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E D E N S t a t e I N B U R G H N a t u r a l V I R O N M E S e t t i n g o f t h e Geology and Minerals E n v i r o n m e n t ’ S N T A u d i t 12 Geology and minerals Introduction 12.1 Edinburgh’s underlying geology has shaped its landscape and setting which in turn has influenced the nature and form of the city’s built environment. It has helped to make it an attractive city in which to live and work, and one which attracts thousands of visitors each year. 12.2 The city is said to have been built on seven hills, the first to be developed being the Castle Rock on which Edinburgh castle sits. The development of the ‘New Town ’in the 19th and 20th centuries saw Calton Hill followed by the other six hills being absorbed into the city. Most of these landforms are volcanic in origin and were subsequently affected by erosion, in particular owing their current form to glacial moulding. 12.3 Because of their height the Pentland Hills, while mostly outside the city boundary, dominate views to the south. To the north the city overlooks the the Firth of Forth, a broad sea inlet. 12.4 While some underground mining took place in Edinburgh in the past, most large scale activity took place outside the city. The thick sequences of carbon-rich sedimentary rocks which underlie Edinburgh and the Lothians has been a source of oil, gas and coal. The oil shale industry was an important part of the West Lothian economy until the 1960s. While no deep mines are now operational in central Scotland, a limited amount of open-cast coal mining takes place in Midlothian. 12.5 Stone for building, aggregate and lime has been extracted throughout the area, although in Edinburgh this is limited to the quarrying of a small amount of hard rock on the city’s west side. Modern limestone extraction for cement takes place near Dunbar in East Lothian. 12.6 While geology has helped to underpin the city’s success, contributing to its wealth and prosperity, it has also had a number of negative impacts. Many of the city’s historic buildings which were constructed from locally quarried sandstones are now in a poor state of repair and require urgent attention. Because the original sources of stone are no longer available, carrying out repairs is often a problem due to the lack of suitable matches from quarries outside the Lothians. 12.7 Edinburgh’s mining legacy and other factors have caused ground stability problems in parts of the city where building settlement is a major problem. Geology 12.8 The rocks underlying the Edinburgh area are typical of those found in the geological heartland of Scotland, the Midland Valley. These belong to two main geological periods : the Devonian and the Carboniferous, covering a time span from about 415 million years ago to about 300 million years ago. The area has also been affected by Quaternary glacial activity (2 million years to present). 12.9 The geographical distribution of the rocks referred to above is shown in Map 1. The geological divisions are illustrated in Table 1. Map 1: Geology of Edinburgh and the Lothians source : Lothians Landscape Character Assessment, 1998 (Scottish Natural Heritage / Ash Consulting) Table 1: Geological Divisions Devonian 12.10 The oldest rocks in the Edinburgh area are Devonian age (ca. 415 M years old). Lower Devonian lavas including basalts, andesites and acid lavas and tuffs were produced by volcanoes. These deposits formed the Pentland Hills, Braid Hills and Blackford Hill. Carboniferous 12.11 The Lower Devonian rocks were unconformably overlain by a sequence of sedimentary rocks including conglomerates from alluvial fans, red continental sandstones (typically seen in the Craigmillar and Dreghorn areas) and coastal plain siltstones and mudstones (referred to as the ‘cementstones’ of central Edinburgh). All these were laid down in a semi-arid climate. 12.12 Most of the rocks in the Edinburgh area are Carboniferous in age (365-290 m years old). The region was volcanically active during the early Carboniferous period, around 350 million years ago. The small volcanoes of Arthur’s Seat and Calton Hill, Castle Rock and West and East Craiglockhart were briefly active, laying down lava flows and volcanic ash. At various times subsequently, molten rock was also intruded between layers of sedimentary rock to form igneous sills of dolerite, the best example being Salisbury Crags. These also form other prominent landforms such as Corstorphine, Mons, Craigie and Dalmahoy hills. 