DAŠT (plain, open ground) ,Persian term for a very specific type of landscape. In scientific geographical literature it is applied to the extended gravel piedmonts and plains that are almost ubiquitous in arid central Persia. Sloping down from the upper reaches of the mountains and highlands, dašt areas are built up by more or less coarse material like gravels of different sizes and composition (e.g., rocky hammada, pebbled serir). They cover broad expanses of surface and pile up in the interior of mountain ranges, seeming to drown them in their own debris. Geomorphological studies have shown, however, that degradation of the higher parts of the relief coincides with aggradation of its lower parts. Dašt slopes are therefore both erosional and depositional features (Figure 7). Such phenomena are called “pediments” and are differentiated into degradational and aggradational piedmonts (Weise, p. 451). The gravel deposits of the dašt generally form very thin covers of erosional material; one of the main features of dašt areas is their gentle slopes, no more than a few meters per thousand in their lower reaches, though as much as 50 m or more per thousand close to the mountain front. As a precise descriptive term, dašt must not be confused with kavīr (playa), which refers to surface coverings composed exclusively of very fine materials like clay, silt, and salts of various kinds. The much higher salinity of the kavīr leads to the formation of salt crusts, whereas the plains surrounding the dašt may develop gypsum crusts or none at all. Furthermore, although the almost total absence of flora and fauna in the kavīr convey the impression of an entirely sterile natural environment, dašt areas, even under extreme climatic conditions, are characterized by more or less regularly distributed forms of desert or semidesert vegetation and fauna (Bobek; de Misonne; Anderson; Read).
For details of Persian dašts and kavīrs, see DESERT.
Bibliography:
S. C. Anderson, “Zoogeographic Analysis of the Lizard Fauna of Iran,” in Camb. Hist. Iran I, pp. 305-71.
H. Bobek, “Vegetation,” in Camb. Hist. Iran I, pp. 280-93.
A. Gabriel, “Die Lut und ihre Wege,” Zeitschrift für Erdkunde 10, 1942, pp. 423-42.
S. Jervis Read, “Ornithology,” in Camb. Hist. Iran I, pp. 372-92.
X. de Misonne, “Mammals,” in Camb. Hist. Iran, I, pp. 294-304.
O. Weise, “µMorphodynamics and Morphogenesis of Pediments in the Deserts of Iran,” Geographical Journal 144, 1978, pp. 450-62.
(ECKART EHLERS)
Figure 7. Section showing the composition of dašt and adjacent kavīr. After Weise.
(Eckart Ehlers)
Originally Published: December 15, 1994
Last Updated: November 18, 2011
This article is available in print.
Vol. VII, Fasc. 1, pp. 94-95
