Lesson 4: Tsunami Flashcards
In _____ a magnitude _____ earthquake off the Indonesian coast generated a tsunami that swept across the Indian Ocean, killing an estimated ______ people. The city of _____, was the closest to the epicenter, provide a dramatic testament to the devastating power of the waves.
2004;
9.1;
225,000;
Banda Aceh
a very long-wavelength wave of water that is generated by sudden displacement of the seafloor or disruption of any body of standing water.
tsunami
tsunamis are sometimes called as ?
“seismic sea waves”
tsunamis occur ______, often without ______. they are extremely dangerous to ________
suddenly;
warning;
coastal communities
5 characteristics of all types of waves
- wavelength
- wave height
- amplitude
- frequency or period
- velocity
Distance between wave crests and wave troughs
wavelength
Normal ocean waves have wavelengths of about _____, while tsunami have wavelengths up to _____
100m;
500km
The rate at which a wave loses its energy is ______ related to its wavelength
inversely
refers to the distance between the trough of the wave and the crest of the wave
Wave Height
height of the wave above the still water line, usually equal to 1/2 the wave height
Wave Amplitude
amount of time it takes for one full wavelength to pass a stationary point
Wave Frequency or Period
wind-generated waves usually have period (time between two successive waves) of _____
5-20 seconds
A tsunami can have a period in the range of ______
10 mins to 2 hours
Velocities of normal ocean waves are about ___, tsunamis have velocities up to___
90 km/hr;
950 km/hr (about as fast as jet airplanes), move much more rapidly across ocean basins
is equal to the wavelength divided by the wave period
wave velocity
When the ocean is 6100 m deep, a tsunami will travel about _____, and thus can travel across the Pacific Ocean in less than one day
890 km/hr
If the trough of the tsunami wave reaches the coast first, this causes a phenomenon called _____, where it appears that sea level has _____ considerably.
drawdown;
dropped
When the crest of the wave hits, sea level _____ (called _____)
rises;
run-up
T or F: one coastal area may see no damaging wave activity while in another area destructive waves can be large and violent.
True
4 ways Tsunamis can be generated
- volcanic eruptions
- landslides
- underwater explosions
- meteorite impacts
_____ cause tsunami by causing a disturbance of the seafloor
Earthquakes
3 controlling factors of earthquake-induced tsunami occurrence
- epicenter
- magnitude
- type of displacement
Most tsunami are generated by _______ that occur along the _______, along the _______.
earthquakes;
subduction boundaries of plates;
oceanic trenches
process of how tsunamis are generated in subduction zones
- in subduction zones
- plates get stuck, the overriding plate gets distorted (buckled)
- stuck area ruptures, triggering an earthquake and pushing up the ocean floor and sea water above
- this starts the tsunami, which moves in the opposite direction
date, magnitude and setting of the Indian Ocean tsunami
- date: December 24, 2004
- magnitude: Mw 9.1
- setting: oceanic trench off the coast of Sumatra, Indonesia
date, magnitude and setting of the Alaskan Tsunami
- date: April 1, 1946
- magnitude: Mw 7.3 earthquake
- setting: earthquake occurred near Unimak Island in the Aleutian Islands, west of Alaske, near the Alaska
Trench
Sediment accumulating in the trench slumped into
the trench and generated a tsunami
date, magnitude and setting of the valdivia earthquake and tsunami
May 22, 1960
Mw 9.5 earthquake occurred along the subduction zone off South America
the Valdivia Earthquake was aka ?
Great Chilean Earthquake
T or F: population of Chile is familiar with earthquakes and potential tsunami, most people along the coast moved to higher ground
True
In the 1960 Valdivia Tsunami:
- first tsunami wave: had a run-up of ____ which hit _____.
about 1 hr. later,
- the second wave: traveling at a velocity of ______ crashed in with a run-up of _____.
- a third wave: traveling at only _____ that crashed in later with a run-up of _____.
4.5 m;
the coast of Chile;
166 km/hr;
8 m
83 km/hr
11 m
casualties of the Great Chilean Earthquake and Tsunami
909 dead with 834 missing
date, magnitude, setting and effect of the Good Friday Earthquake in Alaska
- date: March 27, 1964
- magnitude: Mw 9.2 earthquake
- setting: occurred along the subduction zone off of Alaska
- effect: caused deformation of the crust where huge blocks were dropped down as much as 2.3 m. Sediment accumulating in the trench slumped into the trench and generated a tsunami
date, magnitude and setting of the Moro Gulf Earthquake
- date: August 17, 1976
- magnitude: Mw 8.1 earthquake
- setting: generated along the Cotabato Trench
wave height of Moro Gulf Earthquake
Up to 4.5-meter high waves
the Moro Gulf Earthquake devastated more than ______ of coastline bordering _______ in the _______.
