Withrow Moraine and Jameson Lake Drumlin Field erosion resulting from the Missoula Floods, which laid bare many layers of the basalt flows on the edges of the plateau at Grand Coulee and Moses Coulee. Two million years ago the Pleistocene epoch began and Ice age glaciers invaded the area. They scoured the Columbia River Plateau, reaching as far south as the middle of the Waterville Plateau highlands above the Grand Coulee and south to the head of Moses Coulee. In some areas north of the Grand Coulee they were as much as 3 km (10000 feet) thick. Grooves in the exposed granite bedrock are still visible in
Birch Coulee Battlefield edge is a steep wooded ravine, a landform known locally by the French term "coulee," also spelled "coulie" or "cooley." Birch Coulee, known to the Dakota as "Tanpa Yukan" (Place of the White Birch), is deep and runs for a total of down to the Minnesota River. A few hundred yards to the west of the coulee, the prairie rises slightly onto a gentle knoll. On September 1, 1862, a burial detail of about 170 Union Army volunteers and civilians under Major Joseph R. Brown camped on the prairie west of Birch Coulee. The site was selected by Captain Hiram