Mull – MacCulloch’s tree

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In 1811, John MacCulloch (1773 – 1835) began a tour of Scotland to investigate its geological history, a tour which culminated in his book ‘A Description of the Western Isles of Scotland’, published in 1819. As part of this tour he visited the Isle of Mull where he identified the coniferous tree, now known as MacCulloch’s Tree. This fossilised tree stands within columnar basalt and is the largest and most famous of several trees to be found in the area of Ardmeanach.

The tree exists as a pipe-like cast (1m x 12m), surrounded by columnar basalt of the Staffa Magma Type lavas. The cast contains some carbonised woody remains and volcanic debris, and at the base of the lava pile there is a layer of mud, coal and volcanic ash. Unfortunately, collectors have stripped most of the black woody remains since the tree’s discovery.

MacCulloch's Tree - a pipe-like cast (1m x 12m) of a tree, surrounded by columnar basalt. © Angus Miller.

MacCulloch’s Tree – a pipe-like cast (1m x 12m) of a tree, surrounded by columnar basalt. © Angus Miller.

The tree has been assigned to the genus Cupressinoxylon. It and the others in the area probably represent the last remains of a forest that was covered by a lava flow approximately 60 million years ago, during eruptions from the Palaeogene Mull volcanic centre.

Note: The Mull volcanic centre forms part of the North Atlantic Palaeogene Igneous Province, along with the other centres of Skye, Arran, Ardnamurchan, Rum and St. Kilda.

Further reading:

Bailey, E.B. & Anderson, E.M. 1925. The Geology of Staffa, Iona & Western Mull (Memoirs of the Geological Survey, Scotland). His Majesty’s Stationery Office, Edinburgh.

Emeleus, C.H. & Gyopari, M.C. 1992. British Tertiary Volcanic Province, Geological Conservation Review, Series No. 4. Joint Nature Conservation Committee, Peterborough, 259 pp.

Emeleus, C.H & Bell, B.R. 2005. British regional geology: the Palaeogene volcanic districts of Scotland (Fourth edition). (British Geological Survey, Nottingham.

Stephenson, D. 2005. Mull and Iona – A Landscape Fashioned by Geology. Produced by: Scottish Natural Heritage & British Geological Survey.