geosciences

Review Old Volcanic Stories—Bringing Ancient Volcanoes to Life in Ireland’s Geological Heritage Sites

Matthew Parkes 1,†, Sarah Gatley 2,*,‡ and Vincent Gallagher 2,*

1 Natural History Museum, National Museum of Ireland, D02 F627 Dublin, Ireland 2 Geological Survey Ireland, D04 K7X4 Dublin, Ireland * Correspondence: [email protected] (S.G.); [email protected] (V.G.) † Deceased. ‡ Retired.

Abstract: Active or recently active volcanic areas present very visible and easy to understand phenomena for the broad population to appreciate as geological heritage. However, in a geologically stable country such as Ireland, with no volcanism evident for tens of millions of years and few clearly visible traces of volcanoes of a ‘school textbook’ nature, the significance of ancient volcanic remains is much harder to explain or to present to visitors to geological heritage sites. This paper explores the wide range of evidence of ancient volcanic activity within recognised geological heritage sites across Ireland, both in County Geological Sites and in the UNESCO Global Geoparks. Some of the stories that can be told using the available evidence are documented, including some of the current efforts to present Ireland’s volcanic geological heritage. The stories are told within the context of the geological and volcanic history of Ireland over the past 500 million years. As such, the promotion of


geological heritage is at an early stage, and this contribution may provide inspiration or ideas for
 approaches to this problem for other countries or terrains with similar ancient volcanic rocks. Citation: Parkes, M.; Gatley, S.; Gallagher, V. Old Volcanic Keywords: geoheritage; volcanoes; geopark; county geological site Stories—Bringing Ancient Volcanoes to Life in Ireland’s Geological Heritage Sites. Geosciences 2021, 11, 52. https://doi.org/10.3390/ 1. Introduction geosciences11020052 In County Wicklow, south of Dublin (Ireland’s capital city), is a well-known landmark hill called the Sugarloaf, which is a popular amenity spot for family walks at weekends and Academic Editor: holidays. The name is used for numerous other similarly isolated conical hills in Ireland, Jesus Martinez-Frias but the important point is that, anecdotally at least, the hill is widely held to be an old Received: 25 December 2020 Accepted: 25 January 2021 volcano. Its shape superficially resembles that of a classic cone-shaped Andean volcano, Published: 27 January 2021 so it is perhaps not surprising that this weathered Cambrian quartzite peak has been so mistaken, especially since in the Irish education system, Geology or Earth Science has been

Publisher’s Note: MDPI stays neutral a negligible component of past school curricula. Although the Earth Science content of the with regard to jurisdictional claims in school curriculum has improved slightly in very recent years, there is still a very low level published maps and institutional affil- of public awareness of Geology as a science in its own right, or as a foundation component iations. to many other sciences. It is from this very low base that this contribution is framed, exploring how ancient volcanic rocks and phenomena are presented to the general public across a wide range of geological heritage sites and UNESCO Global Geoparks. The critical point to note here is that the island of Ireland is situated on geologically stable crust, with the opening Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. of the North Atlantic Ocean some 60 million years ago being the last event to leave a This article is an open access article volcanic imprint. The Giant’s Causeway, a UNESCO World Heritage Site in County distributed under the terms and Antrim, Northern Ireland (see Section 3.3), is the exceptional public face of that significant conditions of the Creative Commons event. However, most volcanic rocks in the Republic of Ireland (ROI) are much older and Attribution (CC BY) license (https:// have typically been affected by deformation and metamorphism. Apart from the Giant’s creativecommons.org/licenses/by/ Causeway, there are few sites that present obvious volcanic features in the way that a 4.0/).

Geosciences 2021, 11, 52. https://doi.org/10.3390/geosciences11020052 https://www.mdpi.com/journal/geosciences Geosciences 2021, 11, 52 2 of 22

visitor to Mount Teide in Tenerife, Mount Etna in Italy or many other popular holiday destinations with active or recently active volcanoes can experience. This contribution describes how volcanic geoheritage is being presented and explained in some sites in Ireland (ROI), and how it may be ‘sold’ to the public in other, less obvious places, were there resources available to do so. It is about the stories that can be told to fire the imagination of residents and visitors alike with a vision of past volcanoes at those sites. It is not a systematic review of volcanic sites in Northern Ireland, which has a different legislative scheme for geoheritage sites, (see Section 2.2), but the Giant’s Causeway has been used to complete the volcanic history of the island of Ireland and to illustrate issues of site interpretation and promotion.

2. Geological Heritage Sites in Ireland 2.1. Ireland’s County Geological Sites (CGS) Initial approaches to geoconservation in Ireland through the Irish Geological Heritage Programme (Geological Survey Ireland) were described by Parkes and Morris [1,2] and fur- ther documented in Parkes [3]. The official status of geological heritage programme efforts was recorded in the ProGEO manual of Geoconservation in Europe [4]. Original plans for the designation of statutory geological Natural Heritage Areas failed to progress [5,6] and County Geological Sites (CGS) have become the only effective current geological heritage site designation in Ireland [6]. Although non-statutory in character, CGS do receive an effective degree of protection through incorporation into statutory County Development Plans. The inclusion of CGS into statutory County Development Plans and within the plan- ning system means that no significant development may occur without some consultation with Geological Survey Ireland about the site’s geological heritage value. There are no specific restrictions on what a landowner can do in relation to a County Geological Site. Any proposed development that requires planning permissions simply flags the geological heritage interest of the site and allows it to be factored into any decision along with any other competing interests and values. From an initial audit of County Sligo’s geological heritage in 2004 [7], a programme of county audits has evolved such that after 2020, only three counties, Kerry, Cork and Limerick, remain to be audited (Figure1). Whilst there will be a need to revisit some of the earliest audited counties to take account of new geological knowledge, as well as a more expanded view of the CGS criteria applied in the majority of counties, there is already a very good cross-section of volcanic sites identified to provide the examples discussed below. On the conclusion of a county audit, a geological heritage report on the whole county and individual reports for each County Geological Site (CGS) are published on the Geolog- ical Survey Ireland website [8]. Each CGS report normally has one page of text defining the site and its scientific interest. This page also includes some brief guidance in terms of promotion and management of the site. An additional page of photographs and a page of maps at different scales complete the report. The report provides adequate detail in largely non-technical language for planning professionals in the County Council to use the data in their policies and practice. The Irish Geological Heritage Programme of Geological Survey Ireland has considered Ireland’s geological heritage under 16 geological themes. Whilst many volcanic-interest sites have been defined as CGS under the IGH11 Igneous Intrusions theme, others fall into the various stratigraphical themes (e.g., IGH4 Cambrian-Silurian, IGH10 Devonian, etc.). Many CGS do of course have an interest across two or more geological themes. GeosciencesGeosciences 20212021,, 1111,, x 52 FOR PEER REVIEW 33 of of 23 22

FigureFigure 1. 1. LocationLocation of of counties counties and and main main volcanic volcanic sites sites in in Ireland. Ireland. 2.2. Northern Ireland’s Areas of Special Scientific Interest (ASSI) On the conclusion of a county audit, a geological heritage report on the whole county This review covers the volcanic geoheritage mainly in Ireland (ROI). As a part of and individual reports for each County Geological Site (CGS) are published on the Geo- the United Kingdom, Northern Ireland has its own scheme of statutory ASSIs—Areas of logical Survey Ireland website [8]. Each CGS report normally has one page of text defining Special Scientific Interest (very similar to the statutory Sites of Special Scientific Interest the site and its scientific interest. This page also includes some brief guidance in terms of (SSSI) defined under the Geological Conservation Review in England, Scotland and Wales). promotion and management of the site. An additional page of photographs and a page of There is a range of sites with different interests in Northern Ireland, but in Country Antrim, maps at different scales complete the report. The report provides adequate detail in especially, there are numerous sites associated with the Paleogene volcanism of circa largely non-technical language for planning professionals in the County Council to use 60 million years ago during an initial phase of rifting related to the opening of the North theAtlantic data in Ocean. their policies and practice. TheThe Irish listing Geological of ASSIs Heritage includes 12Programme sites for Caledonian of Geological igneous Survey geology Ireland and has at consid- least 27 eredfor PalaeogeneIreland’s geological igneous geology, heritage along under with 16 severalgeological other themes. igneous Whilst sites undermany othervolcanic-in- themes. terestThe Earthsites have Science been Conservation defined as CGS Review under (ESCR) the IGH11 [9] has Igneous also identified Intrusions numerous theme, others other fallsites into that the have various not yetstratigraphical been designated themes as (e.g., ASSIs IGH4 but whichCambrian-Silurian, may be in future. IGH10 The Devo- ASSI nian,sites etc.). are more Many integrated CGS do of as course natural have heritage an interest sites, across with many two or having more geological biodiversity themes. (plant communities or bird habitats) importance as well as geodiversity. Some are also classified 2.2.and Northern protected Ireland’s as National Areas Nature of Special Reserves, Scientific such Interest as Tardree (ASSI) Quarry, which exposes rhyolite. A reviewThis review of the manycovers promotional the volcanic effortsgeoheritage on Northern mainly in Ireland’s Ireland volcanic (ROI). As sites a part is outside of the Unitedthe scope Kingdom, of this paperNorthern but isIreland desirable. has its own scheme of statutory ASSIs—Areas of Spe- cial Scientific Interest (very similar to the statutory Sites of Special Scientific Interest (SSSI) defined3. Ireland’s under Volcanic the Geological Heritage Conservation Review in England, Scotland and Wales). There Ireland’sis a range geological of sites with heritage different stretches interests back in almostNorthern two Ireland, billion but years in Country and includes An- trim,numerous especially, traces there of volcanic are nume activityrous sites (Figure associated2). Of with most the significance Paleogene from volcanism a geoheritage of circa 60perspective million years are ago those during produced an initial during phase two of periodsrifting related that saw to the the opening closure of the one North ocean, Atlanticthe Iapetus, Ocean. and the opening of another, the Atlantic. In between them, the deposition of sediments in the shallow tropical seas of the Carboniferous period was interrupted by

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The listing of ASSIs includes 12 sites for Caledonian igneous geology and at least 27 for Palaeogene igneous geology, along with several other igneous sites under other themes. The Earth Science Conservation Review (ESCR) [9] has also identified numerous other sites that have not yet been designated as ASSIs but which may be in future. The ASSI sites are more integrated as natural heritage sites, with many having biodiversity (plant communities or bird habitats) importance as well as geodiversity. Some are also classified and protected as National Nature Reserves, such as Tardree Quarry, which ex- poses rhyolite. A review of the many promotional efforts on Northern Ireland’s volcanic sites is outside the scope of this paper but is desirable.

