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STEADY EXPLOSIVE ERUPTIONS 93

properties. Geophys. J. Roy. Astron. Soc., 89, Volcanic Plumes (Chapter 6). Wiley, Chichester,
657–79. 574 pp.
Wilson, L., Sparks, R.S.J., Huang, T.C. & Watkins, N.D.
(1978) The control of volcanic column heights
by eruption energetics and dynamics. J. Geophys. 6.10 Questions to think about
Res. 83, 1829–36.
1 What two aspects of the expansion of gas bub-
bles in magmas rising toward the surface cause
OBSERVATIONS OF ERUPTION PLUMES
an increase in the magma rise speed?
Sparks, R.S.J. & Wilson, L. (1982) Explosive volca- 2 Why does magma fragmentation make a big con-
nic eruptions V: observations of plume dynamics tribution to increasing the rise speed of magma
during the 1979 Soufriere eruption, St. Vincent. in a dike?
Geophys. J. Roy. Astron. Soc. 69, 551–70.
3 In what three ways does a large volatile content
Sparks, R.S.J., Bursik, M.I., Carey, S.N., Gilbert, J.S.,
in a magma contribute to a high eruption speed?
Glaze, L.S., Sigurdsson, H. & Woods, A.W. (1997)
4 Why do some magmas reach the surface at pres-
Volcanic Plumes (Chapter 5). Wiley, Chichester,
sures greater than atmospheric pressure?
574 pp.
5 Why does the material in an eruption cloud slow
Wilson, L. & Self, S. (1980) Volcanic eruption plumes:
down at first after leaving the vent but then
density, temperature and particle content estimates
increase its speed for a while before eventually
from plume motion. J. Geophys. Res. 85, 2567–72.
slowing down again?
6 What controls the maximum height to which an
PLUME INSTABILITY eruption cloud can rise in the atmosphere?
7 Why are large pyroclasts always found close to
Sparks, R.S.J. & Wilson, L. (1976) A model of the
the vent in air fall eruption deposits whereas
formation of ignimbrite by gravitational column
collapse. J. Geol. Soc. London 132, 441–51. small clasts are found at all distances from the
Sparks, R.S.J., Wilson, L. & Hulme, G. (1978) vent?
Theoretical modelling of the generation, move- 8 Why is it likely that an eruption may evolve from
ment, and emplacement of pyroclastic flows by being Plinian to being ignimbrite-forming in
column collapse. J. Geophys. Res. 83, 1727–39. nature but is much less likely to evolve in the
Sparks, R.S.J., Bursik, M.I., Carey, S.N., Gilbert, J.S., other direction?

Glaze, L.S., Sigurdsson, H. & Woods, A.W. (1997)