Assume you live in an environment where the possibility of the ice melting is not a concern (for example, the temperature rarely exceeds, say, -1 C). Speaking strictly in terms of the weight of the ice, the pressure it exerts on both the ground and itself, and any other considerations I may be overlooking, would it be possible for a mile-thick wall (at the base, and tapering toward the top) of ice to be built and to remain standing for centuries?
it would still need to be refreshed like a glacier due to sublimation of the ice.
You would basically be creating a somewhat small artificial glacier. Such a thing could be created but I believe it would have the same issues that other glaciers have. It would move and deform over time so I don’t think it would remain as originally built for centuries. You will also have evaporation issues even if it remains frozen all the time because water will still go straight from ice to water vapor.
The idea is similar to a Piedmont Glacier. They deform into a rough bulb shape over time.
If the OP is referring to a certain wildly popular book & HBO series ahem then The Wall is described as having internal man-made structures, such as gates and watchtowers.
Would that interfere with glacial movement?
Ice that is thicker than about 50 m undergoes plastic deformation, and slowly flows downhill.
So no, a large ice structure will not retain its shape.
There’s gotta be a temperature point past which ice doesn’t undergo plastic deformation.
Not to steal the OP’s question, but given the above, I propose a couple of additions:
A man-made internal structure constructed of wood and stone with gates and a wall. All this (with the exception of the gates) would be encased in ice .
Maintenance of the ice. For instance, carving back the ice at the bottom and adding snow and ice to the top periodically.
If there is, it’s pretty damned cold. Based on the phase diagram, it looks like the only transitions at standard pressure are one at about -200 C and maybe another at -100 C. You don’t get any other forms until over a thousand times standard pressure.
What if the wall were built over an ancient source of magic?
Ok, so the wall is going to move and change shape but does this happen slowly enough that the wall could reasonably be maintained and still effectively block off the far north?
The ice focusing sunlight like a laser might be a serious concern.
Doubt it. Glaciers carve out major geological features as they move. A chunk of ice that big is not going to be stymied by a couple of rocks and some concrete.
It wouldn’t focus the light significantly at all unless it were very specifically shaped to do so, and even if it did, it wouldn’t be anything at all like a laser.
How tall would this hypothetical ice wall be? You said 1m thick at the base and 700 feet long, but not how tall.
I’m sorry, it’s 700 feet tall, and several hundred miles long.
Ah, OK. And I see I missed the 1 mile thick at the base not 1m(eter).
Real-world buildings with reflective surfaces have been known to focus sunlight enough to damage cars without being designed to do so. While you won’t get a “laser”, you probably could get a significant focusing of the light if the ice is smooth & reflective enough.
The wall is explicitly said to be magical in origin, details left blank.
Is a sand castle going to interfere with the tide? When a glacier moves, nothing’s going to stand in its way.
This is a bit strong - mountains significantly constrain the paths that glaciers follow. But it’s true that glaciers carve their adjacent mountains, and at a considerable rate.