Chapter 7 Flashcards
Locally, tsunami caused by ____ can be bigger and cause larger run-ups of water than those caused by earthquakes.
- landslides
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.
- tsunami
Which of the following are the three ways in which volcanoes can cause tsunamis?
- they explode
- they collapse
- they send debris into the water
The sequence of events (listed in chronological order) during the 1929 Grand Banks tsunami was as follows
- Earthquake
- underwater landslide
- tsunami
What is the cause of most tsunamis?
- earthquakes
Named for the Japanese words for harbour and wave, ____ are giant, long-period waves caused by oceanic disturbances.
- tsunami
Which of the following is a typical characteristic of wind-caused waves?
- breaker shape
- water run-up confined to the beach
When the trough of a tsunami reaches shore before the crest, a ____ will be observed.
- retreat of the ocean
The deadliest tsunami in history occurred on 26 December 2004, in the _____ ocean.
- Indian
Ocean bottom tsunami monitoring instruments do not get false alarms from wind-caused waves because ____.
- wind-caused waves are confined to the first hundreds of metre water only
Waves are created when wind energy is transferred to the water surface through the force of _____.
- friction
Which of the following are requirements for an earthquake to generate a tsunami?
- must move the seafloor vertically up or down
- must have a magnitude of at least 7M
Which ocean is most prone to tsunamis?
- Pacific Ocean
When waves slow down in shallow water, their wavelengths ____ and their wave heights ____.
- decrease; increase
An oscillating wave that sloshes back and forth within an enclosed body of water is called an ____.
- seiche
When did the 1960 Chilean tsunami reach Hawaii?
- 14 hours after the earthquake
Seiches can be generated by ____.
- earthquakes
- winds
What should people in coastal areas who experience a large earthquake with shaking lasting a minute or more do?
- immediately evacuate to high ground
An event where the side of a volcano breaks off, forming a large landslide is called a ____ ____.
- flank collapse
Which of the following are tsunami countermeasures used in Japan?
- evacuation towers
- seawalls
- flood gates
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?
- approximately 15 minutes
Tsunamis are most often generated by fault movements that have a strong component of ____ motion.
- vertical
The cataclysmic eruption of Krakatau on 27 August 1882, generated a tsunami through ____.
- explosions when seawater encountered magma
- the collapse oil the volcano into the sea
Which of the following can cause tsunamis?
- underwater landslide
- fault movement
- meteroite impact
- volcanic eruption
When the 2004 Indian Ocean tsunami hit Sri Lanka, it affected almost the entire shoreline of the island. Why?
- the long wavelength of the tsunami allowed it to bend around the island
Coastal British Columbia is at the risk for what type of tsunamis?
- local tsunami from earthquakes from the Cascade subduction zone
- basin-wide tsunami from across the Pacific
- regional tsunami from Alaska
The earthquake that generated the 2004 Indian Ocean occurred due to subduction of the ___ plate.
- Indo-Australian
Waves will slow down when they reach water that is less than ___ deep.
- one half their wavelength
The orbital motion of water particles in water waves resembles ground motion during the passage of which seismic wave?
- Rayleigh waves
Which of the following are examples of tsunami hazard mitigation?
- underwater berms
- seawalls
A tsunami devastated Indonesia in 1883 when ____.
- the volcano Krakatau erupted and collapsed into the sea.
Fault movements, volcanic eruptions, underwater landslides, and meteorite impacts can all generate tsunami because they ____.
- displace large volumes of ocean water
An important feature of the 1964 Good Friday earthquake that led to the generation of such a large tsunami was ____.
- the massive vertical and horizontal motion of the plate overlying the subjecting Pacific plate
- the extremely long duration of shaking during the earthquake
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?
- Japan has a sophisticated tsunami warning system
What do the tidal gauge data recorded at Port Alberni, BC following the 1964 Alaska earthquake show?
- 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
Which of the following is evidence for ancient tsunami caused by flank collapse of the Hawaiian volcanoes?
- layers of coral, marine shells, and volcanic rocks found inline and significantly above sea level
Tsunamis often arrive as a series of several waves. Which is usually the largest?
- there is no way of predicting which will be the largest wave
Large debris avalanche deposits found on the seafloor around the Hawaiian islands have been attributed to ____ .
- flank collapse of the Hawaiian volcanoes
Where, along the coast of the Burin Peninsula, were tsunami wave heights the greatest?
- in long narrow bays
The largest wave of the tsunami caused by the 1960 Chilean earthquake was the ___ wave.
- third
What caused the spectacular seiche event at Lake Hebgen, Montana, on 17 August 1959?
- downward motion on two normal faults that run across the northern end of the lake
An example of an indirect cause of a tsunami is ____.
- a submarine landslide triggered by an earthquake
The 1964 Good Friday tsunami that raced through the entire Pacific Ocean was caused by _____.
- a mega thrust earthquake along the convergent plate boundary between the Pacific and North American plates.
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 ____.
- evidence of damage was washed away by the tsunami.
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 _____.
- fetch
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?
- their constricted topography
The velocity of a tsunami wave is comparable to that of ____.
- a jumbo jet
flank collapse
- a catastrophic event where the side of volcano falls into the sea.
run-up
- the height above a reference level (often chosen as the main sea level) the tsunami waves reach onshore.
Seiches
- oscillating waves on a lake or landlocked sea that vary in period from a few minutes to several hours.
shoaling
- a process whereby waves coming into shallow waters are slowed by seafloor friction and become closer together and higher in amplitude.
