Lightning in the Peaks: How Tall Were the Peaks? : GPH 112: Intro to Phys Geography Lab (2024 Spring
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Arizona State University *
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Course
112
Subject
Geography
Date
Apr 3, 2024
Type
Pages
5
Uploaded by DoctorProtonQuetzal26
Lightning in the Peaks: How Tall Were the
Peaks? Due Feb 14 at 11:59pm
Points 3
Questions 1
Available after Jan 15 at 12am
Time Limit None
Instructions
Roughly 200,000 years ago, the San Francisco Peaks underwent a massive lateral eruption to the
northeast, similar to the lateral eruption seen in the 1980 Mount St. Helens. Today, the tallest point of
the remaining peaks stands thousands of feet shorter than the original cone. In this lab, we'll look at
estimating the height of the former San Francisco Peak before its dramatic and destructive eruption.
EXAMPLE QUESTION
: How tall was the historic San Francisco Mountain using the current mountain
slope to Agassiz Peak? First then, let's estimate the slope of this historic volcano. Go to 35.3077, -111.6898 and mark down
the elevation. Then, travel to Agassiz Peak and mark down the elevation at the top. Find the
difference.
Attempt History
Attempt
Time
Score
LATEST
Attempt 1
6 minutes
3 out of 3
Score for this quiz: 3 out of 3
Submitted Feb 14 at 12:43pm
This attempt took 6 minutes.
Question 1
3 / 3 pts
Mountain side elevation: 2724 meters
Agassiz Peak elevation: 3746 meters
Difference: 1022 meters
Now find the slope (rise over run).
If the distance between the two points is 2 kilometers, take the difference in elevation you found and
divide that by the distance to determine the slope per kilometer. Current slope from the mountain side
to Agassiz Peak = 1022 meters / 2,000 meters (2 km) = .511
Then, if the distance from Agassiz Peak to the historic peak is 1.9 kilometers, determine how many
more feet the volcano would have been if the slope was kept consistent (add the current height of
Agassiz Peak to the multiplied slope and distance to the original peak).
Ancient volcano height = current Agassiz Peak height + (slope x distance to historic peak)
Ancient volcano height = 3746 meters + (.511 x 1,900 meters)
Ancient volcano height = 3746 + 971 meters = 4717 meters or roughly 15,500 feet! To estimate the historic height of the San Francisco Mountain before its destructive eruption, we will
take the slope of the current volcano and extend that to the previous center point of the volcano. The
slope can be estimated by determining the change in height between a location along the base of the
peak, and a current high point (like Humphrey's or Agassiz Peak). Then, that slope can be applied to
the remaining distance towards the historic center of the peak. You can see an overhead view of this
idea in the image below.
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