Тэрхийн Цагаан нуурын хотгорын морфодинамик хөгжил

Morphodynamic development of Terkhiin Tsagaan Lake depression, Central Mongolia

Abstract

Data on the origin and morphology of lake depressions in Mongolia is poor and only 2 percent of total studies. The morphological patterns of the lake depressions caused by volcanic activity have not been well studied in Mongolia. The morphometric indicators of Khorgo volcanic lava plateau, its effect on the morphological changes of the lake depression, and the relationship between them are not studied in detail. The Khorgo volcanic lava is analyzed to clarify how it formed and compare it to the origin of the neighbouring Terkhiin Tsagaan Lake depression. This paper is defined the effect of Khorgo volcanic lava plateau on the origin of the Terkhiin Tsagaan Lake depression, based on morphometric analysis, remote sensing and geological mapping. Also study is checked by field measurements as identifying fault lengths, locations and morphology. Upon the Khorgo volcano activation, the valley of the Terkh River was dammed by a lava plateau. Lava damming formed the Terkhiin Tsagaan Lake depression, blocking the Terkh River valley. Another evidence is the age of the lava plateau and lake sediment. Terkhiin Tsagaan Lake area was three times larger than it is now (9000 years ago), comparing the terraces on the shoreline of the lake. The lake water outflows via the Suman River. The Suman River diversion has created a large canyon along fault. Changes in the water volume of Terkhiin Tsagaan Lake and the erosion of the Suman Gol canyon are inversely related.  This study is concerned that the effect of the youngest volcano in Central Asia is achieved a role in the development of lake depression, and presents a basis for integrating morphometric analysis to define the main phases of volcanic activity and lake depression evolution. Current lake area and volume is under influences of climate and environmental changes and human activities.