<p>It looks like a submarine canyon incised into the seafloor and shelf by repeated sediment &quot;flushing&quot;. Given the location, earthquakes probably flush huge quantities of sediments from the low angle plains to the north, through the canyons, and into the abyssal plain to the south. You might find these canyons in any tectonically active seafloor that sees heavy sediment loading from, say, a mountainous tropical region. This one's not that big, compared to <a href="https://advances.sciencemag.org/content/4/3/eaar3748?rss=1" rel="nofollow noreferrer">New Zealand's Hikurangi Channel</a>, at nearly 700 km.</p>
<p>There's another one off the <a href="https://www.google.com/maps/place/42%C2%B057%2717.6%22N+144%C2%B018%2753.3%22E/@42.6301358,144.4863875,93039m/data=!3m1!1e3!4m5!3m4!1s0x0:0x0!8m2!3d42.9548889!4d144.3148056" rel="nofollow noreferrer">SE coast of Hokkaido Island</a>. What, precisely, locally controls the formation of these canyons is an interesting question.</p>

CC BY-SA 4.0
2021-03-17T18:57:03.657Z
There are canyons like this on the passive margin along the US Atlantic coast, so I'm not sure a tectonic explanation is necessary.
Spencer
CC BY-SA 4.0
2021-03-18T19:48:19.037Z
True, but those canyons are likely drowned fluvial channels created by Pleistocene continental runoff. By contrast, Shionomisaki Canyon does not seem to have any surficial river associated with it.
Knob Scratcher
CC BY-SA 4.0
2021-03-18T22:05:07.043Z
There are three in the upper left of the image, coming down from the higher level of the continental shelf.  In the Atlantic, the abyssal plain has continuations just like Shionomisaki Canyon.
Spencer
CC BY-SA 4.0
2021-03-17T06:19:12.633Z
2021-03-17T07:57:49.480Z
2021-03-17T07:57:49.480Z
Knob Scratcher
<p>Visiting Google Maps, I came across this long, sinuous, while pretty regular mark undersea that looks like an ancient river, when the sea was way lower, or a big (big!) boulder that could have rolled down to the bottom (?).</p>
<p>Given the location (ring of fire), it could also be a &quot;crack&quot; made during a major (and ancient) earthquake that, with time, has been filled with sediments.</p>
<p>This looks like <a href="https://earthscience.stackexchange.com/questions/5189/undersea-riverbeds">this question</a>, but the shape is very different, and much less sinuous than the one in Japan.</p>
<p>The mark:</p>
<p><a href="https://i.sstatic.net/c7eFp.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/c7eFp.jpg" alt="enter image description here" /></a></p>
<p>The location:</p>
<p><a href="https://i.sstatic.net/pscvf.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/pscvf.jpg" alt="enter image description here" /></a></p>

CC BY-SA 4.0
2021-03-15T13:52:50.933Z
That's the Shionomisaki Canyon. It flows to the east / southeast before turning south to cut across five ridges.
David Hammen
<geology><earthquakes><satellite-oddities><sea-floor>
What is this long mark undersea
Déjà vu
# What is this long mark undersea

(Asked by: username_0 on 2021-03-15)

Visiting Google Maps, I came across this long, sinuous, while pretty regular mark undersea that looks like an ancient river, when the sea was way lower, or a big (big!) boulder that could have rolled down to the bottom (?).

Given the location (ring of fire), it could also be a "crack" made during a major (and ancient) earthquake that, with time, has been filled with sediments.

This looks like [this question](https://earthscience.stackexchange.com/questions/5189/undersea-riverbeds), but the shape is very different, and much less sinuous than the one in Japan.

The mark:

[![enter image description here](https://i.sstatic.net/c7eFp.jpg)](https://i.sstatic.net/c7eFp.jpg)

The location:

[![enter image description here](https://i.sstatic.net/pscvf.jpg)](https://i.sstatic.net/pscvf.jpg)

**Tags:** geology, earthquakes, satellite-oddities, sea-floor

> **Comments:**
> **username_1**: That's the Shionomisaki Canyon. It flows to the east / southeast before turning south to cut across five ridges.  

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## 1 answers

### Answer by username_2 on 2021-03-17. Score: 3

It looks like a submarine canyon incised into the seafloor and shelf by repeated sediment "flushing". Given the location, earthquakes probably flush huge quantities of sediments from the low angle plains to the north, through the canyons, and into the abyssal plain to the south. You might find these canyons in any tectonically active seafloor that sees heavy sediment loading from, say, a mountainous tropical region. This one's not that big, compared to [New Zealand's Hikurangi Channel](https://advances.sciencemag.org/content/4/3/eaar3748?rss=1), at nearly 700 km.

There's another one off the [SE coast of Hokkaido Island](https://www.google.com/maps/place/42%C2%B057%2717.6%22N+144%C2%B018%2753.3%22E/@42.6301358,144.4863875,93039m/data=!3m1!1e3!4m5!3m4!1s0x0:0x0!8m2!3d42.9548889!4d144.3148056). What, precisely, locally controls the formation of these canyons is an interesting question.

> **Comments:**
> **username_3**: There are canyons like this on the passive margin along the US Atlantic coast, so I'm not sure a tectonic explanation is necessary.  
> **username_2**: True, but those canyons are likely drowned fluvial channels created by Pleistocene continental runoff. By contrast, Shionomisaki Canyon does not seem to have any surficial river associated with it.  
> **username_3**: There are three in the upper left of the image, coming down from the higher level of the continental shelf.  In the Atlantic, the abyssal plain has continuations just like Shionomisaki Canyon.  

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