12.13 The younger sedimentary rocks were formed by the erosion of the remnant mountains as far away as Scandinavia which were deposited on plains with rivers, shallow lagoons and seas. The period was characterised by rapidly changing environments, leading to alternating layers of rock. 12.14 During two eras extensive peat mires formed from the luxuriant and fast growing tropical vegetation that thrived in a ‘greenhouse environment’. These coal forests gave rise to thick coal seams in sequences known as the Limestone Coal Formation and the Coal Measures. Methane and carbon dioxide gas are usually associated with coal seams and were sometimes problematic during past mining activity. Parts of the city underlain by coal and oil shale bearing rock have been considered moderately prone to gas emission and oil seep. 12.15 Tropical seas encouraged thick limestones to form with corals, shells and sea-lilies as in the Lower Limestone Formation. The Balm Well at Liberton and St Bernard’s Well at Stockbridge illustrate the minor pollution of groundwater by oil and gas seepage from the West Lothian oilshale formation. Oil-shales were deposited by massive algal blooms in lakes. Some sandstones were laid down along coastal beaches; most were deposited by rivers and in deltas - some containing trees carried down by the floods. Thick, hard, fine-grained sandstones such as Craigleith and Hailes, which were used as building stones, were formed during this period. 12.16 At the end of the Carboniferous period no further rocks are known to have been laid down in the Edinburgh area, which remained as land from the post-Carboniferous mountain-building to the present day. However, massive compressive forces produced by the collision of ancient continents crumpled and uplifted the sedimentary and volcanic strata. The rocks, previously horizontal, were tilted and folded into basins, arches and domes, and when the stresses became too great, they were fractured and faulted. As a result of this phase of activity, the Carboniferous rocks occupy broad tracts trending roughly north to south. In the west they dip gently to the west beneath areas of farmland; in the east they dip steeply to the east from the Lower Devonian lavas of the Pentlands (and the Pentland Fault). Quaternary 12.17 Like most of northern Britain during the last 2 million years, Edinburgh has been repeatedly buried under an ice cap hundreds of metres thick. The latest melted as recently as 15,000 years ago. As each ice-age began, ice built up in the Highlands and Southern Uplands, merged in the Midland Valley and flowed generally eastwards across Edinburgh. The weight of the ice selectively eroded the softer sedimentary rocks, leaving the harder volcanic rocks accentuated as hills. All these hills have a ‘tail’ to the east (lee) side forming a feature known as a ‘crag and tail’; the best examples being Edinburgh Castle and the Royal Mile and Blackford Hill. 12.18 The ice sheets left extensive areas of glacial debris called till or boulder clay, a mixture of tough clay, rock flour made from ground-down mudstone and siltstone, together with rounded pebbles and boulders of sandstones, lavas and dolerite. This was deposited on much of the low-lying ground. Exceptionally on the south side of the city, by the bypass at Straiton, thick deposits of sand and gravel are overlain by glacial till. A late resurgence of ice re-advanced across this area. 12.19 Long, oval ridges called drumlins fashioned by ice cover much of western Edinburgh. The ice also left scratches (striae) on the harder rocks as a record of its passage. Glaciated ‘pavements’ are visible on Corstorphine Hill. 12.20 Between ice-ages and following the last ice-age, warmer spells allowed the ice to melt, producing vast amounts of water. This cut new channels to lower ground such as the Hermitage of Braid. The meltwater carried large amounts of sediment, the coarser parts of which were deposited as bedded sand and gravel e.g. in Fairmile Park; the finer parts as silts and clays. 12.21 Postglacial lakes (or lochs) also existed. These took the form of hollows formed in the ice scoured landscape into which water flowed. All except Duddingston Loch have been drained or filled naturally with clays, silts and sands, their former locations being marked by alluvial flats. The largest lochs were at Corstorphine, Gogar and Turnhouse. The Borough Loch is now the Meadows, the Nor’ Loch became Princes Street Gardens. Stream sediment analysis carried by the BGS in 1995 showed that these contained four times the national average concentrations of potentially harmful elements (As, Cd, Cu, Pb, Zn) in parts of the city. 12.22 Sea levels have risen and fallen several times since the end of the ice-age due to the ice taking water from the oceans and the weight of it pressing down on the land which later rebounded (‘isostatic recovery’). Falling sea levels caused some rivers to cut deep gorges in the rocks e.g. the River Almond and Water of Leith, where landslip and rockfall still occur. In the Forth Valley, local sea level was high (about 40 m OD) as the ice retreated. Consequently, raised beaches formed and estuarine deposits accumulated inland of the present coastline. Economic Geology Building Stones 12.23 The predominant building stone in Edinburgh is sandstone. This was quarried most recently at Hailes, Redhall, Ravelston, Craigleith and Craigmillar. Craigleith was the largest and best known of Edinburgh's quarries having a world-wide reputation for producing building stone of the highest quality. It provided most of the building stone for Edinburgh's New Town in the 18th and 19th centuries, and exported stone to London, Europe and the United States. The quarry was active for over 300 years and the final massive hole had faces 110 metres (360 feet) high. Filled with inert waste in the 60 years after quarrying ceased, it has now become the Craigleith Retail Park, opened in 1993. 