Agassiz's Rock & Blackford QuarryAgassiz's Rock is at the south east end of Blackford Quarry, and is a site of historic and international importance. In 1840 the Swiss geologist Louis Agassiz recognised that the polished and striated undercut base of the cliff was the result of the action of an ice sheet. He visited the site on 27th October 1840 with Charles MacLaren, then editor of the Scostman. In 1838 William Buckland (then professor of geology at Oxford University) and Agassiz studied Alpine glaciers and realised that there were many ice-free areas which showed evidence of former ice. Agassiz then made an intellectual leap from valley glaciers to countrywide ice sheets, and his visit to Scotland in 1840 confirmed his ideas. Most of the evidence Agassiz found has now disappeared as pieces of rock have been eroded or fallen away, but the location marks the first recognition in the world of the reality of former ice sheets. Blackford QuarryBlackford Quarry was used to provide road metal between 1826 and 1953. The open quarry you can see was abandoned in 1875. It was part of more extensive workings to the east which have been filled in. The rock is andesite lava (the name comes from the South American Andes where this kind of volcanic rock is common). Andesite is a dark purplish-grey colour, with a fine grain and many closely spaced cracks which break the rock into smooth-faced blocks. The rock was used for road metal and rough walling rather than building stone because the rock was not suitable for dressing to shape, due to the many cracks running in several directions. |
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