Kansas Geological Survey, Current Research in Earth Sciences, Bulletin 244, part 3
The Relationship Between Geology and Landslide Hazards of Atchison, Kansas, and Vicinity--Fig. 14

Fig. 14. Diagram of the failure plane of a landslide in the Kanwaka Shale. The clay layer above the Clay Creek Limestone Member is weak, and the failure plane of the landslide would be located within this layer. Earth slides and earth flows on gentle slopes (5 degrees to 15 degrees) may be the result of thin, weak clay layers.