Skip to comments.Portion of volcano slips toward ocean
Posted on 02/27/2002 1:45:20 PM PST by RoughDobermannEdited on 04/29/2004 2:00:10 AM PDT by Jim Robinson. [history]
STANFORD, California (CNN) -- In an event known as a "silent earthquake," a 72-square-mile chunk of the south slope of Hawaii's Kilauea Volcano slipped 3.5 inches toward the sea several months ago, leading one scientist to warn of a possible disaster for Pacific Rim nations.
(Excerpt) Read more at cnn.com ...
This may turn out not to be the case. Oral traditions in Austrailia and New Zealand as well as the Pacific Northwest of the United States, indicate that at least two large tsunamis may have occurred in the Pacific basin in the not so distant past, a few thousand years at most. Can't find the article now, but I seem to rember something about evidence of one about every 500 years in the Pacific. If that's so, we are overdue, statistically speaking, but not much.
"Richard Chamberlain stars as David Burton, a mild-mannered tax attorney who is called in to represent five aborigines accused of killing another aborigine. Happily married (his wife is well played by Olivia Hamnett) with two beautiful daughters and a respectable middle-class home, Burton is a postcard of contentment. Although he is plagued with strange dreams, and his father (Frederick Parslow) reminds him that they have been a part of his entire life, Burton is more than happy to move through life unchallenged, relying on the rationality of the law and the comfort of Christianity to see him through.
"Yet, as the murder case unfolds, he finds himself increasingly drawn into the world of the aborigines, especially when he realizes that one of the leaders, Chris Lee (David Gulpilil), has been a recurring figure in his dreams. Despite being a white man, Burton feels drawn to the aborigines and their cultural heritage of putting the law above man, which is the exact opposite of his rational, modern understanding of the purpose of the law. When Burton tries to use his society's court of justice to defend the aborigines-arguing that they are tribal people and should be judged according to their tribal laws, an argument not without precedent in Australian legal history-he is faced with the disparity between his world and theirs.
"Weir makes expert use of the uniqueness of the Australian landscape. Even on his minimal budget, he creates impressive visuals of striking juxtaposition: a sudden torrential downpour of water and hail in the middle of the outback without a cloud in the sky; an aborigine in modern clothes painting symbols on the underside of a seaside cliff; an underground cave, long since forgotten beneath the streets of Sydney, filled with ancient statues and images that foretell the impending future. Weir fills the frame with water imagery, from the rage of nature in the form of constant blue-gray rain, to the banalities of everyday life in the form of an overflowing bathtub. If the image of the last wave of the title is somewhat of a letdown-not because of the purposeful vagueness of its reality, but the fact that its power and magnitude is restricted by the use of stock footage of a tidal wave, which was dictated by the film's budget-the symbolic weight of it has a grand force. It is a true climax, that which the film has been building toward from the very first frames. "
What the above review does not mention is that the aborigines recognize, through certain symbols displayed in Chamberlains house, relics of his father's church, that Chamberlain is the foretold precourser to tsunami. When this guy shows up, the wave is coming. More than the political stuff, the theme of the movie is that the tsunami is out there, it's a repeat of the Great Flood in the Bible. I comment only on the entertainment value of the film. Do not flame me on the Bible if you expect an answer.
In an event known as a "silent earthquake," a 72-square-mile chunk of the south slope of Hawaii's Kilauea Volcano slipped 3.5 inches toward the sea several months ago, leading one scientist to warn of a possible disaster for Pacific Rim nations.Silent but deadly. : )
This from BBC talks about the one you describe, plus evidence of earlier ones in the same location.
By R. Monastersky
A year after giant waves swept away 2,200 residents of Papua New Guinea, the disaster has claimed its final victim: the prevailing theory about what causes tsunamis.
Experts on these waves typically attribute them to undersea earthquakes, but evidence collected during marine surveys off the New Guinea coast implicates a submarine landslide or slump, reports the expedition team.
"There is no doubt that there is a shifta sea changein interpretation," says David R. Tappin, a coleader of the surveys and a marine geologist with the British Geological Survey in Nottingham.
"This really is one of those big paradigm shifts in science," says team member Philip Watts of Applied Fluids Engineering in Long Beach, Calif., who uses computer models to simulate tsunamis. "We suspect that a lot of the bigger, known tsunamis involved some landsliding."
The Papua New Guinea tsunami, a train of three monster waves, struck the north shore on July 17, 1998 (SN: 10/3/98, p. 221). Ever since then, researchers have struggled to explain how a moderate earthquake, of magnitude 7.1, could have heaved up a tsunami reaching 15 meters tall. Some speculated that the shaking caused an underwater sediment slide large enough to spawn the waves.
