Isla Grande de Tierra del Fuego
The eastern opening is a wide bay on the border of Chile and Argentina between Punta Dúngeness on the mainland and Cabo del Espíritu Santo ("Cape of the Holy Spirit") on Tierra del Fuego, the border as defined in the Treaty of Peace and Friendship of 1984 between Chile and Argentina. Immediately west are Primera Angostura and Segunda Angostura, narrows formed by two terminal moraines of different ages. The Primera Angostura is the closest approach of Isla Grande de Tierra del Fuego to mainland South America. Farther west lies Magdalena Island, part of Los Pingüinos Natural Monument. The strait's southern boundary in the east follows first the shoreline of the Isla Grande de Tierra del Fuego, then the northern end of the Canal Whiteside and the shoreline of Dawson Island.