1. List three gases released as part of a volcanic eruption.
2. What is tephra? 3. What is a pyroclastic flow? 4. List two differences between shield and composite volcanoes.
KEYWORDS
geothermal energy global cooling lahar
Mount St Helens Mount Vesuvius nuée ardente Pompeii
weather patterns
5. List three differences between acidic and basic lava.
6. Name and give examples of two types of hydrothermal vent.
7. What is a batholith?
Human Interaction with Volcanoes
Predicting volcanic eruptions The destructive nature of volcanic eruptions has led to greater study and investment in new technologies to predict when they will occur. Experts use a number of indicators to help them with their predictions:
Historic patterns
The best way to discover the future behaviour of a volcano is to study its past behaviour. Volcanologists look at historical data to predict how often a volcano erupts and the size of the eruption. Geologists examine sequences of layered deposits and lava flows from around volcanoes to discover the pattern and nature of volcanic eruptions.
Cone temperature
Rocks close to the surface of active vents get hotter, as magma rises prior to an eruption. Infrared heat sensors placed at the surface can detect temperature changes and send images to satellites to warn of an impending eruption.
Gas measurements Volcanologists regularly collect samples of gases such as sulphur dioxide (SO2
carbon dioxide (CO2 DID YOU KNOW?
Japan has about 110 active volcanoes – 75% of the world’s total – but only half of these can be monitored intensively and constantly.
) and ) from active vents. Changes in their composition or increases in the rate at which they are emitted can indicate that a volcano is closer to erupting.
Changes in ground level Sensitive instruments called tiltmeters record changes in the shape and steepness of active volcanoes. A bulge is created at the side of a volcano as pressurised magma builds up in its chamber. As the magma rises to the surface, the volcano deflates and returns to its original shape.
Changes to groundwater
Volcanologists monitor water levels and temperatures in local wells to identify any changes in the behaviour of a volcano. As magma moves into a volcano it can cause:
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a rise or fall in the water table; an increase in the temperature of groundwater. Seismic activity
As magma moves into the reservoir prior to an eruption it ruptures already solidified magma in its way. This creates ground movements which can be detected by seismographs placed on the surface of the volcano.
