Glencoe caldera volcano, Scotland. Classical areas of British geology

By B P Kokelaar I D Moore Contributors: T Bradwell, D Stephenson

Bibliographical reference: Kokelaar, B P, And Moore, I D. 2006. Classical areas of British geology: Glencoe caldera volcano, Scotland. (Keyworth, Nottingham: British Geological Survey.)

(Front cover) Glen Coe viewed towards the south-west from The Study (Photographer: B P Kokelaar) (P611763).

(Rear cover)

(Frontispiece)Viewed due east from the summit of Bidean nam Bian (1150 m), the successive ridges of Beinn Fhada, Buachaille Etive Beag and Buachaille Etive Mòr provide serial sections through the volcanic succession of the Glencoe caldera volcano. The prominent summit in the distance (middle) is of Stob Dearg (1022 m), which presents remarkable exposures of three successive volcanic cones formed during powerful explosive interactions of magma with water. Beyond Stob Dearg lies the desolate Rannoch Moor, mostly underlain by a granitic pluton that was unroofed just before the volcanism at Glen Coe (Photographer: B P Kokelaar) (P611764).

British Geological Survey

Glencoe caldera volcano, Scotland. Classical areas of British geology

Authors B P Kokelaar Department of Earth and Ocean Sciences, University of Liverpool, Liverpool L69 3BX, UK

I D Moore Formerly University of Liverpool; present address Chevron-Texaco, Seafield House, Hill of Rubislaw, Aberdeen AB15 6XL, UK

Contributors T Bradwell D Stephenson British Geological Survey, Murchison House, Edinburgh

British Geological Survey, Nottingham 2006. First published 2006. NERC copyright 2006. ISBN 0 85272 525 6. Printed in the UK

The grid, where it is used on the figures, is the National Grid taken from Ordnance Survey mapping. Maps and diagrams in this book use topography based on Ordnance Survey maps. © Crown Copyright reserved Ordnance Survey licence number 100017897/2006.

(Front cover) Glen Coe viewed towards the south-west from The Study (Photographer: B P Kokelaar) (P611763).

(Rear cover)

Acknowledgements

The geological reappraisal of Glencoe volcano was substantially funded by an Isle of Man Department of Education Postgraduate Studentship (awarded to I D M) and a NERC/BGS contract (GA/96E/13), both held at the Earth Sciences Department of the University of Liverpool. D Stephenson (BGS) wrote the section on the Dalradian metamorphic ‘basement’, and T Bradwell (BGS) Chapter nine — Shaping the landscape. M F Howells and S C Loughlin provided helpful reviews.

Scientific editing on behalf of BGS was by D Stephenson, with review and compilation by E A Pickett; the series editor is A A Jackson. Final versions of figures were produced by BGS Cartography, Edinburgh; pagesetting by A Hill, BGS Keyworth.

Photographs, with the exception of (Plate 1) and (Plate 27), were taken by the authors, and have been deposited for reference in the BGS National Archive of Geological Photographs.

The 3D image used in (Figure 4)a was generated by Harlan P Foote, Image Processing and Analysis Group, Battelle-Pacific Northwest Laboratories, Richland, Washington (state); the geological overprint is from USGS Map I-571, 1970.

(Frontispiece) Viewed due east from the summit of Bidean nam Bian (1150 m), the successive ridges of Beinn Fhada, Buachaille Etive Beag and Buachaille Etive Mòr provide serial sections through the volcanic succession of the Glencoe caldera volcano. The prominent summit in the distance (middle) is of Stob Dearg (1022 m), which presents remarkable exposures of three successive volcanic cones formed during powerful explosive interactions of magma with water. Beyond Stob Dearg lies the desolate Rannoch Moor, mostly underlain by a granitic pluton that was unroofed just before the volcanism at Glen Coe (Photographer: B P Kokelaar) (P611764).

Foreword

The inspiring mountain scenery of Glen Coe, with its famous history of clan rivalry and murder, creates an almost palpable atmosphere of roughness tinged with romance. For many scientists, the awe is enhanced by the importance of the place in the history of geology and, specifically, of volcanology. It was here, close to 100 years ago, that Geological Survey geologists E B Bailey, C T Clough, G W Grabham, H Kynaston and H B Maufe exploited the superb three-dimensional exposure in the rugged terrain to produce the first detailed analysis of how a large, long-lived volcano is successively plumbed by magma. Their interpretation, of ‘cauldron subsidence’, still influences volcanologists who have to infer what they cannot see beneath the surface at modern volcanoes.

In the 1950s and 60s, the recognition of ignimbrites (ash-flow tuffs) and their association with caldera-forming eruptions caused a renewal of interest in the Siluro-Devonian, Glencoe volcano. However, no refinement of existing maps was accomplished, possibly because the prospect of the steep mountain ridges and the midge-infested hollows proved too daunting. By the 1980s and early 90s, when it was clear that understanding of the behaviour of modern, commonly hazardous, caldera volcanoes was hindered by uncertainties at depth, reappraisal of the outstanding natural volcano laboratory at Glen Coe was long overdue.

This book is the result of a complete resurvey of the volcanic rocks and their relationships by Dr Ian Moore, as a PhD student, and Dr Peter Kokelaar, at the University of Liverpool. It is accompanied by a map, at 1:25 000 scale, with several cross sections and a new refined stratigraphy. The early ideas have been modified substantially and the volcano now perhaps constitutes a new archetype, as ‘the world’s best exposed, tectonically controlled, multi-subsidence, piecemeal caldera volcano’! Parts of this complicated interpretation have been published in the relevant journals, but this book presents the complete reappraisal. It has been written with an emphasis on volcanic processes and environments, and on the regional significance of this ancient volcano, to be of interest not only to volcano aficionados but also to the keen amateur and student.

The book and map represent the first major revision of this classical geology since the early pioneering work of those Survey geologists. It is a testament to the techniques of field-based geology, although, inevitably on such a dramatic stage, involving a significant element of mountain guile.

David Falvey, PhD. Director. British Geological Survey. Kingsley Dunham Centre, Keyworth, Nottingham

References