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As shown by these figures, the landslide deposits aze up to 148 feet thick. The thickest part <br />occurs in the lower bench or northern part of the landslide mass where the deposits directly <br />1 overlie the 'B' seam. However, as shown in Figure 7, a lobe of landslide deposits extends <br />further upslope in the central part of the area. <br />In the upper or south part of the landslide mass, the base of sliding is not readily identifiable as <br />-I it does not correspond to the 'B' seam. Little or no colluvium was recognized on the logs of <br />borings penetrating this area. It is likely that most of the landslide debris that was present has <br />been removed by erosion over the centuries. <br />l ?~'alure of Landslide Materials <br />J Borings through the lower bench part of the landslide penetrated a heterogeneous range of <br />materials including sands, boulders, cla}'s and coal frzgmens. This material is interpreted as <br />landslide debris which has travelled a considerable distance from its source, with consequent <br />mixing of blocks of material from a range of strata. <br />Borings through the upper part of the landslide generally penetrated sedimentary bedrock from <br />neaz the surface. This material was not identified as being part of the landslide. Neaz the <br />surface, this rock mass may have beEn disturbed by minor downslope movements which would <br />not be evident from the drill cuttings. Cross-sections SN3, SN4, and SNS through the center <br />of the area show good correlations and consistent dips of strata between borings. This indicates <br />that there has been no major deep-seated sliding. <br />Current Instability <br />There is no evidence of current or recent instability on the lower, bench portion of the landslide. <br />In fact, the lack of any surface evidence of past movement indicates that this area has been stable <br />for a long period. <br />Scarps up to 12 feet high are present in the upper, steeper south part of the landslide mass as <br />shown on Figure 1. These scarps indicate recent movement. The lazgest of these scarps aze <br />' evident on both 1974 and 1992 aerial photographs. This indicates that sliding is occurring <br />slowly -probably less then one foot per yeaz of overall downslope movement. The fact that <br />sliding is still occurring is evidenced by fresh cracks, unvegetated scarps, and toppled vegetation <br />' associated with recent movement. Hummocky ground, which is indicative of recent but not <br />I ~ -10- <br />I 0: \Off\30\JPT\ARCO-Rpt.lkl <br />