The images also reflect the complexity of the formation processes that made the current surface landscape. Most of the mounds have been formed as a result of the erosion and collapse of earthen structures. At the Khepter Khana (a substantial building within the citadel Shahriyar Ark), for example, excavation of the debris showed a complex sequence of erosion and collapse, interspersed with periods of relative stability (Fig. 21).
Figure 21: Excavated section through the erosion debris surrounding the Kepter Khana (a substantial medieval building within the citadel area of Shahriyar Ark). The section shows horizontal external deposits, overlain by sloping erosion and collapse sequences. (Scale 5 x 0.20m)
The observed mounds exhibit clear linear patterns, with distinct ridges, and the inference is that the mounds represent ancient wall lines, along with their erosion cones of collapse and decay. Where the erosion/decay/collapse has taken place within a building, what are left are distinct mounds along wall lines, but with a considerable amount of debris within the rooms themselves (e.g. resulting from collapsed ceilings/roofs, upper storeys). When the erosion/decay/collapse processes have taken place around an open space/courtyard, there was less material to fill the open space, so it remains markedly lower and, as a result, attracts more moisture and thus more vegetation or damper soil, both of which show as darker areas on the aerial images (Fig. 22). In addition, many of the open areas have an almost circular appearance, caused by the additional collapse/erosion material at wall junctions (twice as much material when compared to straight wall sections), coupled with the lack of material in the central portion of the open space (no ceiling or roof material and too far away from the erosion of wall lines) (Fig. 23).
Figure 22: A sample area of the vertical APs showing darker areas (courtyards/open spaces) and lighter areas (buildings). Note the almost circular shape of some of the courtyards, caused by the development of additional collapsed building debris towards the wall junctions (see Fig. 23).
Figure 23: Sketch of formation processes within a courtyard space: material accumulates close to the wall lines and thus more material develops in the angles of walls, leading to almost circular or oval erosion patterns within courtyard spaces. The picture is accentuated by the lack of upper storeys/roofs collapsing into the space, and the scale of the open space.
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Last updated: Mon Sept 29 2008