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Earth of fire

Actualité volcanique, Articles de fond sur étude de volcan, tectonique, récits et photos de voyage

Publié le par Bernard Duyck
Publié dans : #Actualités volcaniques
Öreafajökull - the cauldron on 10.12.2017 / 12h34 - Landsat 8 image - IMO

Öreafajökull - the cauldron on 10.12.2017 / 12h34 - Landsat 8 image - IMO

The University of Iceland and the Icelandic Met Office have obtained in the previous weeks an agreement with NASA and the USGS for the Landsat 8 satellite to continue to acquire images of the volcano, whereas in principle they are not not in December and January, when the solar angle is low.

A comparison of the images taken between October 17 and December 10, 2017 shows that the cauldron has expanded and that the surface of the glacier has a larger or more visible pattern of cracks (Icelandic Met Office & University of Iceland)

Öraefajökull cauldron & crevasses - Landsat 8 images from 17.11.2017 & 10.12.2017 / Nasa & USGS - one click to enlarge

Öraefajökull cauldron & crevasses - Landsat 8 images from 17.11.2017 & 10.12.2017 / Nasa & USGS - one click to enlarge

Magnus Tumi Guðmundsson, a professor of geology, told to Mbl.is on 12 December that, following the study of photos taken the previous day, the slump of the cauldron slowed down and only increased by around 2-3 meters since last flyover two weeks ago.

According to Guðmundsson, the geothermal heat drops, or has already done so before the cauldron was spotted. The power of the geothermal flow in the glacial cauldron is 100-150 MW, which corresponds to that of the Bárðarbunga cauldrons, and given the rapidity of subsidence, it is likely that the water that has accumulated in underneath for weeks or months has infiltrated. He adds, however, that it is impossible to exclude the possibility of a volcanic eruption in the near future, and that the interpretation of events at the Öræfajökull remains the responsibility of the scientists in charge. (Iceland Review)

Note: from 4 to 10 December, the IMO recorded more than 100 earthquakes at Öræfajökull.

The Öerafajökull cauldron and crevasses during the 11.12.2017 overview by RAX / in Iceland Review

The Öerafajökull cauldron and crevasses during the 11.12.2017 overview by RAX / in Iceland Review

An interesting study of the volcano and its ice cover in 2014 is available on the Institute of Earth Science website, entitled "Removing the ice cap of Öræfajökull central volcano, SE-Iceland: Mapping and interpretation of bedrock topography, ice volumes, subglacial troughs ".

Ice Cover and Outlet Glaciers of the Öraefajökull - Doc. Removing the ice cap of Öræfajökull central volcano, SE-Iceland: Mapping and interpretation of bedrock topography, ice volumes, subglacial troughs and implications for hazards assessments Eyjólfur Magnússon, Finnur Pálsson, Helgi Björnsson and Snævarr Guðmundsson - 2014

Ice Cover and Outlet Glaciers of the Öraefajökull - Doc. Removing the ice cap of Öræfajökull central volcano, SE-Iceland: Mapping and interpretation of bedrock topography, ice volumes, subglacial troughs and implications for hazards assessments Eyjólfur Magnússon, Finnur Pálsson, Helgi Björnsson and Snævarr Guðmundsson - 2014

The Öræfajökull bedrock and ice cover study has established a DEM / digital surface elevation model based on radio echo sounding and LiDAR measurements.

In the center of the Öræfajökull, there is a 14 km² caldera, containing a volume of ice of 4.3 km³, which reaches a thickness of 540 meters. Most of the caldera's meltwater is drained to the east and the Kvíá River, the rest to the west and the Virkisá River. The floor of the caldera is generally soft, with the exception of a mouth, under 400 meters of ice, near the line of separation of waters between rivers.

A second separate caldera appears to appear within the main caldera, and measures 6 km² and 150 meters deep.

Subglacial topography also involves the presence of an old, heavily eroded caldera north of the volcano's summit, the Hvannadalshnúkur, culminating at 2110 m a.s.l, similar in size to the main caldera present today.

 Perspective view of SSW of the Öraefajökull Ice Cap (above) and bedrock (below). In the center, the replacement of the icecap by lakes in large depressions. - doc. Removing the ice cap of Öræfajökull central volcano, SE-Iceland: Mapping and interpretation of bedrock topography, ice volumes, subglacial troughs and implications for hazards assessments Eyjólfur Magnússon, Finnur Pálsson, Helgi Björnsson and Snævarr Guðmundsson - 2014

 Perspective view of SSW of the Öraefajökull Ice Cap (above) and bedrock (below). In the center, the replacement of the icecap by lakes in large depressions. - doc. Removing the ice cap of Öræfajökull central volcano, SE-Iceland: Mapping and interpretation of bedrock topography, ice volumes, subglacial troughs and implications for hazards assessments Eyjólfur Magnússon, Finnur Pálsson, Helgi Björnsson and Snævarr Guðmundsson - 2014

Topography of the bedrock of the central part of the Öraefajökull, with the current caldera (dashed red line), a potential intraludate formation (dashed yellow line) and a possible old eroded caldera (dotted green line) - - doc. Removing the ice cap of Öræfajökull central volcano, SE-Iceland: Mapping and interpretation of bedrock topography, ice volumes, subglacial troughs and implications for hazards assessments Eyjólfur Magnússon, Finnur Pálsson, Helgi Björnsson and Snævarr Guðmundsson - 2014

Topography of the bedrock of the central part of the Öraefajökull, with the current caldera (dashed red line), a potential intraludate formation (dashed yellow line) and a possible old eroded caldera (dotted green line) - - doc. Removing the ice cap of Öræfajökull central volcano, SE-Iceland: Mapping and interpretation of bedrock topography, ice volumes, subglacial troughs and implications for hazards assessments Eyjólfur Magnússon, Finnur Pálsson, Helgi Björnsson and Snævarr Guðmundsson - 2014

The Öræfajökull outlet glaciers, which are 550 meters thick in places, have dug the substrate up to 220 meters below the present sea level, at an estimated time of more than 4,000 years, an excavation during the Little Ice Age.

Assuming global warming, marginal lakes will form as glacial retreat in the coming decades, varying from one outlet to another. A persistent temperature rise of 0.5 to 1 ° C could result in the complete disappearance of the lowest outlets, while outlets at higher elevations, such as Kvíárjökull, could survive these adverse weather conditions, and leave 1 / 4 meltwater in the caldera.

 

Only the behavior of the volcano and the climate future will give us precise answers to these estimates.

 

Sources:

- IMO, University of Iceland, Iceland Review, Nasa & USGS / Landsat 8

- Removing the ice cap of Öræfajökull central volcano, SE-Iceland: Mapping and interpretation of bedrock topography, ice volumes, subglacial troughs and implications for haziness assessments Eyjólfur Magnússon, Finnur Pálsson, Helgi Björnsson and Snævarr Guðmundsson - 2014 - link

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