The Greater Yellowstone Ecosystem - Mountains and Plains: The Ecology of Wyoming Landscapes - page 255

the forests and substrate slipped about 1,000 feet,
with many trees coming to rest at an angle. only the
smaller trees survived, usually those less than 40 years
old—probably because many of them were flexible
enough and light enough to avoid significant breakage.
Seedlings of subalpine fir, limber pine, aspen, cotton-
wood, and other trees have since become established
among the surviving Douglas-fir, engelmann spruce,
lodgepole pine, and aspen. in contrast, the scar left by
the slide remains largely unvegetated.
Fears that the newly formed dam would break dis-
couraged tourism. indeed, 2 years later the upper 60
feet of the dam did fail, creating a flood of water, rock,
and mud that claimed the lives of six people. the
Fig. 15.11. the Gros Ventre landslide created Lower Slide Lake
when it dammed the Gros Ventre River on June 23, 1925. the
slide is more than a mile long and half a mile wide. the for-
ests are dominated by lodgepole pine at lower elevations and
have lodgepole pine, aspen, Douglas-fir, engelmann spruce,
and subalpine fir at higher elevations.
Fig. 15.10. east of the Snake River and north of Moran,
patches of mountain big sagebrush are found dispersed in a
shrubland of low sagebrush. Lodgepole pine and subalpine fir
dominate the adjacent forests on glacial moraines. elevation
6,600 feet.
east, the gravel conglomerates of the Mount Leidy
Highlands, the sedimentary strata of the Gros Ventre
Mountains to the east, and the granite and gneiss of
Jackson Peak to the southeast. All are much older than
the tetons. in the Gros Ventre Mountains, fine-textured
soils have developed that are highly susceptible to slip-
page when saturated. Landslides and mudflows are
common in this range. in fact, the largest slide in U.S.
history occurred there on June 23, 1925 (fig. 15.11). 36
Despite a dense cover of coniferous forest at the time, a
block of earth a mile long, half a mile wide, and up to
300 feet deep slipped down the mountainside, crossed
the Gros Ventre River, and created a dam 900 feet long
and more than 200 feet high. Lower Slide Lake was cre-
ated and now is about 3 miles long; ranch buildings
were inundated. All this occurred in about 2 minutes.