Issue
Europhys. Lett.
Volume 69, Number 5, March 2005
Page(s) 739 - 745
Section Electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics
DOI http://dx.doi.org/10.1209/epl/i2004-10408-x
Published online 02 February 2005
Europhys. Lett., 69 (5), pp. 739-745 (2005)
DOI: 10.1209/epl/i2004-10408-x

Order and disorder in columnar joints

L. Goehring and S. W. Morris

Department of Physics, University of Toronto - 60 St. George Street Toronto, Ontario, M5S 1A7, Canada


received 23 June 2004; accepted in final form 23 December 2004
published online 2 February 2005

Abstract
Columnar joints are three-dimensional fracture networks that form in cooling basalt and several other media. The network organizes itself into ordered, mostly hexagonal columns. The same pattern can be observed on a smaller scale in desiccating starch. We show how surface boundary conditions in the desiccation of starch affect the formation of columnar joints. Under constant drying power conditions, we find a power law dependence of columnar cross-sectional area with depth, while under constant drying rate conditions this coarsening is eventually halted. Discontinuous transitions in pattern scale can be observed under constant external conditions, which may prompt a reinterpretation of similar transitions found in basalt. Starch patterns are statistically similar to those found in basalt, suggesting that mature columnar jointing patterns contain inherent residual disorder, but are statistically scale invariant.

PACS
45.70.Qj - Pattern formation.
62.20.Mk - Fatigue, brittleness, fracture, and cracks.

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