Irelands huge hexagonal columns are a natural consequence of lava cooling.
The Giants Causeway.
© Allan Davies / LGPL
The Giants Causeway is not the work of men or monsters, but a natural consequence of how lava cools and solidifies, new computer simulations suggest.
The causeway is a field of roughly hexagonal basalt columns up to 40 feet high on the shores of County Antrim in Northern Ireland. It arose when a flow of volcanic rock split into hexagonal columns to relieve stress, according to Eduardo Jagla of the Centro Atómico Bariloche in Argentina and Alberto Rojo of the University of Michigan in Ann Arbor1.
They might be giants
When the Giants Causeway was first reported to the Royal Society in London in 1693, some wondered whether men had created the step-like stone columns with picks and chisels. Local legend attributes them to the Irish giant Finn McCool, said to have wanted to walk to Scotland without wetting his feet. The more prosaic lava-flow explanation was put forward in 1771.
The columns form a natural stairway from a cliff into the sea. All have between four and eight sides, but most are roughly hexagonal. This geometric regularity has perplexed scientists for centuries.
Jagla and Rojo support their idea with computer simulations of fracture patterns in a layer of particles joined by springs, which mimic the mutually attractive atoms in the rock. The researchers simulate shrinking and cracking in a series of particle layers, using the final cracking pattern in one layer as the starting point for the cracking of the layer below.
They find that the pattern evolves from one that has many randomly distributed cracks to one in which the fractures define large polygons, most of which are six-sided.
Whats more, the model correctly predicts the proportions of columns with different numbers of sides and the average cross-sectional areas of these columns.
PHILIP BALL | © Nature News Service
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