Burren and Cliffs of Moher UNESCO Global Geopark - Geology

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Stress Release in The Burren 

One of the most striking features of the Burren are 

the vertical cracks or fissures in the limestone. They 

are known as ‘grikes’ although I prefer the local 

term ‘Scealps’. For most people they are just the 

things you have to step over, however they initially 

formed as fractures almost 300 million years ago. At 

that time, we were down near the equator and the 

tectonic plates on Earth were colliding to form one 

supercontinent called Pangea. This slow collision 

built up huge stresses in the rocks which eventually 

fractured, releasing the stress. This is the same 

process by which Africa is colliding with Europe 

right now and causing Earthquakes throughout 

southern Europe, most recently in Croatia. This is 

all part of the journey of the tectonic plates that 

make up the Earth’s crust as they move around on 

their merry slow dance through geological time. 

This fracturing in the Burren limestone opened 

millions of thin vertical gaps (mostly oriented 

nearly North -South) which were then filled by 

fluids which had been trapped at depth under 

enormous pressure. These fluids crystallized in 

the gaps forming thin mineral veins, mostly of 

calcite, which effectively sealed the fractures. These 

fractures remained buried and sealed until the 

rock was brought to the surface and exposed to 

the potent force of rain, which slowly dissolves the 

veins and limestone, particularly under acidic soils. 

A second set of fractures (mostly oriented East- 

West) formed much later as the rocks that buried 

the limestone were removed by erosion on our 

long journey from the equator to here. We know 

that at least a couple of kilometres of rock have 

been eroded over the last 300 million years. 

Removing that huge weight also released further 

stresses which caused the rocks to fracture. 

Finally, a third stress was caused by the weight 

of thick ice sheets on the limestone surface 

during the ice age. This weight pressed down 

on the rock surface building up new stresses 

which were released after the ice melted, forming 

new fractures which are mostly horizontal. 

So the fractured surface of the Burren is all about 

stress release. Next time you are there, just relax. 

Article written by Dr. Eamon Doyle, Geologist for 

Burren and Cliffs of Moher UNESCO Global Geopark, Clare County Council. 

www.burrengeopark.ie

The patterns on Moher Flags are ancient geological footprints. 

Geological footprints leave 

elegant patterns 

Justifiably famous for their elegant patterns, 

Moher flags have been quarried along the 

west coast of Clare for centuries. The thin, 

rigid slabs were ideal for roofing in times 

past but more recently they are primarily 

used for paving stones and decorative walls. 

The quarrying methods have hardly changed, and 

the family-owned quarries still extract the slabs 

manually, using techniques handed down through 

the generations. To a geologist, the Moher flags 

(short for flagstones) are sandstones. That means 

they are sedimentary rocks composed of grains 

of sand between 0.06 and 2mm in diameter. The 

grains of sand are mostly the mineral quartz 

with some calcite as well as more exotic minerals 

such as feldspar, biotite and chlorite. These sand 

grains were eroded from long-gone mountains 

and transported by extinct rivers into a sea 

that disappeared over 300 million years ago. 

Dr. Shane Tyrell of NUIG and his student Martin 

Nauton- Fourteu have been studying the ancient 

transport patterns (provenance) of these grains 

in similar rocks along the coast of Clare and have 

shown they were carried here from the south/ 

southwest. As fascinating as that is, the internal 

composition of the sandstone is overshadowed 

by the beautiful, complex patterns on the 

surface. These patterns are called ‘trace fossils’; that 

is, they are the marks left by living creatures but 

not the creatures themselves. They are geological 

footprints. The patterns are actually burrows, 

made by an organism as it burrowed horizontally, 

just below the surface on a sandy coast. 

The creature was ‘mining’ the sand for organic 

matter, taking it in at one end, extracting the food 

and packing the processed sand behind itself 

at the other end - this is why the burrows were 

able to be preserved. The trace fossils are very 

abundant, so we know the creature was ideally 

suited to the environment, however, the lack of 

other fossils or trace fossils indicates difficult 

living conditions, so this creature must have 

had some advantage to have been able to thrive. 

If you look closely at the burrows you will see a 

central ridge. This was likely produced by a siphon 

of some kind sticking up from the creature as it 

burrowed, most likely connecting it to the overlying 

seawater, perhaps giving it access to more oxygen, 

just like a snorkel. We have never seen any hardshell 

fossils in these burrows, and it is tempting to 

say that the creature did not have a shell. However, 

calcite shells can dissolve very quickly once buried 

if the groundwater is slightly acidic and the 

chance of shells being preserved as fossils is low. 

The trace fossils of the Moher flags are an 

active area of research for us right now, so 

watch this space for further updates. Why 

not get a look at the Moher Flag Stones in 

person by paying a visit to the Cliffs of Moher. 




When is a volcano, not a volcano? 

When it is a sand volcano? 

Along our coast from Doolin to the Shannon 

Estuary there are a few nice examples of sand 

volcanoes. Sand volcanoes are low conical 

mounds, often with a shallow central depression, 

resembling a volcano and its crater. Internally 

they are made of layers of sand and have a central 

vertical core, also originally composed of sand, all 

now turned to rock as sandstone. They are found 

within the rock layers so have been there for over 

300 million years, and they range in size from a 

couple of centimetres to over a metre in diameter. 

Sand volcanoes (also known as ‘sand boils’) 

are formed by water and sand, not lava. They 

generally form in areas where there is a high 

rate of sedimentation, such as a delta, where 

successive large amounts of sand and mud are 

transported by rivers into the sea after heavy rain 

or storms. Water can become trapped and buried 

with the sediment. The weight of successive layers 

of sediment puts pressure on the underlying 

water-laden layer raising the water pressure 

which eventually erupts onto the seafloor. As the 

water pours onto the seafloor it carries some of 

the sand with it and deposits layers of the sand 

around the vent, building up the cone shape. 

The weight of the sediment alone is often 

enough to trigger a sand volcano; however, sand 

volcanoes are also known to be formed during 

Earthquakes, as the seismic shock can cause 

sediment to become liquidized and unstable, 

forcing water to escape from the sediment. 

You can get an idea of what happens if you stand 

on a beach near the waves and jiggle your feet; 

you will see water gathering around your feet, this 

is a result of the grains of sand and the water reorganizing 

themselves under the pressure of your 

weight, forcing the water to the surface. So, along 

with other evidence, these sand volcanoes tell 

us that the sand that now forms the rocks from 

Doolin to the Shannon Estuary was deposited 

quickly, on a delta (search for the Mississippi or 

Ganges deltas for comparison) and may have been 

affected by Earthquakes. Earthquakes would have 

been common at that time as the large continent 

we were on was colliding with another one. Also, 

for those of you disappointed by the fact that 

they are not real volcanoes, we do have some 

volcanic rocks in Clare, as 330-million-year-old 

lavas are known from the Quin-Kilkishen area. 

Thankfully, these areas are geologically more 

tranquil these days, however, the enormous power 

of the Atlantic Ocean now batters those rocks and 

bit by bit returns them back to the sea, where they 

will ultimately be buried and turned to rock again. 




History in water flowing 

through the Burren 

FRESH water is vital for life, and our position in 

the solar system means that our planet has plenty 

of the good stuff. Fresh water has played a huge 

role in the development of the geological history 

of the Burren; from the rivers that once flowed 

into long-gone seas more than 300 million years 

ago to make the rocks of the Cliffs of Moher, to 

the massive frozen sheets of ice that carved the 

valleys in the Burren just a mere 20,000 years ago. 

All the water on Earth is constantly being 

recycled, the same water that the fossil corals 

were living in 330 million years ago is a tiny 

part of the water we drink every day. This is 

important, as there is no new source for water 

on Earth, so we really do need to look after it. 

