M6a GLG
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School
Pima Community College *
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Course
101
Subject
Geology
Date
Dec 6, 2023
Type
Pages
7
Uploaded by HighnessVulture3729
Devil’s Tower
Where is the park located (e.g. near which city, state, or specific region of the country?)
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Wyoming
In 2 - 3 sentences, describe the central volcanic feature in the park. Is it an active, dormant, or
extinct volcanic site, or is it another type of feature? If it is a volcano, what type of volcano is it
(shield, stratovolcano, cinder cone, caldera, etc.)? If it is an active volcanic site, what specific
type of volcanic activity does the USGS photo tour depict to help you determine this? (Include a
screenshot of this activity from the photo tour where applicable.)
-
The Devil’s Tower is a large, nearly vertical, very cylindrical mountain that towers above
the surrounding landscape. It is not a volcano, but some believe that it was a volcanic
plug at one point. (nps.gov).
In 2 - 3 sentences, please describe the tectonic processes that resulted in the volcanic feature(s) in
the park. For example, was the volcanic feature a result of activity at a plate boundary, a hot spot,
or some other activity?
-
The prevailing theory is that the Devil’s tower formed as a result of igneous intrusion,
wherein magma squeezes between layers of sedimentary rock and cools. (nps.gov)
In 2 - 3 sentences, please give your own assessment of what type of melt process is occurring at
each location. Is there more than one type of melt? Use the information you have learned in the
text and from the excerpt above on How Rocks Melt.
-
Given that the Devil’s Tower is pretty far inland, I think that it’s the result of a hotspot.
I’m also more inclined to believe that it’s an igneous intrusion rather than a volcanic plug.
For that reason, I think that the magma is a result of pressure-related melting.
Crater Lake
Where is the park located (e.g. near which city, state, or specific region of the country?)
-
Oregon
In 2 - 3 sentences, describe the central volcanic feature in the park. Is it an active, dormant, or
extinct volcanic site, or is it another type of feature? If it is a volcano, what type of volcano is it
(shield, stratovolcano, cinder cone, caldera, etc.)? If it is an active volcanic site, what specific
type of volcanic activity does the USGS photo tour depict to help you determine this? (Include a
screenshot of this activity from the photo tour where applicable.)
-
Crater lake is a caldera that is filled with water. It is not an active volcano, but it was at
one point. We know that it isn’t an active volcano because the caldera could only have
formed after its magma reservoir emptied via eruption. (nps.gov)
In 2 - 3 sentences, please describe the tectonic processes that resulted in the volcanic feature(s) in
the park. For example, was the volcanic feature a result of activity at a plate boundary, a hot spot,
or some other activity?
-
Mount Mazama (the volcano that collapsed to form the Crater Lake caldera) is part of the
Cascade volcanic arc. These volcanoes formed as a result of sitting near a plate boundary,
above a subduction zone.
In 2 - 3 sentences, please give your own assessment of what type of melt process is occurring at
each location. Is there more than one type of melt? Use the information you have learned in the
text and from the excerpt above on How Rocks Melt.
-
Given that Crater Lake sits on a subduction zone, the rock likely melted as a result of
temperature increasing.
Mount St. Helens
Where is the park located (e.g. near which city, state, or specific region of the country?)
-
Washington
In 2 - 3 sentences, describe the central volcanic feature in the park. Is it an active, dormant, or
extinct volcanic site, or is it another type of feature? If it is a volcano, what type of volcano is it
(shield, stratovolcano, cinder cone, caldera, etc.)? If it is an active volcanic site, what specific
type of volcanic activity does the USGS photo tour depict to help you determine this? (Include a
screenshot of this activity from the photo tour where applicable.)
-
Mt. St. Helens is an active stratovolcano. USGS has several different seismic stations
located around the park to detect earthquakes (and potential eruptions). The one pictured
below is at Yellow Rock.
In 2 - 3 sentences, please describe the
tectonic processes that resulted in the
volcanic feature(s) in the park. For
example, was the volcanic feature a result
of activity at a plate boundary, a hot spot,
or some other activity?
-
Mount St. Helens is part of the Cascade volcanic arc, and sits above a subduction zone.
It’s quite similar to Mt. Mazama, which formed Crater Lake. (nps.gov).
In 2 - 3 sentences, please give your own assessment of what type of melt process is occurring at
each location. Is there more than one type of melt? Use the information you have learned in the
text and from the excerpt above on How Rocks Melt.
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-
Similar to Crater Lake, I believe that rock is melted in the subduction zone as a result of
heat and pressure, due to the lowered melting temperature caused by the presence of
water at the subduction zone.
Yellowstone
Where is the park located (e.g. near which city, state, or specific region of the country?)
-
Wyoming
In 2 - 3 sentences, describe the central volcanic feature in the park. Is it an active, dormant, or
extinct volcanic site, or is it another type of feature? If it is a volcano, what type of volcano is it
(shield, stratovolcano, cinder cone, caldera, etc.)? If it is an active volcanic site, what specific
type of volcanic activity does the USGS photo tour depict to help you determine this? (Include a
screenshot of this activity from the photo tour where applicable.)
-
Yellowstone is situated over a supervolcano, but is also a caldera (which resulted from
previous eruptions of the supervolcano that Yellowstone sits on), similar to crater lake. It
is dormant, with low levels of unrest. Its activity is documented monthly at
https://www.usgs.gov/programs/VHP/volcano-updates#yvo.
In 2 - 3 sentences, please describe the tectonic processes that resulted in the volcanic feature(s) in
the park. For example, was the volcanic feature a result of activity at a plate boundary, a hot spot,
or some other activity?
-
During the time that Yellowstone’s mountains were forming, the region of the United
States that it exists in was underwater. We also know that they were formed by a hotspot,
so they’re fairly similar in formation to the islands of Hawaii.
In 2 - 3 sentences, please give your own assessment of what type of melt process is occurring at
each location. Is there more than one type of melt? Use the information you have learned in the
text and from the excerpt above on How Rocks Melt.
-
Yellowstone’s supervolcano formed because of a hotspot, so I believe that the magma
that once filled it melted due to a decrease in pressure.
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What specific questions arose while you researched each feature, and were you able to find
satisfactory answers to address your curiosity?
I still would like to know more about how the Devil’s Tower formed, since there are so
many plausible theories. Nobody seems to know definitively, which is to be expected, because
nobody was around to watch it form (not that it would have been explicitly visible depending on
what happened). At the very least I am intrigued by it and am interested to see what information
and theories geologists come up with in the future, and I’m at peace with not being the only
person who doesn’t know for sure how it formed.
I remember watching a documentary about the Yellowstone supervolcano when I was
little, and being terrified that it could erupt at any moment. Based on the fact that it hasn’t
erupted since I’ve been alive, and the usgs records very little activity from it, I don’t particularly
believe that we’re situated above a ticking bomb, as the documentary suggested.