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I think there are two possibilities: either the strait of Gibraltar was suddenly lowered by an earthquake and the atlantic immediately started to flow into the

by lqet 5y ago

I think there are two possibilities: either the strait of Gibraltar was suddenly lowered by an earthquake and the atlantic immediately started to flow into the mediterranean over the entire 13 km (which would have look very different than the video), or the land barrier slowly eroded at some small location until a tipping point, and the water than quickly widened the hole in a few hours/days. In the latter case, I think it is reasonable to assume that it first looked somehow like in the video. But I still agree that is near to impossible to imagine the scale of the peak inflow.

throwaway0a5e 5y ago
Exactly. It's not like a dam breach where you have a constant and steep incline into deep water. You've got a taper up on one side and down on the other. So your initial breach is going to only have a small cross section. You get something like river rapids as a result. And then erosion quickly does its thing, but much less quickly than it does when water goes over the top of a dam because the much shallower grade means that the amount of material that needs to be moved to get a deeper breach increase more quickly than in the case of a dam. The video from Malaysia is water flowing into what was formerly a mine pit so (like a dam) the wall is going to be about as steep as the geology can support. Natural geology tends to create much more mild slopes.
bell-cot 5y ago
Earthquakes don't suddenly lower terrain by much. (Unless the 'quake triggers a landslide...) My two guesses: - The natural barrier was quite low (due to some combination of things). Then waves from either an exceptional storm, or an tsunami, swept over the top - eroding it enough to start the run-away erosion/flooding process. - Setup similar to my first guess, but the soil/rock/bedrock of the natural barrier aren't able to withstand the groundwater pressure and flows. (Think of a slowly-failing dam, with water seeping through it faster & faster.) Wikipedia's best guess: > The most widely accepted hypothesis is that a stream flowing into the Mediterranean eroded through the Strait of Gibraltar until it captured the Atlantic Ocean... (Which is more-specific version of your second idea.)

by lqet 5y ago

throwaway0a5e 5y ago

Exactly. It's not like a dam breach where you have a constant and steep incline into deep water. You've got a taper up on one side and down on the other. So your initial breach is going to only have a small cross section. You get something like river rapids as a result. And then erosion quickly does its thing, but much less quickly than it does when water goes over the top of a dam because the much shallower grade means that the amount of material that needs to be moved to get a deeper breach increase more quickly than in the case of a dam. The video from Malaysia is water flowing into what was formerly a mine pit so (like a dam) the wall is going to be about as steep as the geology can support. Natural geology tends to create much more mild slopes.

bell-cot 5y ago

Earthquakes don't suddenly lower terrain by much. (Unless the 'quake triggers a landslide...) My two guesses: - The natural barrier was quite low (due to some combination of things). Then waves from either an exceptional storm, or an tsunami, swept over the top - eroding it enough to start the run-away erosion/flooding process. - Setup similar to my first guess, but the soil/rock/bedrock of the natural barrier aren't able to withstand the groundwater pressure and flows. (Think of a slowly-failing dam, with water seeping through it faster & faster.) Wikipedia's best guess: > The most widely accepted hypothesis is that a stream flowing into the Mediterranean eroded through the Strait of Gibraltar until it captured the Atlantic Ocean... (Which is more-specific version of your second idea.)