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There are earthquakes on the Canadian shield, and the reasoning is that it is due to Earth deformation recovery. Essentially, the ice age's massive glaciers de

by b112 2y ago

There are earthquakes on the Canadian shield, and the reasoning is that it is due to Earth deformation recovery. Essentially, the ice age's massive glaciers deformed the ground, and it is slowly rebounding over 1000s of years. The result is minor tremors, sometimes larger quakes. I am in southern Quebec, and there is a LOT of water here. Personally, I suspect there are glaciers underground which are still thawing, which would also cause additional land movement. Some supporting thoughts... * one year, after a lot of snow (record snowfall, where some people's 1st story windows were covered entirely), it took until July for all the snow to melt. This was in areas around my house, and in my forest, where sun didn't shine. * if you look into how we used to store ice for the summer, we'd cut it out of lakes in massive blocks (eg, Lake Ontario or some such), and then store it in warehouses covered with sawdust. Such ice was even used residentially, delivered every once in a while, and used in a refrigerator like 'ice box'. This ice would last the whole summer, it takes time for that much mass to melt, especially with some insulation. Which is what underground glaciers have... they're insulated. Even a decade ago, we'd see -40C regularly here in Jan and Feb, which would counter 40C in the summer I suspect. Anyhow, this could all be simple post-ice age land reformation.

mjhay 2y ago
There's not underground glaciers. Glaciers are always on the surface, and flow due to gravity. You're thinking of permafrost (which can form wedges and lenses of pure ice). Deeper permafrost responds slowly, but on the flip side of that, there never would have been deep permafrost in S. Quebec during the last glacial maximum. The permafrost situation also wouldn't affect isostatic rebound much, because the amount of water in the ground wouldn't change appreciably. A rule of thumb is that only the first two meters of ground responds appreciably to annual variability, which also means that only the very near surface temperatures have the possibility of affecting snowmelt. Thus, any remaining deep permafrost would have almost no effect. It's too much of an insulating overcoat to allow for meaningful heat flux on those timescales.

by b112 2y ago

mjhay 2y ago

There's not underground glaciers. Glaciers are always on the surface, and flow due to gravity. You're thinking of permafrost (which can form wedges and lenses of pure ice). Deeper permafrost responds slowly, but on the flip side of that, there never would have been deep permafrost in S. Quebec during the last glacial maximum. The permafrost situation also wouldn't affect isostatic rebound much, because the amount of water in the ground wouldn't change appreciably. A rule of thumb is that only the first two meters of ground responds appreciably to annual variability, which also means that only the very near surface temperatures have the possibility of affecting snowmelt. Thus, any remaining deep permafrost would have almost no effect. It's too much of an insulating overcoat to allow for meaningful heat flux on those timescales.