With the recent qyauke in Chile I can't help but wonder what all the hype is with the tsunami waves and here is why. They reports a tsunami wave hit (I forgot where) but it was 7.7 feet tall. An article today stated waves hit Japan that were 4 ft tall.

Sorry if I don't seem scared over this but when I went boating on lake Michigan we were in waves 2-4 ft and it's not uncommon for storms to bring in 10-12 ft waves. The most we may see is a small craft warning.

So is there something else about a tsunami wave that is different from a regular wave or is it media hype. Trust me I'm sure some of it is media hype.

I just can't help but laugh when I hear the entire coastline was evacuated for a 4 ft wave! Granted they may not of known the size of the wave coming but then don't make it out to be what it is. Maybe I am missing something.

Tsunami have a very long period (distance from crest to crest) and move at tremendous speed. You can't think of them as the four footers you've seen traveling at half the wind speed with 25 feet between them, A tsunami 4 footer might be going 500 MPH and have a period of many miles. It's a huge volume of water that can rush way up a shoreline.

Don't you remember the tsunami that hit last year (I can't remember where it was!) I think it was indonesia or something. The trouble with tsunami as Dave pointed out is the velocity, coupled with the shear volume of water. That much water traveling at 500 MPH hits the shoreline with tremendous force, and they really can't predict how bad it will be. Luckily the quake that hit Chile was deep, I think i read 22 miles below the crust, if the quake wre shallower the resulting tsunami would have been much more powerful.

I heard an explanation yesterday that seemed like a good way to picture it. A Tsunami wave is more like a flash flood than a "wave" one would surf, etc. Like Memory Make said, the volume of water is huge...I guess more like a storm surge. Initially they expected a 6' wave at Hilo Bay Hawaii, sounds like noting, but that wave, due to volume of the wave and the speed of that volume, was supposed to carry water a mile inland!

The 9.5 Chilean earthquake in 1960 caused a 35 ft wave to hit Hilo Bay. Now that's a big wave regardless of volume! Other parts of the island were hit w/ 3 - 17 ft waves from that earthquake and caused little damage. The 35 ft one caused big damage.

1960 Tsunami

Interesting bit from Wiki on why earthquakes only cause a "drawback" before the tsunami wave hits in one direction or side of the fault line.

Yes I recall that one. It happened on Christmas day. How big was that wave though? I will have to do some digging since yes that caused a lot of destruction and damage but I'm going to be shocked if that was all from a 4 ft wave. I would have thought that was more 20ft +.

I believe the Indonesian Tsunami was on Dec 26, way back in 2004. You guys must be getting old...

ya it was and yes I am getting old! Doesn't seem that long ago.

Time to join the getting old club. That old geezer in line in front of you would be me.

A tsunami wave is a VOLUME of water traveling at high velocity through the ocean, that volume normally being the same as the depth of the earthquake at the ocean floor. If the earthquake happened at a water depth of 300 feet, you have initially 300 feet of water moving at enormous speed. Normal waves you see breaking on the coast are normally caused by wind friction on the surface of the ocean. Tsunamis are NOT this kind of wave action, although the tsunamis in Banda Ache, (sp) Indonesia in 12/04 did have those type of characteristics, due to the abrupt rise in the sea bottom and proximity to the epicenter, causing the volume to rise rapidly and crest like a wind wave. There were plenty of videos showing huge waves actually breaking off the shoreline.

Think of a tsunami as a storm surge, much like in a hurricane. The 'foot' measurement is a rise ABOVE the mean high tide mark, or normal tidal waters. The footage measurement is relative to the ocean surface and land, ie, if the ocean was 8 feet higher generally, as in an 8 foot tsunami, how far inland would the shoreline be... What sets tsunamis apart is the velocity they travel. I have no clue how fast a hurricane surge travels, but tsunamis travel at 4-500 miles per hour! Put that speed with even a 5 foot surge, and it's capable of substantial damage in relatively flat shoreline areas, for several hundred feet inland. The tsunami in Hilo, Hawaii in 1960 did so much damage because of the relatively flat landscape.

Interestingly enough, there was some minor damage to the docks and a few boats from this tsunami, in Long Beach Harbor. The news reported the receding water left a couple boats high and dry! It came at a time of lowering tides, which surely didn't help!

Tsunamis as the others stated are not waves in the normal sense as what you see on the beach. Surfers often surf in waves way far higher than tsunami waves but those waves are not based on velocity and volume. Once they break they move toward shore and fizzle out. A tsunami keeps coming and coming and the height at landfall depends on many variables but a tsunami may be only in the 4 to 10 ft range as it hits land as example but the volume that follows the first hit is what does the damage. A telltale sign that one is approaching is if the beach water suddenly recedes at a very un normal pace and does not recover. There are videos to show that very occurrence during the 2004 Tsunami. Many of the areas hit were big vacation spots for European visitors especially in Thailand. Many had no clue what was about to happen even with the fast recession of the water at some locales. Take the time to watch this video and you will quickly get the idea as you will see a variety of videos taken at different locations. It starts with some video of the earthquake. Video is only about 5 and a half minutes.

http://www.youtube.com/watch?v=RDOuwMj7Xzo

I watched that indonesia video in Nick's post above over the weekend. I had no idea of the devastation that caused. It's way worse than a tornado or an earthquake - it just destroys everything.

Do a youtube search on Banda Aceh and Tsunami and you'll know what they can do...

When I commercial fished in Alaska many of the bars and shops around had pictures of a tsunami that hit there in the '60s. Since the land is not flat it did not do much real damage other than the docks and shoreline facilities but the "drawback" was really something to see. The entire sound was drained. I'm not sure how deep it was but as I recall from looking at the pictures of wharfs standing in the middle of mud flats it must have dropped the ocean level at least 25 or 30 feet. This was in Sitka sound and all the boats there were laying on their side. Then when the water came back in it pushed all those boats up the shore to the foothills.

Even a small tsunami can cause amazing damage. This picture is of the Kodiak shoreline after the 1964 Prince william sound quake. There was no earthquake damage due to the distance away from the mainland but it did get hit with tsunami waves. The highest was about 20'. They see regular waves that tall and taller every year, this is a bit different as you can see.http://wulik.com/Kodiakwaterfront.gif

I searched a bit but was not able to find pics of the drawback. It is equally impressive. If you have ever seen a timelapse of the tide going out in the Bay of Fundy where the tide can run 25' or more, imagine that going out and then back in in about 20 minutes. This can happen several times emptying and filling the bay or sound again and again. Pretty frightening.

We boated along the freighter channel on Lake St Clair this summer, and experienced the drawback to a much lesser degree. When a fully loaded freighter comes by, it pulls out several feet water and exposed 50-100 yards of additional beach. When the freighter passes, it all comes rushing back in and floods most of the beach, you'd better have your stuff pulled to higher ground. The boats also do a good bucking bronco routine. I can't imagine what a serious amount of wave would do.

Largest (highest) recorded tsunami wave, caused by the results of a seismic event (earthquake), was 1720 feet in Alaska on July 9, 1958. This happened when a landslide occured in Lituya Bay, Alaska...

World's Biggest Tsunami