Unit 10 Laboratory Activity_Topographic Maps
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Geography
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Dec 6, 2023
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Using Topographic Maps
Assignment Open up the Mt. St. Helens 7.5 Minute Series Topographic Map located here. A good site to use might also be Science Explorer site on USGS here. If the links aren’t working then try googling Mt. St. Helens 7.5 minute topo map. Make sure it’s dated at 2017. Thank you. 1.
This is a topographic map of the Mt St. Helens area. What state is it located in? Washington 2.
What year was this map completed? 2017 3.
If I wanted to look at a topographic map of the landscape directly to the north of this map, which map would I request from the USGS? You must be looking at the USGS map near the bottom to find this answer. Spirit Lake West 4.
What magnetic declination does this map report (hint: look at the text in the bottom left-hand side of your map)? For what year was this declination used? Magnetic declination is 15°29' East, in 2017
5.
Calculate and report the magnetic declination for this area today by using NOAA’s online calculator
. Input the zip code for this area – 98601. Then click ‘Calculate’. 6.
What is the fractional scale of the map? 1/24,000 7.
Complete the following scale questions (
show all work in your submission
): a.
1 inch on the map = ____24,000___________ inches on the ground b.
1 inch on the map = ____2,000___________ feet on the ground c.
1 inch on the map= ____0.379____________ miles on the ground 8.
What is the latitude of the northern boundary of this map? 46° 15'
9.
What is the latitude of the southern boundary of this map? 46° 07'30''
10. How many minutes of latitude are represented by this map (hint: subtract your answers from #8 and 9)? 8’30” 11. What is the contour interval for this map (Hint: look under the graphic scale bar)? 40 ft
12. Locate Swift Creek in the southern, central part of the map. Which direction does Swift Creek flow? What information on the map helped you to determine this? It’s going downstream because the elevation on the map indicates it’s flowing downstream from a mountain. 13. Which area of the map will have steeper topography, the Pumice Plain (located in the northern central portion of the map) or Studebaker Ridge (just to the west of the Pumice Plain)? What information helped you to decide? The closer the contour lines the steeper the place is so the Studebaker ridge should have a steeper topography. 14. Watch this 7:30 minute USGS video describing the 1980 Mt St Helens eruption. Briefly summarize this eruption in terms of timing, which area(s) around the volcano were affected, and the permanent consequences of the event. Sunday 8:32 am, on the Northside of the mountain. Destroyed 230 sq, miles and killed every living thing and killed acres of forest within a span of 5-9 minutes. Also killed over 50 people. 15. Find the lava dome in the center of Mt. St. Helens in the map. What is the highest elevation of the lava dome (in feet)? 6,400 ft Next, Go to this Link
, click on the map of Mt. St. Helens, it’ll get a little larger. Use the cursor to hover over the lower right corner of the map. 4 arrows pointing away from each other will appear, click on them and the image will get bigger. Now answer question 16 - 18 16. Find the red ‘33’ just to the north of the lava dome. What is the elevation of the land beneath the red ‘33’? Link ≅
5,160ft
17. Using the graphic scale bar, measure the distance (in miles) between the lava dome (measure from the center) and the land beneath the red ‘33’. Be as exact as possible – it might be easiest to literally mark the distance on a slip of paper you hold up to your screen. Without changing the zoom, toggle down, and put your marked paper on the scale bar and measure the distance. 1.37 miles 18. Using the data that you’ve collected in #15-17, calculate the slope (gradient) in of the landscape (in feet/
mile) between the lava dome and the land beneath the red ‘33’. Difference in elevation= 6306.66-5140=1166ft
so the Gradient=1166ft/1.37miles=851.09ft/mi
19. What specific evidence do you see on the topographic map for the *direction* of the 1980 eruption noted in the video?
The contour lines on the North are wider apart showing the topography was hugely affected after the eruption of 1980. 20. What does the presence of a lava dome in the crater indicate (keep in mind that this map was created after the 1980 eruption)? There must have been another eruption that formed a new lava dome. 21. What type of volcano (composite, shield, cinder cone) is Mt. St. Helens? What is your evidence? Composite due to the nature of the eruption and indication of pressure under the surface that made the eruption so explosive. 22. Note the glaciers that surround the peak of Mt. St. Helens. If these glaciers were to melt during an eruption, what type of volcanic hazard could occur? Lahars
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