12.24 Between 1835 and 1865, several fossils of the giant tree (Pitys withamii) were discovered within the quarried sandstone at Craigleith. The largest, known as the Craigleith Tree, is now on display in the Royal Botanic Gardens, Edinburgh. To commemorate the discovery of the fossils, the wall by the doorway to Sainsbury’s supermarket in the retail park has been embellished with carvings of Carboniferous tree stems and leaves. Along the pavement are planted a row of the primitive tree, Dawn Redwood (Metasequoia glyptostroboides), once thought to be extinct and only known from fossils, but found growing in China in 1941. 12.25 The advent of canal, rail and finally road transport allowed stone to be carried from further afield, including from the west of the city at Binny, Humbie and Dalmeny. As many Scottish quarries closed, sandstones were brought from quarries in the north of England e.g. from Doddington near Wooler. Modern buildings in the city are commonly clad with marble, limetone and granite (polished) but the stone is not sourced locally. 12.26 Research carried out by the BGS in collaboration with Historic Scotland and the Edinburgh World Heritage Trust examined previous repairs to over 90 buildings in the Edinburgh New Town. This area, part of a UNESCO World Heritage Site, is an important commercial and residential area within the city. The study showed that the use of inappropriate materials for repairs can result in further damage, and makes recommendations for improved decision-making in the selection of stone for repairs. The work was published in 2004 by Historic Scotland as a Research Report. Mining 12.27 Much of the mining which has taken place in Edinburgh occurred prior to the point at which it was a legal requirement to keep accurate plans of the extent and distribution of mines. The absence of mine abandonment plans causes difficulties and often it is only following an event such as an incidence of subsidence that investigations reveal the extent of mining in an area, although the distribution and extent of quarries sometimes gives an indication of the likely distribution of underground mining. The British Geological Survey holds a database which contains details of old mineral workings (see Map 2 which shows locations in Edinburgh). A table listing quarries and former quarries, as identified on large scale Ordnance Survey maps of Edinburgh, is attached as an Appendix to this chapter. Many are very small, and in many cases there is little if any visual trace of the former activity on these sites. 12.28 The ‘Midlothian Coalfield’ has been worked extensively for coal from the surface and by deep mining since medieval times. Deep coal mines were formerly located at Gilmerton, Newcraighall and Niddrie within the city boundary. 12.29 Limestone was also quarried and mined from the 17th century until the 1960’s. The extraction by both quarrying and mining in the Gilmerton area is amongst the earliest examples of such activity recorded in the Lothians. The ‘Gilmerton Limestone’ seam was commercially important for producing lime which was used for iron-making and for making mortar. Limestone seams cross south-east Edinburgh, running broadly in a south-west to north-east direction, in close association with coal. The ‘Burdiehouse Limestone’ which lies about 420 metres below the Gilmerton Limestone was also mined and quarried extensively in the Gilmerton-Straiton area and the adjacent part of North Midlothian. Map 2 : Mineral Sites in Edinburgh source : British Geological Survey 12.30 Where minerals lay close to the ground surface, the most economical method of extraction was quarrying, and quarries were established at several locations in the Gilmerton area. A method of mining commonly adopted in the area was the ‘stoop and room’ technique, also known as ‘room and pillar’ or ‘pillar and stall’. Tunnels were driven into the seam from several points along the quarry face, to the full 3 metres height of the workable material. These were connected at intervals with further tunnels driven at right angles to the first set of tunnels, creating in plan view an irregular rectilinear grid. The rock between the tunnels was left in place as pillars to support the overlying rock. 12.31 Because of the thickness and perceived strength of the over-lying strata, and the value of the mined material, up to 90% of the area of the seam was mined, leaving just 10% as pillars. Historical accounts suggest that such mines may have been developed by initially leaving wide, relatively safe, pillars but then reducing their circumference by further extraction in the final period before the mines were abandoned. This would inevitably reduce the stability of the overlying rock layers making later subsidence a serious possibility. 