3. How do volcanic eruptions generate tsunamis?
Although relatively infrequent, violent volcanic eruptions represent also
impulsive disturbances, which can displace a great volume of water and generate
extremely destructive tsunami waves in the immediate source area.
According to this mechanism, waves may be generated by the sudden
displacement of water caused by a volcanic explosion, by a volcano's slope
failure, or more likely by a phreatomagmatic explosion and collapse/engulfment
of the volcanic magmatic chambers. One of the largest and most destructive
tsunamis ever recorded was generated in August 26, 1883 after the explosion and
collapse of the volcano of Krakatoa (Krakatau), in Indonesia. This
explosion generated waves that reached 135 feet, destroyed coastal towns and
villages along the Sunda Strait in both the islands of Java and Sumatra,
killing 36, 417 people. It is also believed that the destruction of the
Minoan civilization in Greece was caused in 1490 B.C. by the explosion/collapse
of the volcano of Santorin in the Aegean Sea.
4. How do submarine landslides, rock falls and underwater
slumps generate tsunamis?
Less frequently, tsunami waves can be generated from displacements of water
resulting from rock falls, icefalls and sudden submarine landslides or slumps.
Such events may be caused impulsively from the instability and sudden
failure of submarine slopes, which are sometimes triggered by the ground
motions of a strong earthquake. For example in the 1980's, earth moving
and construction work of an airport runway along the coast of Southern France,
triggered an underwater landslide, which generated destructive tsunami waves in
the harbor of Thebes. Major earthquakes are suspected to cause many
underwater landslides, which may contribute significantly to tsunami
generation. For example, many scientists believe that the 1998 tsunami ,
which killed thousands of people and destroyed coastal villages along the
northern coast of Papua-New Guinea, was generated by a large underwater slump
of sediments, triggered by an earthquake. In general, the energy of
tsunami waves generated from landslides or rock falls is rapidly dissipated as
they travel away from the source and across the ocean, or within an enclosed or
semi-enclosed body of water - such as a lake or a fjord. However, It
should be noted, that the largest tsunami wave ever observed anywhere in the
world was caused by a rock fall in Lituya Bay, Alaska on July 9, 1958.
Triggered by an earthquake along the Fairweather fault, an approximately
40 million cubic meter rock fall at the head of the bay generated a wave, which
reached the incredible height of 520-meter wave ( 1,720 feet) on the opposite
side of the inlet. A initial huge solitary wave of about 180 meters (600
feet) raced at about 160 kilometers per hour (100 mph) within the bay debarking
trees along its path. However, the tsunami's energy and height diminished
rapidly away from the source area and, once in the open ocean, it was hardly
recorded by tide gauge stations.
5. Can asteroids, meteorites or man-made explosions cause
tsunamis?
Fortunately, for mankind, it is indeed very rare for a meteorite or an asteroid
to reach the earth. No asteroid has fallen on the earth within recorded
history. Most meteorites burn as they reach the earth's atmosphere.
However, large meteorites have hit the earth's surface in the distant
past. This is indicated by large craters, which have been found in
different parts of the earth. Also, it is possible that an asteroid may
have fallen on the earth in prehistoric times - the last one some 65 million
years ago during the Cretaceous period. Since evidence of the fall of
meteorites and asteroids on earth exists, we must conclude that they have
fallen also in the oceans and seas of the earth, particularly since four fifths
of our planet is covered by water. The fall of meteorites or asteroids
in the earth's oceans has the potential of generating tsunamis of cataclysmic
proportions. Scientists studying this possibility have concluded that the
impact of moderately large asteroid, 5-6 km in diameter, in the middle of the
large ocean basin such as the Atlantic Ocean, would produce a tsunami that
would travel all the way to the Appalachian Mountains in the upper two-thirds
of the United States. On both sides of the Atlantic, coastal cities would
be washed out by such a tsunami. An asteroid 5-6 kilometers in diameter
impacting between the Hawaiian Islands and the West Coast of North America,
would produce a tsunami which would wash out the coastal cities on the West
coasts of Canada, U.S. and Mexico and would cover most of the inhabited coastal
areas of the Hawaiian islands. Conceivably tsunami waves can also be
generated from very large nuclear explosions. However, no tsunami of any
significance has ever resulted from the testing of nuclear weapons in the past.
