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Effect of ice sheet thickness on formation of the Hiawatha impact crater

By SpaceRef Editor
April 21, 2021
Filed under ,

Elizabeth A. Silber, Brandon C. Johnson, Evan Bjonnes, Joseph A. MacGregor, Nicolaj K. Larsen, Sean E. Wiggins

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.

Comments: 29 pages, 7 figures, 2 tables

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Geophysics (physics.geo-ph); Space Physics (

Cite as: arXiv:2104.07909 [astro-ph.EP] (or arXiv:2104.07909v1 [astro-ph.EP] for this version)

Submission history

From: Elizabeth Silber 

[v1] Fri, 16 Apr 2021 06:19:52 UTC (1,665 KB)

SpaceRef staff editor.