Clochodrick Stone

J.E. Gordon

Highlights

Clochodrick Stone is a notable example of a glacial erratic boulder. Historically, such features were among the first considered to require systematic documentation and conservation.

Introduction

The Clochodrick Stone [NS 374 613] is a particularly good example of a lowland glacial erratic boulder. It is located 3 km north-east of Lochwinnoch and has been described by Milne Home (1872b).

Description

The large glacial erratic known as the Clochodrick Stone (Clach a'Druidh) (Figure 16.5) is located at an altitude of about 100 m above sea level. It measures 6.7 m in length, 6.1 m in width, 20.6 m in circumference and stands up to 4.0 m above ground level. The rock of which it is composed is a trachytic porphyritic olivine basalt and it is crossed by a series of hematite veins. The boulder rests on lavas of slightly different composition, and it was recorded in the First Report of the Boulder Committee (Milne Home, 1872b) that bedrock of the same type as the boulder occurs in the hills two or three miles to the west and north.

Interpretation

The Clochodrick Stone is a particularly good example of a large erratic boulder. Although erratics and erratic trains are relatively widespread in Scotland (see for example, Bell, 1874; Milne Home, 1884; Cumming and Bate, 1933; Sissons, 1967a; Shakesby, 1978; Sutherland, 1984a), the Clochodrick Stone is particularly striking in terms of its size and lowland setting. It was probably transported to its present position by ice from the south-west Highlands moving across the Clyde estuary. This ice moved across and around the Renfrewshire hills towards the south-east (Price, 1975; Paterson et al , 1990).

The Clochodrick Stone is also of more general historical interest in the field of earth-science conservation. It is representative of a suite of features that were among the first to be considered worthy of protection. In 1871 the Royal Society of Edinburgh established the Boulder Committee under the direction of D. Milne Home to identify all the glacial erratics in Scotland that appeared remarkable in terms of size and superficial markings and to recommend measures for their conservation (Milne Home, 1872a, 1872b). This exercise, to some extent a forerunner of the Geological Conservation Review, represents a far-sighted attempt to recognize geomorphological features under threat and to address the need for site survey, assessment and protection. Unfortunately, and unlike the GCR, there was no contemporary legislative framework to underpin the work of the Committee and positive action was to be confined to persuading landowners not to destroy those boulders that merited preservation for further study (Milne Home, 1872a, 1872b). In all, the Committee produced ten reports, the tenth and final one providing a county by county compendium of the boulders listed in the earlier reports (Milne Home, 1884).

Conclusion

Clochodrick Stone is a representative example of a large ice-transported (erratic) boulder. Such boulders were among the first geological features recognized to require systematic survey for conservation during the 19th century; they provide graphic evidence of former ice-sheet movements, in this case from the north-west.

References