Physicists crack riddle of hexagonal columns

December 27th, 2008 - 3:45 pm ICT by IANS  

Washington, Dec 27 (IANS) Physicists have cracked the riddle of the uncannily well-ordered hexagonal columns at popular tourist spots like Giant’s Causeway in Northern Ireland and California’s Devil’s Postpile, using water, corn starch, and a heat lamp.”The size of the columns, which varies from site to site between a few inches and a few yards, is primarily determined by the speed at which lava from a volcanic eruption cools,” said University of Toronoto (U-T) physics professor Stephen Morris, who supervised the thesis project of PhD student Lucas Goehring.

Cooling lava sometimes forms strange column-shaped formations with a remarkable degree of order. The most famous of these hexagonal columns are found at the Giant’s Causeway in Northern Ireland, where they are said to be the work of Finn MacCool, an Irish giant.

Using a combination of field observation, experiments and mathematical theory, the researchers have solved the problem of what decides the size of the columns.

The key to understanding the size of the columns was to reproduce the phenomenon in the lab.

Using a mixture of water and corn starch - which cracks as it dries out and forms very similar columns - they carefully controlled the drying process, and established a relationship between the size of the columns and speed with which the drying front moved.

Goehring also visited several sites around the world and measured certain markings on the sides of lava columns, which were used to deduce the speed with which they formed as the lava cooled, said an U-T release.

“Putting all of these pieces together showed that the columns are formed by the same process in starch as in lava,” said Morris. “We identified the special ratio of speed, column size and diffusion rate that is the same for all cases, finding that the slower the cooling process, the larger the resulting columns would be.”

The findings appeared in the December online issue of the Proceedings of the National Academy of Sciences.

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