"The spalling-enhanced- drilling model developed by Krantz, Camp and Gunn has been shown to predict quite well the water- influx data for the Hanna UCG field tests. In addition, Levie, Krantz, Camp, Gunn and Youngberg have used this model to predict the cavity shape for the Hanna II Phase II UCG field test which agrees well with the shape determined by post-burn coring studies. Furthermore, Gunn and Glaser have used the spalling-enhanced-drying model to show that the heat absorbed by the spalled rock accounts for the ten per cent heat losses in the Hanna III field test which heretofore could not be explained. This paper presents cavity-shape predictions for the recently cored Hanna III UCG field test which provide additional confirmation of the validity of the spalling-enhanced-drying model. In addition, this paper discusses the mechanisms responsible for spalling."