As we all know, most of the water that falls on 

the Burren comes from clouds that develop 

over the Atlantic Ocean which are pushed 

here by southwesterly winds. That water was 

very recently salty sea water, but the process of 

evaporation extracts the fresh water and it ends 

up falling on us and the rocks of the Burren. For 

the most part, this rainfall ends up flowing down 

the cracks in the limestone and disappearing 

underground and surface water is very scarce here. 

The Caher River and the Aille River are the 

exceptions to this, they can maintain flow 

all year long from source to the sea. Climate 

change models predict changes in rainfall over 

the coming decades for the west of Ireland 

and this will impact on these two rivers and 

may lead to an increased risk of flooding. 

For the most part, this rainfall ends up flowing 

down the cracks in the limestone and disappearing 

underground and surface water is very scarce here.’ 

We have recently started a project to look at 

this in more detail. The Aille Engaged project 

is a community citizen science project between 

the Geopark, Earth and Ocean Sciences, NUIG 

and the Lisdoonvarna Historical Society with 

financial support from Geological Survey Ireland. 

The citizen scientists collect daily rainfall 

and river level data for the Aille River 

catchment and input that data directly 

onto our website where it is displayed: 

www.burrengeopark.ie/learn-engage/rainfall-riverlevel-data/ 

The Aille River is a complex river system that has 

two distinct sources that combine at the Spa Wells 

in Lisdoonvarna. From the north we get the rain 

that falls over Slieve Elva and Poulacapple; most of 

this water enters limestone cave systems, emerges 

at Killeany spring, decides to go underground 

for a while again and then finally becomes the 

Gowlaun River just outside Lisdoonvarna town. 

The other branch, the Aille River, spends all its 

time as an overground river flowing over shale. 

Ultimately, the combined waters flow all the way to 

the sea at Doolin, well almost; when not in flood, the 

river decides to go back into the limestone again just 

before entering the sea, mirroring its initial descent 

into the underground on the slope of Slieve Elva. 

Figuring out exactly where all the rain that falls 

in the Burren ends up may take some time. 




The Burren and Cliffs of Moher 

UNESCO Global Geopark designation. 

On 17th November 2015, the 195 member states of 

UNESCO ratified the creation of a new label, the 

UNESCO Global Geoparks, under the International 

Geoscience and Geoparks Programme. This 

expressed global governmental recognition of the 

importance of managing outstanding geological 

sites and landscapes in a holistic manner. This 

new designation is of equal standing to the 

longer established UNESCO World Heritage 

Site Programme, and the UNESCO Man and the 

Biosphere Programme. On that date the Burren and 

Cliffs of Moher achieved UNESCO designation. 

While the importance of archaeological and 

ecological sites to the cultural and environmental 

consciousness of humans have long been recognized, 

this designation recognized the significance of 

the geological history of Earth, which underlies 

every aspect of life on Earth, for the first time. 

Managed by Clare County Council with support 

from Geological Survey Ireland, the Burren 

and Cliffs of Moher UNESCO Global Geopark 

is now part of a growing global network of 

169 Geoparks across 44 countries. There are 

currently two other UNESCO Global Geoparks 

in Ireland, the cross-border Cuilcagh Lakelands 

Geopark (Cavan/Fermanagh) and the Copper 

Coast Geopark in Waterford, a number of other 

locations such as Mourne Gullion in County 

Down and Joyce Country and Western Lakes 

in Galway/Mayo are or will be applying for 

UNESCO Global Geopark status in the near future. 

We are fortunate to have two outstanding and 

significant geological locations, the Burren and 

the Cliffs of Moher, side by side in north Clare 

(which make us the envy of many other parts 

of Ireland). we are equally fortunate in having a 

network of local businesses as well as schools and 

community groups that appreciate the significance 

of the geological landscape, as well as the floral, 

archaeological and cultural heritage of the area. 

The global governmental recognition of the 

importance of geological heritage is in part, related 

to the increased awareness of the significance of 

climate change and the realization that geology 

records how the Earth has responded to climate 

change in the past. By understanding this we 

can better assess the possible outcomes and also 

educate our population on the changing Earth. 

Within the Burren limestone there are thin 

layers of shale, barely noticeable, that tell us that 

sea-level was fluctuating 330 million years ago, 

related to ancient major global ice ages. In the 

sandstone layers of the Cliffs of Moher we see 

evidence for monsoonal storms and floods in 

rivers that transported vast quantities of mud 

and fine sand into a sea, changing it forever. 

The visitors we invite here come here largely 

because of these two impressive geological 

sites. Working with the Burren Ecotourism 

Network we have created a Code of Practice for 

sustainable tourism businesses, working with 

over 60 local businesses to ensure a sustainable 

future and continued employment by setting and 

maintaining the highest international standards. 

The UNESCO Global Geopark designation 

is a globally recognized quality brand 

that visitors trust. Our goal is to keep that 

designation and we are already preparing 

for our next revalidation visit in 2023. 




Our Fossil Roots 

In sandstone rocks along the wild Atlantic coast 

of west Clare we find excellent examples of a fossil 

called Stigmaria. These are elongate, cylindrical 

or flattened structures with a surface covered 

in regularly arranged dimples. First recognized 

as fossils in the early 1800’s the name Stigmaria 

was introduced for them in 1822 by the eminent 

French palaeontologist Alexandre Brogniart. 

If you come across a Stigmaria or any other 

fossil, please remember that these fossils are a 

non-renewable resource and just take a photo. 

At first these fossils were thought to be plant 

trunks or branches, but the discovery of fine 

rootlets attached to them made it clear they were 

roots. In fact, the name Stigmaria refers to the 

dimples, which are the scars (as in ‘stigmata’) 

of rootlets that extended from the main root. 

This is important because roots grow in soil and 

fossil roots with rootlets still attached means the 

fossil is in a fossil soil, which indicates land. So, 

at that moment in time we were above sea-level. 

Stigmaria is a general term for the roots of 

a number of different fossil plants known as 

‘Lycopods’ or ‘scale trees’. The most common are 

called Lepidodendron and Sigillaria. They were very 

abundant during the later part of Carboniferous 

times from 320-300 million years ago and were 

the early equivalent of trees, although they are 

more closely related to modern clubmosses. Unlike 

modern clubmosses which are small plants, the 

early lycopods were tall, sometimes reaching 30m 

in height and they therefore needed substantial 

root systems for support. Stigmaria can be long, 

regularly over a metre long and specimens over 6m 

long are known from similar aged rocks in the USA. 



Stigmaria was a shallow, horizontal, branching root 

system. Extending from the main trunk the roots 

branched dichotomously, that is they branched, 

bifurcating evenly in two. Much finer rootlets 

extended perpendicularly from the main root. 

This horizontal root system is thought to be an 

adaptation for growing in wet, swampy conditions 

and they are most often found associated with 

coal horizons. Coal horizons accumulated in 

swamps where the acidic, boggy conditions 

encouraged the preservation of the plant material. 

These abundant plants were significant because 

of the impact they had on the climate 300 million 

years ago. Like now, plants release oxygen 

and absorb carbon dioxide. It is thought that 

during the Carboniferous period, forests of 

these lycopods contributed to global cooling by 

absorbing CO2 from the atmosphere, storing 

the carbon in the plant tissues and then having 

that stored in the swamps and bogs after they 

died, thus removing the carbon from the system. 

300 million years later during the industrial 

revolution we started burning that preserved 

plant material (coal) in large quantities and 

very quickly transferred that carbon dioxide 

straight back into the atmosphere where it started 

to trap heat, and so global warming began. 

