Semyonovsky Island – was an island in the New Siberian Islands, located 63 km to the west from the northern end of the Stolbovoy Island. The island was stretched in the direction northeast–southwest; its length was 2 km (according to other sources 15 km) with the maximum length around 600 m. It was formed by sand and clay deposits with inclusions of fossil ice. The surface of the island was plain of up to 25 m high. The coasts were steep with cliffs 14–16 m high. In the 1950s the island eroded down (fossil ice melted) into a sandbar. It was discovered by M. Lyakhov, a merchant from Yakutsk, in 1815.