Download are posted - Atmospheric and Oceanic Sciences

Name:_____Solutions______Student number:____________________
ATOC 185 / EPSC 185
Natural Disasters
Mid-Term Examination, 18 October 2010, 6:30-8:30 PM
Instructions: There are 30 questions on this test. Answer your choice of any 25
questions. Each question is worth 4 points. If you answer more than 25 questions, only
the first 25 questions will be marked. All answers should be short-answer, from several
words to several sentences. Provide all answers on the test sheet itself. No aids are
allowed except for translation dictionaries. This test comprises 9 pages.
1.
Explain the following statement that we discussed in class: ‘Mother nature is
non-deterministic’.
Natural phenomena are NOT 100% predictable, or even close to being 100%
predictable.
Or
Natural phenomena are inherently unpredictable.
OR
Natural phenomena occur, without exception, as a result of a well-understood cause
(the cause-and-effect relationship).
OR
Natural phenomena predictions need to be articulated in a probabilistic manner.
2.
Define what is meant by the ‘vulnerability’ of a particular location to a natural
disaster.
Vulnerability is the potential loss, or the degree of loss, associated with a particular
event.
Name:_____________________________Student number:___________________Page 2
3.
Discuss the weather that we would expect directly in the center of the ‘eye’ of the
hurricane. Why would you expect such weather to occur?
We would expect ‘good’ or ‘fair’ weather with relatively clear skies, and subsiding
motions.
These subsiding motions are associated with the compensating downward motions
from the adjacent strong convective (thunderstorm) activity embedded in the
eyewall.
4.
Name the primary weather hazard associated with a hurricane that has moved
over land, and into the latitude (northern location) of Montreal.
Heavy rains and possible flooding.
5.
Consider the situation in which you are a resident of Vancouver in British
Columbia, along the Pacific coast of Canada. If there were a strong El Niño occurring
during the period of December, January, and February (the Northern Hemisphere winter),
what impact of this El Niño would you expect on the Vancouver winter weather?
I would expect to experience unusually warm conditions.
6.
Though ocean temperatures may be very warm in the vicinity of the equator,
would you expect hurricanes or typhoons to occur in this region? Why or why not?
No.
There is not enough of the Coriolis force to allow for the winds to rotate.
7.
Discuss one weather-related consequence of a strong El Niño along the west coast
of South America.
There would be the possibility of relatively heavy rains and flooding.
Name:_____________________________Student number:___________________Page 3
8.
In what tectonic setting are the largest and most destructive earthquakes found
and why?
-subduction zones, around the Pacific Ring of fire
-The friction from the colliding plates stores up enormous energy over time.
-The elastic rebound theory is an explanation for how energy is released
during earthquakes. As rocks on opposite sides of a fault are subjected to
force, they accumulate energy and slowly deform until their internal strength
is exceeded.
At that time, a sudden movement occurs along the fault, releasing the
accumulated energy, and the rocks snap back to their original undeformed
shape.
9.
The San Andreas, Cascadia and Quebec earthquakes are found on different
tectonic settings. Cite and explain each study case.
The San Andreas is a Transform boundary between the Pacific plate and the
North American plate. The plates are moving horizontally past each other.
Pacific plate moves northwest
North American plate moves southeast (relative to fault)
Some parts of the fault lock up and store energy
Release it in abrupt motions, large earthquakes
Other parts of the fault move smoothly
Cause ground deformation, but only small earthquakes
Cascadia Subduction Zone is a very long sloping fault that stretches from
mid-Vancouver Island to Northern California. In the Pacific Northwest, the
tectonic regime is subduction-related. Here, there is evidence for very large
earthquakes over the last several thousand years…the most recent is 300
years ago
Quebec has high levels of seismicity for a zone in the interior of a tectonic
plate
This seismicity may be related to old, aborted rifts about 200 Ma ago. Failed
rifts are ancient to modern features where continental rifting began, but then
failed to continue.
Name:_____________________________Student number:___________________Page 4
10.
Compare brittle and ductile deformation. Give examples.
