Scaling of columnar joints in basalt

Goehring, L ORCID: https://orcid.org/0000-0002-3858-7295 and Morris, SW, 2008. Scaling of columnar joints in basalt. Journal of Geophysical Research: Space Physics, 113 (B10). ISSN 0148-0227

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Abstract

We describe field work, analysis, and modeling of columnar joints from the Columbia River Basalt Group. This work is focused on the regions around the Grand Coulee, Snake River, and Columbia Gorge, which form parts of this unusually homogeneous and very large sample of columnar basalt. We examine in detail the scaling relationship between the column width and the size of the striae and relate these quantitatively to thermal and fracture models. We found that the column radius and stria size are proportional to each other and inversely proportional to the cooling rate of the lava. Near a flow margin, our results put observational constraints on diffusive thermal models of joint formation. Deeper than a few meters into a colonnade, our measurements are consistent with a simple advection-diffusion model of two-phase convective cooling within the joints, regardless of the direction of cooling. This model allows an accurate comparison of igneous columnar jointing and joints due to desiccation in laboratory analog systems. We also identify a new length scale in which wavy columns can appear in some colonnades. The mechanisms leading to the wavy columns are likely related to those underlying similar wavy cracks in 2-D analog systems.

Item Type:	Journal article
Publication Title:	Journal of Geophysical Research: Space Physics
Creators:	Goehring, L. and Morris, S.W.
Publisher:	Wiley-Blackwell
Date:	October 2008
Volume:	113
Number:	B10
ISSN:	0148-0227
Identifiers:	Number Type 10.1029/2007JB005018 DOI
Divisions:	Schools > School of Science and Technology
Record created by:	Linda Sullivan
Date Added:	06 Sep 2016 10:48
Last Modified:	09 Jun 2017 14:05
URI:	https://irep.ntu.ac.uk/id/eprint/28392

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