So, these fossils tell us not only the lie of the 

land of West Clare 300 million years ago but 

also are a reminder of how our actions in 

using Earth’s resources have consequences. 


Erratic Rocks 

A notable feature of the exposed rock of the 

Burren are the large boulders that sit on top of 

the limestone. Some of the best examples are seen 

along the coast road between Ballyrean and Black 

Head or Rock Forest near Mullaghmore. These are 

called ‘glacial erratics’ and they were transported to 

their present position by large ice sheets that moved 

across Ireland during the last period of glaciation 

which was at its maximum about 22,000 years ago. 

Boulders such as this are known from across 

northern Europe and North America and during 

the 17th Century they were originally thought to be 

evidence of the Great Flood. It wasn’t until the 19th 

Century that the idea that major glaciations in the 

past had shaped the Earth’s surface became accepted 

thanks to publications by eminent geologists such 

as Charles Lyell’s Principles of Geology in 1830. 

The name comes from the Greek word ‘errare’ 

meaning to wander. The term is applied to rocks 

that have been carried some distance from their 

original outcrop. We have some excellent examples 

of large granite boulders that have come from 

across Galway Bay. There are no outrops of Galway 

Granite in the Burren so the boulders must have 

been transported here. The vast majority of our 

erratic boulders are limestone and local to the 

Burren, so the transport distances aren’t huge. 

One of the useful features of erratics is that 

they can tell us the direction that the ice flowed, 

so we know that the Galway granite boulders 

were carried south to the Burren by ice sheets 

flowing from Connemara. In southern County 

Clare at the Bridges of Ross we have erratics that 

were carried there from County Kerry whereas 

in eastern Clare we find erratics carried from 

the Slieve Aughty mountains. This tells us that 

local ice sheet flow spread out from regional 

upland areas and that while the overall flow 

of the main ice sheets in Ireland was from the 

northeast, the local pattern can be more complex. 

While currently these boulders stand proud and 

exposed it is possible that they were once part 

of glacial Boulder Clay deposits (a mixture of 

boulders and ground up rock clay) which have lost 

all the finer material due to erosion. The amount of 

Boulder Clay that has been eroded, the erosional 

processes involved or when that erosion happened 

has yet to be established. Some boulders are split in 

half or thirds, this is most likely due to the action 

of freeze-thaw processes in the periglacial period 

after the rock was deposited when severe seasonal 

freezing and thawing would have been common. 

More recently, these erratics can be used to 

establish when the last ice sheets melted. Dr. 

Gordon Bromley, a glaciologist from NUI Galway 

is currently studying our Buren erratics. By 

calculating when these boulders were last exposed 

to cosmic radiation, it is possible to estimate when 

they were exposed after the last ice sheets melted. 

For an alternative and thoroughly entertaining 

story about how the Burren got covered in boulders 

I can recommend Eddie Lenihan’s book ‘Irish Tales 

of Mystery and Magic’ published by Mercier Press. 




Biokarst coastline, near Doolin. Inset shows smooth circular pits made by sea urchins and within those are even smaller 

pits and burrows made by boring sponges (fine network of burrows) and bivalves (isolated burrows). 

How small creatures help shape our coast. 

Our coastal cliffs form a line of defence against a 

constant marine onslaught. From Black Head to 

Doolin the Burren limestone meets the sea and 

from Doolin and the Cliffs of Moher to Loop 

Head our sandstones and shales from a formidable 

barrier. They are greeted with a barrage of Atlantic 

storms. The strength of these storms is such 

that the impact of the waves can be detected by 

the seismometer at the Cliffs of Moher Visitor 

Centre that is designed to detect Earthquakes on 

the other side of the world. These storm events 

cause coastal erosion during which boulders 

the size of cars are routinely thrown around. 

For much of the year however, the coast is a 

pleasant place to live for humans and sea creatures 

alike. Along our coast a community of creatures 

live on the rocks that are submerged and exposed 

twice a day by tides. This is the place where 

we find the rock pools that give us a glimpse 

into life beneath the waves. Here you will find 

sea urchins, limpets, anemones, periwinkles, 

mussels, crabs, starfish, algae and so much more. 

All these creatures affect the rock they live on; 

some scape the surface while grazing on marine 

algae, eroding tiny bits of rock in the process, 

others bore holes into the rock and live in rock 

burrows, grinding or dissolving the rock to make 

their protective shelters and generating very fine 

rock dust which forms mud. While each one 

has very little effect, together they form pits and 

hollows which get deeper and wider over time. 

This makes the limestone weaker, so when storms 

arrive, waves and any rocks they throw around 

can break off chunks of the weakened rock. 

Once the storm has passed, the creatures begin 

again, boring, scraping and dissolving for food 

and protection. The erosional holes and hollows 

they make in the rock are known as ‘biokarst’. 

Studies from the northern Clare coast have 

estimated that sea urchins and boring bivalves 

can remove up to about 1cm of limestone each 

year to form the rounded pits they live in. 

That is one metre in one hundred years. This 

is all part of the rock cycle whereby rocks and 

fossils that formed over 300 million years ago 

are being recycled into the sea as fine mud. 

The wooden ships of the Spanish Armada 

in 1588 are thought to have been infested by 

wood-boring bivalve molluscs. This would 

have weakened the hulls and made them more 

susceptible to breaking up when they struck 

the bored and burrowed rocky Irish west coast. 

Ignore the little guys at your peril! 




Shell ornament on one of the extinct fossil ammonoids found in the rocks of west Clare. 

Mass Extinctions 

The spectacular end of most dinosaurs around 

65 million years ago due to the impact of a large 

asteroid is now widely accepted by scientists and 

even a possible site of the impact, off the Yucatan 

Peninsula of Mexico, has been identified. Around 

65% of species on Earth at that time were killed 

off, although it is worth remembering that birds, 

direct descendants of the avian dinosaurs, and 

more importantly for us, mammals did survive. 

A long time before that, around 250 million 

years ago there was an even more extreme mass 

extinction when over 80% of all species were 

eradicated. The extent and causes of this event 

are still debated by scientists and may involve 

another asteroid as well as huge volcanic eruptions. 

Three other large mass extinction events are 

known in the last 500 million years of Earth’s 

history: The end of the Ordovician Period (440 

million years ago), the end of the Devonian 

Period (360 million years ago) and the end 

of the Triassic Period (200 million years ago) 

the change of rocks from limestone to sandstone 

and shale. This extinction event is attributed 

to changes in climate resulting from the start 

of an ice age. This caused changes in sea level, 

sedimentation and temperature and some species 

were not able to adjust to the new conditions. 

Ammonoids, crinoids, conodonts, brachiopods, 

foraminifers and corals were all affected. So 

as you travel from Black Head to the Cliffs of 

Moher or from Corrofin to Ennistymon you are 

passing over one of Earth’s mass extinction events. 

More recently, many writers are describing a mass 

extinction event unfolding on the Earth right now. 

A large part of the current mass extinction can be 

directly related to the activities of humans due to 

deforestation and habitat loss on land. Coupled 

with the effects of global warming, in particular 

ocean acidification, other effects including the 

loss of many marine creatures are inevitable if 

current trends continue. Ultimately, if enough of 

the ecosystem of the Earth collapses, we could 

be willingly participating in our own extinction. 

A sixth event, known as the mid-Carboniferous 

event (330 million years ago), is also recognized, 

and while this wasn’t quite on the same scale as the 

other ‘big five’ extinctions, many creatures globally 

suffered a serious decline and it is estimated 

that around 30% of species were lost at this time. 

This extinction event is marked in the Burren in 



While we like to think that we as humans will 

leave a long-lasting legacy on Earth, the processes 

of weathering, erosion and plate tectonics would 

continue after we are gone and in a relatively short 

geological time, there would be virtually zero 

trace of our existence in the geological record. 


