Download Explosive and effusive eruptions

Explosive and effusive eruptions
THERE ARE TWO PREDOMINANT TYPES
OF VOLCANIC ERUPTIONS:
Effusive eruptions
when magma rises through the
surface and flows out of the
volcano as a viscous liquid
called lava.
Explosive eruptions when
magma is torn apart as it rises
and reaches the surface in
pieces known as pyroclasts.
The explosive eruptions
Explosive eruptions are violent emissions
of fragmented magma caused by
the actions of gases contained in it
and also by the effect
of the vaporization of the water
(that has external origin),
which comes into contact
with the magma.
The effusive eruption
An eruption dominated by the outpouring of the lava onto the ground
is often defined as an effusive eruption.
Lava flows generated by effusive eruptions change its
shape, thickness, length and width depending on the type
of lava erupted.
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The Precautions
The fall of volcanic ash represents a health
risk. Prolonged exposure can be dangerous
and, for this reason, we should take some
precautions to reduce problems.
1. Outdoors, wear a mask and glasses to protect
against dust
2. In case of eye contact avoid rub; wash them with water
3. Stay indoors with the closed windows
4. Pets should be kept at home
5. Drive with particular caution
6. Don’t eat fruit and vegetables covered with ash
without accurate washing
People exposed to falling
ash or living in the dusty
environment after
an ash fall
can suffer different
problems.
Respiratory problems
such as nose and throat irritation,
coughing, bronchitis-like illness
and discomfort while breathing.
The emission of Radon is also important.
It is considered as a significant air contaminant.
According to a report made by the EPA
(Environmental Protection Agency)
radon causes lung cancer.
Dry volcanic ash can stick to a moist human eye and the tiny ash particles
quickly cause eye irritation. This problem is most severe among people who
wear contact lenses; but there are also some skin irritations reported by
people in ashfall areas.
Depending on where the volcano is located, the effects will be
felt globally or at least by a whole hemisphere.
Large areas can be devastated by
• pyroclastic flow deposits
• volcanic gases, above all sulphur
gases being particularly important.
This gas is converted into sulphuric
acid aerosols in the stratosphere and
layers of aerosol can cover the global
atmosphere within a few weeks to months
or also it can cover the atmosphere for several
years. One of the most important effects
is the temporary reductions in light levels.
The explosive eruptions’ damages
The effusive eruptions’ damages
Effusive eruptions rarely kill anyone because they move slowly. People can
usually be evacuated during an effusive eruption. Usually, the most dangerous
problem is the destruction of roads and buildings.
The mount Aetna
Mount Aetna is one of the most
active volcanoes in the world.
-Volcanic activity first took place
at Aetna about 500,000 years ago,
with eruptions occurring beneath
the sea off the ancient coastline
of Sicily.
-From about 35,000 to 15,000
years ago, Aetna experienced some
highly explosive eruptions,
generating large pyroclastic flows,
which left extensive ignimbrite deposits.
-Aetna's most destructive eruption
started on 11 March 1669.
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-The first eruptions are to be found in the basalt
columns of Acitrezza and Sant’Anastasia and pillows
in Acicastello.
A second series of eruptions, this time type alkalibasalt, is held between 200 and 100 thousand years
ago, giving shape to the so-called Monte Calanna, the
main prehistoric volcanic cones.
-The eruption of Etna in 1669, which is
considered the most
devastating period of history, it destroyed
and buried dozens of villages coming down
to the sea at the western districts of Catania.
The mount vesuvius
Mount Vesuvius is a stratovolcano
in the Gulf of Naples, Italy,
about 9 km east of Naples and
a short distance from the shore.
-Vesuvius is a distinctive "humpbacked" mountain, consisting of a large cone(Gran Cono) partially
encircled by the steep rim of a summit caldera.
-Vesuvius was formed as a result of the collision of two tectonic plates, the African and the Eurasian.
In 1631, different earthquakes occurred. They caused
numerous bulges of the ground, which consequently provoked
many eruptions, such as its last one in 1944, demonstrating the
real activity of Vesuvius and denying his quiescence.
-
The eruption of Vesuvius in 79 A.D. is the major
eruption of Mount Vesuvius occurred in historical times.
The eruption, which has radically altered the morphology
of the volcano, caused the destruction of the cities of
Herculaneum, Pompeii and Stabiae
Marta Barbagallo
Federica Crisafulli
Giulia Gallo
Laura Patanè