>Date: Mon, 02 Apr 2001 11:39:12 -0400
>From: [local anthropologist]
>over the last 20 years i've been getting a version of Dale Cook's "buns"
>about every six months. Soddy Creek has a stretch of them for about 200
>meters. i also have a small example [...], on a rock that someone came
>in with who thought it was an "Indian map." Habte can probably tell you the
>geological name for that formation. it's neither alien nor cultural.
>Date: Mon, 02 Apr 2001 11:28:07 -0700
>From: Dr Annie Holmes [UTC Clinical Assistant Professor of Geology]
>Organization: University of Tennessee at Chattanooga
>from the photos they look like differential weathering of liesegang iron
>deposits that are following fractures (joints). I'm pretty sure it is
>in sandstone, as that is highly porous (e.g., would transmit the water
>bearing the iron very easily). The iron clogs up the pore spaces
>between the sand grains and the water is forced to move out around it,
>forming the circular patterns. The fractures/joints are the parallel
>and perpendicular cracks intersecting one another. If you have a sample
>we can look at it up here in the geo dept.
>Date: Mon, 02 Apr 2001 11:33:10 -0700
>From: Habte Churnet [UC Foundation Professor and Head UTC Department of Physics, Geology, and Astronomy]
>Excellent photographs of weathering of liesegang rings.
>The glossary of geology defines liesegang rings as: a "Secondary, nested
>rings or bands caused by rhythmic precipitaion within fluid saturated
>rock". The liesegangs tend to be red from iron oxide and hydroxides.
>the box-work appearance likely indicates precipitation along joint sets,
>one set likely trending Northeast-southwest and another
>the above is my quick estimation based on the photographs.
>Date: Mon, 2 Apr 2001 21:40:58 -0400
>From: Jonathan Mies [UC Foundation Associate Professor of Geology]
>I know it as "boxwork weathering". It occurs naturally and it's fairly
>common in sandstone, such as the rock on Mowbray Mountain. There are
>various ideas as to how it forms. It begins as a rectangular network of
>vertical, planar cracks; we call them "joints". Iron-rich aqueous solutions
>pass through the cracks and penetrate the adjacent sandstone, usually to
>just a centimeter or two. Some of the iron remains in the rock and serves
>to cement the sand grains more firmly than the rest of the rock. When the
>rock surface is weathered, the iron-cemented rock adjacent to the cracks is
>more resistant and is left standing up in relief. This results in an
>intricate rectangular pattern of ridges.
>Hope this helps.
Pure Appl. Chem., Vol. 71, No. 6, pp. 1007±1017, 1999.
Printed in Great Britain. 1999 IUPAC
*Lecture presented at the 7th International Chemistry Conference in Africa & 34th Convention of the South African Chemical Institute, Durban, South Africa, 6-10 July 1998, pp. 919-1024.
Pattern formation and symmetry-breaking bifurcations fueled by dissipation of chemical energy: a possible model for morphogenesis?
Reuben H. Simoyi
Center for Nonlinear Science and the Chemistry Department, West Virginia University, Morgantown, WV 26506-6045, USA
Abstract: A solution containing a reacting, autocatalytic and bistable chemical system can spontaneously form patterns and structure from erstwhile homogenous aqueous reaction solutions. Among some of the patterns formed are concentric rings and thermal plumes. The exothermic chemical reaction fuels the pattern-formation through a coupling of Marangoni and Rayleigh-Bénard-type thermogravitatioal effects. The thermogravitational effects arise from multicomponent convection which fuels the formation of salt fingers. These fingers later curl upwards to form thermal plumes. The concentric patterns result from the formation of a complete convective torus. The formation a series of stationary convective tori suggest that there is a possibility of other mechanisms in solution which can form Turing-like patterns.
The mechanism for the development of structure and form from erstwhile homogenous media has baffled scientists for years. The age-old problem of geological layering, Liesegang rings, is still searching for a solid explanation . The mathematical description of symmetry-breaking bifurcations using the standard and symmetric hydrodynamics, reaction and diffusion equations requires special preconditions  which may be difficult to replicate in realistic physical systems.