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close this bookAn Overview of Disaster Management (Department of Humanitarian Affairs/United Nations Disaster Relief Office - United Nations Development Programme , 1992, 136 p.)
close this folderChapter 4. Natural hazards
close this folderCharacteristics of particular hazards and disasters 1
View the document(introduction...)
View the documentEarthquakes
View the documentTsunamis
View the documentVolcanoes
View the documentLandslides
View the documentTropical cyclones
View the documentFloods
View the documentDroughts
View the documentEnvironmental pollution
View the documentDeforestation
View the documentDesertification
View the documentPest infestations
View the documentEpidemics
View the documentChemical and industrial accidents
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Causal phenomena

Magma pushed upward through volcanic vent by pressure and effervescence of dissolved gases.

General characteristics

Types of volcanoes are cindercones, shield volcanoes, composite volcanoes and lava domes.
Magma flowing out onto surface is lava and all solid particles ejected are tephra.
Damage results from type of material ejected such as ash, pyroclastic flows (blasts of gas containing ash and fragments), mud, debris, and lava flows.


Study of the geological history of volcanoes mainly located in a clearly defined volcanic belt, along with seismic activity and other observations, may indicate an impending volcano. No reliable indicator has been discovered and precursory signs do not always occur.

Factors contributing to vulnerability

Settlements on the flanks of volcanoes
Settlements in the historical paths of mud or lava flows
Structures with roof designs not resistant to ash accumulation
Presence of combustible materials
Lack of evacuation plan or warning systems

Typical adverse effects

Casualties and health - Death from pyroclastic flows, mud flows and possibly lava flows and toxic gases. Injuries from falling rock, bums; respiratory difficulties from gas and ash.
Settlements, infrastructure and agriculture - Complete destruction of everything in the path of pyroclastic, mud or lava flows; collapse of structures under weight of wet ash, flooding, blockage of roads or communication systems
Crops and food supplies - Destruction of crops in path of flows, ash may break tree branches, livestock may inhale toxic gas or ash; grazing lands may be contaminated.

Possible risk reduction measures

Land use planning for settlements around volcanoes
Protective structural measures

Specific preparedness measures

National volcanic emergency plans
Volcano monitoring and warning system
Training for government officials and community participation in search and rescue, fire fighting

Typical post-disaster needs

Warning and evacuation; medical assistance, search and rescue; provide food, water and shelter; relocate victims; provide financial assistance

Impact assessment tools

Aerial and ground surveys to assess damage; evaluation of evacuation plan and emergency response