News Flash! Asteroid Creates 6500 ft Tsunami

mental_avenger · Jan 14, 2005

Imagine seeing that headline. Although the chance of an asteroid impact may be small, the chance of it producing such a wave is high. The only possible benefit that I can imagine from the tsunami in the Indian ocean is a new and perhaps more present awareness of the power of such an event. Considering the devastation from this “natural” disaster, this should serve as a wake-up call to those who think that an asteroid striking the Earth would do little damage, and only local damage at that. The asteroid (or comet) that struck the Yucatan Penninsula 65 million years ago was about 6 miles across. It wiped out most of the life on Earth. If a similar asteroid hit one of the oceans, it would create a tsunami that would wipe out most major coastal cites on that ocean, and proceed far inland. It might produce a tsumani wave 2000 meters high or more. Even a one kilometer asteroid is projected to probably create a tsunami wave traveling at 600mph, which would be between 500 and 1000 meters high when it approaches land, depending on many factors. It is estimated that the Chicxulub impact release the equivalent of 300,000 Megatons of energy. That is about 60 times more energy than all the energy that was predicted to be released in a full scale thermonculear war. So, what are the chances? Since about 70% of the Earth is covered by water, that would indicate that there is about a 70% chance that an asteroid would impact an ocean. For those of us who live in central mountain ranges, that is good news. Sort of. <div class="Discussion_UserSignature"> Our Solar System must be passing through a Non Sequitur area of space. </div>

nexium · Jan 14, 2005

We have the technology to put laser arrays in solar orbit. By focusing a very narrow beam on the correct side of an asteroiod or comet nucleus, the hole behaves like a jet engine propelling the asterioid gently, but efficiently, in the opposite direction, thus changing a likely hit to a likely miss. Present lasers would have to maintain the beam for thousands of hours (years in advance) of the probable impact, so we would need many laser arrays in solar orbit, using present lasers. Two or more laser arrays would best take turns as the asteroid rotated and changed position relative to the laser arrays. Most of the laser arrrays would be too far away to be effective. Does anyone know if lasers can be focused to less than one meter spot size at a distance of ten million kilometers? The hotter the hole, the more efficient the propulsion of the asteroid especially asteroids with negligible volatiles at the hole location. Neil

meteo · Jan 14, 2005

The only possible benefit that I can imagine from the tsunami in the Indian ocean is a new and perhaps more present awareness of the power of such an event. Considering the devastation from this “natural” disaster, this should serve as a wake-up call to those who think that an asteroid striking the Earth would do little damage, and only local damage at that. Edit: More would be able to get to safe areas in the Pacific which there would be a better chance the asteroid hitting. Ideally you would want to be stoping the asteroid, and not warning of a 6500ft wave. <img src="/images/icons/smile.gif" /> Also, the possibility of the La Palma landslide kind of scares me because there wouldn't be an effective evactuation. With an effective monitoring system you could possibly get enough warning time (a week) to evacuate 20km inland. However, I wonder if an evacuation would take place even if we had warning. If the island then collapsed you've got 6-9 hrs depending on where you are on the east coast. For rural areas that's enough time for most to get out but for major cities an alarming percentage wouldn't get out.

mcbethcg · Jan 14, 2005

I have no idea why it is fashionable to disregard the idea of using nukes to divert asteroids. Nukephobia, I guess.

nexium · Jan 14, 2005

Hi mcbethcg: It is worse than useless to nuke the asteroid after it enters Earth's atmosphere. In the vacuum of space the energy of the nuke is poorly coupled to the asteroid, unless you explode the nuke inside the asteroid. A nuclear blast at the surface changes the direction and speed minutely, but there is about a 1% chance it will break the asteroid into two or more almost as dangerous peices. We probably can not consistantly blow up killer asteroids even with 2049 technology. I suppose a 100 megaton nuke, on the inside, would break most 10 mile in diameter asteroids, so the largest fragment had 1/2 the mass, but 1/2 the mass is still enough to kill millions of humans short term and reduce the collective life expectancy by 100,000,000,000 person-years over the century following impact. Ten well placed big nukes inside the asteroid would all but surely reduce it to sizes that would do only minor damage. I agree nukaphobia is also a significant reason, which is somewhat justified. Nearly everyone would be scared of 10,000 big nukes in solar orbit, waiting for a killer asteroid or comet that they might be able catch and enter. Neil

nexium · Jan 14, 2005

Hi metao: I live in Jacksonville, Florida. I would need to drive 300 miles north on I75 or 441 or 23 to be reasonably sure a 6500 kilometer tsunami did not catch up with me. That would work, if few other people headed the warning, otherwise the roads would be hopelessly over loaded. Neil

mcbethcg · Jan 14, 2005

I am only talking about distant course changes, not attempts at pulverization. A nuke placed at the surface of an asteroid would still give it more of a course-changing-push than years of ion engines would. Attached ion engines are one of the prefered scenarios these days. The scientists who studied project orion determined that a nuclear bomb aplying pressure to a pressure plate has an ISP of about 10,000.

