The Ecological Classification System, introduced on page 13, classified this biome on the basis of its bedrock, glacial deposits, topography, climate, and plant communities. It formed four subsections, or landscape areas, rich in its diversity of prairie communities. This flat glacial lake plain is subtly interrupted by wetlands, meandering streams, sand dunes, and old beach ridges. Bedrock is Precambrian in the east and sedimentary in the west, where exposures near Lake Traverse are rich in fossils. Glacial Lake Agassiz deposited silt, sand, and clay, with some saline patches.
Beach ridges are dry with sandy, gravelly soils.
The Red River flows north to the Hudson Bay, which is still frozen when Minnesota thaws, causing water to back up and flood the lake plain. Tallgrass prairie and wet prairie dominated presettlement vegetation. Today, with intensive ditching, most land use is agricultural. Fragments of native prairie can be found east of the beach ridges and in the interbeach zone. Conservation concerns include preservation of prairie, wetland, and wildlife habitat, along with control of wind erosion.