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Memo to Houlay Jumbo Mountain Landsliding page 3 the United States Geological Survey. Among his numerous publications, Dr. Dunrud authored several USGS monographs addressing subsidence mechanics in Somerset, Colorado and the Book Cliffs areas. Following our inspection, MCC forwarded a copy of Dr. Dunrud's DRAFT report for my examination (see attached). In addressing the landslide at Muffler Rock, Rich Dunrud concludes; "Though the slide this spring at Muffler Rock was roughly coincident with the movement of the Panel 9 longwall face beneath it, it is unlikely that the mining influenced the slide movement significantly. The Mesaverde sandstone and overlying surficial material moved northward during the slide; the Panel 9 longwall face moved eastward. The tilt, curvature, and strain produced by longwall mining (and attendant subsidence) would be maximum in the east-west direction and minimum (or perhaps zero) in the north-south direction. Therefore, I believe that the predominant cause of the slide at Muffler Rock this spring (1997) was the saturated conditions of the material and the northward dip of the bedrock (about 5 degrees) towards the currently existing Muffler Rock landslide scarp." Reexamination of the .71~mbo Mountain north slope Landslide Complex - 1996 Deposits During spring of 1996, approximately 30 to 50 acres of the SW1/4 of Section 24 was affected by landsliding. Mr. Mautz reports that minor cracking was noted by his ranch hands on the roads within the affected area in the fall of 1995, followed by extensive landsliding in May / June of 1996. This is in keeping with my observations of annual spring/summer landsliding in the North Fork Valley over the past nineteen years. Cracks and graben-like (steep-sided trapezoidal) extensional troughs up to ten feet wide and five feet deep were examined in several locations towards the middle to lower portions of the landslide deposit. The more common features are cracks 3 to 12 inches in width. Cracks can be traced for lengths in excess of 100 feet. Most cracks evidence translational offsets indicative of downslope and lateral movements. Cracks occur along contour, parallel to the fall line, and at random orientation. No discrete conclusions could be made about the actual depth of the basal failure plane of the landslide mass(es). The features I observed are typical of large landslide masses in the Williams Fork formation of the Mesaverde Group. These landslides occur prolifically throughout the North Fork Valley on slopes of varying gradient and aspect. The largest and most notorious active landslide in the area is the Muddy Creek Landslide, east of Paonia Reservoir.