3. Ireland’s Volcanic Heritage Ireland’s geological heritage stretches back almost two billion years and includes nu- merous traces of volcanic activity (Figure 2). Of most significance from a geoheritage per- Geosciences 2021, 11, 52 4 of 22 spective are those produced during two periods that saw the closure of one ocean, the Iapetus, and the opening of another, the Atlantic. In between them, the deposition of sed- iments in the shallow tropical seas of the Carboniferous period was interrupted by a third phasea third of phasevolcanism, of volcanism, responsible responsible for several for significant several significant volcanic volcanicheritage heritagesites in Ireland sites in (FigureIreland 1). (Figure 1).

FigureFigure 2. 2. SimplifiedSimplified geology, geology, UNESCO UNESCO Global Global Geopar Geoparksks and and World World Heritage Heritage Site Site (WHS) (WHS) in in Ire- Ireland land[ISZ [ISZ = Iapetus = Iapetus Suture Suture Zone]. Zone]. 3.1. The Iapetus Ocean: Subduction Zones and Island Arc Volcanoes 3.1. The Iapetus Ocean: Subduction Zones and Island Arc Volcanoes The Iapetus Ocean separated the continent of Laurentia, comprising present-day The Iapetus Ocean separated the continent of Laurentia, comprising present-day ar- areas of Scotland, the north of Ireland, Greenland and North America, from another large eas of Scotland, the north of Ireland, Greenland and North America, from another large continent to the south, known as Gondwana, and two smaller continents, Baltica and Avalonia. The ocean reached a maximum width of around 5000 km some 500 million years ago before it began to close. Closure occurred over a period of 100 million years and saw the ocean crust subduct beneath the continents, culminating in continental collision. As at tectonic plate margins such as the Pacific Rim today, chains of volcanoes developed above the subduction zones. The volcanic eruptions that occurred as the ocean closed are now part of the volcanic heritage preserved in Ordovician and Silurian rocks on both sides of the former ocean. Continental collision led to the Caledonian orogeny and the intrusion of large volumes of granitic rocks. The line of closure, or suture, of the former Iapetus ocean runs northeast-southwest through the centre of Ireland (Iapetus Suture Zone—ISZ, Figure2). The volcanic rocks to the north of the suture are found in locations stretching from the east coast to the west coast. Those to the south of the suture occur largely in the east and southeast of the country but can be traced to the west coast. Geosciences 2021, 11, 52 5 of 22

3.1.1. The Northern Margin of the Iapetus Ocean The Longford-Down Inlier extends across counties Longford, Cavan, Monaghan and Louth in Ireland and Armagh and Down in Northern Ireland. It comprises Ordovician and Silurian greywackes that were deposited on the Iapetus Ocean floor before being stacked up above the subduction zone as the ocean closed, as well as volcanic rocks erupted from the island arc volcanoes that also developed above the subduction zones. Bruse Hill Quarry in County Cavan [10] exposes Ordovician green greywackes, red shales and minor spilitic lavas, providing an accessible view of the rocks associated with ocean closure and thought to have been deposited in water depths of over 4000 m. This abandoned quarry is not currently promoted on site for its geological heritage but is cited as part of the ‘Drifting Apart Story’ (see below). In contrast, Carrickatee Hill in neighbouring County Monaghan [11] exemplifies some of the difficulty in telling old volcano stories that will capture public imagination and potentially engage them in geoscience, even at a very superficial level. Here, pyroclastic agglomerates are exposed on the sides of a small, wooded hill. They are among possibly the best exposures of Ordovician volcanic rocks in the Longford-Down Inlier. However, Carrickatee Hill is quite remote from any standard tourism sites in the country and does not have other characteristics of heritage value. Aside from any issues of physical access and land ownership, it is arguable that despite the good representation of part of Ireland’s geological history, the complexity of the whole story is quite difficult to simplify for the wider public. Some volcanic stories are more difficult to relate meaningfully and may be better left to geology students and researchers. Finny (Figure3) is one of the classic stops on geology student field trips in County Mayo [12]. It displays some easily accessible roadside exposures of Ordovician pillow lavas. These are featured in some geological field trip guides and are an asset for the Joyce Country and Western Lakes geopark project. The shapes of the pillow lavas are sufficiently clear to allow any non-specialist to appreciate that they are tubular lava flows, originally Geosciences 2021, 11, x FOR PEER REVIEWerupted into water, with chilled margins from contact with the water. In addition, adjacent6 of 23

exposures are volcanic agglomerates, adding to the interest in a very small area.

FigureFigure 3. 3.Finny, Finny, County County Mayo: Mayo: roadside roadside outcrop outcrop of of Ordovician Ordovician pillow pillow lavas. lavas.

KillaryKillary HarbourHarbour onon the west coast coast is is well well known known as as Ireland’s Ireland’s fjord, fjord, and and there there are are nu- numerousmerous other other geodiversity geodiversity interests interests in in and and around around it. However, therethere isis oneone placeplace where where itit would would be be very very easy easy to to tell tell an an exciting exciting volcanic volcanic geoheritage geoheritage story. story. A A small small roadcut roadcut and and roadsideroadside quarry quarry near near Killary Killary Harbour Harbour exposes exposes an an Ordovician Ordovician ignimbrite. ignimbrite. Here, Here, the the rock rock itselfitself can can be be seen seen close close up up but but when when the the site site is is viewed viewed from from a a distance distance it it is is clear clear that that the the roadroad cuts cuts through through a a linear linear ridge ridge that that continues continues east east and and west. west. Further Further examination examination shows shows that on the skyline to the west, there are five prominent ridges. Each of these distinctive landform features is formed by ignimbrite. The whole assemblage is worthy of some in- terpretation for tourists driving through this popular route. Television images of active pyroclastic flows during volcanic eruptions are perhaps familiar enough to suggest that this would be a good place for visitors to imagine this happening in Ireland some 460 million years ago. County Galway is one of the most complex and diverse geological areas in Ireland and has many more CGS than most. Of these, there are numerous sites that fall within the Igneous Intrusions Theme (IGH11), with many from the large Caledonian Galway Granite area of south Connemara. However, few of these have been related to volcanic activity and even the quite numerous dyke intrusions in the region are interpreted as being related to late-stage granite intrusion. The one CGS that hosts significant volcanic rocks is Gorumna Island (Figure 4) [13], where the well-exposed bedrock comprises a complex sequence of basic volcanic rocks, amphibolite sills and deep-water sedimentary rocks. These are interpreted as having formed in a volcanic arc on the northern margin of the Iapetus Ocean and have been correlated with similar rocks in the Longford-Down inlier. This site, as well as providing relatively rare exposures of volcanic rocks in Galway, also exemplifies how volcanic rocks can contribute to our understanding of large-scale crustal development over millions of years.

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that on the skyline to the west, there are five prominent ridges. Each of these distinctive landform features is formed by ignimbrite. The whole assemblage is worthy of some interpretation for tourists driving through this popular route. Television images of active pyroclastic flows during volcanic eruptions are perhaps familiar enough to suggest that this would be a good place for visitors to imagine this happening in Ireland some 460 million years ago. County Galway is one of the most complex and diverse geological areas in Ireland and has many more CGS than most. Of these, there are numerous sites that fall within the Igneous Intrusions Theme (IGH11), with many from the large Caledonian Galway Granite area of south Connemara. However, few of these have been related to volcanic activity and even the quite numerous dyke intrusions in the region are interpreted as being related to late-stage granite intrusion. The one CGS that hosts significant volcanic rocks is Gorumna Island (Figure4)[ 13], where the well-exposed bedrock comprises a complex sequence of basic volcanic rocks, amphibolite sills and deep-water sedimentary rocks. These are interpreted as having formed in a volcanic arc on the northern margin of the Iapetus Ocean and have been correlated with similar rocks in the Longford-Down inlier. This site, as well as providing relatively rare exposures of volcanic rocks in Galway, also exemplifies how Geosciences 2021, 11, x FOR PEER REVIEWvolcanic rocks can contribute to our understanding of large-scale crustal development over7 of 23

millions of years.

FigureFigure 4. 4.Gorumna Gorumna Island,Island, CountyCounty Galway: Galway:Ordovician Ordovicianvolcanics volcanics (green) (green) cross cross cut cut by by granite. granite.

