Why did Greenland's Ice Canyon form?

[fredinno]

https://en.wikipedia.org/wiki/Greenland's_Grand_Canyon

I'm wondering how such a thing could form- before the ice sheets came in. It really is strange...

[Kryten]

Why would it require some fundamentally different mechanism to any other canyon? The length is just a factor of the shape and relief of Greenland.

[mikegarrison]

Many major canyons are actually rifts, caused by continental spreading. https://en.wikipedia.org/wiki/Rift_valley

Edited August 1, 2017 by mikegarrison

[magnemoe]

Fast guess Greenland was squeezed on the sides generating the bottom and east mountains, then center get pushed down by the ice.
 

[YNM]

It might be a failed rift. Interesting to note that apparently Greenland and Canadian northern islands (what do you call it ?) has a bit of depression in it as well - it might be somewhere along the time that Pangaea rifted apart (and the Atlantic forms). Why do I raise this ? Well, if Greenland really is an extension of North American continent, the sea inbetween should've been shallower, like what you get inbetween Papua and Australia. Also, such large-scale rifting of continents should cause a lot of failed ones as well, like what you get near Sinai peninsula, or the current East African Rift (hasn't failed), or the one that separated Madagascar from Africa. Greenland might have been a similar story for a few times.

[DerekL1963]

3 hours ago, mikegarrison said:

Many major canyons are actually rifts, caused by continental spreading. https://en.wikipedia.org/wiki/Rift_valley

 

1 hour ago, YNM said:

Well, if Greenland really is an extension of North American continent,

Greenland sits on top of an independent plate.

[mikegarrison]

12 minutes ago, DerekL1963 said:

 

Greenland sits on top of an independent plate.

According to Wikipedia, there are questions about that. https://en.wikipedia.org/wiki/Greenland_Plate

[insert_name]

according to Wikipedia it was caused by water erosion

[YNM]

1 hour ago, DerekL1963 said:

Greenland sits on top of an independent plate.

 

1 hour ago, mikegarrison said:

According to Wikipedia, there are questions about that. https://en.wikipedia.org/wiki/Greenland_Plate

It needs not to be an independent continent. An aulacogen is enough.

Although, considering that so far we take Greenland to be a craton, maybe... we should dig in ?

53 minutes ago, insert_name said:

according to Wikipedia it was caused by water erosion

How long would it have been for that to be true ? It doesn't say that it's because of water - it only says that if it was from erosion, it's probably water and not glacier (ice).

[razark]

Time + Water -> Some godsdamn amazing things

 

Water flows downhill, and it carries debris with it.  The faster it flows, the more debris it will carry.  The greater the gradient, the greater the flow.  Initiate feedback loop.

The geology of Greenland was right enough to channel any water runoff into a certain area.  Over time, flowing water and tiny bits of debris eroded that area down.  Since it was lower, water tended to flow into that area.  More water flowed into that area, carrying more debris, which eroded more of a channel which allowed more water to flow into that area, carrying more debris, et cetera ad nauseam and you've got a river valley turned into a canyon.

Edited August 1, 2017 by razark
Bourbon

[Green Baron]

Guys stop flinging wikipedia articles at each other, they seemingly add questions, not answers :-)

First, the canyon is "preliminary". It is covered with kms of ice and thus beyond probing.

Second, there is no strangeness.

 

The ice shield over Greenland built up in the last 10-20 million years in phases. The canyon is probably an erosional structure forming by subglacial meltwater under the pressure of the ice sheet.

See: http://science.sciencemag.org/content/341/6149/997#aff-1

Maybe there is younger work on this, idk.

:-)

Edit: ice shield dynamics are a young field in geoscience. Imagine that - besides the constant flow of the masses from the center outwards - ice constantly melts by pressure and temperature and builds up anew on top through precipitation. Thus there is constant throughput. Though the ice shield (better: cap) as a whole is several million years old, the base ice is "only" a few hundred thousand years old.

Enough throughput for a proper erosion.

And a fast melting if we carry on being so careless ;-)

Edited August 1, 2017 by Green Baron