[mjb]

For comparison, this is between 4 and 5 times larger than the Osceola Mudflow (https://en.wikipedia.org/wiki/Osceola_Mudflow) that formed the 550km² of fertile plains around the south end of Puget Sound (near Seattle) and knocked a huge chunk out of Mount Rainier. If you drive from Auburn to Enumclaw, for example, notice how flat the land is and think about how that was hilly Cascade foothills and glaciated drumlins until 5500 years ago. The Osceola event was way bigger than Mt St Helens, and this one in the Himalayas was way bigger even that that.

Back-of-envelope, that Osceola event released about 10^19 Joules of energy*. The scale of these things is absolutely incredible.

According to my father, until around the time he was doing Geology at university (late 1960s), the consensus was that these kinds of events (and mass wasting more generally) were geologic processes that no longer happened (and hadn't really happened throughout the Holocene). I don't know the history in detail there, but it does seem true that only relatively recently we've had a real appreciation for how active Earth's geology still is.

* 4e15 cubic centimeters of material, 2 g per cc mix of rock and ice, mean elevation change 1000m

[poulsbohemian]

>that formed the 550km² of fertile plains around the south end of Puget Sound (near Seattle) and knocked a huge chunk out of Mount Rainier. If you drive from Auburn to Enumclaw, for example, notice how flat the land is and think about how that was hilly Cascade foothills and glaciated drumlins until 5500 years ago.

I grew up in this area... there are two tragedies that most people living in this area don't realize. One, before the war a good chunk of the region was populated by people of Japanese origin who farmed and never got their farms back after the war, and two, it is some of the richest farmland in the world - now covered with concrete tilt-up warehouses, highways, etc. Humanity is interesting.

[a_t48]

Also grew up there. The soil was _very_ rich.

[mjb]

Related, there's a cool transition if you hike up the Greenwater river (starting at the town of Greenwater, heading towards FS70) there's a cool transition where the geology switches from Osceola mud to the more typical Cascade foothill geology (about half a mile from the White river).

[sjkoelle]

its a real geologic zoo around there

[mjb]

It really is a zoo (and the whole of Western Washington is generally). If you're interested in the topic, I really enjoyed https://www.amazon.com/Roadside-Geology-Washington-Marli-Mil...

[geostupid]

Love the geologic zoo!

I refer to botanical gardens as 'botanical zoos' as well

[User23]

I believe zoo is short for "zoological garden," but of course it's taken on additional meanings. Still, one occasionally hears the term "zoological and botanical garden."

[farnsworth]

Wild to think about the fact that there were people living there who would have seen (or been buried) by that. Same with some of the cataclysmic floods and other events that came with the end of the last ice age.

[masklinn]

> According to my father, until around the time he was doing Geology at university (late 1960s), the consensus was that these kinds of events (and mass wasting more generally) were geologic processes that no longer happened (and hadn't really happened throughout the Holocene). I don't know the history in detail there, but it does seem true that only relatively recently we've had a real appreciation for how active Earth's geology still is.

I can’t fathom how we could think that, surely as long as plates move around and stone weathers this sort of geological events can happen?

They’re certainly not common on historical timescales, so the odds you’d find yourself sharing time (let alone space) with one are low, but what would have made them stop?

[marssaxman]

Geology went hard for uniformitarianism during the 19th century as a reaction against the earlier "catastrophist" worldview, which had interpreted all major land forms as consequences of the great global flood described in the Bible (or something like it). This yielded a strong preference for theories involving continuous processes operating over long spans of time, and skepticism of theories involving sudden, violent changes. This swung back to a better balance during the 20th century; with the ghost of Noah's Ark exorcised, the role of local "catastrophes" in geologic history could again be taken seriously.

[bombcar]

Wasn’t there some massive icedam caused lake that was the size of basically the entire Pacific Northwest and it flooded out in a matter of years? And nobody believed that could happen.

[matt_morgan]

Right, figuring that out was an important step in our appreciation that catastrophes happen and are impactful on a large scale, you know, not just little things that get covered up by longer-term, consistent processes.

https://en.wikipedia.org/wiki/Glacial_Lake_Missoula

It's why western Washington state is all https://en.wikipedia.org/wiki/Channeled_scablands

[astrange]

The Mediterranean may also have been filled in a single event over a few months: https://en.wikipedia.org/wiki/Zanclean_flood

[mjb]

Plate techtonics was very new (and rather controversial, as I understand it), science in the late 1960s: https://en.wikipedia.org/wiki/Plate_tectonics#History_of_the...

[WalterBright]

My grandfather (a vulcanologist) set up measuring stations in Iceland in the 1930s to prove that Iceland was spreading apart. Unfortunately, the war interrupted that, and he died in the war.

[pyinstallwoes]

Any more insights into his research and measurements that you know of? Thanks for sharing.

[WalterBright]

https://de.wikipedia.org/wiki/Ferdinand_Bernauer

"His greatest contributions to the academic world – proof of Continental Drift through his studies in Iceland and a crystal growing method now lost to mankind – attest to his considerable intellect and dedication."

https://expo.uw.edu/expo/apply/494/proceedings/show?id=68965

"Geschichtete Lava an islaendischen Vulkanen" von Ferdinand Bernauer, Berlin-Charlottenburg

Zietschrift der Deutschen Geologischen Gesellshaft Heft 2 Band 89 Berlin 1937 / Verlag von Ferdinand Enke in Stuttgart

[fsckboy]

>I can’t fathom how we could think that, surely as long as plates move around and stone weathers this sort of geological events can happen?

I learned recently (can't remember where, or how reliable) that plate tectonics did not create mountain ranges till carbon life had been around for awhile, because the carbon layers left behind are slippery (graphite) and allow one plate to slide over another plate. Prior to that, the plates simply pulverized each other.

anybody know if this is true?

[swamp40]

They would mostly stop because now the Earth is nicely round. Most of the original bumpiness created during Earth's creation has been smoothed out. That's probably what he meant.

[qup]

I've heard that the earth, if scaled down to the size of a pool/billiards ball, would be smoother than the ball.

I often use that to explain how spinning cue balls can manage to change the angle of the shot, given the same impact point as a non-spinning cue ball, in an effect pool players call "throw." [1]

The peaks and valleys of the pool ball will reliably grip like gears. Sometimes the balls even stick together momentarily before they release, changing the outcome of the shot, in another effect called "skid". [2]

Also the referenced site is an amazing deep-dive into a niche topic, worth a glance--especially the high speed videos demonstrating the physics of the game.

[1] https://billiards.colostate.edu/tutorial/throw/ [2] https://billiards.colostate.edu/resource_files/onoda_skid_ar...

[vba616]

"No, Earth is not as smooth as a billiard ball! ... The billiard-ball-sized Earth’s smoothness would be equivalent to that of 320-grit sandpaper."

https://ourplnt.com/earth-smooth-billiard-ball/

A comment on the article, though, says "I’d like to point out that Earth is about 3400 times flatter than a regulation pool table...I love saying it – The Earth is flatter than a pool table!"

[qup]

F

[ftxbro]

> "Back-of-envelope, that Osceola event released about 10^19 Joules of energy*. The scale of these things is absolutely incredible."

I wonder can we put a kind of "earth turbine" to capture some of that energy? Maybe tap it somehow to not release all in one catastrophe and make it safer at the same time.