Posted on 05/12/2006 11:49:03 AM PDT by blam
Tsunami risk of asteroid strikes revealed
18:18 12 May 2006
NewScientist.com news service
Jeff Hecht
The researchers modelled the asteroid impact believed to have led to the demise of the dinosaurs this frame shows tsunami wave heights 4 hours after the impact of the 10-kilomtre-wide asteroid (Image: Steve Ward)Related Articles
Tsunamis triggered by asteroid impacts cause a disaster similar to the 2004 Asian tsunami once every 6000 years on average, according to the first detailed analysis of their effects.
Researchers have assumed that tsunamis would make ocean impacts more deadly than those on land. But Steve Chesley at the Jet Propulsion Laboratory in Pasadena, and Steve Ward at the University of California at Santa Cruz, both in the US, are the first to quantify the risks.
The pair first calculated the chance of various size asteroids reaching the Earth's surface, and then modelled the tsunamis that would result for asteroids that hit the oceans.
For example, the model shows that waves radiating from the impact of a 300-metre-wide asteroid would carry 300 times more energy than the 2004 Asian tsunami. You can view movies of impact simulations in the North Atlantic, South Atlantic, Gulf of Mexico and Pacific (all in .mov format).
Fifty million people
To accurately assess the overall impact-tsunami risks, the analysis included the full range of asteroid sizes, including the smallest asteroids capable of penetrating the Earth's atmosphere. These are between 60 and 100 metres, depending on their composition.
The most common asteroids, between 100 m and 400 m, would yield tsunami waves up to 10 m when they arrived at the coast. A total of about 50 million coastal residents are vulnerable to such waves, though no single impact would affect them all. The researchers predict a tsunami-generating impact should occur about once every 6000 years, and would on average affect over one million people and cause $110 billion in property damage.
The study also showed that asteroid impacts in the 300-metre class might be similar to the huge tsunamis thrown up when massive chunks of rock break from the sides of volcanoes and fall into the ocean. These events are also thought to occur roughly once every 6000 years.
The analysis confirms suspicions that tsunamis are the biggest risk posed by asteroid impacts. The risks from climate effects of big impacts through dust and smoke that blocks out the Sun are about two-thirds that of tsunamis, while those of land impacts are about one-third of the tsunami risk.
Hurricane aspects
"There still are a lot of uncertainties," Chesley cautions. The solar system's population of 100 m to 400 m asteroids is poorly known, as are coastal population distributions. A big question is how the waves would behave when they reach the shore; successive wave peaks are much closer together in asteroid tsunamis than in earthquake tsunamis (see a simulation of an asteroid hitting the water, here).
But the ultimate uncertainty is when and where an asteroid might hit. "Asteroids sprinkle down pretty much at random," says Ward, "They don't pick out California or Florida."
And, like hurricanes, location is the key. Hurricane Katrina became America's worst natural disaster in living memory not because it was the biggest storm, but because it made a direct hit on vulnerable New Orleans.
But while hurricanes are difficult to predict, they do follow the same general paths. Asteroids come out of the blue literally.
Journal reference: Natural Hazards (vol 38 p 355)
You are right. I was looking for inland effects and it looks like the model didn't show any. I guess it's all the 200 ft. dikes the Army Corps of Engineers are going to build that stopped the waves from swamping the hinterland. ;>)
"The six year long volcanic winter and 1000-year-long instant Ice Age that followed Mount Toba's eruption may have decimated Modern Man's entire population. Genetic evidence suggests that Human population size fell to about 10,000 adults between 50 and 100 thousand years ago. "
This isn't an exact analogy but how much does a lightning rod cost to protect a building vs the damage a lightning bolt can cause? River floods, hurricane storm surges are known threats and they happen more frequently, a buoyant flood road not only would protect against those known threats but tsunamis as well, at least limiting the damage to the over-topping wave-force. But hey, I'm not going to do it for you for FREE. You want to drown? Go ahead, see your whole seacoast wiped away, I only show you HOW to protect yourself from MASSIVE death and destruction from floods. I'm not Santa Claus, the Tooth Fairy, the Easter Bunny; just an architect coming up with a solution as an intelligent alternative to levees, sand bagging. Instead of moaning and groaning about the challenge, what's YOUR solution?
