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Home , Ballintoy, Carncastle, Cushendall, Cushendun, Fair Head, Islandmagee

Rockin’ the Causeway Coast & Glens

A Visitors Guide to the of the Causeway Coast & Glens INTRODUCTION INTRODUCTION

The Causeway Coast & Glens provide an opportunity to study an experience hot dry conditions during the Triassic Period (250 - unparalleled variety of geology in a small area. The rocks were 205 million years ago), due to its location close to the current formed in a range of environments from arid desert, warm Sahara Desert. Evaporation left behind large quantities of salt, tropical seas, explosive volcanic eruptions, to cold glacial including the deposits preserved and mined near . conditions. Hints and clues to this geological history are all By the late Triassic Period, marine conditions returned and around us, in the cliffs, mountains and beaches that make up our reptiles emerged as the dominant life form on Earth. natural landscape and in the rocks beneath our feet. With this booklet, take a tour of the Causeway Coast & Glens, and explore The Jurassic Period (205 - 145 million years ago) is the best how this wonderfully scenic area of Northern came to be known geological period and is associated with dinosaurs on the shape it is today. Earth. Evidence from the Jurassic period can be seen at the Waterloo Beds, where fossils such as a mmonites and other Geological History of The Causeway Coast & Glens remains of marine life can be found. - A Brief Overview Some 500 million years ago, what we now know as Ireland The Cretaceous period (145 - 65 million years ago), brought with existed as a number of discrete areas of land and sea floor within it raised sea levels and the return of deeper marine conditions. an ancient ocean called Iapetus. The affect of plate movements During this period, shells and the remains of dead microscopic through time carried the continents across the Earth’s surface, marine plants known as coccoliths were deposited on the sea eventually closing this ocean. The continental collisions which bed, which over time led to the formation of chalk. This chalk, occurred as the ocean contracted altered the mudstones and which is a pure form of limestone, can now be seen in the cliffs at sandstones into other rock types known as schists. These rocks, White Rocks, . which are among the oldest in , can be found today in . The Palaeogene (65 - 25 million years ago), was associated with intense volcanic activity. flows covered the limestone Around 400 million years ago, the Iapetus Ocean had closed and landscape and as this cooled it formed the black which the mountains in Northern Ireland resembled the Himalayas in characterises much of the Northern Ireland landscape. The basalt scale. Ireland and Britain were situated in the rain shadow of the forms the Antrim and and has protected the Caledonian mountain chain and experienced climate conditions underlying Cretaceous chalk from . The most famous not dissimilar to Death Valley in . Erosion of these geological site in Northern Ireland, the Giants Causeway, was upland areas generated the puddingstone conglomerates and formed during this period. Other evidence of this period include sandstones formed in the hot desert conditions that occurred volcanic vents, these are places where the lava exploded out on during the Devonian Period (420 – 355 million years ago) and the surface of the earth. The best example of a volcanic vent can which can be found around and . The be seen today at Carrickarade and remnants of such vents prevailing conditions at this time also led to the evolution of fish include and Moutain. into amphibians, which was a major advancement for animal life on land. Many of the landscape features we see today were formed during the last Ice Age and much of the bedrock across the Flooding of this desert landscape heralded the beginning of the Causeway Coast & Glens is covered by deposits left by the Carboniferous Period (355 – 290 million years ago), when Ireland receding ice sheets. Raised beaches, such as the one at was covered by shallow tropical seas and deltas. Sediments from Harbour and Magilligan Point, are evidence of this time in this era comprise limestone and sandstone formed within major geological history, known as the Quaternary Period (2.5 million river deltas in what is now the Ballycastle area. Abundant growth years ago - present ). in plants in the warm and moist conditions lead to an accumulation of decayed vegetation, forming the coal seams such as those found in Ballycastle. Northern Ireland continued to

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Ma (millions of years) l a c i d g o i o r l e o P e G

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Rock Types in Northern Ireland Igneous rocks form as molten rock cools and solidifies. Basalt is a dark green-black, fine grained in which the crystals are so small they cannot be Basalt seen by the naked eye. This fine crystal size is due to the rapid rate at which the cooled. Dolerite and gabbro are the same composition as basalt but took longer to cool giving the crystals more time to grow.

