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GOPH 375 > Chapter 7 > Flashcards

Chapter 7 Flashcards

1
Q

Locally, tsunami caused by ____ can be bigger and cause larger run-ups of water than those caused by earthquakes.

A
  • landslides
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2
Q

The magnitude 9.0 earthquake that rocked Japan on 11 March 2011, generated a (n) ____ that resulted in the deaths of over 15,000 people.

A
  • tsunami
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3
Q

Which of the following are the three ways in which volcanoes can cause tsunamis?

A
  • they explode
  • they collapse
  • they send debris into the water
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4
Q

The sequence of events (listed in chronological order) during the 1929 Grand Banks tsunami was as follows

A
  • Earthquake
  • underwater landslide
  • tsunami
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5
Q

What is the cause of most tsunamis?

A
  • earthquakes
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6
Q

Named for the Japanese words for harbour and wave, ____ are giant, long-period waves caused by oceanic disturbances.

A
  • tsunami
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7
Q

Which of the following is a typical characteristic of wind-caused waves?

A
  • breaker shape

- water run-up confined to the beach

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8
Q

When the trough of a tsunami reaches shore before the crest, a ____ will be observed.

A
  • retreat of the ocean
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9
Q

The deadliest tsunami in history occurred on 26 December 2004, in the _____ ocean.

A
  • Indian
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10
Q

Ocean bottom tsunami monitoring instruments do not get false alarms from wind-caused waves because ____.

A
  • wind-caused waves are confined to the first hundreds of metre water only
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11
Q

Waves are created when wind energy is transferred to the water surface through the force of _____.

A
  • friction
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12
Q

Which of the following are requirements for an earthquake to generate a tsunami?

A
  • must move the seafloor vertically up or down

- must have a magnitude of at least 7M

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13
Q

Which ocean is most prone to tsunamis?

A
  • Pacific Ocean
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14
Q

When waves slow down in shallow water, their wavelengths ____ and their wave heights ____.

A
  • decrease; increase
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15
Q

An oscillating wave that sloshes back and forth within an enclosed body of water is called an ____.

A
  • seiche
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16
Q

When did the 1960 Chilean tsunami reach Hawaii?

A
  • 14 hours after the earthquake
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17
Q

Seiches can be generated by ____.

A
  • earthquakes

- winds

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18
Q

What should people in coastal areas who experience a large earthquake with shaking lasting a minute or more do?

A
  • immediately evacuate to high ground
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19
Q

An event where the side of a volcano breaks off, forming a large landslide is called a ____ ____.

A
  • flank collapse
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20
Q

Which of the following are tsunami countermeasures used in Japan?

A
  • evacuation towers
  • seawalls
  • flood gates
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21
Q

In the case of a tsunami triggered by an earthquake similar to the 1700 Cascade earthquake, how long would it take for tsunami waves to reach the west coast of Vancouver Island?

A
  • approximately 15 minutes
22
Q

Tsunamis are most often generated by fault movements that have a strong component of ____ motion.

A
  • vertical
23
Q

The cataclysmic eruption of Krakatau on 27 August 1882, generated a tsunami through ____.

A
  • explosions when seawater encountered magma

- the collapse oil the volcano into the sea

24
Q

Which of the following can cause tsunamis?

A
  • underwater landslide
  • fault movement
  • meteroite impact
  • volcanic eruption
25
Q

When the 2004 Indian Ocean tsunami hit Sri Lanka, it affected almost the entire shoreline of the island. Why?

A
  • the long wavelength of the tsunami allowed it to bend around the island
26
Q

Coastal British Columbia is at the risk for what type of tsunamis?

A
  • local tsunami from earthquakes from the Cascade subduction zone
  • basin-wide tsunami from across the Pacific
  • regional tsunami from Alaska
27
Q

The earthquake that generated the 2004 Indian Ocean occurred due to subduction of the ___ plate.

A
  • Indo-Australian
28
Q

Waves will slow down when they reach water that is less than ___ deep.

A
  • one half their wavelength
29
Q

The orbital motion of water particles in water waves resembles ground motion during the passage of which seismic wave?

A
  • Rayleigh waves
30
Q

Which of the following are examples of tsunami hazard mitigation?

A
  • underwater berms

- seawalls

31
Q

A tsunami devastated Indonesia in 1883 when ____.

A
  • the volcano Krakatau erupted and collapsed into the sea.
32
Q

Fault movements, volcanic eruptions, underwater landslides, and meteorite impacts can all generate tsunami because they ____.

A
  • displace large volumes of ocean water
33
Q

An important feature of the 1964 Good Friday earthquake that led to the generation of such a large tsunami was ____.

A
  • the massive vertical and horizontal motion of the plate overlying the subjecting Pacific plate
  • the extremely long duration of shaking during the earthquake
34
Q

The 2004 Indian Ocean tsunami killed over 245,000 people in Indonesia, whereas the 2011 Japanese tsunami killed only approximately 15,000 people. Why is this?

A
  • Japan has a sophisticated tsunami warning system
35
Q

What do the tidal gauge data recorded at Port Alberni, BC following the 1964 Alaska earthquake show?

A
  • tides at Port Alberni are normally 2.5 metres high

- the height of the tsunami waves was so large that the tidal gauge went off scale

36
Q

Which of the following is evidence for ancient tsunami caused by flank collapse of the Hawaiian volcanoes?

A
  • layers of coral, marine shells, and volcanic rocks found inline and significantly above sea level
37
Q

Tsunamis often arrive as a series of several waves. Which is usually the largest?

A
  • there is no way of predicting which will be the largest wave
38
Q

Large debris avalanche deposits found on the seafloor around the Hawaiian islands have been attributed to ____ .

A
  • flank collapse of the Hawaiian volcanoes
39
Q

Where, along the coast of the Burin Peninsula, were tsunami wave heights the greatest?

A
  • in long narrow bays
40
Q

The largest wave of the tsunami caused by the 1960 Chilean earthquake was the ___ wave.

A
  • third
41
Q

What caused the spectacular seiche event at Lake Hebgen, Montana, on 17 August 1959?

A
  • downward motion on two normal faults that run across the northern end of the lake
42
Q

An example of an indirect cause of a tsunami is ____.

A
  • a submarine landslide triggered by an earthquake
43
Q

The 1964 Good Friday tsunami that raced through the entire Pacific Ocean was caused by _____.

A
  • a mega thrust earthquake along the convergent plate boundary between the Pacific and North American plates.
44
Q

The magnitude 9.1 earthquake that struck Indonesia on 26 December 2004, must have caused extensive damage. However, the extent of damage cannot be assessed because ____.

A
  • evidence of damage was washed away by the tsunami.
45
Q

Wave height in open, deep water is controlled by wind speed, the length of time the wind blows, the consistency of wind direction, and the _____.

A
  • fetch
46
Q

Landslides into bays and lakes can generate huge tsunamis of local extent. What is it about bays and lakes that allow tsunamis to be so large?

A
  • their constricted topography
47
Q

The velocity of a tsunami wave is comparable to that of ____.

A
  • a jumbo jet
48
Q

flank collapse

A
  • a catastrophic event where the side of volcano falls into the sea.
49
Q

run-up

A
  • the height above a reference level (often chosen as the main sea level) the tsunami waves reach onshore.
50
Q

Seiches

A
  • oscillating waves on a lake or landlocked sea that vary in period from a few minutes to several hours.
51
Q

shoaling

A
  • a process whereby waves coming into shallow waters are slowed by seafloor friction and become closer together and higher in amplitude.

GOPH 375 (12 decks)

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