Title: Volcanic Hazards p. 138-140, web reading
1Volcanic Hazardsp. 138-140, web reading
- Volcano Facts
- Volcano Hazards
- Fall processes
- Flow processes
- Other types
- Predicting Volcanic Eruptions
2Giant Caldera Volcano Yellowstone
3Toba, IndonesiaThe Biggest Eruption?
4Toba, 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 3-5C
- Might have affected human evolution
5Volcanic Eruptions over the last 10,000 years
- 1300 active volcanoes
- 550 eruptions (lt 2000 yrs)
- lt10 potentially destructive volcanoes have been
studied in detail
800 million people worldwide _at_ risk gt50 of
worlds volcanoes in nations with per capita GDP
lt20 US
6Volcanic Hazards
Fall Processes Flow Processes
Web reading
7Lava Flows
Basaltic lava (low viscosity) Usually slow moving
(lt10 mph) Rarely life threatening
8Nyiragongo volcano, Congo Goma, Jan. 19, 2002
9Nyiragongo volcano, Congo Goma, Jan. 19, 2002
10Pyroclastic Flows
High density mixture of hot ash, rock, and hot
gases Temp. gt500C Velocity gt 80-100 mph
11Pyroclastic Flows
12Mt Unzen, Japan
- Pyroclastic flows
- Eruption in June, 1991, killed 40 journalists and
3 experienced volcanologists
13Ash Falls (Tephra Falls)
- 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)
Mount Pinatubo, Philippines June 1991
14Ash fall in Rabaul, Papua New Guinea, 1994
15Volcanic AshDanger 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
16Poisonous Gas Emissions
CO2, SO2, HCl, HF H2S
17Poisonous Gas EmissionsLake Nyos, Cameroon (1986)
Controlled degassing, 1995
Lake Nyos
River of CO2 50 m thick layer
Bottom of lake Saturated in CO2
CO2 gas from Magma
18Volcanic Landslides
Mt. St. Helens May 18, 1980 Debris Flow 2.3 km3
of material
Largest debris landslide in recorded history
19The 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.
20Mt. St. Helens May 18, 1980
Figure 5.10
21Mt. St. Helens
22Lahars (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
23Nevado del RuizNov. 13, 1985
- Canyon that channeled the lahar that destroyed
Armero and killed 23,000 people
24Town of Armero
The November 13, 1985 lahar from Nevado del Ruiz
25(No Transcript)
26Volcano Monitoring and Prediction
Goal Prevent a Volcanic Crisis from turning into
a Volcanic Disaster
27Volcanoes of the Lower 48
28Volcano Monitoring and Prediction
Long-Term based on Historical Records and
Geologic History Age-dating of volcanic
deposits ? Eruption Frequency Types and amounts
of eruption products ? Size of Eruption
29Volcano Monitoring and Prediction
Short Term systematic observations of volcanos
visible and subsurface activity
Seismicity Ground tilt Gas emissions
30Rising Magma
- Ground Deformation
- Rising magma and increasing pressure exerted by
gases often cause volcanoes to deform, or swell,
before an eruption
31Rising Magma
Moving Magma and Volcanic Fluids Trigger
Earthquakes
High pressure causes rocks to break, triggering
earthquakes
Rising magma and volcanic gases exert pressure
Magma rises into reservoir beneath volcano
32Forecasting Volcanic Activity
- Ideal Forecast includes
- Location
- Timing
- Character of eruption and magnitude
33Forecasting Volcanic Activity
- Ideal Forecast includes
- Location
- Timing
- Character of eruption and magnitude
- Effective Forecasting involves
- Scientists
- Public officials
- News media
- Informed Public
Friday Video Path of a Killer Volcano Mt.
Pinatubo eruption of 1991