Post 01887
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But, though only one tree may grow, this in due time shades the grass, a circle of young trees rise around it, and these in turn carry forward the work of winning territory. At last the park is overgrown with trees!
Glacier meadows may be seen in all stages of evolution. The lake-basin gouged by a glacier goes through many changes before it is covered by a forest and forgotten. No sooner does ice vanish and a glacier lake appear than its filling-in is commenced. Landslips and snow-slides thrust boulders and cliff-fragments into it; running water is constantly depositing sand and sediment upon its bottom. Sedge and moss commence covering its surface as soon as its water becomes shallow. In due time it becomes a bog with a thick covering like a wet mattress, composed of the matted roots of sedge and grass. Over this, wind and water deposit earthy matter, but centuries may pass before the bog is filled in sufficiently to have a dry surface and produce grass and flowers and finally trees.
Once while strolling through a forested flat in central Colorado, I concluded from the topography of the country that it must formerly have been a glacier lake. I procured tools and sank a shaft into the earth between the spruces. At a depth of two feet was a gravelly soil-deposit, and beneath this a matting of willow roots and sedge roots and stalks. These rested in a kind of turf at water-level, beneath which were boulders, while under these was bed-rock. Numerous romantic changes time had made here.