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44 commonly, they are weathered rapidly by freeze-thaw action (Schumm I--" Wand Chorley, 1966). <.0 CiC Conditions and events associated with a wet climate are pictured in Fig'ure 5.8b. In Figure 5.8a. the cliff scarp and the underlying steep shale slope represents oversteepened yet relatively stable con- ditions during the dry climate. However, the increased amounts of moisture associated with a wetter climate would quick)y render the scarp unstable. Based on landslide studies in general (Varnes, 1978), instability could be due t.o some combination of increased seepage pressures of percolating water in the shale, solution by water from increased rainfall and snowmelt along the joints of the sandstone cap rock and in the bedding planes of the shale, and increased over steep- ening of the shale slope by accelerated erosion. In order' for the escarpment to regain equilibrium, one or more massive rockslides would occur. The water content and momentum associated with the slide would cause the large volumes of slide material to move down the already established piedmont drainages in the form of debris flows. Figure 5.9 shows the debris flow nature of a pediment surface north of Fruita, Colorado. Sometimes during, or shortly after, the debris flow events, the gravel layers were cemented with calc~te that was derived from the shale and sandstone on the debris flows (Carter, 1980). Because the sandstone is of low mechanical strength and because boulders up to 4 m in diameter are in the gravel deposits. fluvial process~s could not have been a major factor and the boulders would have to have been buried rapidly. Debris flows occurring in relatively rapid