Good examples of overwash or outwash plains may be seen at various points in the vicinity of Baraboo. The plain west of the moraine just south of the main quartzite ridge has been referred to under valley trains. In Sauk Prairie, however, its characteristics are those of an outwash plain, rather than those of a valley train.

Fig. 41. -- The morainic or outwash plain bordering the terminal moraine. The figure is diagrammatic, but represents, in cross section, the normal relation as seen south of the quartzite range at the east edge of Sauk Prairie, north of the Baraboo river and at some points between the South range and the Baraboo.

A good example of an outwash plain occurs southwest of Baraboo, flanking the moraine on the west (Fig. [41]). Seen from the west, the moraine just north of the south quartzite range stands up as a conspicuous ridge twenty to forty feet above the morainic plain which abuts against it. Traced northward, the edge of the outwash plain, as it abuts against the moraine, becomes higher, and in Section 4, Township 11 N., Range 6 E., the moraine edge of the plain reaches the crest of the moraine (Fig. [42]). From this point north to the Baraboo river the moraine scarcely rises above the edge of the outwash beyond.

Fig. 42. -- The outwash plain is built up to the crest of the moraine. The figure is diagrammatic, but this relation is seen at the point marked W, Plate [II].

North of the Baraboo river the moraine is again distinct and the overwash plain to the west well developed much of the way from the Baraboo to Kilbourn City. A portion of it is known as Webster's Prairie.

Locally, the outwash plains of this region have been much dissected by erosion since their deposition, and are now affected by many small valleys. In composition these plains are nearly everywhere gravel and sand, the coarser material being nearer the moraine. The loose material is in places covered by a layer of loam several feet deep, which greatly improves the character of the soil. This is especially true of Sauk Prairie, one of the richest agricultural tracts in the state.

When the waters issuing from the edge of the ice were sluggish, whether they were in valleys or not, the materials which they carried and deposited were fine instead of coarse, giving rise to deposits of silt, or clay, instead of sand or gravel.

At many points near the edge of the ice during its maximum stage of advance, there probably issued small quantities of water not in the form of well-defined streams, bearing small quantities of detritus. These small quantities of water, with their correspondingly small loads, were unable to develop considerable plains of stratified drift, but produced small patches instead. Such patches have received no special designation.