Volcanic eruptions

1. Volcanic Eruptions
Disaster Management
Dr Fayaz A. Malla
Assistant Professor, Environmental Sciences
GDC Tral
Higher Education Department, Govt. of J&K
Email: nami.fayaz@gmail.com

2. A volcano is an opening or rupture in the earth’s surface that
allows magma (hot liquid and semi-liquid rock), volcanic ash and gases to
escape.
They are generally found where tectonic plates come together or
separate, but they can also occur in the middle of plates due to volcanic
hotspots.
A volcanic eruption is when lava and gas are released from a volcano—
sometimes explosively.
The most dangerous type of eruption is called a 'glowing avalanche' which
is when freshly erupted magma flows down the sides of a volcano.
They can travel quickly and reach temperatures of up to 1,200 degrees
Fahrenheit.
Other hazards include ash fall, and lahars (mud or debris flows).
Volcanoes often cause population displacement and food shortages.
Volcanic
Eruptions

3. Volcanic Eruption
mechanisms
• There are two types of eruptions in terms of activity,
explosive eruptions and effusive/fissure eruptions.
• Explosive eruptions are characterized by gas-driven
explosions that propels magma and tephra.
• Effusive/fissure eruptions, meanwhile, are characterized by
the outpouring of lava without significant explosive eruption

4. Volcanic
Explosivity Index
• The Volcanic Explosivity Index (commonly
shortened to VEI) is a scale, from 0 to 8,
for measuring the strength of eruptions.
• It is used by the Smithsonian
Institution's Global Volcanism Program in
assessing the impact of historic and
prehistoric lava flows.
• It operates in a way similar to the Richter
scale for earthquakes, in that each
interval in value represents a tenfold
increasing in magnitude (it is logarithmic).
• The vast majority of volcanic eruptions
are of VEIs between 0 and 2.

5. Types of Volcanic
Eruption
Hawaiian
• Hawaiian eruptions are a type of volcanic eruption
named after the Hawaiian volcanoes with which this
eruptive type is hallmark.
• Hawaiian eruptions are the calmest types of volcanic
events, characterized by the effusive eruption of
very fluid basalt-type lavas with low gaseous content.
• The volume of ejected material from Hawaiian
eruptions is less than half of that found in other
eruptive types.
• Steady production of small amounts of lava builds up
the large, broad form of a shield volcano.
• Eruptions are not centralized at the main summit as
with other volcanic types, and often occur at vents
around the summit and from fissure vents radiating
out of the center.

6. Strombolian
• Strombolian eruptions are a type of volcanic eruption named
after the volcano Stromboli, which has been erupting nearly
continuously for centuries.
• Strombolian eruptions are driven by the bursting of gas
bubbles within the magma.
• These gas bubbles within the magma accumulate and coalesce
into large bubbles, called gas slugs.
• These grow large enough to rise through the lava column.
• Upon reaching the surface, the difference in air
pressure causes the bubble to burst with a loud pop, throwing
magma in the air in a way similar to a soap bubble.
• Because of the high gas pressures associated with the lavas,
continued activity is generally in the form of episodic explosive
eruptions accompanied by the distinctive loud blasts.
• During eruptions, these blasts occur as often as every few
minutes.
Types of Volcanic
Eruption

7. Vulcanian
• Vulcanian eruptions are a type of volcanic eruption
named after the volcano Vulcano.
• In Vulcanian eruptions, intermediate viscous magma
within the volcano make it difficult for vesiculate gases to
escape.
• Similar to Strombolian eruptions, this leads to the
buildup of high gas pressure, eventually popping the cap
holding the magma down and resulting in an explosive
eruption.
• However, unlike Strombolian eruptions, ejected lava
fragments are not aerodynamic; this is due to the higher
viscosity of Vulcanian magma and the greater
incorporation of crystalline material broken off from the
former cap.
• They are also more explosive than their Strombolian
counterparts, with eruptive columns often reaching
between 5 and 10 km (3 and 6 mi) high. Lastly, Vulcanian
deposits are andesitic to dacitic rather than basaltic.
Types of Volcanic
Eruption

