Samples were removed from five cores which had been drilled at the Hanna IV A and Hanna IV B burn sites. Strata in four of the cores included paralava and/or coke or semicoke. The fifth core contained coal which had been visibly altered, but there was no other thermally metamorphosed rock. All samples were analyzed by four techniques, including white light and blue light maceral analyses, vitrinite reflectivity, and fluorescence spectroscopy. All methods of analysis confirmed the presence of distinct vertical thermal gradients in Cores 1, 2, 12, and 14. A lateral thermal gradient between Cores 2 and 8 was also deduced. White light maceral analyses and fluorescence spectroscopy provided qualitative evidence that sharp thermal gradients existed between altered and unaltered strata beneath burn cavities and that much broader gradients existed above the burn zones. No absolute range of temperatures could be postulated, though. Blue light maceral analyses and vitrinite reflectivity provided much core quantitative evidence for the levels of thermal alteration. Heat transfer to rocks lying below the zone of combustion in a UCG chamber is apparently negligible. Much greater heat penetration and thermal alteration occurs laterally and vertically above the zone of combustion. 19 refs., 22 figs., 2 tabs.