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In the afternoon of 30 January 2017, a catastrophic outburst flood occurred in the Larsemann Hills (Princess Elizabeth Land, East Antarctica). The rapid drainage of both a thin supraglacial layer of water (near Boulder Lake) and Lake Ledyanoe into the englacial Lake Dålk provoked its overfill and outburst. As a result, a depression of 183 m × 220 m was formed in the place where Lake Dålk was located. This study summarises and clarifies the current state of knowledge on the flood that occurred in 2017. We present a phenomenological model of depression formation. We specify the reasons for the outburst of the system of lakes Boulder, Ledyanoe and Dålk. In addition, we carry out mathematical modelling of the outburst of each of the three lakes and estimate the flood severity. Outburst hydrographs, channel diameters, volume and duration of floods were calculated. Particular simulation results were validated with field data. In conclusion, we give an overview of the new outburst cycle of the lake system, which began in 2020 with the drainage of the lakes Boulder and Ledyanoe, and the new formation of Lake Dålk. Further research is required to improve our understanding of the lake system responses to changing external factors.

The destruction of ground dams, of natural and artificial origin, is caused by certain critical conditions. The main reasons for this are the overflow of water over the crest of a dam, the filtration of water through its body, or mechanical destruction. The processes of destruction of ground dams of moraine lakes are very frequent phenomena for mountain regions and can often occur there. In addition, the outburst of ground dams can take place under the thickness of the cover and mountain glaciers that leads to the formation of the subglacial hydrographic drainage system. Because of the dam destruction, outburst floods, which are accompanied by significant destruction and even human losses, are formed. Considering that, it is extremely difficult and unsafe to investigate the outburst process directly at the time of its natural occurrence, the researchers turn to alternative methods, like physical modeling. In this paper, the results of physical modeling of the outburst of the moraine model reservoir are presented. The experiment was carried out near the coastline of the outburst glacier lake Bashkara (Central Caucasus, Elbrus Region, Russia). Therefore, the artificial dam, consisting of material of moraines surrounding the lake, was created. This leads to a possibility to recreate the experimental conditions closest to natural. During the research photography and video filming of the outburst of the model reservoir were carried out. The results of physical modeling are in complete agreement with previously published data of outburst of ground dams and do not contradict with the physical essence of the process.

There is a reduction in the area of glaciation of mountain massifs as a result of climate warming, which leads to the formation of lake-glacial complexes in areas of glaciation degradation. These complexes are dynamic systems that are rapidly changing over time, therefore, unstable and potentially outburst. Moraine and periglacial lakes outbursts are dangerous hydrological phenomena. As a result of outbursts catastrophic floods and mudflows can form, causing serious damage to the infrastructure of settlements located downstream and often leading to human toll. Therefore, the study of outburst-hazardous lakes is necessary and is an important applied problem associated with forecasting natural hazards. In this paper an the outburst hazard of little-studied moraine and periglacial lakes at the Mongun-Taiga mountain massif (Tyva Republic, Russian Federation) assessment was carried out using the scoring method, supplemented taking into account regional characteristics, using data from remote sensing of the Earth. The performed assessment according to satellite images showed that most of the massif's lakes have a high outburst hazard. Based on the assessment results a group of lakes was selected located in the right branch upstream of the river “Tolaity” for the purpose of a more detailed field survey (hydrological and geophysical studies were carried out). Field work carried out on the selected group of lakes allowed us to correct the performed assessment. In paper the applicability of the method based on comparing field data and data obtained from satellite images was estimated.

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