Period of Formation: Jurassic & Cretaceous & Palaeogene Sedimentary rocks are typically Location: , Co. Antrim composed of particles or pieces of Terrain: Coastal other rocks eroded and laid down in Grid Ref: D462 025 layers over time. Sandstone is a Facilities: Parking and public toilets available at Portmuck , made up of Sandstone grains, most commonly of quartz, The Gobbins, located on the eastern coast of Islandmagee, is known bound together by . for its spectacular basalt cliffs which rise to 60m above sea-level Animals and plants can contribute to sediment particles, The basalt formed some 62 – 60 million years ago during the deposited in layers known as beds eventually becoming Palaeogene Period, when this area was subject to massive consolidated into rock. volcanic fissure eruptions and lava flows which formed the Antrim Plateau. Chalk in Northern Ireland was laid down by accumulation of the At Hills Port, at the southern end of the Gobbins, the are remains of marine algae known as amygdaloidal , which refers to gas bubbles that formed in the coccoliths. lava that have since been filled with minerals known as zeolites. The foreshore and cliffs along the coast of Islandmagee also Chalk expose a sequence of rocks from the Lower Jurassic and Upper Metamorphic rocks have been Cretaceous time periods. The missing Upper Jurassic and Lower subject to intense heat and/or Cretaceous rocks result in a break (or gap) in the geological pressure. A schist is a sequence referred to as an unconformity. metamorphosed mudstone. At Portmuck, west of the Harbour and below the impressive white cliffs of Cretaceous chalk, one of the best exposures of the Hibernian Greensands Formation in Northern Ireland can be seen Schist – these comprise green and brown fossiliferous sandstones that were laid down in beds that are now slightly tilted by later earth movements.

Exposures of Jurassic Waterloo Mudstone Formation can also be seen at low tide as blue clays and limestones.

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Period of Formation: Triassic & Jurassic Period of Formation: Cretaceous & Palaeogene Location: Larne Foreshore, Co. Antrim Location: Located 2km NW of Terrain: Coastal Terrain: Steep & uneven Grid Ref: D387 063 Grid Ref: D333 073 Facilities: Foreshore accessible via promenade Facilities: Parking available 1.8km south of Scawt Hill

Waterloo Beds is a sequence of sedimentary rocks that were laid The summit of Scawt Hill is located about 2km NW of Carncastle down across the boundary of the Triassic and the Jurassic time and marks the outcrop of a composed of a rock periods. It is a unique site in Northern Ireland and is one of the type known as dolerite . The plug fills a conduit, or vent, best in Europe to see this geological transition. through which magma that fed a would have passed during the Palaeogene (some 58 million years ago). Some of that Sediments deposited here during the hot and sometimes arid magma failed to reach the surface and cooled within the vent to conditions of the Triassic Period are known as the Mercia form the plug. The volcano has since been eroded away and the Mudstone Group. They are mainly orange-red mudstones that hill now exposes its root. were laid down in shallow marine conditions and rarely contain fossils. In the late Triassic, the sediments turn pale greyish green Prior to plug formation, large volumes of magma would have and are silty mudstones known as the Collin Glen Formation, that moved through the vent heating its walls and causing them to were laid down in very shallow water. change or metamorphose. The rocks that formed the wall of the vent at Scawt Hill are the Cretaceous White Limestone, These rocks were succeeded by grey and black fossiliferous which led to the unusual variety of minerals found here. mudstones known as the Penarth Group, that were deposited as sea-levels rose. Jurassic rocks are identified by the appearance of Scawt Hill has yielded five minerals entirely new to science; a specific species of ammonite know as Psiloceras planorbis. ; Scawtite; Rankinite; and Hydrocalumite. The discovery of this assemblage demonstrated chemical From the start of the Penarth Group to and mineralogical relationships that had previously only been north of the Waterloo Cottages, anticipated in theory. abundant fossils known as bivalves, crinoids and ammonites can be found. The site is designated an Area of Special Scientific Interest, by reason of its geology and flora. This area is popular for spotting The site is best visited on a falling or Peregrine Falcons and the Irish Hare. low tide.

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Period of Formation: Palaeogene Period of Formation: Cretaceous & Palaeogene & Quaternary Location: Carnstroan, 12km east-northeast of Location: 6km north-northeast of Terrain: Steep & rocky Terrain: Coastal & Bog Grid Ref: D222 054 Grid Ref: D303 237 Facilities: Parking, toilets and information are available here Facilities: Car park available

Slemish Mountain is a 800m long by 200m wide volcanic plug Garron Point reveals evidence of a geological process referred to and remnant of an ancient volcano which existed here some 58 as rotational slip, in which large blocks of basalt and chalk move million years ago during the Palaeogene Period. It is the largest down slope. Rotational slips are a well known geological volcanic plug in Ireland and its distinctive shape makes it a phenomenon around the edge the Antrim Plateau. recognisable landmark for many miles on the Antrim Plateau. The slippage that occurred here dates back to the end of the last The mountain is composed of a rock glacial period of the Ice Age (some 13,000 years ago), when the type called dolerite which formed Scottish ice sheets were in retreat. The ice had eroded and when magma cooled at a shallow over-steepened the Antrim Plateau escarpments in parts and depth beneath the Earth’s surface. this led to the instability. This instability was exacerbated by the soft Jurassic mudstones which underlay the chalk and basalt. The dolerite of Slemish is harder than the surrounding basalts into which it As a result Garron Point is a good site to view blocks of black was injected (intruded) , as a result basalt at the same level as the Cretaceous chalk. glaciers did not erode the plug as Garron Point forms the edge of the Garron Plateau, an area readily, thus its prominent location 200 characterised by a plethora of designations. It contains the most metres above the surrounding land. extensive area of intact upland blanket bog in Northern Ireland Slemish is associated with , the Patron Saint of and represents one of the best examples of this habitat in the Ireland, who was brought here as a boy and lived here as a UK. The peatland supports a number of rare and notable plant shepherd for six years. and animal species, and a diverse upland breeding bird population. The plants found on the slopes of Slemish are typical of It is duly designated a Ramsar Site, a Special Area of mountain and moorland. The large black raven is a common Conservation, an Area of Special Scientific Interest and an Area sight here. of Outstanding Natural Beauty.

