Northern Prairie Wildlife Research Center
|48b. Sand Deltas and Beach Ridges||Level IV Ecoregion|
|Home||Glacial Lake Agassiz was the
last in a series of proglacial lakes to fill the Red River Valley
since the beginning of the Pleistocene. The Lake agassiz Plain is composed
of thick lacustrine sediments underlain by glacial till. It is extrememly
flat and has fewer lakes and pothole wetlands than neighboring ecoregions.
The historic tallgrass prairie has been replaced by intensive agriculture.
The preferred crops in the northern half of the region are potatoes,
beans and wheat; soybeans and corn predominate in the south. Sugar beets
are grown throughout the region.
The varying relief of the Sand Deltas and Beach Ridges ecoregion interrupts the extremely flat and intensively farmed land of the Lake Agassiz Plain (48). The beach ridges appear as parallel lines of sand and gravel formed by wave action on the varying shoreline levels of glacial Lake Agassiz. Three sand deltas, the largest being the Sheyenne River delta in the south, occur where major rivers entered glacial Lake Agassiz and dropped their sediment load. A high erosion risk exists in the sand dune areas.
Area (square miles): 1616
Surficial Material and Bedrock
Order (Great Groups)
Precipitation - Mean annual (inches)
Potential Natural Vegetation
Tallgrass prairie with patches of oak savannah in delta areas.
Land Use and Land Cover
Sunflowers, potatoes, small grains on beach ridges. Mainly grazing on delta sands. Corn on sandy loams. Some irrigation.