volcanic hazards p. 138-140, web reading
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Volcanic Hazards p. 138-140, web reading. Volcano Facts Volcano Hazards Fall processes Flow processes Other types Predicting Volcanic Eruptions. Yellowstone Old Faithful. Ground collapse ~ Area of NYC Material ejected ~1000 km 3. Ash Fall. Giant Caldera Volcano: Yellowstone. - PowerPoint PPT PresentationTRANSCRIPT
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Volcanic Hazardsp. 138-140, web reading
• Volcano Facts• Volcano Hazards
• Fall processes• Flow processes• Other types
• Predicting Volcanic Eruptions
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YellowstoneOld Faithful
Giant Caldera Volcano: Yellowstone
Ground collapse ~ Area of NYCMaterial ejected ~1000 km3
Ash Fall
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Toba, IndonesiaThe Biggest Eruption?
• 75,000 years ago
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Toba, IndonesiaThe Biggest Eruption?
• Caldera diameter 100x35 km• Volume erupted 2,800 km3
– 10 cm of ash fell in India, 3000 km away
• Volcanic winter for a decade– With global cooling 3-5°C
• Might have affected human evolution
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Volcanic Eruptions over the last 10,000 years
• 1300 active volcanoes• 550 eruptions (< 2000 yrs)• <10% potentially destructive volcanoes
have been studied in detail
~800 million people worldwide @ risk>50% of world’s volcanoes in nations with per capita GDP <20% US
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Volcanic Hazards
Fall ProcessesFlow Processes
Web reading
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Lava FlowsBasaltic lava (low viscosity)Usually slow moving (<10 mph)Rarely life threatening
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Nyiragongo volcano, CongoGoma, Jan. 19, 2002
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Nyiragongo volcano, CongoGoma, Jan. 19, 2002
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Pyroclastic Flows
High density mixture of hot ash, rock, and hot gases Temp. >500CVelocity > 80-100 mph
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Pyroclastic Flows
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Mt Unzen, Japan• Pyroclastic flows• Eruption in June,
1991, killed 40 journalists and 3 experienced volcanologists
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Ash Falls (Tephra Falls)
Mount Pinatubo, Philippines June 1991
•can cover large areas for days to weeks•ash will last on the ground for months to years•making land and water unusable•provide material for future hazards (lahars)
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Ash fall in Rabaul, Papua New Guinea, 1994
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Volcanic Ash–Danger to Aircraft
Volcanic ash can be a serious hazard to aviation even thousands of miles from an eruption. Airborne ash can diminish visibility, damage flight control systems, and cause jet engines to fail.
USGS
Part of a 747 engine
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Poisonous Gas Emissions
Lake Nyos, Cameroon
CO2, SO2, HCl, HFH2S
Volcanic Smog-Vog
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CO2 gas from Magma
Bottom of lakeSaturated in CO2
Lake Nyos
Poisonous Gas EmissionsLake Nyos, Cameroon (1986)
“River” of CO2
50 m thick layer
Controlled degassing, 1995
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Volcanic LandslidesMt. St. HelensMay 18, 1980Debris Flow2.3 km3 of material
Largest debris landslide in recorded history
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The avalanche traveled approximately 15 miles downstream at a velocity exceeding 150 mph. It left behind a hummocky deposit with an average thickness of 150 feet and a maximum thickness of 600 feet.
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Figure 5.10
Mt. St. Helens May 18, 1980
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Mt. St. Helens
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Lahars (Mudflows)
• A mixture of volcanic fragments and water
• Mudflows are channeled along valleys on the flanks of volcanoes.
• Mudflows have the consistency of wet concrete and move at high speeds (up to 20-60 mph).
Pinatubo
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Nevado del RuizNov. 13, 1985Canyon that
channeled the lahar that destroyed Armero and killed 23,000 people
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The November 13, 1985 lahar from Nevado del Ruiz
Town of Armero
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Volcano Monitoring and Prediction
Goal: Prevent a Volcanic Crisis from turning into a Volcanic Disaster
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Volcanoes of the “Lower
48”
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Volcano Monitoring and Prediction
Long-Term based on Historical Records and Geologic History
Age-dating ofvolcanic deposits Eruption Frequency
Types and amounts oferuption products Size of Eruption
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Volcano Monitoring and PredictionShort Term: systematic observations of volcano’s visible and subsurface activity
SeismicityGround tiltGas emissions
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Rising MagmaGround DeformationRising magma and increasing pressure exerted by
gases often cause volcanoes to deform, or swell, before an eruption
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Rising Magma
Magma rises into reservoir beneath volcano
Rising magma and volcanic gases exert pressure
Moving Magma and Volcanic Fluids Trigger Earthquakes
High pressure causes rocks to break, triggering earthquakes
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Forecasting Volcanic Activity• Ideal Forecast includes
– Location– Timing– Character of eruption and
magnitude
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Forecasting Volcanic Activity• Ideal Forecast includes
– Location– Timing– Character of eruption and
magnitude
•Effective Forecasting involves•Scientists•Public officials•News media•Informed Public
Friday VideoPath of a Killer VolcanoMt. Pinatubo eruption of 1991