Posts Tagged With: Geology

Giant Steps

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The Giant’s Causeway is on every visitor’s must see list on the island of Ireland. For lots of different reasons. It’s a beautiful place on a beautiful coast, It has mystery and mystique. It is intriguing and enigmatic. That’s why over a million people a year visit.

It is located in Northern Ireland in a part of Antrim known as The Causeway Coast.  I have been there twice in the past year – in January 2017 in the depth of winter and in September. Both times I was gifted with marvellous weather.

For me as a geologist it was like worshipping at a holy shrine. So I thought I would put together a few of my observations from the two trips.  Apologies if this is too dry for you but you can skip the words and just look at the pictures.

So what are we talking about here?

The Causeway is part of an extensive coastline exposing thick basalt flows.  The scenery is nothing short of spectacular with sweeping bays and jagged cliffs stretching as far as the eye can see.

 

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The Causeway Coast looking west with Giant’s Causeway in the foreground.  

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The coastal path from the Causeway to the Chimney Tops past the Organ Pipes

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View west showing Causeway and Chimney Tops in the distance.

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Giant’s Causeway is on the right and the Camel Rock on the left.

 

The Giant’s Causeway is most famous for the spectacular columns, or more correctly ‘columnar jointing’ in the basalt. The origin of the columns has historically caused all sorts of consternation. Our forebears did not believe such regular shapes could be created naturally. So if it wasn’t the work of the Almighty then it must have been Finn McCool. Hence the legend of the Irish Giant constructing the causeway to engage with his counterpart in Scotland, Fin Gall.

 

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View from the clifftop down onto the Causeway.

 

 

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And he left evidence didn’t he? In his haste to get back to Ireland and escape from his giant nemesis, Finn McCool lost a boot which remains to this day adjacent to the Causeway. There is a more prosaic explanation and I’ll return to this later.

 

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The Giant’s Boot

 

The Causeway came to the attention of Science however in the late 17th century and right through the 18th century it was the focus of intense debate as to its origin. Geological science was then in its infancy. Two intensely opposed schools of thought developed. The Vulcanists, who believed the columns were basalt solidified from lava and the Neptunists who said that all rocks including basalt were sedimentary and formed in a great ocean. The Giants Causeway was at the centre of this debate. So it is one of the most significant places in the history of the geological sciences. That debate has long since been resolved in favour of the Vulcanists

We now know, however, that the columns are caused by cooling cracks that developed at the bottom of a lava flow where it was in contact with the cooler rock beneath. As the lava continued to cool these cracks slowly propagated up creating regular, generally six-sided (though they can have from three to seven sides), columns. These regular columns are called colonnades. The hexagonal shapes are caused by the joints tending to be at 120º to each other. At the exposed tops of the flows cooling was more rapid where there was contact with air and water, so the jointing was irregular and blocky. This type of jointing is called entablature. You can see this very clearly in many places especially at the, so called, Organ Pipes

 

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Regular hexagonal columns

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Columns with 4, 5, 6 or 7 sides.

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Columnar jointing

 

 

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Spectacular columns at the Organ Pipes

If you look closer at the columns you will see that in addition to the regular vertical joints that create the columns there is also another set of sub horizontal joints which slices each column into regular segments. These were created by the release of stress during contraction within the columns.

 

 

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Horizontal jointing

 

The really intriguing thing is that when these columns break along thee horizontal joints to form the rock platforms they are in fact ont horizontal.  Usually they are either  beautifully concave or convex and the segments fit perfectly together in a ball and socket arrangement. The concave joints are easily spotted on the rock platform as they retain pools of water.

 

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Detail of column surfaces.  water collects on convex surfaces

 

The columns make an impressive display whether on the rock platforms or in the cliffs.  There is a formation at the eastern end known as the Chimney Tops. If the illustration attached from an 1888 book is accurate, then the chimneys are considerably smaller than they were in the 19th century.   I suggest you go and see them before they disappear.

 

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Chimney Tops 2017

 

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Chimney Tops 1888

 

 

 

 

 

It is easy to see how the Neptunists thought the basalts were of sedimentary origin.  There is a distinct layering which could be mistaken for sedimentary banding. Of course it represents different lava flows.  particularly confusing is a distinctive orange red layer in the middle of the cliff.  It is known as an Interbasaltic Formation; a laterite horizon, and is caused by the basalts below it being exposed to weathering for a considerable time before the upper series of basalt flows were deposited. It also suggest a warmer climate at the time as laterites require tropical conditions to develop. It is composed mainly of clays and is rich in iron and aluminium (most other elements were leached out) and has been mined for these ores elsewhere in Antrim.

