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VOLCANOES (Types of Eruptions (Viscosity, Temp. + Composition (Viscosity…

- - - - Most silica content
      - Most gas content
      - Highest viscosity
      - Lowest temp. at eruption
    - - Middle
    - - Least silica content
      - Least gas content
      - Least viscosity
      - Highest temperature at eruption
  - - - Eruption rate
      - Product volume
      - Eruption column + altitude
      - Duration
    - - Explosive
        
        High VEIs
        
        Shortest period of time
      - Effusive
        
        Low VEIs
        
        Longer period of time
    - - Categorised from 0-8
      - Probelms
        
        When magma chamber empties are eruption, it is refilled- but the new magma can be of a different composition = change in categorisation of volcano
- - - - Caldera is above mantle plume
      - Crust is relatively thick + buoyant - acts as a lid on top of magma chamber
      - Thick crust - rising magma cannot escape
        
        So magma differenitates in the chamber = rhyolitic + granitic viscous melts that trap gases
      - As magma is forced upwards, it fractures and lifts the crust
  - - - Sound waves travel slower thru hot molten materials compared w solid rocks
  - - - Acid rain
      - Acidification of water supplies
    - - Fall due to decreased global temperatures = less evaporation
      - Less evaporation = less rainfall
      - Decreased rainfall affects crops - esp. in sub-tropical regions
    - - VE 8 would affects temps. by 4 degrees
      - Prevents UV rays from reaching the surface
      - Ash clouds block sunlight = decreased temperatures
    - - Reduction in yield
      - Food shortage
      - Might have global effects if rainfall decreases
        
        In tropical regions monsoon rains are needed for rice production in Asia
      - Die near volcano
      - UN estimates that we have 74 days of food supply
    - - Animals affected is water is contaminated
      - Land/habitat destroyed
      - Animals deaths due to lack of fodder
    - - Phone lines
      - Internet
      - Radio - no warnings/updates available
      - Satellite info. out
      - Tremors damage power + water lines
      - Lahars could wipe out power stations
      - Ash cover can collapse power lines
  - - - 60-70% of the heat is leaked via the water
    - - Could be used to power generators
    - - Drilling could trigger an explosion
- - - - Near the main city in Sicily
      - Key landing point for migrants to Italy
      - Lemon groves - significant export
  - - - Increased paroxysms (explosive episodes) = ash + gas
    - - S eruption + NE eruption occurred simultaneously
      - Monitoring + Prediction
        
        Seismic swarms in SE crater - magma fractures rock = EQ
        
        Seismic activity was only a few hours before the eruption of 2002
        
        2 different phases of magma
        
        Magma vent uses central magma source + is degassed
        
        Magma from flank is not degassed as it is from a subsidary conduit = more viscous + explosive
        
        Projected lava flows correct + so communities were saved
        
        Explosives + concrete dams used to direct lava flows
        
        Earth bunds used to divert lava flows heading to cable cars + nature reserves
        
        Daily inspections of lava field and fly-overs with thermal cameras - monitored lava flows in case of emergency evacuations + new eruptions along fissures
        
        Water-spraying aircraft used - was 5 miles from town
        
        NE slope was a fracture zone 2/3 mile long near Pinao Provenzana
        
        Eruption was unpredictable - speeds changed daily + not sure how long it would last
      - Characteristics
        
        Eruptions fed from 2 main magma sources
        
        High altitude vents = low viscosity, low gas, basaltic lava
        
        Lava vents were fed by subsidary conduit independent of main magma source
        
        Magma had not degassed = depressuried suddenly when erupted
        
        Gas expanded and exploded lava rocks = ash fall, lava bombs + lapilli
        
        More explosive = inc. risk to populations living at lower elevations on eastern flank
        
        Eruption occurred simultaneously in 3 areas
        
        Central vent
        
        NE flank eruptions: Pinao Provenzana + Etna Nord
        
        S flank eruptions
  - - - 10 km high
      - Affected air traffic - closed Catania International Airport = loss of revenue from cancelled flights + tourist visits
      - Ash fell for 30 days
    - - Last for weeks/months compared to short-lived summit eruptions
- - - - Oldest + most reliable method
      - Micro-EQ activity
      - Richter scale - relative measurement of energy released
      - Network of seismometers
        
