Novarupta

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Novarupta
Novaruptas lava dome

Novaruptas lava dome
height 841  m
location in southwest Alaska
Mountains Aleutian Islands
Coordinates 58 ° 16 ′ 0 ″  N , 155 ° 9 ′ 24 ″  W Coordinates: 58 ° 16 ′ 0 ″  N , 155 ° 9 ′ 24 ″  W
Novarupta (Alaska)
Novarupta
Type Stratovolcano
Age of the rock 1.1 million years
Last eruption 1912

The Novarupta is a volcanic caldera in Katmai National Park in the Aleutian Range in Alaska . This collapse basin was formed in 1912 as a result of one of the largest volcanic explosions of modern times.

Discovery story

Aleutian chain

The Novarupta volcano erupted in 1912 with a devastating explosion, but at the time it was attributed to the Katmai volcano . Its crest had collapsed as a result of the emptying of the magma chamber shared by both volcanoes. Only in 1950 with a re-examination of the area by the Geological Survey of the United States, United States Geological Survey , it became clear that not the Mount Katmai, but a previously unknown volcano had erupted, the remains of the Valley of Ten Thousand Smokes , so the valley which formed ten thousand columns of smoke. The mountain itself was no longer there as a result of the explosion and the collapse of the caldera chamber . In order to protect the valley with its numerous fumaroles and solfataras , the area around Mount Katmai and the Valley of Ten Thousand Smokes was declared a national monument . On December 2, 1980, the area was declared a national park by the Alaska National Interest Lands Conservation Act .

Outbreak of 1912

The largest volcanic explosion of the 20th century occurred between June 6th and 8th, 1912. During the 60-hour eruption, 13 to 15 km³ of magma were released, which corresponds to level 6 on the volcanic explosiveness index . This amount of magma caused more than 17 km³ of fly ash and around 11 km³ of ash tufa . The eruption of such a mass of magma led to the formation of a 2 km wide funnel-shaped opening and the collapse of the top of Mount Katmai, which shared the same magma chamber with the Novarupta. As a result, a 600 m deep, 3 km × 4 km wide, kettle-shaped caldera formed. The eruption ended with the extrusion (pushing out) of a lava dome that clogged the chimney. The cup-shaped caldera with the (1950) 90 m high and 360 m wide lava dome is called Novarupta .

During the eruption, pyroclastic currents reached up to 13 miles into the upper Ukak River Valley. Even a few years later, some deposits were so hot that they could boil water. Because of the many fumaroles , this part of the valley has since been called the Valley of Ten Thousand Smokes . During the eruption, about 65 km² of land was covered with volcanic ash and other volcanic material ( ignimbrite ). The volcanic deposits reached a thickness of up to 200 m. The ash rain also fell in nearby Kodiak and even in Vancouver ; It is reported that lit street lamps in Kodiak could no longer be seen from a distance of 2 m.

In contrast to the eruptions of Krakatau or Tambora , which claimed many thousands of lives, only a few people were harmed - as far as is known - during the eruption in the Katmai area, as the area was practically uninhabited.

Comparable outbreaks

The eruption of the Novaruptas was the only volcanic explosion in the 20th century that led to the formation of a caldera (collapse cauldron). Only the eruption of Mount Pinatubo in  1991 with an ejection volume of 11 km³ tephra was of a comparable magnitude (VEI 6), but did not lead to the formation of a caldera. At least two more powerful eruptions occurred in the 19th century: the eruption of Tambora in  1815 with 150 km³ (VEI 7, caldera formation) and the eruption of Krakatau in  1883 with 20 km³ of ejection (VEI 6, caldera formation).

See also

literature

Web links

Commons : Novarupta  - collection of images, videos and audio files

Footnotes

  1. ↑ Adrian Lobe: Novarupta volcano: When the abyss of hell opened up in Alaska. In: The time . June 6, 2012, accessed October 6, 2012 .
  2. ↑ H. Pichler, T. Pichler: Volcanic areas of the earth . Elsevier, Munich 2007, ISBN 978-3-8274-1475-5 , pp. 178-179 .