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Period of Formation: Devonian Period of Formation: Palaeogene Location: Cushendall Location: West of Cushendall Terrain: Coastal Terrain: Steep, uneven, unsuitable for walking Grid Ref: D245 272 Grid Ref: D194 268 Facilities: Parking available at Harbour in Cushendall Facilities: No access/parking available. Long range views available from Causeway Coastal Route Rocks along the Antrim Coast from Port Obe at Cushendall to Cushendun form what is referred to in geological terms as the Tievebulliagh is the prominent hill located 4km west of Cross Slieve Group. These rocks are 350-400 million years old, Cushendall of which glimpses can be seen from the coast road. associated with the Devonian Period. The Palaeogene that formed the Antrim Plateau took Rocks on the shore of Port Obe display both mudstone & place between 62 and 58 million years ago and constituted two sandstone from this period and are known as the Ballyagan outpourings of basalt lava flows separated by an interval of Formation. dormancy. The climate during this interval was subtropical with high levels of rainfall which lead to the surface of the Ridges of uncommon purple-red sandstone, varying in grain size, basalts rotting to create a red soil known as laterite . When a protrude through beach deposits here. volcanic vent later punched through this lateritic soil, the hot In some places, the top of these ridges magma caused it to bake, forming the unique and extremely is characterised by a thick bed of hard hard rock Porcellanite . pale green mudstone, featuring large During the (4000 to 2,500 BC) Tievebulliagh was the cracks filled with sand. These cracks, site of a stone axe factory. The highly prized porcellanite axes known as dessication cracks, are were traded across Ireland and Britain during this time. associated with the intense heat associated with the Devonian period, Abundant flakes of porcellanite can be found amongst the loose which hardened the rock. These rock debris (scree) at the foot of Tievebulliagh and represent the cracks have filled with sediment rough working or shaping of the tools produced here. subsequently washed over them. Occurrences of this rock type are restricted in Ireland to this location and Brockley on . A collection of The coarse, pink sandstone forming the cliffs on the north side porcellanite artefacts, including the Malone Hoard, can be seen of Port Obe are also part of the Ballyagan Formation. in the in .

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Period of Formation: Precambrian Period of Formation: Precambrian & Triassic & Cretaceous Location: North of Cushendun Carboniferous & Palaeogene Terrain: Coastal Cliffs Location: East of Ballycastle Grid Ref: D234 407 Terrain: Coastal Facilities: Torr Scenic Route available via Causeway Coastal Grid Ref: D196 423 Route, unsuitable for large vehicles Facilities: Parking Available

Torr Head, located approximately 7km north of Cushendun, is A diverse range of geology can be viewed including all of the composed of metamorphic rocks of Precambrian age (around three main classes of rocks - igneous, sedimentary and 600 million years old). metamorphic at Murlough Bay. Meta- is used in front of the rock names to indicate that they The oldest rocks occur at the eastern side of the bay and are have been metamorphosed. The rock types found at Torr Head Dalradian schists, which are just over 600 million years old. include grey meta-limestone and pinkish meta-sandstone (or Red sandstone dating from the Triassic Period overlies the psammite) that were originally laid down as sediments in an schists, and the boundary between the two is an unconformity opening ocean. As the ocean (known as Iapetus) opened, representing a gap of some 350 million years. magma was created and injected into the sediments; the resulting igneous rock type formed is known as metabasite . A second unconformity, is seen where Cretaceous white Sedimentary structures (beds and cross-stratification) limestone overlies the Triassic sandstones. A conglomerate (a preserved in the limestone and psammites indicate that they rock composed of rounded pebbles of pre-existing rocks) is have all been turned upside-down (inverted), and as such found at this unconformity and contains fossils which indicates represent part of a large fold structure in the rocks. that Jurassic rocks were here and later removed . The folding and were the consequences of an Fair Head itself is a body of igneous rock which pushed its way intense period of mountain building that took place about 470 through older Carboniferious rocks forming a structure known million years ago which resulted in the formation of the as a . The sill is made of a dark green-black, medium grained Caledonides range. dolerite that displays columnar structure not unlike those seen These rocks are collectively referred to as the Dalradian at the Giant’s Causeway. Supergroup and can be traced from northeast west in the Sperrin Mountains and east into . The rocks at Torr Head are best viewed from the southeast side of the headland, below the abandoned Coastguard station.