        Placed within bedrock to block out sound from traffic
        
        Network of stations used to find epicentre and magma chamber
      - Tremors as magma rises
      - Short-period high-freq. = magma chamber filling
      - Long-period, low-freq. harmonic tremors = magma chamber full + eruption imminent
      - Initial tremor is followed by continual tremors
  - - - Tiltmeter gives small measurements of E's crust
      - Measures inflation + deflation as magma rises
      - Peak inflation = eruptions
      - Chamber empties = deflation
      - Monitoring stations surrounding volcano
    - - Monitor eruption activity
      - Ash plumes tracked
      - Measuring hotspots - changes in SO2
      - Ground deformation via GPS
      - Thermal imaging - changes in temperature + heat emitted from hot springs
      - Mt St. Helens
        
        Building new cone inside crater
        
        Sensors for seismometers (magma moving kilometeres beneath surface)
        
        Ground-based + space-based components communicate
  - - - Number + type of gases emitted
      - Increase in gases = increases in likelihood of eruption
    - - Chemistry + gas of magma + silica
      - Characteristics of magma = info. on how the eruption might proceed
  - - - Red periods - active - 5 of these
      - Green periods - no activity - currently in longest one
    - - Seismo. network in 2008 meatn that everyone was evacuated
      - Identify patterns = warning can be issued for evac.
      - Pause in seismic activity = evacuation period - magma is finding its way to the surface
      - High-freq. tremors - magma rising to surface + cracking crust
      - Swarms - low freq. long period harmonic tremors - m chamber is full
      - So many events they merge into one another = magma moving
    - - 2 points- one on mountian + one away from it
      - Good GPS network of tiltmetres
      - Measure inflation + deflation
      - Vol. swells = pressure building and there is an long pause between the 2 GPS points
      - Explosion = shorter pause between 2 GPS points + pressure realeased
      - Pressure on flanks = expansion
      - Shows if inflation is still occurring to determine when to re-enter exclusion zone
    - - Composition of gas in plume is monitored
      - Diff. to sample directly
      - Amount of light reflected by plume = gas composition
      - Avg. 300 tonnes SO2/day - too high for inactive vol.
      - More useful for assessing certainty than prediction
        
        It ties in with the 'green period'
  - - - Flooding
        
        Glacial output flood in one of the main hazards in Iceland
        
        Can reach peak discharge within 1 hour
        
        Glacial meltwater must be constantly monitored
        
        2010 eruption
        
        Volcanic temperature and electrical conductivity of meltwater
        
        Realt-time data: water level, conductivity + temp.
        
        Deformation + river level monitoring - allows prediction of eruption months in advance
      - London Aviation Centre was contacted months in advance coz of environmental monitoring
      - Ash
        
        EU + US flight paths affected by ash
        
        Monitoring and predicting ash movement kept travelers safe
      - Deformation
        
        Graben/rift valleys form at the Eurasian and N Am plate - cracking + movement
        
        How land changes varies across the rift
        
        Low rate of deformation in centre of graben
        
        High rate of deformation at edges of valley
        
        GPS is used - v. accurate - antenna measures to mm over years
        
        Tectonics, hotspots, glaciers - Iceland is uplifting at a great rate
- - - - Low melting point = always molten
      - Cools immediately
  - - - Steam appeared from vents at top + sides
      - Ash + steam forced out of the vents - phreatic eruption = lava on the move
      - Lava came 4 months after ash + steam
      - Dome grows as lava rises
  - - - Collapse = exposure of hotter materials
      - Large lava dome collapse = magmatic eruptions
    - - Hundreds degrees
      - Hot gases, rock particles, ash
      - Lasted for first few months
      - Asphyxiation
      - Flattening of vegetation
      - Fires + habitual destruction
    - - Large parts of islands were covered w tephra
      - Much tephra on volcano sides
      - When mixed with precipitation = lahars
    - - Secondary hazard
      - Little vegetation to hold the ash on bare slopes = easy to form lahars and much energy in lahars
      - Several valleys covered in metres of ash
      - Destruction of golf course - key tourist attraction
      - Many houses flooded and dragged into the river
  - - - Loss of large areas of vegetation - affected local species
      - Rainforest habitats destroyed
      - Ash acidifies water
      - Ash decreased insect abundance = less food for animals
      - Livestock now ferrel
      - 300m extension on eastern coast bc of pyroclastic flows = coral destruction - tourism impact
    - - Ash covered the coral - won't ever recover - key part of tourism + economy
      - Gov. buildings + main port covered in ash
      - Complete destruction of Plymouth due to 16 years repeated cycle of washing away ash + pyroclastic flows
      - Pop decrease: 12,000 in 1950; 5-6000 now
- - - - Money for recovery
      - Loss of houses - no insurance
      - Foreign aid
    - - Age distribution
      - Pops. resistent to relocaiton
    - - Preparedness
      - Evacuation procedures
      - Evacuation shelters
      - Place attachment
        
