Forest physiography; physiography of the United States and principles of soils in relation to forestry . discord-ances that prevail throughout its entire area between general surfaceand geologic structure — a discordance that can be explained only bythe assumption that it was once a region of prolonged erosion and thata pronounced, possibly a mountainous relief, was reduced practically tothe level of the sea. 558 FOREST PHYSIOGRAPHY REPRESENTATIVE DISTRICTS LAURENTIDE MOUNTAINS With these general features in mind we may now turn to the moredetailed features of representative portions of the La
Forest physiography; physiography of the United States and principles of soils in relation to forestry . discord-ances that prevail throughout its entire area between general surfaceand geologic structure — a discordance that can be explained only bythe assumption that it was once a region of prolonged erosion and thata pronounced, possibly a mountainous relief, was reduced practically tothe level of the sea. 558 FOREST PHYSIOGRAPHY REPRESENTATIVE DISTRICTS LAURENTIDE MOUNTAINS With these general features in mind we may now turn to the moredetailed features of representative portions of the Laurentian area,beginning with the Laurentide Mountains that border the St. LawrenceValley on the northwest. Perhaps the most important point in thisdistrict is that relating to the deformation which the Laurentian pene-plain suffered in the uplifting process that raised it to its presentlevel. The uplift was differential and is still in progress; the generalnature of the first uplift was a tilting of the whole northeastern cornerof the continent upward at the north; the present movement is in har-. Fig. 224. — The Laurentide Mountains north of St. Lawrence River at St. Anne de Beaupre. The lowlandin the foreground is formed on limestone which terminates at the foot of the mountain slope. mony with and in continuation of the earlier movement. The Lauren-tide Mountains are due only in small part to their residual are due chiefly to the greater uplift of the peneplain along theborder of the St. Lawrence Valley, so that its southeastern margin asviewed from the valley does not appear as the margin of a plateau butas a range of hills of sufficient height to be known as marginal swell roughly parallel to the margin of the peneplain issucceeded toward the interior by a number of circular depressions oc-cupied by lakes, of which the St. John at the head of the SaguenayRiver is the most important. The streams of this portion of theplateau cross the margina
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectforestsandforestry
