| Semyonovsky | |
| Native Name: | остров Семёновский |
| Native Name Lang: | Russian language |
| Settlement Type: | Island |
| Coordinates: | 74.2528°N 133.925°W |
| Pushpin Map: | Russia Sakha Republic |
| Pushpin Label Position: | top |
| Subdivision Type: | Country |
| Subdivision Name: | Russian Federation |
| Subdivision Type1: | Federal subject |
| Subdivision Name1: | Far Eastern Federal District |
| Subdivision Type2: | Republic |
| Subdivision Name2: | Sakha Republic |
Semyonovsky Island ('о. Семёновский' in Russian) was an island in the Lyakhovsky Islands subgroup of the New Siberian Islands. It was located in the southwestern area of the archipelago, in the eastern part of the Laptev Sea.
Before its disappearance, it was at 4 km2, one of the smallest islands in the archipelago. In 1945, just before it disappeared, its sea cliffs rose about 24 meters above sea level.[1] [2]
Mr. I. Lyakhov, a merchant from Yakutsk, discovered this island in 1770. He discovered it by following the tracks of an enormous herd of reindeer across frozen sea ice. Czarina Catherine II rewarded him for discovering this and another island in the New Siberian Island archipelago with the exclusive rights to collect fossil ivory from them.[3]
After its discovery, Semenovsky Island rapidly decreased in size until it disappeared between 1952 and the early 1960s. The area of Semyonovsky Island was 4.6 km2 in 1823, 0.9 km2 in 1912, 0.5 km2 in 1936, and 0.2 km2 in 1945. In 1950, it was only a solitary baydzharakh (thermokarst mound). By 1952, it had been eroded down into a sand bar lying just above the sea surface. When Semyonovsky Island was visited in the early 1960s, it had vanished and only a sand shoal with an average depth of 10 m and minimum depth of 0.2 m remained.[1] [2]