Post 24897
Created:
Modified:
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.
Many of these meadows are as level as the surface of a lake. Commonly the surface is comparatively smooth, even though one edge may be higher than the other. I measured one meadow that was three thousand feet long by two hundred and fifty feet wide. Tree-ranks of the surrounding forest crowded to its very edge. On the north the country extended away only a foot or two higher than meadow-level. On the south a mountain rose steeply, and this surface of the meadow was four feet higher than the one opposite. The up-the-mountain end was about three feet higher than the end which had been the old outlet of the lake. The steep south shore had sent down more material than the level one on the north. In fact, water-level on the north shore, though concealed by grass, was almost precisely the same as when the waters of the lake shone from shore to shore. In one corner of the meadow was an aspen grove. From the mountain-side above, a landslide had come down. Rains had eroded this area to bed-rock and had torn out a gully that was several feet wide on the slope below. This washed material was spread out in a delta-like deposit on the surface of the meadow. Aspens took possession of this delta.
Glacier meadows are usually longer-lived than other mountain parks. In favorable places they sometimes endure for centuries. Commonly they are slowly replaced by the extending forest. The peaty, turfy growth which covers them is of fine matted roots, almost free of earthy or mineral matter, and often is a saturated mattress several feet in thickness. The water-level is usually at the surface, but during an extremely dry time it may sink several inches or even a few feet. If fires run during a dry period of this kind, the fire will burn to water-level. The ashes of this fire, together with the mineral matter which it concentrates, commonly form a soil-bed which promptly produces trees. Sometimes, however, grass returns. Thus, while fire brings forth many meadows in the forest, it sometimes is the end of one evolved from glacial action. A landslip often plunges a peninsula of soil out upon a glacial meadow. This is usually captured by trees in a year or two.