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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Effect of ice sheet thickness on formation of the Hiawatha impact crater
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Effect of ice sheet thickness on formation of the Hiawatha impact crater

机译：冰盖厚度对HiaWatha冲击式火山口形成的影响

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摘要

The discovery of a large putative impact crater buried beneath Hiawatha Glacier along the margin of the northwestern Greenland Ice Sheet has reinvigorated interest into the nature of large impacts into thick ice masses. This circular structure is relatively shallow and exhibits a small central uplift, whereas a peak-ring morphology is expected. This discrepancy may be due to long-term and ongoing subglacial erosion but may also be explained by a relatively recent impact through the Greenland Ice Sheet, which is expected to alter the final crater morphology. Here we model crater formation using hydrocode simulations, varying pre-impact ice thickness and impactor composition over crystalline target rock. We find that an ice-sheet thickness of 1.5 or 2 km results in a crater morphology that is consistent with the present morphology of this structure. Further, an ice sheet that thick substantially inhibits ejection of rocky material, which might explain the absence of rocky ejecta in most existing Greenland deep ice cores if the impact occurred during the late Pleistocene. From the present morphology of the putative Hiawatha impact crater alone, we cannot distinguish between an older crater formed by a pre-Pleistocene impact into ice-free bedrock or a younger, Pleistocene impact into locally thick ice, but based on our modeling we conclude that latter scenario is possible. (C) 2021 Elsevier B.V. All rights reserved.
机译：在格陵兰岛西北部冰盖边缘的海瓦塔冰川下发现了一个巨大的假定撞击坑，这重新激发了人们对厚冰层大撞击性质的兴趣。该圆形构造相对较浅，呈现出较小的中央隆起，而预期的是峰环形态。这种差异可能是由于长期和持续的冰下侵蚀造成的，但也可能是由于格陵兰冰盖最近的一次撞击造成的，预计这将改变最终的陨石坑形态。在这里，我们使用水代码模拟来模拟陨石坑的形成，改变撞击前的冰厚度和晶体靶岩上的撞击器成分。我们发现，冰盖厚度为1.5或2 km时，形成的陨石坑形态与该结构的当前形态一致。此外，厚厚的冰盖实质上抑制了岩石物质的喷出，这可能解释了如果撞击发生在晚更新世，大多数现有格陵兰深冰芯中没有岩石喷出物。仅从假定的Hiawatha撞击坑的当前形态来看，我们无法区分由前更新世撞击无冰基岩形成的较老陨石坑，或由更新世撞击局部厚冰形成的较年轻陨石坑，但根据我们的建模，我们得出结论，后一种情况是可能的。（c）2021爱思唯尔B.V.保留所有权利。

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