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Period of Formation: Carboniferous & Palaeogene Period of Formation: Cretaceous & Palaeogene & Quaternary Location: Ballycastle Location: Coastal Island, approx 9.5 miles from Ballycastle Terrain: Coastal Terrain: Coastal Grid Ref: D136 417 Grid Ref: D148 510 Facilities: Car-parking & facilities available in Ballycastle. Facilities: A regular ferry service runs between Ballycastle and Rathlin weather permitting. Facilities available on the island

Ballycastle is one of the few places in Northern Ireland where The geological structure of Rathlin Island, which can be viewed sedimentary rocks belonging to the upper part of from the mainland, exhibits the startling contrast between the Carboniferous Period (also referred to as ‘the Coal Measures’) Cretaceous white chalk and the overlying black Palaeogene can be examined. basalt. The rocks here are mainly sandstones and mudstones with A break in Palaeogene volcanic activity is recorded in the abundant fossil plants and evidence of animal activity. The uppermost lava flows of the Lower Basalt Formation by the sediments that formed these rocks were deposited in a delta to orange-red laterite preserved at various levels across the island. shallow marine setting. Vegetation was abundant on the delta This deposit represents an ancient weathering that took place and built up into layers of peat that was later preserved as when rains and the subtropical conditions rotted the basalt seams of coal. landscape surface. The cliffs at Pans Rock have been designated as an Area of This quiet period was interrupted by the eruption of lava flows Special Scientific Interest known as the Ballycastle Coalfield, that on the mainland formed the Giant’s Causeway. The and is the best exposure of a coalfield sequence in Ireland. resulting rock formation (the Causeway Tholeiite Member) also Examples of the coal seams and abandoned adits are visible at displays the famous columnar forms. Maguires Strand Caravan Park. Under no circumstances should Rathlin also displays evidence of post-glacial sea-level changes these mines be entered as they are highly dangerous due and isostatic uplift. Both were due to the melting and retreat of to instability. Scottish ice. The melting initially raised sea-level, but this was Coal mining here dates back to the 13th Century and continued followed by the rise of the landscape due to it being unloaded until the 1960’s. This area corresponds closely with the of its ice (like taking the cargo off a ship) , the interaction of Machrihanism Coalfield in Kintyre, Scotland. these processes created the platforms and raised beaches seen at various places around the island including Church Bay and Rue Point.

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Period of Formation: Palaeogene Period of Formation: Cretaceous Location: 2km east of Ballintoy Location: Ballintoy Terrain: Coastal Terrain: Coastal Grid Ref: D061 449 Grid Ref: D038 456 Facilities: : Car-parking, toilets and catering facilities Facilities: Car-parking, toilets and catering facilities available here available here

The island of Carrickarade and adjoining mainland reveal a From Ballintoy Harbour west to Whitepark Bay, the shoreline section through a Palaeogene volcano which exploded here consists of metamorphosed chalk. This is the chalk laid down in some 62 million years ago. marine conditions during the Cretaceous which has been covered with and metamorphosed by the molten lava of the Palaeogene. The island is a volcanic plug composed of a dark green to black, medium-grain igneous rock known as dolerite. Once the The Bendoo volcanic plug, a black forms the famous rope bridge has been crossed, the view back to the headland and this can be seen beside the old coastguard station mainland reveals large, angular, blocks of black Palaeogene on the cliff-top, east of the Harbour. basalt, white Cretaceous chalk and grey Jurassic limestone A line of weakness in the earth exists here, known as the embedded in a sandy coloured volcanic ash. These deposits are Ballintoy Fault , which forms part of the larger Portbradden Fault. known as agglomerate and demonstrate the explosive nature Erosion has occurred here and as a result of movement along of the volcano that formed them. this fault, the chalk exhibits a fractured appearance. This rock The chalk cliffs at Carrickarade host a raised sea cave which has type is known as rock breccia . the only known example of a speleotherm within the Ulster Large scale mining of the chalk occurred in this area and this industry White Limestone. The speleotherm ,includes stalactites, lead to the establishment of the harbour here. Mining of the chalk is stalagmites and a pillar and are thought to be a unique feature also evidenced in the numerous lime kilns dotted around the area within the Cretaceous of Ireland and Britain. including the kiln that can be seen at Ballintoy Harbour. The cliff-top habitats include maritime grassland, acid heath Ballintoy is notable for its well raised shoreline, its formation and chalk grassland. The site is home to two rare snails, the associated with changes in sea level. During the last Ice Age, wrinkled snail and the heath snail, and breeding birds include massive sheets of ice caused the land to sink here. Over time as twites, kittiwakes, guillemots and razorbills. temperatures rose and the ice sheets receded, this land slowly began to emerge, a process referred to as isostasy. The disused quarry at Ballintoy Harbour Carpark shows a raised sea cave.

