Page 145 - Fundamentals of Physical Volcanology

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122 CHAPTER 8

(a)

pyroclastic density current
aggrading ignimbrite

flow boundary zone
shown in B and C

(b)
concentration
profile
velocity
h profile

basal part
of current
FLOW BOUNDARY
(sharp rheological interface,
sharp high shear)
upper part rheological
of deposit boundary

C, u

(c)
concentration
profile velocity
profile
h

basal part
of current
FLOW BOUNDARY
(no sharp rheological interface,
low shear)
compacting &
degassing
deposit

C, u
Fig. 8.12 Possible vertical variations in particle concentration, C, and horizontal velocity, u, in pyroclastic density currents.
(Taken from fig.1.2 in Branney, M.J. and Kokelaar, P. (2002) Pyroclastic Density Currents and the Sedimentation of
Ignimbrites. Geol. Soc. Memoir No. 27, Geol. Soc. Lond.)