Edinburgh & West Lothian: A landscape fashioned by geology The tranquil appearance of the city of Edinburgh nestling between the surrounding hills and the undulating countryside of West Lothian belies their dramatic volcanic past. The Lothian landscape took over 400 million years to reach its present shape. This book tells the story of its journey from erupting volcanoes, through rivers, seas and ice-caps, to the peaceful parks, restored quarries and level playing fields we see today. West Lothian EDINBURGHA LANDSCAPE FASHIONED & BY GEOLOGY There is probably no place in the world which better exemplifies "A Landscape Fashioned by GEOLOGY Lothian: & West A LANDSCAPEEDINBURGH BY FASHIONED Geology" than the area around Edinburgh. Here you can follow in the footsteps of James Hutton, the Father of Modern Geology, see what he saw, and better understand the processes that formed Edinburgh’s dramatic landscape. This booklet is beautifully accessible, taking you on a journey from today’s familiar hills and valleys to the icy wastes of two million years ago and further back, to the volcanoes and coal swamps of 350 million years ago when Edinburgh lay at the equator. What more exciting story could there be than the story in the rocks and landscapes of Edinburgh. Dr Stuart Monro, Scientific Director, Our Dynamic Earth About the Author David McAdam has spent a lifetime mapping and describing the geology of east central Scotland. He has contributed to three other titles in the `Landscape Fashioned by Geology ' series. Although recently retired, he remains a Visiting Scientist with the British Geological Survey to continue his interest in promoting Scotland's geological heritage. ISBN 1-85397- 327- 0 9 781853 973277 ISBN 1 85397 327 0 Price £4.95 Scottish Natural Heritage British Visit our website on http://www.snh.org.uk Geological Survey NATURAL ENVIRONMENT RESEARCH COUNCIL ©Scottish Natural Heritage 2003 ISBN 1 85397 327 0 A CIP record is held at the British Library HS3K0303 Acknowledgements Author: David McAdam Text on pages 26 and 27: Allison Grant Text on page 30: Alan McKirdy (SNH) Series editor: Alan McKirdy (SNH) Photography T.S. Bain/BGS front cover, back cover, frontspiece, 5 left, 5 right, 6 left, 7 top, 7 bottom, 8, 13 top, 14, 16, 18 left, 18 right, 19 top, 19 bottom, 21, 23, 24, 26, 27, 28, 29, M.A.E. Browne 31 left, L. Gill/SNH 22, F.I. Mactaggart/BGS 10 top, P&A. MacDonald/SNH 11 left, 12, The Trustees of the National Museums of Scotland 30 bottom. Illustrations C. Ellery 2, 3, 6 right, 9, 11 right, 15 bottom, 17, 25 bottom, I. McIntosh contents page, The Natural History Museum, London 4, Royal Society of Edinburgh (Transactions 12, plate 6) 20, Scottish Academic Press plc top 30 top. Further copies of this book and other publications can be obtained from: The Publications Section, Scottish Natural Heritage, Front cover image: Battleby, Redgorton, Perth PH1 3EW Salisbury Crags and Arthur’s Seat Tel 01738 444177 Fax:01738 827411 from Blackford Hill, Edinburgh E-mail: [email protected] Back cover image: Web site: http://www.snh.org.uk Samson’s Ribs, Arthur’s Seat, Edinburgh EDINBURGH & West Lothian A Landscape Fashioned by Geology by David McAdam Edinburgh skyline from Rest-and-be-thankful, Corstorphine Hill Contents 1. Introduction 20. Edinburgh’s Buildings – A Man-made Landscape 2. Edinburgh & West Lothian Through Time 22. Nature Provides a Playground 3. Geological Map of Edinburgh & West Lothian 24. Pentland Hills from Castlelaw Hill 4. Volcanoes Create the Seven Hills 26. The Landscape Today 6. Intrusions - Volcanoes That Did Not Quite Make It 30. Sites of Special Scientific Interest (SSSIs) 8. The Arthur's Seat Volcano Today 31. RIGS – Regionally Important Geological Sites 10. Sedimentary Strata Form the Low Ground 32. Scottish Natural Heritage and the British Geological Survey 12. The Great Ice Age – Glaciation Moulds the Grain 33. Geological Code 14. Lochs, Seas and Rivers – The Great Levellers 34. Also in the Landscape Fashioned by Geology Series 16. Edinburgh Castle and The Royal Mile 35. SNH Publications Order Form 18. Mining & Quarrying – Man Alters Nature's Landscape Edinburgh, called the `Athens of the North' because of its classical architecture, is said like Rome to be built on seven hills - Castle Hill, Calton Hill, Arthur's Seat, Corstorphine Hill, Craiglockhart Hill, Blackford Hill and the Braid Hills. What links all these hills is their igneous or volcanic origin; they are all made of hard durable rock which has resisted subsequent erosion to leave them standing as prominent features of the landscape. But there are also ridges and hollows, gorges and flat plains. Edinburgh's landscape took over 400 million years to reach its present shape. This booklet explains how. 1 Edinburgh & West Lothian Through Time RECENT TIMES Present day. New ‘New Town’ at Edinburgh Park. City By-pass open; coal and oil-shale industries closed. 80 years ago. Midlothian Coalfield and West Lothian oil-shale field at peak, coal and massive red spent shale bings. 