Quiz 2 week #7
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El Paso Community College *
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Course
2
Subject
Geology
Date
Dec 6, 2023
Type
docx
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Uploaded by essm8163
QUIZ #2.
Answer all questions and turn in on Blackboard.
What is your name? Elmer Saenz
1.
(1 point) Which of the three main classes of stress would cause the clay layers to deform this way?
Compressional Stress
2.
What is the name of the structure shown in the image below, inside the black circle drawn onto the
photograph? (1 point)
Anticline Structure
3.
(6 points, one point per row)
Fill in the chart below. It compares types of plate boundaries with the
features and common hazards found there. You can mark an X in each box where it applies. (For
example, if there are earthquakes at a boundary where two oceanic plates diverge, mark an X in that
box)
Two oceanic
plates
converge
Two oceanic
plates
diverge
Two
continental
plates
converge
Two
continental
plates diverge
An oceanic
plate and a
continental
plate
converge
Two plates
slide past
each other
Earthquakes
x
x
x
x
x
x
Tsunamis
x
x
Volcanoes
x
x
Mountains
that
aren’t
volcanoes
x
x
Ridge made of
volcanoes in
the ocean
x
Deep trench in
the ocean
x
3. Volcano Scenario
Volcano X is a very active volcano in Central America.
It is formed by the subduction of the Cocos Plate under
the Caribbean Plate.
Rock layers on this large, steep sided (steeply sloping) volcano have been identified as
andesite, which is
relatively high in viscosity.
The seismic activity at Volcano X has been increasing in
frequency, intensity and magnitude.
Scientists are concerned that an eruption may be imminent.
Because of your knowledge of earth science, your friend who lives about 20 kilometers from the volcano has
asked you for advice.
They want to know some things about Volcano X and what types of hazards they may
expect from Volcano X.
A (1 point). What type of volcano (think of the three main classes of volcanoes) is Volcano X?
Explain your
reasoning (need explanation for full credit). (
Volcano X is a
composite or stratovolcanoe
.
Composite
volcanoes are also known as stratovolcanoes or stratocones. They are the most common type of volcano and are
formed by the eruption of viscous lava and ash. Composite volcanoes are typically steep-sided and conical in
shape, with a central vent.
Volcano X is described as being steep-sided and having erupted andesite lava. Andesite is a type of lava that is
relatively high in silica, which makes it viscous. This suggests that Volcano X is a composite volcano.)
B (1 point).
It is stated above that the Volcano X region is characterized by the subduction of the Cocos Plate
under the Caribbean plate.
Given that it represents a subduction zone, which of the following observations
would be most likely to happen in regards to the faults in the region when earthquakes happen on them?
(a)
Hanging wall moves up
(b)
Hanging wall drops down
(c)
Hanging wall and footwall move side-to-side laterally with regards to each other.
D. (1 point per answer) Your friend asks you which types of volcanic hazards they should prepare for from
this volcano.
Answer yes or no for each item below BUT ALSO EXPLAIN YOUR REASONING (you must give
an explanation for full credit).
1. Volcanic ash clouds in the sky and falling out over the area
Yes
. Composite volcanoes are known for producing explosive eruptions that can generate large ash clouds. Ash clouds can
travel long distances and can cause a number of hazards, including respiratory problems, damage to crops and
infrastructure, and disruptions to air travel.
2. Smooth, very liquid, black lava flows running down from the mountain
No
. Composite volcanoes typically erupt viscous lava that does not flow very easily. This type of lava is more likely to
form lava domes and pyroclastic flows, which are fast-moving mixtures of hot gas and rock.
3. Explosive eruption blast
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Yes
. Composite volcanoes are known for producing explosive eruptions. Explosive eruptions can generate powerful
shockwaves and pyroclastic flows.
4.
The image below, obtained near the bottom of the Grand Canyon, shows a quartz vein that has been
deformed.
(a)
(1 point) Which class of deformation caused the quartz vein to change shape?
The quartz vein in the
image shows evidence of
ductile deformation
. This is because the quartz has been stretched and folded into a
curved shape, without breaking. Ductile deformation occurs when rocks are subjected to high temperatures and
pressures over a long period of time. This causes the rocks to become more pliable and less likely to break.
(b)
(1 point) Did this deformation most likely occur near Earth’s surface or deep inside the Earth?
The fact
that the quartz vein has been deformed I think this suggests that it was subjected to high temperatures and
pressures at some point in its history. This is more likely to have happened at
great depth,
where the rocks are
hotter and under more pressure. Therefore, the deformation of the quartz vein most likely occurred at great depth.
5.
The cartoon below, from your book, illustrates the tectonic setting of East Africa.
For 1 point, what
class of plate boundary/plate margin formed these structures?
Be as specific as possible.
In summary, it is mostly understood that the East African Rift Valley was formed due to the pulling apart of the
African Plate and the Somali Plate along a divergent plate boundary
. This process led to the gradual thinning of
the lithosphere, upwelling of magma, and the creation of new crust, resulting in the unique geological features we
can observe in the picture.
6. (1 point) An earthquake strikes El Paso one morning at 7 AM!
The city shakes, items are thrown off
of shelves, and cracks appear in some houses.
It seems to be the only thing that people want to talk
about.
Later that day, you see several friends of yours and everyone discusses the earthquake.
One of
them says, “Yeah, they said that here on the far east side it was 4 on the Richter scale, it was a big
shake but not too bad, but I hear the worst damage was up by Transmountain, over there it hit
magnitude 6.”
What was incorrect about your friend’s statement?
Explain.
I think my friend’s statement was incorrect because the Richter scale is not a measure of the intensity of
an earthquake at different locations, but a measure of the magnitude of an earthquake at wherever it was.
The magnitude is the same for all locations, but the intensity may vary depending on the distance from
the epicenter, the local geology, and other well known factors.