3.1.2.3.1.2. TheThe SouthernSouthern MarginMargin ofof thethe IapetusIapetus Ocean Ocean Northeast Ireland (ROI) NortheastOne of Ireland the easiest (ROI) single features with which to explain volcanic rocks to the public is foundOne in of the the grounds easiest single of Ardgillan features House with which (Figure to5)[ explain14] on volcanic the north rocks coast to of the County public Dublin.is found Thein the house grounds is owned of Ardgillan by Fingal House Council (Figure and 5) run[14] ason a the public north park coast and of County visitor attraction.Dublin. The On house the routeis owned between by Fingal the carCouncil park and and run the as House a public is a park large and boulder visitor which attrac- wastion. collected On the route from abetween nearby the beach, car inpark the and mistaken the House impression is a large that boulder its concentric which circularwas col- patternslected from were a nearby some ancient beach, in Celtic the mistaken carvings. impression They are inthat fact its theconcentric weathering circular pattern patterns of pillowwere some lavas ancient from Ordovician Celtic carvings. volcanoes They that are erupted in fact the in the weathering area some pattern 460 million of pillow years lavas ago. However,from Ordovician despite volcanoes suggestions that made erupted in the in CGS the area report, some no 460 interpretation million years or explanationago. However, is availabledespite suggestions on site, yet itmade provides in the opportunities CGS report, tono tell interpretation several fascinating or explanation stories in is a available publicly accessibleon site, yet and it provides eye-catching opportunities location. Theto tell boulder several reveals fascinating not only stories its geological in a publicly origin acces- as volcanicsible and lava eye-catching erupted underwater, location. The which boulder is evidence reveals not of the only closure its geol ofogical the Iapetus origin Ocean, as vol- butcanic also lava a more erupted recent underwater, history of which movement is eviden at thece hands of the ofclosure people. of the Iapetus Ocean, but also a more recent history of movement at the hands of people.

Figure 5. Ardgillan House Boulder, County Dublin: weathered Ordovician pillow lavas.

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Figure 4. Gorumna Island, County Galway: Ordovician volcanics (green) cross cut by granite.

3.1.2. The Southern Margin of the Iapetus Ocean

Northeast Ireland (ROI) One of the easiest single features with which to explain volcanic rocks to the public is found in the grounds of Ardgillan House (Figure 5) [14] on the north coast of County Dublin. The house is owned by Fingal Council and run as a public park and visitor attrac- tion. On the route between the car park and the House is a large boulder which was col- lected from a nearby beach, in the mistaken impression that its concentric circular patterns were some ancient Celtic carvings. They are in fact the weathering pattern of pillow lavas from Ordovician volcanoes that erupted in the area some 460 million years ago. However, despite suggestions made in the CGS report, no interpretation or explanation is available on site, yet it provides opportunities to tell several fascinating stories in a publicly acces- Geosciences 2021, 11, 52 sible and eye-catching location. The boulder reveals not only its geological origin as7 of vol- 22 canic lava erupted underwater, which is evidence of the closure of the Iapetus Ocean, but also a more recent history of movement at the hands of people.

FigureFigure 5. 5.Ardgillan Ardgillan House House Boulder, Boulder, County County Dublin: Dublin: weathered weathered Ordovician Ordovician pillow pillow lavas. lavas.

Lambay Island, situated off the coast north of County Dublin [14] is the eroded remains of an Ordovician volcano, located on the leading edge of the Avalonian continental plate. Throughout the Ordovician Period, this small continent was moving northwards as the Iapetus Ocean closed. This level of presentation of the geological history of Ireland is comprehensible to ordinary people, and personal experience has shown that many people are fascinated to learn this story, if it is presented well. Whilst Lambay Island is an understandable story and an important CGS, it presents difficulties too. The island is privately owned and not publicly accessible in general. Therefore, excellent exposures of thin limestone beds with corals draped over andesite lavas, found at the remote eastern tip, are only ever seen by privileged geologists. Furthermore, the island’s somewhat flattened low cone shape, as seen from the mainland, may disappoint those expecting a sight more in keeping with the popular image of a modern volcano. Fortunately, at Portrane Shore CGS [14] on the mainland closest to Lambay Island, an excellent coastal exposure reveals most of the same rocks found on Lambay Island or their more distal equivalents, plus slightly younger carbonate rocks. Although access to some features is controlled by the tides, there is always enough of interest visible from the coastal path around the headland, to be able to present the geology through a guided walk or geological fieldtrip. Every degree of understanding can be catered for here, with many levels of detail to be explored, including the limestones and debris flow deposits that overlie the volcanic rocks. Soft sedimentary structures are abundant and their story can be told as one of instability of sedimentary deposits around the former volcano. Whilst the complexity of geology can be investigated and queried by geological field parties, here, there is clear, simple evidence that can be seen, absorbed and understood by a non-specialist visitor. Several simple guides to this CGS have been published and remain popular with local people [15]. Aside from these sites, pebbles of the distinctive Lambay porphyry (Figure6) are common along the east coast of Dublin and in particular on Killiney beach, a popular ‘outdoor classroom’, from where the volcanic stories can be equally well told. One unique CGS, Bellewstown Quarry in County Meath [16], exposes an inlier of volcanic and sedimentary rocks that existed as a volcanic island in the middle of Iapetus during Ordovician times. Fossil faunas show affinities with other island faunas whilst younger shales reveal the island had later moved closer to the adjacent continents. The Kilsaran International operators of this working quarry agreed a formal proposal to permit access for a GSI (Geological Survey Ireland) and NMI (National Museum of Ireland) research team, and their ongoing cooperation has proved a model of best practice Geosciences 2021, 11, x FOR PEER REVIEW 8 of 23

Lambay Island, situated off the coast north of County Dublin [14] is the eroded re- mains of an Ordovician volcano, located on the leading edge of the Avalonian continental plate. Throughout the Ordovician Period, this small continent was moving northwards as the Iapetus Ocean closed. This level of presentation of the geological history of Ireland is comprehensible to ordinary people, and personal experience has shown that many people are fascinated to learn this story, if it is presented well. Whilst Lambay Island is an understandable story and an important CGS, it presents difficulties too. The island is privately owned and not publicly accessible in general. Therefore, excellent exposures of thin limestone beds with corals draped over andesite lavas, found at the remote eastern tip, are only ever seen by privileged geologists. Fur- thermore, the island’s somewhat flattened low cone shape, as seen from the mainland, may disappoint those expecting a sight more in keeping with the popular image of a mod- ern volcano. Fortunately, at Portrane Shore CGS [14] on the mainland closest to Lambay Island, an excellent coastal exposure reveals most of the same rocks found on Lambay Island or their more distal equivalents, plus slightly younger carbonate rocks. Although access to some features is controlled by the tides, there is always enough of interest visible from the coastal path around the headland, to be able to present the geology through a guided walk or geological fieldtrip. Every degree of understanding can be catered for here, with many levels of detail to be explored, including the limestones and debris flow deposits that over- lie the volcanic rocks. Soft sedimentary structures are abundant and their story can be told Geosciences 2021, 11, 52 as one of instability of sedimentary deposits around the former volcano. Whilst the8 ofcom- 22 plexity of geology can be investigated and queried by geological field parties, here, there is clear, simple evidence that can be seen, absorbed and understood by a non-specialist visitor. Several simple guides to this CGS have been published and remain popular with forlocal operators people of[15]. extraction sites of geological heritage importance. Where promotion is not practicalAside in CGSfrom thatthese are sites, working pebbles quarries, of the GSIdistinctive encourages Lambay the inclusionporphyry in(Figure restoration 6) are planscommon of rock along faces the left east visible coast and of accessible, Dublin and ideally in particular with interpretation on Killiney panels beach, and a viewing popular platforms‘outdoor [classroom’,17]. from where the volcanic stories can be equally well told.

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The Kilsaran International operators of this working quarry agreed a formal proposal to permit access for a GSI (Geological Survey Ireland) and NMI (National Museum of Ireland) research team, and their ongoing cooperation has proved a model of best practice for operators of extraction sites of geological heritage importance. Where promotion is not practical in CGS that are working quarries, GSI encourages the inclusion in restoration plans of rock faces left visible and accessible, ideally with interpretation panels and view- FigureFigure 6. 6.Lambay Lambay Porphyry:Porphyry: volcanic pebble pebble common common on on Killiney Killiney beach, beach, County County Dublin Dublin (Photo: (Photo: S. ingGatley). platforms [17]. S. Gatley). SouthwestSouthwestOne unique Ireland Ireland CGS, (ROI) (ROI) Bellewstown Quarry in County Meath [16], exposes an inlier of volcanicOneOne ofand of the the sedimentary most most western western rocks occurrences occurrences that existed of of volcanic asvolcanic a volcanic rocks rocks south island south of in theof the the Iapetus middle Iapetus suture of suture Iapetus is in is Fantaneinduring Fantane QuarryOrdovician Quarry (Figure (Figuretimes.7) in FossilCounty7) in Countyfaunas Tipperary showTippe [ 18 raryaffinities]. Here, [18]. volcanicwithHere, other volcanic ash island horizons ash faunas horizons are highly whilst are visibleyoungerhighly as visible paleshales greenas reveal pale bands greenthe island against bands had theagainst later dark movedthe grey dark Silurian closer grey togreywackes.Silurian the adjacent greywackes. The continents. strong The folding strong meansfolding they means are repeatedthey are aroundrepeated fold around hinges. fold However, hinges. asHowever, with many as workingwith many quarries, working it isquarries, not practical it is not to practical present the to present volcanic the geoheritage volcanic geoheritage to a wider to public. a wider In public. Fantane In Quarry, Fantane asQuarry, with other as with quarries, other quarries, it would it require would arequir specifice a specific investment investment by the quarryby the quarry operator oper- in publicator in relations public relations to embrace to embrace organised organised visits, such visits, as bysuch school as by groups, school whengroups, the when stories the couldstories be could told. be told.

FigureFigure 7. 7.Fantane Fantane Quarry, Quarry, County County Tipperary: Tipperary: pale pale green green volcanic volcanic ash ash bands bands in in Silurian Silurian greywackes. grey- wackes.

