The Black Sea used to be a freshwater lake. Perhaps 7,600 years ago a natural dam at the present Bosporus Strait crumbled, allowing the Mediterranian Sea to flow into the basin. At some earlier time, the Atlantic Ocean overcame the natural dam at Gibraltar to create the Mediterranian Sea.
Doubtless this will happen again eventually. But where? I can think of the San Andreas Fault ripping into California, allowing the Sea of Cortez to flood basins to the north. Seems the Rift Valley in Africa is a prime candidate for a Great Flood.
Until recently, New Orleans. Other places include Venice, which already is overwhelmed by high tides, London by the River Thames, the Netherlands have taken elaborate anti-flood measures etc…
Typically areas of high flood risk already have at least some protection.
I’m talkin’ about a GREAT Flood. Not like New Orleans, Venice, et al. More like a basin that is separated by land from a body of water, and where it is likely that the land (natural dam) will be overcome in the future and that a large (Black Sea or Mediterranian sized) area will be flooded.
I’m thinking that the entire Central Valley of California looks like it’s going to fill up and be the Central Bay of California, given rising sea levels and the inevitable Big Earthquake.
There simply isn’t anyplace else on Earth of that scale below present sea level. There are some areas in North Africa, and there is the Dead Sea area in Israel Jordan, but they are much smaller. Part the Caspian Sea basin is below sea level, but most of that is already filled by the Caspian.
Death Valley is below sea level, and it fits the scenario as I envision it.
I used to live in the Antelope Valley (Northern Los Angeles County, at the extreme Western edge of the Mojave Desert). The airport there is 2,437 feet. Edwards AFB is lower, but still fairly high above sea level. (It’s the high desert.) I can imagine the San Andreas Fault ripping California like a zipper as the Pacific Tectonic Plate moves Los Angeles slowly northward to become a suburb of San Francisco. But in addition to the high desert being between the Sea of Cortez (I’d have to look at a map, but I think that’s the likely place for the water to come from) and Death Valley, there are some moderately-sized mountains. The Escondido Summit on the 14 between the San Fernando Valley and the Antelope Valley is around 4,000 feet. The San Gabriels approach (or exceed?) 10,000 feet. And it’s about 200 miles from the AV to DV. Are the mountains growing? I don’t remember. But they came from somewhere, so I’m guessing that the Pacific Tectonic Plate vs. the North American Tectonic Plate might still be pushing them up.
But I didn’t specify a time-frame. In a million years…?
There are several places, such as the East African Rift system and Death Valley, where relatively small scale flooding would occur, but these are not nearly as large as the Black Sea and Mediterranean basins.
The Mediterranean and Black Sea are so large because they were not created by *rifting * of tectonic plates, but rather by their convergence. Europe and northern Asia was once separated from Africa and India by a wide sea called the Tethys. As Africa and India moved north, the Tethys gradually became smaller; its remnants are the Mediterranean and Black Sea. During periods when the entrances to these seas have been blocked by tectonic shifts or changes in sea level, they dry out. They are basically ocean basins that at times have dried out, rather than parts of continents that have flooded.
Sorry. I shouldn’t have mentioned ‘size’. What I was really getting at was differentiating between costal flooding like in New Orleans, Bangladesh, etc., and flooding caused by a natural and lon-lived land formation giving way.
As I understand it, there was a massive cataclysmic flood released during the recession of the glaciers during the last ice age.
A large lake of glacial meltwater was enclosed within a rim of retreating glacial ice. As the ice continued to melt and recede, the lake got bigger and the walls thinner. It burst impressively, needless to say. You can read a bit about it on Wikipedia or you can visit one of its still-living relics at Dry Falls, estimated to be the greatest waterfall of all time. Very impressive, as I recall.
In theory, given a million years, another such thing could happen nearly anywhere in the northern hemisphere.
I’m currently living in the Imperial Valley in California, and we’re about 50 miles from the Sea of Cortez. I know that’s quite a barrier to overcome, but somewhere between here and there, the elevation takes a dip. The water tanks here somewhat whimsically have “Sea Level” painted on them, and the line is about 40 feet up.
I know you have to crest 4000 feet to get to San Diego, though, so it might be that there are mountains making quite a barrier to the SoC flooding this valley for any forseable future.
Along the lines of the Black Sea flood/creation, IIRC the same proponents have looked to the basin below where the Nile enters the Med., among other things, to determine that at one time the Straits of Gibraltar may have been solid, holding back the Atlantic from a much, much shallower Mediterranean, until one day…
That one didn’t end up creating a sea but it well could have. Any natural basin would do. Since the technique presupposes an Ice Age, imagining some new appropriate land contours is easy.
I vote we put the new lake near the other Great Lakes. Then we’d mess up every crossword puzzle in history because HOMES would no longer be an mnemonic for their names. If the new lake starts with a W we could change the mnemonic to SHOWME.
The Army Corps of Engineers maintain a dam that keeps the Mississippi River from changing its course to the Atchafalaya River, which is lower than the current bed of the Mississippi. The Corps says eventually the river will conquer their best efforts, and the port of New Orleans will be useless.
