Active volcanoes / Aktive vulkaner:
Hudson, Chile    (ikke klart enda)

Cerro Hudson, August 23, 1991
Photo: USGS

The ice-filled, 10-km-wide caldera of the remote Cerro Hudson volcano was not recognized until its first 20th-century
eruption in 1971. Cerro Hudson is the southernmost volcano in the Chilean Andes related to subduction of the
Nazca plate beneath the South American plate.

The massive, 1905-m-high Cerro Hudson covers an area of 300 sq km. The compound caldera is drained through
a breach on its NW rim, which has been the source of mudflows down the Río de Los Huemeles.
Two cinder cones occur north of the volcano and others occupy the SW and SE flanks.

Hudson has been the source of several major Holocene explosive eruptions.
An eruption about 6700 years ago was one of the largest known in the southern Andes during the Holocene;
another eruption about 3600 years ago also produced more than 10 cu km of tephra.
An eruption in 1991 was Chile's second largest of the 20th century and formed a new 800-m-wide crater in
the SW part of the caldera.

Wednesday, November 16th, 2011
The volcano's activity level is maintained at: LEVEL 4 - Yellow:
Significant variations monitoring parameters indicate that the activity can evolve to an eruptive event in days / weeks.
If the Volcanic activity continues with the current trend, will lower the alert level to Level 3 - YELLOW in the next report.

Based on the analysis of information obtained through monitoring and surveillance equipment for the Hudson volcano, SERNAGEOMIN and OVDAS reported for this period as follows: -During this period there were 988 seismic events,
of which 862 are associated with rock fracturing (VT) and 124 correspond to events associated with the fluid
dynamics inside the volcanic conduit type long period (LP). -registered events have magnitudes calculated based
on the duration of the signal (MD), lower than 1.1,

Sunday, November 6th, 2011
The Volcano Observatory of the Southern Andes (OVDAS), National Service of Geology and Mining
(SERNAGEOMIN) - reports on the activity of Hudson volcano in the last 24 hours
The level of volcanic alert remains in YELLOW - LEVEL 4: Changes in the volcano's behavior -
Significant monitoring parameters indicate that the activity may evolve into an eruptive event in Days / Weeks

Thursday, November 3rd, 2011

Nearly 150 evacuees on Wednesday will be able to return home, after the government determined to lift the state
of red alert due to an eruptive activity of the Hudson volcano.

The National Emergency Office switched the red alert level to yellow noting that evacuated residents,
within the perimeter of 45 km near the Hudson volcano, located in the southern region of Aysen,
about 2,000 miles away from the capital, could return to their homes.

Nevertheless, authorities warned about the characteristics of the volcano, considered among the most explosive of Chile, and also called for further surveillance.

October 26th, 2011

Hudson volcano erupted from three craters.

Authorities issued a warning that an explotion could be around the corner within few days.
People withing its range were immideately evacuated.

That followed the increased seismicity that was detected during 25-26 October. At 1908 on 25 October an M 4.6
volcano-tectonic earthquake occurred at a depth of 19 km, followed by a seismic swarm starting at 2149.
More than 100 events, with depths ranging from 15 to 25 km, were recorded through the next day;
12 of the events were M 3, and three events were M 4.

Scientists aboard an overflight on 26 October observed a white plume with some ash content that rose 1.5 km
and lahars in Rio Huemul, to the W. The Alert Level was raised to Level 5 - Red.
A very low-frequency M 4.3 earthquake occurred that same day at a depth of 15 km.

See comments to the ongoing swarm of quakes on El Hierro, where they say that an eruption is
not yet to happen, as quakes are too deep - about 20-.25km.


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