The audit of County Kerry, on the southwest coast, is yet to be completed but some of the potential CGS within the Silurian volcanic rocks of the Dingle Peninsula are given here and more fully addressed in Geological Field Guides such as Meere et al. [19]. The western end of the peninsula around Clogher Head reveals a sequence of Palae- ozoic sedimentary and volcanic rocks accumulated within the small Dingle Basin. Distinc- tive textures can be seen clearly in the dark green and red volcanic rocks, including sharp ‘glass-like’ shards, forming flattened ‘eutaxitic’ fabrics within fine-grained welded tuffs. These features tell a dramatic story of subaerial porphyritic lava and pyroclastic flows, with hot pumice and ash falling into the lava to become stretched out in their ‘plastic’ state. Later burial at depth compressed the deposit and preserved the pumice fragments as the glass-like shards, known as ‘fiamme’. In slightly younger rocks immediately to the south, similar but thin, pyroclastic flows in a pre-dominantly red-bed sequence contain volcanic bombs. Adjacent highlands that controlled seasonal flooding and the red-bed deposition are also thought to have been active volcanic centres producing the pyroclastic flows.

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The audit of County Kerry, on the southwest coast, is yet to be completed but some of the potential CGS within the Silurian volcanic rocks of the Dingle Peninsula are given here and more fully addressed in Geological Field Guides such as Meere et al. [19]. The western end of the peninsula around Clogher Head reveals a sequence of Palaeo- zoic sedimentary and volcanic rocks accumulated within the small Dingle Basin. Distinctive textures can be seen clearly in the dark green and red volcanic rocks, including sharp ‘glass- like’ shards, forming flattened ‘eutaxitic’ fabrics within fine-grained welded tuffs. These features tell a dramatic story of subaerial porphyritic lava and pyroclastic flows, with hot pumice and ash falling into the lava to become stretched out in their ‘plastic’ state. Later burial at depth compressed the deposit and preserved the pumice fragments as the glass-like shards, known as ‘fiamme’. In slightly younger rocks immediately to the south, similar but thin, pyroclastic flows in a pre-dominantly red-bed sequence contain volcanic bombs. Adjacent highlands that controlled seasonal flooding and the red-bed deposition are also thought to have been active volcanic centres producing the pyroclastic flows. Ferriter’s Cove exposes Silurian sandstones and siltstones rich in fossils and interbed- ded with thin layers of coarse-grained volcanic ash with sharp pale clasts. These are interpreted as pyroclastic flow and ash deposits from a nearby source, reworked in a shallow water environment. An overlying 5 m thick volcanic tuff forms a prominent ridge and indicates a more sustained episode of volcanism.

Southeast Ireland (ROI) The southeast of Ireland contains the largest extent of volcanic bedrock in Ireland, outside of the Palaeogene of Northern Ireland. The Duncannon Group, a belt of Ordovician felsic and basic volcanic lavas and tuffs, stretches from the east coast in County Wicklow through County Wexford to the south coast in County Waterford. These rocks are products of the volcanic arc that formed on the southern margin of the Iapetus ocean. On the south coast in County Waterford the Copper Coast UNESCO Global Geopark (see Section4) contains numerous CGS that cater to a wide range of geological interests, including Ordovician palaeontology, Quaternary features, coastal geomorphology and significant mining heritage. However, the underlying basis for the Geopark is essentially the Ordovician volcanic succession [20]. Two examples of specific interest that relate to the volcanic geoheritage theme are the Pipes of Baidhb (Figure8) and Dunhill Quarry (Figure9)[ 21]. The former is an intrusion of rhyolite, seen in the cliffs of Knockmahon and Stage Cove, and accessible to anyone walking along the shoreline. The rhyolite displays columnar jointing, reminiscent of the Giant’s Causeway. The intrusion was named by Des Cowman, a local leading light in the inception and development of the Geopark, as part of a deliberate strategy to promote the Geopark’s assets through its folklore. The ‘Baidhb’ was a ghostly woman, wandering the local roads and screeching an omen of death that echoed from the organ pipes in the cliff. Dunhill Quarry would be an especially interesting site for public presentation, if the necessary permission and access arrangements could be negotiated. Although presently partly overgrown with vegetation, the face of this quarry displays at least five individual tuff units in a face that looks like it was sawn with a cheese wire. The top of each unit comprises laminated fine-grained tuff with the remainder composed of coarser grained lapilli tuff. The quarry faces display larger blocks of volcanic material that fell directly to the ancient sea floor, indenting the surfaces of the tuff layers. Some units have pumice fragments that were deposited on the top of the layer before eventually sinking after becoming waterlogged. Some good interpretation on site could make this a very visual, safe and easily understood access point to the geological story of Ordovician volcanoes on the Copper Coast. Geosciences 2021, 11, 52 10 of 22 Geosciences 2021, 11, x FOR PEER REVIEW 11 of 23

Geosciences 2021, 11, x FOR PEER REVIEW 11 of 23

FigureFigure 8. 8.Pipes Pipes of of Baidhb, Baidhb, County County Waterford: Waterford: polygonal polygonal columns columns in in rhyolite rhyolite intrusion. intrusion. Figure 8. Pipes of Baidhb, County Waterford: polygonal columns in rhyolite intrusion.

Figure 9. Dunhill Quarry, County Waterford: Ordovician volcanic bedded tuffs. FigureFigure 9. 9.Dunhill Dunhill Quarry, Quarry, County County Waterford: Waterford: Ordovician Ordovician volcanic volcanic bedded bedded tuffs. tuffs. Volcanic rocks contain some of the world’s most important mineral deposits and are particularlyInVolcanic County associated rocks Wexford, contain with the somecopper large of workingand the world’sgold. quarry The most Ordovician at important Coolishall volcanic mineral [22] excavatesrocks deposits of the aand Avoca large are rhyolitedistrictparticularly body,(Figure associated representative 10) in County with ofcopper Wicklow many and such [23]gold. volcanic hosted The Ordovician bodiesa large thatmassive volcanic comprise sulphide rocks the Duncannonof deposit the Avoca and GroupIreland’sdistrict volcanics (Figure most important 10) of SE in Ireland.County copper TheseWicklow mine. resistant Historical[23] hosted volcanic (18th a large bodies and massive 19th form century) the sulphide core mining of deposit numerous in adits and smallandIreland’s shafts hills most that was stretch importantoverprinted from copper Countyby 20th mine. Wicklowcentury Historical underground to New (18th Ross and and in 19th southwest open century) pit mining. County mining The Wexford. in mines adits Whilstfinallyand shaftsthere closed was are in overprinted many1982. Large other by open concerns 20th pit century mining for an underground has operator left a significant to addressand open geoheritage in pit the mining. simple legacy, The process mines with ofexcellentfinally operating closed exposures a in quarry, 1982. of Large itboth would openmineralisation be pit highly mining beneficialand has theleft volcanica ifsignificant some host level geoheritage rocks, of controlled as well legacy, as public iconic with accessCornishexcellent were engine exposures made houses. possible, of both especially mineralisation for educational and the volcanic groups. Nothost onlyrocks, would as well this as enable iconic schoolCornish children engine to houses. learn a little about the ancient volcanic history of County Wexford, but it would also teach them about the importance of quarrying to maintaining the lifestyles we currently enjoy in our societies. Volcanic rocks contain some of the world’s most important mineral deposits and are particularly associated with copper and gold. The Ordovician volcanic rocks of the Avoca district (Figure 10) in County Wicklow [23] hosted a large massive sulphide deposit and Ireland’s most important copper mine. Historical (18th and 19th century) mining in adits

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and shafts was overprinted by 20th century underground and open pit mining. The mines finally closed in 1982. Large open pit mining has left a significant geoheritage legacy, with Geosciences 2021, 11, x FOR PEER REVIEWexcellent exposures of both mineralisation and the volcanic host rocks, as well as iconic12 of 23

Cornish engine houses.

FigureFigure 10. 10.Avoca, Avoca, County County Wicklow: Wicklow: copper copper mineralisation mineralisation hosted hosted in in Ordovician Ordovician volcanic volcanic tuffs. tuffs.

However,However, AvocaAvoca exemplifies exemplifies some some of of the the difficulties difficulties of of promoting promoting geological geological and and miningmining heritage heritage in in competition competition with with other other viewpoints. viewpoints. Although Although Avoca’s Avoca’s mining mining and, and, by by extension,extension, volcanic volcanic geological geological heritage heritage has has been been the the focus focus of of multiple multiple community community driven driven projectsprojects to to conserve conserve and and promote promote it, it, with with a a view view to to becoming becoming a a National National Mining Mining Heritage Heritage Centre,Centre, the the site site is is in in state state ownership. ownership. The The state state body body responsible responsible for for management management of of the the sitesite has has largely largely focused focused on on safety safety issues issues and and on on addressing addressing the the significant significant environmental environmental contaminationcontamination causedcaused byby discharge discharge of of acid acid mine mine drainage drainage from from the the site. site. There There has has been been littlelittle room room for for public public promotion promotion of of mining mining heritage heritage in in recent recent years. years.

