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Eruptions of Mt. Vesuvius Mt Vesuvius and...
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Eruptions of Mt. Vesuvius
Eruptions of Mt. Vesuvius
Historical and Future(?)
Historical and Future(?)
Tragedies
Tragedies
CC 3.32, Lecture 3
CC 3.32, Lecture 3
Location of Mt. Vesuvius
Location of Mt. Vesuvius
Mt Vesuvius and Naples
Mt Vesuvius and Naples
Ruins of Pompeii
Ruins of Pompeii
79 AD Population: ~20,000
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Casts of Bodies in Pompeii
Casts of Bodies in Pompeii
1,150 bodies have been uncovered
79 AD Eruption of Vesuvius
79 AD Eruption of Vesuvius
��Vesuvius had not
Vesuvius had not
erupted violently in
erupted violently in
prior history
prior history
��Minor eruption in 217
Minor eruption in 217
BC (Plutarch)
BC (Plutarch)
Precursor Signs:
Precursor Signs:
��Earthquakes
Earthquakes
��Drying of wells and
Drying of wells and
springs in early
springs in early
August, 79 AD
August, 79 AD
79 AD Eruption of Vesuvius
79 AD Eruption of Vesuvius
��August 24 or 25
August 24 or 25
��Explosive eruption
Explosive eruption
that lasted 19 hours
that lasted 19 hours
��1 cubic m
ile of ash
1 cubic m
ile of ash
erupted
erupted
��Ash column was 20
Ash column was 20
miles high
miles high
��Winds blew southward
Winds blew southward
••10 feet of ash fell on
10 feet of ash fell on
Pompeii
Pompeii
79 AD Eruption of Vesuvius
79 AD Eruption of Vesuvius
by Pliny the Younger
by Pliny the Younger
��““The cloud was rising from a
The cloud was rising from a
mountain
mountain-- at such a distance
at such a distance
we couldn't tell which, but
we couldn't tell which, but
afterwards learned that it was
afterwards learned that it was
Vesuvius. I can best describe
Vesuvius. I can best describe
its shape by likening it to a
its shape by likening it to a
pine tree. It rose into the sky
pine tree. It rose into the sky
on a very long "trunk" from
on a very long "trunk" from
which spread some
which spread some
"branches." I imagine it had
"branches." I imagine it had
been raised by a sudden
been raised by a sudden
blast, which then weakened,
blast, which then weakened,
leaving the cloud unsupported
leaving the cloud unsupported
so that its own weight caused
so that its own weight caused
it to spread sideways. Some
it to spread sideways. Some
of the cloud was white, in
of the cloud was white, in
other parts there were dark
other parts there were dark
patches of dirt and ash.
patches of dirt and ash. ””
Vesuvius
1944
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79 AD Eruption of Vesuvius
79 AD Eruption of Vesuvius
by Pliny the Younger
by Pliny the Younger
��““Ash was falling onto the ships
Ash was falling onto the ships
now, darker and denser the
now, darker and denser the
closer they went. Now it was
closer they went. Now it was
bits of pumice, and rocks that
bits of pumice, and rocks that
were blackened and burned
were blackened and burned
and shattered by the fire
and shattered by the fire””
��““The ground outside his room
The ground outside his room
rose so high with the m
ixture
rose so high with the m
ixture
of ash and stones that if he
of ash and stones that if he
had spent any m
ore time there
had spent any m
ore time there
escape would have been
escape would have been
impossible
impossible……They tied pillows
They tied pillows
on top of their heads as
on top of their heads as
protection against the shower
protection against the shower
of rock. It was daylight now
of rock. It was daylight now
elsewhere in the world, but
elsewhere in the world, but
there the darkness was darker
there the darkness was darker
and thicker than any night .
and thicker than any night . ””
Plinian
PlinianEruptions
Eruptions
��Large, explosive events
Large, explosive events
��Eject enorm
ous columns of
Eject enorm
ous columns of
ash (>11km tall)
ash (>11km tall)
��Ejecta
Ejecta
is carried by the
is carried by the
prevailing winds
prevailing winds
��A few hours to a few days
A few hours to a few days
��Mt. Vesuvius
Mt. Vesuvius
Mt. St. Helens
Mt. St. Helens
Mt.
