Shores of the East Siberian Sea
Shores of the East Siberian Sea – length of coastline comprises 5,918 km including the islands. The formation of the East Siberian Sea shores was influenced by general weakness of wave processes, caused by high ice coverage and good development of fast ice as well as evolvement of thermo-abrasive processes and instances of frost weathering. The coast of the East Siberian Sea within its official boundaries (the eastern boundary of meridian 108°E) is divided in two distinctive parts. The bigger western part of the coast, stretching from the New Siberian Islands to the mouth of the Kolyma, is low and flat. Here the sea is being approached for almost 1,000 km by a vast Yana-Indigirka lowland which is formed by the most recent fluviolacustrine and alluvial, occasionally marine sediments and is covered by permafrost. All the northern part of this lowland that is adjacent to the sea is 200–250 km wide and presents a tundra with thousands of thermokarst lakes and alases. It is cut by big rivers such as the Indigirka and the Kolyma and dozens of smaller rivers and streams.
The eastern part of the East Siberian Sea coast is an upland. Here mountain structures of the Kolyma Upland and the Chukotka Upland approach the sea. However, the mountains come close to the sea only in several limited areas. In most of this eastern part of the coast, the mountains are separated from the sea by chains of lagoons and coastal spits (from a kilometer to several dozen kilometers wide).
According to their geomorphic characteristics, the shores of the East Siberian Sea are divided into three areas: Oygossko-Kolymskaya (Merkushinskiy, Indigirskiy, and Indigiro-Kolymskiy Districts), Kolymsko-Chaunskaya (Letyatkinskiy and Rauchuanskiy Districts), and Shelagsko-Billingskaya (Vapkaraiskiy and Pegtymelskiy Districts).
Oygossko-Kolymskaya area is characterized by low relief of the land and extremely shallow continental slope (bottom slope ranges from 0.0003 to 0.0005), formed by very mobile silt. Coefficient of ice-free period here is from 16 % in the west to 14 % in the east. The ice line in the summer is very close to the shore. All of this put strict limits to the intensity and terms of wave impact on the shores. The Indigirka, Kolyma, and Alazeya carry away about 26 million tons of dredge annually. The surf zone displays mainly weak flows of wave energy, most of which is spent away from the coast due to the shallow continental slope. Energetic resultant of waves comprises from 140 ton-meter/year in the west to 85 ton-meter/year in the east.
To this it is necessary to add that almost all along the coast here, the sea is approached by the sediments constrained by permafrost. Thus, the shallowness of the continental slope, low relief of the coast, and permafrost and fluvial factor activity together with the limited chances of active wave processes determine all the peculiarities of the coastal morphology and dynamics within the coastal area under analysis.
From Cape Svyatoy Nos for more than 100 km, there stretches a flat thermo-abrasive coast known as Oygossky Yar, formed by an ice complex. A flat thermo-abrasive ledge is occasionally complicated by baidzherakhi. Deposits resulting from stream-bank erosion move eastward. According to the shore outline, it is possible to assume that in front of the entrance to Omulyakhskaya Guba, the deposit drift gets unloaded which has caused the appearance of Merkushin Spit here. In fact this low and flat coastal form, fringed with foreshores and fully flooded in times of big upsurge, is more likely to be a relict formation subject to thermo-abrasion. To its east there is also a thermo-abrasive coast stretching.
To the east of Guba Gusinaya, there is a vast mouth of the Indigirka River. To the east of the mouth, there is a large Alazeya projection in the shape of a bow curved in the direction of the sea. This is a straightened thermo-abrasive accretion coast characterized by weak flows of wave energy along the shore. Around Cape Krestovy the deposits migrate in two directions. The speed of thermo-abrasion in separate areas reaches 11 m/year. The accumulative areas of the shore are fringed with wind foreshores.
The Kolyma River forms a vast mouth with an area of more than 3,000 km2. The river flows into the East Siberian Sea in three arms named Chukochya, Prokhodskaya, and Kolymskaya.
Kolyma-Chaunskaya coastal area. To the east of the Kolyma mouth, there is a complex straightened coast formed by alternating areas of thermo-abrasive and soliflual and original abrasive cliffs and low accretion areas with beaches and wind foreshores. Soliflual and thermo-abrasive coasts are also very typical of Ayon Island lying at the entrance to Chaunskaya Guba, one of the biggest gulfs in the East Siberian Sea. On the northern shore of Ayon Island, there is a stretch of seashore terraces; the coast here is shallow and fringed with a wind foreshore.