Lough Garrig on top of Sleive Elva 

The smallest Lake in Ireland is in the 

Burren 

Sitting on top of Slieve Elva at an elevation of 

almost 330m is a tiny pond of water called Lough 

Garrig. Only a couple of metres across, it is barely 

noticeable in the broad bog that covers the highest 

upland in the Burren. The lake has been marked unnamed 

on maps since the acclaimed 1842 Ordnance 

Survey 6 inch maps. The name Lough Garrig first 

appears on the 25 inch Ordnance Survey maps 

(1888-1913). I have not been able to discover yet 

why it was named, why this insignificant pool of 

water warranted a name, title, recognition on a map. 

And yet, it is significant. 

Bogs have been very useful to us in Ireland 

over the last few hundred years, primarily as 

a local source of fuel and more recently as a 

source of organic soil for our gardens and potted 

plants. Before that the iron (bog iron) beneath 

the bog was used for the forging of iron tools. 

Today our bogs are universally recognized 

as carbon ‘sinks’ or reservoirs, that is, places 

where carbon is stored on the Earth’s surface 

so it doesn’t end up as carbon dioxide in the 

atmosphere. This is important, but bogs can 

only act as carbon sinks if they can continue to 

store water. The noted and notable presence of 



Lough Garrig on top of Slieve Elva from over 

150 years ago to today indicates a hydrological 

stability, it means the bog is consistently able 

to store water and it acts as a not just a carbon 

reservoir but an important water reservoir as well. 

When rain falls in the Burren some of it falls on the 

limestone and it quickly disappears underground. 

When rain falls on the bog a lot of it is held there 

by the bog. The rain is held by the bog acting like a 

huge sponge. If it is full, then water will flow off the 

surface very quickly, however once the rain stops 

the bog will release the water it is holding very 

slowly over many months, supplying numerous 

streams that in turn flow into rivers or caves. 

If it wasn’t for the bog on top of Slieve Elva than all 

of the streams that flow off the hill, the streams that 

supply water to local houses and farms, the streams 

that provide water to the Aille river and the sea 

and the invertebrates and fish that live there, would 

be dry in a matter of days in summer or any dry 

period. The bog is an important reservoir and the 

diminutive Lough Garrig may be the smallest lake 

in Ireland, but rather than celebrating it for its size, 

we should celebrate it as an important part of that 

water reservoir and the hydrology of the Burren. 

I hope it is still on maps in another 150 years. 


Fossil Wind 

Ancient ripples formed by wind waves on a 

shallow coast 315 million years ago. 

There are three main rock types; Igneous rocks 

which are formed from molten magma from the 

Earth’s interior that has cooled, Sedimentary rocks 

which are formed from particles (sediments); bits 

and pieces of rocks and fossils and Metamorphic 

rocks which are any rock that has been deformed 

by deep burial and the forces of plate tectonics. 

The rocks of the Burren are sedimentary rocks. 

At the Cliffs of Moher, the layers are made of 

particles of sand and mud and occasionally bits of 

fossils. These particles were transported by rivers 

from long-gone distant mountains and finally 

deposited into the sea. After they were buried by 

more and more sediment they were eventually 

turned into rock. So, while the sand and mud 

and bits of land plants often ended up in the sea, 

they were transported considerable distances 

from where they were originally eroded on land. 

As these bits of eroded land entered the sea, they 

were sometimes buried beside sea creatures that 

were living in the sea at that time. So, we often find 

land and sea creatures preserved together there. 

The limestone of the Burren is also a sedimentary 

rock, but limestone is a bit different. The particles 

that make up limestone are often dominated by 

fossils or fragments of fossils. They haven’t been 

transported by rivers and are usually turned 

into rock close to where they lived. All the 

fossils in the Burren limestone are sea creatures 

and lived and died in a shallow tropical sea. 

Here the process of turning into rock is quicker 

as the tropical seas are very rich in calcium 

carbonate which crystalizes out to form the 

cement that holds all the bits of fossils together. 

This can happen very shortly after the creatures 

died and they don’t need to be buried deeply. 

The processes that act on the particles of sand, 

mud or fossils while they are on the seafloor can 

tell us a lot about where exactly they were, and 

this is one way we get to understand what was 

happening over 300 million years ago. One of 

those processes is wave action produced by wind. 

When wind blows across a body of water it can 

generate a circular motion in the water, these 

circular cells of water decrease in size the deeper 

you go in the water until at a certain depth they 

disappear. If the water is shallow enough, those 

circular cells will impact the sea floor creating a 

back-and-forth motion that can move the loose 

sand on the seafloor. This back-and-forth motion 

creates wave ripples. If these are buried by another 

layer of sand, they may be preserved as fossil 

ripples. They are, in effect, fossilized wind energy. 

These ripples, which can be seen along the 

walls of the path along the Cliffs of Moher have 

been quarried locally. We know how important 

waves are to local surfing and energy generation 

now, they have been important to whoever 

was living here for over 300 million years. 




A clay layer between two layers of limestone is a record of an ancient ice age in the rocks of the Burren. 

Geological Climate Change 

When we talk about Climate Change what we are 

really talking about is Anthropogenic Climate 

Change, that is, the effect human activities are 

having on global climate. The increased levels 

of carbon dioxide in the atmosphere due to the 

effects of burning coal and oil, the methane output 

from huge herds of livestock and the nitrous oxide 

from excessive use of artificial fertilizers are wellknown 

examples of human-induced emissions 

that are contributing to the rapid global rise in 

temperature. Although we are doing it more 

quickly, we are not the first to do it; here are some 

examples of how other organisms on Earth have 

caused Climate Change in the geological past. 

From the very first beginnings of life on Earth the 

organisms that live here have had a direct impact on 

the climate. As early as 3.5 billion years ago, the first 

cyanobacteria (blue-green algae) were converting 

the water and carbon dioxide in the atmosphere 

into oxygen. This early oxygen was mostly 

absorbed into rocks but after a billion years or so, 

oxygen began accumulating in our atmosphere. 

These simple organisms transformed our 

atmosphere. They caused global Climate Change. 

Much later, around 470 million years ago another 

new group of organisms, the land plants, evolved. 

These plants started taking carbon dioxide from 

the atmosphere and releasing oxygen while their 

roots contributed to breaking up rock which then 

absorbed carbon dioxide as well. Very slowly over 

time (35 million years) this resulted in a significant 

decrease in the amount of carbon dioxide levels 

in the atmosphere and there is evidence that the 

reduction in carbon dioxide resulted in a significant 

global cooling which triggered an ice age. 

This process was repeated 100 million years later 

when large forests evolved, again the effect was 

to absorb carbon dioxide from the atmosphere, 

and again the result was to significantly cool 

the planet, resulting in another long-lasting 

ice age. In this case however, the carbon was 

stored in bogs and swamps when the plants 

died. This meant that the carbon was extracted 

from the atmosphere and stored on land. 

Eventually this plant carbon was turned to coal. 

Since the 17th century we have been reversing that 

process by taking that coal (and more recently oil 

and gas) and burning it and returning that carbon 

to the atmosphere as carbon dioxide. That is the 

main reason we are now warming the planet. 

When these first forests were forming, the rocks 

in the Burren were forming, and we see evidence 

of the global ice age. The ice sheets that formed on 

the South Pole absorbed so much water that sealevel 

fell globally. We can see that in the Burren 

limestone, when sea level dropped the limestone 

on the sea floor became land, was exposed to 

weathering and soils formed. As the ice melted 

those soils were then buried by the rising sea level 

and preserved within the rocks of the Burren. 

