has a medium level of silica. *andesitic – has a high level of silica.
- 7. Purpose of this lab: The purpose of this lab is to initiate and observe three scale model volcanic eruptions in order to analyze the viscosity of magma. The three samples of synthetic “magma” have different levels of “silica” present. Students will determine magma viscosity , and compare and contrast the three eruptions.
- 8. Materials needed: There are supplies needed for use by the teacher. *Refer to the attached video clip. (click below)
- 9. Other materials needed: There are supplies that the students will need for their groups. *Refer to the attached video clip. (click below)
- 10. PROCEDURES: PHASE 1 -– Build the volcano model: *Refer to the attached video clip. (click below) The distance between the start line and the finish line on the volcano cone model is actually 7.8 cm .
- 11. PHASE 2 - Set up data table: SAMPLE # DISTANCE (CM) TIME (S) VELOCITY (CM/S) VISCOSITY (L, M, H) 1 7.8 __ 2 7.8 __ 3 7.8 __
- 12. PHASE 3 - Fill the test tubes: *Refer to the attached video clip. (click below)
- 13. PHASE 4 - Fill the dixie cups: *Refer to the attached video clip. (click below)
- 14. PHASE 5 - Trigger and measure the eruptions: TRIAL #1 (magma sample #1) *Refer to the attached video clip. (click below)
- 15. Log data for Trial #1 (magma sample #1): SAMPLE # DISTANCE (CM) TIME (S) VELOCITY (CM/S) VISCOSITY (L, M, H) 1 7.8 181.71 __ 2 7.8 __ 3 7.8 __
- 16. TRIAL #2 (magma sample #2) *Refer to the attached video clip. (click below)
- 17. Log data for Trial #2 (magma sample #2): SAMPLE # DISTANCE (CM) TIME (S) VELOCITY (CM/S) VISCOSITY (L, M, H) 1 7.8 181.71 __ 2 7.8 52.12 __ 3 7.8 __
- 18. TRIAL #3 (magma sample #3) *Refer to the attached video clip. (click below)
- 19. Log data for Trial #3 (magma sample #3): SAMPLE # DISTANCE (CM) TIME (S) VELOCITY (CM/S) VISCOSITY (L, M, H) 1 7.8 181.71 __ 2 7.8 52.12 __ 3 7.8 4.10 __
- 20. Figure the velocity of each magma flow: Trial #1: v = d / t v = 7.8 cm / 181.71 s v = .0429255 cm/s Trial #2: v = d / t v = 7.8 cm / 52.12 s v = .1496546 cm/s Trial #3: v = d / t v = 7.8 cm / 4.10 s v = 1.902439 cm/s * To figure the velocity of the magma flow, use the formula: v = d / t (velocity = distance / time)
- 21. Log the velocity for each magma sample: SAMPLE # DISTANCE (CM) TIME (S) VELOCITY (CM/S) VISCOSITY (L, M, H) 1 7.8 181.71 .0429255 __ 2 7.8 52.12 .1496546 __ 3 7.8 4.10 1.902439 __
- 22. Determine whether each magma sample had a low, medium, or high viscosity and log each one: SAMPLE # DISTANCE (CM) TIME (S) VELOCITY (CM/S) VISCOSITY (L, M, H) 1 7.8 181.71 .0429255 HIGH __ 2 7.8 52.12 .1496546 MEDIUM 3 7.8 4.10 1.902439 LOW __
- 23. CONCLUSION Part 1: *Magma sample #1 in Trial #1 was determined to be of high viscosity because it had the slowest flow rate (velocity). Therefore, it could have contained the highest amount of silica (possibly basaltic in nature). Also, it could possibly have a low gas content, and may have been a cooler temperature than the other two samples.
- 24. CONCLUSION Part 2: *Magma sample #2 in Trial #2 was determined to be of medium viscosity because it had a flow rate (velocity) that fell between the other two samples. Therefore, it could have contained a medium amount of silica (possibly granitic in nature). Also, it could possibly have a medium gas content, and may have been a medium temperature, falling somewhere between the other two samples.
- 25. CONCLUSION Part 3: *Magma sample #3 in Trial #3 was determined to be of low viscosity because it had the fastest flow rate (velocity). Therefore, it could have contained the lowest amount of silica (possibly andesitic in nature). Also, it could possibly have a high gas content, and may have been a hotter temperature than the other two samples.
- 26. CONCLUSION Part 4: The students’ times will vary from group to group. They must be sure to start and stop timing as precisely as possible. The variance in times will also vary the magma velocities. Be prepared to have different answers for different groups. Although, the sequence of viscosities is actually “high - medium - low”. If the students have them listed in a different order, then an error occurred somewhere.
- 27. Analysis Questions: 1. What is viscosity? 2. What factors can affect magma / lava viscosity? 3. How is viscosity related to the shape and height of a volcano? 4. How might gas pressure within the volcano, coupled with magma viscosity, affect the type of eruption that a volcano may produce?
- 28. Answers: 1. Viscosity is the resistance of a material to flow. It hinges on the consistency (thickness) of the material. 2. Factors that can affect the viscosity of magma / lava may include thickness (density), temperature, gas content, and silica content. 3. If lava has a high viscosity, it is thick. Therefore, it will tend to flow short distances and will stay at or near the top of the volcano. This builds tall, cylindrical cones (cinder cone and composite volcanoes). However, if the lava has a low viscosity, it is thin and runny. It will flow long distances and will build a cone that is wide at the base (shield volcano). 4. High viscosity magma tends to clog the volcano’s vent, building gas pressure, and causing a violent eruption. Low viscosity magma does not clog and allows gas to escape, allowing for a quiet eruption.