Furthermore, such testing is presently prohibited by international
treaty.
6. Where and how frequently are tsunamis generated?
Tsunamis are disasters that can be generated in all of the world's oceans,
inland seas, and in any large body of water. Each region of the world
appears to have its own cycle of frequency and pattern in generating tsunamis
that range in size from small to the large and highly destructive events.
Most tsunamis occur in the Pacific Ocean and its marginal seas. The
reason is that the Pacific covers more than one-third of the earth's surface
and is surrounded by a series of mountain chains, deep-ocean trenches and
island arcs called the "ring of fire" - where most earthquakes occur
(off the coasts of Kamchatka, Japan, the Kuril Islands, Alaska and South
America). Many tsunamis have also been generated in the seas which border
the Pacific Ocean. Tsunamis are generated, by shallow earthquakes all
around the Pacific, but those from earthquakes in the tropical Pacific tend to
be modest in size. While such tsunamis in these areas may be devastating
locally, their energy decays rapidly with distance. Usually, they are
not destructive a few hundred kilometers away from their sources. That is
not the case with tsunamis generated by great earthquakes in the North Pacific
or along the Pacific coast of South America. On the average of about
half-a-dozen times per century, a tsunami from one of these regions sweeps
across the entire Pacific, is reflected from distant shores, and sets the
entire ocean in motion for days. For example, the 1960 Chilean tsunami
caused death and destruction throughout the Pacific. Hawaii, Samoa, and
Easter Island all recorded runups exceeding 4 m; 61 people were killed in
Hawaii. In Japan 200 people died. A similar tsunami in 1868 from
northern Chile caused extensive damage in the Austral Islands, Hawaii, Samoa
and New Zealand. Although not as frequent, destructive tsunamis have been
also been generated in the Atlantic and the Indian Oceans, the Mediterranean
Sea and even within smaller bodies of water, like the Sea of Marmara, in
Turkey. In 1999, a large earthquake along the North Anatolian Fault zone,
generated a local tsunami, which was particularly damaging in the Bay of
Izmit. In the last decade alone, destructive tsunamis have occurred in
Nicaragua (1992), Indonesia (1992, 1994, 1996), Japan (1993), Philippines
(1994), Mexico (1995), Peru (1996, 2001), Papua-New Guinea (1998), Turkey
(1999), and Vanuatu (1999).
7.How does tsunami energy travel across the ocean and how far
can tsunamis waves reach?
Once a tsunami has been generated, its energy is distributed throughout the water
column, regardless of the ocean's depth. A tsunami is made up of a series
of very long waves. The waves will travel outward on the surface of the
ocean in all directions away from the source area, much like the ripples caused
by throwing a rock into a pond. The wavelength of the tsunami waves and
their period will depend on the generating mechanism and the dimensions of the
source event. If the tsunami is generated from a large earthquake over a
large area, its initial wavelength and period will be greater. If the
tsunami is caused by a local landslide, both its initial wavelength and period
will be shorter. The period of the tsunami waves may range from 5 to 90
minutes. The wave crests of a tsunami can be a thousand km long, and from
a few to a hundred kilometers or more apart as they travel across the ocean.
On the open ocean, the wavelength of a tsunami may be as much as two
hundred kilometers, many times greater than the ocean depth, which is on the
order of a few kilometers. In the deep ocean, the height of the tsunami
from trough to crest may be only a few centimeters to a meter or more - again
depending on the generating source. Tsunami waves in the deep ocean can
travel at high speeds for long periods of time for distances of thousands of
kilometers and lose very little energy in the process. The deeper the
water, the greater the speed of tsunami waves will be. For example, at
the deepest ocean depths the tsunami wave speed will be as much as 800 km/hr,
about the same as that of a jet aircraft. Since the average depth of the
Pacific ocean is 4000 m (14,000 feet) , tsunami wave speed will average about
200 m/s or over 700 km/hr (500 mph). At such high speeds, a tsunami
generated in Aleutian Islands may reach Hawaii in less than four and a half
hours. In 1960, great tsunami waves generated in Chile reached Japan,
more than 16,800 km away in less than 24 hours, killing hundreds of people.