700 km;
Moro gulf;
North Celebes Sea
casualties of Moro Gulf Earthquake in region 9: dead, missing, injured and homeless?
dead: 1440
missing: 909
injured: 7701
homeless: 49 848
casualties of Moro Gulf Earthquake in region 12: dead, missing, injured and homeless?
dead: 3351
missing: 1379
injured: 2227
homeless: 43 534
T or F: Volcanoes that occur along coastal zones can cause several effects that might generate a tsunami.
True
Explosive eruptions can rapidly emplace ________ into the water. ________ produced by eruptions can rapidly move into water, and _______ to form ______ can suddenly displace the water.
pyroclastic flows;
landslides and debris avalanches;
collapse of volcanoes;
calderas
example of volcanic eruption that generated a tsunami
what: The eruption of Krakatau
when: 1883
where: in the Straights of Sunda, between Java and Sumatra
how: generated at least three tsunami that killed 36,417 people
how did the eruption of krakatau exactly cause a tsunami?
still uncertain, but several events during the eruption could have caused it including:
- a large Plinian eruption column blasted pumice and ash up to 40 km into the atmosphere
- a loud explosive blast was heard as far away as Australia
- At some point during the eruption, a caldera formed by collapse of the volcanic island
- submarine earthquakes could have caused a tsunami
example of landslide that generated a tsunami
what where: Debris avalanche fell into Lituya Bay, Alaska
when: 1958
how: the avalanche caused a wave with a run-up of about 60m as measured by a zone completely stripped of vegetation
what causes landslides that cause tsunamis?
earthquakes or volcanic eruptions
example of underwater explosion induced tsunamis
what: Nuclear testing by the United States
where: Bikini Atoll in Marshall Islands
when: in the 1940s and 1950s
how: generated up to 30-m high tsunamis
While no historic examples of meteorite impacts are known to have produced a tsunami, the apparent impact of a meteorite at the end of the _______ period, about _______ yrs ago, near the tip of what is now the ________, produced a tsunami that left deposits all along the Gulf coast of Mexico and the United States.
Cretaceous;
65 million;
Yucatan Peninsula of Mexico
For areas located ______ from earthquakes that could potentially generate a tsunami, there is usually plenty of time for _____ and ______, even though tsunami travel at high velocities across the oceans.
at great distances;
warnings to be sent;
coastal areas evacuated
where is a good example of an area located far from most of the sources of tsunami, where early warning is possible and has saved lives.
Hawaii and Japan
NOAA
National Oceanic and Atmospheric
Administration
full NOAA
National Oceanic and Atmospheric Administration
NOAA has set up a Pacific warning system for areas in the Pacific Ocean, called ?
Pacific Tsunami Warning Center
the Pacific Tsunami Warning Center consists of an international network of _______ and _____ around the Pacific basin that can all send information via _____ to the _____.
seismographic stations;
tidal stations;
satellite;
Center
Center of Pacific Tsunami Warning Center is located in ?
Hawaii
Tsunami warning centers in ______ and Hawaii ________ for earthquakes that might generate a tsunami and _______
Alaska;
monitor the globe;
issue warning guidance
In order to be able to issue warnings about tsunami generated within _____ of an earthquake, several ______ have been set up in areas prone to tsunami generating earthquakes.
100 to 750 km;
regional warning centers
example of regional warning systems that have been successful at saving lives
- before the Japanese warning system was established, 14 tsunamis killed over 6000 people in Japan.
- Since the establishment of the warning system, 20 tsunami have killed only 215 people in Japan
7 tsunami safety rules
Keep calm and move to higher ground
- Stay out of danger until an “all clear” is issued by a competent authority
- approaching tsunami are sometimes heralded by noticeable rise or fall of coastal waters
- Never go down to the beach to watch for a tsunami!
- the upper floors of high, multi-story, reinforced concrete hotels can provide refuge if there is no time to quickly move inland or to higher ground.
- If you are on a boat or ship and there is time, move your vessel to deeper water
- Stay tuned on credible source of news