I read it too, which makes my 'DUH!' reaction to this article even more funny. Where's the 'master of the obvious' graphic when you need it?
Well, they show a frame grab on the site from one that does have inland effects for at least the Gulf of Mexico, so I assume they exist for the other areas modelled. I'd be interested in seeing the north Atlantic one, as the impact is just off NC, where I'm located.
That reflects the shorelines 65 Myears ago.
I've got that one on one of my bookcases somewhere...
One of the best things about "Lucifer's Hammer" was the research Niven and Pournelle must have done. While their comet was quite large and hit at several points around the world, it was plain that any large body crashing into our little ball of clay and water would cause every fault to suddenly and disasterously release any pent-up energy.
Tsunamis along the shores reaching way inland through river channels and super-violent earthquakes knocking down nearly every structure man had made. It wouldn't be pretty but it would be interesting. Your mountain home might indeed become beachfront property- if it survived!
I didn't see that in the article; did I miss it, or is that knowledge that you bring to the table? I'm reasonably certain they intended to show the extent of inland flooding. Is the whitish area analogous to some ancient shoreline? I'm only familiar with the "fall line" separating the Piedmont and coastal plain regions in NC, SC and VA, which I understand is believed to have been the shore, long ago. But, from what I can tell, this is going inland well past the fall line in most areas of NC and SC at least. Also, I understand 65M as 65,000 (same as 65K), since I'm in the printing industry. 65,000,000 would be 65MM. You did mean millions and not thousands, correct?
Yes I did mean Mega, not kilo.
As for the shorelines I believe that what I said is correct. Gimme a few to verify?
The meteorite hurtled toward the big, blue planet, reaching speeds of as much as 150,000 miles per hour. Its surface white-hot from the friction caused by its plunge through the atmosphere, the giant crashed into the sea on what is now the northern coast of the Yucatán Peninsula of Mexico. The impact of the six-mile-wide space maverick created an underwater crater more than 25 miles deep and 112 miles in diameter farther across than the distance between Austin and Waco.
Material was blasted out of the crater at 50 times the speed of sound. About 400 cubic miles of debris were carried upward by the resulting fireball. (The 1980 eruption of Mount St. Helens, by comparison, released less than a third of a cubic mile of ash.) After several months of drifting around in the atmosphere, the finer particles began settling back to Earth, covering the entire planet with a thin layer of dust.
Another 5,000 cubic miles of melted and crushed rock was ejected from the crater, then fell back to Earth in a matter of hours within 3,000 miles of the impact in all directions. Called "ejecta," this melt rock was thickest near the point of impact, becoming patchier farther away.
The enormous energy generated by the impact also created huge tidal waves radiating out from the area of collision giant versions of the ripples that form on the surface of a lake when someone tosses a rock into the water. These "ripples" were 150 to 300 feet high up to as tall as a football field is long. Churning up the seabed to a depth of 40 feet, one of the monster tsunamis roared across what we now call the Gulf of Mexico. The wave-from-hell tore rocks, sharks' teeth, sand and boulders from the bottom of the sea as it went. The giant wave finally deposited its burden of trash more than 150 miles inland from today's coastline.
The Texas Connection
One of the sites where this antique debris has been found is along the Brazos River in Falls County about 30 miles southeast of Waco, where the rock layer has been exposed by water erosion. This area was under a shallow sea at the time of the probable impact and tidal wave. Paleontologist Thor Hansen began studying the Brazos River site in 1985. He found a layer of mud clumps as much as three feet thick, along with fist-size chunks of sandstone. This layer is in a deep bed of mudstone that had been produced by a million years of otherwise quiet accumulation of water-deposited silt. Similar layers of what is most likely tidal-wave trash dating from the same geological period have been found in Mexico, Arkansas, Cuba, and off the coasts of Haiti and North Carolina.
Some scientists believe that the debris in question can be explained by a large volcanic eruption. But each new report by scientists studying the phenomenon adds weight to the collision theory.
Dinosaur Killer?
