Scotland's Mountain Landscapes

Colin K. Ballantyne

Description

The diversity of Scotlands mountains is remarkable, encompassing the isolated summits of the far northwest, the serrated ridges of Skye, the tor-studded high plateau of the Cairngorms and the rolling hills of the Southern Uplands. Born on ancient continents and uplifted by tectonic forces, the mountains of Scotland have been sculpted by successive ice sheets, landslides, frost, wind and running water. This book explains the geological evolution of Scotlands mountains, and how this has produced an unparalleled variety of mountain forms. It outlines the effects of successive ice sheets on mountain scenery, and explains the dramatic changes in climate that terminated the Ice Age only 11,500 years ago. In non-technical terms it explains the effects of frost action in forming the rubble that mantles many mountain summits, and how such debris has slowly migrated downslope by freezing and thawing of the ground. The dramatic effects of deglaciation and earthquakes in triggering catastrophic landslides and downslope displacement of entire mountainsides are described, along with accounts of more recent events involving the rapid downslope flow of saturated debris. The book also outlines how Scottish mountains experience frequent gale-force winds, and their impact of wind in scouring plateaus and depositing expanses of windblown sand on lee slopes. The role of floods in eroding upland terrain and depositing floodplains, terraces and fans of sediment is described in the context of possible human influence on river regime through forest clearance.Written in clear, non-technical language and abundantly illustrated, this book is designed to provide an essential guide to landforms for all those who walk, climb, live and work in the mountains of Scotland.

Sujets

• Sciences et techniques
• Earth science

Informations

• Publié par: Dunedin Academic Press
• Date de parution: 01 décembre 2019
• Nombre de lectures: 0
• EAN13: 9781780466101
• Langue: English
• Poids de l'ouvrage: 5 Mo

