I have been sort of avoiding 'net and TV news about the tsunami - I can’t take some of the horrifying images that are being shown. But I did catch a few glimpses of the aftermath and it looks to me like things are relatively “dry” there…
When we have floods in the US, people are riding around in motorboats down streets. The tsunami images I’ve seen seem to indicate that there’s no flood - all of the water just came up and sucked EVERYTHING back into the ocean, including the water itself.
If that’s the case (the water totally receded), what’s the science behind this? What is the force that is pulling the water back out to sea?
Also, what are the ecological ramifications of all this stuff - autos, homes, contents of homes, people, sewage, trees, etc - being in the ocean now? Is there going to have to be alot of cleanup effort offshore as well?
The basic force removing the water after the tsunami is the same force that removes rain water: gravity.
When we see pictures of floods, we are generally seeing an area that is relatively flat with an enormous amount of water going by it. The flatter it is, the more slowly the water moves. Often there are hills between the location where the water is flooding and any lower ground and the water needs to get past the bottleneck in the hills. (An exception would be the Mississippi flood of a few years ago that had no serious hills in the way. However, what it had was an enormous amount of water making its way down the Missouri, Mississippi, and Ohio rivers and their tributaries that was forced into narrow streams by the dikes and levees we had built to keep them out after earlier floods. Once the levees were breached, the water, being very high, poured into the area behind the levees through those narrow breaches. Once it had spread out behind those breaches, however, it had to flow back to the river through those same narrow breaches and without the tremendous height of the water that forced the breaches, the draining took a long time.
With the tsunami, there is only the gentle slope of the earth away from the ocean and the waves were able to retreat the same way they came. (There probably is flooding in many areas, but the initial picturees will have come from areas that were more accessible because they were not flooded.)