Lena Trough

a rift valley between the underwater Gakkel and Knipovich ridges in the Arctic Ocean. It extends approximately along 1° E long. Depths in the southern part are 3,-500–3,900 m; in the northern, 3,100–3,400 m. The trough was discovered by Soviet expeditions on the ships Ob’ and Lena in 1957 and 1958.