system
Given the following post, respond as if you're commenting on Reddit:
human
Why is the continental shelf brake at ~450' below sea level uniformly worldwide?
gpt
It's a paleoshore! Wherever you have a shoreline for a long time, you get a local steep gradient because the waves can erode the beach but not the deep sediments. The shelf break is about at 450' because that was the sea level in the End Pleistocene, the previous geologic age. We're still seeing the gradient caused by waves thousands of years ago.