 

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Layering in basalt flows

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Interbasaltic laterite

 

 

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Laterite in detail

 

Within this laterite hori\on you can see relicts of the original basalt as paler partially weathered rock. There are also some excellent examples of preserved circular structures representing earlier spheroidal weathering within the normal basalt. This is caused by water percolating down vertical and horizontal cracks eventually creating rounded blocks. It is also known as ‘onion skin’ weathering.

Oh I forgot.  Finn’s boot.  It’s actually a glacial erratic, deposited by a retreating glacier at the end of the last Ice Age (about 10,000 years ago). Much more boring explanation.

 

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Giant’s boot.  Glacial erratic

 

I know I’ve gone on about the rocks but the spirit of the place is palpable.  The only word I can think of is Romance,.

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Romance and Rocks.  What a combination.

 

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The Torr Road Drive, Co Antrim. Lime Kilns, Game of Thrones and sublime beauty.

Travelling by car along the north coast of Antrim is spectacular to say the least. As seems to be the way of the world the drive has to have a label. So this is the Causeway Coastal Route because it features the Giant’s Causeway. I will blog on this and other places in due course because they warrant attention. But after Ballycastle, if you are heading east, the Causeway Coastal Route turns inland (away from the Coast – go figure!) towards Cushendun and Cushendall.  So most travellers miss a little pocket of Antrim that is staggeringly beautiful. This is the Torr Road which hugs the coast to Cunshendun.  Ireland is noted for its green of course but in many parts that green turns brown and red in winter.  Not here.  In this part of Antrim you seem to get the Forty Shades all year.

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View from the Torr Road, Antrim

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Green and gold.  Just add sunshine.  Torr Road.  Antrim

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Green slopes that run down to the sea.  Torr Road, Antrim. That current looks pretty treacherous.  Scotland is visible on the horizon.

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Coastal view, Torr Road.

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Fences need repair whatever the weather.  Torr Road, Antrim.

Of course the road leads to Torr Head.  This is the closest point to Scotland and from here you look across to the Mull of Kintyre.  It was very cold this morning, so I resisted the temptation to climb to the top. At the top of the headland is a tower which watches over the Sruth na Maoile (Straits of Moyle), a former haunt for privateers, and acted as a signal tower, passing on messages of ship movements to Lloyds of London.  There is also a now ruined, customs station which was abandoned in 1922. Its stark ruin brings an evocative supernal element to the gorgeous views both along the coast and back towards the hinterland.  Awaiting you, at the end of this drive at Cushendun, is the gateway to the Glens of Antrim, but that’s another story.

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Torr Head.

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Ruined Customs House, Torr Head.  Antrim.

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Ruins of Customs House, Torr Head

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Phone Box looking towards, Torr Head.

On my first drive along this road I went past a turn off to Murlough Bay. It was an inconspicuous sign and nothing drew my attention to it. If it hadn’t been for my B&B hosts that night at Teach an Cheol, just out of Ballycastle then I would have missed this little gem entirely. They insisted I go back there before leaving Antrim. Thank you  Micheál and Catherine.

The single lane road to Murlough Bay snakes off the Torr Road across brilliant green paddocks, and then suddenly drops off the plateau winding both perilously and picturesquely down to the sea. Remarkable views open up.

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Limestone cliffs at Murlough Bay.

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I passed a solid stone structure which intrigued me, so I dragged my eyes away from the view.  It was like nothing I had seen before and I later discovered it was a lime kiln where broken limestone rock was melted to produce quicklime. This was used for mortar or for agriculture. It was a thriving industry wherever limestone and coal (for fuel) was found.

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Lime kiln near Murlough Bay.  Front view.

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Lime Kiln from above.  Showing hole where lime and coal are loaded.

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Limestone cliffs

A little simple chemistry.  Limestone with the application of heat breaks down to lime with the release of carbon dioxide gas as in the following reaction

CaCO3 + heat → CaO + CO2

The reaction requires about 1000 °C. They were extremely common around Ireland and Britain, indeed in the mid 1800s there were believed to be 23,000 in Cork alone. There was plenty of limestone here with the surrounding cliffs. I’m guessing there was also a good supply of coal nearby too. I am always impressed by the beauty and solidity of the industrial architecture I come across here in Ireland. The stone work of the multiple arches over the air intake is stunning.

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So continuing down towards the coast I see a sign reminding me that this area was used to film episodes of Game of Thrones that hugely successful television series, still running. Of course you can see why. Film tourism has always been a big thing in Ireland what with The Quiet Man, Ryan’s Daughter, Father Ted, PS I Love You, and it continues with Game of Thrones and Star Wars.

Murlough bay is a place of singular beauty. You leave the car and walk along the track which follows the coast to a whitewashed cottage with the most perfect location in Ireland. There is a second small abandoned cottage; padlocked but in reasonable condition. A peek in the window and I can see some bottles of disinfectant and cloths suggesting a level of optimism by the owner. What a place for a holiday batch. Nearby there is another lime kiln.

