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Earth of fire

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

Publié par Bernard Duyck
Publié dans : #Actualités volcaniques

Among the few lava lakes present on the planet, Nyiragongo ( DRC), Erta Ale (Ethiopia) , Kilauea (Hawaii) and Erebus (Antarctica) , the latter holds a special place .

Its phonolitic magma is 100 times more viscous than basaltic magma of Kilauea or Erta Ale

This lava lake , active since the 70s, was analyzed by volcanologists for over 40 years. During the first decades , scientists had only a few weeks in summer to gather measurements and valuable comments . The installation of permanent equipment have allowed monitoring throughout the year .

Erebus - photo MEVO 11.2012

Erebus - photo MEVO 11.2012

The breath of the sleeping dragon :

This ongoing monitoring revealed the regularity of  the " breath of Erebus ."

There a few years ago , Oppenheimer, a volcanologist at the University of Cambridge , has measured the plume of gas still present volcano : the total amount of gas , composed almost equally of carbon dioxide and water with added a little sulfur dioxide and HCl , follows a cycle of 10 minutes , with both quantitative and qualitative changes .

The analysis of several hundreds of thousands of images allowed to deduce the motion vectors surface , and the average surface speed of the lava lake . Since 2004, and although the apparent surface of the lava lake has decreased by a factor 4, the pulsatile behavior remained constant , showing cycles of surface speed between 5 and 18 minutes. The average surface speed is from 3 to 20 cm / sec .

In addition, it is noticed that the surface of the lake rises and down 2 to 3 meters , in conjunction with the cycle gas ten minutes.

Erebus - continuous degassing - photo Nat Geo / Carsten Peter

Erebus - continuous degassing - photo Nat Geo / Carsten Peter

Erebus - 01.12.2012 - the lava lake - photo MEVO

Erebus - 01.12.2012 - the lava lake - photo MEVO

Eructations and plumbing system of the volcano :

Differentiation between this " breathing " and " burping " of the volcano during eruptions allows a better understanding of the plumbing system of Erebus .

During eruptions , large gas bubbles emerge and burst into the lava lake , making splash on the slopes ... some lava bombs up to the size of a bus. These two behaviors are not coupled , and scientists believe that the gas bubbles causing the projection of bombs rise from a greater depth . They have indeed noted that the cycles of gas continue even when eruptions do sharply lower the level of the lava lake .

Erebus - Clive Oppenheimer near a large anorthoclase phonolite bomb - December 2013 - photo MEVO

Erebus - Clive Oppenheimer near a large anorthoclase phonolite bomb - December 2013 - photo MEVO

Erebus plumbing system - doc. MEVO

Erebus plumbing system - doc. MEVO

Sources :

- Live Science - Antarctic lava lake huffs and puffs like a sleeping dragon - link

- ScienceDirect / Earth and Planetary Science Letters - Decadal persistence of cycles in lava lake motion at Erebus volcano, Antarctica by Nial Peters ,CliveOppenheimer, Philip Kyle, Nick Kingsbury / 03.2014

- MEVO - Mount Erebus Volcano Observatory - link

- Mantle to surface degassing of alkalic magmas at Erebus volcano, Antarctica - By Clive Oppenheimer & al. - link

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