Tutorial 5
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Simon Fraser University *
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Course
312
Subject
Geography
Date
Dec 6, 2023
Type
docx
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6
Uploaded by anniesun9876
Question 1:
What kind of plate boundary exists off the east coast of Martinique? (Clicking on the
boundary will open a pop-up with some details about that boundary)
Off the east coast of Martinique, there is a subduction plate boundary.
Question 2:
Martinique is located on the Caribbean Plate, and it is situated adjacent to the South
American Plate. The Caribbean Plate is a tectonic plate in the western Atlantic Ocean.
The Caribbean Plate is moving eastward. This eastward movement is driven by the
forces of the Mid-Atlantic Ridge, where a new oceanic crust is formed, pushing the
Caribbean Plate toward the South American Plate.
To the west of Martinique is the South American Plate. The South American Plate is
one of the Earth's major tectonic plates. It includes the continent of South America and
a portion of the Atlantic Ocean floor. The South American Plate is relatively larger and
is moving westward. This westward movement is due to the subduction of the oceanic
crust of the Atlantic Plate beneath the eastern edge of the South American Plate along
the Lesser Antilles Subduction Zone.
Question 3:
Based on the type of plate boundary, what general magnitude of earthquake would you
expect is possible here?
The type of plate boundary where the Caribbean Plate and the South American Plate is
a convergent plate boundary. Its a subduction zone where the denser oceanic crust of
the Atlantic Plate is being forced beneath the lighter Caribbean Plate. Convergent plate
boundaries are known for generating powerful earthquakes. The magnitude of
earthquakes that can occur at subduction zones varies, but they can be quite
significant.
Question 4:
According to the Geologic Timescale (
here
Links to an external site.
), what time period does the Holocene epoch cover? (Hint: 'Ma' stands for 'millions of
years').
The Holocene epoch covers the time period from approximately 11,700 years ago to
the present day. It is the most recent epoch in the Earth's geological history and is
characterized by the interglacial period that followed the last glacial period, commonly
referred to as the "Ice Age."
Question 5:
How many volcanoes have erupted during the Holocene along the string of islands
between Grenada and Puerto Rico?
Question 6:
Use the Terrain Profile tool in below and draw a line exactly west/east from one coast of
the island to the other and through the peak of Mount Pelée (select metres as your
units from the drop-down menu). Take a screenshot of your topographic profile and
save it so you can upload the image in the quiz.
Question 7:
What is the maximum elevation (in metres) of Mount Pelée on your topographic profile?
1372.88016 m
Question 8:
Given the maximum elevation you measured in the previous question, the general
shape of the mountain, and the explosive character of past eruptions, what is the best
classification of volcanic type for Mount Pelee?
Mount Pelée, with its maximum elevation of approximately 1,372.88 meters (4,504 feet), is
classified as a stratovolcano or composite volcano. The general shape and characteristics of
Mount Pelée, along with the explosive nature of past eruptions, align with the characteristics of
a stratovolcano. Stratovolcanoes are typically large, steep-sided volcanic mountains with a
conical shape. They are characterized by alternating layers of lava flows, volcanic ash, and
other volcanic debris.
Question 9:
In 1902, the Capital City of Martinique, and the seat of the government was St. Pierre.
What is the current Capital City of the island?
The current capital city of Martinique is Fort-de-France. Fort-de-France is not only the
largest city on the island but also serves as its administrative, economic, and cultural
center.
Question 10:
Lahars are some of the most devastating types of volcanic hazards. Watch the
following video and explain what factors make Lahars so dangerous to those living
near a volcano.
-
Lahars can travel up to tens of kilometers, even communities far away are in
danger
-
Eruption of hot rocks can melt ice covering volcanoes that form large volumes of
water that then forms lahars
-
There are no alternatives other than evacuating buildings to higher ground,
however, lahars can bring down buildings
Question 11:
Olympic Champion Usain Bolt runs the 100 m sprint in 9.58 seconds. Would he have
been able to outrun the lahar that occurred at Mount Pelee over a 100 m course?