We are just the latest organism on Earth to 

significantly change our atmosphere, the difference 

this time is that we change what that impact is. 




Coral Conundrum 

Fossil corals are quite common in the limestone of the 

Burren. They can be easily seen around the Flaggy Shore 

and the walking trails at Mullaghmore in the Burren 

National Park. They were alive and thriving about 330 

million years ago when the area that has become the 

Burren was over 5,000 km away, near the equator. They 

were living in a shallow tropical sea similar to the sea 

around the Bahamas today. It would have been great for 

snorkeling. 

These corals belong to two groups; the Rugosa and the 

Tabulata and they went extinct during one of the largest 

mass extinctions in geological history at the end of the 

Permian period about 250 million years ago. Modern 

corals belong to a different group; the Scleractinia and 

they appeared after the mass extinction about 240 million 

years ago. Although they are superficially similar to the 

Rugosa, they are quite different in how they build the 

structure of their skeleton, and they use a different form 

of calcium carbonate to build it. They are best described 

as ‘distant cousins’. 

Modern corals belong to two broad groups, those that 

live in shallow, warm water (and make such massive 

structures as the Great Barrier Reef, Australia) and those 

that live in deep, cold water and do not form reefs (we 

have important communities of these off the coast of 

Ireland). However, despite the undoubted importance of 

these modern corals to our marine environment, we don’t 

know where they came. 

The question is, did modern corals evolve from a few 

of the rugosa corals that survived the mass extinction 

event or did they have much older ancestors? Were 

the scleractinia already around, well before the mass 

extinction and only came to prominence once all the 

other corals had been wiped out? 

It is generally considered unlikely that a whole new form 

of complex coral with different internal structure and 

composition could have evolved so quickly after the mass 

extinction. 

There have been a couple of fossil corals discovered 

in much older rocks (470 million years old) that have 

internal structures very similar to modern corals. 

However, because there is such a long time gap (over 200 

million years) until we see the next modern corals after 

the mass extinction, palaeontologists had thought that 

these very old forms were an early evolutionary anomaly 

that only briefly existed. 

One way to identify the real ancestors of modern 

corals would be to find some in rocks that bridge the 

200-million-year gap. The rocks of the Burren fall into 

that age and so when I am out and about looking for 

fossils, I keep a very close eye out for any slightly different 

looking fossil corals that may provide an answer to the 

conundrum of the origin of modern corals. 

Figure caption: Examples of extinct Rugosa (left) and Tabulata (right) fossil corals in the Burren limestone.

Big Brachiopods 

Large brachiopods are quite common in the limestone 

of the Burren. They can be seen in walls and loose rocks 

and in the rock of the limestone pavement that we so 

enjoy walking over. They were alive and thriving about 

330 million years ago when the area that has become 

the Burren was over 5,000 km away, near the equator. 

The large brachiopods that are found in the Burren are 

called Gigantoproductus, not because they are gigantic 

but because they are relatively large compared to most 

other brachiopods, living or fossil. There are other fossil 

brachiopods in the limestone of the Burren, but the big 

brachiopod Gigantoproductus is the one you are most 

likely to see. 

Brachiopods look like bivalves such as scallops or cockles 

(which are types of mollusc) because they have two 

opposing shells that they can open and close, however 

internally they are very different because brachiopods 

have a feeding structure known as a lophophore, which 

is different to the gill system used by bivalve molluscs. 

Brachiopods evolved at the same time as bivalve molluscs 

around 530 million years ago when many creatures first 

started making protective calcareous shells for themselves 

and thousands of species have evolved since then. 

Brachiopods are alive and well and living in all the worlds 

oceans today, however you are unlikely to have come 

across one unless you scuba dive, as they are small and 

live in deep seas with little light. Today they are hugely 

outnumbered by their bivalve mollusc cousins which are 

easy to find as they are common in shallow water and 

can be found along any coast. That wasn’t always so, in 

the past, brachiopods dominated the seas; during the 

Carboniferous Period, 330 million years ago they would 

have been much more abundant than bivalves. However, 

they were decimated by the Permian mass extinction 

250 million years ago. Their slower metabolism likely 

hindered their recovery and bivalve molluscs took the 

opportunity to take over ecological niches left vacant by 

the extinct brachiopods. 

It is interesting to think that when the limestone in the 

Burren is dissolved by rain, the fossil brachiopods in the 

limestone are also dissolved and washed into the sea. 

The calcium and bicarbonate ions then become available 

for living brachiopods (and other shelled creatures) to 

extract from the water to make their shells today. Some 

of these new brachiopod shells will in turn be buried and 

preserved as fossils. This is an example of the Rock Cycle. 

However, a warning is required; if global warming 

continues and ocean acidification continues the chemistry 

of the oceans will change so that it will be impossible for 

the shelled creatures in the sea to make their shells and we 

will have created another mass extinction. 

Figure caption: Fossil brachiopods from the Burren. Shell exterior of a single shell on the left, cross-section through 3 complete brachiopods on 

the right.

Fossil crinoids – finding the ‘new’ in 

the old 

The limestone of the Burren is packed with fossils. It is 

reasonable to say it is made of fossils. A lot of the time 

we don’t see them because the surface of the limestone 

is covered by algae or lichen but just below the surface 

lie the remains of animals that lived in a tropical shallow 

sea, 330 million years ago. And of all the fossils in the 

limestone, bits of fossil crinoids are the most abundant. 

Crinoids come in a variety of forms, the most typical 

being a long narrow stem, with a globular body or ‘calyx’ 

on top and multiple long feathery-looking arms extending 

upwards from that. They look a bit like ferns and are 

also known as ‘sea-lilies’ or ‘feather stars’. Crinoids were 

abundant in the Carboniferous shallow seas and they are 

still found in the world’s oceans today although generally 

in deeper water, so they are rarely seen. Crinoids belong 

to the echinoderms, so they are closely related to sea 

urchins, sand dollars, starfish and even sea cucumbers. 

Like many sea creatures, crinoids make their hard parts 

out of the mineral calcite. It is the hard parts that survive 

to become fossils. For crinoids, their hard parts are a 

series of discs stacked on top of each other that make up 

the skeleton of the stem and arms of the animal. During 

life, these are attached together by ligaments giving the 

animal a degree of flexibility to wave around in ocean 

currents, where they use their arms to collect food from 

the water. 

Unfortunately, most fossil crinoids in the Burren 

limestone are not complete, they were separated into 

their individual pieces shortly after they died, when the 

connecting tissues had decomposed or were eaten. These 

pieces of crinoid were then moved around on the seafloor 

by waves and currents and broken up even further by 

burrowing organisms or scavengers before being buried 

and turned to rock. These individual circular sections of 

stem are known as ‘ossicles’ and vary in size from 1mm 

to about 20mm in diameter. When alive, the stems can 

be over 1m long but after death they break up, however, 

sometimes short sections of stem survive intact. While 

finding a complete fossil crinoid in the Burren is unlikely, 

because each crinoid has hundreds of individual pieces, 

this means there are a lot of crinoid pieces to be found. 

When palaeontologists find ‘new’ species, they are of 

course finding old fossils and just giving them a new 

name. My Geopark research with Dr. Steve Donovan on 

fossil crinoids has already identified a ‘new’ 326 million 

year old species (Heloambocolumnus harperi) from 

Doolin, a crinoid unknown anywhere else in the world. 

As I find more specimens, this ‘new’ material should 

provide even more ‘new’ fossil discoveries in the coming 

years. 

Figure caption: Fossil crinoids from the Burren. Left, fossil crinoid ossicle unique to Doolin; centre, typical preservation of crinoid bits; right, 

short section of intact stem.

