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Grand Teton National Park
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In 1984, the SRC Chief Daniel Lenihan and NPS Research Scientist Gary Davis investigated several large trees that appeared to be rooted in an original growth position in Jenny Lake at Grand Teton NP. The trees were reported to the NPS by members of the Jackson Hole Dive Club at a depth ranging from 85-90 ft. Concern that the position and location of these trees evidenced severe contemporary seismic activity in the region was expressed at public hearings on the Jackson Lake Dam Environmental Impact Statement. The investigation was initiated to determine if the trees were actually rooted, indicating that they grew in-situ. If they did grow in-situ, then the substrate in which they were rooted may have been inundated by rapid tectonic activity, i.e. severe earthquakes. If, however, the trees came to rest in upright positions at the bottom of the lake as a result of avalanche, landslide, or wind-throw then no extraordinary tectonic forces are indicated.
During the course of the project, a total of 14 dives were conducted by NPS divers, which located 12 upright trees. Depth ranges from 15 to 80 ft were observed, however most were on a 55-60 ft contour at the toe of a submerged slope. In the course of underwater survey in a 20 to 60 ft vicinity of the upright trees, a total of 64 trees were encountered: 62 prone and 2 upright. Nearly all the branches on both upright and prone trees were broken off at the trunk. |
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| The underwater scene in Jenny Lake near the uptight tree looks similar to that on the adjacent shoreline. There was an accumulation of large trees scattered like jackstraws as the base of a slope. One out of thirty of the submerged trees came to rest in a vertical position. This distribution may occur simply by chance, but the weight of stones in root-balls of larger trees may cause them to sink in vertical positions. It was evident that the upright trees examined were not rooted in their original growth positions. It appeared they were deposited in the lake by avalanches from the steep slopes of Cascade Canyon.
- 1995 - John Brooks, SRC photographer, executed a series of dives with Diane Richardson (assigned to the SRC from Channel Islands National Park) to obtain underwater images for use in Underwater Wonders of the National Parks.
- 1984 - Lenihan and Gary Davis conduct assessment of downed trees in Jenny Lake at request of the park and the Bureau of Reclamation. They determined that trees were not rooted and did not occur upright underwater as a result of localized tectonic factors.
Reference:
- 1984 Trip Report on assessment of trees available from SRC through special written or e-mail request.
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Grand Teton National Park
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