CHAPTER XXVIII
GEOLOGICAL FORCES AT WORK
It seems to me that never before have I seen the geological forces of nature so obviously at work. Elsewhere I have seen great valleys, cliffs, islands, etc., held on good evidence to be the results of such and such powers formerly very active; but here on the Athabaska I saw daily evidence of these powers in full blast, ripping, tearing reconstructing, while we looked on.
All the way down the river we saw the process of undermining the bank, tearing down the trees to whirl them again on distant northern shores, thus widening the river channel until too wide for its normal flood, which in time, drops into a deeper restricted channel, in the wide summer waste of gravel and sand.
Ten thousand landslides take place every spring, contributing their tons of mud to the millions that the river is deporting to the broad catch basins called the Athabaska and Great Slave Lakes.
Many a tree has happened to stand on the very crack that is the upmost limit of the slide and has in consequence been ripped in two.
Many an island is wiped out and many a one made in these annual floods. Again and again we saw the evidence of some island, continued long enough to raise a spruce forest, suddenly receive a 6-foot contribution from its erratic mother; so the trees were buried to the arm-pits. Many times I saw where some frightful jam of ice had planed off all the trees; then a deep overwhelming layer of mud had buried the stumps and grown in time a new spruce forest. Now the mighty erratic river was tearing all this work away again, exposing all its history.
In the delta of the Slave, near Fort Resolution, we saw the plan of delta work. Millions of tons of mud poured into the deep translucent lake have filled it for miles, so that it is scarcely deep enough to float a canoe; thousands of huge trees, stolen from the upper forest, are here stranded as wing-dams that check the current and hold more mud. Rushes grow on this and catch more mud. Then the willows bind it more, and the sawing down of the outlet into the Mackenzie results in all this mud being left dry land.
This is the process that has made all the lowlands at the mouth of Great Slave and Athabaska Rivers. And the lines of tree trunks to-day, preparing for the next constructive annexation of the lake, are so regular that one's first thought is that this is the work of man. But these are things that my sketches and photographs will show better than words.
When later we got onto the treeless Barrens or Tundra, the process was equally evident, though at this time dormant, and the chief agent was not running water, but the giant Jack Frost.