Our Geological Connection with 

Ukraine 

Here in the Burren, we are forging new, unexpected 

connections, with Ukraine. However, we also have a 

much older connection, through the rocks and fossils 

of both places. We have been part of the same tectonic 

plate as Ukraine for the last 400 million years and have 

a shared journey through geological time. Ukraine has 

a huge diversity or rocks; from some of the oldest rocks 

in the world that are dated at 3.75 billion years old (just 

over a billion years after the formation of the Earth!), to 

relatively young rocks of just a few million years old and a 

selection of almost everything in between. 

One part of Ukraine is of particular interest to us as it 

has Carboniferous-aged rocks, which also extend into 

western Russia. These rocks are the same age (340-310 

million years old) as the rocks in the Burren and Cliffs of 

Moher. Not only are the rocks the same age, they are also 

the same type (limestone covered by sandstone and shale) 

and while their rock sequences are considerably thicker, a 

visiting geologist would immediately see the similarities. 

They even have some of the same fossils. 

In their limestone they have the fossil coral 

Siphonodendron, which is also found here. They also 

have similar fossil brachiopods and crinoids. These 

sea creatures would have lived in very similar shallow 

tropical seas before being turned into fossils. Overlying 

the limestone, they have thick layers of sandstone and 

shale, just like the rocks in the Cliffs of Moher. In both 

places these rocks were formed from sediment carried 

by large rivers into a sea where they formed deltas with 

thin sandy layers that eventually turned into rock. The 

rocks preserve the same type of fossil plant material such 

as Lepidodendron, as we find here and they also have 

goniatites (fossil ammonoids) that are very similar to 

ours. 

The geology of Ukraine also has some other fascinating 

fossils that we do not find here. In their Ediacaran rocks 

older than 550 million years, there is evidence for very 

early life forms of soft-bodied creatures. In their younger 

rocks (about 45 million years old) they also have some 

fossil reptiles, including crocodiles and even a fossil 

leatherback sea turtle as well as fossil birds! 

In another geological similarity with the Burren, Ukraine 

has extensive development of caves. However, they 

formed differently to ours, from thick deposits of gypsum 

(similar to that found in County Monaghan) and as 

gypsum is even more soluble in water than limestone, this 

has led to extensive cave development, similar to what 

we see in the Burren limestone. One gypsum cave system 

discovered in Ukraine in 1966 has over 265 kilometers 

of cave passages! Our own Aillwee and Doolin caves are 

much more manageable. 

The blue area marks the Carboniferous rocks in Ukraine that are the same as the rocks we have in the Burren.

The rocks of the Cliffs of Moher 

As the tourist season starts to accelerate, one of the most 

popular visitor locations will be the Cliffs of Moher. All 

visitors will experience a variety of feelings and emotions 

as they gaze out over the world-renowned cliffs. It is 

worth reminding ourselves about the geology they are 

looking at. 

All the rocks in the Cliffs of Moher started out as mud, 

sand, and silt around 320 million years ago. These 

sediments were eroded by rivers from a huge mountain 

range that extended along the equator, south of where 

we were located at that time. Like the modern Ganges or 

Brahmaputra rivers, they were fed by monsoonal rains 

and carried a lot of sediment to the sea where it was 

deposited as a delta. 

When rivers carry sediment to the sea, the coarser sand is 

deposited first, right at the shore, but the finer mud can be 

transported huge distances offshore before it finally settles 

to the seafloor. As the sediment keeps being deposited, the 

sheer volume of it can form new land as it builds outwards 

into the sea. So, if you were standing on the seafloor (for 

a very long time) far out to sea, you would initially see a 

lot of mud accumulating around you. However, over time 

you would be buried by increasingly coarser sediment as 

the shoreline got closer to you. Eventually it would fill the 

sea, land would appear, and plants would then colonize 

that land. 

Then imagine that sea-level rose and you were inundated 

again. As long as the rivers keep flowing the process 

would repeat itself and the sequence from mud to sand 

would be repeated in successive layers as the sediment 

filled the sea again. If sea-level then dropped, the coastline 

would move offshore and there would be erosion of the 

coastal area until a new equilibrium was reached. 

This interaction between fluctuating sea-level, monsoonal 

rains and large rivers is what happened 6,000 kilometres 

away and 320 million years ago to form the layers of sand 

and mud that became the sandstone and shale of the Cliffs 

of Moher. The changes in sea-level were caused by an 

ancient ice age that was happening at that time. 

The layers of sandstone are slightly harder than the rest of 

the cliff face, which is made of softer shale and siltstone. 

The softer layers get eroded by wind and waves, leaving 

the sandstone ledges slightly overhanging. These ledges 

are ideal nesting sites for the incredible bird population 

that returns here every year, an amazing sight for the 

visitors who also return every year. 

The rocks of Cliffs of Moher are a record of the changing 

patterns of sedimentation in an ancient delta that formed 

320 million years ago, over 100 million years before the 

first birds had evolved and 320 million years before the 

first tourist. 

Figure caption: The layers of sandstone and shale of the Cliffs of Moher.

The corals of the Burren National Park 

The Burren National Park is located on the ancient Burren 

limestone bedrock. As you approach Mullaghmore you 

will notice that the layers in the limestone are gently 

buckled, the result of plate tectonic collisions almost 300 

million years ago, more than 30 million years after the 

rocks were formed in a shallow tropical sea. 

The limestone in the Burren is rich in fossils, although 

they can be difficult to see sometimes. Along the main 

walking trail that ascends to the top of Mullaghmore 

there are some wonderful examples of colonial corals. 

Some of these corals are more than one metre in diameter. 

The corals stand out because they are darker than the 

surrounding limestone. 

They also literally ‘stand out’ as they protrude slightly 

above the limestone surface. 

The corals are called colonial corals because they are 

colonies of individual animals not because of any 

geopolitical history! 

These colonies are formed of clustered branches of the 

coral structure. This structure is the rigid framework that 

physically supported the soft creatures known as ‘polyps’ 

that lived there. An individual polyp would have lived at 

the end of each branch. Each polyp in a colony was an 

individual creature, but they were actually clones of each 

other, so would have been genetically identical. 

Corals make their hard structures from the white mineral 

calcite (CaCO3), which they extract from sea water. 

The fossil corals along the walking trail in the Burren 

National Park were originally calcite too, however the 

minerals have since been changed. The corals are now 

predominantly silica (SiO2), and silica doesn’t dissolve 

as easily as calcite, which is why they stand proud of the 

limestone surface. 

It is common for minerals to be replaced by other 

minerals over geological time. This process of change is 

known as ‘diagenesis’, and it is controlled by temperature, 

pressure and chemistry changes that take place as rocks 

get buried deeper below the surface. The question is, 

where did the silica come from? 

There were many possible sources of silica. Some 

creatures which may have been living with the corals, 

such as sponges and radiolaria, extracted silica from 

seawater to make their rigid structures, so their skeletons 

could have supplied the silica. The silica could also have 

come from wind-blown dust blown into the sea, similar to 

modern Saharan dust storms. Another source could have 

been mineral veins which were injected into the limestone 

during the tectonic collision that formed the buckling of 

Mullaghmore. It is also possible that freshwater flowing 

into the sea could have brought in silica, in much the 

same way that offshore springs around the Burren 

transport minerals from land to sea. Whatever the source, 

once buried, that silica dissolved and migrated and found 

a new home, in the corals of the Burren National Park. 

The corals are wonderful examples of colonial organisms 

but also highlight the complex paths that lead to the 

preservation of fossils as we see them today. 

Figure caption: Colonial coral replaced by silica in the Burren National Park.

The significance of Slieve Elva. 

