Gradually, and then Suddenly
March 29, 2018 2:30 PM   Subscribe

Building on an earlier hypothesis and using a new stratigraphic analysis of part of the Mediterranean seafloor, scientists have discovered new evidence which provides a convincing argument (and video!) for their their hypothesis about the Zanclean Flood, which rapidly refilled the Mediterranean over a mile-high waterfall and ended the Messinian Salinity Crisis.

Scientific American has a summary of the research.
Micallef and his colleagues focused on the Malta Escarpment because megaflood water flowing east would have encountered this natural blockade, making it a logical place to find sediments deposited by water that breached the cliff. The researchers used seismic reflection imaging, which involves directing sound waves toward the sea bottom and measuring the time it takes them to return. Essentially an x-ray of the seafloor, this technique allowed the team to reconstruct the thickness and likely composition of buried sediment layers.

One of those layers stood out from the others; it was a jumbled mix of angular pebbles and boulders. “It doesn’t have internal layering like marine sediments normally do,” says Garcia-Castellanos, who was also a co-author of the new study. This irregularity implies the sediments—up to 800 meters thick in places—were laid down “quickly and haphazardly,” Micallef says, consistent with the material being transported by rushing water. Furthermore, this layer lay just to the east of Noto Canyon, a large undersea gorge running through the Malta Escarpment. The canyon bears a curious geologic scar on its western side; a channel 400 meters deep runs through its hard limestone. This feature, similar to the signatures of erosion seen near the Strait of Gibraltar, was probably caused by flowing water, the researchers reasoned. “We think we found this breach just to the southeast of Sicily,” Micallef says.
Previous megaflood discoveries include the formation of the Channeled Scablands in eastern Washington, where a once-dismissed theory of a glacial megaflood is now supported by evidence of multiple floods, and the English Channel. Those two both apparently resulted from ice age formations that allowed massive lakes to form from glacial melting, and then ruptured in great floods. The Zanclean flood appears different in that both the closing of Gibraltar and its eventual reopening were due to tectonic processes.

Despite the wishes of Young Earth Creationists, however, it still looks like the Grand Canyon was formed by slow erosion and not a biblical flood.
posted by fedward (20 comments total) 50 users marked this as a favorite
Thanks for this post. I am enormously ... comforted, if that is the right word, by the idea that the Mediterranean Sea is not a permanent thing.

Somewhere I read the simple statement that every lake is temporary, and it set me back on my heels.
posted by Countess Elena at 2:49 PM on March 29, 2018 [5 favorites]

One of my favorite daydreams is to be a time-tourist, who uses a time machine to experience various moments in history. I'd do stuff like visit Disneyland on opening day, drink the first glass of Coca-Cola, that sort of thing. Going back and witnessing a mile-high ocean waterfall is going pretty high on the list.

(P.S. I know Disneyland had a terrible opening day and the first Coca-Cola had cocaine in it. That's part of the fun.)
posted by Mr.Encyclopedia at 2:53 PM on March 29, 2018 [10 favorites]

“Messinian Salinity Crisis” is my favorite Robert Pollard album.
posted by ardgedee at 3:39 PM on March 29, 2018 [6 favorites]

I am enormously ... comforted, if that is the right word, by the idea that the Mediterranean Sea is not a permanent thing.

None of the oceans are permanent!
posted by thelonius at 4:25 PM on March 29, 2018 [1 favorite]

I am enormously ... comforted, if that is the right word, by the idea that the Mediterranean Sea is not a permanent thing.

There is something hugely comforting, in a nihilistic sort of way, in the depth of geologic time.
I work in land conservation. It can be a very depressing field. I visited Glen Canyon Dam on the Colorado River. The river used to alternate between a torrent and a trickle of warm water that was "too thick to drink, too thin to plow". That annual gush of sediment scoured out the Grand Canyon. Now the river is a year-round steady trickle of cold, perfectly clear water. I looked at the dam and thought "we have killed this river, killed the process that built the canyon".