3.2.3.2. The The Carboniferous: Carboniferous: Tropical Tropical Seas Seas and and Underwater Underwater Volcanoes Volcanoes CroghanCroghan Hill Hill (Figure (Figure 11) 11) is the is remainsthe remains of an extinctof an volcanoextinct volcano that erupted that anderupted emerged and fromemerged the sea from that the covered sea that County covered Offaly County [24] andOffaly much [24] ofand the much rest of of Ireland the rest during of Ireland the Carboniferousduring the Carboniferous Period. A variety Period. of volcanicA variety rocks of volcanic occur on rocks and aroundoccur on Croghan and around Hill, includingCroghan alkaliHill, including basalts, limburgites, alkali basalts, pyroclastic limburgites, agglomerates pyroclastic and agglomerates tuffs. The rocksand tuffs. are interbeddedThe rocks are with interbedded the limestones with the that limestones formed in that the formed warm seas in the into warm which seas the into volcano which erupted.the volcano These erupted. rocks record These episodesrocks record of lava episod flowses of and lava violent flows explosive and violent eruptions. explosive On erup- the northeasterntions. On the side northeastern of Croghan side Hill, of Croghan some columnar Hill, some jointing columnar in basalt, jointing formed in basalt, by a similar formed processby a similar to that process in the to Giant’s that in Causeway,the Giant’s suggestsCauseway, ponding suggests and ponding cooling and of thecooling lava of in the a subaeriallava in a environment.subaerial environment. Gneiss xenoliths Gneiss have xenolit beenhs describedhave been [ 25described,26] in agglomerate [25,26] in agglom- to the westerate of to Croghan the west village of Croghan and in basaltsvillage southand in of ba thesalts village. south It of has the been village. suggested It has thatbeen these sug- high-gradegested that metamorphic these high-grade gneisses metamorphic are derived gn fromeisses the are sub-Palaeozoic derived from lowerthe sub-Palaeozoic crust in this region. There is a great scope for making more of the old volcano story at Croghan Hill and lower crust in this region. There is a great scope for making more of the old volcano story this should be made easier by the fact that the official tourism Discover Ireland website at Croghan Hill and this should be made easier by the fact that the official tourism Dis- refers to it in one of its headlines as an old volcano. cover Ireland website refers to it in one of its headlines as an old volcano.

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FigureFigure 11. 11.Croghan Croghan Hill, Hill, County County Offaly: Offaly: Agglomerate Agglomerate rock rock forms forms the the Clustaka Clustaka standing standing stone. stone.

CountyCounty Limerick Limerick contains contains the the most most extensive extensive development development of of Carboniferous Carboniferous volcanic volcanic rocksrocks in in Ireland, Ireland, part part of of the the Limerick Limerick syncline. syncline. Extensive Extensive ash ash deposits deposits or or tuffs, tuffs, of of basaltic basaltic origin,origin, are are interbedded interbedded withwith limestonelimestone and are in places fossiliferous, evidence evidence of of deposi- depo- sitiontion in in a a shallow shallow tropical tropical sea. sea. Basalt Basalt lava lava flows flows are are also also present present and and in inone one quarry quarry at Ca- at Caherconlishherconlish a atrachyte trachyte body body displays displays spectacular spectacular columnar jointing.jointing. TheThe GSIGSI PublicPublic Data Data ViewerViewer for for unaudited unaudited sites sites [ 27[27]] shows shows 11 11 provisional provisional CGS CGS of of volcanic volcanic interest, interest, some some of of whichwhich have have great great potential potential as as volcanic volcanic geoheritage geoheritage sites. sites. The The area area is is the the subject subject of of several several classicclassic geological geological descriptions, descriptions, including including Lamplugh Lamplugh et et al. al. [ 28[28]] and and Geike Geike [ 29[29],], but but has has yet yet toto be be surveyed surveyed in in modern modern times times as as part part of of a a CGS CGS audit. audit. Thus, Thus, information information on on the the current current statusstatus of of the the sites sites is is lacking. lacking.

3.3.3.3. The The North North Atlantic: Atlantic: Basalt Basalt Lavas, Lavas, Columnar Columnar Jointing, Jointing, Dolerite Dolerite Dykes Dykes and and Cone Cone Sheets Sheets TheThe North North Atlantic Atlantic began began opening opening around around 200 200 million million years years ago ago and and the the ensuing ensuing pe- pe- riodriod of of crustal crustal rifting rifting eventually eventually led, led, 65 65 million million years years ago, ago, to to the the creation creation of of the the Palaeogene Palaeogene NorthNorth Atlantic Atlantic Igneous Igneous Province. Province. Then, Then, large large volumes volumes of of magma magma were were intruded intruded into into the the crustcrust or or erupted erupted through through fissures. fissures. Traces Traces of Palaeogene of Palaeogene volcanism volcanism can be can found be found as far southas far assouth Dingle as Dingle in County in County Kerry but Kerry the but most the important most important examples examples are in the are northern in the northern part of thepart island.of the island. The Giant’s The Giant’s Causeway Causeway is the most is the spectacular most spectacular example example of thick of basalt thick lava basalt flows lava that covered much of the northern part of the island. The lava flowed upwards through flows that covered much of the northern part of the island. The lava flowed upwards fissures, now preserved as a series of dolerite dykes that extend westwards into today’s through fissures, now preserved as a series of dolerite dykes that extend westwards into Atlantic. Large volumes of magma solidified underground to form granites and gabbros. today’s Atlantic. Large volumes of magma solidified underground to form granites and 3.3.1.gabbros. The Giant’s Causeway, Geoheritage Interpretation and Visitor Experience With just under 1 million visitors in 2019 [30], the Giant’s Causeway World Heritage 3.3.1. The Giant’s Causeway, Geoheritage Interpretation and Visitor Experience Site (WHS) in north County Antrim (Figure 12) is one of the most popular tourist destina- tions inWith Northern just under Ireland 1 million and one visitors of the bestin 2019 sites [30], anywhere the Giant’s for viewing Causeway volcanic World geological Heritage heritage.Site (WHS) The in columnar north County jointing Antrim in the (Figure basalt 12) flows is one is probably of the most its best-known popular tourist feature destina- but thetions entire in Northern site contains Ireland numerous and one volcanic of the best features sites ofanywhere interest. for Two viewing thick basalt volcanic lava geolog- flows areical exposed heritage. in The the cliffscolumnar above jointing the shore in the and basalt between flows them is probably is the Interbasaltic its best-known Formation, feature abut red the clay entire (laterite) site contains formed bynumerous tropical volcanic weathering features of the of top interest. of the Two first lavathick flow. basalt With lava 40,000flows basaltare exposed columns, in the the cliffs distinctive above structuresthe shore and are likenedbetween to them classical is the architecture, Interbasaltic with For- themation, most accessiblea red clay colonnade/entablature(laterite) formed by tropical junction weathering known asof ‘Thethe top Organ’. of the The first polygonal lava flow. columnsWith 40,000 have basalt resulted columns, from the the ponding distinctive of thickstructures individual are likened lava flows to classical in river architecture, valleys cut intowith the the Lower most Basaltaccessible landscape. colonnade/entablature junction known as ‘The Organ’. The po- lygonal columns have resulted from the ponding of thick individual lava flows in river valleys cut into the Lower Basalt landscape.

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FigureFigure 12. 12.Giant’s Giant’s Causeway, Causeway, County County Antrim: Antrim: hexagonal hexagona jointingl jointing in in Palaeogene Palaeogene basalt basalt lavas lavas (Photo: S.(Photo: Gatley). S. Gatley).

SeveralSeveral authorsauthors [[31,32]31,32] have have documented documented th thee spectacular spectacular features features and and geological geological sig- significancenificance of of the the Giant’s Giant’s Causeway, Causeway, and and the challenges ofof implementingimplementing aa management management plan,plan, as as required required by by WHS WHS reporting reporting [ 33[33],], for for this this complex complex geosite. geosite. It It is is also also a a dynamic dynamic site, site, subjectsubject to to ongoing ongoing coastal coastal erosion erosion and and slope slope failures, failures, which which resulted resulted in in the the closure closure of of the the lowerlower coastal coastal pathpath inin thethe mid-1990’smid-1990’s [34,35]. [34,35]. A A 2010 2010 study study [34], [34], establishing establishing a adatabase database of ofbaseline baseline slope slope instability instability and and future future recording recording mechanisms, mechanisms, has has provided provided a tool a tool for sus- for sustainabletainable management management in in response response to to the the effects effects of of climate climate change, asas wellwell asas proposing proposing innovativeinnovative choices choices for for virtual virtual tourism tourism experiences. experiences. TheThe WHS WHS is is promoted promoted through through a a state-of-the-art state-of-the-art visitor visitor centre, centre, opened opened in in 2012. 2012.His- His- torically,torically, interpretation interpretation and and the the tourism tourism experience experience focused focused on on the the aesthetics aesthetics of of the the basalt basalt columns,columns, wovenwoven inin with with tales tales of of Irish Irish mythology, mythology, which which overshadowed overshadowed its its geoscientific geoscientific significance.significance. Folklore Folklore legend legend of of the the Giant Giant Finn Finn McCool McCool (Fionn (Fionn mac mac Cumhaill) Cumhaill) invokes invokes the the basaltbasalt polygons polygons as as his his stepping-stones stepping-stones between between Ireland Ireland and and Scotland Scotland and and likens likens a range a range of volcanicof volcanic features features to possessions, to possessions, such such as ‘The as ‘The Giant’s Giant’s Boot’. Boot’. InIn response response to to this this imbalance, imbalance, a a 2007 2007 survey survey [ 36[36]] to to assess assess visitor visitor appreciation appreciation of of the the site’ssite’s geoheritage geoheritage value value and and on-site on-site interpretation interpretation showed showed a arelatively relativelylimited limited understand-understand- inging of of its its abiotic abiotic nature nature (as (as opposed opposed to to its its biodiversity). biodiversity). The The recognised recognised need need for for improved improved geoheritagegeoheritage interpretiveinterpretive panelspanels andand interaction interaction throughthrough guided guided walks walks were were some some of of the the conclusionsconclusions that that also also had had relevance relevance for for other other (particularly (particularly coastal) coastal) geotourism geotourism sites. sites. While While therethere is is a a valid valid place place for for folklore folklore ‘enhancement’ ‘enhancement’ at at geosites, geosites, there there is is still still a a need need to to fully fully redressredress the the balance balance at at the the Giant’s Giant’s Causeway Causeway and and toto promotepromote thethe dramaticdramatic geologicalgeological story.story. GuidedGuided walks walks are are now now available, available, although although individual individual ranger ranger guiding guiding and and interpretation interpretation maymay be be variable variable in in its its myth–science myth–science balance. balance. TheThe WHSWHS managementmanagement plan has has also also required required a abalance balance between between promotion promotion and and ge- geoeducation,oeducation, and and geoconservation: geoconservation: a dilemma a dilemma that that is not is notto date todate necessitated necessitated by the by lesser the lesserknown, known, older, older, volcanic volcanic sites in sites Ireland in Ireland (see Se (seection Section 4.1.). The 4.1). wider The widersubject subject of how of to how con- tovey convey the geoheritage the geoheritage message message in public-friendly in public-friendly language, language, rather than rather technical, than technical, and how andto produce how to producehighly engaging highly engaging interpretative interpretative panels through panels throughoptimal optimalcontent contentand location, and location, has been discussed recently by several authors, for example, by Bruno and Wallace has been discussed recently by several authors, for example, by Bruno and Wallace and and Brilha [37,38]. A summary of existing and proposed interpretative and promotional Brilha [37,38]. A summary of existing and proposed interpretative and promotional meth- methods for Ireland’s main volcanic sites are given in Table1. ods for Ireland’s main volcanic sites are given in Table 1.

