نوع مقاله : مقاله پژوهشی
1 دانشجوی دکتری ژئومورفولوژی، دانشکده علوم جغرافیایی و برنامهریزی، دانشگاه اصفهان.
2 دانشیار گروه جغرافیای طبیعی، دانشکده علوم جغرافیایی و برنامهریزی، دانشگاه اصفهان.
عنوان مقاله [English]
Glaciers provide researchers as important sources for obtaining environmental information, water resources, agriculture, as well as climate change trends in the past, present and future.In the study of glacial circuses, allometric and morphometric study of circuses helps to identify the nature and how the processes affect during different periods on these glacial landforms.
By measuring the dimensions and geometric shape of these landforms with mathematical and statistical methods, a lot of information about environmental and climatic conditions can be extracted from them.
In this study, the morphometric and allometric indices of circuses in the heights of Silveh Basin in northwestern Iran on the border of Iran and Iraq have been identified, classified and analyzed using geomatic models and new methods invented by Seif (2014). For this purpose, digital DEM altitude map (10 meters) (received from Aster satellite), topographic map sheets of 1 / 50,000 Piranshahr and Sardasht, geological maps of 100,000 Naqdeh and Sardasht and Google Earth satellite images were used. Arc GIS 10.5, Global Mapper18, Google earth, Surfer11, Minitab16, Excel software have been used to produce composite maps and extract the required data and information. After determining the study area and cutting it using the DEM map, the layers needed to identify and analyze the morphometric and allometric parameters of glacial circuses were prepared and produced To identify and classify the glacial circuses of the region, the methods of Rudberg-Wilburg and Evans-Cox have been used. For morphometry and allometry of circuses in this area, indices such as (W), (L), (H), (W / H), (L / H), (L / W), and the size of circuses have been used. . Based on the research results, 33 glacial circuses were identified in the heights of Siloheh basin, of which 2 circuses are in N2 category, 11 circuses are in N3 category, 15 circuses are in N4 category and 5 circuses are in N5 category. Allometric study of basin circuses shows that the coefficient b for the longitudinal axis of circuits N3, N2 is equal to 0.88 and for circuses N4, N5 is 0.90 which is B <1. As a result, the allometric behavior of the circuses in this area is negative and in general, the circuses studied in this area have a lower degree of development and Quaternary glaciers have had a poor performance in this basin.
From the glacial circus formed in the heights of Silohe Basin, according to the Wilburg and Rudberg classifications, 2 circuses are equivalent to 6.06% of the total circuses in category N2, 11 circuses are equivalent to 33.33% of the total circuses in category N3 and 15 circuses, equivalent to 45.45% of all circuses, are in N4 category. Also, 5 circuses equal to 15.15% of all circuses are in N5 category. According to Evans and Cox classification, there are 2 circuses in the good and developed category, 11 circuses in the definite category, 15 circuses in the weak category and 5 circuses in the border category in the study area.
The average amplitude of the coefficient b changes for the longitudinal axis of circuses N2 and N3 is higher, ie these circuses move more towards evolution and development. In N2 and N3 circuses, the coefficient b for the longitudinal axis of the circuses is equal to 0.90. This value is equal to 0.90 for N4 and N5 circuses. In circuses of both categories is B <1. This indicates that the allometric behavior is negative for the longitudinal axis of the circuses of both categories. Also, the coefficient a is 0.92 for the transverse axis of N4 and N5 circuses and 0.70 for N2 and N3 circuses. Also, there is no isometric situation for circuses of both categories. Therefore, in general, the activity of glaciers during their rule and now has not had much impact on the development and evolution of circuses in these altitudes, and circuses in these altitudes need a long time to grow and develop. Glaciation in these roughnesses acts as valleys and due to tectonic activity, circuses have less development and evolution.
In the study of glacial cirques, the study of regional power and strength of cirques helps to identify the nature and how the developers of the effect during different periods on these glacial landforms. By measuring the dimensions and geometric shape of these landforms with mathematical and statistical methods, a lot of information can be extracted from them in terms of environmental and climatic conditions. The purpose of this study is to identify, classify and also analyze the morphometric, allometric and isometric characteristics of glacial cirques in the heights of Silveh basin on the border line between Iran and Iraq in West Azarbayjan province. In this work, the digital elevation model and its adaptation to the slope map classified in the software environment has been used. To identify and classify the glacial cirques of the region, the methods of Rudberg-Wilburg and Evans-Cox have been used. For morphometry and allometry of cirques in this range, indicators such as (W), (L), (H), (W / H), (L / H), (L / W), and the size of circuses are used. Be has been. Based on the results of the research, 33 glacial cirques in the heights of Silveh basin were determined, of which 2 circuses are in N2 category, 11 cirques are in N3 category, 15 cirques are in N4 category and 5 circuses are in N5 category. Examination of the forces of the basin shows that the coefficient b is 0.88 for the longitudinal region of N3, N2 circuses and 0.90 for N4 circuses, which is B <1. As a result, the behavior of the power forces is regional, and in general, the circuses under study in this area are not less than the degree of development, and Quaternary glaciers in this basin have had a poor performance
Keywords: Glacial Cirques, Morphometry, Allometry, Silveh Basin