8. Why aren't tsunamis seen at sea or from the air?
In the deep ocean, tsunami wave amplitude is usually less than 1 m (3.3 feet).
The crests of tsunami waves may be more than a hundred kilometers or more
away from each other. Therefore, passengers on boats at sea, far away
from shore where the water is deep, will not feel nor see the tsunami waves as
they pass by underneath at high speeds. The tsunami may be perceived as
nothing more than a gentle rise and fall of the sea surface. The Great
Sanriku tsunami, which struck Honshu, Japan, on June 15, 1896, was completely
undetected by fishermen twenty miles out to sea. The deep-water height of
this tsunami was only about 40 centimeters when it passed them and yet, when it
arrived on the shore, it had transformed into huge waves that killed 28,000
people, destroyed the port of Sanriku and villages along 275 km of
coastline. For the same reason of low amplitude and very long periods in
the deep ocean, tsunami waves cannot be seen nor detected from the air.
From the sky, tsunami waves cannot be distinguished from ordinary ocean waves.
9. What are the factors of destruction from tsunamis?
There are three: inundation, wave impact on structures, and erosion.
Strong, tsunami-induced currents lead to the erosion of foundations and
the collapse of bridges and seawalls. Flotation and drag forces move
houses and overturn railroad cars. Considerable damage is caused by the
resultant floating debris, including boats and cars that become dangerous
projectiles that may crash into buildings, break power lines, and may start
fires. Fires from damaged ships in ports or from ruptured coastal oil
storage tanks and refinery facilities, can cause damage greater than that
inflicted directly by the tsunami. Of increasing concern is the potential
effect of tsunami draw down, when receding waters uncover cooling water intakes
of nuclear power plants.
10. What determines how destructive a tsunami will be near
the origin and at a distant shore?
Tsunamis arrive at a coastline as a series of successive crests (high water
levels) and troughs (low water levels) - usually occurring 10 to 45 minutes
apart. As they enter the shallow waters of coastlines, bays, or harbors,
their speed decreases to about 50-60 km/hr. For example, in 15 m of
water the speed of a tsunami will be only 45 km/hr. However 100 or more
kilometers away, another tsunami wave travels in deep water towards the same
shore at a much greater speed, and still behind it there is another wave,
traveling at even greater speed. As the tsunami waves become compressed
near the coast, the wavelength is shortened and the wave energy is directed
upward - thus increasing their heights considerably. Just as with
ordinary surf, the energy of the tsunami waves must be contained in a smaller
volume of water, so the waves grow in height. Even though the wavelength
shortens near the coast, a tsunami will typically have a wavelength in excess
of ten kilometers when it comes ashore. Depending on the water depth and
the coastal configuration, the waves may undergo extensive refraction - another
process that may converge their energy to particular areas on the shore and
thus increase the heights even more. Even if a tsunami wave may have been
1 meter of less in the deep ocean, it may grow into a huge 30-35 meter wave
when it sweeps over the shore. Thus, tsunami waves may smash into the
shore like a wall of water or move in as a fast moving flood or tide - carrying
everything on their path. Either way, the waves become a significant
threat to life and property. If the tsunami waves arrive at high tide,
or if there are concurrent storm waves in the area, the effects will be
cumulative and the inundation and destruction even greater. The historic
record shows that there have been many tsunamis that have struck the shores
with devastating force, sometimes reaching heights of more than 30-50 meters.
For example, the 1946 tsunami generated by an earthquake off Unimak
island in Alaska's Aleutian Islands, reached heights of more than 35 meters,
which destroyed a reinforced concrete lighthouse and killed its occupants.
Finally, the maximum height a tsunami reaches on shore is called the
runup. It is the vertical distance between the maximum height reached by
the water on shore and the mean sea level surface. Any tsunami runup over
a meter is dangerous. The flooding by individual waves will typically
last from ten minutes to a half-hour, so the danger period can last for hours.
