I didn’t realize Greenland had that much “old” surface. There’s not much crust left that’s over 1 billion years old.
At least, that hasn’t been extensively remodeled at some point.
Over the 3 billion years since the impact, the land has been eroded down to expose deeper crust 25 km below the original surface. All external parts of the impact structure have been removed, but the effects of the intense impact shock wave penetrated deep into the crust - far deeper than at any other known crater - and these remain visible.Just... WOW!
Is this visible now because there has been more melting of the ice or did people just not recognize it before?