Extrait

Scotland’s Mountain Landscapes
A GEOMORPHOLOGICAL PERSPECTIVE
Colin K. Ballantyne
For Rebecca, Hamish and Kate
Contents
Acknowledgements
1 Introduction
The land of the mountain and the flood
Geology and geomorphology
Weathering, erosion and deposition
Dating the past: the geological timescale
Dating the Quaternary
About this book
2 The geological evolution of Scotland
Introduction
Rocks
Plate tectonics
Geological evolution: the making of Scotland
Conclusion
3 Rocks, relief and the preglacial landscape
Introduction
Structural grain: the ripples of orogeny
Rocks and relief
Cenozoic landscape evolution
Synthesis
Before the ice: the preglacial landscape of Scotland
4 The Ice Age in Scotland
Ice ages: an introduction
Glacial and interglacial stages
Glaciers and glaciation
The last Scottish Ice Sheet
The last mountain glaciers: the Loch Lomond Stade
The Holocene
Synthesis
5 Glacial landforms
Introduction
Landforms of glacial erosion
Landforms of glacial deposition
Glacifluvial landforms and deposits
Ice-dammed lakes
Synthesis: glacial landscapes of Scotland
6 Periglacial landforms
Introduction
Ancient periglacial landforms: blockfields and tors
Lateglacial periglacial landforms
Active periglacial landforms
Synthesis
7 Landslides and related features
Introduction
Rock-slope failures
Rockfall, talus and snow avalanche landforms
Slope failures in soil and peat
Debris flows
Conclusion
8 Aeolian landforms
Introduction
Aeolian processes
Landforms produced by wind erosion
Aeolian deposits
Conclusion
9 Fluvial landforms
Introduction
Mountain rivers
River terraces
Alluvial fans
Conclusion
Postscript: into the Anthropocene
10 Key sites
Introduction
An Teallach, Wester Ross
Torridon, Wester Ross
The Trotternish escarpment, Isle of Skye
The Cuillin Hills, Isle of Skye
Glen Roy, Lochaber
Glen Coe, Western Grampians
The Cairngorms
Drumochter Pass, Central Grampians
Tinto Hill, Southern Uplands
Further reading
Index of locations in Scotland
Index of Scottish mountains and hills
General Index
Acknowledgements
In preparing this book for submission I owe a huge debt of gratitude to Professor John Gordon. John has an unrivalled knowledge and understanding of the geomorphology of Scotland, and his insightful and incisive comments greatly improved the text. The book has also greatly benefited from the contribution of my longstanding friend and colleague Graeme Sandeman, cartographer at the University of St Andrews, who produced all the final maps and figures. Graeme has been transforming my inept scribbles into crisp cartography for nearly four decades, and the figures contained herein are (yet again) testimony to his skill and forbearance. I am also indebted to Professor Doug Benn and Dr Adrian Hall for reading over particular chapters and preventing a few embarrassing blunders. John Gordon, Charles Warren, David Evans and Martin Kirkbride all helped by contributing photographs.
The impetus for writing this book came from friends who have for many years had to suffer my enthusiasm for explaining the origin of ploughing boulders, tors, rock-slope deformations and a multitude of other landforms as we tramped over Scottish mountains. I thank in particular Peter Robinson for being a patient listener for over 40 years, and Cairns Dickson, who egged me on to put it all in print, and who gamely read through and commented on the draft manuscript. I owe an enormous debt to my co-researchers on aspects of Scotland’s geomorphology, notably Professors Doug Benn, Svein Olaf Dahl, Atle Nesje, Danny McCarroll and John Stone, my former PhD students, and especially the legions of enthusiastic students at St Andrews University who have clambered up Scottish mountains in all weathers to assist in fieldwork.
I owe particular thanks to Anthony Kinahan of Dunedin Academic Press for providing encouragement and advice throughout the writing and production stages, David McLeod for design and compilation of the book, and Anne Morton for eagle-eyed copy-editing.
This book owes much to my mentor and friend, Dr Brian Sissons (1926–2018). Brian made an unparalleled contribution to our understanding of the geomorphology of Scotland, some of which is reflected here. His seminal book The Evolution of Scotland’s Scenery (1967) influenced my decision to pursue a career as a geomorphologist, a choice that has allowed me to combine research with my love of mountains, the Arctic and above all the Scottish landscape.
My children, Hamish and Kate, have tolerated numerous ‘holidays’ that involved them being cajoled up rainswept mountains with promises of ice cream. My wife Rebecca has been my constant companion on the hills in weather fair and foul, and tolerated my long absences spent working in a hut at the bottom of the garden. Together we treasure wonderful memories of summits across the globe from Kilimanjaro to Kosciuzsco, but the best of these have been in Scotland.
Colin Ballantyne Blebo Craigs Scotland
Chapter 1
Introduction
The lowly offices of wind and rain, springs and frost, snow and ice, trifling as they may appear, have nevertheless been chosen as instruments to carve the giant frame-work of the mountains.
Archibald Geikie: The Scenery of Scotland (1865)
The land of the mountain and the flood
Mountains represent the essence of Scotland’s scenery. Postcards, calendars, shortbread tins and dishtowels seeking to capture ‘Scotland’ in a single image almost invariably depict a mountainous Highland landscape, sometimes with a loch or castle in the middle distance and a kilted bagpiper artfully (and sometimes digitally) inserted in the foreground. They are a fundamental part of Scottish identity, for though most Scots live in the towns and cities of the lowlands, the mountains are close by on the horizon, a line of purple or snow-covered peaks that reminds us of another Scotland where the interplay of sunshine and cloud over rocky crags, deep lochs, windswept plateaux and lonely moorlands creates a sense of wilderness and an opportunity to escape from our urban hinterland.
And escape we do. When the weather is favourable, thousands of hillwalkers visit the summits of Scotland’s mountains every week, many with the aim of completing the ascent of the 282 Munros (summits over 3000 feet or 914 m). Rock climbers are drawn to the crags and corries of Skye and Glen Coe, skiers to the snowy slopes of Glen Shee and the Cairngorms, and others come to the mountains for fell running, mountain biking and even hang gliding. Outnumbering all of these, however, are the visitors who come simply to marvel at the most wonderful scenery in the British Isles.
Nobody who has explored the mountains of Scotland can fail to have been impressed by their sheer diversity. The isolated sandstone peaks of the far northwest, the serrated gabbro ridges of Skye, the granite high plateaux of the Cairngorms, and the rolling uplands of southern Scotland ( Fig. 1.1 ) represent a variety of mountain landscapes that rivals any on Earth. Such diversity reflects not only Scotland’s tumultuous geological evolution, which has created a mosaic of contrasting rock types, but also the operation of a wide range of erosional processes that have sculpted the underlying rocks into the wonderful topographic variety of Scotland’s mountain landscapes. Some of these processes operated in deep time, many millions of years ago, others throughout the Ice Age, and many, such as frost action, rockfall and river erosion, have continued to modify mountain landscapes since the disappearance of the last glaciers.
In this book we shall take a journey through time, beginning with the formation of the oldest rocks and ending with the manifold processes that are still operating on high ground. We shall visit past eras when Scotland lay near the Equator, when alpine-scale mountains towered over the landscape, when volcanoes spewed out copious lava flows, when ice covered the land, and when earthquakes triggered major landslides. Mountain scenery is always inspirational; but understanding how mountain landscapes have evolved deepens our perspectives of time and space, and the transience of human existence. Just 12,500 years ago, for example, Scotland looked like high-arctic Svalbard today: a great icefield occupied the western Highlands, a valley glacier was advancing to the southern end of Loch Lomond, permafrost underlay the ground beyond the glaciers and mean July temperatures were no higher than those in November at present. Understanding such events and their effects on the landscape can make a day in the Scottish mountains a thrilling excursion that spans millions of years.
This chapter provides some basic concepts and terminology for readers with limited prior knowledge of geology and geomorphology. It introduces the concept of recycling of rock materials, focusing on the ways in which rocks are broken down and eroded, and how rock material (sediment) is transported by various agencies and deposited. It also outlines the geological timescale and describes how rocks, landforms and sediments can be dated and interrogated to reconstruct histories of past events.

Figure 1.1 Examples of the diversity of Scotland’s mountain landscapes. ( a ) Suilven (731 m) in NW Scotland, a sandstone mountain rising above glacially scoured gneiss (photograph by John Gordon). ( b ) Sgùrr Dubh Mór (944 m) and Sgùrr Dubh an Da Bheinn (938 m), Cuillin Hills, Skye. ( c ) The eastern Grampians, with the Cairngorms on the skyline. ( d ) The Southern Uplands: White Coomb (821 m) from Hart Fell.
Geology and geomorphology
Geology is the science of the Earth and its history, reconstructed from the record of rocks: their types, structures, ages and origins. For over two centuries, geologists have studied the characteristics and distributions of rocks to piece together a coherent inter