0022-3530/91 $3.00 Comments on 'On Convective Style and Vigor in

In a recent paper in this Journal, Marsh (1989b) put forward a series of incorrect statements about the fluid mechanics of crystallizing convective systems and arrived at conclusions which claim to change the way in which one should describe convection in magma chambers. The theoretical ideas used to support these conclusions are inconsistent with well-established and tested fluid dynamical principles. Along with many of our fluid dynamical colleagues we are concerned about the influence that such inappropriate theory by a well-known geologist will have. We have previously set out our point of view in a series of publications, some of which will be referred to below, but we are constantly approached by geologists to explain our explicit objections to Marsh's published statements in a way that all can read and consider for themselves. We do so briefly here, confining ourselves entirely to questions of fundamental fluid mechanical principles. Geological observations or their interpretation are irrelevant in the discussion of these points as no explanation of a geological feature based on incorrect physical arguments can be of any value. Marsh's thesis, put forward in three separate publications (Marsh, 1988, 1989a, 1989b), is that the convective motion in almost all naturally occurring magma chambers is weak o