Prediction of Hazard Events (AQA A Level Geography)

Frequency & Regularity of Hazards

• Volcanic eruptions occur with varying frequency and regularity depending on the type of volcano and its location

  • Shield volcanoes tend to be found at constructive plate margins and are typified by high frequency, low magnitude eruptions

  • Stratovolcanoes tend to be found at destructive plate margins and are typified by low frequency, high magnitude eruptions

• Some volcanoes erupt more frequently and regularly than others

  • Mount Stromboli in Italy usually erupts every 20-40 minutes

  • Mount Pinatubo in the Philippines had not erupted for around 500 years before its eruption in 1991

• Scientists study the geological history of volcanoes (e.g. eruptions and gas emissions) to try to predict when the next eruption might occur

• Volcanic eruptions can occur with few warning signs and do not necessarily follow historical patterns

Predicting Volcanic Events

• There are warning signs before most volcanic eruptions

• Volcanologists (scientists who study volcanoes) monitor changes using GPS, tilt meters, satellites, seismometers and gas detection

• Signs of an eruption include:

  • Magma rising which can be detected by heat sensors and satellites

  • Ground deformation as rising magma causes bulges

  • Increased emissions of sulphur dioxide and other gases

  • Increased seismic activity caused by magma movement detected by seismometers