Tsunami runup at the point of impact will depend on how the energy is
focused, the travel path of the tsunami waves, the coastal configuration, and
the offshore topography. Small islands with steep slopes usually
experience little runup - wave heights there are only slightly greater than on
the open ocean. This is the reason that islands with steep-sided fringing
or barrier reefs are only at moderate risk from tsunamis. However, this
is not the case for islands such as the Hawaiian or the Marquesas. Both
of these island chains do not have extensive barrier reefs and have broad bays
exposed to the open ocean. For example, Hilo Bay at the island of Hawaii
and Tahauku Bay at Hiva Oa in the Marquesas are especially vulnerable.
The 1946 Aleutian tsunami resulted in runup, which exceeded 8 m at Hilo
and 10 m at Tahauku; 59 people were killed in Hilo and two in Tahauku.
Similarly, any gap in a reef puts the adjacent shoreline at risk.
The local tsunami from the Suva earthquake of 1953 did little damage because of
Fiji's extensive offshore reefs. However, two villages on the island of
Viti Levu, located on opposite gaps in the reef, were extensively damaged and
five people were drowned.
11. What are some of the largest historical tsunamis?
Destructive tsunamis have occurred in all of the world's oceans and seas.
In the last half of the 20th Century, Pacific-wide, destructive tsunamis
occurred in 1946, 1952, 1957, 1960, and 1964. (Many more tsunamis in
inland seas around the periphery of the Pacific, where extremely destructive
locally and claimed thousands of lives. Such localized tsunamis occurred
in 1975, 1983, 1985, 1992, 1993, 1995, 1998, 1999 and 2001.
The 1 April 1946 Aleutian Earthquake and Tsunami
One of the most destructive Pacific-wide tsunamis was generated by a magnitude
7.8 earthquake near Unimak Island in Alaska's Aleutian Island Chain. A
huge wave of 35 meters destroyed completely the U.S. Coast Guard's Scotch Cap
lighthouse on Unimak and killed all five of its occupants. The lighthouse
was a steel-reinforced concrete structure standing about 30 meters above sea
level. Without warning, destructive tsunami waves reached the Hawaiian
Islands, five hours later, causing considerable damage and loss of life.
The waves completely obliterated Hilo's waterfront on the island of
Hawaii, killing 159 people there. Altogether a total 165 people lost
their lives from this tsunami, including children attending school at Hawaii's
Laupahoehoe Point, where waves reaching up to 8 m destroyed also a hospital.
Damage was estimated at $26 million (in 1946 dollars). In 1948,
and as a result of this tsunami, the U.S. established a Pacific Tsunami Warning
Center in Hawaii.
The 4 November 1952 Kamchatka Earthquake and Tsunami
A strong earthquake (magnitude 8.2) off the coast of Kamchatka Peninsula
generated a great destructive Pacific-wide tsunami. Its waves struck the
Kamchatka Peninsula, the Kuril Islands and other areas of Russia's Far East,
causing considerable damage and loss of life. The tsunami was widely
observed and recorded in Japan, but there was no loss of life or damage
there. There was considerable damage in the Hawaiian Islands and some
damage in Peru and Chile. The tsunami was recorded or observed
throughout the islands of the Pacific. In New Zealand waves reached
height of 1m. In Alaska, in the Aleutian Islands and in California waves of up
to 1.4 meters were observed or recorded. By far the largest waves
outside the generating area were observed in the Hawaiian
Islands. Fortunately, no human lives were lost in Hawaii from this
tsunami, but damage was extensive, estimates ranging from $800,000- $1,000,000
(in 1952 dollars). The tsunami caused damage on Midway Island.
Elsewhere in the Hawaiian island chain, the waves destroyed boats and
piers, knocked down telephone lines, and caused extensive beach erosion.
