California, Yosemite National Park, Middle Cathedral Rock. On 14 May Eric Beck (21) and Tom Frost were ascending the direct north buttress (Chouinard roper route) of Middle Cathedral Rock. On the fifth pitch Beck led up 5th class for 25 feet placing one piton for protection. At this point, the crack narrowed and he began placing pitons for direct aid. All this time he had been climbing up the edge of a large flake or exfolliation slab. As the second direct aid piton was driven behind the slab, the crack expanded, loosening the piton he was standing in and causing the fall. The 5th class piton also pulled out and he fell 80 feet.

Source: Tom Frost.

Analysis: The party was climbing well and moving rapidly. Both members looked critically at the slab, but neither seriously considered that a feature of such massive size would actually expand. The accident could have been avoided by (1) realizing the expanding nature of the flake, or (2) using a slower, more conservative approach to the general problem of expanding flakes. This implies cutting into the higher piton before it is driven hard, or as could have been done here, utilizing a thin crack in the wall for placing alternate pitons.