Volcanic hazards Flashcards
What are the volcanic hazards?
Lava flows
Lahars (mudflows)
Glacial floods (Jokulhlaups)
Tephra
Toxic gases
Acid rain
Nuees Ardentes
What is a lava flow?
Can flow quickly or slowly depending on viscosity
Silica makes lava viscous (common in explosive eruptions)
What is a lahar?
Melting ice at high latitudes, mixed with mud/sediment
What is a glacial flood?
Glaciers or ice sheets quickly melt and a large amount of water is discharged
What is tephra?
Any rock ejected from the volcano
Can CO2 be considered a toxic gas?
Yes - it can replace oxygen as it is heavier
What is acid rain?
Sulfur dioxide are released into the atmosphere
What is a nuees Ardentes?
AKA pyroclastic flow
Clouds of burning hot ash/gas that collapses down the volcano at high speed
Average speed is 60mph
How do we measure the magnitude of earthquakes?
Vulcanicity measured with the VEI. The more powerful, the more explosive.
Logarithmic scale from VEI 2 and onwards.
Factors: how much tephra, duration of eruption, height of tephra ejection.
How frequent are volcanic eruptions?
50-60 volcanoes erupt monthly.
Some volcanoes erupt constantly.
Higher frequency usually means they’re effusive; low frequency means explosive.
Classed as either active, dormant or extinct.
How regular (the same) are volcanic eruptions?
Eruptions on each type of boundary are similar
There are anomalies
How can we use the regularity of eruptions to pre-plan?
Regularity (same action on the same boundaries) can help us estimate how often eruptions will happen
Seismic activity, gases and elevation monitoring can indicate imminent eruption
Primary and secondary environmental impacts of volcanic hazards
Primary - ecosystem damage, wildlife killed
Secondary - water contaminated by acid rain, enhanced greenhouse effect
Primary and secondary economic impacts of volcanic hazards
Primary - Business and industry destroyed/disrupted
Secondary - Jobs lost, tourist industry profits
Primary and secondary social impacts from volcanic hazards
Primary - people killed, homes destroyed from Nuees Ardentes
Secondary - Fires, mudflows, floods, hazard trauma/PTSD, homelessness
Primary and secondary political impacts from volcanic hazards
Primary - government buildings destroyed
Secondary - conflicts demanding government response: food shortage, insurance.
How can we prevent volcanic hazards?
Land use zoning
How can we prepare for volcanic hazards?
Monitoring - warnings issued
Educational campaigns
Planned evacuation
Training response teams
How can we mitigate volcanic hazards?
Concrete blocks to channel lava away from urban areas
Make buildings resilient to mudflows or ash pileup
Evacuation and exclusion zones
Emergency aid/rescue
How can we adapt to volcanic hazards?
Encourage tourism and capitalize on it - more funding
Be in a sector that won’t be affected by the hazard
What type of plate boundary is the Montserrat volcano on?
Destructive - North American subducting under Caribbean.
What kind of volcano is Soufriere Hills? What type of lava does it produce?
Composite cone - Andesitic magma (viscous, explosive)
What were the warning signs for the Mount Soufriere eruption?
1995 - small earthquakes and eruptions
Lava dome grew
June 1997 - small earthquakes caused pyroclastic flow, burying the ‘Spanish Point’ community
September 1997 - 74 eruptions (magma)
What were the volcanic hazards of the Montserrat eruption?
4-5 million metres cubed of material released in 20 minutes
Lava dome collapse
Pyroclastic flow and lahars