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Period of Formation: Jurassic & Cretaceous Period of Formation: Palaeogene Location: Between Ballintoy & Portbradden Location: Giants Causeway Terrain: Coastal Terrain: Coastal Grid Ref: D001 440 Grid Ref: C945 440 Facilities: Signposted from Causeway Coastal Route. Facilities: Parking; public transport link & range of facilities Parking available adjacent to YHA Hostel available here

Rocks deposited during the Lower Jurassic Period (also known as The Giant’s Causeway sits within a dynamic coastal landscape of the Liassic or Lias) are present in Whitepark Bay. Towards the rugged cliffs, majestic headlands and secluded bays. It is eastern side of the bay, during periods of low tide, grey mudstones designated a World Heritage Site by UNESCO in recognition of its and limestones of the the Waterloo Mudstone Formation can be outstanding geology and exceptional natural beauty. observed. Marine fossils such as ammonites, belemnites and Rocks that form the Giant’s Causeway date from the Palaeogene bivalves can be collected amongst the rocks here. Period and are related to large scale volcanic activity which The younger, Cretaceous chalk is mainly exposed in the cliffs precluded the opening of the north Atlantic Ocean approximately behind the sand dunes and contain fossils such a belemnites, 55 million years ago. sea urchins and brachiopods . The Causeway is made up of tens of thousands of basalt columns The ground behind the beach and that together are referred to as the Causeway Tholeiite Member. dunes is uneven because of The columns are preserved within lava flows that flooded a valley numerous land-slipped blocks. After that had become blocked – the result was a lava lake that cooled the last glacial period when the gradually but evenly. As the lava cooled it contracted and formed Scottish ice had retreated, the cliffs the regular hexagonal shapes that we see today. The majority of here were left in a seriously over- the columns are five, six or seven sided with a few four and eight steepened state. This coupled with sided columns scattered around the site. the soft clay underlying the chalk Occurring below the columnar basalts are a number of thinner caused instability in this area. lava flows of the Lower Basalt Formation. The top of this rock The time interval between the last Liassic mudstone rocks and formation was weathered due to the warm wet conditions during the first Cretaceous rocks is over 100 million years. This gap in a period of volcanic inactivity to form a deep orange-red material the geological sequence is known as an unconformity. known as laterite. Famous features to look out for include the Giant’s Organ, Eyes and Boot, and the Chimney Stacks.

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Period of Formation: Quaternary - recent Period of Formation: Cretaceous & Palaeogene Location: Location: Between Portrush & Portballintrae Terrain: Coastal Terrain: Coastal Grid Ref: C929 425 Grid Ref: C884 407 Facilities: Parking & toilet facilities available beside Facilities: Parking & toilet facilities available here Portballintrae Village Hall

The coastline at Runkerry Strand undergoes constant change The name White Rocks is derived from the magnificent white and absorbs more energy from waves than any other beach in chalk cliffs that date to the Cretaceous Period. A thick layer of Northern Ireland. As a result of this, the beach demonstrates black basalt caps this white chalk, evidence that lava flowed over strong seasonal variation. During adverse weather the beach this area during the Palaeogene Period. can be stripped of sand, and conversely, during fair weather, Numerous volcanic vents can be seen in the chalk cliffs at White typical of summer months, the beach is fed material. Rocks. Agglomerate is a rock type that is found within these The , which enters the Bay at the southwest corner of vents,and is comprised of rounded and angular boulders of basalt the strand feeds the beach with terrestrial sediment, which is and chalk reflecting the explosive nature of the volcano. crucial to balance out the material lost to the destructive waves The vents in this area are thought to have formed due to the battering the beach during the winter months. escape of gas and boiling fluids released by the formation of the A significant dune system backs the Portrush sill, which intruded the Jurassic sediments present below beach and is thought to been formed White Rocks. in two different phases. Dunes Fossils in the chalk include brown, bullet-shaped belemnites, sea shoreside of the tramline date back urchins and brachiopods . 4000 years ago, while the older dunes behind the tramline date back 5000 - To the east of White Rocks, is constructed on 6000 years. agglomerate. The unstable nature of the underlying geology at this location may have led to the dramatic events reported in The rapid rate of change at Runkerry Strand makes it an ideal 1639, when during a storm, the castle kitchens plunged into the site to study seasonal changes in the beach environment. sea below killing several staff.