At 344m above sea-level, Slieve Elva (Sliabh Eilbhe) is 

the highest point in the Burren region. As a landscape 

feature it records the past, influences the present and will 

contribute to the future Burren landscape. 

Slieve Elva is surrounded by limestone on its western, 

eastern, and northern slopes but the top is not limestone, 

it is mostly shale with some layers of sandstone, which are 

largely covered by a bog. These are the same shales and 

sandstones that stretch south to form the cliffs at Doolin 

and the Cliffs of Moher. The change from limestone to 

shale is abrupt and we know from fossils that there is a 

time gap (a few million years) between the last limestone 

being formed and the first shale being formed. We are 

not exactly sure what happened during that missing time 

period. 

The sandstones and shales that make the top of Slieve 

Elva are a just remnant of what would have covered all 

of the Burren millions of years ago. Erosion by rivers, 

and then ice, has removed these rock layers, exposing the 

limestone underneath. Once exposed, the limestone is 

then subject to the influence of rainwater which dissolves 

the limestone. This is demonstrated particularly well 

around the flanks of Slieve Elva where a large number of 

sinkholes have developed at the contact between the shale 

and the exposed limestone. This has had a huge impact 

on the Burren over millions of years; the current Burren 

landscape would not have developed if the limestone was 

still buried under sandstone and shale. 

However, it is not just the rocks of Slieve Elva that are 

significant, the bog that caps the mountain has a very 

important influence on water flow in the area. The bog 

acts as a living water storage system that can hold water 

and release it slowly throughout the year. This means that 

the local streams always have water, although they flow 

underground through the limestone for some of their 

journey. One of those streams, the Gowlaun River at 

Lisdoonvarna, is fed directly by water that flows off Slieve 

Elva. If you visit the Spa Wells in Lisdoonvarna after a 

recent rainfall event you will be able to see where the two 

distinctive rivers meet. The clear water of the Gowlaun 

River meets the dark water of the Aille. 

We are currently working with hydrologist Dr. Tiernan 

Henry of NUIG to monitor the water flow and develop a 

better understanding of how the complex river catchment 

works and how it will change based on climate change 

predictions for rainfall changes in the coming years. This 

ties in with the work of Lisdoonvarna citizen scientists in 

the Aille Engaged project who collect daily rainfall and 

river level data. 

Figure caption: The clear water of the Gowlaun River (left) meets the dark water of the Aille River (right) at the Spa Wells.

Conodonts: bizarre fossils in the 

Burren that deserve a mention. 

Imagine a small eel-like creature, anywhere between 1 and 

40cm long with a flattened body that has a small tail fin. 

These little creatures, which are now extinct, once swam 

in the seas that eventually become the rocks of County 

Clare. Nothing too bizarre about that so far, until we get 

to its mouth.. 

The conodont creature didn’t have jaws; the mouth was 

packed with 16-18 different pieces of dental apparatus. 

Some are like tiny teeth, others are like tiny combs. This 

complex apparatus is bilaterally symmetrical, so has a 

distinct left and right side. These pieces, usually between 

0.2 and 5.0 mm long are arranged like the mechanism of 

a fine mechanical watch. It is thought that the animals 

could extend and manipulate this complex toothed 

apparatus to capture prey. The tooth elements are made 

of a durable material called hydroxyapatite; the same 

mineral makes up a good part of our own bones and 

teeth, so we are distantly related! 

Globally, only about a dozen of these creatures have ever 

been found as complete fossils. Some of these have been 

well-preserved. Most of the reconstructions you will see 

on an internet search will show them with large eyes, 

although not everybody agrees that they had large eyes. 

Thanks to those exceptional preservations a lot is now 

known about these creatures, however that wasn’t always 

the case. Usually all we find as fossils are the scattered 

remains of the small individual tooth elements. 

Conodonts were known only from their teeth elements 

for over one hundred years and it wasn’t until the 1980’s 

that the animal they belonged to was discovered with 

the teeth elements intact. However, despite not knowing 

what the animal was, palaeontologists had noticed that 

the details of some of the teeth elements evolved quickly 

and they were being used to age rocks quite successfully. 

Because the teeth are so resilient, blocks of limestone can 

be dissolved by acid and any conodont elements in the 

limestone will remain and can be collected afterwards for 

study. 

Conodonts have also proven themselved very useful in 

a totally different geological context; they change colour 

depending on the maximum temperature they have been 

exposed to, which can tell us how deep the rocks have 

been buried. Recently I found some new conodonts which 

are white, which indicates the rocks here were heated to 

over 350° C at some point in the past. This means that the 

rocks were buried to a depth of at least 3 kilometres. The 

rocks have since been uplifted and eroded over the last 

few hundred million years to get to where they are today. 

Imagine 3,000 metres of rock above the Cliffs of Moher 

now. That is what has been removed. 

So, even when we only find parts of these bizarre little 

conodont fossils, they can still provide a wealth of useful 

information about our geological history. 

Figure caption: One of the tiny (1.5mm) tooth elements of a conodont, recently discovered in the Burren and Cliffs of Moher UNESCO Global 

Geopark.

Cephalopod fossils; underwater 

swimming predators without fins or 

tails. 

Cephalopods are a type of mollusc, so are related to our 

garden snails and slugs as well as the osyters and mussels 

that live along our coast. Cephalopods have existed on 

our planet for over 500 million years and are represented 

in our oceans today by octopus, squid, cuttlefish and the 

iconic coiled-shell Nautilus. 

Cephalopods were more abundant and diverse in the past. 

Many had a shell (unlike modern octopus and squid), 

and over time the shell evolved into a variety of straight, 

curved and spiral forms, incuding some bizarre contorted 

shapes. The most well known fossil cephalopods are 

the coiled ammonites, the spiral shape of which is often 

used as an icon image for fossils or geology; some of the 

ammonites reached over 1m in diameter. 

Cephalopods today are predators; they have good eyesight 

for targeting prey, tentacles for grasping prey and tough 

beaks for biting and ripping apart prey. 320 million years 

ago they were doing the same thing, swimming and 

hunting in the seas that eventually formed the rocks of the 

Burren and Cliffs of Moher. Fortunately, some of them are 

preserved in those rocks as fossils. 

We find two main types of fossil cephalopods in our rocks 

here; thin, conical, straight-shelled forms and tightly 

coiled spiral forms. When these shells are well-preserved 

you can see they have a series of internal chambers, 

the same as in modern Nautilus shells. These chambers 

were connected by a tube which was able to regulate the 

amount of fluid and possibly gas inside the chambers, 

this enabled the cephalopod to adjust it’s position up or 

down in the water column. In addition to this marvelous 

mechanism the cephalopods also deposited layers of 

shell inside the chambers to act as ballast as well as to 

strenghten the shell to protect it from predators.The 

animals actually only inhabited the final open section of 

the shell. 

The cephalopods propel themselves by pumping water 

through a funnel known as a hyponome and squirting it 

out. This acts like jet propulsion and gives them the speed 

to catch their prey or escape predators, many also use an 

ink sac to squirt out clouds of dark ink to confuse their 

predators and remarkably there are fossil examples of 

these ink sacs preserved in exceptional conditions. 

Being skilled hunters, the cephalopods would have been 

close to the top of the food chain. For a long time it was 

thought they were the apex predators here. However, 

these cephalopods were likely preyed upon by larger 

predators such as sharks. I am currently hunting for 

more of these fossils to expand our knowledge of these 

fascinating ancient predators and the intricate web of life 

that existed 320 million years ago. 

Figure caption. Two types of fossil cephalopods from the rocks of the Burren. Both were common here 320 million years ago.

Sedimentary layers: reading the pages 

of geological history. 