Then I went to the bottom of the dam, and floated down the river, and looked up, and saw hundreds of millions of years of strata above me, and realized that the oldest structures in the world are a few thousand years old, and there is no way that dam will last more than a few hundred years. And I thought about how everything humans have done to the planet will one day be reduced to a few-mm-thick stratum enriched in plastics and radioisotopes. And I somehow found that unbelievably, inexplicably comforting.

Anyway, I love this post. I particularly liked the bit where the sea level in the Mediterranean rose by 10m per day for years. That time the tide came in fast, and just would not stop coming in.
posted by agentofselection at 4:32 PM on March 29, 2018 [27 favorites]

ObSF: Randall Garrett and Vicki Ann Heydron, The Gandalara Cycle.
posted by Chrysostom at 5:01 PM on March 29, 2018 [1 favorite]

Also on the SF front, I probably should have included xkcd 1190, which [spoiler] imagines a future event like the one in the top of this post (previously).
posted by fedward at 5:10 PM on March 29, 2018 [6 favorites]

The drying and refilling of the Mediterranean is a key plot twist of one of Randall Munroe's comics. (Spoiler as to which in the link title.)
posted by tavella at 5:13 PM on March 29, 2018

> and realized that the oldest structures in the world are a few thousand years old, and there is no way that dam will last more than a few hundred years.

Look on my works, ye mighty, and despair!
posted by I-Write-Essays at 5:14 PM on March 29, 2018 [3 favorites]

None of the oceans are permanent!

The continents also warp and split and collide and do things we're only beginning to figure out. We learned about Pangaea in school, but not Rodinia or any of the other previous supercontinents, and there's a fault under the central US that dates to a rift that formed during the breakup of Rodinia (when the predecessor continent to North America almost broke apart, but then didn't).
posted by fedward at 5:22 PM on March 29, 2018 [4 favorites]

There is a similar hypothesis regarding a mega flood on the Black Sea. Except this one is hypothesized to have occurred around 5600BC or well within the oral history of neolithic people who lived in the area. It has been put forward as the origin of the Flood story in the bible.
posted by Mitheral at 8:18 PM on March 29, 2018 [1 favorite]

I wonder how much, if any, narrative gets embedded deep within our psyche genetically.

We look at landmasses and see how they could match up, then seek appropriate evidence to prove it. How much "pattern matching" quality of our brains does it take to tell that story internally without passing it between individuals (with similar stories running within)? Or do we just have such a mass of content exposed to us that even by osmosis we gain this narrative?
posted by filtergik at 4:24 AM on March 30, 2018

The radio show On Being had an episode about the biblical flood, looking for a connection to the geological record.
posted by kokaku at 6:33 AM on March 30, 2018 [2 favorites]

one of the best things about geology is it's sort of the oldest of modern sciences, so they've stuck with a very 19th-century aesthetic for naming things. I had no idea there was such a thing as the Zanclean age.
posted by vogon_poet at 8:17 AM on March 30, 2018

I could watch that video over and over and over.
posted by mareli at 10:39 AM on March 30, 2018

More, earlier, ObSF: The Saga of Pliocene Exile by Julian May is riproaring fun, providing around-the-Med viewpoints on the changes wrought by flooding (observered by time travelers from the future, it's complicated).
posted by Jesse the K at 3:08 PM on March 30, 2018 [2 favorites]

More SF: Down in the Bottomlands by Harry Turtledove, an alternative history where the Mediterranean Sea never flooded.
posted by Gortuk at 8:21 AM on March 31, 2018 [1 favorite]

There is a YA series about people who unbeknownst to them live in the dry Mediterranean basin; and it is slowly filling. It features big cats and a lack of wood (an intact log is a king's treasure). Anyone recall the name?
posted by Mitheral at 12:58 PM on March 31, 2018

I love science and geology posts, thank you!

On an extremely scientific note, then, ;) what bearing does this finding have on the myth of the Lost City of Atlantis?
posted by salvia at 2:09 PM on March 31, 2018

Mitheral: "Anyone recall the name?"

It's The Gandalara Cycle. Thanks Rhaomi.
posted by Mitheral at 7:40 PM on March 31, 2018

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