In some locations, tsunami waves were destructive in certain locations but
hardly noticeable at others. The north shore of the Island of Oahu
experienced higher waves of up to 4.5 meters. On the south shore of the
island, the tsunami was powerful enough to throw a cement barge in the Honolulu
Harbor into a freighter. The island of Hawaii experienced run up to 6.1
meters. In Hilo, a small bridge connecting Coconut Island to the shore
was destroyed by one of the tsunami waves lifting it off its foundation, then
smashing it down. The effects of the tsunami in the generating area in
Kamchatka, varied significantly. From Kamchatka Peninsula to Kronotsky
Peninsula the wave heights ranged from zero to 5 meters. From Kronotsky
Peninsula to Cape Shipursky the heights ranged from 4-13 meters. The
highest wave of 13 meters was the third and was observed at Olga Bay, where it
caused considerable damage. Travel time of the first tsunami wave to Olga
Bay was approximately 42 minutes after the earthquake. From Cape
Shipursky to Cape Povorotny, the tsunami waves ranged from 1 to 10 meters and
caused considerable loss of life and damage. At Avachinskaia Bay the
tsunami height was 1.2 meters and its travel time was about 30 minutes.
From Cape Povorotny to Cape Lopatkka the waves ranged from 5 to 15 meters.
At Khodutka Bay a cutter was thrown 500 meters back from shore. On the
West coast of Kamchatka Peninsula, the maximum tsunami runup at Ozernoe was 5
meters. At Alaid Island of the Kuril Island group, run up was 1.5 meters.
At Shumshu Island it ranged from 7-9 meters. At Paramushir Island
the waves ranged from 4-18.4 meters. At Severo - Kurilsk on Paramushir
Island, the second wave was the highest reaching maximum run up of 15
meters. It destroyed most of the town and caused considerable loss of
life. At Onekotan Island tsunami run up was 9 meters, while at
Shiashkoton Island it was 8 meters and at Iturup Island 2.5 meters. Waves
of up to 2 meters were observed at the Komandorsk Islands and at Okhotsk. At
Sakhalin - Korsakov a 1-meter tsunami wave was observed.
The 9 March 1957 Aleutian Earthquake and Tsunami
On March 9, 1957, an 8.3 magnitude earthquake south of the Andreanof Islands,
in the Aleutian Islands of Alaska - in the same general area as that of April
1, 1946 - generated a Pacific-wide tsunami. Although no lives were lost,
there was extensive destruction of property in the Hawaiian Islands, with
damage estimated at approximately $5 million (1957 dollars). The waves
were particularly high on the north shore of the island of Kauai where they
reached a maximum height of 16 meters, flooding the highway and destroying
houses and bridges. This was twice the height of the 1946 tsunami.
At Hilo, Hawaii, the tsunami runup reached 3.9 m and there was damage to
numerous buildings along the waterfront. Within Hilo Bay, Coconut Island was
covered by 1 m of water and the bridge connecting it to the shore, as in 1952,
was again destroyed.
The 22 May 1960 Chilean Earthquake and Tsunami
The largest earthquake ( magnitude 8.6) of the 20th century occurred on May 22,
1960 off the coast of south central Chile. It generated a Pacific-wide
tsunami, which was destructive locally in Chile and throughout the Pacific
Ocean. The tsunami killed an estimated 2,300 people in Chile. There
was tremendous loss of life and property in the Hawaiian Islands, in Japan and
elsewhere in the Pacific. Destructive waves in Hilo, Hawaii, destroyed
the waterfront and killed 61 people. Total damage was estimated at more
than $500 million (1960 dollars).
The 28 March 1964 Alaska Earthquake and Tsunami
The largest earthquake of the 20th Century in the northern hemisphere, with a
magnitude 8.4, affected an area in Alaska that was almost 1600 km long and more
than 300 km wide - extending from Valdez to the Trinity Islands, southwest of Kodiak
Island in the Gulf of Alaska. The earthquake caused areas to be lifted
by as much as 15 m (50 feet) in certain areas, while many other areas subsided
greatly. In addition to many local tsunamis generated within the Prince
William Sound, vertical crustal displacements averaging 1.8 m (6 ft.) over an
area of about 300,000 square kilometers (115,000 square miles) extending in the
Gulf of Alaska's continental shelf, generated a Pacific-wide tsunami. Its
waves were very destructive in southeastern Alaska, in Vancouver Island
(British Columbia), and in the U.S. States of Washington, California and
Hawaii. The tsunami killed more than 120 people and caused more than
$106 million in damages, making it the costliest ever to strike the Western United
States and Canada. Five of Alaska's seven largest communities were
devastated by the combination of earthquake and tsunami wave damage.
