Primary Hazards
- Although they are all unique, volcanic eruptions have common hazards
- Primary (a direct result of the eruption)
- Secondary (a result of the primary hazards)
Diagram to show volcanic hazards
- Tephra – solid material of varying sizes that is ejected by a volcano – ranges from ash (less than 2mm in diameter) to volcanic bombs (more than 64mm)
- Ash fallout – large quantities of ash carried by the wind and deposited on the ground
- It can travel many km, causing respiratory problems, injuries, damage, deaths and disruption to transport
- E.g. the 2010 Eyjafjallajökull eruption in Iceland produced an ash cloud that disrupted air travel in Europe for several weeks
Extent of ash cloud from 2010 Eyjafjallajökull eruption
- Pyroclastic flow (also known as nuée ardente) - a super-heated mixture of gas and tephra that flows at speeds of up to 700 km per hour
- This is one of the deadliest volcanic hazards as they can travel long distances and destroy everything in their path
- E.g. when Fuego volcano erupted in Guatemala in 2018, pyroclastic flows destroyed several nearby towns
- Lava flow – lava flows travel at different speeds depending on slope, temperature and viscosity
- Most move slowly enough that they are not a risk to human life but can cause significant damage to property and infrastructure
- The fastest flows can reach speeds of up to 60 mph
- In the 2021 eruption of Mount Nyiragongo in the Democratic Republic of Congo, lava flows travelled almost 10km destroying properties and killing over 30 people
- Volcanic gases – eruptions can release large quantities of gases such as sulphur dioxide and carbon dioxide
- They are hazardous to human health causing respiratory problems and deaths
- E.g. Kilauea in Hawaii (USA) releases large amounts of sulphur dioxide leading to air quality alerts and health warnings for residents