The shores of Chaunskaya Guba are rather versatile which is due to both their exposure with respect to the resultant of waves and the direction of the local waves and their lithologic heterogeneity. Most of the coast of Chaunskaya Guba is low and formed by cryogenic lacustrine–alluvial deposits. This is where thermo-abrasive processes develop. Some areas of the shore have heavy solifluvial and avalanche masses accumulated at the cliff foot; the cliffs die out or their activity has long been stopped. In the shore indentations or in front of the river mouths, beaches and foreshores have appeared. In the region of Pevek, Cape Shelagskiy, and in some other places where the shore is formed by original (chalk and intrusive) rocks, abrasive cliffs in these rocks have developed.
Shelagsko-Billingskaya coastal area is special because branches of the Chukotka Upland come right up to the sea here. The shore is bold; the bottom slope is 0.01–0.02. Energetic resultants on the sea border of the coastal area are directed to southwest; their value ranges from 100,000 to 160,000 ton-meter/year. Long-term average annual ice edge comes almost right up to the shore, and the ice-free period comprises not more than 10 %. In the area from Cape Shelagskiy to Nolde Gulf, it is typical to find high abrasive cliffs formed in the original bedrock. The coastal area accepts fragmental products of rock frost weathering which become pebble depositions as they are immediate products of abrasion. Pebbled barriers isolate small lagoons from the sea. In general this part of the shore may be considered abrasive and accretion straightened.
Cape Billings is a complex of a heavy and complicated accretion form and not less complicated Valkakimanka Lagoon, separated from the cape by this barrier.
The New Siberian Archipelago consists of three groups of islands. The closest to the continent group is called Lyakhovsky Islands and consists of three large islands – Stolbovoy, Maly, and Bolshoy Lyakhovsky. Further to the north, there are the Anjou Islands consisting of huge islands: Kotelny, Faddeyevsky with Bunge Land and Novaya Sibir, as well as relatively small island Belkovsky. The northernmost group is the De Long Islands with small islands Bennett, Zhokhov, Vilkitsky, Henrietta, and Jeannette.
Kotelny, Faddeyevsky, and Bunge Land islands have long combined to form a single land massif. It is believed to have happened as a result of the contemporary upheaval of the islands. However, it is not unlikely that the fusion of the abovementioned islands was caused by accumulation of depositions and the subsequent drying up of the gulfs that previously separated them. This is proven first of all by the high intensity of thermo-abrasive processes on the island shores. The retreat of shores as a result of thermo-abrasion goes at a speed of 4 m on Novaya Sibir Island to 12 m on Bolshoy Lyakhovsky Island. Loose deposits of the recent time composing the coastal plains contain much cavern-load ice which forms high thermo-abrasive shores quite often complicated by numerous baidzherakhi. In the foundation of such shores, melt-out niches can be very prominent. The shores of Bunge Land are occasionally accumulative and present a unique Arctic sandy desert with typical wind-borne forms of relief that formed as a result of deposition accumulation in the decay zone between Faddeyevsky and Kotelny islands. There are high (up to 220 m high) denuded shores formed by massive rock. They are characteristic of the De Long Islands, Stolbovoy Island, and Belkovsky Island, sometimes in certain areas of the coast of Kotelny and Bolshoy Lyakhovsky islands. Bennett and Henrietta islands are covered by an ice sheet, and in the areas where it goes down to the sea, ice coast is developed.
A very shallow offshore zone of the New Siberian Islands is characterized by an unusual relief of submarine ridges that are parallel to the general direction of the shore. Formation of these forms of relief is connected with the wave activities, and these formations themselves present a series of large submarine bars surrounding Novaya Sibir Island, Zhokhov Island, and the Medvezhiy Islands.
Most of Wrangel Island is washed by the Chukchi Sea, a smaller part – by the East Siberian Sea. Here the scientists have pointed out a variety of rocks, predominantly metamorphically altered sediments. The rocks of Wrangel Island have been exposed to folding. The geologic structure of the island is based on two latitudinal anticlines, directed to the north. Half of the island’s surface has a mountain relief. Its base is formed by two mountain ranges corresponding to the two abovementioned latitudinal anticlines. In the east both the ranges get lower and turn into a plateau. The mountain slopes are dissected by numerous river valleys. There are various glacial relief forms proving the former glacier covering of the whole island. At the moment there are about ten small cirque glaciers, one of them descending right to the sea in the western part of the island. The mountainous part is almost surrounded by a piedmont plain mostly of fluvioglacial or alluvial origin. The plains boast of various cryogenic forms of microrelief, particularly polygonal forms. The shores of the island are different in the north, south, west, and east. The northern shore is low and fringed with a coarse sand and pebble bar which is mostly insular. To the south of the bar, there is a narrow lagoon connected to the sea by several straits. The southern shore is mostly characterized by alternation of low accretion areas and rock outcrops. This shore can be considered as one of an abrasive and accretion bay coast. In the east and west parts of the island, pre-quaternary rocks come right up to the sea forming high coastal ledges mostly developing under the influence of denudation processes.