The cosmic collision occurred about 65 million years ago at the boundary between two geological periods: the Cretaceous, when dinosaurs flourished on the planet and few mammals existed, and the Tertiary, when the dinosaurs had mostly vanished and mammals began to proliferate. Did the enormous amounts of material thrown into the atmosphere block out the sun and destroy parts of the ozone layer to the extent that the Earth's ecological systems shut down? And did that shutdown cause more than half the planet's species to die off? This is the scenario suggested by a number of scientists who have been exploring the probable Big Crash.
The asteroid/comet collision idea is not a recent one. French scientist Pierre de Maupertuis proposed as early as 1750 that comets striking the Earth had caused mass extinctions by altering the atmosphere and the oceans.
But the first solid evidence linking a cosmic catastrophe with the wholesale eradication of species was suggested in the late 1970s by Walter Alvarez, a geologist at the University of California at Berkeley, and his father, physicist Luis Alvarez. The layer of fine debris from the impact shows up today as a stratum of grayish clay at the Cretaceous/Tertiary boundary (K/T boundary). The clay layer appears to be world-wide: It has been found at more than 100 sites scattered over the globe. This clay contains an unusually high amount of the element iridium up to 30 times more than could normally be expected. Iridium, a heavy, brittle, metallic chemical element, is found in the Earth's core. It is rare on the Earth's surface, but comets and asteroids are relatively rich in it. The high concentration of iridium in the K/T boundary clay stratum could be explained by the collision theory.
The Brazos River site reveals not only the jumbled anomalous sandstone rocks and sharks' teeth from the tidal wave, but also this overlying, iridium-rich layer of clay.
The discovery of a thick layer of glassy particles at the K/T boundary in Haiti in the early 1990s provided what many geologists feel is the last piece of evidence needed to support the collision theory. Chemical analysis of the glass drops, called tektites, confirms their impact origin and indicates that they are probably part of the ejecta layer.
The most likely candidate for ground zero is the Chicxulub crater, just north of Mérida, Mexico, on the coast of the Yucatán Peninsula. The huge crater, which was underwater at the time of the probable impact, contains deposits of rocks, such as highly shocked quartz, which can be produced only by such an impact or by a nuclear explosion. Analysis of rocks from drill cores taken from the Chicxulub crater indicate an age of 65 million years, identical to the age of the tektites in Haiti.
The consensus appears at this time to be that an asteroid did splash down in the Yucatán and that it did produce the ejecta layer with its glassy particles, the global layer of clay, and the tsunami trash in Texas and elsewhere and that the dinosaurs died off after the collision.
But the jury is still out on whether the first caused the second.
Written by Mary G. Ramos and first published in the 1994-1995 Texas Almanac.
High ground? Yes, but roughly 3/4 of all populations live within 30 miles of an ocean shore; as lung fish we emerged from the ocean long ago, still have an ocean current inside : our pulsating blood system. Thus the vast majority will remain close to our original marine "home". The tsunami of 12/26/5 was a clear warning : be prepared(boy scout)or DIE. Katrina taught 2 lessons : 300 years of geological siltation and the self-reliant lived, those who waited for government "help" suffered and died. How would you feel as governor of a coastal state if your whole coastline was wiped CLEAN and yet you COULD have built a protective barrier like I suggest? For every dollar spent on it you'd save a $1000 worth of real estate and millions of lives. Oh well, I guess it's evolution's way....
That really is pretty close to the extent of the white area. I'm still hoping to get at the meaning of the white and green areas. What's really impressive (or scary, depending upon your perspective) is the distance in four hours' time. The extent of the green, up the Mississippi Valley, appears to be at least 600 miles. A wall of water, even a relatively shallow one, moving at 150 mph average, would produce damage more akin to a nuclear blast than any sort of flood. Of course, speed would be much greater, the closer you get to the site of impact, as well as the closer you get to the Gulf or the Atlantic. I'm guessing that the green areas would definitely get wet, but the effects would be more along the lines of widespread flooding, since the forward momentum would be greatly reduced by that point. Reasonable assumption?
Time is not on our side here....it will eventually happen.
I havent read the book in a while and cant find my copy, does anyone rememer why the US and the Soviets nuked China in that book after the asteroids hit?
Nudge at-risk asteroids away from Earth's path. Japan recently sent a robotic spacecraft named Hayabusa to an asteroid, landed on it, and plan a return to Earth. If they can do all that we should be able to plant a thermonuclear blast into a trouble maker.
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