volcanic hazards Flashcards
Can you give some primary volcanic hazards
Eruption column (cloud of tephra and gasses)
Volcanic gases
lava flows
nuées ardente / pyroclastic flow
Tephra
give an example of a case involving an eruption column
Chaitén, Chile, 2008.
Typical of plinian eruptions.
give an example of a case study involving a lahars
Nevado del Ruiz destroyed Colombian town of Armero.
1985.
give a case study involving volcanic landslides
Mt. St. Helens eruption - largest volcano landslide!
Give a case study with large pyroclastic flows
Pompeii?
79AD
Vesuvius.
Give a case study of lava flows
Erupting basaltic since 1983
Kilauea volcano
Hawaii
Lava flows destroying almost 200 houses.
Give a case study with volcanic gases
1986 -
Lake Monoun (Cameroon) contaminated 1,700 die.
What’s the difference between EFFUSIVE and EXPLOSIVE eruptions?
EFFUSIVE: molten rock ejected - small eruptions
EXPLOSIVE: rock ejected. - big eruptions!
Each step in the VEI (?) scale represents an explosivity increase of how much?
VEI - volcanic explosivity index
10X more than previous rating.
10-100-1000 (tenfold)
Give some secondary hazards
Lahars
Flooding
Tsunamis
Avalanches
Landslides
Climactic change (1991 mount Pinatubo lowered global temps by 1 degree C!)
Give 3 short term impacts of eruptions
disease
can make geothermal energy
environmental devastation
give 2 long term impacts of hazards
Nutrient rich soil
tourism - Vesuvius.
Impacts of eruptions (SEEP)
Social: homes + land destroyed. Death + disease.
Environmental: acid rain
Economic: Buildings + businesses destroyed.
Political: mistrust gov.
list the VEI in order
Icelandic
Hawaiian
Strombolian
vulcanian
pelean
Plinian
Ultra plinian
where can one locate a volcano…
CONSTRUCTIVE (divergent) plate margins
- oceanic ridges (Mid Atlantic ridge) + The Great Rift Valley in East Africa. (created Kilimanjaro).
SUBDUCTION ZONES
- Ring of fire + Island arcs
HOT SPOTS
- Hawaiian islands - e.g Mauna Loa.
What are the 5 types of volcano?
basic shield - divergent - basaltic
acid dome - convergent - rhyolitic
composite - convergent - rhyolitic
Ash and cinder - convergent - basaltic
Caldera - Hotspots only - Basaltic
monitoring a volcano
increase in release of gases
rise in level of lava lakes in volcanic craters
bulging upwards of surrounding land due to pressure
increasing number of small earthquakes (magma rising)
why are some volcanoes more hazardous?
viscosity of magma
frequency of eruptions and risk perceptions
predictability
proximity to population centres
materials ejected
explosivity
plate margins
Intrusive and extrusive volcanic activity?
IGNEOUS ROCKS
Intrusive - happens inside the volcano - form big crystals - granite.
Extrusive - happens outside - small crystals - pumice.
3 preparation ideas
Land zoning
lava/lahar diversion channels
volcano - proof house - e.g roof support.
ways to build resilience
mobile phone warnings
education
emergency services
stockpiling resources
practice drills.
what equipment do scientists use to monitor volcanoes?
seismometer
tiltometers
radon gas levels
thermal imaging (like a pregnancy scan for a volcano :)
Magnetometer
drilling into volcanoes (can detect when last erupted due to gases)
what are the 3 stages of the Park’s model?
Relief (hrs/days)
Rehabilitation (days/weeks)
Reconstruction (weeks/years)
what is a seismometer/seismograph?
detects microwaves from increasing small e-quakes as magma rises.
What is a tiltometer?
monitors how much the sides of the volcano have moved (flanks bulging with magma)
what are Radon gas levels?
used to see how much sulpher dioxide is in the rick.
What is a magnetometer?
see magnetism of the magma (magma contains magnetite - the reason for magnetic striping.)
What is thermal imaging
Looks at magma levels within the volcano.
what are the 3 types of lava?
Basaltic
Andesitic
Rhyolitic
