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Volcanoes
- Landscape of vulcanity
- Extrusive activity
- Intrusive activity
- Extrusive activity
- Locations
- Subduction boundaries
- Sea-floor spreading centres
- Rifting on continental plates
- Rifting on continental plates
- Hotspots
- Individual plumes of magma rise to the crust
- Individual plumes of magma rise to the crust
- Subduction boundaries
- Eruption styles
- Hawaiian(Haw)
- Basaltic--> highly fluid lava
- Low gas content --> non
explosive/violent eruptions-->
effusive lava flows
- Shield Volcanoes eg
Kilauea, Hawaii and Mauna
Loa, Hawaii
- Basaltic--> highly fluid lava
- Strombolian(Strom)
- Moderate gas content-->
slightly more explosive than
Hawaiian eruption
- Cinder cones volcanoes
eg Mount Etna
- Basaltic/Andesitic-->
more viscous lava than
Hawaiian
- Moderate gas content-->
slightly more explosive than
Hawaiian eruption
- Vulcanian(Vul)
- High amounts of
gas-->steam
explosions-->
release old
material from
central vent
- Viscous basaltic to rhyolitic
- Tephra dispersed into wider areas
than Haw/Strom
- Cinder cones &
Stratovolcanoes
eg Vulcano, Italy
- High amounts of
gas-->steam
explosions-->
release old
material from
central vent
- Pelean(Pel)
- More viscous andesitic &
rhyolitic magma than Vul
- Upward escape of
explosive gasses
prevented by solidified
lava--> forces way out-->
nuee ardente
- Stratovolcanoes
eg Mount Mayon
- More viscous andesitic &
rhyolitic magma than Vul
- Plinian
- Gas-rich eruptions--> intensely violent
--> wide disperse of pyroclastic materials
- Stratovolcanoes
- Gas-rich eruptions--> intensely violent
--> wide disperse of pyroclastic materials
- Hawaiian(Haw)
- Primary Hazards
- Lava flows
- Depends on vicosity
- Steepness of ground
- Rate of prodn level
- Depends on vicosity
- Pyroclastic flows
- Destroys
everything in path
- Most dangerous:
Lateral blast
- Lead to lahars by damming
streams (water mix with rock
fragment)--> rush downstream
- Destroys
everything in path
- Tephra & ash fall
- Block sunlight--> temporary cooling of
atmospheric temperature
- Ash disrupts lives of ppl more than other volcano
hazards bc leads to low economic activity by
reducing visibility and is slippery
- Block sunlight--> temporary cooling of
atmospheric temperature
- Volcanic gasses
- Sulphur dioxide gas--> acid rain & air pollution
- Carbon dioxide > 30% is lethal
- Sulphur dioxide gas--> acid rain & air pollution
- Lava flows
- Secondary Harzards
- Lahar
- Volcanic Landslide
- Tsunamis
- Earthquake
- Torrential Rain
- Atmospheric effects
- Lahar
- Mitigation
- Lava Flow Dams
- Redirect lava flow. Rely on the fact
that basaltic lava do not behave like
bulldozers. Can contain basaltic lava.
Small flow to prevent lava from
getting down to lower parts of
volcano. Big flow--> spill down but give
sufficient time for ppl to evacuate
- Redirect lava flow. Rely on the fact
that basaltic lava do not behave like
bulldozers. Can contain basaltic lava.
Small flow to prevent lava from
getting down to lower parts of
volcano. Big flow--> spill down but give
sufficient time for ppl to evacuate
- Hazard Mapping
- Long term planning. Show areas most likely to
be affected by diff types of volcanic activity.
Indicate relative degree of hazard occurring.
Good for land-use & effective
emergency-response measures--> will save many
ppl and avoid dmgs to property
- However, if met with strong
opposition from economic interests> will likely be
produced not long b4 eruption>
insufficient time for proper dissemination
of map to public
- However, if met with strong
opposition from economic interests> will likely be
produced not long b4 eruption>
insufficient time for proper dissemination
of map to public
- However, not sure of the
accuracy for (a) size of
eruption (b) duration of
eruptive activity (c) extent
of topographic changes (d)
specific vent location
- Long term planning. Show areas most likely to
be affected by diff types of volcanic activity.
Indicate relative degree of hazard occurring.
Good for land-use & effective
emergency-response measures--> will save many
ppl and avoid dmgs to property
- Educating the public
- Lessen physiological and physical impacts
of eruption on the public. Warnings can be
better understood if public understands
nature of hazard. We can also use hazard
map to educate
- Lessen physiological and physical impacts
of eruption on the public. Warnings can be
better understood if public understands
nature of hazard. We can also use hazard
map to educate
- Crisis Response
- Emergency evacuation plans are
developed to ensure safest and most
efficient evacuation time should any
natural disasters occur
- However, inadequacy of the
community in responding to the
imminent disaster was
compounded by the failure of local
authorities to respond in a timely
manner. Complacency. Chain of
command and sometimes a
meeting along the way. Eg Nevado
del Ruize
- However, inadequacy of the
community in responding to the
imminent disaster was
compounded by the failure of local
authorities to respond in a timely
manner. Complacency. Chain of
command and sometimes a
meeting along the way. Eg Nevado
del Ruize
- Emergency evacuation plans are
developed to ensure safest and most
efficient evacuation time should any
natural disasters occur
- Lava Flow Dams
- Monitoring
- Tilt Meters
- Monitor deformation caused by upward
movement of magma underneath
surface
- Monitor deformation caused by upward
movement of magma underneath
surface
- Eruption Recurrence Interval Prediction
(Long Term)
- A cycle may be evident eg
Hawaii displays regular eruptive
sequences w definable intervals
- Ascertain historic style of
eruption. Determine the
volcano's eruption interval.
- A cycle may be evident eg
Hawaii displays regular eruptive
sequences w definable intervals
- Physical Anomalies and
Precursor Phenomena
- Ground deformation as magma
moves into a volcano. Tilt meters
measure changes in angle of volc's
surface
- Volcanic gasses such as hydrogen
chloride & sulphur dioxide emitting
from volcanic vents
- Ground deformation as magma
moves into a volcano. Tilt meters
measure changes in angle of volc's
surface
- Tilt Meters
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