Lava dome of Novarupta

The Novarupta is a Vulkancaldera in Katmai National Park in the Aleutian Island chain in Alaska. This was formed in 1912 as a result of the largest volcanic explosions in modern times.

Discovery history

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

Outbreak of 1912

The largest volcanic eruption of the 20th century occurred between June 6 and 8, 1912. During the outbreak lasting about 60 hours 13 to 15 km3 of magma were released, which corresponds to the index of the Vulkanexplosivität Level 6. This amount of magma caused more than 17 km3 of fly ash and about 11 km3 Aschetuff. The eruption of such a magma quantity led to the formation of a 2 km wide funnel-shaped opening and the collapse of the summit of Mount Katmai, who shared with the Novarupta the same magma chamber. As a result, a 600 m deep 3 km × 4 km wide cauldron-shaped caldera formed from. The eruption ended with the extrusion ( pushing out ) of a lava dome, which clogged the vent. The cauldron-shaped caldera with the (1950 ) 90 m high and 360 m wide lava dome is called Novarupta.

During the eruption, pyroclastic flows reached up to 21 km in the upper Ukak River Valley. Even some years later, some deposits were so hot that you could so bring water to a boil. Because of the many fumaroles this part of the valley Valley of Ten Thousand Smokes since then is called. When the eruption about 65 km2 of land were covered with volcanic ash and other volcanic material. The volcanogenic deposits reached up to 200 m thick. The ash fall was also reflected in the nearby Kodiak and even in Vancouver; It is reported that while in Kodiak burning street lights were no longer visible at a distance of 2 m.

In contrast to the eruption of Krakatoa or Tambora, which claimed thousands of lives, were - is as far as known - the outbreak in the Katmai area, few people injured as the area was virtually uninhabited and still is today.

Similar outbreaks

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