Mt. Pinotubo
Pinotubo
Plinian
PlinianAnimations
Animations
��http://
http://www.sci.sdsu.edu
www.sci.sdsu.edu/volcano/
/volcano/
��http://
http://www.sci.sdsu.edu/volcano/fly
www.sci.sdsu.edu/volcano/fly
by.m
ov
by.m
ov
79 AD Eruption of Vesuvius
79 AD Eruption of Vesuvius
��10 feet of ash fell on
10 feet of ash fell on
Pompeii
Pompeii
••Winds m
ust have been
Winds m
ust have been
blowing southward
blowing southward
during the eruption
during the eruption
��38% of the 1,150 bodies
38% of the 1,150 bodies
recovered in Pompeii lie
recovered in Pompeii lie
within the ash fall
within the ash fall
••Mostly crushed under
Mostly crushed under
collapsing roofs
collapsing roofs
••Weight of pumice ash
Weight of pumice ash
has been estimated at
has been estimated at
476 lb/ft
476 lb/ft22
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Volcanic Strata at Pompeii
Volcanic Strata at Pompeii
79 AD Eruption of Vesuvius
79 AD Eruption of Vesuvius
��Ash fall was followed by a
Ash fall was followed by a
series of
series of pyroclastic
pyroclasticsurges
surges
on the next morning
on the next morning
••Ground
Ground-- hugging, directed
hugging, directed
explosions
explosions
••Super
Super --heated gasses and
heated gasses and
pyroclastic
pyroclasticdebris
debris
••Asphyxiated the remaining
Asphyxiated the remaining
people in Pompeii
people in Pompeii
��62% of the bodies in
62% of the bodies in
Pompeii lie within the
Pompeii lie within the
surge deposits
surge deposits
��Half of these were on the
Half of these were on the
streets and half were
streets and half were
indoors
indoors
Types of
Types of Pyroclastic
PyroclasticFlows
Flows
��Pyroclastic
PyroclasticFlow
Flow: A hot, chaotic avalanche of
: A hot, chaotic avalanche of
pumice, ash, and gasses.
pumice, ash, and gasses. Pyroclastic
Pyroclasticflows can
flows can
move at high speeds along the ground and pass
move at high speeds along the ground and pass
over substantial obstacles. Their distribution is,
over substantial obstacles. Their distribution is,
however, strongly controlled by topography.
however, strongly controlled by topography.
��Pyroclastic
PyroclasticSurge
Surge: A turbulent cloud of volcanic
: A turbulent cloud of volcanic
ash and hot gasses, which hugs the ground and
ash and hot gasses, which hugs the ground and
travels at speeds often exceeding 100 km per
travels at speeds often exceeding 100 km per
hour. Surge deposits are m
ore widely distributed
hour. Surge deposits are m
ore widely distributed
than
than pyroclastic
pyroclasticflow deposits, although not as
flow deposits, although not as
widespread as air
widespread as air--fall pumice layers.
fall pumice layers.
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Types of
Types of Pyroclastic
PyroclasticFlows
Flows
Pyroclastic
PyroclasticFlows at Pompeii
Flows at Pompeii
��The deposits reveal that after the
The deposits reveal that after the Plinean
Plinean
eruption, Pompeii was hit first by a
eruption, Pompeii was hit first by a pyroclastic
pyroclastic
surge
surge, leaving a deposit of 10 to 20 cm, closely
, leaving a deposit of 10 to 20 cm, closely
followed by a
followed by a pyroclastic
pyroclasticflow
flowthat left a deposit
that left a deposit
varying in thickness up to 200 cm
varying in thickness up to 200 cm
��Shortly thereafter, there was a
Shortly thereafter, there was a second
second pyroclastic
pyroclastic
surge
surgeleaving a deposit of 10 to 20 cm, rich in
leaving a deposit of 10 to 20 cm, rich in
fragments of limestone and dense volcanic rocks.
fragments of limestone and dense volcanic rocks.
Pel
Pel ééananEruptions
Eruptions
��Explosive outbursts that
Explosive outbursts that
generate
generate pyroclastic
pyroclasticflows
flows
��Eruption columns are short
Eruption columns are short
��First described from Mt
First described from Mt
Pelee
Peleeon Martinique
on Martinique
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Eruptive History of Vesuvius
Eruptive History of Vesuvius
History of
History of
Vesuvius
Vesuvius
Phlegrean
PhlegreanFields
Fields
��13 km caldera
13 km caldera
��Form
ed 35,000 years
Form
ed 35,000 years
ago
ago
��Eruption of 80km
Eruption of 80km
3
3 of
of
ash
ash
��Two historic eruptions
Two historic eruptions
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Phlegrean
PhlegreanFields Caldera
Fields Caldera
Monte
Monte Nuovo
Nuovo
��Form
ed during an
Form
ed during an
eruption in one
eruption in one
week, beginning on
week, beginning on
September 28,
September 28,
1538
1538
Solfatara
Solfatara
��Volcano form
ed 4000
Volcano form
ed 4000
years ago
years ago
��Last erupted in 1198
Last erupted in 1198
��Boiling m
ud and
Boiling m
ud and
sulfurous vapors
sulfurous vapors
Bradyseism
Bradyseism
��Gradual change in ground elevation due to
Gradual change in ground elevation due to
filling or emptying of a m
agma chamber
filling or emptying of a m
agma chamber
��Between 1968 and 1972, the
Between 1968 and 1972, the Phlegrean
Phlegrean
Fields rose 1.7 m
eters
Fields rose 1.7 m
eters
��Between 1982 and 1984, the
Between 1982 and 1984, the Phlegrean
Phlegrean
Fields rose 1.8 m
eters
Fields rose 1.8 m
eters
��Region still active
Region still active
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Current
Current
Threat?
Threat?
Naples Population
~1 m
illion people