12.32 Two types of subsidence would normally be expected above room and pillar mining. In the first of these, the roof between adjacent pillars can fail in time. As the overlying rock falls into free space, it tends to increase in bulk, and so it can eventually block and stop the failure. In this way the effect of failure and subsidence decreases as the failure moves up towards the surface. Thus the deeper the mine workings, the less the amount of subsidence occurs on the surface. In the second type of subsidence, the rock falls into a void which is big enough to accommodate all the debris, and a void migrates as a chimney to the surface. Normally this occurs over intersections of rooms in the mine, and above relatively shallow mines. 12.33 In November and December 2000, a series of ground settlements in the Ferniehill area of southeast Edinburgh caused by the progressive collapse of long-abandoned underground limestone mines which had been worked from the face of former quarries, resulted in serious damage to a number of houses. No residents were injured, but they had to be evacuated at short notice and 33 properties had to be demolished immediately. Other houses also had to be vacated and demolished, displacing the residents of a further 189 homes. Hard Rock 12.34 Quarrying for hard rock (mainly the intrusive igneous rock known as dolerite) for use in the construction industry takes place at a number of locations, mainly in rural west Edinburgh (see Map 2). A significant proportion of these deposits lie under parts of the Green Belt, Areas of Great Landscape Value, wildlife sites and SSSIs, prime quality agricultural land, areas of archaeological significance and historic and designed landscapes. While this may have a potential effect on the landscape it also means that there is little conflict with other development which would preclude future mineral extraction as these areas are already protected by various national and local policies. Potentially, new technology could be available in the future which would allow extraction in such areas where at the moment it would not be environmentally sound to do so. 12.35 The Environment Act 1995 included a requirement for mineral planning authorities to review old planning permissions granted in the period 1948 to 1982. These provisions were subsequently consolidated in section 74 and Schedules 9 & 10 of the Town and Country Planning (Scotland) Act 1997. A distinction was drawn up between active and dormant mineral workings. For dormant sites, no minerals development may be lawfully carried out until such time as a new scheme of conditions has been submitted to, and approved by the planning authority. For active sites, the review was progressed in 2 successive three-year phases. • Phase 1 sites are those where the predominant permission was granted between 1948 and 1969, but also includes sites within various designated areas of scenic or nature conservation interest • Phase 2 sites are those where the predominant permission was granted between 1969 and 1982 12.36 In a review carried out by the Council in response to this classification, three active or operational quarries were identified : • Hillwood, Ratho (not currently in production) (Tarmac Ltd.) • Bonnington Mains (Russell RMC) • Ravelrig (Tarmac Ltd.) 1.2 km. west of Balerno In January 2008 Tarmac submitted a planning application to extend Ravelrig Quarry to the west, south and east. If approved, this would extend its productive life from 2009 to 2019, yielding high quality aggregates for the construction industry. When production has ceased, the owners propose to restore the quarry to form a nature reserve, with footpaths and public access facilities. The reserve would incorporate a diverse range of wildlife habitats, including a new loch, woodland, scrub, grassland, rocky outcrops, and cliff faces. 12.37 A further three sites were categorised as ‘dormant’ in the Council review : • Craigiehill • Torphin • Craigpark 12.38 Planning consents at Craigpark and Torphin quarries have now lapsed. It is proposed to restore Torphin for recreational purposes, the area having been identified as a local nature conservation and RIGS site. Craigpark Quarry has a valid planning consent for housing. 