IMPACTS INTO OCEANS AND SEAS

Impacts of cosmic bodies into oceans and seas lead to the formation of very high waves. Numerical simulations of 3-km and 1-km comets impact ing into a 4 km depth ocean with a velocity of 20 km/sec have been con ducted. For a 1-km body, depth of the interim crater in the sea bed is about 8 km below ocean level, and the height of the water wave is 10 m at a distance of 2000 km from the impact point. As the water wave ru ns into shallows, a huge tsunami hits the coast. The height of the wav e strongly depends on the coastal and sea bed topography. If the impac t occurred near the shore, the huge mass of water strikes the cliffs a nd the near shore mountain ridges and can cause displacement of the ro cks, initiate landslides, and change the relief. Thus, impact into oce ans and seas is an important geological factor. Cosmic bodies of small sizes are disrupted by aerodynamic forces. Fragments of a 100-m radiu s comet striking the water surface create an unstable cavity in the wa ter of about 1 km radius. Its collapse also creates tsunami. A simple estimate has been made using the light curves from recent atmosphere e xplosions detected by satellites. The results of our assessment of the characteristics of meteoroids which caused these intense light flashe s suggests that fragments of a 25-m stony body with initial impact vel ocity 15 to 20 km/sec will hit the surface. For a 75-m iron body strik ing the sea with a depth of 600 m, the height of the wave is 10 m at 2 00-300 km distance from the impact.