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Earth of fire

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

The eruption of 1951, preceded by a strong earthquake, starts on a crack, south of Pico do Fogo, on June 12 , where it builds cinder cones called Monte Orlando and Monte Rendall .
Following the spread of the feeder dyke to the northwest, others fissure vents open this time on the other side of Pico, and finally to the cone Monte Preto de Cima .


Magma storage and ascent of historic and prehistor-copie-2
Fogo - location of flows and cinder cones of eruption of 1951 - after Brum da Silveira et al. (1997) and Torres et al. (1997) / in Hildner ref. in sources.

The eruption, of Strombolian to Hawaiian type, will continue until August 21. It will feed voluminous lava flows, which will destroy crops in Cha das Caldeiras . Castings issued on the south side descend to the coast, to stop only 100 meters from the beach and destroy the Cova Martinho village. The volume of lava emitted is 11 million m³.
 
17° - fogo - 6 - CHB-copie-1              Fogo - north side of Pico and lava 1951 - photo © Carole and Frederic Hardy

51 - Fogo - 4 - CHB               Fogo - north side of Pico - cinder cone 1951 - © photo Carole and Frederic Hardy

51 - Fogo - 3 - CHB            Fogo - Cha das Caldeiras - hornito - photo © Carole and Frederic Hardy

The Portuguese geographer Orlando Ribeiro will see the eruption and there devoted a study : A Ilha de Fogo e as Suas Erupções . In tribute , we called Monte Orlando one of the cinder cone formed during this eruption .


51.07.09 Mt Orlando - CEG
Fogo - 9th of juillet 1951/4 ° week of the eruption - the Monte Orlando smoke - in the background , the Pico do Fogo - © CEG / site of Orlando Ribeiro .

51 - Fogo - 12 - CHBFogo - lava of the 1951 eruption - "pressure ridge " on a lava tunnel - photo © Carole and Frederic Hardy
51 - Fogo - 19 - CHB                  
Fogo - 
lava of the 1951 eruption - photo © Carole and Frederic Hardy
51 - Fogo - 17 - CHB                      Fogo - lava 1951 - photo © Carole and Frederic Hardy

Rocks for this eruption are basanites to tephrites, with a MgO percentage ranging from 5.0 to 8.2 wt % . The low concentrations of MgO , Ni and Cr indicate that these rocks do not represent a primitive magma . There is also an abundance of amphibole megacrysts xénolithe, particularly in the late phase of eruption.
The 1951 eruption is characterized by fractional crystallization 17-22 km . in the upper mantle, before that takes up the eruptive phenomenon, and a short stagnation of magma during its ascent at 9-13 km in the crust.
The plumbing model is completed by a large intrusive body in the crust .

 

Magma storage and ascent of historic and prehistor-copie-3

               Fogo - plumbing system in 1951 - after Pim et al. / Hildner in ref. in sources.

Sources:
- Global Volcanism Program -
Fogo

 - Magma storage and ascent of historic and prehistoric eruptions of Fogo
Cape Verde Islands: A barometric , Petrologic and geochemical approach - by Elliot Hildner / University of Bremen

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