Brittle deformation
Rock breaks if applied stress is too great
Rocks at or near surface (cold, low pressure) tend to deform by brittle
rupture
Object absorbs energy, exceeds elastic limit and breaks, Permanent
deformation
Exp: drop down a plate, it shatters
A crack or a fault formation
Ductile deformation:
Permanent deformation caused by flowing and folding at stresses
Above elastic limit high confining pressure and/or temperature
Warm rocks tend to deform plastically
Object absorbs, internally consumes energy, permanent deformation
Exp: squeezing clay modeling
Folds formation
Any other plausible example is acceptable
11.
Explain how liquefaction occurs in an earthquake and how it can cause damage.
Occurs on sediments during earthquake shaking. Groundwater can move
upwards due to the shaking. Water lubricates contact between sediment
grains. Weakens sediments.
Liquefaction has two consequences
Amplifies shaking in structures
Causes buildings to sink into sediment
12.
Why are Mauna Loa and Kilauea in the Hawaiian Islands the best example of
intraplate volcanism? How do they form?
Mauna Loa and Kilauea in the Hawaiian Islands the best example of
intraplate volcanism because they are still actives. More lava is extruded here
constantly than anywhere else on Earth.
Basaltic magmas at hot spots are derived from deep within the mantle to form shield
volcanoes. The magmas are fed by deep mantle plumes which are stationary relative
to the drifting tectonic plates. This causes the original volcano to become extinct
when its move cuts it off from its magma source and an island is born. A new
volcano will then form above the hot spot again. This process repeats as the plate
moves and a string of volcanoes (and eventually, islands) will dot the surface of the
plate as the movement continues away from the hot spot.
Name:_____________________________Student number:___________________Page 5
13.
What are the main factors that influence the explosivity of magmas?
•
Three factors affect the explosivity of a volcano
– Temperature of magma
• High-temperature, less explosive
– Composition of magma
• Less silica, less explosive
– Gas content of magma
• Less gas, less explosive
Viscosity and gas content are also acceptable answers.
•
–
14.
Explain the difference between a lava flow and a pyroclastic flow. Why are lava
flows generally not dangerous, but pyroclastic flows are?
•
Pyroclastic flows are suspensions of hot pyroclastic material, air, and gas
which descend under the influence of gravity. Their velocity is generally very
high (50-500 km/hr) and their temperature can attain 1000 C. These flows
can incinerate everything in their path.
•
•
A lava flow is a moving outpouring of molten rock, which is created during a
non-explosive effusive eruption. Due to its low silica content and high
temperature, it is quite fluid (but stickier than maple syrup), yet lava usually
flows fairly slowly and can be diverted.
Name:_____________________________Student number:___________________Page 6
15.
Sketch normal and reverse faults. How do these two faults form?
A normal fault is the result of tensional forces (e.g., rifting)
Reverse and thrust faults are the result of horizontal compression
16.
Hot spots are responsible for both Yellowstone and Hawaii volcanism. How those
two types of volcanism differ and why ?
The Yellowstone hot spot is beneath a continental crust. Melting of that crust will
generate a viscous magama----more gases----gases can not escape or flow out--energy build up inside the magma chamber----fissures---magma chamber will
empty= Caldera formation
Hawaii hot spot forms beneath an oceanic plate---basalt generation---less viscous--less gas---lava flowing out easily----Shield volcanoes.
Name:_____________________________Student number:___________________Page 7
17.
What is a lahar? Explain the concept of bulking of lahars.
A lahar is a fast, liquid flow arising when a pyroclastic flow mixes with water from
snow fields or nearby streams or rivers.
As they progress, lahars can undergo a process called “bulking”---Incorporate
material from the area they flow over------Erode sides of existing drainage channel
18.
Contrast an island volcanic arc with a continental volcanic arc.
In an island volcanic arc, the overriding plate at the subduction zone is composed of
oceanic lithosphere. Resultant volcanism produces an island chain dominated by
basalt (e.g. Aleutians)
In continental volcanic arc, the overriding plate is continental lithosphere. A chain
of terrestrial volcanoes extruding andesitic lava is produced.
19.
Why was the 1906 San Francisco earthquake so destructive?
The 1906 San Francisco earthquake was caused by a rupture on the San Andreas
Fault, a continental transform fault that forms part of the boundary between the
Pacific Plate and the North American Plate
As damaging as the earthquake and its aftershocks were, the fires that burned out
of control afterward were even more destructive. It has been estimated that up to
90% of the total destruction was the result of the subsequent fire
Damage to water mains prevents or hinders fire fighting efforts
20.
