GEOSCI 106 Lab 7_ Lahars- MARCH
pdf
keyboard_arrow_up
School
University of Wisconsin, Madison *
*We aren’t endorsed by this school
Course
106
Subject
Geology
Date
Dec 6, 2023
Type
Pages
7
Uploaded by MateBraveryOyster20
GEOSCI/ENVIR ST 106: Environmental Geology
Lab 7: Lahars
Assignment Overview:
In this lab you will investigate the hazards posed to several communities in the
Pacific Northwest by lahars through examination of lahar hazard maps.
Instructions:
Fill out each red highlighted field (_________) according to each question’s instructions.
Submission:
To submit the assignment on Canvas, use the following steps:
1.
In Google Docs, generate a PDF: File → Download as → PDF Document
2.
In Google Docs, use Share → Get Shareable Link, and copy the link address
3.
In Canvas, upload your PDF to the assignment.
4.
In Canvas, paste the link address to your Google Doc in the assignment comments.
1
Part 1: Lahar characteristics
1. Define a lahar. (1 point)
A volcanic mudflow created by volcanic ash and water._________
2. How does a lahar originate? (1 point)
They are formed when an eruption melts snow or ice on the top of a volcano and flows down
slope._________
3. Why do lahars tend to follow river beds? (1 point)
I think they follow river beds because of the low altitude that comes with river beds making it easier
for them do flow downhill._________
Part 2: Mount Rainier lahar hazards
Complete the following questions using the following lahar hazard map for Mount Rainier.
2
Figure 1.
Map of lahar hazards around Mount Rainier for three different scenarios (Cases 1, 2, and
3). Case 1 is for big lahars that occur once every 500-1000 years. Case 2 is for medium-sized lahars
that occur once every 100-500 years. Case 3 is for small lahars that occur once every 1-100 years.
3
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Colors indicate the areas that would be inundated by each type of lahar. From Cakir and Walsh
(2012).
4. Based on the hazards map and the distribution of roads on the map, where would you expect the largest
amount of property damage from a Case I lahar? (2 points)
I think the most property damage would be around the cities in the northwest as there are many rivers
that flow to the Puget sound and lahars tend to follow river beds._________
5. Using the hazards map and other data sources (e.g., Google Maps), what major interstate highway
would likely be affected by a Case I lahar, and what major cities would be affected by this disruption? On
this map, major cities are distinguished from minor cities by the size of the font used for their names. For
example, in the top left corner of the map, the font size for Bremerton indicates a major city, while the
font size for Port Orchard indicates a minor city. (2 points)
Highway: 162, 12, 706, 410, 165, 167, and part of 5_________
Cities: Puyallup,_Auburn, ________
6. Using the scale at the bottom of the map, estimate the maximum distances travelled along the riverbeds
(in km) by: (3 points)
Class III Lahars: _At Most 10 km________
Class II Lahars: _75km________
Class I Lahars: _95km________
7. (a) Speeds of lahars differ as a function of slope and fluidity, but 40 kph is not unusual. At that speed,
approximately how long would it take for a lahar from Mount Rainier to reach the small town of Ashford
(WSW of Mt. Rainier)? Show your work. (1 point)
_V=D/T, T=D/V; T=20km/40kmph=.5hour ________
(b) How long would it take to reach Puyallup, on the outskirts of Tacoma? Show your work. (1 point)
_T=D/V;__T=50km/40kmph= 1.25hour______
4
Part 3: Glacier Peak lahar hazards
Now that you’re familiar with the idea of a lahar hazard map, you will try to make one of your own using
the following satellite image of the Skagit Valley and the Glacier Peak volcano in Washington State. You
may find it helpful (though it is not strictly necessary to answer the following questions) to investigate
this area manually through Google Earth to get a better feeling for the topography around Glacier Peak.
Figure 2.
Satellite image of Glacier Peak (see yellow pin on the right half of the image) and
surrounding terrain. White lines show the approximate outline of Skagit County. This is the same
image that is available in the Canvas lab module.
8. In the Canvas lab module, download the file “Glacier Peak satellite image.png”. This is the same
image as that in Figure 2. Based on the map from Mt Rainier, and assuming a Case I lahar of roughly the
same magnitude as those in Figure 1, sketch on the satellite image where you think lahar inundation zones
would be on the map. (You are welcome to outline the lahar inundation zones with any image editing
software you like. For example, you could do this in this Google Doc through Insert > Drawing > New,
5
then dropping the “Glacier Peak satellite image.png” file into the drawing space, and editing it there.)
Paste your modified image here. (3 points)
_
________
9. Though prone to an assortment of volcanic hazards, the Skagit Valley is an incredibly beautiful place.
If you wanted to move to a town in Skagit County (see white lines for approximate outline of Skagit
County in Figure 2), but take into account the prospect of lahars, where would you move and why?
(Note: Island life is not an option – too expensive, sorry!) Explain your reasoning in 2-3 sentences. For
example, you can discuss the warning time you would have, topography, and other factors. (2 points)
I would live in south western Sedro-Woolley close to the water so I am farther away from the volcano
but far enough from the water so it doesn’t flood into my house if there is a big enough lahar. I think
living there would be the safest option because it would give me ample warning time and I wouldn’t
be right in the valley where the lahar comes through._________
6
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
References
Recep C, Walsh, T. J., 2012. Loss estimation pilot project for lahar hazards from Mount Rainier,
Washington: Washington Division of Geology and Earth Resources Information Circular 113, 17 p.
7