Hudson Volcano - John Seach



45.90 S, 72.97 W
summit elevation 1905 m

Note: There is a volcano in Antarctica called Hudson Mountains.

Hudson volcano is the southernmost volcano of the Chilean Southern Volcanic Zone. It is located 280 km from the Nazca-Antarctica-South American triple junction. Volcanic activity results from subduction of the Nazca plate beneath the South American plate.

Hudson volcano is just north of 300 km long Patagonian Volcanic Gap (46–49°S), which is related to the subduction of the Chile Rise over the last 8 million years. The volcano contains a 10 km wide, almost circular caldera is filled with glacial ice, which drains into the Huemules glacier to the north.

Eruptions of Hudson volcano
There have been at least 12 Holocene explosive eruptions at Hudson volcano. The largest eruptions occurred 6,700 years ago, the 3,600 yrs ago, and 1991. The eruption in 1991 was one of the largest of the 20th century.

2011 Eruption
A large exclusion zone of 45 km was placed around Hudson volcano on 26th October 2011, and the highest level 5 alert announced after a minor eruption. Steam and minor ash emissions reached height of 5.5 km on Thursday 27th October.

2007 Earthquake
On 21st April, 2007, a Magnitude 6.2 earthquake occurred at about 13:50 local time in the Aisén Fjord, 50 km north of Hudson volcano. The earthquake was considered responsible for the eruption of Chaiten volcano, 250 km north of the earthquake epicentre in May 2008.

1991 Eruption
An eruption of Hudson volcano began on 8th August 1991 at 18:20 hr. Phreatomagmatic eruptions from the NW part of the caldera produced a 400 m wide hole in the glacier, and lava flows from and a 4 km long, NNE-SSW trending fissure. The paroxysmal phase of the eruption began on August 12th (12:00 hours) with
a Plinian eruption forming an 800-m-wide crater 4 km SSE of the first crater. The eruption column reached 16 km high on 13th August. Ash fell on the Falkland Islands (Malvinas Islands) 1000 km SE, and covered 100,000 sq km of southern Patagonia. On 20th August 1991 ash reached SE Australia 15,000 km east of the volcano. An aircraft flying between Sydney and Melbourne had an encounter with volcanic ash. Passengers and crew noticed a strong sulphurous smell in the cabin.

Effects of the region
Ashfall from Hudson eruption produced ashfall, damaged houses, roads, and water supplies at Los Antiguos village, 100 km SE of the volcano. The 250-ton annual crop of cherries was destroyed by the eruption. Snowfall was greater than normal, with the total precipitation of 410 mm, compared to the average of 218 mm. In some areas, 30-40 percent of sheep herds were killed. This was from eating ash covered grass, and the weight of ash of the back of some animals prevented them from standing up. There was a fast recovery of orchid crops after 2 years, but hundreds of sheep farms were abandoned in Santa Cruz province of Argentina.

Causes of the eruption
The eruption of Hudson volcano was caused by rising basaltic magma, erupted during the first phase, mixing with trachyandesite magma stored at a depth of 2-3 km. An increase in volume and gas release associated with mixing between basalt and trachyandesite magma may have triggered the paroxysmal eruption at Hudson on 12th August 1991.

Eruption 6700 Years Ago
An eruption of Hudson volcano 6700 years ago produced ashfall over large areas of southern Chile and Argentina. This eruption may have produced the current caldera.

Hudson Volcano Eruptions

2011, 1991, 1971, 1891, 1740 ± 150, 860 AD ± 100, 390 AD ± 150, 120 BC ± 200, 790 BC ± 75, 1890 BC?, 2250 BC, 3890 BC ± 500, 4750 BC?, 4960 BC ± 150, 8010 BC?