12.39 Some examples of quarries which are no longer operational and are being used for other purposes include : • Ratho Quarry now accommodates the ‘Edinburgh International Climbing Arena : Ratho’, the world’s largest indoor climbing arena • Braehead Quarry is a civic amenity site near Cammo • Hailes Park (former quarry and landfill site) to become a new greenspace project being undertaken by a trust on behalf of CEC 12.40 Crushed rock and other materials such as sand and gravel are important sources of aggregates, a steady supply of which is required to support the construction of new buildings and any associated infrastructure. The recycling and reuse of construction waste and the promotion of renewable energy alternatives may result in a future reduction in demand for primary mineral resources. 12.41 Scottish Planning Policy SPP4, ‘Planning for Minerals’, which was published by the Scottish Executive in Sept 2006 says that the new city region authorities, which will prepare strategic development plans (replacing structure plans) should maintain a minimum 10 year supply of construction aggregates to ensure continuity of supply, subject to other planning considerations. Other mineral activity 12.42 Other historical mineral activity includes: • Oil shale extraction (Queensferry area) • Clay (Portobello and Granton areas) in connection with pottery making • Sand and gravel (New Hailes, Mortonhall, Fairmile) Hydrogeology 12.43 As already indicated Edinburgh has a wide range of sedimentary and igneous rocks which show a variation in their water bearing capacity. However, only a small proportion of rain water soaks into the ground and enters the groundwater system where it is held within rocks or sand and gravel deposits. Anthropogenic barriers such as asphalt roads and surfaced pavements combined with drains and storm water and naturally occurring materials such as boulder clay each form a barrier to infiltration. 12.44 Within the city there are four main types of aquifer, though none are comparable with the highly productive aquifers located in other parts of Scotland. 12.45 The first type of aquifer may be found in the Devonian volcanic rocks of the Pentland Hills and the smaller volcanic hills of the Carboniferous where the rocks have a tight crystalline structure which have a low porosity and are relatively impervious to water. Therefore any small amounts of water in these rocks are limited to faults, cracks and fissures. These may be seen as seepages from rock faces eg. Arthur’s Seat, Castle Rock, and springs / wells on Corstorphine Hill. 12.46 A more important source are the early Carboniferous red sandstones which are seen in exposures along the city by-pass and are present beneath Craigmillar and parts of the city centre. These rocks which are relatively porous and permeable were exploited by many breweries in the 18th and 19th centuries as a good source of brewing water. The Grassmarket, Holyrood and Craigmillar areas were considered more favourable than others for obtaining good supplies from deep well and boreholes, although most of these sources are now disused. The sandstone aquifers are classified as being in the range moderately to highly vulnerable to pollution depending on the permeability of the rock and thickness of the clay or mudstone cover. 12.47 Carboniferous silts and mudstones underlying much of the west and north sides of the city are interbedded with sandstones of varying thicknesses. However, these have limited water storage capacity as they are not particularly porous. The rocks of the Midlothian Coalfield on the eastern side of the city were never sourced because of the number of mine workings in the area. 12.48 The unconsolidated sands and gravels that underlie the small flood plains of the River Almond, Water of Leith and Braid Burn are the fourth aquifer type. Since these are close to rivers under low-lying ground, the water table is normally close to ground level and almost at the same level as the river. However, groundwater in these aquifers is vulnerable to pollution at the surface. Radioactivity 12.49 On average, natural sources account for 82% of the annual radiation dose received by Scottish residents. These include cosmic rays, gamma rays and radon, with radon alone contributing 43% of the total. Radon is a radioactive gas emitted from very small amounts of uranium which are naturally present in materials such as rocks, soils, bricks and concrete. As it decays it emits short-life products that tend to accumulate within buildings, potentially exposing occupants to a higher risk of lung cancer. Normally, concentrations do not present a significant risk. However, where they exceed 200 Bequerels per cubic metre of air the Health Protection Agency (National Radiological Protection Board prior to 2005) recommends that relatively simple and inexpensive measures should be taken to reduce them below this level. 