Movie Quiz 3
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University of Guelph *
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2240
Subject
Geography
Date
Dec 6, 2023
Type
docx
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2
Uploaded by BaronFlamingoPerson819
New Madrid Earthquakes (Due Monday, Oct 9, by 11:59 pm)
https://vimeo.com/38864818
Name and student ID__________1145966___________________________
1.
Describe seismic activity around small town of New Madrid in 1811-1812.
How many major and
minor earthquakes occurred?
There were four big earthquakes occurred on Dec 16
th
, 1811 2:15 a.m., Dec 16
th
, 1811 8:00 a.m., Jan 23
rd
,
1812 and Feb 7
th
, 1812. In between these large earthquakes, New Madrid was shaken by smaller
aftershocks.
2.
List five consequences of 1811-1812 New Madrid earthquakes in addition
to property destruction
& loss of life.
The earthquake created a fault in the middle of the Mississippi River that lifted the riverbed and created
the waterfall. At the same time a semicircular area opened up to the south and was flooded by the river.
Buildings in Madrid's city center also received varying degrees of damage from the quake.
3.
Explain how
sand boils
form.
How do scientists use
fossil sand boils
to reconstruct previous
earthquake history of the area? How often did major earthquakes in this area occur?
The water pressure between the sand grains increases as the earth trembles because the water-soaked sand
grains move and compress. Sand and silt are carried along by the pressured water as it finds the route of
least resistance and emerges to the surface through fissures or other weak spots. These mixes create
"boils" at the surface, which seem like little wet sand volcanoes. The sediments in these sand boils may be
dated, which allows scientists to determine when previous earthquakes have place.
Earthquakes do not
normally occur in the Madrid area.
4.
What is the probability of a major earthquake in this area in the next 50 years? Why are scientists,
emergency agencies and state & local governments so concerned about possible future
earthquake?
The probability of an earthquake of magnitude 7 occurring in the next 50 years is 7-10%. The probability
of a magnitude 6 earthquake is 25-40%. The reason scientists and society are so concerned is that an
earthquake of this magnitude could cause more than 86,000 casualties and tens of billions of dollars in
economic damage.
5.
Explain the differences between New Madrid earthquakes and earthquakes of similar magnitude
in California.
The California earthquake is because the rock under the ground is hot and loose, making it difficult
for the energy to be transmitted far away. The rock formations beneath the Madrid earthquake belt are
cold and hard, which made the quake felt in cities across the eastern United States. At the same time,
Madrid is located in the middle of a continental plate and should not be a high seismic zone.
California, by contrast, sits on a plate fault and is itself vulnerable to earthquakes caused by
continental plates pushing against each other.
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