No because it traveled at approximately 90 km/hr, which is about 55.9 miles per hour. In
comparison, Usain Bolt's world record time in the 100-meter sprint is 9.58 seconds.
Assuming the lahar's speed remained relatively constant over the 100-meter course, it would
take the lahar just a little over 1 second (around 1.14 seconds) to cover that distance at a speed
of 90 km/hr.
Q12
Recurrence Interval = observation period / Number of Events
- The observation period is 5,000 years.
- Number of Events is 30 past eruptions.
Recurrence Interval = 5,000 years / 30 events
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Recurrence Interval ≈ 166.67 years per eruption
So, the estimated recurrence interval for eruptions at Mount Pelée over the last 5,000 years is
approximately 166.67 years per eruption.
Question 13:
Based on the lahar map above, explain how the geography of the island might create
problems for populations trying to evacuate Mount Pelee during a period of eruption.
Based on your response, explain how you think this information might be useful in
evacuation planning.
On the west side of the island, most roads do not have submersion and there are more lahars
likely to hit nearby communities. There are no evacuation routes or guidance that shows which
building roof or elevated ground people can go in the case of lahars. This information is
significantly important in evacuation planning because people may pick buildings that are in
dangerous zones near lahar or infrastructure is fairly old etc,. Another important reason is so
that when people evacuate in panic, everyone can safely reach higher grounds.
Question 14
What does the map above tell you about the minimum warning that might be
necessary for a successful evacuation of all people from around Mount Pelee?
The map shows that all residents must evacuate using a vehicle, which not everyone may have.
The minimum escape time for most of the people living near Mount Pelee requires at least 40-
60 minutes minimum to evacuate. However, all evacuation directions point to the south, which
means vehicles can be congested, delaying evacuation times to be longer.
Question 15
If the above map had more detailed information about the distribution of people across
the mapped area, how would that help define the distribution of risk faced by the local
population?
It would help define the minimum population in high risk zones and allow further
evacuation plans necessary for those zines.
Question 16
Based on the maps you have seen so far, what data is used to determine if a location is
high population risk? (there are at least two categories of data that contribute to this).
Historical data and geographic and geological data.
Question 17
Based on the maps you have seen so far, what data is used to determine if an area is
high isolation risk?
The geographical location, population density, evacuation and accessibility routes.
Question 18
Using the ashfall contours, how much ash is predicted to fall in the city of St. Pierre
(base your estimate on the value of the nearest ashfall contour)?
3 mm
Question 19
Using the ashfall contours, how much ash is predicted to fall in the city of Fort de
France (estimate the value of the ashfall based on its location halfway between the two
closest ashfall contours)?
20mm
Question 20
In both cities, the inhalation of volcanic ash can pose a risk to respiratory health. Even
a relatively thin layer of ash, such as 3 mm in St. Pierre or 20mm in Fort-de-France, can
irritate the respiratory system, leading to coughing, breathing difficulties, and other
health issues. People with pre-existing respiratory conditions are particularly
vulnerable.
In Fort-de-France, with its thicker ashfall (20mm), there is a higher risk of structural
damage to buildings and infrastructure. Heavy ash accumulation can add significant
weight to roofs, potentially causing collapses or damage to weaker structures. In St.
Pierre, the 3mm of ash is less likely to cause severe structural issues.
The thicker ashfall in Fort-de-France can disrupt transportation more severely. It can
make roads slippery, damage vehicles, and lead to the closure of airports and ports. In
St. Pierre, with a thinner layer of ash, the impact on transportation may be less severe.
Agriculture in Fort-de-France may experience greater damage due to the thicker ash
whereas St. Pierre, with its thinner ashfall, may have a milder impact on agriculture.
The economic impact on businesses, tourism, and daily activities can be more
significant in Fort-de-France due to the thicker ash. Businesses may face more
downtime, and the local economy may be more affected than in St. Pierre.
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