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.

沿着西北格陵兰冰原边缘在Hiawatha冰川下埋藏的一个大型推定撞击坑的发现，激发了人们对浓厚冰团大撞击性质的兴趣。这种圆形结构相对较浅，并具有较小的中心隆起，而峰环形态是可以预期的。这种差异可能是由于长期和持续的冰川下侵蚀造成的，但也可以通过格陵兰冰原的相对较新的影响来解释，这可能会改变最终的火山口形态。在这里，我们使用水力代码模拟，在晶体目标岩石上改变预撞击冰厚度和撞击器组成来模拟火山口形成。我们发现，冰盖厚度为1.5或2 km时，形成的火山口形态与该结构的当前形态一致。此外，一块厚厚的冰原会抑制岩石物质的喷射，这可能解释了如果在更新世晚期发生撞击，大多数现有的格陵兰岛深冰芯中就不会出现岩石喷射。从目前仅假定的Hiawatha撞击坑的形态来看，我们无法区分是由更新世前撞击形成无冰基岩形成的较旧火山口，还是由较新世撞击形成局部较厚冰块的较年轻火山口，但是基于我们的模型，我们得出结论后一种情况是可能的。