Alaska's Sand Dunes

Ten thousand years ago, when the last major glaciation occurred (the Wisconsin glaciation), the Tanana Valley was glacier free. Still, it probably looked quite different than it does today. There were fewer trees and probably a lot more sand dunes.

As they ground the Alaska Range to the south into flour-sized particles, glaciers carried the debris northward and delivered it to the winds sweeping up the Tanana Valley. The winds, in turn, deposited the silt onto the hills fronting the valley--33-Mile Bluff, Moose Creek Bluff, Birch Hill, College Hill, Chena Ridge and the Nenana Bluffs.

Most of the time the silt deposited so fast that extensive humus layers did not build up. In places though, one can dig down to find thin dark layers, an inch or so thick, representing times of low wind deposition rates.

Active sand dunes probably moved across the lowland areas, just as they still do today west of Huslia in the Koyukuk Valley and along the Kobuk River. Low, hill-like remnants, now arrested by growths of small trees and shrubs, can be seen along the Parks Highway, just south of Nenana. There several persons have built their houses on the dunes as a means of getting up above the nearby surroundings.

Even today one sees the telltale signs of blowing soil, blowouts and elongated windrows of silt on top of the snow and moss. Perhaps we are very close to the condition when the plant growth can no longer arrest the dunes. Even a rather slight change--more wind or less rain--might cause the dunes to move again.

Agricultural development, too, could trigger the change. Replacement of the natural perennial growth by annual crops that do not hold the soil so well could have the potential for long-term disaster.