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Period of Formation: Palaeogene & Jurassic Period of Formation: Quaternary Location: Portrush Location: Magilligan Terrain: Coastal Terrain: Coastal Grid Ref: C855 413 Grid Ref: C662 392 Facilities: Various parking & facilities available in Portrush Facilities: Parking available near entrance to Martello Tower.

Portrush is built upon a large body of Palaeogene igneous rock, Magilligan in the Binevenagh AONB is one of the largest which was intruded into older Jurassic rocks as magma. Such a calcareous dune systems in the country. It is also noted for its body is referred to as a sill, and the Portush example is one of unmodified system of dune ridges and slacks and the great the thickest in Northern Ireland. number of dune grassland and dune slack plant communities. This is an internationally important locality in the history of The site also exhibits a record of Holocene sea-level changes that geological study, as it caused much debate during the 18th occurred as ice-sheets from the last glaciation receded. Flooding century between two schools - the Neptunists and the occurred of the Lower Lough Foyle and material from a cliff, which Vulcanists. Neptunists believed that basalt precipitated out of can still be traced around the Lough, was transported. Gravel sea water, whilst vulcanists believed that it was the result of ridges formed as a result of this process. As land levels rose with volcanic activity. the retraction of ice sheets and corresponding sea levels fell, lower volumes of water flowed in and out of the Lough. The occurrence of ammonites, in what Nepunists believed was basalt, supported their theory. However, the Vulcanists were When sea levels stabilised approximately 1500 years ago, sand able to show that although these rock closely resembled basalt, supply for ridge development was exhausted and erosion of the they were in fact sedimentary rocks, which as a result of the shoreline of Lough Foyle commenced until it stabilised to its heat from molten lava, had been baked and metamorphosed current position. This erosive phase released sand, which was into a different rock type, known as hornfels. swept along coastline through long shore drift and sand drove ashore formed the dune systems seen today. The dunes located The Skerries are a chain of small islands, 2km offshore and along the front reach a height of 17m in places. represent a continuation of the Portrush sill. Given the distribution of the islands and exposed rocks onshore the sill Eastwards from Benone to Downhill, the coastline is relatively can be shown to be elliptical in shape. stable, however westwards the system is subject to significant erosion, up to 3 metres a year. The Magilligan system is the most intensively studied coastal accumulation site in Ireland and amongst the top such localities in Europe.

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Agglomerate: A rock type formed from a combination of fragments of debris produced from explosive volcanic activity. Ammonite: A now extinct marine animal that is related to the modern nautilus/squid. Amphibian: A cold blooded vertebrate. The larvae live in water and breathe using gills, the adults live on both land and water and breathe using lungs. Amygdaloidal Basalt: Bubble, or vesicles, in lava (in this case basaltic lava) that have been filled with minerals. Basalt: A volcanic igneous rock which is dark in colour, fine grained and basic in composition and which was originally erupted as lava. Belemnite: Belemnites (or belemnoids) are an extinct group of Period of Formation: Palaeogene & Quaternary marine life, very similar in many ways to the modern squid Location: Approximately 8km from Bivalve: A class of marine and freshwater molluscs. Their shell Terrain: Steep, Rocky, Cliff consists of two asymmetrically rounded halves known as valves Grid Ref: C692 309 which are mirror images of each other and joined by a hinge at Facilities: Parking available beside the Lake at Binevenagh summit. one end. Nearest parking to Binevenagh Nature Reserve at the base of the Blanket Bog: An area of peatland which forms over a large area cliff is 3-4 mile walk from nature reserve entrance. in conditions of high rainfall and low levels of evapotranspiration Brachipod: Any of various marine invertebrates of the phylum The imposing cliffs of Binevenagh, overlooking the flat plains of Brachiopoda, having bivalve dorsal and ventral shells enclosing a Magilligan, comprises a stack of basalt lava flows (some 100- pair of tentacled, armlike structures that are used to sweep 150m thick) overlying white Cretaceous chalk. minute food particles into the mouth. Also called lampshell. Breccia: A breccia that was formed due to tectonic processes. Huge rotational landslips are evident on the western escarpment It is an unconsolidated rock composed of broken, fragmented rocks. of Binevenagh, where blocks of basalt and chalk have migrated Calcareous: Mostly or partly composed of calcium carbonate. downslope. This instability can be attributed to erosion and Carboniferous: Geological time period extending from 354 over-steepening of the escarpment during the last Ice Age. million years ago to 290 million years ago. After the ice had retreated the block slumped into the underlying Chalk: A soft, white, porous sedimentary rock - a form of soft Jurassic clays. limestone that is composed of the mineral calcite (calcium carbonate). It forms in deep marine conditions as a result of the In between the basalt cliffs and the lower grassy slopes is an area build up of the shells of microorganisms known as coccoliths. of loose rock debris known as scree . The deposit has formed by Clay: A naturally occurring material that is very fine grained and freeze thaw action of the steep cliffs over time. forms due to long periods of chemical weathering of silicate bearing rocks. The site is noted for its artic-alpine plant community, hosting Coccolith: A microscopic marine algae with a calcareous outer shell. rare species including Moss Campion, Mountain Avens & Purple Saxifrage. These plants are found in few places in Ireland, but Conglomerate: A sedimentary rock which is made up of fragments which range in shape and size. have survived for thousands of years since the last Ice Age in the soils and micro-climate that characterises the high cliffs Cretaceous: Geological time period after the Jurassic but before the Palaeogene, from approximately 142 million years ago to 65 of Binevenagh. million years ago. The peregrine falcon and the buzzard, both birds of prey, nest in Crinoid: Also known as "sea lilies" or "feather-stars", are marine the cliffs here. animals that make up the class Crinoidea of the echinoderms (phylum Echinodermata). They live both in shallow water and in depths as great as 6000 meters. Crinoids are characterized by a mouth on the top surface that is surrounded by feeding arms.

