Features of the formation of the coasts of Chukotka and the Koryak highlands

Abstract

Long-term expeditionary studies of the Geography Faculty of Lomonosov Moscow State University of the Arctic coast of Russia (1969 – 2015) have provided extensive material on hydrology, channel morphodynamics and geomorphology of the estuaries of large rivers from the Northern Dvina to the Kolyma. The joint work of the Moscow State University and the M. K. Ammosov North-Eastern Federal University made it possible to signifiantly expand the geography of research to the coasts of the Chukchi and Bering Seas. Based on the analysis of geological and geomorphological data and an array of published and archival materials, it was possible to establish patterns and specifi features of coastal and estuarine processes in the fial phase of stabilization of the post-glacial ocean transgression. Over the past 7-5 thousand years, floding of low-lying hilly coastal plains, river valleys and fjords has occurred. The active impact of the wave activity of the sea led to the erosion of the upper part of the underwater slope, the restructuring of its profie and the retreat of accumulative forms towards the land and the creation of modern outlines of the coastline. The sections of the coast extended into the sea, composed by a thickness of loose quaternary sediments, were partially eroded by waves, and sediments were involved in longitudinal and transverse movements, forming braids and embankments, which led to a general alignment of the coastline. Currently, in conditions of rising sea levels, the general trend towards the restructuring of the underwater slope and the coastal zone persists and can be extremely dangerous for coasts composed of strongly icy sandy-loamy alluvial-lacustrine deposits. A further increase in global temperature will signifiantly soften the climate of the Arctic coasts, cause the degradation of permafrost, thawing of underground ice and accelerate the process of retreat of coastal abrasion ledges, the sea edge of river deltas. Taking into account the regional geological and geomorphological features of the coasts of the Chukchi and Bering Seas, it should be expected that a possible rise in sea level will lead to thawing and degradation of permafrost rocks and vein ice.