Describe the two types of faults which generate destructive earthquakes in the Los
Angeles area, as discussed in the movie, “Killer Quake”.
Strike slip fault:
One of the major faults is the San Andreas Fault. Located at the boundary between
the Pacific Plate and the North American Plate.
Blind thrust fault:
A shallow-dipping reverse fault which terminates before it reaches the surface.
When it breaks, therefore, it may produce uplift, but never any clear surface
rupture. Many still-unknown blind thrust faults may exist in southern California.
Name:_____________________________Student number:___________________Page 8
21.
Why are earthquakes along subduction zones more violent than those along
divergent margins? Explain
-Under compression rocks are very strong---store more energy over time---rocks
overcome the elastic limit and break---energy release
-under tension rocks are very weak------less energy stored with time---the elastic
limit is overcome in a short time----rupture----energy release
22.
Describe the differences between shield volcanoes and stratovolcanoes. How are
these differences explained by the composition of their lavas?
Shield volcanoes are gently sloped domes typically composed of basaltic volcanic
rock. The lava that forms these rocks is of low viscosity, so it flows easily.
Stratovolcanoes or composite volcanoes are large conic volcanoes. They are the
result of multiple eruptions, which have in turn produced both effusive lava and
pyroclastics.
23. Name at least two reasons why most of the Atlantic Ocean’s easterly waves do not
evolve into hurricanes.
Take two:
There is usually strong descending air producing an inversion, inhibiting
thunderstorms.
Vertical wind shear destroys the tendency for the cloud systems to stay together.
The middle layers of the atmosphere are too dry for the cloud systems to be
maintained.
24. Why is it that we need very warm sea-surface temperatures for hurricanes to form?
Increasingly warm sea-surface temperatures allow for more latent heat of
condensation. This latent heating is the essential process by which hurricanes form.
25. During an extremely strong El Niño event, would you expect any hurricanes to form
along the west coast of South America? Why or why not?
No. The sea-surface temperatures, though unusually warm, are still too cold for
hurricanes to form.
Name:_____________________________Student number:___________________Page 9
26. Define a ‘storm surge’. What atmospheric (meteorological) processes are
responsible for storm surges?
It is a 8-160 km wide dome of water that sweeps over the coastline during the
hurricane’s landfall.
Strong onshore winds and relatively low air pressure are responsible for a storm
surge.
27. Assume a north-south oriented coastline, such as that of the North American east
coast. If an Atlantic Ocean hurricane is travelling directly into the coastline from the
east, where with respect to the hurricane center, would you expect to see the most
coastline damage or impact of that hurricane upon landfall? Explain your reasoning, with
a sketch.
Most of the damage occurs to the right of track. The reasoning is that the strongest
winds impacting land are to the right (north) of track, because of the onshore (less
friction) component, and that the wind is travelling with (not against) the movement
of the storm.
Name:_____________________________Student number:___________________
Page 10
28. Discuss the relationship of the Southern Oscillation to El Niño?
During the negative phase of the Southern Oscillation, when the pressures are
relatively low in the vicinity of Tahiti, there is an El Nino. This is associated with
either weaker than average easterly winds, or actual westerlies in response to an
unusually strong west-to-east pressure gradient.
29. The typical winds that occur over the tropical waters of the Pacific Ocean are easterly
(winds from the east). Discuss the consequences of these winds shifting to westerly (from
the west) on the state of the ocean along the west coast of South America.
As the atmospheric westerlies arise over the ocean, the currents respond with
westerlies, allowing for the warm waters in the west to be transported to the east,
thereby providing unusually warm water in the central and eastern regions. This
transport of warmer waters to the east also tends to suppress the upwelling of cold
water in the eastern and central parts of the ocean.
30. Define the La Niña phenomenon. What weather-related consequence would you
expect to see in northern Australia and in Indonesia?
Take one:
1. La Nina is the opposite of El Nino, namely, with unusually warm oceans in the
western Pacific and unusually cold waters in the eastern Pacific.
2. La Nina is also characterized by unusually low pressures in the western part of
the ocean, and unusually high pressure in the eastern/central part of the Pacific
Ocean.
3. La Nina is also associated with unusually strong easterly trade winds across the
tropical Pacific.
4. We should expect to see heavy rains and flooding in northern Australia and
Indonesia.
Name:_____________________________Student number:___________________
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