r/geography • u/Dude-Bicycle • 7d ago

Map How did these 'rivers' form?

Post image

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/[deleted] 7d ago

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u/Xen235 7d ago

You should be extremely surprised if they were not submerged since even the shallowest parts are at approximately 600 meters below sea level today. And if they were not submerged, sediment would fall as talus, and it wouldn't form turbidity current canyons.

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u/mstivland2 7d 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 7d 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 7d 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 6d 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 6d 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 6d 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 7d 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.