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By: Zaisha Brothers & Jen Cleveland
Volcanoes, are a mountain or hill formed by the
accumulation of materials erupted through one or more
openings in the earth’s or other planets surfaces. Most
volcanoes have steep sides, but some can be gently
sloping mountains or even flat tablelands, plateaus, or
plains. The volcanoes above sea level are the best known,
but the vast majority of the world's volcanoes lie beneath
the sea, formed along the global oceanic ridge systems
that crisscross the deep ocean floor.
Formation
•
All volcanoes are formed by the accumulation of magma; molten rock that forms
below the earth's surface. Magma can erupt through one or more volcanic vents,
which can be a single opening, a cluster of openings, or a long crack, It forms deep
within the earth, generally within the upper part of the mantle; one of the layers of
the earth’s crust. High temperatures and pressures are needed to form magma. The
solid mantle or crustal rock must be melted under conditions, commonly to reach
depths of 80 to 100 km below the earth’s surface. Once tiny droplets of magma are
formed, they begin to rise because the magma is less dense than the solid rock
surrounding it. For magma to rise is, it generally moves upward toward lower
pressure regions, squeezing into spaces between minerals within the solid rock.
When individual magma droplets rise, they join to form larger blobs and move toward
the earths surface. The larger the rising blob of magma, the easier it is for it to move.
Rising magma does not reach the surface in a steady manner but tends to
accumulate in one or more underground storage regions, called magma reservoirs,
before it erupts onto the earths surface. With each eruption, whether it is explosive or
non-explosive, the material erupted adds another layer to a growing volcano. After
many eruptions, the volcanic materials pile up around the vent or vents. These piles
form a hill, mountain, plateau,or a crater, that we today recognize as a volcano. Most
of the earth's volcanoes are formed beneath the oceans surfaces.
Volcano Formations Around
The World
Daytime
Night Time
Volcanic Materials
There are 3 different types of materials that can erupt from an
active volcano. These materials are lava, tephra and gases.
The type and amount of the material that erupts from an
active volcano depends on the composition of the magma
inside the volcano.
May 18, 1980. Mount St Helens
Eruption
Before
During
After
On May 18th, 1980 the eruption of Mt. St. Helens in southwest Washington state
disrupted the lives of thousands and changed more than 200 square miles of rich forest
into a grey, lifeless landscape. Now, twenty-two years later, the land around the
mountain is slowly healing itself. Nature is covering the scars of the eruption but
many people will never forget what happened that day.
Cinder Cone Volcanoes
• Cinder Cones are the easiest
type of a volcano. They are
built from particles and blobs
of congealed lava ejected
from a single vent. As the gascharged lava is blown into the
air, it breaks into small
fragments that solidify and
fall as cinders around the vent
to form a circular or oval cone.
Composite Volcanoes
• Composite volcanoes are
steep-sided. These
volcanoes can blast
fragments up to 8,000
feet above the base of
the volcano.
Lava Dome Volcanoes
• Lava Domes are
formed by small,
bulbous masses
of lava, which
piles over and
around the vent
of the volcano.
The dome grows
larger within
itself.
Shield Volcanoes
• Shield
volcanoes are
built almost
entirely of
lava flows.
The lava flows
out in all
direction from
the central
vent.
This is an eruption of
Stromboli Volcano in
August 2002.
Volcano damage is caused by clouds of ash that rise above a volcano, and in addition
some explosive eruptions produce avalanches of hot ash, rock and gas that move at high
speeds down the slopes of a volcano. Ash flows are the most destructive type of volcanic
activity. They are extremely hot and move across the ground as fast as, several 100
kilometers per hour. Ash flows knock down and burn everything in their way. Very few
living things can survive an ash flow. The damage a volcano causes is life-altering and can
even causes death in a lot of situations
 This is a picture of a
forest that has been
cleared from a volcano
eruption
Expected Hazards After A Volcano
Eruption
There are several processes that occur on the slopes of the volcano that are
hazards to humans and the environment around them. Most of the hazards are
directly caused by volcanic eruptions.
BLASTS OR PROJECTILES
Large projectiles can damage buildings; if these are hot they can start fires.
