volcanic hazards 50-60 volcanoes erupt each year! f 2-3 in usa usually in unpopulated areas, but not...
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Volcanic HazardsVolcanic Hazards50-60 volcanoes erupt each year! 50-60 volcanoes erupt each year!
2-3 in USA 2-3 in USA
Usually in unpopulated areas, but not always: Usually in unpopulated areas, but not always: JapanJapan PhilippinesPhilippines IndonesiaIndonesia ItalyItaly NW USANW USA
Volcanic HazardsVolcanic HazardsPlate tectonics and volcanismPlate tectonics and volcanism
Hot spots can be either Hot spots can be either oceanicoceanic (Hawaii) or (Hawaii) or continentalcontinental (CRB, Yellowstone) (CRB, Yellowstone)
VolcanismVolcanismMid-ocean ridgesMid-ocean ridges
BasaltsBasalts from partial melting of the mantle from partial melting of the mantle
VolcanismVolcanismMid-ocean ridgesMid-ocean ridges
Iceland is the only major threatened area (hot spot?)Iceland is the only major threatened area (hot spot?)
Walla Walla
PacificPlate
IndianPlate
NazcaPlate
Antarctic Plate
AmericanPlate
EurasianPlate
AfricanPlate
EurasianPlate
0o
30o
30o
60o
75o
75o
60o ReykjanesRidge
Mid
-Atl a
ntic
Rid
geSouth East Indian
Central IndianOcean Ridge
Juan de Fucaand Gorda Ridges
Galapagos Spreading Center
Ocean RidgeSouth West Ind ian O
c. Rid
ge
East P
acific
Rise
VolcanismVolcanismHot SpotsHot Spots
Ocean islands:Ocean islands: Hawaii, Azores, Fiji, Canaries... Hawaii, Azores, Fiji, Canaries... ContinentalContinental hot spots: CRB, Yellowstone... hot spots: CRB, Yellowstone...
PacificPlate
IndianPlate
Antarctic Plate
AmericanPlate
EurasianPlate
AfricanPlate
EurasianPlate
0
30
30
60
75
75
60Bowie
YellowstoneBermuda
Baja
Hawaii
Easter
Marquesas
Pitcairn
Galapagos
San Felix
Juan Fernandez
Cobb
Iceland
Fernando
Ascension
AzoresMadeira
CanaryG. MeteorCape Verde Hoggar
TibestiDarfur
Cameroon
Ethiopia
Trindade St Helena
Tristan
Vema
Cape
Bouvet
Crozet
E. Africa
Comoro
Reunion
Gough
Kerguelen
SE Australia
Caroline
SamoaCocos
Society
Tubai
VolcanismVolcanismHot SpotsHot Spots
Plates move as hot spots remain ~ stationaryPlates move as hot spots remain ~ stationaryHawaii:Hawaii:
Oceanic Hot spot Oceanic Hot spot plumes plumes basaltbasalt
Low viscosityLow viscosity
Shield VolcanoShield Volcano
VolcanismVolcanismHot SpotsHot Spots
Plates move as hot spots remain ~ stationaryPlates move as hot spots remain ~ stationaryCRB - SRP - Yellowstone:CRB - SRP - Yellowstone:
Present
CRBG
SRP
WA
OR
CA NV
MT
WY
ID
UT
Yellowstone
Walla Walla
VolcanismVolcanismRidge and Hot Spot volcanism is Ridge and Hot Spot volcanism is
predominantly predominantly basalticbasaltic Basalts are Basalts are low viscositylow viscosity melts melts Gases escape easily and eruptions are Gases escape easily and eruptions are not explosivenot explosive Most common hazards are Most common hazards are flowsflows and and ashash deposits deposits
Subduction Zone VolcanismSubduction Zone Volcanism Melting of slab and/or dehydration Melting of slab and/or dehydration melting of melting of
mantle wedge above the slabmantle wedge above the slab Island Arc: Japan, Aleutians, Indonesia, Caribbean...Island Arc: Japan, Aleutians, Indonesia, Caribbean... Continental Arc: Cascades, AndesContinental Arc: Cascades, Andes
Subduction Zone VolcanismSubduction Zone Volcanism Basalt - andesite - dacite - rhyoliteBasalt - andesite - dacite - rhyolite Each is progressively more viscous and Each is progressively more viscous and explosiveexplosive Strato-volcanoes (composite volcanoes)Strato-volcanoes (composite volcanoes) Flows and Flows and pyroclasticspyroclastics Far more dangerous due to explosive natureFar more dangerous due to explosive nature
Continental Subduction Zone (and some hot-spot) VolcanismContinental Subduction Zone (and some hot-spot) Volcanism
Real biggies: Real biggies: rhyoliterhyolite calderacaldera eruptions eruptions Long Valley, Yellowstone, Vallez in New MexicoLong Valley, Yellowstone, Vallez in New Mexico Melt base of silica-rich continental crustMelt base of silica-rich continental crust Subduction related or hot spot? Behind SZ properSubduction related or hot spot? Behind SZ proper No historic eruptions (thank goodness!)No historic eruptions (thank goodness!)
