north were then high, but this cannot he said to he proved. That the arctic lands have been at some time raised higher than now, is shown by the fiords of the northern coasts, which, as first pointed out by Dana, must have been excavated by subaërial erosion; but a large part of that erosion may have been effected in the Tertiary age, and perhaps it was chiefly accomplished then.
When a dense forest clothed the arctic lands, and spread over continuous land-surfaces to Europe and Asia, these now half-submerged fiords were valleys traversed by flowing streams; for the abundant Tertiary vegetation of the far north proves the country to have been well watered. That these fiords were filled with glaciers during the Ice period is certain, as the bottoms and sides of many of them are glaciated, but this would happen again with a depression of temperature, and without a depression of sea-level. The fact that the glaciated surface of the bottoms of fiords in Sweden and America passes under the sea, and reaches as far as observation can be carried, is not the proof of elevation it has been claimed to be, for the glaciers that now reach the sea must score their beds to the depth of several hundred feet, before their extremities are lifted up by the one-tenth greater gravity of water, and are floated off as icebergs.[1]
Prof. J. W. Dawson holds the view that the Glacial period was one of depression at the north, as he finds marine shells in the bowlder clay of the St. Lawrence Valley; and he attributes much of the glaciation of Eastern North America to icebergs dragged over the submerged land.
Croll says ("Climate and Time," p. 391):
"The greater elevation of the land (in the Ice period) is simply assumed as an hypothesis to account for the cold. The facts of geology, however, are fast establishing the opposite conclusion, viz., that when the country was covered with ice, the land stood in relation to the sea at a lower level than at present, and that the continental periods or times, when the land stood in relation to the sea at a higher level than now, were the warm inter-glacial periods, when the country was free of snow and ice, and a mild and equable condition of climate prevailed. This is the conclusion toward which we are being led by the more recent revelations of surface-geology, and also by certain facts connected with the geographical distribution of plants and animals during the Glacial epoch."
According to the investigations of Bohtlingk and Kjerulf, Scandinavia was 600 feet lower during the Glacial period than now. Erdmann, on the contrary, supposes that Sweden was higher during the Glacial epoch than at the present day, from the fact that polished
- ↑ Some of the huge tabular icebergs, which have been observed off the Antarctic Continent, projected more than 500 feet above the surface of the ocean; and as for every foot above water there must have been 8.7 feet submerged, the whole thickness of the ice-sheet, from which these bergs were detached, must have been over 5,000 feet, and such a glacier must grind the sea-bottom to a depth of over 4,000 feet. (See Croll, "Climate and Time," p. 385.)
