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Recent geo-physical studies have re-dimensioned the
importance of these systems by giving more
importance to the Ibleo-Maltese fault, regarding the
evolution of Etna’s magma. This fault dislocates the
lower eastern section of Etna's massif by forming a
series of distensive structures emphasised by
escarpment, faults and steep slopes with a NNW-SSE
orientation. The eastern section of the volcano is
limited northwards by the “Pernicana fault”
in an E-W direction.
The first signs of volcanic activity around Etna
occur at the base of the volcano and form the
splendid “Ciclope Coast” gushes and the
pillow lava along the cliff of Acicastello, but also
the basalt columns gushing on the river terrace of
Simeto, extending from Paternň to Adrano. The
studies on the composition of this lava highlights
that we are dealing with Tholeiites, i.e. magma that
is similar, even if with differences, to that
produced in areas where the earth mantle is
characterised by high levels of partial fusion of
great distensive activity, which is typical of the
oceanic ridges and islands. Tholeiites form a fairly
limited percentage of products from the area around
Etna and were produced from fissural eruptions,
often under water and on several occasions starting
circa 500,000 years ago. They are in fact the oldest
of Etna's products.
Following the first “Tholeiitic" period, the
eruptions began in the central apparatus of real,
exposed volcanoes. The products erupted during this
second period present a marked chemical difference
with the tholeiites. The lava is “alkaline”,
defined by scientists with exotic names such as
Hawaiiti or Mugeariti and even Benmoreiti. This
series of names also includes the most known, but
little present on Etna, basalts. The alkaline
products form the great mass of Mount Etna and still
erupt today. The distinctions between the terms are
carried out by means of percentage ratios of certain
oxides and in particular SiO2 and K2O+Na2O which are
considered indicative of the magma genesis. In
reality, the differences in terms used are very few.
For example the paragenesis, or rather the
collection of minerals present in the lava is almost
the same and composed of plagioclase, pyroxene, iron
titanium oxide and olivine.
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