Page 28 - Fundamentals of Physical Volcanology

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VOLCANIC SYSTEMS 5

SIB
NAVP
CRFB
DEC
CARI
ETHI

ONTO

KERG

Fig. 1.8 Map showing the global distribution of flood basalt deposits, marked in black. The labeled deposits are: CRFB,
Columbia River Flood Basalts; CARI, Caribbean Flood Basalts; NAVP, North Atlantic Volcanic Province; ETHI, Ethiopian Flood
Basalts; SIB, Siberian Traps; DEC, Deccan Traps; KERG, Kerguelen Plateau; ONTO, Ontong Java Plateau. (Information derived
from fig. 1 in Coffin, M.F. and Eldholm, O. (1994) Large igneous provinces: crustal structure, dimensions, and external
consequences. Reviews of Geophysics, 32, 1–36; and from fig. 5.4 in Courtillot, V. (1999) Evolutionary Catastrophies. The
Science of Mass Extinction. Cambridge University Press, 173 pp.)

eruption which occurred in Iceland in 1783–85. This mals in the pastures. This resulted in the death of
3
eruption produced ∼15 km of lava, with individual half of all livestock in Iceland. The resulting “haze

lava flows exceeding 35 km in length. Eruption famine” caused the death of 22% of the human
3 −1
rates as great as 8700 m s have been estimated population through a combination of starvation,
for the eruption. By contrast the 1983–86 eruption disease and severe cold. When the small scale of this
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at Kilauea produced ∼0.5 km of lava at eruption rates eruption is considered relative to the sizes of flood
3 −1
ranging from less than 20 to more than 350 m s . basalt eruptions, it is clear that the environmental
The Laki eruption is of special interest because of consequences of a flood basalt eruption are likely to
its effect on climate. The winter of 1783–84 was a be profound (see Chapter 12).
particularly severe one in Europe and was asso-
ciated with a “dry fog” which spread out across
1.2.4 Plinian eruptions
several countries reducing the amount of sunlight
reaching the surface. The most plausible explana- Events such as the May 18, 1980 eruption of Mount
tion for this fog is that it was caused by the release St Helens in Washington State, USA (Fig. 1.2) are
of mainly sulphurous gases during the Laki erup- typical of Plinian eruptions. These eruptions were
tion. The effect of the fog or “haze” in Iceland itself named after Pliny the Younger who wrote an
was extremely severe: it stunted the growth of grass, account of the AD 79 eruption of Vesuvius which
and small amounts of fluorine released from the destroyed the cities of Pompeii and Herculaneum.
lava were taken up by grass and poisoned the ani- In eruptions of this kind a jet of gas and magma