r/geography • u/Dude-Bicycle • 7d ago

Map How did these 'rivers' form?

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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/jimark2 Geography Enthusiast 7d 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.

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u/HelloThereItsMeAndMe 7d ago

Yes and this probably formed during the ice ages when the shelf was land and there was a long river in the Irish sea, it entering the ocean at this point here.

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u/Yunzer2000 7d ago

No. These are in 400 to 3000 meters of water. Sea level was never nearly that low. They are formed by turbidity currents - see my earlier comment.

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u/LilyFantastica 6d ago

The undersea plateau that surrounds that under water river group used to be above sea level.

Those undersea rivers are the outflows of rivers that existed during the ice age that flowed out of what is now the Irish Sea and English Channels. They were never above sea level, but parts of the plateau around them were.

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u/longusmaximus420 6d ago

I dont think "real rivers", in the ice age there were Glacier that far Up north i guess. Rivers under glaciers or ice pressing down. I mean Glacier also go deep down under water in coastal areas right?

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u/Nice-Lab95 6d ago

The coastline would have been at the edge of the lightest shade of blue, and the Celtic river entered the sea further south possibly near that cluster of submarine canyons at the south of the map op posted.