Can someone help me answer these questions for my natural hazards lab? Thanks. T
ID: 284307 • Letter: C
Question
Can someone help me answer these questions for my natural hazards lab? Thanks.
Tephra: Fragmental material produced by a volcanic eruption regardless of composition, fragment size or emplacement mechanism. Tephra fallout is also commonly referred to as volcanic ash.
For this lab you will utilize the Tephra2 online simulation tool available through Vhub.org.
You will need to create a Vhub account by going to (https://vhub.org) and clicking the ‘Register’ link in the upper right corner (its free and easy to do).
The Tephra2 tool calculates the sedimentation of tephra on the ground given a particular eruptive scenario. To access the tool, go to www.vhub.org. Hover your mouse over ‘RESOURCE WAREHOUSE’, and select ‘Online Simulation Tools’. Find and select ‘Tephra2: Student Version” from the Resources column. Alternatively the direct link is https://vhub.org/tools/tephra2edu. Then Click the ‘LAUNCH TOOL’ button to begin using this resource. Select English as language, then read the notes that appear. Click to advance to the inputs page.
PART I: (20 points) Learning about the Tephra2 Inputs
First you will explore the inputs accepted by the Tephra2 code. The first parameter asked for is which volcano to consider. For this assignment you should use Colima Volcano - so you can go ahead and select this volcano. The second parameter asked for is the wind field. The ‘Random Wind Field’ option will randomly sample a list of approximately 1000 wind files, all of which represent actual wind fields measured near the volcano selected over a five-year period. This will produce the most realistic output. For this assignment, however, select one of the constant wind fields. The third parameter is Eruption Type. (1) What are the options for eruption type? (2) What are the main differences between each eruption type? Hint: Which of the Eruption Parameters change as you select the different eruption types? How do they change?
Now move on to the Particle Parameters tab under Eruption Parameters. For this assignment use the default values for maximum and minimum grainsize.
(3) What is the default value for the median grainsize erupted, in mm?
(4) What is the density of the particles being ejected from the vent? Be sure to include units.
The Simulation - Parameters tab describes the type of column model that the program will use. Select different particle release heights and examine the associated image. (5) Why is it reasonable to consider dispersal from only the upper part of the column? (use what you learnt in class about eruption columns to help you). Return the column model to its default (Particles released from upper 20% of column).
Finally, select the volcano information and images tabs. Here you will find some basic information about the volcano and a photograph and location map of Colima volcano. (6) Briefly describe the volcano. What type of volcano is it? What kind of eruptions are typical for this type of volcano ?
(7) Considering the type of volcano in question, name at least one volcanic hazard, other than tephra fallout, that might pose problems given an eruption at Colima volcano. Explain why you chose the hazard you chose.
Find Colima city on the location map. (8) How far away from the volcano is the city? In what direction, relative to the volcano, is the city located?
Now you are ready to run your first simulation. For the moment, leave both the ‘Compare model result to field data?’ and ‘Re-use previous wind field?’ boxes unchecked (no).
You may select whatever eruption type you like. Select one of the two constant wind fields while leaving all other parameters at their defaults. (If you have already altered the defaults, simply close the application and re-launch the tool). Hit the ‘Simulate’ button and wait for the program to run.
Eruption Type: ___________________ Wind Field: __________________________________
The code provides multiple outputs. After you run a simulation you can switch between these using the tab at the right hand side of the results box.
Select the ‘Isopach Map: No Topography’ window. Note that this option plots only the area over which calculations were made while the map with topography has a constant, pre-defined size. The contour lines on this plot are called ‘isopachs’. (9) What does an isopach usually represent? (10) What are the units associated with these isopachs? What might be a more accurate term for these contours? Hint: clicking the magnifying glass to the left of the image will enlarge the plot making it easier to read. You can also look in the Tephra2 Output file. (11) What parameter would you need to know to convert from one to the other ?
(12) 3. Sketch a representative number of isopachs in the space below. Where is tephra accumulation greatest?
Colima volcano (red triangle on the map)
(13) Predict how the accumulation of tephra will change if you select the other constant wind field. Draw your prediction below.
Wind Field: _____________________________________
Colima Volcano
Clear your result by selecting the ‘clear’ button in the lower right corner. Return to the inputs section by selecting ‘Inputs’. Run the simulation again, this time selecting the other constant wind field. (14) Was your prediction correct? Explain.
Explanation / Answer
(1) What are the options for eruption type?
Voilent Strombolian, Subplinian and Plinian
(2) What are the main differences between each eruption type? Hint: Which of the Eruption Parameters change as you select the different eruption types? How do they change?
Type of eruption Eruption Height (max.km) Mass x10*11kg
Voilent Strombolian, 2 to 9 0.01 to 0.8
Subplinian 8 to 18 1 to 8
Plinian 20 to 35 1 to 100
Now move on to the Particle Parameters tab under Eruption Parameters. For this assignment use the default values for maximum and minimum grainsize.
(3) What is the default value for the median grainsize erupted, in mm?
The default value for the median grainsize erupted 5 mm
(4) What is the density of the particles being ejected from the vent? Be sure to include units.
The density of particles being ejected from vent are 1200 kg/m3
The Simulation - Parameters tab describes the type of column model that the program will use. Select different particle release heights and examine the associated image.
(5) Why is it reasonable to consider dispersal from only the upper part of the column
Grain size dispersal is only in upper part of column because the force is reduced and grains start falling by dispersing
(use what you learnt in class about eruption columns to help you). Return the column model to its default (Particles released from upper 20% of column).
Finally, select the volcano information and images tabs. Here you will find some basic information about the volcano and a photograph and location map of Colima volcano.
(6) Briefly describe the volcano. What type of volcano is it? What kind of eruptions are typical for this type of volcano ?
Colima volcano is located in Western Mexico Volcanic belt. It is a strato volcano. Voilent Strombolian type eruptions occur in this type volcano
(7) Considering the type of volcano in question, name at least one volcanic hazard, other than tephra fallout, that might pose problems given an eruption at Colima volcano. Explain why you chose the hazard you chose.
The volcanic eruption in 1913the summit and formed deep crater
Find Colima city on the location map. (8) How far away from the volcano is the city? In what direction, relative to the volcano, is the city located?
The Colima city is around 50 km away from the Volcano.The city is located south of the volcano
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