The island is approximately long east-west, and wide, with an area of . The island is deeply indented by bays. Its highest point is , and is considered to be the last
prominence of the
Andes mountain range. It receives around of rain per year. The island is surrounded by minor islands and rocks, the largest being
Observatorio island north, with an area of . At the eastern end of the island is Cape Saint John, a landmark for ships sailing around the island in order to avoid the currents and tides of the Le Maire Strait to the west. The only settlement is the Puerto Parry Naval Station, located in a deep and narrow
fjord on the northern coast of the island. The naval station, established in 1978, is staffed by a team of four seamen on a 45-day rotation. They monitor environmental conservation and ship movements, and provide emergency assistance.
Geology The island's
Formation is mainly
Jurassic Lemaire, which is
tuffs and
lavas. The
Islas Año Nuevo,
Isla Observatoria, and the
Caleta Lacroix region on the west coast, however, have exposures of the Jurassic-
Cretaceous Beauvoir Formation, mainly composed of
shales,
mudstones,
limestones, and
graywacke, plus silt, clay, sand and gravel glacial
fluvial deposits. There are at least 18
fjords, with associated glacial sediments such as
moraines and
till, especially prevalent at Cape San Antonio and Cape Colnett on the north coast. Key fjords on the north coast include Port Hoppner, Port Parry, Port Basil Hall, Port Año Nuevo, Port Cook, and Port San Juan Del Salvamento going east to west. Key fjords on the south coast include
Bahía Capitan Cánepa, Port Lobo, Port Vancouver, and
Bahía Blossom, going east to west. Cape Kempe on the south coast lies opposite Cape San Antonio.
Climate The island has a cold and humid climate and is characterized by rapid and unpredictable changes in the weather from day to day. Under the
Köppen climate classification, despite the vegetation, it would be classified as a mild
tundra climate (
ET), a cold climate with a mean temperature in the warmest month below with abundant precipitation year-round. The climate of the island is strongly influenced by the subpolar low pressure system which develops around the
Antarctic Circle and the surrounding oceans. Being located between the semi–permanent high pressure cell and the subpolar low (which does not change in intensity through the year and have little seasonal variation), the island is exposed to
westerlies throughout the year. Temperatures are low year round but without extreme minimum temperatures. The mean temperature in summer is with mean extremes of and while in winter, the mean temperature is with mean extremes of and . Mean temperatures are lower than in
Tierra del Fuego but due to the moderating influence of the ocean, extreme minimum temperatures are higher than in Tierra del Fuego. Coastal areas have average temperatures above in the coldest month while higher altitude locations may average below . Though no reliable records are available, it is estimated that the island averages around of precipitation per year. However, owing to its relief, precipitation is highly variable across the island. In the eastern parts of the island, it averages based on four years of data. Precipitation occurs frequently on the island, averaging 252 days with precipitation. June is the wettest month while October is the driest. Thunderstorms are very rare. Snow frequently falls during the winter months, averaging 33 days, although snow can fall during autumn and spring. The island receives high cloud cover throughout the year, with 74% of the days being cloudy. June is the cloudiest month while October is the least cloudy month. Fog is uncommon, averaging only 16 days per year. Similar to the rest of
Patagonia, the island is exposed to strong westerly winds. These winds often carry moisture with them, leading to frequent storms. Average wind speeds range from a high of in August to a low of in December.
Flora and fauna Isla de los Estados is covered with dense low forests of
Nothofagus (southern beech). The animal life is composed mainly of
penguins,
orcas,
seals,
seagulls, and
cormorants, as well as human-introduced
deer and
goats. The island is the location of one of the more southerly
Atlantic breeding colonies of the
Magellanic penguin. As early as the last part of the 18th century, Isla de los Estados was used as a seal harvesting location. The island and surrounding waters, including the
Burdwood Bank, an
ocean bank to its east, have been designated an
Important Bird Area (IBA) by
BirdLife International because it supports significant populations of
southern rockhopper and Magellanic penguins,
imperial shags, and
striated caracaras. ==See also==