
Undersea rivers we know little about - happy-go-lucky
http://www.bbc.com/future/story/20170706-the-mystery-of-the-massive-deep-sea-rivers
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dsmithatx
I immediately thought of Devil's Kettle Falls reading this. I had to Google it
and found that 4 months ago scientist have decided it flows back into itself.
They have a plan to put a large amount of dye in during low water and see
where it reconnects.

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jfries
Ah the circular river. Very rare but useful to extract energy from.

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bousaid
Have people done this?

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marcosdumay
I'm quite certain the GP was a joke.

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pmontra
Only badly worded. The missing water flows back into the visible river
somewhere downstream, not upstream.

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b_emery
We know lots about these things - as the article explains. A lab I'm roughly
associated with models them, here's an example:
[https://www.youtube.com/watch?v=UR5NoaqpCok](https://www.youtube.com/watch?v=UR5NoaqpCok)

The physics (IIRC) are very similar to snow avalanches. I saw a talk once that
presented evidence of one in the Indian Ocean flowed half way to the Antarctic
(order 1000s of km). They have been observed to scour the canyons (such as
Monterey Canyon) and are hypothesized to be set up similarly to avalanches,
where the sediment depositions become unstable and slide.

A final bit of trivia: the photo of the mooring base shows a common
oceanographic mooring construction material - used railroad car wheels. Big,
super heavy and relatively cheap. I've never heard of them being recovered.
Usually the important parts are detached and the wheels are left behind.

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cjensen
I was curious about the canyon after looking at geo maps a couple of years
ago. When I looked at Wikipedia at that time, it described the canyon as an
ancient feature created by a long-ago river.

Is this stuff undergoing a revolution in understanding? Or was Wikipedia just
very out of date? Revolutions in understandings are always fun!

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b_emery
The canyon is certainly an 'ancient' feature - just the underwater extension
of geographic features on land. The river (on land) at the base of the canyon
carries sediments into the ocean. These get deposited somewhat haphazardly,
and occasionally destabilize forming the turbidity current. That is the extent
of my understanding.

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phkahler
My first thought was that these formed during glaciation when most of the
continental shelf was exposed. The rivers just had to flow further to get to
the sea. My second thought is that my first thought is still valid after
reading the entire article. It is interesting that they have mud flows in
those areas, but I doubt that has much to do with how they formed.

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cossatot
Sea level during the Pleistocene glaciation got to be ~150 m lower than today.
You are absolutely right that during times of low sea level, the rivers eroded
this part of the shelf just as today. However, these canyons go all the way
down the continental slope to ~3000 m below current sea level, with the same
basic erosional forms (check out Monterey Canyon in Google Earth, it's
gorgeous). These mud flows (called turbidites in the literature) are quite
capable of eroding the seafloor when they flow down steep slopes, though at
rates well below what rivers do on the surface.

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rmason
Detroit at one time had seven rivers, but they were buried. In Detroit they're
known as ghost waters.

[http://www.huffingtonpost.com/2013/04/02/detroits-ghost-
wate...](http://www.huffingtonpost.com/2013/04/02/detroits-ghost-waters-
video_n_2999011.html)

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fowkswe
Hudson Canyon always fascinated me:
[https://en.wikipedia.org/wiki/Hudson_Canyon](https://en.wikipedia.org/wiki/Hudson_Canyon)

