Aerial photo from 1991
|Elevation||1,905 m (6,250 ft)|
|Volcanic arc/belt||Southern Volcanic Zone|
Mount Hudson (locally known as Volcán Hudson also Monte Hudson) is a stratovolcano in southern Chile, and the site of one of the largest eruptions in the twentieth century. The mountain itself is covered by a glacier. 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.
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 may have wiped out many if not all groups of early man living in central Patagonia at that time, based on evidence from the Los Toldos archaeological site.Recently, the volcano has had moderate eruptions in 1891 and 1971 as well as a large eruption in 1991.
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.
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 humans were killed but hundreds of people were evacuated from the vicinity. Ash fell on Chile and Argentina as well as in the South Atlantic Ocean and on the Falkland Islands. 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 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 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.
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.
A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava, tephra, pumice and ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and periodic intervals of explosive eruptions and effusive eruptions, although some have collapsed summit craters called calderas. The lava flowing from stratovolcanoes typically cools and hardens before spreading far, due to high viscosity. The magma forming this lava is often felsic, having high-to-intermediate levels of silica, with lesser amounts of less-viscous mafic magma. Extensive felsic lava flows are uncommon, but have travelled as far as 15 km (9.3 mi).
A lahar is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a river valley.
Mount Pinatubo is an active stratovolcano in the Zambales Mountains, located on the tripoint boundary of the Philippine provinces of Zambales, Tarlac and Pampanga, all in Central Luzon on the northern island of Luzon. Its eruptive history was unknown to most before the pre-eruption volcanic activities of 1991, just before June. Pinatubo was heavily eroded, inconspicuous and obscured from view. It was covered with dense forests which supported a population of several thousand indigenous Aetas.
Mount Rinjani is an active volcano in Indonesia on the island of Lombok. Administratively the mountain is in the Regency of North Lombok, West Nusa Tenggara. It rises to 3,726 metres (12,224 ft), making it the second highest volcano in Indonesia.
Mount Veniaminof is an active stratovolcano on the Alaska Peninsula. The Alaska Volcano Observatory currently rates Veniaminof as Aviation Color Code ORANGE and Volcano Alert Level WATCH as of 22 November 2018, at 2005 (UTC), after it being RED/WARNING since 21 November 2018, at 1915 (UTC). The mountain was named after Ioann Veniaminov (1797–1879), a Russian Orthodox missionary priest whose writings on the Aleut language and ethnology are still standard references. He is a saint of the Orthodox Church, known as Saint Innocent for the monastic name he used in later life.
Mount Okmok is the highest point on the rim of Okmok Caldera on the northeastern part of Umnak Island in the eastern Aleutian Islands of Alaska. This 5.8 mile (9.3 km) wide circular caldera truncates the top of a large shield volcano. A crater lake once filled much of the caldera, but the lake ultimately drained through a notch eroded in the northeast rim. The prehistoric lake attained a maximum depth of about 150 m (500 ft) and the upper surface reached an elevation of about 475 m (1560 ft), at which point it overtopped the low point of the caldera rim. Small, shallow remnants of the lake remained north of Cone D at an altitude of about 1075 feet: a small shallow lake located between the caldera rim and Cone D; a smaller lake farther north near the caldera's gate. After the 2008 eruption, the hydrogeology of the caldera was greatly changed with five separate sizable lakes now emplaced. In addition to the caldera lakes, Cone A, Cone E, Cone G and the new 2008 vent on Cone D contain small crater lakes. The last major eruptions of Okmok—with a VEI strength of 6—occurred 8,300 and 2,400 years Before Present.
Viedma is a subglacial volcano located below the ice of the Southern Patagonian Ice Field, an area disputed between Argentina and Chile. The 1988 eruption deposited ash and pumice on the ice field and produced a mudflow that reached Viedma Lake. The exact position of the edifice is unclear, both owing to the ice cover and because the candidate position, the "Viedma Nunatak", does not clearly appear to be of volcanic nature. Numerous ash layers in the Viedma lake indicate numerous past eruptions.
Cerro Azul, sometimes referred to as Quizapu, is an active stratovolcano in the Maule Region of central Chile, immediately south of Descabezado Grande. Part of the South Volcanic Zone of the Andes, its summit is 3,788 meters (12,428 ft) above sea level, and is capped by a summit crater that is 500 meters (1,600 ft) wide and opens to the north. Beneath the summit, the volcano features numerous scoria cones and flank vents.
