Ice Edge and flooded marsh, is it possible?

[Yon]

Hi everyone,

hope this is the right section. I have a technical question about realistic climatic possibilities: I draw a very long edge that divides the North's Lands from the rest of the Continent. North's Lands are always icy but the Edge works as a climatic borderline: onward the Edge, southwards, there is a big big marsh, like a sea that have got a few centimetres of depth; northwards, over the Edge, the perpetual ice.
Ice melts and runs down the Edge, fueling this marsh-sea for a kilometres and kilometres.

I would like know if it's a realistic scenario or not.


Thank you and sorry for my very poor English.

[Pixie]

Realistically, that Ice Edge you describe is a glacier, pure and simple. If the temperature and the rain pattern of a location is stable, then so will the glacier limit. Glaciers limits, however aren't normally a marsh. You will have a moraine, maybe a small lake, a river. The sort of marsh you describe demands a very flat land, but glaciers won't develop in flat land, not that I know.

The closest I can think to what you describe is right at your door step. Lake Como, Lake Garda and the likes are the remainders of glaciers that flowed down the Alps. For a long period of time, the walls of those glaciers must have been nearly as high as the mountains that embraced them and to their south... plains. Yet, the glaciers are in the middle of mountains.

[Azélor]

Maybe, I'm thinking that a marsh is pretty much the same thing as a shallow lake. The lower area is a natural depression with a (semi) permafrost soil. The soil cannot absorb the water since it's often frozen due to low temperatures. Thus, the water accumulates in small pockets here and there.

[Kanny]

Geologically speaking this would, in my mind, have to involve some kind of transitional gradient between the two states (unless magic or a potent technology of some form is involved).

Assuming your northern reach is an ice covered mass it would have to transition into a more glacial formation that then breaks (over some distance) into your marshland. There would as a result be quite some degree of flooding between the two states as well, probably forming into quite a broad and potent river as a result.

Additionally When your talking about this kind of mass of water, it would likely have a current that would over time have eroded many of the small mounds you may consider when picturing a marsh. Also bare in mind that plant life would emerge on this terrain very slowly, which would in turn prevent this "would be marsh" from benefiting from any of the natural purchase (roots) or resistance (various types of floral and faunal debris) that that would gum up the flow of water - thereby preventing the aforementioned current and resulting erosion.

Also when considering the slow formation of life we must also remember that soil (a key component) would not simply spring up from nowhere. Soil its carried (by water or wind) and deposited as the result of other life in a cycle. This is why bare rock normally comes before or around large frozen expanses.

As a result you have a situation where one element prevents the other from ever occurring. Its two cold for life, thus no soil, thus bare rock in the face of lots of water, thus small rocks are eroded and thus we have a large body of water with a few jagged formations of rock OR canals cutting between larger rocks (probably mountains) which may eventually give way to your marsh over a wider plateauing distance.

The best real world example of this kind of transition I can think of is the terrain between north Canada and Greenland. Notice the various channels that wind and more importantly water erosion have born into these terrains over millions of years.

I'm no expert so I may be wrong on one or more of these things but this is my own impression of the realities in play here.

Also I should say that none of the above take into consideration any kind of seasonal change. Your region could indeed be a large area of marshland or swamp that at certain times freezes as a result of low temperatures. This is not an unheard of circumstance in many points around the world. I think however that this is not really the kind of thing your talking about here though.

Anyway hope that helps!

[Yon]

Many thanks guys, you're very helpful!
Shallow lake is also a great scenario like to the marsh that I have imagined.
Naturally this area cover many km2, therefore a gradual transition is possible.
If I finish the map i will post it here for any comment.