Geomorphology
gholam hassan jafari; Frozan Naseri
Abstract
Doline is one of the most characteristic and basic surface and morphological forms of karst, as a result of the chemical effect of water on limestone that occurs in different shapes and sizes. Dolines differ in morphological characteristics. In the present study, after identifying the valleys in the ...
Read More
Doline is one of the most characteristic and basic surface and morphological forms of karst, as a result of the chemical effect of water on limestone that occurs in different shapes and sizes. Dolines differ in morphological characteristics. In the present study, after identifying the valleys in the karst areas of the Zagros, their dispersion and change of morphological characteristics such as length, width, area and depth in relation to altitude and climate, citing documentary sources such as geological maps 1: 100000, digital elevation model layer with strength 12.5 m resolution, satellite imagery, 1: 50,000 topographic maps, and 49-year-old Esfzari temperature and precipitation databases were analyzed in Arc GIS, Mapper Global, and Excel software. The study of different parameters of Zagros valleys in different altitudes and climates indicates that their shape and depth have been affected by Quaternary climate change. At lower altitudes, where water is more involved in dissolution than low temperatures, the dolines are nearly circular in shape and stretch at higher altitudes and the lower the temperature and the greater the likelihood of the doline turning into a glacial-doline circus, the more elongated the doline becomes. The compression coefficient of the dolines also indicates that their elongation and length increase with increasing height; in this way, at an altitude distance of 500-1000 meters, the ratio of circles for every 1000m increase in height increases by 0.8 and the compression coefficient decreases by 0.9. At an altitude distance of 1000-2000m, with each increase of 100m, the ratio of circles is 0.44 and the compression coefficient is 0.1. In the 3700-3000m floor, the circular ratio decreases by 1.2 with each elevation of 1000m, and the compaction increases by 1.3.
Climatology
gholam hassan jafari; Hazhir Mohammadi
Volume 23, Issue 68 , September 2019, , Pages 47-69
Abstract
Changes in the base levels are the most important factors of forms and processes’ imbalance in drainage basins. Ghezel Ozan basin, which is the sub-basin of Caspian Sea, has had many effects on base level fluctuations. In this study, Channels and Lithology were evaluated using GIS software and ...
Read More
Changes in the base levels are the most important factors of forms and processes’ imbalance in drainage basins. Ghezel Ozan basin, which is the sub-basin of Caspian Sea, has had many effects on base level fluctuations. In this study, Channels and Lithology were evaluated using GIS software and topographic and geological maps. Using evidences, the base level changes including the capture and diversion of convergent radial rivers and channels of Bijar geo-neuron in Qezal Oazan Basin were identified. Also, the relationship between branch and length of the channels in Bijar sub-basins was investigated using the fractal geometry theory and Horton- Strahler stream ordering method and their fractal dimension was calculated. The results show that the effects of changes in local base levels of Bijar hole can be traced as aggregate levels in the alluvial plains of 6 sub-basins of Angouran-Chay, Hassanabad Yasukand, Yol-Kashti, Ghorveh and Dehgolan, Garmab and Sujasrud. The prospecting process is visible in the center of the hole. At elevations of 1561, 1540 and 1515 meters in Bijar hills, 3 lake terraces have been observed. The fractal number of 2.12 of Bijar basin indicates that the whole basin is in a relatively moderate condition and the retardation erosion in the branches is going to be stopped. In the two sub-basins of Yol-Keshti and Ghorveh-Dehgolan, fractal dimension of less than 2 shows that the coefficient of branching is greater than the basin area. At the head of the water at the Angoran Chay, Sujasrud and Garmab sub-basins, the branches are still developing and retreating. Hassanabad Yasukand sub-basin with the highest fractal number among the sub-basins (3.25) reaches its maximum balance and the lowest erosion is dominant in its branches. Investigating the relationship between fractal dimensions and branching ratio with the area of the studied basins indicates a reverse and negative relationship.
Geomorphology
gholam hassan jafari; Mahdei Abbasei
Volume 22, Issue 65 , November 2018, , Pages 117-139
Abstract
Review of river terraces is main issues related to river geomorphology. They are areas with low slope that is parallel to the axis of the river valley and are in the higher levels of the river bed and created through cutting the river bed and response to changes in external factors such as climate, tectonics ...
Read More
Review of river terraces is main issues related to river geomorphology. They are areas with low slope that is parallel to the axis of the river valley and are in the higher levels of the river bed and created through cutting the river bed and response to changes in external factors such as climate, tectonics and base level. Ghezel owzan River is as one of the longest river systems in the country, responded well to changes in external factors (climate, tectonics and base level). For this purpose, after dividing the river into nine periods, Profile was drawn on the terraces adjacent faults in order to study in terms of height level and symmetry. In order to assess the effect of Tectonic activity on Ghezel owzan Catchment area, Four sub-basin are studied: Divandareh, Zanjan rood, Gharanghochay and Hashtchin- Tarom, from Upstream to downstream , With the help of two indicators, River Gradient length (SL) and Valley floor width to valley height (Vf) by determined sections, The results indicate the relationship building terraces with tectonic factors. This means that form terraces in downstream river is more a reflection of the effects of neo-tectonics and tectonic if they originate, reflecting the effects of tectonics. Feedback such activities is in basin downstream for nested alluvial fans and vertical-walled terraces in bedrock and in the mirage nested terraces in alluvial sediments with low sides slope.
