Active Rock Glaciers and Protalus Lobes in the Western Kunlun Shan of China: A First Assessment

Active rock glaciers (ARGs) and protalus lobes (PTLs) are characteristic periglacial landforms indicating the presence and creeping process of permafrost underground in an alpine environment. However, little information of such landforms has been provided in mountainous western China. In this work, we compiled an inventory including ARGs and PTLs in part of the western Kunlun Shan based on satellite Synthetic Aperture Radar (SAR) interferometry and optical images from Google Earth. Six interferograms generated from ALOS-1 PALSAR images were used for identifying ground movements. Their geomorphic parameters such as aspect, area, altitude and slope angle, were quantified using the SRTM digital elevation model. Within the 700 km² study area, we identified 30 ARGs and 25 PTLs. The preliminary results reveal that the mean Line-of-Sight (LOS) velocities of the ARGs and PTLs are 36 cm/yr and 16 cm/yr, respectively. The maximum LOS velocity for the ARGs is about 95 cm/yr. The aspects of the landforms vary significantly: 43% of the ARGs are located on northeast-facing slopes while 28% of the PTLs are located on southeast-facing slopes. Our inventory shows the total areas covered by ARGs and PTLs are 4.8 km² and 0.7 km², respectively. The largest ARG has an area of 0.6 km². Both the ARGs and PTLs are located between 4100 m and 5600 m a.s.l. and have a mean slope angle of 18°. Compared with the existing rock glacier inventories in High Mountain Asia such as the northern Tien Shan and the Hindu Kush Himalaya, the distribution density of ARGs and PTLs in the western Kunlun Shan is much lower.