Lassen Peak is a rhyolitic Lassen Peak is a rhyolitic domedome Hydrothermal activity: hot springs, geysers Hydrothermal activity: hot springs, geysers
geothermal energygeothermal energy
Volcanic HazardsVolcanic Hazards
FlowsFlows Mostly basaltic Mostly basaltic
Hawaii: ~ 1 m/hrHawaii: ~ 1 m/hr CRBs fasterCRBs faster
Run through property, but easy to evacuate in Run through property, but easy to evacuate in advance, so little threat to lifeadvance, so little threat to life
The Columbia River Basalts and Oregon High Lava Plateau The Columbia River Basalts and Oregon High Lava Plateau are dominated by lava flows. are dominated by lava flows. During the peak of CRB activity (16-18 million years ago) some massive individual flows may have exceeded 2000 km3 or even 3000 km3, which would qualify them as the largest known terrestrial lava flows
Volcanic HazardsVolcanic Hazards
FlowsFlows Control?Control?
Spray water and chill (Heimaey & Mt. Helgafell: Spray water and chill (Heimaey & Mt. Helgafell: modest success... fortuitous?)modest success... fortuitous?)
Construct walls and diversionsConstruct walls and diversions Bombing? Block established channelwayBombing? Block established channelway Nothing will stop a large flowNothing will stop a large flow
Volcanic HazardsVolcanic Hazards
PyroclasticsPyroclastics Basalts in ridge-hot spotBasalts in ridge-hot spot
Ash of minor importanceAsh of minor importance Can be locally destructive, howeverCan be locally destructive, however
PyroclasticsPyroclastics
Subduction-related eruptionsSubduction-related eruptions Pyroclastics much more important and damagingPyroclastics much more important and damaging
1.1. Vertical ash columnsVertical ash columns (“Plinian” eruptions) (“Plinian” eruptions)
Vertical plinian ash Vertical plinian ash column from Mt. St. column from Mt. St. Helens, 1980Helens, 1980
Mount Pinatubo, Philippines, on June 12, 1991
Pyroclastics Pyroclastics
Subduction-related eruptionsSubduction-related eruptions Pyroclastics much more important and damagingPyroclastics much more important and damaging
1.1. Vertical ash columnsVertical ash columns (Plinian eruptions) (Plinian eruptions) Ash fall blanketAsh fall blanket Huge area, but more of a nuisance at a distanceHuge area, but more of a nuisance at a distance
Destroys vegetationDestroys vegetation Contaminate surface waterContaminate surface water Collapse roofsCollapse roofs
Can be thick and noxious close by (Pompeii) Can be thick and noxious close by (Pompeii) Also Also hothot
Pompeiian body postures suggest heatPompeiian body postures suggest heat
Pyroclastics Pyroclastics
Subduction-related eruptions
2. Pyroclastic flows Travel at several hundred km/hr and Travel at several hundred km/hr and 800 800ooC or higherC or higher
A. A. Gravitational collapse of ash column Gravitational collapse of ash column B. B. Lateral blast (Mt St Helens & others)Lateral blast (Mt St Helens & others)
C. C. Caldera overflowCaldera overflow
Any may Any may nuée ardentenuée ardente (glowing cloud) (glowing cloud) ignimbrite ignimbrite Hug ground as base surge, fluidized by gas contentHug ground as base surge, fluidized by gas content
Mt. St. Mt. St. HelensHelensAug. 7, Aug. 7, 19801980
Martinique after Nuée Ardente from Mont Pelée, 1902
Huge Rhyolitic EruptionsHuge Rhyolitic Eruptions Long ValleyLong Valley
Mono Craters
Mammoth Mtn
Long Valley caldera along the east side of the Sierra Nevada in east-central California
Many eruptions in last 3 Ma incl. massive, caldera-forming eruption 760,000 years ago
Most recent eruptions occurred just 500 to 600 years ago from vents along the Mono Crater-Inyo crater volcanic chain, Mono Lake to western part of Long Valley caldera
Long ValleyLong Valley Earthquakes began to increase in 1978 & 1Earthquakes began to increase in 1978 & 1stst swarms in 80's swarms in 80's Related to Related to magma chambermagma chamber 8 km below Long Valley 8 km below Long Valley 32 x 15 km 32 x 15 km calderacaldera from eruption only 760,000 yrs ago from eruption only 760,000 yrs ago 4 large earthquakes in May 19804 large earthquakes in May 1980 Resurvey Resurvey "resurgent dome" had risen 25 cm since 1975 "resurgent dome" had risen 25 cm since 1975 By 1982 had risen another 7 cm & caldera up 18-20 cmBy 1982 had risen another 7 cm & caldera up 18-20 cm Swarm = 1) magma motion? (most were harmonic)Swarm = 1) magma motion? (most were harmonic) 2) stress from deeper magma source pushing 2) stress from deeper magma source pushing
