A Volcanic Past at Spier's
16 August
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Basalt with ancient gas bubbles
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Tree roots entwined with basalt bedrock
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Uprooted tree at Spier's
A large fallen tree at Spier's Old School Grounds has its roots embedded in rock which is derived from an old lava flow known as a 'dike,' one of a 'swarm' that exist locally.
The solid geology of the Beith area is dominated by rocks such as limestone, coal, and also whinstone, an igneous basalt. The whinstone is therefore derived from volcanic activity and often shows itself as 'dikes' which are usually linear seams of hardened lava which was originally pushed up through the overlying limestone or coal. Coal miners were greatly incovenienced by these hard dikes.
The basalt at Spier's has many distinctive holes or bubbles, known as vesicles. These formed when gases such as steam and carbon dioxide escaped as the compressive pressure got less in the molten rock as the lava reached the surface. The largest numbers of bubbles occur when the hardened skin of the lava surface prevented the bubbles from rising to the surface and bursting.
Olivine crystal faces are visible, a mineral rich in silica, iron and magnesium. The size of the faces shows that the lava cooled relatively slowly, allowing the crystals time to 'grow'.
Spier's is close to the limestone quarries of Broadstone, Hillhead, Middleton, Dockra and Trearne. Whinstone has been quarried along a dike at Barrmill and is still quarried at Loanhead.
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