NORTH DAKOTA STATE UNIVERSITY
- FARGO, N D
in the contiguous United States.
While most geologic landscapes have their histories measured in millions or tens of millions of years, that of Fargo is measured in only a few thousands of years.
"The Red River Valley" therefore is an unfortunate misnomer for this landscape. It is not a valley in the sense that it was formed by a river. Instead, the origins of this flat plain lie as the floor of what was an enormous glacial lake.
The actual "valley" of the Red River is only a few hundred feet wide at Fargo. Because of the low gradient of the Red and the young age of the river, the "valley" is not fully mature. During times of major flood, the "valley" quickly fills, and floodwaters spill out onto the lake plain. Hence, major floods in the Red River Valley tend to be wide but shallow.
These expansive properties make it difficult to engineer and protect permanent structures in the Valley. Street surfaces, sidewalks, water lines, etc., rise and fall with the water content of the clays. Because the strength of these clays is generally low, heavier structures in Fargo must first have considerable foundation support, requiring piers (caissons) or pilings that pass entirely through the package of Lake Agassiz sediments to support the structure on firmer glacial materials beneath.
Rivers that flow northward are actually not particularly rare (there are many in the United States). But the Red River of the North is one of the few drainages in the contiguous 48-states whose waters ultimately drain into the Arctic Watershed. Waters of the Red flow northward into Lake Winnipeg in Manitoba. There, they mix with waters of the Saskatchewan River, whose headwaters lie in the Canadian Rockies. Lake Winnipeg, itself, is drained by the Nelson River, which flows northeastward into Hudson Bay at York Factory, Manitoba.
In perhaps a more romantic view of the Red River, its waters therefore mix with those draining glacial ice fields of such places as Banff National Park and Jasper National Park. These waters together drain northeastward, ultimately to be lapped by the tongues of polar bears or to serve as an area for beluga whales to dive and play.
Prior to the Pleistocene ice ages, a pre-glacial version of the Red River likewise flowed northward. It would have been a considerably larger river, having a watershed that included much of eastern North Dakota, northeastern and north-central South Dakota, and northwestern Minnesota. The landscape over which this river flowed would have been fantastic to see: the river itself flowing across granitic basement rock of the Canadian Shield. To the west would have been buttes and mesas of Cretaceous-aged shales and sandstones. Springs leaking from some of these sandstones would have been highly salty.
Much of that pre-glacial topography is still "there," but buried underneath several hundred feet of glacial drift and glacial lake sediments. The landscape therefore that we see around Fargo today is one whose origins are tied to the last events of the last ice age.
Donald P. Schwert