On April 16, 2011, cohan fulford wrote: > >..... (a very fast google suggests 10 feet deep as a frost line > for Alberta, other sources suggest 4-6 feet, haven't found anything > official--suffice to say, lots more than 6 inches here :)
I'm no expert on frost lines, Cohan, but I do know that the official frost lines in Canada have more to do with the depth footings need to be, or road beds need to be and so on, than with the actual depth to which soil freezes in a typical winter. Here in Ontario, footings have to be deeper than (I think) 4 feet, but the ground never freezes that deep. Even in a very cold winter (-30C) with no snow cover, the ground only freezes about 1 foot down. If the extreme cold lasts longer, than it freezes deeper. In practice, however, we almost always have good snow cover, and most winters the soil doesn't freeze at all. Tundra happens when the temps stay low enough long enough that the frost never completely leaves the ground, thus causing the next winter to add to the existing frozen soil. If you think of a block of ice, say one cubic foot, surrounded by air or warmish soil, it takes a certain amount of cold to freeze it solid. If you take the same cubic foot of water and put it on top of a solid block of ice, it will be easier (quicker) to freeze. Tundra soil never completely thaws out, only the top thaws, and so the frost line will be very deep indeed. Lis Lis -- Lis Allison Pine Ridge Studio www.garden-on-the-ridge.blogspot.com _______________________________________________ Alpine-l mailing list [email protected] http://mailman.science.uu.nl/mailman/listinfo/alpine-l