In January, a team of researchers boarded a Japanese ship to survey the seafloor. It was the first such intense study after a tsunami. In this expedition, they mapped the seabed and drilled samples of sediments. In late February, they used a robotic sub to photograph the seafloor.
The scientists described their findings at a July meeting of the International Union of Geodesy and Geophysics in Birmingham, England, and in the July 27 Eos.
The exploration focused on the continental slope, which plummets into a 4-kilometer-deep trench. This chasm marks where a piece of the Pacific Ocean floor crashes into New Guinea. As the Pacific tectonic plate scrapes beneath the island, it creates the deep trench and sparks frequent earthquakes.
The survey found that the extremely steep continental slope bears a thick carpet of sediments. In places, this coating has slid downhill in speedy landslides and slower-moving slumps.
On one dive, the researchers discovered a fresh, amphitheater-shaped scar, created when a giant chunk of sediment slumped downhill. "We know this slope failed sometime in the past," says Watts. "The mystery is, When did it go?"
The researchers also found a 15-km-long fault that showed evidence of recent movement. Faulting of the seafloor can generate tsunamis when one side jumps up and the other side drops, displacing water in the process.
Tappin, Watts, and others who think a slump caused the waves contend that the fault could not be the source. Eyewitness accounts indicate that the first wave struck shore about 20 minutes after the main shock of the earthquake, too long for the tsunami to have originated from subsea faulting during the quake. A slump, however, typically lags several minutes after an earthquake and could explain the delay.
When Watts modeled the tsunami, he obtained better results using an undersea slump than a sea-bottom quake. "I'm convinced that the main part of the tsunami was generated by one giant slump," he says.
Further support comes from a 70-second-long rumble recorded in the middle of the Pacific soon after the earthquake. This sound lasted too long to have come from a small aftershock and may represent a seafloor slide, says Emile A. Okal of Northwestern University in Evanston, Ill.
Some survey participants, however, discount the slump theory. Harry Yeh of the University of Washington in Seattle argues that simulations of a subsea quake can explain the tsunami's size. The team found evidence for small slides but no obvious signs of a giant slump, he says.
Whatever the outcome of the debate, the recent tsunami is forcing researchers to consider slumps as potential sources of giant waves, says Eddie Bernard, coordinator of the National Tsunami Hazard Mitigation Program in Seattle. "I think the good thing that this has done is to open our eyes."
The disaster also suggests that relatively modest quakes, such as the kind that occasionally rock southern California, can trigger giant tsunamis by setting off slides. "This makes the hazard much more dangerous than the scientific community has perceived it in the past," says Bernard.
From Science News, Vol. 156, No. 7, August 14, 1999, p. 100. Copyright © 1999, Science Service.
A 7.0 earthquake, with the epicenter significantly inland, occurred shortly after sundown and was followed 20 minutes later by a 5.9 aftershock. We think the initial quake triggered a landslide on the sea floor, probably on the order of four or five cubic kilometers. The wave arrived onshore five to 10 minutes after the initial quake.The block discussed in the article is probably an order of magnitude larger than the one that caused the New Guinea tsunami.
In an event known as a "silent earthquake," a 72-square-mile chunk of the south slope of Hawaii's Kilauea Volcano slipped 3.5 inches toward the sea several months ago, leading one scientist to warn of a possible disaster for Pacific Rim nations.
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Mega-tsunami have affected much of the coastline of Australia over the past millennium. Such catastrophic waves have left an imprint consisting predominently of bedrock sculpturing of the rocky coastline and deposition of marine sediments to elevations reaching 130 mabove sea level. One of the largest of these events occurred in eastern Australia in the fifteenth century. This event may be related to the Mahuika impact crater found at 48.38 S, 166.48 E on the continental shelf 250 km south of New Zealand. A comet at least 500 m in diameter formed the crater. Maori and Aboriginal legends allude to significant cosmogenic events in the region, while Aboriginal legends about tsunami are common along the eastern Australian coast. Evidence for legends that could describe the impact of a cosmogenic tsunami also exists in NW Australia. Here geological evidence of a single megatsunami as recent as in the seventeenth century covers 1500 km of coastline. We term this event Wandjina after the artwork related to the legends. More attention should be given to oral traditions in searching globally for other sites of significant mega-tsunami.
I’m sure it’ll be much less damaging next time, though. ;’)
And these could all be from mere landslides, rather than, say, an impact from space.
Underwater earthquakes, impacts from space...and the odd (probably rare) landslide?
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