Geog312- Tutorial 5 Questions
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Simon Fraser University, Fraser International College *
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312
Subject
Geography
Date
Dec 6, 2023
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docx
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Uploaded by MegaFang1434
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)
-The type of plate boundary that exists off the east coast of Martinique is a convergent plate boundary
2.Martinique is located on the Caribbean Plate next to the South American Plate. Explain the relative
position of each plate and direction of movement.
-The Caribbean plate is positioned in between the North and South American plates, with the North
American plate to its north and the South American plate to the south. The plate boundary is
convergent, meaning the two plates Caribbean and South American) are moving towards each other.
However, the Caribbean plate is descending beneath it.
3.Based on the type of plate boundary, what general magnitude of earthquake would you expect is
possible here?
-Generally at convergent plate boundaries, you can expect that deep, large magnitude earthquakes are
possible. The general magnitude that I would estimate with this plate boundary would be M8 or higher,
and that is being generous I think. Martinique is found near the Lesser Antilles subduction zone, similarly
to us near the Cascadia subduction zone, and similar magnitude earthquakes should be expected.
4.According to the Geologic Timescale, what time period does the Holocene epoch cover? (Hint: 'Ma'
stands for 'millions of years').
-The Holocene epoch covers the last 2.58Ma or millions of years to the present day. We are currently still
living in the Holocene
5.How many volcanoes have erupted during the Holocene along the string of islands between Grenada
and Puerto Rico?
-This was difficult to find as I am not sure where this data is located. The map shows a number of active
Holocene volcanoes along that string of islands. I found a link that I will attach to this question as to
where I found my answer. Estimates suggest that there have been 34 historically known eruptions in the
Lesser Antilles, with 21 occurring since 1900. Nine of these have occurred from land volcanoes on
Martinique. Source:
https://uwiseismic.com/volcanoes/caribbean-volcanoes/
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.
*screenshot*
7.What is the maximum elevation (in metres) of Mount Pelée on your topographic profile?
-The maximum elevation (in metres) of Mount Pelée on my topographic profile is 1361 metres
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 Pelée?
Given the characteristics of the mountain and the explosive nature of past eruptions, I would classify
Mount Pelée as a composite or stratovolcano.
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 the island is Fort-de-France. It replaced St. Pierre after it was destroyed by the
eruption of Mount Pelée.
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 carry massive amounts of debris that can cause tremendous damages and loss of life, for
instance, boulders can be carried by lahars that are the size of cars. They can move at very high speeds
and occur in quick succession over far distances, making them difficult to escape or evacuate from.
Lahars are capable of occurring years following a volcano and without proper monitoring, can lead to
extreme damage as buildings and infrastructure do not stand much of a chance.
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 Pelée over a 100 m course?
-No, I do not think that Usain bolt could outrun the lahar that occurred at Mount Pelée. Lahars are
capable of moving much faster than Usain Bolt can. Further, debris and other material caught up in the
lahar only adds more energy and speed to it. He does not stand a chance.
12.Scientists trying to determine probability of future eruptions for a volcano often try to look at the
frequency of past eruptions. The amount of time between events is referred to as
recurrence interval
.
You can determine the recurrence interval by dividing the amount of time for which observations have
occurred by the number of events recorded in that period. At least 30 past eruptions over the last 5000
years have been identified by volcanologists working at Mount Pelée. What is the recurrence interval of
these eruptions?
-Recurrence interval = observation period/# of events recorded
Recurrence interval = 5000/30 = 166.7
The recurrence interval of these eruptions at Mount Pelée is 166.7
13.Based on the lahar map above, explain how the geography of the island might create problems for
populations trying to evacuate Mount Pelée during a period of eruption. Based on your response,
explain how you think this information might be useful in evacuation planning.
-Many of the major cities and main roads are located near the coastline of the island on low elevation.
Particularly on the western areas of the island (but also the east), the lahars, watershed and rivers lead
directly into populations near the coastline. This can be very troublesome, especially if adequate warning
for evacuation is not given to inhabitants of these cities. The lack of main roads and modes of escape
may enlighten authorities to implement new evacuation routes made specially for lahar or volcano
situations. It may also give reasoning to improve road structure, as there are still many roads throughout
the island that would be completely destroyed in the case of a lahar. Maps such as these can help
improve surrounding infrastructure to assist with better evacuation.
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 Pelée?
-The map suggests that a minimum warning of approximately 70-80 minutes would be necessary to
successfully evacuate all people from around Mount Pelée. Particularly for those in the dark purple area,
they need upwards of 60 minutes given their area, which may be difficult. This ultimately stresses the
importance of early warning signs and the proper communication of them to populations in the greatest
risk.
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?
-A map with more detailed information would provide more knowledge into which areas might need
more early warning systems or evacuation routes, infrastructure, etc. For example, an area that has
40,000 inhabitants compared to 8,000 is going to need more infrastructure to get those people
evacuated safely. There is no time for road traffic or stalls. I think more detailed maps also allow for
better allocation of resources for the most people possible.
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).
-The data that are used to determine if a location is high population risk are the amount of people in an
area and said population’s proximity to the hazard. If there are many people living in an area and that
area is close to the volcano or lahar, then it makes sense that the area is considered higher risk
compared to an area far from the volcano or lahar with less people.
17.Based on the maps you have seen so far, what data is used to determine if an area is high isolation
risk?
-The data that are used to determine is a location is high isolation risk is an area’s distance from main
roads or other evacuation infrastructure. For example, the very eastern cities are seen in red, as they are
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only stationed on a single main road that can only go one direction to safety. They could be easily
isolated is something were to go wrong in their evacuation plan.
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)?
-Based on the ashfall contours, it is predicted that there would be 300mm of ash to fall in the city of St.
Pierre as it is right along the dark red line.
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)?
-Based on the ashfall contours, it is predicted that there would be 20mm of ash to fall in the city of Fort-
de-France. I based this on it being the middle point between 2 different contour lines.
10. Based on the ashfall thickness for St. Pierre and Fort de France, explain the similarities and
differences in the actual hazards that might be produced as a result of the ashfall for the cities.
-No amount of ashfall is good for a city, but St. Pierre is going to feel much more dramatic effects with a
predicted 300mm of ashfall compared to Fort-de-France’s predicted 20mm. The physical and chemical
properties of ash can have impacts on health, environment and critical infrastructure. The production of
this much ash will destroy crops and vegetation, impair human respiratory health and function, as well as
many other things. Prolonged exposure is going to be greater for those of St. Pierre, making their risk
greater compared to Fort-de-France, but the only real difference is their proximity to the eruption.
Fortunately for Fort-de-France, they are much further away meaning they will get much less ashfall.
Additionally, large amounts of ashfall as predicted in St. Pierre can destroy buildings and homes,
particularly when wet, making cleanup a dangerous and time consuming task as it ash may remobilize
for some time following an eruption.