nexium · Jan 14, 2005

Hi mcbethcg: I sure you are aware of the long thread claiming Orion scientists were wrong and/or lied in hopes of getting more funding. It may however be ok to vaporize a few million tons of the killer asteroid to serve as reaction mass. Are you thinking 100 megatons yield at the surface to change the direction of an asteroid ten miles across by one second of arc? How many g does that acellerate the asteroid for the fraction of a second the blast lasts. Is there any chance the blast lasts even one second in vacuum? I'm really scared of having dozens of 100 megaton missles on Earth surface launch pads waiting until we find an asteroid that will miss Earth by 10,000 miles plus or minus 20,000 miles. We need to change that to miss to at least 20,000 miles if the margin of error is 20,000 miles. Is there any hope of smaller margin of error a year before impact? Is one second of arc change enough one year before impact? Can we fly the missle from Earth's surface to the asteroid in less than 6 months? 30,000 miles per hour (average speed) for 4000 hours = 120 million miles. A missle that powerful can be programed to hit any Earth city less than 20 minutes after launch. Average speed 20 kilometers per second = 20,000 kilometers in 1000 seconds = 17 minutes. Ion engines tested to date, produce so little thrust we would need to place a million of them on a ten mile wide asteroid a year before probable impact on Earth. Don't forget asteroids rotate, so we need shut down the ion engines about 12 hours per day to avoid cancelling the direction change of the other 12 hours Has anyone schedued a 100 pound thrust ion engine to fly in 2005? Dr. Edwards hopes to use an electromagneto what's it to deploy the space elevator. Is this possibly suitable as a substitute for an ion engine? Will it be tested soon. Does anyone have details? Neil

mental_avenger · Jan 14, 2005

More would be able to get to safe areas in the Pacific which there would be a better chance the asteroid hitting. Ideally you would want to be stoping the asteroid, and not warning of a 6500ft wave. The intent of my post was to reinforce the need to deploy an asteroid detection and defense system, not to warn people of a tidal wave. The graphic description was to indicate the serious nature of an asteroid impact, on land or on the water. <div class="Discussion_UserSignature"> Our Solar System must be passing through a Non Sequitur area of space. </div>

bobvanx · Jan 15, 2005

<blockquote>In reply to:<hr />The intent of my post was to reinforce the need to deploy an asteroid detection and defense system, not to warn people of a tidal wave.<hr /></blockquote>That's good to know, because the research being done in impact-generated tsunamis indicates a maximum deep-water wave height of just 230 meters, at 100km from a 2km impactor. There's also a fair amount of argument about whether there would even be a coherent wave generated. Interestingly, they don't bother modeling anything larger, since any impactor larger than 2km is considered to be globally devastating. But be sure to get to the Eltanin impact image at this link where they've figured out that a 4km impactor caused a 65m wave.

igorsboss · Jan 15, 2005

I believe it would be most effective to explode the nuclear ordinance inside the asteroid, by Newton's third law (equal and opposite reactions). I think of it this way: If the right side of the asteroid pushes against the left side of the asteroid, the course of each side is altered. If you tried to give the asteroid a push without splitting it, the main body of the asteroid would not change course very much. Instead, you would simply impart a very large Delta-V to the pusher craft... even if the pusher craft is an explosion. That is to say, an explosion on the surface would just bounce off without changing the asteroid's course.

igorsboss · Jan 15, 2005

Regarding the Tsunami warning system, I think it is perfectly reasonable to design the system for a maximum 20 meter Tsunami. Asteroid impacts need to be dealt with differently. There is an additional problem with the Oregon and Washington shoreline: Ground subsidence. When The Big One hits the Juan de Fuca subduction zone, not only will there be a huge Tsunami, but the shoreline is very likely to drop by 5 to 30 meters during the triggering Earthquake. Given 15 meters of ground subsidence followed by a 10 meter Tsunami, you get complete and utter devestation of the entire shoreline. The whole Long Beach penninsula would suddenly and permanently vanish. Estuaries would become bays.

redwhitearcher · Jan 15, 2005

There were much bigger tsunamis not caused by an asteroid. Try searching the web for mega-tsunami.

