Understanding conflagration of one-story mud-brick structures: an experimental approach

Many Near Eastern destruction layers are characterized by burnt, partially collapsed, mud-brick structures. Despite the prominence of these layers in archaeological field research, the processes that generated these layers are little understood. In order to explain field observations and identify patterns that may be useful for archaeological interpretation, experimental burning of miniature single-story mud-brick structures was conducted. Two types of structures—covered by vegetal roofs or by mud-plastered roofs—were conducted. Each experiment was duplicated. Temperatures in chambers, walls, roofs, and floors were recorded continuously. Bricks, floor, and roof sediments were sampled and analyzed by Fourier transform infrared (FTIR) spectroscopy after the burned structures cooled down. The results showed that ignition of vegetal roofs does not produce a pattern recognizable in Near Eastern destruction layers, while chamber ignition within mud-plastered roofed structures produces patterns that most resemble field evidence. These include (a) upper portions of walls and mud roofs witness temperatures above 500 °C resulting in a mineralogical change that is identifiable by FTIR, (b) no significant heat in floor deposits, (c) higher temperatures in upper parts than the bottom portions of walls, (d) external walls experience heat diffusion to the outside environment and do not burn through, and (e) internal walls can burn through. The directly measured temperatures correlate with reconstructed temperatures via FTIR and with brick color patterns. Future field research should explore color patterns in cross-sections of mud-brick walls and apply FTIR spectroscopy to reconstruct distribution of heat across destruction levels.