The limestone, sandstone and shale rocks of the Burren 

and Cliffs of Moher are all sedimentary rocks, they 

formed by the accumulation of sediment in a longgone 

sea over 300 million years ago. A typical feature of 

sedimentary rocks is the horizontal layering within the 

rocks. To a geologist, these layers are the equivalent of the 

pages of a book, and careful reading can provide a lot of 

information about exactly how the rocks formed. 

Individual sedimentary layers can be as thin as 1mm 

(known as laminations) or several metres thick and are 

often produced by a single event. Typical events include 

storms, floods, tides, avalanches and tsumani. When 

these events move and deposit sediment either on land 

or at sea, the deposited sediments may be preserved by 

being buried by the next event and eventually get turned 

to rock. Some events can produce multiple deposits (and 

therefore multiple layers) at the same time in different 

places. For example, a large storm could produce a lot of 

rainfall on land which would cause a river to flood and 

burst it’s banks. As the flood recedes it can deposit a lot 

of mud on the floodplain. The same river in flood will 

also transport more mud and sand out to sea, some of 

which may be deposited close to the river mouth, forming 

thick sand bars in a delta, while some will be transported 

much further offshore eventually settling to form fine 

laminations on the deep sea floor. 

Sometimes these events (such as storms) are sporadic 

and may only happen once a year, however other events 

such as tidal currents are repeated twice a day and can 

leave distinctive deposits every day. These tidal deposits 

can record the monthly change in conditions from neap 

tides to spring tides, as stronger spring tides will deposit 

thicker, coarser layers than during neap tides. The entire 

sequence will show a monthly cyclical pattern changing 

from coarser to finer, repeated many times. 

Things get complicated when several events happen at 

the same time, for example when a flood happens in a sea 

that has strong tidal currents, in those cases we may get 

alternating layers of different events or mixed deposits 

showing characteristics of both events. 

It has been estimated that at the time our Burren rocks 

were formed, tides were very modest, typically only about 

5 or 10 centimetres, this is because the sea where our 

rocks were forming was shallow and wasn’t directly linked 

to a large ocean. This is quite different to our coast now 

where the Atlantic Ocean can generate huge tides. 

We do have evidence from the Cliffs of Moher that 

annual monsoonal floods caused rivers to transport large 

amounts of sediment into the sea. Some of the fine mud 

was transported offshore and settled in quiet areas to 

produce laminations. So, where we find these laminations 

we can look at a yearly record of sediments from over 300 

million years ago. That is more detailed than most history 

books. 

Figure caption: One of the tiny (1.5mm) tooth elements of a conodont, recently discovered in the Burren and Cliffs of Moher UNESCO Global 

Geopark.

Fossil sponges: shining a light on some 

of our most overlooked fossils. 

Sponges are not the most glamorous things in the world, 

at best they might be delicious cakes or comforting bath 

scrubs, while in our kitchens they are man-made plastic 

porous blocks we use to help clean the dishes. The original 

sponges are living creatures however and most of us don’t 

stop to think about them, so here is a little background to 

the most overlooked creatures in the fossil record. 

These fascinating creatures are alive and well in all our 

seas today (a few live in fresh water), although many 

were in danger of extinction due to overfishing before 

the arrival of synthetic replacements. Sponges are simple 

multi-cellular organisms that don’t have a nervous or 

circulatory system or even a digestive tract. No limbs 

or eyes or teeth either. They have a porous jelly-like 

body that is supported by a network of microscopic 

skeletal elements known as ‘spicules’ that can be straight, 

cross or star-shaped. They draw water in through their 

porous bodies where microrganisms are filtered out and 

processed by the cells for food. 

It has been over 500 million years (half a billion years!) 

since the first sponges appeared and they are thought to 

be one of the earliest animal lineages to have evolved. 

Sponges can be found in all the geological ages from then 

to the present day and they have evolved a wide variety 

of lifestyles. Most are attached to rocks or the seafloor, 

but some can drift in currents; most filter microrganisms 

from the water, but some are predatory and capture prey 

with long sticky threads or hooked spikes; they can vary 

in sze from 1mm to several metres and can live in shallow 

water or down to the deepest ocean floor many kilometers 

below the sea surface. 

Sponges have an extraordinary ability to regenerate 

themselves from fragments. This is important in assuring 

their survival; even if a small part of a sponge survives a 

predator it can grow into a new animal. 

So, do we find fossil sponges in the rocks of the Burren 

and Cliffs of Moher UNESCO Global Geopark? Yes, 

we do, although they are not easy to spot because it is 

usually only the tiny (2mm) spicules that get preserved as 

fossils. This is why they are so overlooked. However, you 

might more easily find some evidence of the sponges that 

currently live along our coast, as some have the ability to 

dissolve limestone and make tiny complex burrows in the 

rock. 

Sponges are an important part of our modern ocean 

ecosystem and they were an equally important part of 

our geological ecosystems in the distant past. Finding 

fossil sponges adds one more piece of information to our 

understanding of our ancient biodiversity. 

Figure caption: A tiny spicule of a fossil sponge (left) recently collected in the Burren and Cliffs of Moher UNESCO Global Geopark and (right) 

modern sponge borings in a Burren limestone pebble.

Oh poop... 

We have quite a wide variety of the remains of once living 

creatures preserved as fossils in the rocks of the Burren 

area. Apart from their remains, recent finds tell us we also 

have their leavings! Yes, some of these creatures did what 

we all do and some of their leavings have been preserved, 

hidden for 320 million years until I split open a rock and 

found something new to here. 

Fossilized poops are known as coprolites. The name was 

given to them by William Buckland, a pioneering UK 

palaeontologist of the early 19th Century. He received 

his samples from Mary Anning, a collector and seller 

of fossils from Lyme Regis who had noticed that some 

unusual shaped stones found associated with the fossil 

ichthyosaurs (large marine reptiles) she collected had bits 

of fish and teeth inside them. She had also interpreted 

those stones as poop. 

Coprolites are classified as trace fossils as they are not the 

animal itself, just the result of the animal’s activity when it 

was alive. This is why the markings on the Moher flags are 

also classified as trace fossils, but they are the remains of 

burrowing activity not pooping activity. 

Coprolites are not commonly preserved; as poop,they 

would have been rich in food for scavenging creatures 

as well as bacteria, algae and fungi. Also, as most of our 

rocks were formed under the sea, the poops would have 

been very wet and disintegrated quickly on the seafloor. 

These leavings are extremely useful because they can 

preserve evidence that would otherwise have been lost. In 

the same way that a biologist can look into an owl or otter 

pellet to see what it was eating, we can see the remains 

of the food of creatures that died millions of years ago. 

Only the undigested remains are preserved, so Just like 

with fossils themselves, usually what is preserved are the 

hard bits. The most common remains found in coprolites 

are teeth and scales. In most cases the food has been so 

efficiently digested that nothing identifiable remains. 

Identifying who left the leaving is a different matter. 

Usually in any environment a number of predators eat 

more or less the same prey, so distinguishing the exact 

maker is difficult. There are some tell-tale signs however, 

for example sharks and some other fish such as the 

coelacanth have a spiral valve in their intestine, this gives 

a spiral, coiled appearance to their poop. 

The coprolites I found here recently are small (1-2cm) and 

some contain even smaller fish scales and bits of bone. As 

I found other remains of fish at the same place it is most 

likely the poops are the product of larger fish, which fed 

on smaller fish. This all adds to our understanding of the 

animals that lived here way before us. 

Good things come in small packages. 

Figure caption: Partially digested fish scale (2.5mm) inside one of the newly discovered coprolites.

The Burren and Cliffs of Moher 

UNESCO Global Geopark

Burren and Cliffs of Moher UNESCO Global Geopark - Geology

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