Alaska's fishing industry and most seaport facilities were virtually destroyed.
Tsunami waves at Kodiak Island washed away a total of 158 houses and
buildings within two blocks of the waterfront. Fishing boats were
carried hundreds of meters inland. The 1964 tsunami waves caused also
extensive damage in Vancouver Island (British Columbia), and in the states of
Washington, California and Hawaii, in the U.S.. The waves affected the
entire California coastline, but were particularly high from Crescent City to
Monterey ranging from 2.1 - 6.3 meters (7-21 feet). Hardest hit was
Crescent City, California, where waves reaching as much as 6 meters (20-21
feet) destroyed half of the waterfront business district. Eleven persons
lost their lives there. At Santa Cruz Harbor, the tsunami waves reached
as high as 3.3 meters (11 feet) causing some damage. There was extensive
damage in San Francisco Bay, the marinas in Marin County and at the Noyo, Los
Angeles and Long Beach harbors. Estimated losses in California were
between $1,500,000 and $2,375,000 (1964 dollars), while at Crescent City
tsunami damage was estimated at $7,414,000.
12. Why are locally generated tsunamis so dangerous?
A locally generated tsunami may reach a nearby shore in less than ten minutes.
There is not sufficient time for the Pacific Tsunami Warning Center or
for local authorities to issue a warning. For people living near the
coast, the shaking of the ground is a warning that a tsunami may be imminent.
For tsunamis from more distant sources, however, accurate warnings of
when a tsunami might arrive are possible8:57 AM 5/20/2003 because tsunamis travel
at a known speed.
13. Where can I find more tsunami related FAQs?
Geoscience
Australia's Tsunami Factsheet These questions are answered on this
factsheet at http://www.ga.gov.au/urban/factsheets/20010821_7.jsp:
What is a tsunami?
How do tsunamis occur?
Do tsunamis reach Australia?
How are tsunami warnings issued?
Oahu Civil Defense Agency Tsunami Questions and Answers These questions are answered by the Oahu Civil Defense Agency at http://www.co.honolulu.hi.us/ocda/tsunami2.htm:
What is a tsunami?
What areas of Oahu are vulnerable to tsunamis?
How will I know that a tsunami is expected?
What should I do when watches, warning or tsunami evacuation advisories/orders
are issued?
How can I get to a safe area or shelter if I have no transportation?
Will residents and property owners be allowed to enter tsunami evacuation
zones?
What if a tsunami warning is issued while my child is in school?
How can I obtain emergency assistance?
How can I obtain more information about tsunami hazards and preparedness?
Pacific Tsunami Museum FAQs These questions are answered on the Pacific Tsunami Museum Web site at http://www.tsunami.org/faq.htm.:
Where is Hilo, Hawaii?
What does the word tsunami mean?
What causes a tsunami? How is a tsunami wave different from a normal wave?
What is run-up?
Do all oceans have tsunamis?
How are tsunami wave heights measured?
How long does it take a tsunami to reach land?
What is the Tsunami Warning system?
What is the difference between a Tsunami Watch and a Tsunami Warning?
How many warnings have been issued by the Pacific Tsunami Warning Center since
it was established?
What should I do or not do in a tsunami warning?
Can the arrival time of a tsunami be accurately predicted?
What has been the most destructive tsunami to strike the Hawaiian Islands in
recent history?
How many Pacific-wide tsunamis have struck the Hawaiian Islands in recent
history?
How many locally generated tsunamis have occurred in the Hawaiian Islands in
recent history?
What is the "wrap-around" effect?
How many waves are there in a tsunami?
How does a tsunami behave as it approaches land?
How are inundation/evacuation areas determined?
Since I don't live in an inundation area why should I be concerned?
If I would like more information on tsunamis who should I contact?
PMEL's Tsunami:
FAQs
(http://www.pmel.noaa.gov/tsunami-hazard/tsunami_faqs.htm)
At this site you can find questions answered by PMEL tsunami scientists.
West
Coast/Alaska Tsunami Warning Center FAQs
(http://wcatwc.arh.noaa.gov/frequently.htm.)
Questions answered include:
What does the West Coast and Alaska Tsunami Warning Center do?
