THE RELATIONSHIP BETWEEN GEOLOGY AND CLIMBING ACCIDENTS IN THE “GUNKS”: LITHOLOGY, GELIFRACTION, STRESS AND ROCK FATIGUE

The Shawangunk Ridge in the mid-Hudson Valley, New York, has long been a favorite site of technical climbers because of the ease of access, rock quality (quartz pebble conglomerate to quartzite), and variety of climbing routes. We have analyzed data from 1972 provided by the Mohonk Preserve that includes: injury type, climbing location, route taken, and date of accident. Since the placement of fixed gear such as bolts or pitons is discouraged, climbers must be knowledgeable about the geology and what gear selection will be needed for the abundant horizontal bedding surfaces, vertical joints and fault planes oriented at various attitudes. Chocks or cramming units placed into horizontal sandy beds that are extremely friable present a hazard, whereas gear placed into joints or faults are much less likely to slip unless the rock is flaked or otherwise stressed. Two contributing factors that weaken the rock, often without external signs, are gelifraction and fatigue. Gelifraction refers to the breakup of rocks due to tremendous pressure exerted by the freezing of water that has seeped into cracks or pores or along bedding surfaces. Failure of the rock may occur after many repetitions of a stress resulting in accumulated strain that weakens the climbing face, resulting in rock fatigue. Climbers repeatedly using the same climbing routes subject the rocks to low-level stress which, by constant repetitive use, can cause failure. Preliminary analysis of climbing accidents in the “Gunks” indicates that in many cases the gear failed, resulting in falls. This occurred mainly for two reasons: (1) gear was placed improperly or, (2) the rock chipped. Accidents may have occurred less often in quartzite rather than conglomerate. In the cases we studied, accidents in the Trapps and the Near Trapps were caused by protection that pulled out of the rock wall resulting in injuries ranging from abrasions to fractures and a fatality (Shockley’s Ceiling). The incidence of injury does not appear to correlate with technical difficulty. For example, Shockley’s Ceiling is rated 5.6 on a scale of 5.2-5.13d on the Yosemite Decimal System and is not considered particularly challenging.