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Fig. 15.2. (left) Petrified tree trunks on a ridge south of the
Lamar River valley, the remnants of forests buried by volcanic
deposits in what is now Yellowstone national Park during
eocene eruptions, about 50 million years ago. the fossil trees
in the region include specimens of chestnut, magnolia, maple,
oak, redwood, sycamore, and walnut—none of which grow in
the area now. At the present time, Douglas-fir is common on
this steep north-facing slope. elevation 8,400 feet.
Fig. 15.3. (below) the tetons rise abruptly above the Snake
River and Jackson Hole to a maximum elevation on Grand
teton of 13,770 feet. Shrublands dominated by mountain
big sagebrush are characteristic of the flat glacial outwash
plains, at an elevation of 6,600 feet, including the lower
terrace carved during the Pleistocene epoch. Blue spruce,
engelmann spruce, narrowleaf cottonwood, river birch, silver
buffaloberry, and various willows are common in the riparian
woodlands. Douglas-fir occurs on the slopes above the river.
See also fig. 2.6.
 
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