Browsing around Google Maps, I came across this off the south-west coast of Ireland

Continental shelf southwest of Ireland

It looks very consistent with the shape rivers and their tributaries might make, but it has me puzzled since it's all underwater!

The main, most "river-like" one is in the middle-left of the picture but there are more (which look more like fjords) at the bottom.

What caused this feature?

  • 7
    $\begingroup$ So you discovered the Gollum channel system, nice (it really is called so). Have an extensive read at wikipedia on submarine canyons, then return with further questions. $\endgroup$
    – Erik
    Mar 23, 2020 at 12:41

1 Answer 1


The carvings are submarine canyons, a part of the continental slope leading from the continental shelf to the continental rise and ultimately the Abyssal plains. They are a product of :

  • erosion through currents and
  • slumping of the continental shelf

Like other erosive or slumping effects, they can be self-reinforcing, leading to canyon-like structures. The highlighted canyon here is the Gollum Channel system, seen here.


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