Transcript Volcanic Eruptions and Hazards

SUBJECT:CAUSES AND EFFECTS OF VOLCANO..
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PARTALA MAULIK
VIVEK VEKARIYA
(130870106115)
(130870106122)
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vent
cone
conduit
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magma chamber
A volcano is a
vent or 'chimney'
that connects
molten rock
(magma) from
within the Earth’s
crust to the
Earth's surface.
The volcano
includes the
surrounding cone
of erupted
material.
Majority of volcanoes are formed as the result of
plate boundary movement such as the Ring of
Fire. The Pacific Ring of Fire contains over ½ of
the world’s volcanoes.
Volcanoes can also form in
the middle of a plate.
These are known as
“hot spot” volcanoes
and form because
magma is able to reach
the surface due to a
weak/thin spot in the
lithosphere.
Examples: Hawaiian
volcanoes and
Yellowstone National
Park.
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Vent- the vent is
the opening from
which lava flows.
Dust, ash, and
rock particles can
also be thrown out
of the vent!
2. Crater-
the
top of the
volcano. It is
a funnel
shaped pit. It
is formed
when the
material
explodes out
of the vent!
3.
Caldera-A vast
depression at the top
of a volcanic cone,
formed when an
eruption substantially
empties the reservoir
of magma beneath the
cone's summit.
Eventually the summit
collapses inward,
creating a caldera.
4.
Volcanic Conduit-A
tube like passage
through which
magma travels
within a volcano.
5.
Magma Chamber
is a large
underground pool of
molten rock found
beneath the surface of
the Earth's crust. The
molten rock in such a
chamber is under
great pressure, and
given enough time,
that pressure can
gradually fracture the
rock around it creating
outlets for the magma.
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There are 3 types of Volcanoes:
Shield
Cinder Cone
Stratovolcano
Volcanoes are
classified by
how they form!
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Is wide and
somewhat flat.
It forms from an
effusive (quiet)
eruption of lava.
Lava flows out
quietly and for great
distances.
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Has tall, very
steep sides.
Has explosive
eruptions.
This eruption
produces a lot
of cinder and
ash.
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Forms from
explosive
eruptions.
Produce a lot of
lava and ash.
Has steep sides.
MOST COMMON
TYPE OF
VOLCANO!
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Pressure builds deep in the earth where the magma
is. Suddenly the gases escape and violently explode.
When magma reaches the surface, how easily it flows
depends on its viscosity (stickiness) and the amount of gas
(H2O, CO2, S) it has in it.
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EXPLOSIVE ERUPTIONS are the result of high levels of gas
and high viscosity (sticky) magma.
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EFFUSIVE (QUIET) ERUPTIONS are the result of low
amounts of gas and (or) low viscosity (runny) magma.
VEI measures how explosive an eruption is
based on the amount of material released!
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Explosive volcanic
eruptions can be
catastrophic
Erupt 10’s-1000’s km3 of
magma, rocks, and other
materials
Send ash clouds >15
miles into the
stratosphere
Have severe
environmental and
climatic effects such as
global cooling because
ash blocks sunlight from
reaching Earth’s surface
Mt. Redoubt
Above: Large eruption column and
ash cloud from an explosive eruption
at Mt Redoubt, Alaska
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Courtesy of www.swisseduc.ch
Pyroclastic flow
Lahars/Mud flows
Pyroclastic fall
Lava flow
Noxious Gas
Earthquakes
Direct
measurements of
pyroclastic flows are
extremely
dangerous!!!
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For example,
eruption of
Vesuvius in 79
AD destroyed
the city of
Pompeii
On August 24, 79AD Mount Vesuvius literally
blew its top, erupting tons of molten ash,
pumice and sulfuric gas miles into the
atmosphere. Pyroclastic flows flowed over
the city of Pompeii and surrounding areas.
Pyroclastic flows of poisonous gas and hot
volcanic debris engulfed the cities of
Pompeii, Herculaneum and Stabiae
suffocating the inhabitants and burying the
buildings.
The cities remained buried
and undiscovered for almost
1700 years until excavation
began in 1748. These
excavations continue today
and provide insight into life
during the Roman Empire.
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Naples
Vesuvius remains a
hazardous volcano
with heavily
populated flanks:
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Vesuvius
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Bay of
Naples
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Courtesy of www.swisseduc.ch
around 1.5 million
people live in the
city of Naples alone
Naples is situated
approx. 20 miles
from Vesuvius
Pyroclastic flows
can flow up to 60
miles from source!
Mt Peleé, Martinique (1902)
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An eruption of Mt Peleé in 1902 produced a
pyroclastic flow that destroyed the city of St.
Pierre. Over 29,000 people died!
before
after
Courtesy of www.swisseduc.ch
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Hot volcanic activity
can melt snow and ice
Melted water picks up
rock and debris forming
hot, fast moving mud
flows known as lahars.
Lahars are a mixture of
rocks, soil, boulders and
other debris and can be
very destructive.
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Collapses roofs
Brings down power lines
Kills plants
Contaminates water
supplies
– Respiratory hazard for
humans and animals
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Effusive eruptions are
characterized by outpourings
of lava on to the ground.
Hawaii
Courtesy of www.swisseduc.ch
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It is not just explosive volcanic activity that can
be hazardous. Effusive (lava) activity is also
dangerous.
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Iceland, January
23,1973.
Large fissure
eruption
threatened the
town of
Vestmannaeyjar.
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The lava flows caught
the inhabitants by
surprise
Before the eruption was
over, approximately
one-third of the town of
Vestmannaeyjer had
been destroyed
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However, the potential damage was reduced by
spraying seawater onto the advancing lava flows.
This caused them to slow and/or stop, or diverted them
away from the undamaged part of the town.
So….
How do we minimize the risk of active
volcanoes?
Volcano Observatories
are set up on all active
volcanoes that threaten
the human population.
These are designed to
monitor and potentially
to predict the eruptive
behavior of the volcano
in question.
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Seismicity
Deformation
Gas Output
These three things are
the most important
precursors to an
eruption.
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Earthquake activity commonly precedes an eruption
 Result of magma pushing up towards the surface
 Increase volume of material in the volcano shatters the
rock
 This causes earthquakes
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Tilltmeters can tell you when new material enters the magma
chamber.
A
B
Note the
presence of
earthquakes in
relation to the
deformation.
Often it is a
combination of
events that forewarns of an
eruption.
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Commonly gas output from a volcano increases or changes
composition before an eruption.
 As magma rises to the surface it releases (exsolves) much of
its gas content.
 This can be measured
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1,700 people living in the
valley below Lake Nyos in
northwestern Cameroon
mysteriously died on the
evening of August 26, 1986.
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Lake Nyos is a crater lake inside a dormant
volcano.
The lake had become laden with carbon
dioxide gas.
This gas had suddenly bubbled out of the
lake and asphyxiated nearly every living
being in the surrounding valley.
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A management plan has been
developed to remove gas from the
lake to prevent a further tragedy.
An artificial vent to the lake surface
was created with pipe.
Water is pumped from the bottom of
the lake to the surface through the
pipe, where it can degas.
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Volcanoes are extremely hazardous.
However, the volcano can be studied,
monitored and understood.
Each volcano is different, and offers a
unique set of dangers
Plans may be put into place to help
control potential damage.