Spalling occurs when extreme temperatures weaken the surface of concrete, masonry, or brick, causing it to chip, pit, and scar. This phenomenon is primarily caused by rapid expansion (if heated) or contraction (if cooled) of the surface of the concrete compared to the different rate of expansion of the underlying layers of the material. Spalling can be recognized by distinct striated lines on the surface, with chips, craters and broken pieces. Color changes can also be observed: light areas where the top layer of material has burned away, exposing a clean underlying area, and dark areas of soot deposits. Although spalling can be associated with the presence of an ignitable liquid, spalling is NOT an "automatic" indicator that an accelerant was used in the fire. Spalling can be caused by other factors, including water rapidly cooling hot concrete. Like all other indicators, spalling must be considered with the totality of the evidence at a scene before a cause determination can be made.