Hazard management- Monitoring and risk assessment Flashcards
In the 20th centtury, how many deaths were due to volcanic eruptions?
96,000
What did 91% of the fatalities from volcanic eruptions in the 20th century result from?
Pyroclastic flows
Lahars
Tsunamis
Famine and epidemic disease
What 3 things does short term forecasting and monitoring involve?
Volcano monitoring in real time
Eruption and forecasting and prediction
Volcanic emergency management and planning- local authorities, civil defense
What 3 things does long term forecasting and monitoring involve?
Identify the high-risk volcanoes
Map and indentify past volcanic hazards to prepare for volcanic hazard
Long-term forecasts
What does volcanic monitoring include?
Seismic monitoring
Ground deformation
Microgravity
Magnetic field
Volcanic gases
Temperature
Hydrology
Why does volcanic monitoring include seismic monitoring?
Moving magma and gases cuases rocks to break- causing high frequency earthqaukes or low frequency earthqaukes/tremors
What does short period/high frequency tremors suggest?
Fractures due to expansion of magma chamber
What does harmonic (low frequency) tremors suggest?
Magma flows through feeder conduits (water/magma channels)
What is a seismometer used for?
Used to record volcanic-related earthquakes
Tell us information about the tremors- timing, location, depth and magnitude
What is ground deformation?
Changes to the surface of the volcano tells us what is happening below
How do you measure ground deformation?
Requires precise surveying techniques
More accurate with recent advances in lasers
How does geodetic levelling work?
Measures elevation differences between benchmarks (gps points)
How does a tiltmeter work?
Precise levelling, displacements as small as 1-2cm can be determined
How does an EDM (electronic distance meter) work?
Sends and recieves an electromagnetic signal to measure the distance when comparing the transmitted and received signal
What is ground inflation?
Gradual changes in the volcano surface, and can occur over a period of months and years
What is ground inflation?
Gradual changes in the volcano surface, and can occur over a period of months and years
What is ground deflation?
Sudden change in the volcano surface, as the magma chamber is emptied associated with an eruption
What does volcanic gas monitroring include?
Collecting ground samples
Taking airbourne measurements of eruption plumes
Analysis of water chemistry
(all for gas contents)
What gas recordings help monitor gas explosions/releases from volcanic eruptions?
Sulfur dioxide (SO2)
What does temperature (thermal) monitoring include?
Infrared imaging to detect and analyse active areas of a volcano
Can differentiate hot from cold eruptibe events
Highlights active faults
What does hydrology monitoring include?
Monitoring sediment erosion, transport and deposition, water temperature, found vibrations (mudflows, lahars) and precipitation
As volcanoes interact with the local hydrology
What assumption is made when analysing the risk/mapping volcanic hazards?
The geological past provides a useful guide to future activity
What information is crucial to identifying and mapping volcanic hazards?
Careful stufy of geological record of volcanoes and their surroundings
Mapping distribution and extent of lava and pyroclastic flows
Dating events to help understand the frequency of eruptions- predict when they will next occur
Why is it important to identify and map volcanic hazards?
Helps to plan for future events, know who needs to be evacuated- reducing deaths
Understanding the volcanic environment that has formed can inform where to build/not build
Combination of early warning systems can inform emergency managment agencies- best preparedness (all the info about the hazard) produce risk assessed cover map of landscape
