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

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

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

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

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

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

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?

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.

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)

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.

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

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

GEOPHYSICAL OBSERVATIONS: Thermal Anomalies (Temperature)

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

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!!!!

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

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

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