Villarrica is one of Chile's most active volcanoes, rising above the lake and town of the same name, 750 km (470 mi) south of Santiago. It is also known as Rucapillán, a Mapuche word meaning "devil's house". It is the westernmost of three large stratovolcanoes that trend NW-SW obliquely perpendicular to the Andean chain along the Mocha-Villarrica Fault Zone, along with Quetrupillán and the Chilean portion of Lanín, are protected within Villarrica National Park. Guided ascents are popular during summer months.
The Llaima Volcano is one of the largest and most active volcanoes in Chile. It is situated 82 km northeast of Temuco and 663 km southeast of Santiago, within the borders of Conguillío National Park.
Mentolat is an ice-filled, 6 km (4 mi) wide caldera in the central portion of Magdalena Island, Aisén Province, Chilean Patagonia. This caldera sits on top of a stratovolcano which has generated lava flows and pyroclastic flows. The caldera is filled with a glacier.
Operation Fiery Vigil was the emergency evacuation of all non-essential military and U.S. Department of Defense civilian personnel and their dependents from Clark Air Base and U.S. Naval Base Subic Bay during the June 1991 eruption of Mount Pinatubo in the Philippines.
Sollipulli is an ice-filled volcanic caldera and volcanic complex, which lies southeast of the small town of Melipeuco in the La Araucanía Region, Chile. It is part of the Southern Volcanic Zone of the Andes, one of the four volcanic belts in the Andes chain.
Christopher G. Newhall is a volcanologist, formerly with the U.S. Geological Survey and the Earth Observatory of Singapore. He is the co-creator of the Volcanic explosivity index and specializes in volcanic prediction.
The Silverthrone Caldera is a potentially active caldera complex in southwestern British Columbia, Canada, located over 350 kilometres (220 mi) northwest of the city of Vancouver and about 50 kilometres (31 mi) west of Mount Waddington in the Pacific Ranges of the Coast Mountains. The caldera is one of the largest of the few calderas in western Canada, measuring about 30 kilometres (19 mi) long (north-south) and 20 kilometres (12 mi) wide (east-west). Mount Silverthrone, an eroded lava dome on the caldera's northern flank that is 2,864 metres (9,396 ft) high, may be the highest volcano in Canada.
Chaitén is a volcanic caldera 3 kilometres (2 mi) in diameter, 17 kilometres (11 mi) west of the elongated ice-capped Michinmahuida volcano and 10 kilometres (6 mi) northeast of the town of Chaitén, near the Gulf of Corcovado in southern Chile. The most recent eruptive phase of the volcano erupted on 2008. Originally, radiocarbon dating of older tephra from the volcano suggested that its last previous eruption was in 7420 BC ± 75 years. However, recent studies have found that the volcano is more active than thought. According to the Global Volcanism Program, its last eruption was in 2011.
Lake Pinatubo is the summit crater lake of Mount Pinatubo formed after its climactic eruption on June 15, 1991. The lake is located in Botolan, Zambales, near the boundaries of Pampanga and Tarlac provinces in the Philippines. It is about 90 km (56 mi) northwest of the capital city of Manila. While one paper by researchers from Japan suggested a depth of 600 m (2,000 ft), more detailed research suggests that 95–115 m (312–377 ft) is more accurate.
The 1991 eruption of Mount Pinatubo was a significant volcanic eruption in the Luzon Volcanic Arc of the Central Luzon region of the Philippines. Eruptive activity began on April 2 as a series of phreatic explosions from a fissure that opened on the north side of Mount Pinatubo. Seismographs were set up and began monitoring the volcano for earthquakes. In late May, the number of seismic events under the volcano fluctuated from day-to-day. Beginning June 6, a swarm of progressively shallower earthquakes accompanied by inflationary tilt on the upper east flank of the mountain, culminated in the extrusion of a small lava dome.
This timeline of volcanism on Earth is a list of major volcanic eruptions of approximately at least magnitude 6 on the Volcanic Explosivity Index (VEI) or equivalent sulfur dioxide emission around the Quaternary period.