I'm writing a fantasy world that takes Earth's Prehistorical landforms as basis for its geography, and adding a twist to it. I read about the Messinian Salinity Crisis and the Zanclean flood, and how low the oceans got during the Last Glacial Maximum, with sea levels lowering about 125m. This drop doesn't ever comes close to how deep the Gibraltar Strait is, which surpasses 900m.

However, what if The Gibraltar Strait wasn't that deep, and it was instead 100m deep instead on its shallowest parts on the Camarinal Sill, so that in every Last Glacial Maximum, the sill acted like a Dam? Let's also consider no matter how powerful they became, no Outburst floods would ever erode the Sill enough to stop it acting as a dam when the sea levels dropped again, at least during some tens of millions of years. What would be the effects of these periodical deluges, at least in geological timescales, to the European and the World's ecosystems as a whole?

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    $\begingroup$ Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. $\endgroup$
    – Community Bot
    Jul 28, 2022 at 5:54
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    $\begingroup$ Hello Sistine, welcome to Worldbuilding. As written, this question is inappropriate for our Stack. (a) We are not a discussion forum. (b) We don't entertain open-ended, hypothetical questions (see off-topic High Concept Question). (c) This violates multiple rules from our help center, not the least of which is that it's too broad and too opinion-based. Worse, (d) We have a rule that says if you can imagine an answer needing an entire book, the question is bad. Asking how this would effect entire ecosystems meets that restriction. $\endgroup$
    – JBH
    Jul 28, 2022 at 7:15
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    $\begingroup$ The Gibraltar reopened for the last time some 5.3 million years ago, so that there is no time for it to close and open periodically for "tens" of millions of years. And anyway, the amount of salt deposited in the Messinian strata is so large, very much larger than the amount of salt in the water of the Mediterranean, that the common opinion is that the dessication and refilling of the basin happened repeatedly. Overall, the conditions in the question did actually exist, just not during the last 5 million years. $\endgroup$
    – AlexP
    Jul 28, 2022 at 7:54
  • $\begingroup$ I’m voting to close this question because AFAIK "What If?" is not a valid question. $\endgroup$
    – Gillgamesh
    Jul 28, 2022 at 12:15
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    $\begingroup$ I would agree with closing the question, not for inappropriateness, but because the OP is asking "what if the world were exactly like it already is. As @AlexP points out, the described conditions are actually the real conditions, plus or minus time frame. $\endgroup$ Oct 9, 2022 at 21:58

1 Answer 1


What would be the effects of these periodical deluges, at least in geological timescales, to the European and the World's ecosystems as a whole?

There was a period when slightly higher Earth axial tilt was changing rain pattern and Sahara was green so there could have been slightly higher rainfall to balance no inflow from Atlantic. However, there doesn't seem there would be much change, based on proposed mega-project to dam this whole area.


I would expect slightly lower sea level, slightly drier region, slightly saltier Mediterranean sea during that era but otherwise nothing dramatically different. If you are desperate to create some cool new setting this way, then you should presumably pick some slightly lower guesstimate concerning water level, and later pick a river valley in area that right now is 200 m below sea level or some rivers that only under such conditions were able to merge.

no Outburst floods would ever erode the Sill enough

Instead of miracle, you just need some ongoing extra tectonic collision that would be effectively rebuilding this sill in the meantime.


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