The case hardening also creates outstanding surfaces for climbing, so on sunny weekends, the state park draws hundreds of rock climbers of all abilities. Along with the enhanced weathering and erosion along fractures, this case-hardening results in an endless variety interesting shapes and pinnacles. At Smith Rock, the responsible minerals are mostly zeolites, a group of minerals with wide-ranging compositions but containing silica, aluminum, and water. The durable crusts form because minerals in the tuff dissolve in pore water and re-precipitate on the surface as the pore water evaporates. The outer edges of these features typically consist of more durable rock whereas the insides typically consist of softer, more easily erodible material. Numerous pocket-like holes dot many of the cliff faces.
Fine-scale layering in the Smith Rock Tuff
