Actualité volcanique, Articles 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
.
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.
Fogo - north side of Pico and lava 1951 - photo © Carole and Frederic
Hardy
Fogo - north side of Pico - cinder cone 1951 - © photo Carole and Frederic Hardy
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 .
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 .
Fogo - lava of the 1951 eruption - "pressure
ridge " on a lava tunnel - photo © Carole and Frederic Hardy
Fogo - lava of the 1951 eruption - photo © Carole
and Frederic Hardy
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 .
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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