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Table 1. Selection of the main volcanic sites in Ireland with suggested interpretation and promotion.

CGS/Geosite County Age Primary Heritage Value Secondary Heritage Value General Setting Accessibility Existing Promotion * Suggested Promotion * (See Figure 1 for Locations) 1 Ardgillan Dublin Ord Volcanic Public Park Very Good 5,9 1,5 1,2,3,4,6,8, 2 Avoca Wicklow Ord Mining Volcanic State owned Poor, safety issues 5,9 (10) 3 Bellewstown Meath Ord Fossils Q active By request; supportive 5,9 1,7,8,(10) Palaeo 5 Blind Rock Donegal Coastal geomorp Igneous Coastal Good 5,9 1,2 -gene 7 Bruse Hill Cavan Ord Strat/Vol Q disused Private 6,9 6,(10) 8 Caherconlish Limerick Carb Q 5 1,6,9 9 Camaderry Wicklow Caled Igneous National Park, Hill Walking route 5,9 3,5,6, 10 Carrickatee Monaghan Ord Strat/Vol Hill Crags, fields Private 9 6,(10) 11 Coolishall Wexford Ord Strat/Vol Q active By request 5,9 6,(10) 12 Croghan Hill Offaly Carb Volcanic Carb Hill Good 5,9 1,6, 13 Dingle Kerry Silur Coastal Good 5,6 1,2,4,5,6,9 15 Dunhill Waterford Ord Strat/Vol Q disused Private 5,9 5,6,(10) 17 Fantane Tipperary Silur Strat Q active By request 9 5,6,(10) 18 Finny Mayo Ord Fossils Strat/Vol Roadside Very Good 4,5,6,9 1,3,5,6 Palaeo 19 Giant’s C Antrim Volcanic Biodivers Coastal Good 2,3,4,5,6 1,2, -gene 20 Gorumna Galway Ord Strat/Vol Igneous Coastal Good 5,9 1,5,6 21 Greystones Wicklow Caled Igneous Coastal Good 5,9 1,5,6,(10) Palaeo 22 Inishcrone Sligo Igneous Quatern Coastal Good 5,9 1,5,6 -gene Very 23 Kilkenny BP Donegal Caled Igneous Thick gorse 5,9 3,5,6,(10) Poor 24 Killary H Galway Ord Strat/volc Roadside Good 5,9 1,5,6, (10) 26 Lambay N Dublin Ord Fossils Volcanics Private island Restricted, by boat 5,9 5,6,(10) 28 P Baidhb Waterford Ord Strat/volc Coastal Safety issues 1,5,9 5,6 Karst, 1,2,4,5,6 30 Portrane N Dublin Ord Volcanic, Fossils, Coastal Very Good 5,9 Quatern Palaeo 31 Rampark Louth Volcanic Private roadside Not known 5,9 5,6 -gene Palaeo 32 Slievenaglogh Louth Volcanic Mountain grazing Good 5,9 1,5,6 -gene * Key: 1. Info panel; 2. Thematic/Trail; 3. Visitor/Info centre; 4. Guided walk; 5. Literature; 6. Website/app; 7. Converted Quarry; 8. Viewing platform; 9. CGS audit report; (10. science specialist/student interest). Geosciences 2021, 11, 52 15 of 22

There are numerous other sites along the north Antrim coast where Palaeogene Geosciences 2021, 11, x FOR PEER REVIEWvolcanic heritage can be seen. Examples include the North Star Dyke at Ballycastle,16 of a23 probable feeder dyke for the basalt lavas, and two dolerite sills emplaced horizontally into Carboniferous strata to form the promontory at Fair Head. However, while the fame of the Giant’s Causeway can be seen as reflecting the popularityrelevant geoheritage of volcanic stories. geoheritage, The Interbasalti it can alsoc Formation have the red effect beds of were overshadowing extensively other,mined equallyfor iron relevant and aluminium, geoheritage especially stories. Theduring Interbasaltic World War Formation 1, leaving red a rich beds mining were extensively heritage in minedthe Glens for ironof Antrim. and aluminium, The direct connection especially duringof a cultural World and War economic 1, leaving heritage a rich to mining the es- heritagesential geology in the Glens underfoot of Antrim. should The be direct easy connectionto promote of but, a cultural in contrast and to economic the international heritage toattention the essential focused geology on the underfootCauseway should (for exam beple, easy the to hobby promote website but, in‘Volcano contrast Hotspot’ to the international[39]), there has attention been only focused very onlimited the Causeway local interest (for in example, the history the hobbyand physical website heritage ‘Volcano of Hotspot’the mining [39 industry]), there hasin the been Glens only of very Antrim. limited local interest in the history and physical heritage of the mining industry in the Glens of Antrim. 3.3.2. Palaeogene in Counties Louth, Donegal and Sligo 3.3.2.Further Palaeogene south, in CountiesCounty Louth Louth, has Donegal a multit andude Sligo of Palaeogene igneous CGS, largely withinFurther the Cooley south, Peninsula County Louth around has Carlingfor a multituded. The of Palaeogene rocks in these igneous sites CGS, are part largely of a withinwider thedevelopment Cooley Peninsula of intrusive around and Carlingford. extrusive Theigneous rocks rocks in these that sites includes are part the of aMourne wider developmentMountains Granite of intrusive and Slieve and extrusive Gullion igneousRing Dyke rocks complex that includes in County the Mourne Down in Mountains Northern GraniteIreland. and Some Slieve years Gullion ago, Ringlocal Dykebodies complex in both in jurisdictions County Down together in Northern commenced Ireland. a Somecross- yearsborder ago, Geopark local bodies project in but both after jurisdictions County Lo togetheruth’s withdrawal, commenced the a cross-borderGeopark endeavour Geopark is projectcurrently but afterrestricted County to Louth’sNorthern withdrawal, Ireland and the has Geopark gone endeavourforward as is an currently application restricted from towithin Northern the UK. Ireland and has gone forward as an application from within the UK. However,However, there there is stillis still much much potential potential for telling for telling volcanic volcanic geoheritage geoheritage stories in stories County in Louth.County Most Louth. of the Most relevant of the volcanic relevant or volcanic sub-volcanic or sub-volcanic sites are of gabbrosites are or of granite gabbro intrusions, or granite doleriteintrusions, dykes dolerite and cone dykes sheets, and butcone there sheets, are bu alsot there exposures are also of volcanicexposures agglomerates of volcanic ag- at Slievenagloghglomerates at CGSSlievenaglogh (Figure 13 )CGS and (Figure hawaiite 13) lavas and athawaiite Rampark lavas CGS at [Rampark40]. An excellent CGS [40]. field An guideexcellent for geologistsfield guide has for been geologists published has bybeen Baxter published [41], but by there Baxter is great[41], scopebut there for ais more great integratedscope for heritagea more integrated trail for ordinary heritage hillwalkers trail for ordinary or cyclists hillwalkers as well as motorists. or cyclists The as visiblewell as geologymotorists. identified The visible in the geology CGS could identified be presented in the inCGS a simple could but be meaningfulpresented in way a simple for those but untrainedmeaningful in geology,way for those but curious untrained about in thegeolog naturaly, but landscape. curious about the natural landscape.

FigureFigure 13. 13.Slievenaglogh, Slievenaglogh, County County Louth: Louth: vent vent agglomerate agglomerate with with irregular, irregula unsortedr, unsorted clasts clasts in finein fine ma- matrix. trix.

