Tilting With Nature

Just the fact that the Tanana River hugs the north side of its broad valley is a hint that something peculiar is going on. Add to that the observation that trees on the north side of the valley, in the Minto Flats show signs of drowning and one has the strong suggestion that the Tanana Valley is slowly tipping northward.

Additional suggestion that the whole valley, and even the Alaska Range to the south, is tipping northward comes from the strange paths followed by the Nenana and Delta Rivers. Rivers are supposed to head in the summit valleys of mountain ranges and not cut across the mountains as these two rivers do.

By rights, the summit near the head of the Delta River should be in the heart of the Alaska Range. Instead, it is well to the south, adjacent to Summit Lake. Hence the Delta River cuts right across the heart of the Alaska Range on its northward flow into the Tanana Valley.

Even more peculiar is the path of the Nenana River. It flows westerly along the south side of the Alaska Range and then abruptly turns northward to cross the high mountains.

The clincher to the idea that relative vertical motion is occurring is observation by geologists working in the Alaska Range that the range itself is uplifting. While the north side of the Tanana Valley may not be moving downward, the uplift on the south side does result in tipping of the region.

One of the consequences is the construction of a major dike near Fairbanks to hold the Tanana River away from the town. Unfortunately, the Chena River, which heads in the uplands to the north of the Tanana Valley, flows through Fairbanks to enter the Tanana River just below the city. With man's propensity at times to tilt with the forces of nature, one wonders how long it will be before funds are appropriated for a lift station to pump the Chena River waters up into the Tanana.