12.50 Radon emissions are spatially variable, being associated with particular geological formations – especially granite, limestone and metalliferous vein outcrops. Parts of the country where more than 1% of homes are considered to be above the Radon Action Level of 200 Bq/m3 are classified as Radon Affected Areas. Within Scotland this designation only applies to parts of Aberdeenshire and the Helmsdale / Brora area in east Sutherland. Although Edinburgh has some formations with low to moderate radon emission potential (e.g. limestones at Gilmerton and Burdiehouse), there is no evidence of any significant risk. Some parts of the Pentland Hills may have a relatively high radon potential, but these tend not to be inhabited. As Table 2 shows, average radon concentrations in Edinburgh are well below the Action Level. Table 2 : Radon measurements in dwellings by postcode area, Scotland, 1997 Postcode area No. of results Average radon level (Bq / m3) Highest recorded level (Bq / m3) Number above Action Level (*1) 1,123 74 2,200 73 Aberdeen 2,649 68 1,600 148 Galashiels 113 38 290 1 Perth 229 36 310 4 Dundee 104 31 180 0 Dumfries 283 31 150 0 Inverness 392 26 360 0 Edinburgh 92 25 100 0 Lerwick, Shetland 96 23 180 0 Falkirk 81 23 130 0 Motherwell 56 22 75 0 Kirkcaldy 95 17 61 0 Kilmarnock 98 17 58 0 Glasgow 93 15 58 0 222 13 88 0 Kirkwall Paisley source : Scottish Environment Statistics 1998 (*1) n.b. Kirkwall postcode area includes part of mainland Seismic activity 12.51 Earth movements in the Edinburgh area have been localised, low magnitude, and almost exclusively associated with former mining activity in the north Midlothian coalfield. Only the easternmost parts of the city have been affected (Map 3). All events have registered less than 3 on the Richter scale. Being a logarithmic scale this is a very low intensity, with few noticeable effects other than in the immediate vicinity. 12.52 With increasing time since the cessation of mining activity, collapses are tending to occur with diminishing frequency : 35 movements were recorded by the British Geological Survey in the coalfield area in the 1970s, falling to 31 in the 1980s and 9 in the 1990s. In fact the last recorded sign of activity dates back to 1997. Map 3 : Seismic activity in Central Scotland source : British Geological Survey Geology and the Environment Biodiversity 12.53 The diverse topography of the Edinburgh area contains an unusually large number of rock faces for an urban area. This reflects the City’s unique geological history, and in particular the landforms associated with the Arthur’s Seat volcano, including Castle Rock, Calton Hill and Arthur’s Seat itself. Although the most significant rock faces lie inland, a number of smaller coastal cliffs also fall within the city boundary. Steep slopes and screes are also present, often below cliff faces, most notably in Holyrood Park and at Dalmahoy and Hailes. 12.54 Rock faces contain many varied habitats, their diversity arising from variations in slope, aspect, soil composition and microclimate. The presence or absence of disturbance is a key factor. The resulting flora and fauna, though few in number, are often rich in diversity. 12.55 Most of the important sites in the city fall within Sites of Special Scientific Interest (SSSI’s) shown in the Table 3 below: Table 3 : Sites of Special Scientific Interest (SSSIs) in Edinburgh – with details of geological interest Name Interest Agassiz Rock Quaternary. Striated rock surface. Associated with the early development of glacial theory in Scotland Arthur’s Seat Volcano Carboniferous / Permian igneous strata Duddingston Loch Carboniferous / Permian igneous strata Firth of Forth (part of) Biodiversity and geodiversity Inchmickery Islands (Inchmickery and Cows & Calves) Rocky offshore islands of importance as a breeding ground for four species of tern – common, arctic, sandwich and roseate Wester Craiglockhart Hill Lowland grassland habitat source : Scottish Natural Heritage 12.56 In addition there are 13 Local Geodiversity sites covering a range of interest. These include former Regionally Important Geological and Geomorphological Sites (RIGS) as shown in Table 3 below. Table 3 : Local geodiversity sites in Edinburgh, with details of geological interest Name Interest Balm Well Well seeping natural oil Calton Hill Comprises a sequence of lavas and interbedded tuffs in repeated episodes. Crag-and-tail formation. Craigleith Gullane formation (Lower Carboniferous Strathclyde group); sediments including river delta, lacustrine sandstones, siltstones, mudstones (including oil shales) Craigmillar Relationship between the landscape and the underlying stratified rocks, which belong to the Upper Old Red Sandstone or Inverclyde group of the Lower Carboniferous. Corstorphine Hill Illustrates a combination of geomorphological landforms and geological outcrops Dreghorn Link Cutting exposing about 80m of Upper Old Red Sandstone sandstone and shales Ellen’s Glen Exposure of strata Fairmilehead Park Location where large glacial erratics formerly exposed in sandpit Hermitage of Braid Crag-and-tail. Lower Devonian lava flow. Joppa Shore Carboniferous strata and sedimentary rock Ravelston Woods Good example of sedimentary processes of the lower Carboniferous Stones of Scotland Examples of the varied geology