25 | www.ccght.org www.ccght.org | 26 GLOSSARY OF TERMS GLOSSARY OF TERMS

Dalradian: A term that represents metamorphic rocks associated Limestone: A sedimentary rock composed mainly of calcium with the opening and closing of the Iapetus Ocean. They are carbonate in the form of the mineral calcite. mostly from 600 – 420 million years ago. Lower Basalts: The term given to the first series of that Desiccation cracks: A feature that form as a result of drying out. flowed across the region some 62 – 60 million years ago during They confirm environments which are hot and arid that the Palaeogene Period. experience periodic rainfall followed by periods of drying out. Magma: Molten rock that, when cooled, forms an igneous rock. Devonian: Period of geological time extending from 417 million Magma that extrudes onto the surface is termed lava and magma years ago to 354 million years ago. The Carboniferous is the time that intruded below the surface and solidifies there forms period after and the Silurian the time period before. intrusive igneous rocks. Dolerite: An igneous rock which is dark in colour, medium Marine Transgression: A geological event whereby sea levels grained and basic in composition. It has the same composition as rise relative to the land surface causing the shoreline to move to basalt only coarser crystals due to the rate of cooling. higher ground. Dune Ridges: In areas of large-scale dune activity, certain types Mercia Mudstone Group: A sequence of sedimentary rocks that of dunes result in sand ridges occurs widely across Britain and Ireland. It consists of mudstones, Dune Slacks: Low-lying depressions within a dune system siltstones and sandstones and is Triassic in age. Fault: A planar fracture within a volume of rock over which Metabasite: A collective term, for metamorphosed rock that has significant movement can occur. It is a line of weakness that lost all traces of its original texture and mineralogy owing to forms due to tectonic processes. complete recrystallization. Flint: A rock type composed of microscopic crystalline silica. It Metamorphism: This process is the recrystallization of pre- forms nodules within the Cretaceous Chalk existing rocks due to changes in physical and chemical conditions, primarily heat, pressure, and the introduction of Fold/Folding: A deformation process that results deep within the chemically active fluids Earth, at high temperatures and pressures. It results in rocks that appear to have been bent. Mudstone: A sedimentary rock composed of clay size particles. It is structureless and unlaminated. Freeze-Thaw Action: A type of weathering process that operates when the temperature is around the freezing point of water. It Neolithic: Prehistoric period related to the Stone Age beginning operates on the basis that water contracts when it thaws and around 4500 B.C. characterized by the development of expands when it freezes resulting in a change in volume. agriculture and the making of polished stone implements Therefore water in pore spaces or fractures in rocks causes them Neptunist/Neptunism: A discredited scientific theory which to weaken and ultimately to break up. dates back to the 18th Century which proposed that rocks formed from the crystallisation of minerals in the earth’s oceans. Hibernian Greensands Formation: A division of the Cretaceous rocks in Northern Ireland. This formation is restricted to the south Olivine Basalt: A type of basalt that has an abundance of the and eastern fringes of the Antrim Plateau. mineral olivine. Olivine is a yellow-green magnesium iron silicate mineral. Holocene: Geological epoch within the Quaternary period. It encompasses the last 10,000 years. Palaeogene: Geological time period extending from 65 million years ago to 23 million years ago. Hornfels: A name of a group of contact metamorphosed rocks that have been baked by the heat of an igneous intrusion. They Penarth Group: A formation of rocks deposited over a period of are usually very hard and fine grained rocks. approximately 4 million years associated with the close of the Triassic period. Isostasy: Describes the process that occurs when temperatures rise and ice melts the weight of the ice is removed from the Porcellanite: So called due to its fine-grain blue appearance that surface of the Earth causing the Earth’s crust to gradually rise up; looks like porcelain. It forms by the heating of weathered basalt this is the process of isostasy. (laterite). The heat comes from the neighbouring volcanic plug. Jurassic: Period of the stratigraphical column from Psammite: A medium grained that was approximately 206 million years ago to 142 million years ago. originally sandstone. Laterite: A weathering product, commonly igneous rocks. Pyroclastic: A volcanic rock fragment/deposit that is ejected into Generally occurs in wet tropical conditions and produces a the air during a volcanic eruption. reddy/brown sediment Quaternary: Period of the stratigraphical column extending from Liassic/Lias: Term used in defining the lower part of the Jurassic Period. approximately 2.6 million years ago to the present. It is characterised by grey clays and mudstones in northeast of Ireland. 