Impact

MING Y. YU

    Hi, there is a major error in the discussions of the asteroid/comet impact tidal wave problem. The existing estimates are at most valid for the "final steady state", certainly not "tidal wave" effects.

     When an object falls into water, the resulting rise in the water depends on the impact conditions such as speed, etc. (Newton's action-reaction law). The raised (the reaction) water will be of the form of a ring, which expands outwards. This is a nonlinear wave problem. The ring shaped soliton will form the tidal wave. It can be much higher than that calculated from the displaced water assuming uniform height distribution. It can even grow as it propagates outwards and many after-shock solitons will follow because of the oscillations at the impact site. Furthermore, the coriolis force might cause such a large system to rotate and form some kind of tidal tornado, and the water can be ejected into the upper atmosphere and diffuse into deep space. Also, the dissipation will be huge and the giant waves will probably breakup. On the other hand, as soon as the tidal wave hits the shore, it will very quickly dissipate.

     Another point to consider is that for a large impact a lot of the water will be displaced into the atmosphere and may diffuse into space and/r eventually fall onto otherwise dry regions. The ground there can absorb a lot of water. Same is true for water moving inland from the shore.

     Physically, a large comet/asteroid (of rock-like material) will almost certainly breakup in the upper atmosphere due to the implosion caused by the rapidly vaporizing surface. The smaller pieces will vaporize quickly so that eventually not a very large volume will actually hit.

     May be it is more interesting to calculate what happens if a giant asteroid falls on Los Angeles! Can it trigger the long awaited earthquake?