Thermal Abrasion – the process of destruction of the shorelines composed of ice or multiyear frozen rocks, resulting from combination of the mechanical action of breaking waves and thermal action of water and air (mechanical and heat energy). The processes of thermal abrasion are most intensive in the Laptev Sea, with the shoreline retreating up to 18 m/year. T.A. in the Laptev Sea led to disappearance of the islands, the length of which at the time of their discovery in the nineteenth century exceeded 10 km. This way, former Vasilyevsky Island, which was around 7 km long and 0.5 km wide in 1823, totally disappeared by 1936. Former Semyonovsky Island, 14 km long in 1823, stopped to exist in 1951. During 2 years – from 1944 to 1946 – the record speed of shoreline erosion, 55 m/year, was recorded there. Within decades the Figurin, Diomede, and Mercury Islands disappeared.