8. Pelean
• Peléan eruptions are a type of volcanic eruption
named after the volcano Mount
Pelée in Martinique, the site of a Peléan eruption
in 1902 that is one of the worst natural disasters in
history.
• In Peléan eruptions, a large amount of gas, dust,
ash, and lava fragments are blown out the
volcano's central crater.
• The material collapses upon itself, forming a fast-
moving pyroclastic flow (known as a block-and-
ash flow)that moves down the side of the
mountain at tremendous speeds, often over
150 km (93 mi) per hour.
• These landslides make Peléan eruptions one of the
most dangerous in the world, capable of tearing
through populated areas and causing serious loss
of life.
Types of Volcanic
Eruption

9. Plinian
• Plinian eruptions (or Vesuvian eruptions) are a type of
volcanic eruption named for the historical eruption of
Mount Vesuvius in 79 AD.
• The gases vesiculate and accumulate as they rise
through the magma conduit. These bubbles agglutinate
and once they reach a certain size (about 75% of the
total volume of the magma conduit) they explode.
• Eruption velocity is controlled by the gas contents of the
column, and low-strength surface rocks commonly crack
under the pressure of the eruption, forming a flared
outgoing structure that pushes the gases even faster.
Types of Volcanic
Eruption

10. Types of Volcanic Eruption

11. Distribution of Volcanoes
• Circum-Pacific belt or Pacific ring of fire
• Mid-continental belt
• Mid-Oceanic ridge belt

12. Causes of Volcanic Eruptions

13. Hazardous
effects of
Volcanic
Eruptions
Advancing lava flows, known as Lahar down the slope of volcanic
cones
Fallout of volcanic materials
Heat of lava which ignites fire and burns houses, vegetations etc.
Emission of harmful gases such as CO2, SO2, CO, H2S, CS, CS2, HCL,
H CH4 etc.
Emission and fallout of inorganic compounds such as heavy metals
e.g., mercury, lead, gold
Earthquakes caused due to violent explosive eruptions of
volcanoes
Tsunamis generated after violent explosive eruptions and strong
seismic events, etc.

14. Damages
caused by
Volcanic
Eruptions
Damage by lava flow
Damage by fallout of volcanic matter
Human causalities
Damage due to Tsunami generated by Volcanic
Eruptions
Damage to Man-made and natural features
Volcanic dusts and climate change
Volcanic Eruptions and Ecological Changes

15. Management of
Volcanic Disaster
• Assessment and analysis of
vulnerability to volcanic
eruption
• Risk assessment of
impending volcanic disaster
• Disaster preparedness
• Volcanic disaster response
measures
Steps and measures of reduction and
management of volcanic disaster
include the following

16. Volcanic Disaster Mitigation and Preparedness
Identification of existing
volcanoes and mapping of
volcanic hazard zones
Predictability and
prediction of impending
volcanic eruption
Determination of seismic
hazard probability and
dependent eruption
probability
Evaluation and assessment
of vulnerability of buildings
roads and network etc.
Social preparedness and
assessment of probability
of bad reactions all for the
society or certain segments
of human population
Vulnerability of
information system and
management of media
Rescue system efficiency
time of intervention
capability etc.
Efficiency of health sector
and facilities for timely
treatment of injured
people capability of
treatment of diseases
Scientific knowledge about
different aspects of
volcanic disaster
General awareness about
danger and adverse effects
of volcanic disasters and
protective measures and
precautionary measures

17. Elements of General Preparedness
Identification
demarcation and
mapping of volcanic
hazard zones
To prepare inventory of
valuable movable
property
Identification of safe
refuge zones and
evacuees
Identification of
evacuation routes
Demarcation of points
for the assembly of the
persons awaiting
transportation for going
to safer areas
Provisions for easily
available means of
transport
Proper shelters and
accommodation in
refugee camps or areas
Inventory of personnel
and equipment for
search and rescue
Provisions of hospitals
and medical services
for treatment of injured
people
Proper security
arrangements in
evacuated zones
Provision of emergency
alert and warnings
Communication of
emergency
Formulation of
emergency
management plans

18. Thank
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