Mount Hudson ( es, Volcán Hudson, es, Monte Hudson, label=none) is a stratovolcano in southern

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the eas ...

, and the site of one of the largest eruptions in the twentieth century. The mountain itself is covered by a

glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such a ...

. There is a caldera at the summit from an ancient eruption; modern volcanic activity comes from inside the caldera. Mount Hudson is named after Francisco Hudson, a 19th-century Chilean Navy hydrographer.

Eruptive history

The first large explosive eruption of the volcano dates, the "H₀" eruption, to around 15,450 BCE. Subsequent large eruptions around 4750 BCE and 1890 BCE are believed to have been of Volcanic explosivity index (VEI) 6; these are probably responsible for the large caldera. The 4750 BCE eruption, also known as "H₁", may have wiped out many or all of the groups living in central Patagonia at that time, based on evidence from the Los Toldos archaeological site, and the sudden ceasing of rock art production in the area around that time, including the utter cessation of Stylistic group A at Cueva de las Manos. The 1890 BCE eruption known as "H₂" (ca. 3,900 a cal BP) is known to have deposited an ash layer of about 5 cm as far east as the shores of San Jorge Gulf in the Atlantic coast A microscopic ash layer from the H₂ eruption has also been reported in a peat bog in the

Falkland Islands The Falkland Islands (; es, Islas Malvinas, link=no ) is an archipelago in the South Atlantic Ocean on the Patagonian Shelf. The principal islands are about east of South America's southern Patagonian coast and about from Cape Dubou ...

, more than 1200 km east of Mount Hudson Recently, the volcano has had moderate eruptions in 1891 and 1971 as well as a large eruption in 1991. This last eruption is known as "H₃".

1971 eruption

Before 1970, little was known about the mountain. Minor eruptive activity began in 1970 and melted parts of the glacier, raising river water levels and leading to the identification of the caldera. In August–September 1971, a moderate eruption (VEI 3) located in the northwest area of the caldera sent ash into the air and caused lahars from the melting of a large portion of the glacier. The lahars killed five people; many more were evacuated.

1991 eruption

The eruption in August to October 1991 was a large plinian eruption with a VEI of 5, that ejected 4.3 km³ bulk volume (2.7 cubic km of dense rock equivalent material). Parts of the glacier melted and ran down the mountain as mud flows (see glacier run). Due to the remoteness of the area, no-one was killed but hundreds of people were evacuated from the vicinity. Ash fell on Chile and

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, t ...

as well as in the South Atlantic Ocean and on the

. In 1992, John Locke Blake, then resident on Estancia Condor, south of Rio Gallegos, in Argentina describes the effects of the eruption vividly. He describes an ash fall up to 15 cm in depth, covering some 150,000 to 180,000 square kilometres in a triangle from Los Antiguos to Deseado to San Julian to a depth of between 5 and 10 cm. He reports that the

hygroscopicity Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substa ...

of the silica caused the formation of morasses around drinking places causing sheep to be trapped and die in huge numbers. He records that 'ten years later, most of the farms in the affected area are empty, of sheep and of people'. In addition to the ash, a large amount of sulfur dioxide gas and aerosols were ejected in the eruption. These contributed to those already in the atmosphere from the even larger

1991 eruption of Mount Pinatubo The 1991 eruption of Mount Pinatubo in the Philippines' Luzon Volcanic Arc was the second-largest volcanic eruption of the 20th century, behind only the 1912 eruption of Novarupta in Alaska. Eruptive activity began on April 2 as a series of ...

earlier in the year and helped cause a worldwide cooling effect over the following years. Ozone was also depleted, with the Antarctic ozone hole growing to its largest levels ever recorded in 1992 and 1993. As a result of the Mount Pinatubo eruption, the Hudson eruption received little attention at the time.

October–November 2011 eruption

On October 26, the Chilean Service for Geology and Minery issued a red alert and a mass evacuation of the region surrounding the volcano, fearing an imminent eruption in the coming hours or days. It happened on Oct 31 but was small and didn't do any damage to the area.

References

External links

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Mount Hudson at AGU

{{DEFAULTSORT:Hudson, Mount Mountains of Aysén Region Stratovolcanoes of Chile Active volcanoes Subduction volcanoes VEI-6 volcanoes Volcanoes of Aysén Region South Volcanic Zone 20th-century volcanic events Holocene stratovolcanoes