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Comment by tokai | Hacker News Reader

I'm surprised that we do not have any chaos terrain on Earth. Can't find any explanation why. We have had large sudden flood events on Earth, but maybe weathering orders the 'chaos' over time?

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The suggested mechanism is that sedimentary rocks form over ice. That puzzles me in itself, because it implies a river with ice at the bottom. But anyway, then some heat source arrives and melts the ice, causing a sort of rug pull that means the rock layer drops down and breaks up. Kaboom.

I think the most likely case for sedimentary deposition over ice would be something like volcanic eruption or an impact event redepositing material onto pre-existing ice.

At first I thought perhaps it was a non-h20 liquid, since that would explain the frozen bits on the bottom.

Bit apparently it’s more banal, and sediment doesn’t need a river or a liquid at all. It’s any kind of deposit. So wind can deposit sedimen, volcanic ash is sediment glaciers deposit it etc.

We almost certainly did at one point, but life and tides can fill-in the gaps. We also truly do not know what terrain is underneath Antarctica, Greenland, etc.

What? Yes, we do.

https://science.nasa.gov/earth/earth-observatory/uncovering-...

https://sealevel.nasa.gov/resources/75/the-bedrock-beneath-a...

https://commons.wikimedia.org/wiki/File:AA_bedrock_bedmap2.4...

I didn't understand, how is that dissimilar to mountains? Large tilted blocks, hundreds of meters high, hills and depressions...

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