        Belongings vulnerable to looting if residents leave
    - - Flat land/downward slope = lava travels faster
      - Farmland or not - crops destruction
      - Deforestation - vulnerable to flooding
        
        Inland deforestation has occurred for palm oil
  - - - Landslides
        
        Destruction of farmland, homelessness, deaths, habitual destruction
      - Fires
        
        Widespread landscape destruction, gases (pollute water supplies), casualties
      - Lava Flows
        
        No farming foe 000s years for land to regrow
      - Gas + heat
        
        Fires + respiratory problems. Heat = sterilisation of soil = no growth
      - Ash
        
        Crop + animal deaths. Collapses roofs
    - - Tsunamis
        
        Building destruction + environ. damage. Coastal settlements + infrastructure lost
      - Ash deposits on crops
        
        Food shortage, loss of income, LT effect on agricultural jobs
      - Famine
        
        Malnutrition, stunting, loss of economic potential
      - Travel disruption
        
        Damage to trade and industry
      - Disease
        
        Cholera
      - Aerosols + ash in upper atmosphere
        
        Global cooling
      - Lahars
        
        Destruction of settlements on flanks
- - - - Make hazard maps via lava flows
      - Forecast routes
      - Use models to run eruptive scenarios
      - Take lava samples to determine speed - is diff. coz of fissure eruptions = magma moves along many routes
    - - Give risk assessments
      - Issue warnings
      - Strategy depends on eruption type (effusive/explosive, fissure/flank)
        
        Fissure is most difficult due to topography + is closer to settlements
    - - Accustomed to hazard
      - They spread the landholding on the eastern flank so that it is not concentrated in areas of greatest risk of lava flows
      - Retailers at Piana Provenzana have mobile units to move out of the way = reduction in economic loses
      - Strong catholic beliefs
  - - - Imp. magmatic gas
      - Emitted in huge quantities on flanks
      - High CO2 levels = magma rising + high pressure
    - - 78 along coast - 60% on Etna
      - Track movement of magma + fluids
      - Locates the source
    - - Studies fractures that are possible magma paths
      - Defines what regions are more dangerous - for hazard maps
    - - Developing + enforcing building codes
  - - - Very expensive for small businesses
      - Premium is v high due to high risk of lava flows
      - But there is 2-3 years of tax relief for businesses affected by vols.
      - Key strategy in ACs
      - V. expensive in freq. affected areas - can be unavailable
      - Premiums increase with claims
    - - Monitoring = warnings + evac. procedures
      - SMS ,landline, radio
    - - Identify where, then, how
      - Allows warnings to be given+ evacs. made
      - Minimises loss of life + damage
    - - Prevents development in hazardous areas
      - No roads/bridges in areas susceptible to mudflows
- - - - Sends intrusive magma upwards
      - Magma plume rises as it is hotter + less dense
    - - Continental plate moves but the mantle remains the same
      - Will take millions of years for plate to move away from magma source
    - - They are low and smaller and become sea mounts bc:
        
        They're eroded - unvegetated slopes
        
        Cone subsides as it moves away from heat sources and cools
  - - - Emits more heat than any other
      - Fire fountain
      - Built the island
      - Hawaii is still growing as new lava pours into sea
        
        As lava enters sea, there's high volatility
        
        Large boulder explosions
        
        Forms pillow lavas
    - - Studying composition of lava - how deep it is below earth - they analyse chemical composition
      - Basalt lava
        
        Very fluid
        
        Effusive
        
        Low viscosity
        
        V hot - 1000 degrees
      - Is identical to lava from 4bn y/a when earth was being formed
- - - - One of country's top visitor attraction - +700k visitors in 2015
    - - Means Icelandi pops. stay in Iceland
      - Residents may remain in remote and inaccessible areas bc of increased tourist flow