This place is everything that makes Ireland beautiful. Cliffs, washing waves on rocky shores, boulder beaches, jagged headlands, green fields rolling into the sea, craggy islands, little coves. The surprising variety of landscape is a result of a rich geological melange which I might talk more about at another time, but I saw metamorphosed schist and gneisses, basalts, sandstone and conglomerate, limestone and of course the ever-present carpet of bog over it all. A geological history of 600 million years on display in this little bay.  Again a sign tells us a little cove here was used in another episode of GOT.

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Distant view of Murlough Bay

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Murlough Bay looking east.

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Murlough Bay looking west.

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Basalt outcrops forming islands and bays

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Murlough Bay.

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Murlough Bay.  Sandstone rock platform with narrow bands of conglomerate.

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Murlough Bay.  This view has sandstone, basalt, gneiss and limestone.  A geological melange.

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Murlough Bay.  Abandoned cottage on the shore.

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Another lime kiln on the beach at Murlough Bay.

Again a sign tells us a little cove here was used in another episode of GOT.

It is hard not to use clichés in describing this spot. I was the only one there and it was so quiet and so still. the only activity was a fishing boat, way out in the channel and the only noise was the ripples lapping the shore and the occasional squawk of a gull. There was an undisturbed equanimity and you could feel tension disappearing with the tide. Just me and my thoughts. I didn’t want to leave. I have been to so many beautiful places in Ireland, but not felt this way before. Surrounded by natural beauty, yet somehow otherworldly.

Extraordinary.

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All is not what it seems. A little story from the Wild Atlantic Way on the west coast of Clare.

I live in a remarkable spot and I have written of it and photographed it many times. Point Caherush lies between Quilty and Spanish Point along the spectacular west coast of Clare.  Indeed it was spectacular before it became part of the Wild Atlantic Way but now of course it is legitimately spectacular because it has a label with the word ‘wild’ in it. Anyway I live at the end of a one kilometre long boreen known locally as the Clogher Road. My front door looks out over Quilty and Mutton Island. Here’s a reminder.

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My little cottage nestled on the rocks at Pt Caherush

 

The rocks at my feet though are similar to the rest of the West Clare coastline from Loop Head to Doolin, and comprise shallowly dipping interbedded sandstones and shales.  For the whole time I have lived here I assumed that I was living at the edge of a wilderness (that’s the ‘wild’ in Wild Atlantic Way!). A thin strip of pristine land beyond the rolling green that is everywhere so heavily moulded by man.  I surmised, somewhat romantically, that only the hand of the sea had sculpted the shore. Despite this I was troubled by some observations I could not explain. Perfectly circular holes in the rock sometimes with radial joint patterns around them were disturbingly reminiscent of what I had seen in open cut mines. This made no sense. There was nothing to mine in these barren sandstones.

But I didn’t think of the sandstone itself.

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Perfectly circular holes and radial joint patterns on the rock platform at Point Caherush

 

One day I was chatting to Mikey Talty, a resident of this place all his long life. I have written about that day in a previous blog, when three generations of the Talty family were harvesting kelp from the bay. Mikey is full of wonderful stories but he really got my attention when he mentioned working as a young man in the 1950s at a massive quarry operation on the Point. He showed me where the crushing plant was and described how truckloads of rock were carted away to build roads as far away as Kilrush and Kilkee. This mining it would seem had changed the shape of the headland and much of the protection of the bay was lost.

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Mikey Talty talks about Caherush in his youth.

 

With this new knowledge I now see the evidence everywhere in my wanderings. Of course the drill holes were for the explosives, some still showing their perfect shape and probably unexploded, and others with radial shatter patterns showing they did their job. There are rock exposures that are not natural and there is angular rubble strewn, that has yet to be smoothed out by the ocean.

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Blasted face at limit of quarrying

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Quarried rock face and blasted rubble

 

It is hard now to understand the thinking that would have led to the locating of a quarry here when there would have been plenty of locations away from the coast. I would like to think that in ‘modern’ Ireland it would be impossible to conceive of permission being obtained today for mining on the seashore. Perhaps planning approval wasn’t needed then and certainly priorities would have been different.

I can find nothing in the literature about this operation and maybe the memory of it is only now with those who lived or worked here. But the record will stay in the rocks for hundreds of years and I am sure it will confuse and intrigue future generations of geologists and non-geologists, who wander around Point Caherush, as it did me.

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The Burren, Again.

The Burren in the north of Clare has an indefinable pull.  I can’t stay away.

