Marine Target Impacts

摘要: Most cosmic bodies impacting the Earth fall into seas and oceans, which cover more than two-thirds of Earth’s surface. However, among 150 craters discovered on Earth, only 15–20 found recently were formed as a result marine target impacts (Ormo Lindstrom 2000). The deficit underwater is explained by relative youth typical ocean floor (<150–180 Ma), insufficient exploration sea/ocean floor, specific features cratering process. known in shallow seas, where water depth comparable with an impactor size. Eltanin (Gersonde et al. 1997) presently impact structure due to deep (∼4 km) ocean. process has been poorly investigated; however, relations obtained for continental are commonly used estimate parameters craters. A small number numerical simulations performed first stage very large projectiles (∼10 km), interest from viewpoint impact-induced mass extinctions biota (O’Keefe Ahrens 1982b; Roddy 1987). these gave neither shape final crater nor generated tsunami waves. Laboratory experiments (Gault Sonnet 1982) detailed (Artemieva Shuvalov 2002) made it possible determine critical sea at shock-modified material can be found. works (Adushkin Nemchinov 1994; Hills Nemtchinov 1996) estimates based nuclear explosion data modeling initial phase study generation caused comet 4 km depth.