Dynamics of the development of thermocirque with massive ice bed near the village of Lavrentia (Chukotka Autonomous Okrug) for 2018-2021

Abstract

Massive ice beds are unique natural formations of cryolithozone, as well as important objects of research in the area of reconstruction of paleogeographic conditions and solution of the tasks of engineering geology. On the plains of Chukchi Peninsula, massive ice beds are common and represent regional geological peculiarity. The article traces the dynamics of recession of the edge of thermocirque and the evolution of the morphology of ice bed outcrop in 7 km south of the village of Lavrentia (Chukotka Autonomous Okrug) over the period from 2018 to 2021. The results of field observations indicate the active development of thermocirque over 4 years: its back wall in both corridors receded by 50-60 meters, increasing the area of the thermocirque by 3-4 times. The shape of the outcropping massive ice bed changed over time: in 2018, its main part was exposed in the northern part, in subsequent years, the bed was outcropped mainly in the northern part from the side of the deposits remnant (southern side) and in the southern part. The width of the bed varied from 5 m in 2018 to 15-20 m in 2019 and 2021. The ice thickness also varied in the northern part of the thermocirque from 2 m in 2018 to 6 m in 2019, while in the southern corridor it remained stable in 2020-2021 (about 5 m). A hypothesis has been put forward on the mechanism and time of ice bed formation. The acquired results suggest that the ice bed may have heterogeneous segregation-injectional genesis. It is revealed that the ice bed under review is part of a larger ice body and was outcropped as a result of the cyclic fluctuations of climatic characteristics that determine the depth of seasonal thawing of the soil.