Tutorial:Burning residues

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Burning Residues
Fire has been used as a means of land management, waste disposal, heating, protection, cooking, and in numerous industrial processes. As a result charcoal, ash and other burning residues are some of the commonest indicators of past human activity.

Indicators of burning
Burning involves the liberation of heat and light energy from a fuel material; the by-products of this process include charcoal and partially carbonised fuel materials, ash, and heated stones, soil and artefacts. Where burning takes place directly on the soil surface the heat from the fire can also alter the structure of the soil resulting in the formation of a burning crust and spherical vesicular voids, the loss of soil organic matter, the breakdown of the soil structure and changes in colour associated with the loss of organic materials, and the oxidation of iron minerals in the soil.

More information on recognising indicators of burning in the field can be found here

Geoarchaeological analysis of burning residues
Examination of burning residues in the field can help to identify activity areas such as hearths and industrial areas but this requires that the residues of burning in-situ can be differentiated from redeposited burnt material as middens and rubbish filled pits also often contain high concentrations of burning residues.

More information about the field identification and interpretation of in-situ burning can be found here.

Analysis of redeposited burning residues, can also be useful with respects to specific archaeological questions. The incorporation of ash and hearth waste with manures in many traditional systems, means that burning residues can provide a marker for land use and management practices (Adderley et al., 2006).

Techniques often used to investigate burning residues include:
 * Magnetic susceptibility
 * Micromorphology
 * Microanalysis
 * Electron Spin Resonance