I've been trying to think through what these things are like and what they are doing ~ first off they'd be detectible only from space, and at the same time they could cause some sea levels on some shores to drop.
They probably explain the biological anomaly discovered in Alaska a couple of decades back. The guy found the terminal forests were at a lower elevation than the immediate post Ice Age bogs along the rain forest area South of Juneau. The theory had been that the bogs came first, then the trees, but there the trees came first then the bogs.
The only way to explain it was for the sea level in that region to be dropping while it was rising further up the coast North of Juneau. However, there were no geological signs of subsidance.
The guys who have the job of understanding this currently put little store in sea level data having much relevance to anything ~ particularly no the predictions of cities being flooded suddenly while their citizens stand there dumbfounded and drown.
Your first line. Yes. That’s why if the earth ever gets something that tilts its axis rather violently all that momentum is going to cause catastrophic flooding.
There is evidence of very thick salt deposits on the bottom of the Mediterranean Sea. When the Ice Age ended the water was probably much evaporated, and only when the ocean level was as high as the bottom of the Straits of Gibralter did it start to refill. There may have been times as the level became higher and the bottom more eroded that the ocean rushed it with a great flood.