摘要
Science公布的2018年十大科学突破之一,是在地球北极圈格陵兰岛西北部的Hiawatha冰川下,发现了一个直径约31km的大型撞击坑[1](https://vis.sciencemag.org/breakthrough2018/finalists/#cell-development).该项成果由丹麦哥本哈根大学Kjaer为首的国际科学家团队[1]完成,于2018年11月发表在Science Advances上.该团队利用1997~2016年间的机载雷达测声探测资料,对格陵兰岛冰盖区域冰层和冰下地形进行研究时,在西北部Hiawatha冰层之下发现了一个圆形洼陷区域,直径约31km,深约800m.中间有个微小的隆起以及零星、类似中央峰环的痕迹.
Large impact events could cause huge environmental changes and ecological disasters on Earth. Therefore, the possibility of impact events is always considered as a potential cause of sudden climatic, environmental and ecological hazards. Vice versa, a large impact event can also be used to assess its impact on the environmental and ecological systems. In 2018, the Kj?r team discovered a new 31 km diameter impact crater under the Greenland ice sheet. On the basis of regional airbone radar sounding studies, the Kj?r team identified a circular depression with small peaks in the center underneath the northwest Greenland Ice Sheet. They then carried out ground-based field studies of the deglaciated forland deposits and found shocked quartz and some impact-related grains. These pieces of evidence provided compelling evidence that the depression under the ice was an impact crater(now named Hiawatha). The Hiawatha crater is now the best morphologically preserved large complex crater on Earth and it has been listed as one of the breakthrough discoveries of the year 2018 by Science. It has attracted significant attention because it’s located in Greenland and its potential link with the Younger Dryas Event in the last ice age. The Younger Dryas Event is one of the most significant environmental and ecological event in the Quaternary era and the trigger for this event has been debated for a long time. According to the impact hypothesis, one or more extraterrestrial objects hit(or exploded over) the Laurentide Ice Sheet about 12900 years ago and caused extensive wildfires, megafaunal extinctions and changes in the human population. Despite much criticism initially leveled at the impact hypothesis, the controversy continues to this day and new evidence, both in favor and against the hypothesis, continues to be published. The newly discovered Hiawatha impact crater might be one more piece of evidence supporting the impact hypothesis as the trigger of the Younger Dryas Event. However, due to the lack of solid evidence supporting both a temporal correlation and a causality, the available data reported in this study could not prove that there is an unequivical causal relationship between the two events. To prove the cause and effect link between these two events, additional studies should be carried out, including:(1) To determine the time of the Hiawatha impact event;(2) to determine the distribution of Hiawatha impact ejecta and assess its environmental and ecological impacts;(3) to conduct comparative study of geological records related to the Younger Dryas Event in North America and other regions, and assess their causalities;and(4) to simulate the impact process and its climatic and environmental effects, and evaluate the possibility for causing the Younger Dryas Event and its related geologic record. In summary, the discovery of the Hiawatha crater provides an excellent frame of reference for the study of impact craters on extraterrestrial bodies. Given the importance of the impact itself and its potentially very significant effects on climate and ecological environment, the discovery and analysis underline the importance of the search for and identification of impact craters on Earth, and assessment of their potentially global geological, environmental and biological effects throughout Earth history.
作者
肖龙
Long Xiao(School of Earth Sciences,China University of Geosciences,Wuhan 430074,China;Center for Excellence in Comparative Planetology,Chinese Academy of Sciences,Hefei 230026,China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2019年第22期2270-2273,共4页
Chinese Science Bulletin
基金
国家自然科学基金(41772050)资助
作者简介
肖龙心,岩石学及行星地质学家,现任中国地质大学(武汉)教授、澳门科技大学特聘教授.长期从事岩石学和行星地质学教学和科研工作.在类地行星火山作用及表面地质过程、火星与地球的对比研究、月球地质研究、地幔柱岩浆作用、火成岩成因等方面,取得了多项重要成果.E-mail:longxiao@cug.edu.cn.
