242 
IOWA ACADEMY OF SCIENCE 
moderately steep, but rounded, indicating sub-mature dissection; the 
region is covered with loess which is frequently seen in road cut ex- 
posures; the surface material, derived from the loess, is without grit 
of ^ny sort; and no pebbles or boulders occur on the surface. In the 
more dissected parts, near the large valleys, the fresh, brownish-grey 
phase of the Kansan drift can be exposed. The region belongs to the 
loess-covered Kansan drift-plain. 
Running in an east-west direction through sections 30 and 29 south- 
west of East Sioux Falls is a ridge. It rises to an elevation which is 
approximately that of the major divides to the north, has a rounded 
crest and is apparently erosional. The north slope has broad valleys 
leading clown to the creek of sections 19 and 20, the bed of which is 
100 feet lower than the crest of the ridge. This is the ridgel described 
by Professor Todd and interpreted by him as a part of the outer 
moraine. From the crest of this ridge one overlooks the region to the 
north and the south. To the north is the rolling country of erosional 
topography noted above. To the south of the crest, the slope de- 
scends 30 to 50 feet in the first half mile and then an even plain of 
slight relief continues off to the south and southwest. 
Passing out onto this plain, in sections 31 and 32 (T. 101 N., R. 48 W.) 
it is found to have a relief of 15 to 25 feet with frequent undrained 
depressions, which during the wet seasons, are occupied by swamps or 
small ponds. Just east of the southwest corner of section 32, is a 
small depression occupied by a pond, not more than 50 yards from the 
edge of a narrow valley cut sharply to a depth of 30 to 40 feet be- 
low the plain. Other ponds occur just to the east in similar positions 
with reference to this valley, and at the quarter section corner on the 
east of section 32 is an undrained depression within a short distance 
of the edge of the Big Sioux valley. This plain continues southward 
and southwestward to Shindlar and beyond. North of Shindlar the 
relief is 10 to 20 feet and undrained depressions with swamps occur 
in every section. The location of a few typical ones may be noted, as 
in the southeast corner of section 36, the southwest and southeast quar- 
ters of section 31, the northwest corner of section 9, the east part 
of section 8, and at several places in sections 17, 8 and 7 along the 
Chicago, Rock Island and Pacific Railway northwest of Shindlar (Fig. 
3 ). 
The loess loam, so usual in the Kansan area, is 'absent here and the 
drift continues to the surface, or is overlaid by a black soil. A field 
in the southeast quarter of section 31, showed a gravelly, pebbly soil 
turned up by recent plowing and the road beds contain pebbles and 
