Sediment collected from beneath Hiawatha Glacier contained shocked quartz, quartz grains with brown 'toasting,' and minerals altered by shock metamorphism into glass.
Notes on verification
Confirmed by the original peer-reviewed Science Advances study and multiple independent secondary sources, including the research team's own site and science news outlets. All specific mineralogical details match. [cascade flags: wikipedia_dropped_other_sources_exist | tier=silver indep_score=0.867 clusters=3 claim_tier=notable]
Sources
- City-size impact crater found under Greenland ice (seed:history_and_archaeology)
- https://www.science.org/doi/10.1126/sciadv.aar8173 (corroboration)
- https://www.sci.news/othersciences/geoscience/hiawatha-impact-crater-greenland-06610.html (corroboration)
- https://craterexplorer.ca/hiawatha-impact-crater/ (corroboration)