When is a warning issued?
If you feel a large earthquake, should you wait for a warning or evacuate?
How are tsunami generated?
Do all large earthquakes, greater than magnitude 7.0 generate dangerous
tsunamis?
What was the biggest earthquake ever recorded?
Does Alaska have a history as a dangerous tsunami source region?
What does the word 'tsunami' mean?
Can a tsunami sink a ship?
TsuInfo
Alert Newsletter
(http://www.wa.gov/dnr/htdocs/ger/tsuinfo/index.html.)
And in case your question falls within the range of "Infrequently"
Asked Questions, try looking at the online issues of TsuInfo
Alert Newsletter. Each issue usually has a column of questions
compiled by Lee Walkling of Washington's Division of Geology and Earth
Resources Library. Example question: If you hiked Mt. St. Helens, could
you find evidence of a tsunami?
14. What is a mega-tsunami and can it happen today?
The following is a position paper that was issued by the Tsunami Society
concerning the occurrence of Mega-Tsunamis:
The mission of the Tsunami Society includes "the dissemination of
knowledge about tsunamis to scientists, officials, and the public". We
have established a committee of private, university, and government scientists
to accomplish part of this goal by correcting misleading or invalid information
released to public about this hazard. We can supply both valid, correct and
important information and advice to the public, and the names of reputable
scientists active in the field of tsunami, who can provide such information.
Most recently, the Discovery Channel has replayed a program alleging potential
destruction of coastal areas of the Atlantic by tsunami waves which might be
generated in the near future by a volcanic collapse in the Canary Islands.
Other reports have involved a smaller but similar catastrophe from Kilauea
volcano on the island of Hawai`i. They like to call these occurences "mega
tsunamis". We would like to halt the scaremongering from these unfounded
reports. We wish to provide the media with factual information so that the
public can be properly informed about actual hazards of tsunamis and their
mitigation.
Here are a set of facts, agreed on by committee members, about the claims in
these reports:
- While the active volcano of Cumbre Vieja on Las Palma is expected to erupt
again, it will not send a large part of the island into the ocean, though small
landslides may occur. The Discovery program does not bring out in the
interviews that such volcanic collapses are extremely rare events, separated in
geologic time by thousands or even millions of years.
- No such event - a mega tsunami - has occurred in either the Atlantic or
Pacific oceans in recorded history. NONE.
- The colossal collapses of Krakatau or Santorin (the two most similar known
happenings) generated catastrophic waves in the immediate area but hazardous
waves did not propagate to distant shores. Carefully performed numerical and
experimental model experiments on such events and of the postulated Las Palma
event verify that the relatively short waves from these small, though intense,
occurrences do not travel as do tsunami waves from a major earthquake.
- The U.S. volcano observatory, situated on Kilauea, near the current eruption,
states that there is no likelihood of that part of the island breaking off into
the ocean.
- These considerations have been published in journals and discussed at
conferences sponsored by the Tsunami Society.
Some papers on this subject include:
"Evaluation of the threat of Mega Tsunami Generation From ....Volcanoes on
La Palma ... and Hawaii", George Pararas-Carayannis, in Science of Tsunami
Hazards, Vol 20, No.5, pages 251-277, 2002.
"Modeling the La Palma Landslide Tsunami", Charles L. Mader, in
Science of Tsunami Hazards, Vol. 19, No. 3, pages 160-180, 2001.
"Volcano Growth and the Evolution of the Island of Hawaii", J.G.
Moore and D.A.Clague, in the Geologic Society of America Bulletin, 104, 1992.
Committee members for this report include:
Mr. George Curtis, Hilo, HI (Committee Chairman) 808-963-6670
Dr. Tad Murty, Ottawa, Canada, 613-731-8900
Dr. Laura Kong, Honolulu, HI, 808-532-6423
Dr. George Pararas-Carayannis, Honolulu, HI, 808-943-1150
Dr. Charles L. Mader, Los Alamos, NM, 808-396-9855
and all can comment on this or other tsunami matters.
For information regarding the Tsunami Society and its publications, visit:
www.sthjournal.org.
For general and educational material on tsunamis, check: www.tsunami.org.