When Geraldine, schoolteacher friend, asked me if I wanted to accompany her and the kids from her school at Doora near Quin on a hike through the Burren, I was a bit unsure. Didn’t sound all that exciting but I have made it a rule not to say no to anything since I’ve been here. So I agreed. I’m really glad I did.

The day did not start out too promising. I met Geraldine after a couple of false starts at 11:00am and four carloads of kids from 5th and 6th class with a handful of parents and teachers met at Crag Road, the start of our linear hike. We had hoped to use the National Park free bus service but times did not work so some cars were dropped over to Coolorta Cross, the end of the hike. By 11:45am we were on our way!

The weather was overcast but dry though rain was predicted (of course). The plan was to head up to Mullaghmore and then across to the next mountain (well they are technically hills) knows as Sliabh Rua. Wasting no time the kids headed out along the trail leaving me and a couple of stragglers in their wake. We caught up eventually (well I think they waited for me) and with barely time to catch my breath I found myself giving a talk on the unique geology that is the Burren.  After a month in Clare I was an expert on the Burren geology. Well the kids thought so. Some of them were surprisingly up to speed while others hadn’t even stepped foot on the Burren before.

We continued the climb along the ridge beneath the first cliff and I kept stopping to look at the amazing fossils and rock formations and to take photographs so of course we got further behind. By this time I was left with just one boy who delayed me further as I stopped to answer the non stop stream of questions and comments about what he was seeing. It was great to see this unbridled curiosity and his eyes opening to what was around him. Eventually we rejoined the group.

As we were on a deadline and I was slowing them down, we agreed they would go ahead and I proceeded at my own pace. I was in awe of the scenery at the top. Limestone bands twisted into gentle folds ran in sinuous waves across the barren treeless landscape. With the dull light it had a mysterious mystical quality reinforced by the clarity of the eerie silence. Truly a breathtaking place. In the distance I could see the group had reached the top of Sliabh Rua and were now proceeding down so I followed the contours around the mountain and attempted to re-join them. Distances are deceptive up here. It was a fairly treacherous descent over boulders and scree formed from jagged limestone. Every foot had to be carefully placed so there was no rushing. I would stop often to breathe in the view. A new vista around every corner. I never did catch them and I arrived at the cars about half an hour after the rest. We were lucky. The rain had held off.

I was mightily impressed with the whole day. The kids behaved impeccably and were a credit to their school.

Once they had left, Geraldine wanted to show me more of the Burren, a place she clearly loves, so we headed along another track to a Holy Well. I had never seen one before. This was a natural spring coming out of the base of a moss covered rock. Nestled in a dark cool glade which felt as ancient as it probably was. It would not have surprised to see fairies darting about!  There were cups hanging from a string inviting you to partake and there were ribbons hanging from nearby branches, perhaps some sort of offering.   An elliptical walled area a few metres across was apparently an ancient bath which was used for ritual bathing. It takes a while to get one’s head around the fact that this place may have been used by our predecessors up to 5,000 years ago.

The magic of the place was having an effect. We walked back along the track to see a car driving up the lane. I did not recognise the occupants but Geraldine did. There was P.J. Curtis (the eminent writer/record producer/broadcaster/historian) and Maurice Lennon (fiddling legend from Stockton’s Wing). I was introduced to them and they couldn’t have been nicer. We ended up back in P.J.’s house in Kilnaboy (built in 1770, the year Cook landed in Australia) listening to Maurice play tunes from ‘Light in the Western Sky’ (one of my favourite albums) and then some gorgeous airs including one of his own on his Viola. I had to keep pinching myself. P.J. gave us a tour of his Forge which was full of original equipment. It was the conclusion to a wonderful day.

If you go with the flow in this extraordinary country then extraordinary things happen.

 

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Burren Limestone with fossil coral

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Some of the wildlife in the Burren

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Geometric patterns etched in the cliff face. The Burren

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A large fossil coral colony. The Burren

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On the way up to Mullaghmore

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Pausing for a breather.

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the view from the top

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Heading across to Sliabh Rua

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Spectacular landforms that make up the Burren

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Twists and contortions in the limestone layers on Mullaghmore

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One last cliff on the ascent of Sliabh Rua

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Looking back from Mulalghmore

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Gentle folds in limestone, Mullaghmore

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Cairn, Mullaghmore, the Burren

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The descent from Mullaghmore

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Native orchard, the Burren

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Limestone plain at the foot of Mullaghmore

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Returned safely

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Holy Well, the Burren

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Moss covered walls of an ancient bath, Holy Well, the Burren

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Glacial erratics, dumped at the end of the last ice age. The Burren

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Meeting Maurice Lennon in the middle of nowhere

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Mullaghmore. A distant view

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PJ Curtis outside the Old Forge at Kilnaboy

 

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