Porvenir, capital of the Chilean Province of Tierra del Fuego, located on the main island, and, on Navarino Island, Puerto Williams, which is the capital of the Antártica Chilena Province. Puerto Toro lies a few kilometers south of Puerto Williams. Arguably, it is the southernmost village in the world. The mostly uninhabited islands north and west of the main island are part of Magallanes Province. The eastern part of the main island and a few small islands in the Beagle Channel belong to Argentina. They are part of the Tierra del Fuego, Antarctic Territory and South Atlantic Islands Province, whose capital is Ushuaia, the largest city of the archipelago. The other important city in the region is Río Grande on the Atlantic coast. The Cordillera Darwin in the southwestern part of the main island contains many glaciers that reach the ocean. While Mount Darwin had previously been thought to be the tallest mountain in the archipelago, this distinction now belongs to the unofficially named Monte Shipton at . The topography of Tierra del Fuego can be divided into four regions: an outer archipelago region () to the south and west, a mountainous region in the south (), a plains region () plus a sub-Andean zone in-between the last two zones (). Geology The geology of the archipelago is characterized by the effects of the Andean orogeny and the repeated Pleistocene glaciations. The geology of the island can be divided into large east–west-oriented units. The southwestern islands of the archipelago, including Cape Horn, are part of the South Patagonian Batholith, while the Cordillera Darwin and the area around the Beagle Channel form the principal mountain range hosting the highest mountains. The Magallanes fold and thrust belt extends north of Almirantazgo Fjord and Fagnano Lake, and north of this lies the Magallanes foreland, an old sedimentary basin that hosts hydrocarbon reserves. Orthogneiss dated at 525 million years is known to underlie some of the oil wells in northern Tierra del Fuego. The Magallanes–Fagnano Fault, a sinistral strike slip fault crosses the southern part of the main island from west to east. It is an active fault, located inside and parallel to the Fuegian fold and thrust belt, and marks the boundary between a southern belt of Paleozoic meta sediments and a northern Mesozoic belt of sedimentary sequences. Fagnano Lake occupies a glacier-carved depression in a pull-apart basin that has developed along the