Dawson Island ( Lat : 53 Â 58 â 12 â S Long : 70 Â 34 â 48 â W ) is an island in the Strait of Magellan that forms part of the Tierra del Fuego archipelago , 100 km south of the city of Punta Arenas in Chile , and part of the Municipality of Punta Arenas . Dawson Island ( Lat : 53.97 Â S Long : 70.58 Â W ) is an island in the Strait of Magellan that forms part of the Tierra del Fuego archipelago , 100 km south of the city of Punta Arenas in Chile , and part of the Municipality of Punta Arenas .