تحليل مورفومتري و مورفولوژي شبكه زهكشي در مخروط آتشفشاني تفتان

Morphometric-morphologic Analysis of Drainage Systems in Taftan Volcanic Cone

Volcanic cone of Taftan is located in southeast of Iran ,northwest of Khash city. While there is water vapor and sulfur dioxide exhaustion from its peak, the presence of deep vail eyes and irregular shape of drainage system demonstrates long term erosion and complicated development of drainage system. For the evaluation of lithology, slope degree and slope aspect effects on drainage density, after digitizing of topographic and geologic map, we prepared Digital Elevation Model(DEM), slope degree, slope aspect, drainage system and lithology maps of Taftan cone in ILWIS software. Then drainage densitis in all formations, slope aspects and slope degrees was extracted .Data analysis reveals that, except alluvial fans and terraces, drainage density is more in old formations and steeper slope than in modern formations and lower slopes. Drainage density is more in east, southeast aspect, which are corresponding to older formations, than other aspects. Investigation of drainage pattern in study area shows that drainage pattern in younger lavas is parallel while in older lavas is dendritic. Nevertheless, there are irregularities in patterns. The comparison of old and new alluvial fans in IRS satellite images illustrates considerable differences in drainage patterns so that drainage patterns in new and old fans are divergent and convergent downward respectively. This is due to agradational process in new fans and degradation process in old ones. It can be, to some extent, accepted the viewpoint of some researchers like Parker about drainage density and pattern relation with time passing and slope angle in study area but there are complexities in drainage characteristics especially in channel pattern.