Page 188 - Fundamentals of Physical Volcanology

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11 Volcanic hazards and

volcano monitoring

11.1 Introduction starts very close to a habitation where people are
sleeping, or the people involved are ill or infirm,
The historic and archeological record is littered they are likely to be able to escape, as long as they
with examples of disasters caused by volcanic erup- walk away from the downslope path that the flow is
tions: the burial of Pompeii and Herculaneum following. Vastly more people have been killed by
by the AD 79 eruption of Vesuvius, the collapse of the products of explosive eruptions than by being
the Minoan civilization as a result of an eruption at overtaken by lava flows.
Santorini around 1650 BC, and the devastation pro- Lava flows can, however, cause the total destruc-
duced by the tsunami waves generated during the tion of property. In some cases flows that are thick
eruption of Krakatoa in 1883. This chapter looks at enough do this by simply burying buildings, gener-
the range of hazards that can be caused by volcanic ally crushing them in the process (Fig. 11.1). In other
eruptions, at how scientists try to assess the hazards cases a building may be strong enough to withstand
presented by any one volcano, at methods used to the pressure exerted on its walls as a flow piles up
monitor active volcanoes, and at successes and fail- against it, and thus the flow may eventually just sur-
ures in predicting volcanic activity. round the building, but the intense heat radiated
from the flow will ignite virtually any flammable
material and so the building will burn (Fig. 11.2).

11.2 Types of volcanic hazard Given the slow advance rate of flows, it is common

Volcanic eruptions can present a wide range of haz-
ards to human life and property and to the wider
environment. Some hazards are direct, such as the
destruction of property by lava flows or death
caused by being overrun by a pyroclastic density
current. Other hazards are indirect, such as starva-
tion due to destruction of crops or changes in clim-
ate caused by volcanic activity (see Chapter 12).

11.2.1 Lava flows
Lava flows do not generally cause the deaths of
people directly. This is because, except in the cases
Fig. 11.1 Buildings in the village of Kalapana on the
of fluid basaltic flows very near the vent, the vast
southeast flank of Kilauea volcano, Hawai’I, extensively
majority of lava flows do not move as fast as moder- damaged by lava flows. (Photograph by Jim Griggs, courtesy
ately fit people can walk. Thus, unless an eruption of U.S. Geological Survey, Hawaiian Volcano Observatory.)