27 | www.ccght.org www.ccght.org | 28 GLOSSARY OF TERMS REFERENCES & ACKNOWLEDGEMENTS Abbreviations Raised Beaches: Coastal beaches and other formations such as cliffs and caves that are above the present shore line. They AONB: Area of Outstanding Natural Beauty formed after the Ice Age when the sea level was higher due to melting of the ice. ASSI: Area of Special Scientific Interest SPA: Special Protection Area Ramsar Site: Wetland sites of international importance SAC: Special Area of Conservation designated under the Ramsar Convention NNR: National Nature Reserve Rotational Slip: The slipping of a rock unit along a curved plane WHS: World Heritage Site on a decline. Sandstone: A sedimentary rock composed of cemented sand References grains. Its grain size can vary. A Geological Excursion Guide to the Causeway Coast Schists: A metamorphic rock which has been subjected to high - Paul Lyle (EHS) 2ND Edition 2005 temperatures and pressures deep within the earth. It is A Story Through Time - Patrick McKeever (1991) characterised by its shiny appearance due to the formation of secondary mica. The Classic Geology of the North of Ireland - Ian Mitchell, Mark Cooper, Patrick McKeever & Brian McConnell (2010) Scree: Accumulation of broken rock fragments on a slope. The Geology of Northern Ireland: Our Natural Foundation - Sill: Horizontal (or near horizontal) body of igneous rock that has Geological Survey of Northern Ireland (2004) been intruded into older sediments in which it lies conformably. The North of Ireland – Classic Geology in Europe Speleotherm: Formations that commonly form in limestone caves - Paul Lyle (2003) Tombolo: A bar that extends outward from the shore, connecting www.doeni.gov.uk/niea/biodiversity with an island. www.doeni.gov.uk/niea/landscape Triassic: Time period extending from 248 million years ago to www.habitas.org 206 million years ago. Unconformity: A surface of erosion or non-deposition that Acknowledgements separates younger rocks from older rocks. It represents the This publication has been produced by the Causeway Coast & passage of time. Glens Heritage Trust with the financial assistance of the Rural Upper Basalts: The termed given to the second cycle of lavas Development Programme, Northern Ireland Environmental that flowed across the region during the Palaeogene 65 million Agency and the Northern Ireland Tourist Board. years ago to 23 million years ago. Special thanks to Mark Cooper & Patrick McKeever, Geological Survey Volcanic Cone: Created by eruptions that throw out mostly small Northern Ireland for their invaluable assistance with this project. pieces of rock that build up around the vent. These can be relatively short-lived eruptions that produce a cone-shaped hill The CCGHT provides a secretariat service to the Antrim Coast & Volcanic Plug: A volcanic landform formed when magma Glens, Causeway Coast & Binevenagh AONB Management hardens within a volcanic vent of an active volcano. Groups. The Trust is grateful for support from the Northern Volcanic Vent: A volcanic opening, sometimes a pipe, which can Ireland Environmental Agency an agency with the Department of often be filled with fragmental material. the Environment, Northern Ireland Tourist Board, ; Borough Council, Limavady Borough Council, Waterloo Mudstone Formation: Also known as Lias Clay, it was & Ballymena Borough Council. deposited in the Jurassic approximately 200 million years ago. World Heritage Site: A UNESCO World Heritage Site is a place Photo Credits: (such as a forest, mountain, lake, desert, monument, building, Ballymena Borough Council; Geological Survey Northern Ireland; complex, or city) that is listed by the UNESCO as of special cultural Limavady Borough Council; Mike Hartwell; Northern Ireland or physical significance. Environmental Agency; Northern Ireland Tourist Board & Ulster Museum. Zeolite: A mineral with a porous structure, formed where volcanic rocks and ash layers react with alkaline groundwater For information on the work of the Causeway Coast & Glens Heritage Trust please contact the staff at the following address: Tilly Molloys 18 Main Street, Armoy, Antrim BT 53 8RQ. Tel: (028) 20752100 Fax: (028) 20752101 Or visit our website www.ccght.org Design by: www.thinkstudio.co.uk 29 | www.ccght.org www.ccght.org | 30