TSUNAMI Flashcards
In 2004 a magnitude 9.1 earthquake off the Indonesian coast generated a tsunami that swept across the Indian Ocean, killing an estimated 225,000 people. What oceanic plate subducted beneath the Burma micro-plate?
India Plate
WHAT IS A TSUNAMI?
A tsunami is a very long-wavelength wave of water that is generated by sudden displacement of the seafloor or disruption of any body of standing water.
- Sometimes called as “seismic sea waves”
- Occur suddenly, often without warning
- Extremely dangerous to coastal
communities
Distance between two wave crests
wavelength
Normal ocean waves have
wavelengths of about _____ meters
100 m
Tsunamis have wavelengths up to?
500 km
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 this is 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
Velocities of normal ocean waves are
about 90 km/hr, tsunamis have velocities up to 950 km/hr
950 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
dropped considerably
drawdown
when the crest of the wave hots, sea level rises called
run-up
standing waves in bodies of water, and are often found in large lake systems during strong winds.
seiches
HOW DO TSUNAMI OCCUR?
Tsunamis can be generated by volcanic
eruptions, landslides, underwater explosions, and meteorite impacts.
______ cause tsunami by causing a
disturbance of the seafloor.
earthquakes
Tsunamis are commonly generated in subduction zones under the ocean where two plates collide with one plate moving under the other, then when the plates get stuck, the overriding plate gets distorted. then what happens?
stuck area ruptures triggering an earthquake and pushing up the ocean flood and sea water above. this starts the tsunami which moves in opposite direction
The waves will travel in what direction from the source area?
outward on the surface of the ocean in all directions away from the source area
true or false
THe first wave is not always the largest/Strongest
true
what volcanic eruption caused a tsunami in 1883?
Krakatau ve
The _________ has set up a Pacific warning system for areas in the Pacific Ocean, called the Pacific Tsunami Warning Center
National Oceanic and Atmospheric
Administration (NOAA)
What to do when there is a tsunami alert?
- 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
true or false
passive margins are safe from tsunami
false
Describe crest and trough
crest maximum value of the upward displacement of a cycle and the trough is the opposite which is the minimum or lowest point
is the depth where water molecules are no longer affected by the passing wave. It is equal to about one-half of the wave’s wavelength (distance between
successive crests).
wave base
controlling factors of a tsunami occurrence
epicenter, magnitude, and type of displacement
