Озёра у ледника Малый Азау на Эльбрусе: динамика и прорывы

The lake dynamics and the current state of them were analyzed on the basis of interpretation of aerial and satellite images of different years together with results of field surveys. Areas of six lakes existing in different years near the Maliy Azau Glacier had been determined. On August 22, 2011, the maximum area of one of the lakes was equal to 25.5 thousand m2. The first outburst was caused by the landslide deformations of the moraine massif forming a part of the lake basin, while the second one was a result of degradation of the lake ice dam and the water overflow on top of it. The present‑day lake dams (terminal‑moraine ramparts and medial moraine ridges) are the result of the Maliy Azau Glacier advance in 1990s. The revealed feature of the lake dynamics on the mountain Elbrus was a drop of the water level and corresponding decrease of the lake areas in winter that was related to existence of the groundwater runoff into fractured volcanic rocks. At present, moraine dams of lakes and areas of the surface water runoff from the lakes are in stable condition due to which there is no threat of a lake outburst. However, the potential threat of outburst still remains because of high seismicity and possible volcanic activity in this region.На основе дешифрирования аэрофотоснимков и космических снимков приводятся данные о количестве и динамике озёр у ледника Малый Азау за 1957–2015 гг. Наибольшая площадь озера (25,5 тыс. м2) зафиксирована на космоснимке 22.08.2011 г. незадолго до прорыва. Прорывы озёр происходили в 1978 и 2011 гг. и имели разные причины. Первый прорыв связан с оползневыми деформациями моренного массива, слагающего часть озёрной котловины, второй – с деградацией ледяной плотины озера и переливом воды поверх неё. Установлен также факт значительного падения уровня воды в озёрах в зимний период

Эволюция озёр у ледника Джикиуганкез (Северное Приэльбрусье) в 1957–2020 гг. с учётом подземных каналов стока

Evolution of lakes near the Dzhikiugankez Glacier in the north of Elbrus for the period of 1957–2020 was studied using a comparative interpretation of aerial and satellite images as well as aerial and ground surveys in 2007–2018. Within this period the area of the Dzhikiugankez Glacier (43,35 N, 42,53 E) decreased by 8.2 km2. On the territory previously occupied by the glacier and close to it, 19 lakes appeared at different times, which dynamically developed and broke through. The lakes cover the area of 0.43 km2, that equals to 5.21% of the total icefree area. The average area of the lakes is 26.6 thousand m2. The maximum (the lake East Birdzhaly) is 89 thousand m2. In total there were six lakes larger than 25 thousand m2. They are concentrated in depressions on the surface of an ancient lava flow dammed by glaciers, dead ices and moraine lines. At a certain stage in the evolution of lakes, water from them penetrated through these barriers and, thus, formed subglacial and underground drainage channels. In 2013, during helicopter flights, an underground drainage channel with a length of more than 80 m was detected in the moraine line around the Lake «Podkova». The survey made possible to determine decreasing in the lake level by 2 m, and the accumulation of water with a volume of up to 48 thousand m3 in the cavities of the moraine massif, until it reaches the outer slope. The accumulated volume of water interflowed through the underground channel gradually, but despite the pot-holes on its bottom, no mudflow happened in the valley. Although in another case, the formation of an underground drainage channel from the Severnoye Chungurchat Lake was accompanied by a lake breakthrough and a mudflow. Other characteristic features of the evolution of lakes and changes in the direction of drainage from glaciers are also analyzed in the paper.По данным дешифрирования аэрофотоснимков и космических снимков за 1957–2020 гг., а также полевых наблюдений и вертолётных облётов определены особенности эволюции озёр у ледника Джикиуганкез и механизмы их прорыва, в том числе по подземным каналам. На примере озёр Подкова, Северное Чунгурчат и Балык Южное показано, что формирование подземных каналов стока не обязательно приводит к сходу селевых потоков, однако даже небольшие озёра могут быть очагами значительных селей

Lakes near the glacier Maliy Azau on the Elbrus (Central Caucasus): dynamics and outbursts

The lake dynamics and the current state of them were analyzed on the basis of interpretation of aerial and satellite images of different years together with results of field surveys. Areas of six lakes existing in different years near the Maliy Azau Glacier had been determined. On August 22, 2011, the maximum area of one of the lakes was equal to 25.5 thousand m2. The first outburst was caused by the landslide deformations of the moraine massif forming a part of the lake basin, while the second one was a result of degradation of the lake ice dam and the water overflow on top of it. The present‑day lake dams (terminal‑moraine ramparts and medial moraine ridges) are the result of the Maliy Azau Glacier advance in 1990s. The revealed feature of the lake dynamics on the mountain Elbrus was a drop of the water level and corresponding decrease of the lake areas in winter that was related to existence of the groundwater runoff into fractured volcanic rocks. At present, moraine dams of lakes and areas of the surface water runoff from the lakes are in stable condition due to which there is no threat of a lake outburst. However, the potential threat of outburst still remains because of high seismicity and possible volcanic activity in this region