Thread by @Mikeachim

I recently learned something mindblowing about the geological history of the Mediterranean Sea, and I just can't get it out of my head.

Now I'm going to make it *your* problem too. Sorry.

Hang onto your hat. This is wild.

1/

This is the Strait of Gibraltar, where Europe and Africa reach out to *almost* touch each other.

At this point there's only 13 km/ 8 miles between them - and it's where the Med feeds into the Atlantic.

Imagine if something absurdly Roland-Emmerichy happened & it closed up?

2/

No need to imagine - because it actually did.

It's called the Messinian Salinity Crisis, and it happened around 5-6 million years ago:

en.wikipedia.org/wiki/Messinian…

After a presumably colossal tectonic shift, the Pillars of Hercules closed (or more correctly were bridged)....

3/

...and the Mediteranean started drying up.

After some undetermined period of time, the Mediterranean was empty - evaporated down to a desert & a series of huge, super-salty lakes.

A vast, salty desert bowl - *kilometres* deep.

(This is not the wild thing.)

4/

The desert bowl of the western Med was also noticeable higher than the east.

You can see this in modern sea floor maps: shallower continental crust in the west, deeper oceanic in the east - connected at the modern-day Strait of Sicily...

And primed for another cataclysm.

5/

Before I read about this, I assumed that at some point the Strait of Gibraltar cracked, the water rushed in, and over centuries or millennia, our modern Mediterranean was created.

That's a manageable thought, right? Epic in scale, but - thinkable.

That's not what happened.

6/

Modern borehole and siesmic data has uncovered huge grooves through the rock on either side of the Gibraltar Strait - each around 250 metres deep...

And there's a channel along the bed of the sea floor, carved with unimaginable force.

It's around 200km long.

7/

At some point, maybe after a massive earthquake, the landlocked cliffs at the Strait were forced aside and the Atlantic rushed in with *mindboggling* fury.

Not a waterfall, but a long slope - down which roared up to *100 million cubic metres of water a second*.

8/

I'm keeping the nerdy geological details pretty light here. There's so much, and it's all on an incredible, mindbending scale.

If you want to geek out further, I'll have a newsletter on all this next week. Sign up for free here:

everythingisamazing.substack.com

OK, back to it.

9/

This flood, descending a kilometre to the sea floor, had a thousand times the discharge of the modern Amazon...

And it refilled 90% of the West Med in a YEAR.

This was 5 (or 6) million years ago. Did any of our distant ancestors see it?

Can you imagine their terror?

10/

(One year. Or perhaps even less time. Or perhaps a couple of years!

(The point here is: this DIDN'T take centuries, or even decades. It was terrifyingly fast.

(It must have seemed like the end of the world.)

11/

If you're disappointed that the breached Straits of Gibraltar didn't form a spectacular waterfall - look to the east of this artist's reconstruction, courtesy of Wikipedia.

Remember that the eastern Med is a lot deeper?

South of Sicily, there's an underwater cliff...

12/

The flood roared over it at around 160 miles an hour, forming a waterfall over 1.5km high.

And to the east, the deeper desert bowl of the dessicated Mediterranean started filling with water - rising up to 10 metres a day.

*Not* a typo.

13/

The name for this astounding event is the ZANCLEAN MEGAFLOOD:

en.wikipedia.org/wiki/Zanclean_…

I've put it in All Caps because, what a hilariously epic name. I burst out laughing when I read it.

Anyone searching for a name for their new rock band?

14/

So now I'll leave you to do your own reading - although, if you want my own excitable take on all this, I'll have something in my newsletter next week (everythingisamazing.substack.com/about)

And also? Let me say this very loudly:

AS YOU CAN SEE, GEOLOGY IS NOT BORING.

Thanks for reading. :)

And lastly, since this is starting to go a bit nuts with shares & likes (thank you!) - you may also enjoy this thread I did in December, about light pillars:

https://twitter.com/Mikeachim/status/1466763517487370246

Ta!

And! A hat-tip to @frod_san for steering me towards this reconstruction of the Mediterranean flood:

https://twitter.com/frod_san/status/1491168739609354241

And and! @math_vet reminded me that the Zanclean Megaflood featured in one of the finest things on the Web:

https://twitter.com/math_vet/status/1491211079523119112

You really should check it out. It's a wonderful journey.

OK. Breaking from this Big Terrifying Geological Nope No Thanks theme for a second, I'd like to recommend to you some other curious, interested writers.

1) Mr @douglasmack, a travel writer who now has a delightfully curious newsletter about snacks: snackstack.net

2) Jodi (@legalnomads) whose newsletter is the aptly-named Curious About Everything: jodiettenberg.substack.com

Read this just-published piece by her at CNN to learn what a terrific writer she is: edition.cnn.com/travel/amp/jod…

3) The mighty @celbrash, ridiculously accomplished travel writer (recently in National Geographic) who can currently be found farming pearls in Tahiti: kamokapearls.com

Her daily life is ridiculously interesting (sorry, Celeste, but it's true). Follow her for the stories.

If anyone''s interested: in advance of my Zanclean Megaflood writeup, here's why this season of my newsletter is about the 71% of the Earth's surface we have a tendency to tune out (because we're massively biased that way):

everythingisamazing.substack.com/p/from-the-rid…

Ta.

ANOTHER UPDATE:

My Megaflood writeup's a few days delayed - for the best of reasons! Because of the *bonkers* reaction to my Twitter thread, I ended up with dozens of new rabbit-holes to scurry down. What a journey.

Thank you for all the suggestions! Hope I can do them justice.

At long last - here's my newsletter on the Zanclean Megaflood, with a lot more detail and some huge numbers that will *really* make your head hurt:

everythingisamazing.substack.com/p/in-search-of…

Whew. What an absolute thing.

OK. I need sleep.

And it turns out that Britain has its own Megaflood story, much more recently - and involving highly terrified prehistoric people:

https://twitter.com/Mikeachim/status/1507401667347730435

And as a reminder that xkcd continues to do the most experimentally interesting and creatively pants-off bonkers things on the Internet, here's today's delightful barminess:

https://twitter.com/waxpancake/status/1510041568631160834

My latest thread! No need to cast your imagination back in time for this one - it's about what the bottom of the Atlantic looks like, right *now*:

https://twitter.com/Mikeachim/status/1518263121374236672