The eastern elevation is a ridge or cuesta formed by an outcropping hard layer of the ancient coastal plain; and it separates the Wisconsin river basin from the Fox River Valley and the streams flowing into Lake Michigan.
The vast river basin thus enclosed embraces 432,480 sq.
By far the largest Asiatic river basin is that of the Ob, which exceeds 1,000,000 sq.
The climate is generally dry, although less so on the mountains and in the Flathead river basin than on the Great Plains, and is subject to sudden changes and to great extremes of temperature; but the temperature varies more than the amount of precipitation.
The area of the river basin is calculated at 895,500 sq.