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' <br />' <br />~ S <br /> <br /> It is very difficult to interpret the character and the <br /> depth of the landslide deposits.~°GIe believe that two types of <br /> landslides can be classified on the site: <br />' 1 <br />L <br />ld l <br />lid <br />d <br />h <br />d <br />l <br />i <br /> . <br />arge, o <br />s <br />an <br />es t <br />at occure <br />a <br />ong t <br />me ago, <br /> possibly during the Pleistocene time under different climatic <br /> conditions. These landslides included not only surficial soils <br /> but also the bedrock. Flat benches and generally hummocky topo- <br /> graphy of the area are a result of this type of sliding. <br /> ~ Slides could easily develop in geological conditions where <br /> 1 a water-bearing coal seam was underlain by an impervious layer <br />' I of shale or claystone; long-term exposure of the shale layer to <br />h <br />i <br />d <br />if <br />d <br />i <br />f <br />h <br />h <br />l <br />h <br />d <br />i t <br />e water cause <br />s <br />gn <br />icant re <br />uct <br />on o <br />t <br />e s <br />a <br />e strengt <br />an <br /> shearing resistance. As a result of potential high ground water <br /> pressures, a slide could easily develop; the slip plane of the <br /> failure follows the contact between the coal and shale and then <br />l iin a step-wise mode vertical joints and bedding planes in rock <br />- ` !above the coal seam. <br />' <br />i ~ <br />hi <br />lid <br />f <br />f <br />l <br />h <br /> es o <br />t <br />s type are <br />air <br />y common; t <br />ey can be observed <br />i S <br /> !in the Mesaverde formation in the vicinity of the Mount Gunnison <br />' ~ jmine; some of them are very recent. They are not always related <br /> jto the presence of the coal seam; a water bearing sandstone <br />' <br />I M ayer has a very similar effect on the stability. <br />, <br /> <br />' 1 2. Smaller, surficial slides that have been occurring <br /> (recently. These slides. are limited to the surficial solid cover <br />' only. Above five of <br />h <br />lid <br />di <br />l them are indicated on the geotechnical map; <br />b <br />b <br />i <br />i <br />h <br />l <br /> t <br />e s <br />e <br />y <br />rect a <br />ove <br />or <br />ng P1 <br />s t <br />e <br />argest one and, at <br /> the same time, the most recent one as it has developed during <br />' the last months. <br />~~ <br />' The development of these slides is closely related to the <br /> general instability of the area after the initial development of <br /> large landslides of <br />I the first group; unfavorable hydrological <br /> <br /> ao«.o.o cormu..n r.c <br />