SOIL SURVEY OF LOUISA C30UNTY, IOWA. 7 



farther south. On the west side of tho phiin the bluffs are 40 to 90 

 feet in height and the slopes are longer and rnore gentle. In sees. 

 4, 5, 23, 24, and 25, T. 75 N., R. 4 W., and in sees. 9, 10, and 15, 

 T. 74 N., R. 3 W., the margin of the upland is 10 to 30 feet higher 

 than the surrounding upland and has an uneven dunelike appear- 

 ance. These elevations are probably the result of wind action. In 

 the northeast half of Grandview Township there are several broad, 

 swell-like elevations lying about 30 feet higher than the surrounding 

 upland and having a northwest-southeast trend, while in Jefferson 

 Township several wide, shallow valleys with a northeast-southwest 

 trend occur. 



The western drift plain occupies the southwestern part of the 

 county. It is terminated on its eastern border by a well-defined 

 bluff extending along the Iowa River in its entire southeastward 

 course thi-ough the county. The elevation of the bluff above the 

 lowland varies from 125 feet north of Columbus Junction to less 

 than 75 feet along the west side of the Wapello Prairie. The bluff 

 line is broken by numerous streams leaving the upland and traversing 

 the bottoms. This plain, like the east plain, varies from level to 

 broken in topography, but is predominantly gently rolling to rolling. 

 An undulating to gently rolling surface characterizes the more recently 

 dissected parts of the plain, while a steeply rolling to broken surface 

 is general in the parts more completely dissected, as along the lower 

 courses of the streams. In Marshall Township and to the northwest 

 the creek valleys are wider, and have longer slopes that merge more 

 gradually into the upland plain than in Morning Sun Township and 

 southeast, where the valleys are narrower and V-shaped, with steeper 

 slopes that normally break sharply from the upland plain. As is 

 almost always the case in this latitude, where the streams run east 

 and west, the south slopes of the valleys are more steep and blufi'like 

 than the north slopes. A noticeable feature of the western upland 

 is a depression resembling a shallow drainage valley beginning at the 

 eastern border just north of Columbus Junction, extending southwest 

 about 3 miles, thence south to the southeast corner of Elm Grove 

 Township and thence south into Henry County.- This depression 

 has an average width of 1^ iniles, and where best defined its bottom 

 lies about 40 feet below the surrounding upland. Where it crosses 

 Long Creek the banks are very indistinct. A smaller branch de- 

 pression, about one-fourth to one-half miU; in width, leaves the main 

 depression at the northeast corner of Elm Grove Township and ex- 

 tends southw^est and out of the county at the southw^est corner of 

 the same township. These valleylike depressions are not drainage 

 valleys at present, but are crossed in places by small streams. It 



2 See Geology of Louisa County, by J. A. Uddeu, Iowa Geol. Survey Vol. XI, 19 :!0, pp. (53, 04. 