MUD FLOWS
Frequently accompany volcanic eruptions and can be lethal. Lakes can mix with volcanic rock and debris to form a nearsolid flow which engulfs all in its path.
PYROCLASTIC FLOWS
Mixtures of hot gases, ash, fine pumice and rocks; danger lies in the density and temperature of the ash and rock
fragments. Pyroclastic flows can move at very high speeds, possibly over 100 km/h. Hazards include body surface
burns, inhalation injuries and asphyxia.
•GASES
These may be asphyxiants which are concentrated near the volcanic crater or fissure or respiratory irritants which
are more dispersed and can be harmful at lower concentrations.
LAVA FLOWS
These are flows of extremely hot molten rocks extruded by the volcano. The viscosity and high temperature
make these flows very dangerous and they are capable of destroying all in their path.
LOCAL EARTHQUAKES
Possible loss of human life and property.
TSUNAMIS
Tsunami is Japanese for "tidal wave", the seismic wave that can hurtle across oceans at up to
600 miles per hour (800 km/hour). Occurrence is unpredictable and can destroy coastlines.
Volcanic eruptions are predicted by signs, some of which are not detected by any instruments, or
observed by volcanologists. The following are some points that should be taken into consideration to
respond effectively to a volcanic eruption:
BEFORE THE ERUPTION
Community Preparation
•Demarkation and evacuation of areas of risk.
•Formulation of and familiarization with search and rescue plans.
•Preparation of hospital emergency plans to cope with large influx of patients with burns, lung
damage and trauma.
•Identification of facilities to collect and analyse ash for toxic elements and drinking water quality.
•Facilities and equipment for monitoring air.
•Plans for procurement of emergency supplies.
•Report any and all unusual physical changes around volcanoes to the Seismic Research Unit, e.g.
the drying up of vegetation, rumbling sounds, earthquakes, landslides and other possible
abnormalities.
DURING THE ERUPTION
•Pay attention to Warnings, which would include evacuation notices and escape from area as quickly
as possible.
•Listen to the radio for information and advice.
•Find shelter, but NOT in a building with low-pitched or flat roof, if heavy ash is falling.
•Avoid basements and closed spaces where gases may accumulate.
•Wear protective clothing over head and body if you have to move in an ash shower.
•Breathe through a handkerchief.
•Always carry a flashlight, even during the daytime.
NORMAL - All the monitored parameters are within the levels exhibited during
non-eruptive (normal) periods, no eruption may be expected in the near
future.
ABNORMAL - Some of the monitored parameters had recently deviated from
the normal patterns. The abnormality may persist for some time and may
deteriorate and eventually lead to an eruption within the next few months.
ALARMING - Monitored parameters indicate conditions that resemble recorded
precursors, the abnormality may lead to an eruption in the near future,
probably within weeks or a few months.
CRITICAL - Monitored parameters indicate pre-eruptive conditions; the
volcano's condition may lead to an eruption in the immediate future, probably
within several weeks.
ERUPTION IMMINENT - The volcanoes condition indicate a high probability
for an eruption to occur in the immediate future, probably within a few weeks
or days.
ERUPTIVE - The volcano had entered an eruptive condition.
Resources
http://www.hewett.norfolk.sch.uk/curric/NEWGEOG/Tectonic/Volc/VOLFACTS.HTM
http://pubs.usgs.gov/gip/volc/fig8.gif
http://www.keadventure.com/images/volcanoes.jpg
http://www.ngdc.noaa.gov/seg/image/titlethumb/73900115.jpg
http://www.ngdc.noaa.gov/seg/image/titlethumb/73900115.jpg
http://www.jpl.nasa.gov/earth/er_images/volcanoes_31277.jpg
http://pubs.usgs.gov/gip/volc/fig8.gif
http://www.jgsc.k12.in.us/urey/composite.gif
http://www.geo.chs.nihon-u.ac.jp/tchiba/unzen.1995.dome.gif
http://mahi.ucsd.edu/Gabi/erth10.dir/shield.iceland.jpeg
http://www.solarviews.com/cap/volc/ashflow2.htm
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