CountyCounty DonegalDonegal hashas somesome ofof the the most most complex complex geology geology in in Ireland, Ireland, dominated dominated by by PrecambrianPrecambrian Dalradian Dalradian metasediments metasediments and and Caledonian Caledonian granite granite bodies bodies that werethat emplacedwere em- alongplaced major along crustal major faults.crustal Purelyfaults. Purely volcanic volcanic features features are relatively are relatively few but few new but airborne new air- geophysicalborne geophysical mapping mapping by Tellus by [ 42Tellus] shows [42] that shows the northwest–southeast-trendingthat the northwest–southeast-trending Palaeo- Palaeogene dolerite dyke swarms that are a prominent feature of the Antrim basalt plat- eau extend across Donegal and into the Atlantic seabed. A notable example is the Blind Rock sub-vertical dolerite dyke on Doorin Point peninsula [43]. It is interpreted as a com- posite feeder dyke that supplied now eroded, formerly overlying volcanic rocks, in sev- eral pulses of intrusion during the opening of the North Atlantic Ocean. Fittingly, the main exposure of the dyke extends into the Atlantic Ocean in Donegal Bay. Blind Rock is easily

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gene dolerite dyke swarms that are a prominent feature of the Antrim basalt plateau extend across Donegal and into the Atlantic seabed. A notable example is the Blind Rock sub-vertical dolerite dyke on Doorin Point peninsula [43]. It is interpreted as a composite Geosciences 2021, 11, x FOR PEER REVIEW 17 of 23 feeder dyke that supplied now eroded, formerly overlying volcanic rocks, in several pulses of intrusion during the opening of the North Atlantic Ocean. Fittingly, the main exposure of the dyke extends into the Atlantic Ocean in Donegal Bay. Blind Rock is easily accessible andaccessible is the best and exposure is the best in Irelandexposure of in this Ireland type of of composite this type dyke.of composite The audit dyke. recommends The audit itsrecommends wider promotion its wider through promotion a visitor thro informationugh a visitor panel. information panel. EquallyEqually impressive impressive are are the the very very fine fine exposures exposures of Palaeogene of Palaeogene dykes dykes at the at eastern the eastern side ofside Inishcrone of Inishcrone beach beach in County in County Sligo Sligo (Figure (Figure 14)[7 14)]. They [7]. They feature feature in a publicin a public guide guide to the to geologicalthe geological heritage heritage of the ofcounty the county [44], [44], which wh wasich was the firstthe first guide guide derived derived from from an original an orig- CGSinal audit.CGS audit. The site The has site its has own its chapter own chapte heading,r heading, ‘Molten ‘Molten magma magma rises through rises through the Rocks’, the givingRocks’, context giving to context the dykes. to the The dykes. dykes The are dykes numerous are numerous on the foreshore, on the immediatelyforeshore, immedi- below aately popular below promenade a popular and promenade traditional and seaweed traditio baths.nal seaweed Their form baths. varies Their considerably form varies with con- positivesiderably and with negative positive relief and comparednegative relief to the compared Carboniferous to the Carboniferous Limestone host Limestone rock. There host arerock. quite There variable are quite degrees variable of baking degrees ofthe of baking host rock of andthe host chilling rock of and the chilling dyke margins of the dyke and attractivemargins and colour attractive contrasts, colour such contrasts, that a natural such curiositythat a natural as to theircuriosity form as and to their origins form ought and toorigins be expected. ought to There be expected. is certainly There scope is certainl for morey scope effort for to promote more effort them to aspromote an interesting them as featurean interesting of the town feature for of visitors. the town for visitors.

FigureFigure 14. 14.Inishcrone, Inishcrone, County County Sligo: Sligo: Palaeogene Palaeogene dyke dyke in in Carboniferous Carboniferous Limestone. Limestone.

4.4. UNESCOUNESCO Global Global Geoparks Geoparks in in Ireland Ireland ThereThere areare currentlycurrently threethree UNESCO UNESCO GlobalGlobal GeoparksGeoparks inin Ireland, Ireland, thethe Marble Marble Arch Arch Caves,Caves, the the Burren Burren and and Cliffs Cliffs of of Moher Moher and and the the Copper Copper Coast. Coast. The The Marble Marble Arch Arch Caves Caves in in CountyCounty Fermanagh Fermanagh [45 [45]] formed formed the the focus focus of theof firstthe first cross-border cross-border UNESCO UNESCO Global Global Geopark Ge- (betweenopark (between County County Fermanagh Fermanagh in Northern in Northern Ireland Ireland and County and County Cavan Cavan in the in Republic the Repub- of Ireland).lic of Ireland). The Copper The Copper Coast UNESCO Coast UNESCO Global GeoparkGlobal Geopark [46] is a community[46] is a community driven venture, driven designatedventure, designated in 2001, and in focused2001, and on anfocused historic on copper an historic mining copper area ofmining County area Waterford of County in SEWaterford Ireland. in SE Ireland. ThereThere are are aspiring aspiring Geoparks Geoparks in in other other areas, areas, but but the the Joyce Joyce Country Country and and Western Western Lakes Lakes geoparkgeopark projectproject [47[47]] isis the the most most likely likely to to meet meet the the stringent stringent requirements requirements for for UNESCO UNESCO approval.approval. AlthoughAlthough therethere are are some some Ordovician Ordovician volcanic volcanic elements elements in in the the district, district, they they are are only one aspect of the multiple geodiversity interests here. Another cross-border project that sought UNESCO Global Geopark status for the Mourne Mountains and Ring of Gul- lion in Northern Ireland, and the Cooley Peninsula in Ireland was unsuccessful. More re- cently, Mourne Gullion Strangford Aspiring UNESCO Global Geopark [48] has applied for this status, based on the igneous geology and volcanic geoheritage of the Northern Ireland part of the story. The Antrim geopark project in Northern Ireland is focused on

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only one aspect of the multiple geodiversity interests here. Another cross-border project that sought UNESCO Global Geopark status for the Mourne Mountains and Ring of Gullion in Northern Ireland, and the Cooley Peninsula in Ireland was unsuccessful. More recently, Mourne Gullion Strangford Aspiring UNESCO Global Geopark [48] has applied for this status, based on the igneous geology and volcanic geoheritage of the Northern Ireland part of the story. The Antrim geopark project in Northern Ireland is focused on the Palaeogene volcanics and older rocks of the spectacular Causeway Coast AONB and Antrim Coast and Glens AONB (Areas of Outstanding Natural Beauty) [49]. The Copper Coast UNESCO Global Geopark, based on Ordovician volcanic geology and associated copper deposits, clearly has the most scope for presenting volcanic geoher- itage stories to the wider public. Two examples of specific interest were described above, but there are many more potentially available, especially with the facility of the visitor centre in Bunmahon and a dedicated geologist working on public activities. In the Marble Arch Cave UNESCO Global Geopark, the geological emphasis is on Carboniferous rocks and the upland bogs and karst developed on them. Volcanic rocks do not play any significant part, other than a Palaeogene dyke that crosses Cuilcagh Mountain and plays an influential role in the development of the numerous cave systems, acting as a divide to drainage systems. Whilst this is well known to cavers and influences their systematic approach to cave exploration and dye tracing of water, the dyke is a minor story within the scope of the Geopark and the geological stories they communicate to the many visitors.

4.1. National and UNESCO Global Geoparks Examples of how to promote palaeovolcanics in geotourism, where storytelling is difficult to relate to a volcanic morphology that has been largely eroded, have been given in several papers on European national and UNESCO Global Geoparks [50,51]. These include the extensive Permian lavas and ignimbrites of national Geopark Porphyrland in Germany [50], where the vast majority of geosites address volcanism as the main theme, which is also promoted through its volcanic stone industry heritage, thematic trails, publicly accessible disused quarries and guided tours. Bohemian Paradise UNESCO Global Geopark (northern Czechia) [50] explores its volcanic mineralogy theme with a museum dedicated to mineralogy. Younger volcanic rocks are easier to promote, with their easier to understand geomor- phology. The abandoned Hegyest˝uquarry in Bakony–Balaton UNESCO Global Geopark in western Hungary [51] shows a nearly 30 m-high wall of columnar jointing in basalt. The Geopark also plans to incorporate a 260 m tunnel carved into Mio-Pliocene volcanic rock at Kopasz Hill, into its Visitor Centre. Columnar jointing is also the focus of some very impor- tant geotourism sites around the world, on a par with the Giant’s Causeway, such as the Hong Kong UNESCO Global Geopark, where geotourism, geoconservation, geoeducation and recreation has been successfully integrated in this volcanic setting (e.g., [52,53]).

4.2. Drifting Apart Project Between 2015 and 2018, Ireland, principally through the Causeway, Coast and Glens Heritage Trust and Marble Arch Caves UNESCO Global Geopark, was involved in a Northern Peripheries and Arctic Area Programme ERDF-funded project called ‘Drifting Apart’ [54] in which numerous UNESCO Global Geoparks and aspiring geoparks on the Atlantic seaboard promoted their shared geoheritage. Much of this related to Palaeogene volcanism, and resources created in the project remain available on the project website for future use.

5. General Issues with Promoting Igneous Geoheritage to the Public The sites we have described above have been restricted to those showing volcanic rocks sensu stricto and are mostly found under the Geological Heritage Programme’s Geosciences 2021, 11, 52 18 of 22

IGH11 Igneous, IGH4 Cambrian-Silurian, IGH8 Lower Carboniferous and IGH10 Devonian Geosciences 2021, 11, x FOR PEER REVIEW 19 of 23 themes, although many CGS having an interest across two or more themes. However, there are blurred boundaries in geological definitions and in terms of public perception, and there are many sites of a broad igneous nature that can help in demonstratingstrating fundamental fundamental principles principles of geological of geological processes, processes, such as magmatism such as magmatism and chronos- and chronostratigraphictratigraphic timelines, timelines, to the general to the generalpublic. public.This blurring This blurring can be seen can bewith seen the with strictly- the strictly-speakingspeaking intrusive intrusive feeder feederdykes dykes(e.g., North (e.g., North Star Dyke Star Dykeand Blind and Blind Rock) Rock) associated associated with withthe extrusive the extrusive Palaeogene Palaeogene lavas. lavas. ThereThere areare somesome sitessites ofof brecciabreccia pipes,pipes, appinitesappinites andand explosionexplosion brecciasbreccias that, that, although although notnot strictlystrictly volcanicvolcanic inin origin,origin, dodo demonstratedemonstrate ‘volcanic-type’‘volcanic-type’ mechanismsmechanisms ofof upwardupward pipe-likepipe-like explosiveexplosive gas gas and and magma magma intrusions. intrusions. BrecciaBreccia pipespipes areare associatedassociated withwith aa suitesuite ofof Caledonian Caledonian Appinites Appinitesthat that was was intruded intruded immediatelyimmediately beforebefore the earliest earliest Donegal Donegal granite granite plutons. plutons. They They were were formed formed through through ex- explosiveplosive pressure pressure from from upward-streaming upward-streaming gas-rich gas-rich magma, causing fragmentationfragmentation ofof thethe countrycountry rock. rock. However,However, most most Donegal Donegal sites, sites, such such asas KilkennyKilkenny BrecciaBreccia PipePipe (Figure(Figure 15 15))[ [43],43], areare largelylargely inaccessibleinaccessible (remote, (remote, rough rough ground ground and/or and/or privateprivate farmland)farmland) andand mostmost likelylikely onlyonly ofof studentstudent andand specialistspecialist interest.interest.

