1. Key Question: How are volcanic eruptions predicted and how successful has prediction been?
Key Words
COSPEC
Geochemical / Geophysical
Tiltmeters
Seismometers
Pick one method from the
diagram and try and explain how it might predict an eruption

2. To Start: In pairs draw out as many features of a shield and composite cone volcano as possible
You need to sit back to back
You can either do 1 type each and see who gets the most points or draw the same one and see who’s version is best

3. Types of Volcano
Characteristics
High temps – 1100oC
a) Shield
Frequent ‘effusive’ eruptions (non-violent)
Red Volcanoes
Wide base and low angled – 6 or 7o
Low viscosity runny lavas (Basalts)
Low silica magma
(basic 45-54%)
Lavas spread over large distances
Examples: Iceland and Mauna Loa in Hawaii

4. Made of layers of lava and ash
b) Composite Cone
Characteristics
Explosive grey eruptions
Examples: Etna and vesuvious, Italy
High – can exceed 5000m (Andes)
Steep sided
May have crater lake or volcanic plug of viscous lava
May have parasitic cones
High viscosity lavas (andesite and rhyolite)
Higher Silica Content >52%
Layers of lava and ash / pyroclastic flows
Higher Silica Magma Chamber

5. Classify those on your sheet into the appropriate groups
Volcanic Prediction
1. Geochemical
Classify those on your sheet into the appropriate groups
2. Geophysical
3. Geological Observations

6. Now explain how volcano type can be used to predict the level of risk
GEOLOGICAL OBSERVATIONS: Volcano Type
Now explain how volcano type can be used to predict the level of risk
By looking at volcano type and eruption history from past deposits geologists can begin to work out the type of hazards likely to occur
Grey are generally more likely to erupt violently

7. GEOLOGICAL OBSERVATIONS: Time Since Last Eruption
Vesuvius 1944
The longer the time dormant, the greater the chance of a violent eruption!
This can be worked out from past historical records or from past deposits.
Why do you think time may increase the violence of an eruption?

8. GEOLOGICAL OBSERVATIONS: Lava Escape / increase in activity
Also an increase in volcanic activity can mean an eruption is
approaching!
The presence of lava doming (dacite) may indicate a pressuring magma chamber. E.g. Pinatubo 1991.

9. Seismometers can detect vibrations caused by:
GEOPHYSICAL OBSERVATIONS: Seismic Activity
Seismometers can detect vibrations caused by:
fracture of rocks (tectonic tremors)
movement of magma or gas bubbles (volcanic tremors)

10. GEOPHYSICAL OBSERVATIONS: Seismic Activity
Tectonic tremors occur when the hot rising magma pushes against the surrounding rocks, fracturing occurs setting off high-frequency seismic events.

11. GEOPHYSICAL OBSERVATIONS: Seismic Activity
These low-frequency events (2-3 vibrations per second) are caused by magma flowing up tubes and vents in the volcano.
Seismometer shows a continuously vibrating signal also known as an harmonic tremor

12. GEOPHYSICAL OBSERVATIONS: Uplift and Tilting
Rising magma makes the ground swell and tiltmeters can detect the changes e.g. St
Helen’s 1980

13. GEOPHYSICAL OBSERVATIONS: Thermal Anomalies (Temperature)

14. Detected at fumaroles or with COSPEC (correlation spectrometer).
GEOCHEMICAL OBSERVATIONS: Volcanic Gas Emissions
Detected at fumaroles or with COSPEC (correlation spectrometer).

15. Magma degassing at depth!
GEOCHEMICAL OBSERVATIONS: Volcanic Gas Emissions
Carbon Dioxide (CO2) =
Sulphur Dioxide (SO2) =
Magma degassing at depth!
Magma rising to surface and eruption immanent
A sudden < means vent is block and pressure building up!!!!

16. Volcanic Prediction Techniques
Rock Types and Past Deposits e.g. lahars and pyroclastic flows and ash
Volcanic Gas (C02 and SO2)
Thermal Anomalies
Volcanic Prediction Techniques
Volcano Type
Ground Deformation
Lava Escape
Seismic Activity (tectonic and Harmonic)
Increase in Activity

17. Seismic Activity (tectonic and Harmonic)
Rock Types and Past Deposits e.g. lahars and pyrolclastic flows and ash
Rock Types and Past Deposits e.g. lahars and pyrolclastic flows and ash
Volcanic Gas (C02 and SO2)
Volcanic Gas (C02 and SO2)
Seismic Activity (tectonic and Harmonic)
Seismic Activity (tectonic and Harmonic)
Ground Deformation
Ground Deformation
Thermal Anomalies
Thermal Anomalies
Volcano Type
Volcano Type
Lava Escape
Lava Escape
Increase in Activity
Increase in Activity

18. Summary: To summarise, think back to earthquakes and compare the success of earthquake prediction to volcano prediction. Which is most successful, why?
EQ prediction
‘Volcano prediction is much more successful than EQ as before a major eruption we can detect geophysical and geochemical changes in the earth’
Volcano Prediction