Types of Disasters and Their Consequences

Volcanic Eruptions

Volcanic activity involves the explosive eruption or flow of rock fragments and molten rock in various combinations of hot or cold, wet or dry, and fast or slow. Extremely high temperature and pressure cause the mantle, located deep inside the earth between the molten iron core and the thin crust at the surface, to melt and become liquid rock or magma. When a large amount of magma is formed, it rises through the denser rock layers toward the earth's surface. Magma that has reached the surface is called lava. Volcanic hazards vary in severity depending on the size and extent of the eruption and whether the eruption is occurring in a populated area. Volcanos are classified by similar characteristic behavior, and have been called "Strombolian," "Vulcanian," "Vesuvian," "Pelean," "Hawaiian," and others. When active, volcanoes may exhibit only one characteristic type of eruption or a sequence of types.

A volcano may begin to show signs of unrest several months to a few years before an eruption. Accurate long-term predictions, specifying when and where an eruption is most likely to occur and what type and size eruption should be expected are not possible. Warnings that an eruption is hours to days away are possible because eruptions are preceded by such changes in a volcano's earthquake activity, ground deformation, and gas emissions over a period of days to weeks.

In the United States, volcano warnings are made through a series of alert levels that correspond generally to increasing levels of volcanic activity. Each increase in the alert level helps authorities gauge and coordinate their response to a developing volcano emergency.

Depending on the location of the volcano (California, Alaska, Pacific Northwest or Hawaii), different alert levels² are used to provide volcano warnings and emergency information regarding volcanic unrest and eruptions. Different alert levels are used because volcanoes exhibit different patterns of unrest in the weeks to hours before erupting, volcano hazards differ requiring a warning scheme that addresses specific volcano hazards, and there is variability in the intensity of monitoring U.S. volcanoes. The Volcanic Explosivity Index or VEI is the eruption magnitude scale used to rate the eruption. The VEI considers the plume height, the volume of magma, the classification, and how often it erupts. The VEI ranges from VEI 0 to VEI 8. Any eruption that occurs anywhere will rate at least a VEI 0 on the scale and have less than 10,000 cubic meters of ejecta, which includes lava and ash. VEI 3 volcanoes have as much as 100 million cubic meters of ejecta. A VEI 8 volcano must spew out a minimum of one trillion cubic meters of ejecta.

Many kinds of volcanic activity can endanger the lives of people and property located both close to and far away from a volcano. The range of adverse health effects is quite broad and extensive. Immediate, acute, and nonspecific irritant effects have been reported in the eyes, including corneal abrasions, nose, skin, and upper airways of persons exposed to volcanic dusts and ash particles. Victims can have exacerbation of their asthma symptoms and can asphyxiate due to inhalation of ash or gases. There is the potential of injuries from blasts and projectile of rock fragments. Lacerations can occur if sound waves shatter windows and break glass. Volcanic flow can set homes on fire causing thermal injuries including death. Victims can experience trauma due to fallen trees or rocks or the collapse of buildings under weight of the ash. Foraging animals may be unable to find adequate supply of food or water. Indoor air radon levels may be elevated. Flooding and pooling of water secondary to debris or obstruction of waterways can lead to spread of infectious disease. Finally, victims can experience anxiety, depression, or post traumatic stress disorder.

² Also referred to as status levels, condition levels, or color code.

• Collaborate with emergency-management specialists to develop effective warning schemes.
  
  

• Participate in volcano-emergency planning workshops and emergency-response exercises.
  
  

• Prepare educational materials, including fact sheets, booklets, video programs, and maps.
  
  

• Designate areas for evacuation and evacuate when indicated.
  
  

• Provide emergency air-monitoring equipment for detecting toxic gases.
  
  

• Stockpile and distribute masks and eye shields or goggles, where indicated.
  
  

• Prepare for breakdown of water systems.
  
  

• Encourage protection by remaining inside sturdy houses with shuttered windows when evacuation not indicated or possible.
  
  

• Strengthen roofs of building with supports or take shelter in most resistant part of the building.
  
  

• Stay indoors during worst conditions.

American Public Health Association © 2005  American Public Health Association

Cite this: Types of Disasters and Their Consequences - Medscape - Sep 20, 2005.