allall Swarms Swarms shallower by mid May, 1982 shallower by mid May, 1982
steam ventssteam vents formal notice of volcanic hazardformal notice of volcanic hazard later found not a strict progression of shallowing e'quakes later found not a strict progression of shallowing e'quakes
& latest May ones, although shallowest, were over a & latest May ones, although shallowest, were over a broad areabroad area
Huge Rhyolitic EruptionsHuge Rhyolitic Eruptions Long ValleyLong Valley
Why concern??Why concern?? 760,000 yr old eruption was 760,000 yr old eruption was HUGEHUGE Bishop ash fall was hundreds of meters thick locally & Bishop ash fall was hundreds of meters thick locally &
weldedwelded Ignimbrite = Bishop TuffIgnimbrite = Bishop Tuff
1 meter thick over 75 km radius & 1 cm at Kansas 1 meter thick over 75 km radius & 1 cm at Kansas City!!City!!
Poisonous GasesPoisonous Gases Mostly steam, but also Mostly steam, but also
COCO22, CO, SO, CO, SO22, H, H22S S Rarely a problem since Rarely a problem since
diffusesdiffuses
Japan has gas monitors and sirens for some Japan has gas monitors and sirens for some volcanoes volcanoes
Lake Nios, Cameroon, 1986 Lake Nios, Cameroon, 1986
Sulfur dioxide from Mt. Pinatubo, 1991
Lake Nios, Cameroon, 1986Lake Nios, Cameroon, 1986 Slow release by Slow release by
dormant volcano dormant volcano bottom of lake in bottom of lake in crater crater
Suddenly overturned Suddenly overturned and released COand released CO22
which is heavy and which is heavy and hugged the ground hugged the ground suffocating ~2000suffocating ~2000
Mudflows and debris (coarser) flows: lahars (Java)Mudflows and debris (coarser) flows: lahars (Java) Ash & other Ash & other tephratephra become water saturated become water saturated
The premier threat of NW volcanoes: so much snow The premier threat of NW volcanoes: so much snow and ice to meltand ice to melt
They can be huge (Redoubt 1990 They can be huge (Redoubt 1990 flow with flow with discharge ~ Mississippi at flood)discharge ~ Mississippi at flood)
Mudflows and debris (coarser) flows: lahars (Java)Mudflows and debris (coarser) flows: lahars (Java) Osceola (5000 yrs) and Electron mudflows from Mt Osceola (5000 yrs) and Electron mudflows from Mt
RainierRainier
Hundreds of Hundreds of thousands of people thousands of people live in threatened live in threatened valley bottoms valley bottoms
Little warning Little warning (unlike floods)(unlike floods)
Predicting Volcanic ActivityPredicting Volcanic Activity
Some general patterns, but usually pattern for one Some general patterns, but usually pattern for one volcano not so good for anothervolcano not so good for another Seismic activitySeismic activity
earthquakes are earliest warningearthquakes are earliest warning harmonic tremors = magma motionharmonic tremors = magma motion may die to quiescent or may be calm before stormmay die to quiescent or may be calm before storm
Geophysical MonitoringGeophysical Monitoring shallow chamber usually fills prior to eruption shallow chamber usually fills prior to eruption surface surface swelling and tiltswelling and tilt heat: IR imagesheat: IR images magnetic fields hot springs and hydrologic activitymagnetic fields hot springs and hydrologic activity
Predicting Volcanic ActivityPredicting Volcanic Activity GasesGases
Changes in gas geochemistry (relative amounts of steam, Changes in gas geochemistry (relative amounts of steam, COCO22, SO, SO22, etc), etc)
Worked at Mt St. Helens and Pinatubo (use at MSH Worked at Mt St. Helens and Pinatubo (use at MSH predicted 13 eruptions)predicted 13 eruptions)
Geologic HistoryGeologic History Mapping of volcanic rocks and deposits characterize Mapping of volcanic rocks and deposits characterize
common eruption typescommon eruption types Example: > 90% of Kilauea surface covered by lava in Example: > 90% of Kilauea surface covered by lava in
last 1500 yrs. last 1500 yrs. If had known, may never have built KalapanaIf had known, may never have built Kalapana
Best for long-range (of course)Best for long-range (of course)