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<br />- 32 - <br /> <br />The scarps and elongate depression features have the appearance of 1andn <br /> <br />slide scarps and tension features associated with landslide displace- <br /> <br />ments. We believe the talus is actually a mantle over numerous UnGeT- <br /> <br />lying landslide surfaces. Figures 18 and 19 illustrate the genera:l <br /> <br />appearance of the linear depression features. <br /> <br />According to our geologic interpretation, it seems probable that <br /> <br />a talus of coarse rock debris formed on the glacially oversteepened <br /> <br />north side of the Crystal River valley in this area. Influenced by the <br /> <br />steep angle of repose of the coarse rock debris, and perhaps aided by <br /> <br />I <br />seasonal presence of intersticial ice, the talus assumed more rapid <br /> <br />movement similar to a rock glacier. In addition to the movements within <br /> <br />the mass, we believe that slow landslide movements have taken place at <br /> <br />the contact between the talus and the steep glaciated surface upon which <br /> <br />it was deposited, or along south-dipping bedding surfaces of the under- <br /> <br />lying rock. The probability of such sliding occurring is increased oy <br /> <br />several conditions, including (1) a very steep original slope caus0J <br /> <br />by previous glaciation; (2) abundant water on the surface from underly- <br /> <br />ing morainal material and sub cropping Mesa Verde sandstone beds; and, <br /> <br />(3) south-dippingand erosionally detached bodies of intrusive igneous <br /> <br />rocks on the upper slope. We believe that the above described combina- <br /> <br />tion of movement within the mass of rock debris, concurrent with basal <br /> <br />slippage and 1ands1iding has produced the observed topographic forms - <br /> <br />the sinuous transverse ridges by movement within the talus, and the <br /> <br />elongate depressions and linear scarps as a result of tension and down- <br /> <br />slope displacements of portions of the talus. Field observations sug- <br /> <br />gest that these movements are rather slow, but continuing (figure 19). <br /> <br />,We consider the entire slope in this area to be unstable and em- <br />