of Scotland Torphin Quarry A disused quarry showing three thick basalt lava flows, intervening tuff and barite veins source : City of Edinburgh Council 12.57 The following Edinburgh biodiversity Action Plan species can be found in association with rock faces and screes: Animals: Aelurillus v-insignatus (jumping spider), Ceciliodes acicula (blind white snail), Tetramorium caespitum (ant), Capperia britanniodactyla (plume moth), Glyphiptererix Minorella (micromoth), Plants: spring sandwort, rock whitebeam, rock-rose, maiden pink, sticky catchfly, sieve- tooth moss Regionally Important Geological Sites (RIGS) 12.58 There are now 13 RIGS or ‘Regionally Important Geological and Geomorphological Sites’ in Edinburgh. These are sites which have been identified by locally developed criteria, and are currently the most important places for geology, geomorphology and soils outside statutorily protected nature reserves and Sites of Special Scientific Interest (SSSI). The designation of RIGS is one way of recognising and protecting important Earth science and landscape features for future generations to enjoy. The following RIGS sites are located in Edinburgh : • • • • • • • • • • • • Torphin Quarry (1994) Dreghorn Link (1994) Craigleith (1999) Craigmillar (1999) Hermitage of Braid (2000) Corstorphine Hill (2000) Joppa shore (2000) Calton Hill (2005) Stones of Scotland (2005) Ravelston Woods (2005) Ellen’s Glen (2005) Balm Well (2005) • Fairmile Park – Comiston Sand Pit (2005) Historical Links James Hutton 12.59 Many of the early ideas and discoveries in geology were made in the Edinburgh area by James Hutton (1726-1797), a leading member of the Scottish Enlightenment. In 1788 he published ‘Theory of the Earth’ widely regarded as the foundation of modern geology. 12.60 Hutton used a number of localities to demonstrate his theories including ‘Hutton’s Section’ at the south end of Salisbury Crags. Here he demonstrated that the crystalline rocks of the Crags were formed by the intrusion and cooling of hot molten rock and not, as was the view at that time, from the cold precipitation from salts of the sea. Nearby is ‘Hutton’s Rock’ which he is reputed to have asked the quarrymen to save as it contained a fine example of an iron ore vein. A memorial garden marks the site of James Huttton’s Edinburgh home on St John’s Hill in the Pleasance above Holyrood Road. Agassiz 12.61 Another benchmark in geological understanding occurred in 1840 when the Swiss geologist, Louis Agassiz was able to confirm for the first time that Scotland had once been covered by ice. Striae or ice scratches on what is called Agassiz Rock on Blackford Hill were among evidence he cited for glaciation. APPENDIX : Quarries and former quarries identified on large scale OS maps of Edinburgh Quarries < 0.01 hectares Quarry Barnton Pk. Craigiemill Mortonhall Clove Location Grid Ref. Area (ha.) Status Balerno 314555 666830 0.09 Disused Balerno 318604 664349 0.42 Disused Barnton 319726 675937 0.34 Disused Braid Hills 326083 669675 0.16 Disused Cramond 318217 676318 0.57 Disused Cramond 318500 676476 0.14 Disused Dalmahoy 313371 666906 0.14 Disused Harlaw Res. 318792 665205 0.29 Disused Listonshiels 312862 661371 0.40 Disused Listonshiels 312882 661189 0.12 Disused Listonshiels 313090 661272 0.19 Disused Listonshiels 313131 660963 0.11 Disused Mortonhall 324747 669214 0.67 Disused Newbridge 312817 672204 0.35 Disused Ratho / Newbridge 312666 671164 0.44 Disused S. Queensferry 315388 675825 0.86 Disused Swanston 324583 667231 0.09 Disused History / use Quarries 0.01 to 5.0 hectares Quarry Location Grid Ref. Area (ha.) Status Barnton Barnton 320190 674991 1.86 Disused History / use Bonaly 319999 667583 2.35 Disused Torphin Bonaly 320252 667745 2.40 Disused former whinstone quarry Braehead Cammo 317424 673776 3.28 Disused now landfill & recycling site Lennie Cammo 316852 674092 2.69 Disused Corstorphine Hill 320304 674800 2.30 Disused Craigmillar 328580 670998 3.11 Disused Humbie Kirkliston 310929 675692 1.21 Disused Niddrie Bing Niddrie 330657 671420 3.87 Disused Ratho Ratho 312831 670962 1.23 Disused Ratho 312529 670033 1.41 Disused Location Grid Ref. Area (ha.) Status Blackford 326039 670284 6.45 Disused Craigleith 1.5km NW of city centre 322571 674671 9.84 Disused Craigiehill S. Queensferry 315500 676150 5.65 Disused currently used as national climbing centre Quarries 5.01 to 10 hectares Quarry History / use former sandstone quarry; now retail park Quarries >10 hectares Quarry Location Grid Ref. Area (ha.) Status History / use Ravelrig Balerno 314611 666985 34.01 Operational Bonnington Mains Bonnington / Ratho 312533 670034 14.08 Operational active hard rock quarry Kaimes Kirknewton 313112 666466 19.77 Disused formerly landfil Craigpark Ratho 312809 670514 32.94 Disused 1995 – permission refused for landfill 2005 – premission granted for housing and public amenity Hillwood Ratho Station / Newbridge 312933 671699 48.00 not in production