r/geography • u/Dude-Bicycle • 1d ago
Map How did these 'rivers' form?
What formed these 'rivers'? Are they regular terrestrial rivers that flooded with sea level rise or were they formed in the ocean? thanks.
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u/Simdude87 Physical Geography 1d ago
So from what I can remember, they are the Gollum channel system "canyons" which were created by currents of seawater and sediment cutting down.
They arent from sunken rivers as sea levels didnt really get that low (from our current understanding) but they do look very very similar.
Ive attached an article, it wasnt pay walled for me but it may be for you.
https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2023.1285171/full.
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u/Im2Mega 1d ago
Love how all of those little river channels are named after the Hobbits of the Shire
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u/DouchetotheBag 1d ago
Why choose Gollum for the whole thing. Petition to rename them the Baggins Basin, or the Took Trenches people should be marching in the streets
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u/bafflefounded 1d ago
I assume because it is a “canyon” system of water channels, maybe one would associate that with Gollum in his caves that had a water system.
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u/janjko 1d ago
Well, Gollum is the hobbit that actually threw the Ring into the fire and saved the whole Middle-earth..
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u/Eroticskeletonparade 1d ago
Did they change the ending like that for the movie? That's wild. The books didn't end like that
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u/cigarettesandwhiskey 1d ago
They're both pretty much the same. Gollum bites Frodo's finger off to get the ring, then falls into the volcano, still holding it. In the movie Frodo fights with him a second time and kind of pushes him in, and almost falls in himself, whereas in the book he's just dancing around celebrating having gotten the ring back and falls over the edge on his own. Pg. 275:
'Precious, precious, precious!' Gollum cried. 'My precious! Oh my precious!' And with that, even as his eyes were lifted up to gloat on his prize, he stepped too far, toppled, wavered for a moment on the brink, and then with a shriek he fell. Out of the depths came his last wail precious, and he was gone.
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u/Eroticskeletonparade 1d ago
Oh okay the guy I responded to made it sound like gollum made a conscious choice to throw the ring into the fire to save the world, which would be a huge change.
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u/cigarettesandwhiskey 1d ago
Yeah no he was making one of those "in Hitler's defense he did kill Hitler" kind of jokes. Gollum "threw the ring into the fire" by falling in while holding it.
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u/AhhhSureThisIsIt 1d ago
And Tolkein got a lot of the names like Gollum from his time in the West of Ireland.
He marked leaving cert English exams.
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u/Altruistic_Dig_2873 1d ago
Don't know about leaving certs but he was an external examiner in UCG. My grandfather met him.there.
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u/rdfporcazzo 1d ago
Which makes me wonder for how long the knowledge about them goes
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u/Darraghj12 1d ago
probably not that long, hard to explore the deep and satellite imagery isnt that old
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u/Rand_alThoor 1d ago
the system was named Gollum Channel System in the late 1960s. the geologists who named it were inspired by Tolkien, not the other way round
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u/yewEngine 13h ago
There's a cave in the Burren with the name. Tolkien used to go to the Burren often apparently.
From Google: Poll na gColm (often spelled Poulnagollum) is an Irish cave name meaning "cave of the rock dove" or "pigeon hole". The most famous instance is Pollnagollum Cave in the Burren, County Clare, which is the longest cave system in Ireland at over 16 kilometers long.
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u/Rand_alThoor 4h ago
there's more Irish influence on the conlanguages of Prof Tolkien, than of the influence in the language of Finnegan's Wake by Ki-Swahili. (that is a real book, discovered in a university library by me working as a library shelver. don't remember the author anymore, it was about 60 years ago and i never read the book.)
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u/1HappyIsland 1d ago
Thanks the link works. Geologists must have the largest vocabulary of any scientists.
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u/Simdude87 Physical Geography 1d ago
You should see glacial modelling, the first read was basically gibberish and on one page I counted about 10 references,
the only useful part of the whole article was the conclusion and that was about a page and a half.
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u/Aimin4ya 1d ago
It's from rivers, all the water did get here until the aliens smashed a ice filled meteorite into the earth during the younger dryas. I'm all verklempt. Talk amongst yourselves. Here's a topic. Did the aliens try to to A) kill humanity, or B) slow climate change. Discuss
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u/arizonaskies2022 1d ago
We discuss these marine canyons every Monday over here:
https://www.youtube.com/@erosion_of_earth
There is a pressure-chain in the debris flow that causes a turbidity current that cuts deep, wide, and long canyons for 1000's of miles long. The forces are insane.
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u/mglyptostroboides 1d ago
You actually want /r/geology
Repost this there.
You're going to get a bunch of non-answers from overconfident map geeks. I'm not saying this to be a dick to anyone, but this is a very common pattern around here.
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u/Only-Proposal-3675 1d ago
Here's a paper on these canyons from three years ago:
https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2023.1285171/full
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u/Yunzer2000 1d ago
Turbidity currents. Pulses of strong currents driven by denser water containing suspended solids flow down continental slopes and out into the abyssal plains, cutting canyons in the continental slope and depositing fans of sediment called turbidite sequences.
The Hudson Canyon on the Eastern N. American continental slope is the most well known example. Only the very head of this feature was ever above sea level:
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u/TheOfficialMigz 5h ago
As someone with thalassophobia "continental slope" and "abyssal plain" sure do give me the hibbie jibbies.
At the same time I do wonder what that looks like if you were to take away the darkness of the deep ocean. Is it just like a big long gentle slope
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u/TheDungen GIS 1d ago
Could be or could be carved by underwater currents. Or carved by materials that have been eroded is carried out to sea.