FigureFigure 15.15.Kilkenny Kilkenny BrecciaBreccia Pipe,Pipe, CountyCounty Donegal:Donegal: inaccessibleinaccessible sitesite inin thickthick gorse.gorse.

TwoTwo County County Wicklow Wicklow sites sites [ 23[23]] with with good good public public access access contain contain Caledonian Caledonian appinite appinite intrusions.intrusions. WhilstWhilst geologicalgeological researchersresearchers areare stillstill workingworking toto fullyfully understandunderstand thesethese pipe-pipe- likelike intrusionsintrusions of of hornblende hornblende rich rich basic basic magmas, magmas, the the simple simple story story can can be be told told that that they they are are coevalcoeval basic basic magmas magmas differentiated differentiated from from the the batholiths batholiths of Leinsterof Leinster Granite Granite which which dominate domi- thisnate county. this county. Whilst Whilst signboards signboards are too are intrusive too intrusive a medium a medium for the for Camaderry the Camaderry Appinite Appin- in itsite remote in its remote hillside hillside setting setting overlooking overlooking Glendalough, Glendalough, there there are other are other media media that that could could be usedbe used (such (such as geotourism-walking as geotourism-walking apps), apps), and especiallyand especially by the by hillwalking the hillwalking community community who wouldwho would be the be ones the passingones passing through through exposures exposures on popular on popular walking walking routes. routes. The Greystones The Grey- Appinitesstones Appinites are along are the along seafront the seafront and could and becould explained be explained with a with signboard a signboard to enhance to en- interesthance interest for a variety for a variety of visitors. of visitors. InIn south south County County Dublin Dublin (Dun (Dun Laoghaire-Rathdown) Laoghaire-Rathdown) the Blackrock the Blackrock Breccia (BrecciaFigure 16(Figure) [55], which16) [55], occupies which aoccupies distinctive a distinctive small area small (approximately area (approximately 30 m by 13 m)30 m in theby 13 intertidal m) in the zone in- attertidal Blackrock zone village, at Blackrock is an explosion village, isbreccia, an explosion composed breccia, of angular composed fragments of angular of granite fragments set inof agranite matrix ofset finely in a matrix broken of granite. finely Nobroken junction granite. or boundary No junction with or another boundary rock with type another is seen. Therock rock type is is interpreted seen. The rock to have is interpreted formed in to the have later formed stages in of the the later intrusion stages of the intrusion Leinster of the Leinster Granite when an upsurge of an explosive gas phase fragmented granite that had already formed. It is included in some popular guidebooks but there is much more potential to tell the story of this rock which is immediately beside the coastal path.

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Granite when an upsurge of an explosive gas phase fragmented granite that had already formed. It is included in some popular guidebooks but there is much more potential to tell theConstant story of washing this rock by which the sea is immediatelykeeps the exposu besideres the free coastal of algae, path. seaweed Constant and washing other mate- by therial. sea keeps the exposures free of algae, seaweed and other material.

FigureFigure 16. 16.Blackrock Blackrock Breccia, Breccia, County County Dublin: Dublin: explosion explosion breccia breccia of graniteof granite fragments fragments in granite in granite matrix. matrix. 5.1. The Obscure and the Over-Exposed! 5.1. SoThe much Obscure of and the the effective Over-Exposed! promotion of any type of geoheritage depends on easy accessSo for much the visitorof the effective and the promotion ease with whichof any aty guidepe of geoheritage (in person ordepends by leaflet, on easy app, access etc) canfor pointthe visitor out the and features the ease and with bring which the a geological guide (in person story to or life. by leaflet, Two very app, different etc) can sites,point atout Pollnapeiste the features in Donegaland bring [43 the] and geological at White Rockstory into Countylife. Two Dublin very [55different], demonstrate sites, at contrastingPollnapeiste aspects in Donegal of public [43] accessibility. and at White Rock in County Dublin [55], demonstrate con- trastingPollnapeiste, aspects of is public an unusual accessibility. cave formed in Dalradian marbles, near the mouth of the GweebarraPollnapeiste, River near is an Lettermacaward. unusual cave formed The developmentin Dalradian marbles, of the cave near has the been mouth strongly of the controlledGweebarra by River the folded near amphiboliteLettermacaward. dykes The within development the marbles, of asthe they cave act has as impermeablebeen strongly barriers.controlled Since by the the folded cave requires amphibolite rope dykes access with to enter,in the it marbles, is a really as they strong act example as impermeable of just howbarriers. inaccessible Since the some cave geological requires heritagerope access can to be enter, to a broader it is a really audience, strong both example conceptually of just andhow physically. inaccessible some geological heritage can be to a broader audience, both conceptually andBy physically. contrast, there is a small area of coast at the north end of Killiney Bay that provides interestingBy contrast, geological there stories is a small related area to of igneous coast at rocksthe north but end which of Killiney also exemplifies Bay that someprovides of theinteresting complexity geological of promoting stories geologicalrelated to igneous heritage rocks in competition but which withalso exemplifies other interests. some At of Whitethe complexity Rock, geological of promoting students geological have long heritage been brought in competition to examine with the other contact interests. between At theWhite Dalkey Rock, Granite geological body students and the have country long rock.been brought These metamorphic to examine the schists contact with between large andalusitethe Dalkey crystal Granite growths body and are an the excellent country place rock.to These study metamorphic contact metamorphism schists with by large a large an- igneousdalusite intrusion. crystal growths There is are additionally an excellent an place historical to study lead minecontact associated metamorphism with mineralised by a large fluidsigneous from intrusion. the intrusion. There Theis additionally access to the an site historical is only bylead one mine steep associated path across with a railwaymineral- line.ised However,fluids from the the secluded intrusion. cove The at access the start to the of thissite is section only by has one become steep anpath unofficial across a naturistrailway beach line. However, in recent years, the secluded with sunbathers cove at the reclining start of against this section the same has rocksbecome geological an unof- students would wish to examine! ficial naturist beach in recent years, with sunbathers reclining against the same rocks ge- Such sites displaying igneous rocks also highlight the difficulty in bringing to life hard- ological students would wish to examine! to-imagine scenarios of huge >600 ◦C magma chambers of molten liquid rock when gazing Such sites displaying igneous rocks also highlight the difficulty in bringing to life upon a weathered bit of cold inert grey granite in County Dublin. Parallels drawn with hard-to-imagine scenarios of huge >600 °C magma chambers of molten liquid rock when modern-day volcanoes and the luminous red- and white-hot lavas of Iceland or Hawaii gazing upon a weathered bit of cold inert grey granite in County Dublin. Parallels drawn perhaps help in evoking this type of geological image. with modern-day volcanoes and the luminous red- and white-hot lavas of Iceland or Ha- waii perhaps help in evoking this type of geological image.

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5.2. Small Scale Models As illustrated at the start of this review, the County Wicklow Sugar Loaf’s morpholog- ical imitation of a volcano is misleading and is only noted for its cone-like ‘volcanic’ shape. However, there are small-scale cone-like structures in County Clare that at least have been produced by a process of upward extrusion, albeit in a sedimentary context. These impressive ‘sand volcanoes’, which are only one to two metres in diameter, are found within Upper Carboniferous slumped and deformed siltstones and sandstones at the Bridges of Ross and at Doonaha [56]. They were formed by the extrusion of fine-grained sediment suspended in water as the sediments were compacted. Featured in a guide derived from the CGS Audit [57], they offer great opportunities for exploring the topic of volcanoes on a miniature scale, in an easily-accessible and fun way.

6. Conclusions It is generally accepted that many people are interested in the phenomena of volcanoes and volcanic eruptions for a wide variety of reasons. Many classic tourist destinations actually consist of active or extinct volcanoes and related phenomena. Continuous visitor numbers at accessible volcanoes demonstrate this fascination with the natural world and the enormous power of volcanic phenomena. Based on the unsubstantiated premise that this interest could extend to ancient volcanic rocks and features, in a terrain such as Ireland’s where volcanism ceased many millions of years ago, this review has assessed what volcanic (and broader igneous geology) heritage sites are identified. It has tried to appraise what efforts have been made or are currently in progress to promote the stories behind these sites, as summarised in Table1. Clearly in some locations, such as the Copper Coast UNESCO Global Geopark, volcanic rocks and processes are being actively promoted in the core messages of the Geopark. However, in more cases than not, there is little current promotion, and little telling of these old volcanic stories. This review has presented numerous examples to support the view that there is great potential for helping more people to understand the evidence for old volcanoes spread across Ireland.

Author Contributions: All authors (M.P., S.G. and V.G.) contributed to the different parts of the article. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: The data presented in this study are openly available on Geologi- cal Survey Ireland website at [https://www.gsi.ie/enie/programmes-and-projects/geoheritage/ activities/county-geological-site-audits/Pages/Completed-audits.aspx][8]. Acknowledgments: The authors would like to thank Michael Dempster (Northern Ireland Envi- ronment Agency) for helpful comments on the original manuscript and Eamon Doyle (Burren and Cliffs of Moher UNESCO Global Geopark) for useful clarification on County Clare sites. We are grateful to Brian McConnell for the photograph of the Finny pillow lavas. All observations, data and photographs, except where otherwise stated, are based on CGS audit reports completed as part of GSI’s Geoheritage Programme and published on its website. We especially acknowledge the generous endorsement of Michelle Parkes-Davern in allowing us to complete this paper on behalf of her husband, and our dear friend and colleague, Matthew Parkes, who died unexpectedly in October this year. Conflicts of Interest: The authors declare no conflict of interest.

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