volcano icon Volcanic Hazards

Numerous types of hazards may result from a volcanic eruption, often simultaneously. The type of hazards that will occur depend on which volcano is erupting ( Gaua, Ambae, Ambrym, Lopevi or Tanna) and the nature of the eruption. For exemple an eruption from Gaua through the crater lake will be different from one at say Lopevi where there is no lake.  Potential hazards from Vanuatu's volcanoes are :

  • Ballistic or bomb
volcanic bombs

Volcanic bombs formed when a volcano ejects viscous fragments of lava during an eruption and can be thrown many meters to kilometers from an erupting vents. They are a significant volcanic hazards, and can cause severe injuries and death to people in an eruption zone.

  • Lahars or mudflow
Lahars

Lahars are "mudflows", mixtures of volcanic ash, blocks and water, formed on volcanoes. The source of a lahar maybe a crater lake, a dam collapse or heavy rainfall washing from the slope of a volcano. People caught in the path of a lahar have a high risk of death from severe injuries. Lahars are extremely destructive causing destruction of buildings, installations and vegetation caught in their path. People should remain at a safe distance.

  • Hot ash flow or pyroclastic flow
pyroclastic

If a large volume of volcanic debris is erupted quickly from a volcano, the eruption column can collapse. As the eruption column collapse it can transform into an outwardly expanding flood of hot solid ejecta in a fluidizing gas cloud, knowing as a pyroclastic flow, or surge. These flows are a common devasting result of certain explosive eruptions;they normally touch the ground and hurtle downhill, or spread laterally under gravity. People caught in the direct path of a flow or surge are most unlikely to survive. The best protection is to evacuate prior to the event.

  • Volcanic gases
gas

Volcanic gases predominately consist of steam and followed by other gases (carbon dioxyde, sulphur and chlorine compounds). Hazardous concentrations of gases are present only very close to the crater (within 1 -2 km). Away from the vent gases pose no more than an irritant or nuisance.

  • Ash fall
ash fall

When a volcano erupts, it will eject a wide variety of material into the air. The fine material (millimetre-sized ash), which is derived from the glass, rock and crystal particules, can carried by currents in the eruption column above the volcano and pass the downwind plume to rain out forming ash deposits. The impacts of ash fall on people, structures and equipements depend largely on ash thickness. For more information regarding the " Volcanic Ash Impacts & Mitigation ", click here.

  • Lava
volcanic lave

Lava flows are streams of molten rock that will travel down valleys on the slopes of volcanoes. The distance they travel depends on the viscosity of the lava, output rates, volume erupted, steepness of the slope, topography and obstructions in the flow path. Lava flows will seldom threaten human life because of their slow rate of movement. However, the steep fronts of flows may became unstable and can collapse, causing small pyroclastic flows. Lava flows will causes total destruction of buildings and other infrastructure in their path.

  • Tsunami
tsunami

Tsunamis are seismic sea waves of long period caused by disturbances on the sea floor. Volcanic tsunami may be produced by landslides or debris avalanches flowing into the sea around an island volcano such as Lopevi.  

 

 
Many of these phenomena will only affect an area very close to the volcano. However, volcanic ash fall can be deposited hundred to thousands of kilometres from its source, making it the product most likely to affect the largest area and the greatest number of people.
 
 For more information on volcano awareness materials for reducing risk of the above volcanic hazards, click here.