down to a considerable depth These curious conditions serve to 

 i<eep the two types of growth quite distinct, for the vegetation 

 of both is highly adapted to these particular seasonal alternations 

 of comparative heat and cold, and more especially to concurrent 

 changes in moisture and aridity, so that trees cannot get a hold 

 in the muskeg, while the muskeg bushes cannot grow in the 

 deep shade under the trees Thus, the whole of this land becomes 

 a vast jigsaw puzzle, as is plain when it is seen from the air and 

 IS only too patent when you try to cross it on the ground. 



As we mentioned in the previous chapter, there is compara- 

 tively (to the mean world average) low precipitation in these 

 northlands. That there is an excess of standing water on the 

 surface is due to the fact that the ground is permanently frozen, 

 which prevents water from sinking into the earth. These con- 

 ditions pertain throughout this province and almost to its south- 

 ern periphery. However, the frozen soil is not the result of the 

 high latitude or even of the long, very cold winters. It actually 

 results from what we may call "fossilized frozenness," some- 

 thing left over from the last southward advance of the north 

 polar ice — or "Ice Age" as it is popularly but misleadingly 

 called. 



THE LAST FREEZE-UP 



The whole northern part of the North American continent, from 

 the great barrier of the Rockies to Newfoundland, was recently, 

 by geological redconing, covered by an enormous icecap, esti- 

 mated to have been about two miles thidc at its maximum, and 



extending south to Montana in the west, St Louis m the center, 

 and Long Island, New York, in the east. This icecap seems to 

 have spread out from a point approximately in the middle of 

 Hudson Bay 



While there were countless vast glaciers on the Rockies, and 

 Quebec and Labrador were covered at the same time, neither 

 area went down beneath the load of ice. Parenthetically, it 

 should be explained that, while glaciers may in exceptional 

 circumstances coalesce to form "icefields." they do not form an 

 "icecap." Glaciers are moving rivers of ice that flow downward 

 from icefields; an icecap is something quite different and of quite 

 uncomparable dimensions: it is, in fact, a vast dome of ice 

 formed from compressed and recongealed snow that covers the 

 whole land, including mountain ranges and their icefields and 

 glaciers. Today there are but two in existence, on Greenland and 

 the Antarctic continent. Around the edge of icecaps there may. 

 of course, be glaciers. For this reason, while there are manifold 

 signs of recently past glaciation in the Rockies and in Labrador, 

 these are confined to the scouring of valleys and the creation of 

 certain peculiar phenomena in them. 



This mass of ice. piled up upon the whole northeastern part 

 of what is now the United States and Canada, weighed a tremen- 

 dous amount. At the same time, the surface rocks of the earth, 

 although appearing absolutely solid, are actually quite plastic 

 but they are only to a limited extent compressible, while the 

 next layer of material beneath them is not entirely rigid. If. 

 therefore, you pile enough extra weight on the surface it will 

 sag and. where the surface rocks are what is called "sedimen- 

 tary" — i.e. those formed under seas and lakes — they may also be 



A young bull moose browsing on pond plants in a mixed coniferous-deciduous forest. Largest of 

 the deer, moose, like all other species. >'■ - ^ ''• ■•■■ :•'' :•/ :"■ 