mental_avenger · Jan 15, 2005

That's good to know, because the research being done in impact-generated tsunamis indicates a maximum deep-water wave height of just 230 meters, at 100km from a 2km impactor. I don't have time to do the math, but a 230 meter deepwater wave would make an incredible tsunami. Consider that the Dec 26 tsunami was created by a 10 meter wave (the ocean floor raised 30 feet). The problem occurs when that wave runs up the coastal shelf. <div class="Discussion_UserSignature"> Our Solar System must be passing through a Non Sequitur area of space. </div>

mental_avenger · Jan 15, 2005

I believe it would be most effective to explode the nuclear ordinance inside the asteroid, by Newton's third law (equal and opposite reactions). The last thing we would want to do is blow a threatening asteroid apart and create multiple threats instead of one. The best way to prevent a threatening asteroid from hitting Earth is to deflect its path slightly when it is still a long ways from Earth, possibly even on the orbit preceeding the collision path orbit. The further back along that potential impact path, the less the asteroid needs to be nudged. In addition, it would probably be more effective to accelerate or decelerate the asteroid to make it miss, rather than trying to deflect it laterally. It might be a safer maneuver also. <div class="Discussion_UserSignature"> Our Solar System must be passing through a Non Sequitur area of space. </div>

bobvanx · Jan 15, 2005

>>I don't have time to do the math, Perhaps since you were aiming for a sensational headline, being an order of magnitude off isn't that important. I tried to find any impact model at all that supported a 6500 ft (2000m) wave, but the largest I could find was 230m. Most of the work looks like they predict under 65m. Devastatingly huge, certainly! But a far cry from your headline, and I figured a stickler for accuracy such as yourself would want to know.

mental_avenger · Jan 15, 2005

A deep ocean wave increases in size dramatically when it approaches land. Building to 10 times its original height when it runs up the sloping shelf onto land would be average. Some waves might build to twice that, depending on the length of the wave and the topography of the underwater shoreline. <div class="Discussion_UserSignature"> Our Solar System must be passing through a Non Sequitur area of space. </div>

jcdenton · Jan 16, 2005

The Chicxulub impact did cause a mega-tsunami. Tsunamis with tidal waves as high as 100m or more are classified as mega. <div class="Discussion_UserSignature"> </div>

nexium · Jan 16, 2005

With any technology we are likely to have in the next 40 years, blowing up a killer asteroid is about a prudent as trying to smother a fire with gasoline. In the coming 40 years, we are unlikely to be able to identify the rare exceptions, nor impliment the kind of precision needed to scacrifice a hundred small towns, totalling 200,000 people to save New York City and vicinity totalling 20 million people. Mental_Avenger exagerated, but not by much. Perhaps even more "last" is change a probable miss to a hit, by nuging the asteroid on the wrong side; an error we could easily make with the present state of the art. Another possible exception is a small asteroid having a volume of one cubic kilometer which we blow into pieces of the following size .2 .1 .03 .02 .01 cubic kilometer and smaller peices. The two biggest fragments may loose more than half their mass passing though the atmosphere and do little damage in sparsely populated areas. Most of the other pieces will be tiny when they reach Earth's surface. Without extreme precision, it is just as likely for the biggest peice to be 0.9 cubic kilometers and hit in a more populated area than it would have if we had done nothing. Neil

mental_avenger · Jan 16, 2005

You've lost me on your last post. With any technology we are likely to have in the next 40 years, blowing up a killer asteroid is about a prudent as trying to smother a fire with gasoline. I never advocated blowing up any asteroid. In fact, I commented that was the last thing we should do. In the coming 40 years, we are unlikely to be able to identify the rare exceptions I have no idea what “rare exceptions” you are referring to. Exceptions to what? nor impliment the kind of precision needed to scacrifice a hundred small towns, totalling 200,000 people to save New York City and vicinity totalling 20 million people. Again, what are you talking about? Nothing I have posted indicates sacrificing anything. Perhaps even more "last" is change a probable miss to a hit, by nuging the asteroid on the wrong side; an error we could easily make with the present state of the art. That's a joke, right? I don't see that we would have any problem calculating either the amount of force to apply, or the direction in which we should apply that force, in order to change the orbit of an asteroid on a collision course with Earth, to an orbit that is a clear miss. The problems will be: Building engines that are the most efficient for the job. Getting all the materials into the right place in time Stopping the rotation of the asteroid. After that, it is a relatively straightforward operation. If the readings are taken from Solar orbiting detection stations, using triangulation, the calculations should be very precise. If the object doesn't pass by another massive object on the way around, the calculations should remain valid. In any event, the orbit can be monitored to verify and update the course, and small changes be imple <div class="Discussion_UserSignature"> Our Solar System must be passing through a Non Sequitur area of space. </div>

News Flash! Asteroid Creates 6500 ft Tsunami

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