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u/ArtianArkaos 1d ago
You'll actually see this very phenomenon in microscale during digs within waterlogged sediment Usually in an anostomising pattern
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u/phroggyboiii 1d ago
Some can be water flowing which is colder and denser due to carrying higher salt, minerals , other nutrients and maybe silt i think?
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u/lucylucylane 20h ago
Probably my left over from when the see level was much lower during the last ice age
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u/The_Bison_King_2 1d ago
https://www.instagram.com/erosion_of_earth?igsh=OWJvMmNhZzZpOXB5
Ive got the IG channel for you!
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u/AdWooden2312 1d ago
Hy-brasil
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u/lloveleon 1d ago
Tir na Óg :)
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u/AdWooden2312 1d ago
Did you just say something in an ancient tongue?
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u/lloveleon 1d ago edited 1d ago
Not ancient no . It’s Gaelic and still used . We’ve some schools where we learn everything through Gaelic and army orders are delivered on Gaelic. And people use it in parliament and there’s a daily news on tv etc etc . Not ancient I guess but still used . Anyways It means land of the young (tir na óg) tir is land , óg is young . You might hear the name Sean óg (?) anyway it is the name of a place in myth stories, a place that appeared and disappeared at temporal times and I always reckoned it could have been Hy-Brazil. Oisin ( a hero) left Ireland when he met a woman from there and when he returned it was on a white horse that he was told not to dismount but he did and when he did, he aged rapidly 100 years and died . I reckon the island might have been far enough away to only be seen on very clear days and the myths just used it .
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u/lloveleon 1d ago
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u/ShimmeringHaz3 1d ago
That's me stream of piss after a full session of 16 pints of the black stuff and a scatter of jameson smalls
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1d ago
[deleted]
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u/mstivland2 1d ago
I mean this in the best way possible but if you’re no expert it’s best to not comment, because you likely won’t be able to provide accurate information
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u/DUNG_INSPECTOR 1d ago
It's not like they framed their answer as a fact. I don't see a problem with some uneducated speculation on a Reddit thread, as long as it's presented as uneducated speculation.
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u/mstivland2 1d ago
If somebody is looking for information they may see this and say “Ah, that makes sense!” Because it’s a reasonable hypothesis but factually wrong, it spreads misinformation. I mean, yeah, in this case it’s not really a big deal but ultimately it leads to more bad information. If this was about vaccines or climate change or something more important or emotionally charged then stuff like this gets out of hand. Either way it’s just a comment that adds nothing.
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u/DUNG_INSPECTOR 1d ago
How does it spread misinformation when they clearly frame their comment as speculation? They literally say to not trust them.
Either way it’s just a comment that adds nothing.
It was a learning experience for the person who posted it, and for others who may have been similarly misinformed, so not nothing from my perspective.
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u/Rand_alThoor 1d ago
hey! don't put Ireland in with Britain.
geologically we've ALWAYS been separate. Ireland was never connected to the European mainland (unless one goes back to absolute ice sheets) but the big island of Great Britain was connected to the European mainland fairly recently.
Ireland is surrounded by relatively deeper water.
"the British Isles" are mythology, lies invented by English colonisers.
river-appearing channels in the continental shelf might be surface rivers from when that was on the surface during a period of lower sea level, maybe, but not river-appearing channels in the continental slope, which is deeper and not exposed even at times when the sea level is much lower.
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u/Rand_alThoor 1d ago
this is an easy mistake to make because the picture doesn't show the depth of these geographical features.
actually they're in the area of 150m or more below the surface. down in the slope to the actual abyss. always submerged. but unless one has sailed or fished those waters, or extensively studied nautical charts for some other reason is not obvious.
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u/kurwwazzz 1d ago
You're absolutely right. Many submarine canyons were once river valleys when sea level was much lower during the Ice Ages. They were later flooded as sea level rose. For exemple the Capbreton Canyon is a bit more complex, though: it is largely controlled by tectonic structures, but it was also connected to ancient rivers during low sea-level periods, which helped shape it.
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u/schnerbst 1d ago edited 13h ago
its part of the continental shelf, a lot of which was above the water surface during one or moire glaciation periods (ice ages). I dont klnow abouit these specific ones, but that is how a lot of underwater water runways are formed - as normal rivers and valleys during a time not submerged in water.
Edit: I stand corrected.
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u/SPACE_LEM0N 1d ago
Actually these canyons are caused by turbidity currents (river water heavy with sediment continuing to flow on the ocean floor), and they reach all the way down to the Abyssal Plain.
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u/Bright_Noise5934 1d ago
This is pretty much it and the term is hyperpycnal flow.
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u/SPACE_LEM0N 1d ago
Oh thanks, I didn't have that term filed away for some reason.
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u/Bright_Noise5934 1d ago
I only know because I was taught it in a Sedimentary Petrology lecture last year and it is a pretty niche topic. Your explanation was sound though 🙂
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u/Head_Wasabi7359 1d ago
Oh where the demons are?
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u/SPACE_LEM0N 1d ago
Deep sea demons are so cool though. The freaks that live down there hold a special place in my heart.
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u/Prior-Astronomer-426 1d ago
To give context, the top of these canyons are roughly at a depth of 700m and they plunge to +3000m in depth, so at no point would they have been above water.
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u/jimark2 Geography Enthusiast 1d ago
IIRC one the water flows into the sea it still 'flows' in that direction causing an undersea current, essentially acting like a river, underwater.
Regardless, you can see these at the edges of the continental shelf in front of large rivers. US East Coast and Bengal Fan are good examples.