Page 40 - Volcano and Geothermal Tourism

Introduction 17

Table 1.4 Volcanic hazards
Type of volcanic hazard Potential dangers and effects
Acid rain Rain turns acidic when falling through clouds of volcanic gas or acid particle emissions. Eye and skin
irritant, affects vegetation and water quality (Hansell et al, 2006).
Ash Of all eruptive hazards ashfall can affect the most people because of the wide areas that can be covered
(Blong, 1996). Ash is a collective term for fine pyroclasts of a size <2mm diameter, that can affect the
respiratory and cardiovascular systems and is irritating to eyes and skin (Hansell et al, 2006). Ash can
also destroy vegetation, crops, block roads, block drains, watercourses and cause damage to equipment.
In large eruptions, the danger to aircraft is considerable and particles can impact on climate and weather
(Chester et al, 2001).
Ballistics, bombs, blocks Rocks and lava lumps ejected during major and minor eruptions causing injuries from impact and burns
(Hansell et al, 2006).
Gas emissions Volcanic gases present hazards to human health and vegetation. The effects of SO , HCl, CO and H S
2
2
2
are at their most severe close to a volcano or a hydrothermal vent. Hydrogen sulphide (H S) also occurs
2
near some hot springs and has caused fatalities in several countries.
Jökulhlaup Icelandic name for glacier burst, causing severe flooding by melt water, when a volcano erupts
underneath a glacier or an ice cap.
Lahar, landslide, mudslide Gravity-controlled mudflows carrying volcanic debris and ash mixed with water downhill. Dangerous
because of their great speed, embedded large boulders and ability to wash away foundations of bridges
and buildings. They can be triggered a long time after a volcanic eruption through heavy rainfall.
Lava flows Lava flows are molten rock and generally move slowly along paths determined by topography and do not
normally threaten life, because they allow time for evacuation. Lava flows cause destruction through
burial and burning of property and vegetation and can cause thermal burns.
Laze (Lava haze) HCl gas clouds form when lava flows enter the ocean and come in contact with seawater. Affects the
respiratory system, irritates eyes and skin.
Pyroclastic flows Pyroclastic flows and surges (Schmincke, 2006), can travel at several hundred km per hour and can even
jump over ridges uphill. Maximum temperatures in such flows can reach over 800°C and can cause
death, injury, destruction of buildings, impact damage and burial. They are usually caused by either a
dome collapse or the collapse of an eruption column or a lateral blast.
Tephra, air fall deposits They are created when blocks, bombs and lapilli are ejected from a volcanic eruption column or plume
and can be deposited over long distances. The particle size can range from ash (<2mm) and lapilli
(>2mm) to blocks and bombs (>greater than 64mm). Hazard can be severe, depending on the proximity
to the volcano. Injuries and death through impact are possible.
Tsunami Also known as ‘sea wave’ or ‘harbour wave’ and is caused by the displacement of water in the ocean by
an earthquake or subaqueous eruption. A tsunami is not a tidal wave but can inundate vast stretches of
low lying coastal areas.

Source: Compiled by author from various sources including Chester et al, 2001; Francis and Oppenheimer, 2004; Hansell et al, 2006

or steam vents, acid rain and ground deformation the side of caution to avoid unpleasant or even life
can make for rather unpleasant experiences. In threatening experiences.
some areas unreliable and unqualified tour guides It is not just tourists that can get caught by
offer mountain tours with great views, assuring unexpected eruptions; this has happened in the
the tourists that there is no danger involved and past to experienced and trained scientists working
halfway up the mountain everybody has to run for on active volcanoes because essential information
their lives. These things have happened on various appears to have been either misinterpreted or even
occasions and it is therefore paramount to err on ignored (Bruce, 2001), resulting in the death of

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