Page 38 - Fundamentals of Physical Volcanology

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VOLCANIC SYSTEMS 15

deep within the Earth in the zone in which the the nature of volcanic activity (Stage 4), and to
magma initially formed. To fully understand the vol- show the importance of increasing our know-
canic eruption itself, then, we need to understand ledge of these processes in order to improve our
the subsurface processes which led up to it, as well understanding of the eruptions themselves and
as the processes involved in the eruption itself. the effects that they can have on our lives.
In this book we consider the sequence of phys-
ical processes which lead up to and take place
during a volcanic eruption as occurring within an 1.5 Further reading
overall volcanic system (Fig. 1.21). The physical
processes operating within the system can be
divided into four stages: Stage 1 is the formation of GENERAL
magma; Stage 2 involves the movement of magma
Dobran, F. (2001) Volcanic Processes: Mechanisms
away from the source zone; Stage 3 involves storage
in Material Transport. Plenum, 590 pp. ISBN:
of magma at depth; and Stage 4 involves the move-
9780306466250.
ment of magma to the surface and the eruption
Schmincke, H.-U. (2004) Volcanism. Springer-Verlag,
process itself. The path taken by magma through
324 pp. ISBN: 9783540436508.
any specific volcanic system is not always the same.
For instance, in some cases magma may be formed
(Stage 1) and be transported directly to the surface HAWAIIAN ERUPTIONS
to be erupted (Stages 2 and 4) thus bypassing stor-
Head, J.W. & Wilson, L. (1989) Basaltic pyroclastic
age at depth (Stage 3). In other cases magma may
eruptions: influence of gas-release patterns and vol-
form and move to a zone of storage (Stages 1–3) but
ume fluxes on fountain structure, and the formation
never be erupted. This division of a volcanic system
of cinder cones, spatter cones, rootless flows, lava
into just four stages is something of an oversim-
ponds and lava flows. J. Volcanol. Geotherm. Res.
plification of what can happen, but it is very useful
37, 261–71.
as a way of denoting the key processes that magma
Wolfe, E.W., Neal, C.A., Banks, N.G. & Duggan,
must go through in order to be erupted, and forms a
T.J. (1988) Geological observations and chronology
basis for examining the successive physical processes
of eruptive events. In The Puu Oo Eruption of
experienced by magma as it travels to the surface.
Kilauea Volcano, Hawaii: Episodes 1 through
20, January 3, 1983, through June 8, 1984. U.S.
Geol. Soc. Prof. Pap. 1463, 1–97.
1.4 The structure and aims of this book
In line with the stages shown in Fig. 1.21, we start FLOOD BASALT ERUPTIONS
in Chapter 2 by looking at Stage 1 processes: the
Self, S., Thordarson, T. & Keszthelyi, L. (1997)
generation of magma. In Chapter 3 we look at the
Emplacement of continental flood basalt lava
ways in which magma moves within the mantle and
flows. In Large Igneous Provinces: Continental,
crust (Stage 2). In Chapter 4 we look at magma
Oceanic, and Planetary Flood Volcanism (Eds J.J.
storage (Stage 3). Successive chapters are then
Mahoney & M.F. Coffin), pp. 381–410. Geophysical
concerned with aspects of Stage 4 – the movement
Monograph 100, American Geophysical Union,
of magma at shallow levels within the crust and
Washington, DC.
with the processes and consequences of eruptions.
Swanson, D.A., Wright, T.L. & Helz, R.T. (1975) Linear
The bulk of the book is concerned with Stage 4 vent systems and estimated rates of magma pro-
processes because these are the events that volca- duction and eruption for the Yakima basalt on the
nologists know most about, and because eruption Columbia Plateau. Am. J. Sci. 275, 877–905.
processes have the most direct impact on humans. Thordarson, T. & Self, S. (1993) The Laki (Skafta
Our intention throughout, however, is to empha- Fires) and Grimsvotn eruptions of 1783–1785.
size how subsurface processes (Stages 1–3) affect Bull. Volcanol. 55, 223–63.