220 years ago. Edinburgh New Town round drumlin ridge of George Street; built from sandstone quarried at Craigleith and Hailes and transported by canal from West Lothian; Nor’ Loch drained; limestone quarrying, as at Gilmerton and Cousland. 800 years ago. Edinburgh Old Town developed round Castle Rock and down glacial tail feature of Royal Mile; lowland forests on glaciated landscape cleared and lochs drained for agriculture. Coal mining starts. 1,900 years ago. Glaciated landscape, shallow lochs marshy and silting up; Roman occupation of ports at Cramond and Inveresk. QUATERNARY 5,000 to 4,000 years. Sea at level comparable with present day; Neolithic hunters colonised the area building strongholds THE ‘ICE AGE’ on volcanic hills; away from lowland forests and swamps with their predators. 6,500 years. Sea level at 8m above present day forming an extensive platform with prominent cliff all along the coast. 2.4 million years ago up to and including 9,000 to 8,000 years. Peat accumulates as climate becomes warm and wet. recent times ❄ 11,000 to 10,000 years. Climate cools again to arctic conditions; sea level falls to present-day level or below. ❄ ❄ 13,000 years. Ice had retreated to the Highlands and had vanished from the Southern Uplands; melt water cut new valleys ❄ ❄ and gorges, transported glacial debris and deposited it as sands and gravels, as in the Esk Valley, or as silts and clays in ❄ ❄ ❄ lochs and along sea-shores; sea level is up to 45m higher than present day. 19,000 years. Ice, 5 kilometres thick, extends many miles east of the present coastline. ❄ ❄ 27,000 years. Last advance of the ‘Ice Age’ as ice builds up in the Highlands and Southern Uplands. 2.4 million years. Climate cools and ‘Ice Age’ begins. TERTIARY 62 million years. Weathering and erosion largely fashion present-day river systems; Volcanic activity in west of Scotland; 65 to 2.4 million years ago no record of any geological events in Edinburgh & West Lothian. CRETACEOUS 80 million years. Warm shallow temperate seas fringe the land, with chalk deposited across Scotland, but later removed 135 to 65 million years ago by erosion. JURASSIC Climate on land is warm and humid. 205 to 135 million years ago PERMIAN - TRIASSIC Climate on land is arid; desert conditions widespread. 295 to 205 million years ago CARBONIFEROUS Throughout Carboniferous. Intrusion of dykes and sills as at Salisbury Crags and Corstorphine Hill. 355 to 295 million years 305 million years. Movements within the Earth’s crust, cause folding, faulting, uplift of the crust and subsequent erosion. Scotland sits astride the equator 315 million years. Forests established to give another series of coal seams. 320 million years. Large rivers lay down thick sandstones. 330 million years. Thick forests repeatedly blanket the land, their peaty remains turning to numerous coal seams. 335 million years. Corals flourish in tropical seas and rich marine life in carbonate muds, producing thick beds of limestone full of fossils. 340 million years. Rich algal life flourish in coastal lagoons, producing oil-shales; while river deltas lay down thick sandstones as at Craigleith and Hailes. 345 million years. Small volcanoes begin erupting lavas and ash on land and under the sea, as at Arthur’s Seat, Castle Rock, Craiglockhart Hill. Volcanic activity and earthquakes continue throughout the next 50 million years. 355 million years. Semi-arid coastal plain at times flooded by the sea. Limy beds with shrimps, mussels and other fossils. DEVONIAN 370 million years. Widespread alluvial plain established, inland desert with extensive areas of sand dunes, leaving 410 to 355 million years sandstones along north of the Pentland Hills. 410 million years. Large volcanoes producing lava and debris flows built the Pentland Hills, Braid Hills and Blackford Hill. Semi-arid climate with large river systems depositing thick beds of sand and gravel. Primitive plants and fish fossilised in lake deposits. SILURIAN 420 million years. The earth moves when Scotland collides with England as the Iapetus Ocean in-between closes. 440 to 410 million years Extensive folding, faulting, and uplift of the crust from the Southern Uplands and subsequent erosion ensues. The Southern Upland Fault is created as a boundary between the Southern Uplands and the Midland Valley. ORDOVICIAN Great thickness of muds and sands accumulate in the Iapetus Ocean, which separated Laurentia (including the land now 510 to 440 million years called Scotland) from Avalonia (including the land now called England). No record of any earlier geological events in Edinburgh & West Lothian. 2 Geological Map of Edinburgh & West Lothian BO'NESS INCHKEITH QUEENSFERRY LEITH LINLITHGOW EDINBURGH BROXBURN HILLS BATHGATE LIVINGSTON DALKEITH WHITBURN WEST CALDER PENICUIK PENTLAND HILLS Carboniferous Former loch Intrusive rocks Lower Devonian other sedimentary rocks volcanic rocks Carboniferous Raised beach Carboniferous Southern Upland rocks coalfields volcanic rocks Ice flow, drumlin Carboniferous Devonian Fault oilshale field sandstones 3 The Arthur’s Seat volcano Volcanoes Create the Seven Hills Volcanoes in the heart of the city of Edinburgh? Yes, but Edinburgh’s volcanoes are very ancient.