Thomas Malloch

At the edge of our patio, we have a collection of stones. One in particular catches the eye. It has a dominant greenish colour but with a chaos of blue veins running in all directions and when held to the sun, glassy glints. In the hand it is warm and light, soft even, with a peculiarly greasy feel.

It was gathered from the shore at Lendalfoot, some six miles south of where we live. This was during the first COVID year, our Far East travel aspirations having to give way to staycation projects such as the local geology.

After the first lockdown restrictions had eased, our son came to visit. Weather being fine, we set up the garden table to eat outside. I handed him the stone.

“What do you think of that?”

He rubbed at it with his thumb. “Feels like a snake.”

“A snake? When have you ever handled a snake?”

He told of how he once pulled a snake out from under the stove at a friend’s house, the friend being the son of a local vet.

Now, nobody in our family is a geologist but this unprompted observation seemed confirmation of what my wife and I had suspected. The stone was serpentinite, so named for its texture, though to my untrained eye, it also has the look of snakeskin. And what is remarkable about that, is that this type of stone comes from below the earth’s crust. So how did it end up on a beach at the edge of the Atlantic Ocean? Answer: the beach once lay on the edge of another ocean, one that is now extinct.

The Atlantic Ocean was named for Atlas, a character from Greek mythology. He was one of the defeated in the War of the Titans, after which Zeus condemned him to stand forever at the western end of the known world and bear the heavens on his shoulders.

The father of Atlas was Iapetus, who also had an ocean named for him. 500 million years ago, this ocean lay between two continents, Laurentia to the North and Avalonia to the South. As these land masses came together, the Iapetus was obliterated. The ocean floor was topsliced, a process known as obduction. Rocks from below the seabed were deposited on the cutting edge of Laurentia. Instead of an ocean, we had a suture line. The political boundary separating Scotland and England today, roughly follows that line.

In time, the supercontinent of Pangea was formed, only to break up about 300 million years after its creation. But the lines of cleavage differed from the suture lines. One line of separation became the Atlantic Ocean and the geologies either side of that ocean, reflect their origins. Scotland’s south-west has more in common with Newfoundland in Canada, than Cumbria, just across the Solway.

This then is where we live, on the edge of two oceans, one historic and one present-day. It’s a doubly marginal place. And margins are always interesting. But sometimes, a way of looking is required and it is a knack of which I am well short of mastering.

What is of interest here is the assemblage of rocks that happen to be exposed on the coastal margin between Girvan and Ballantrae. It has a name – the Ballantrae Ophiolite Complex (ophiolite from the Greek, meaning snake stone) and is famous in the world of geology. Why? Because this assemblage has more to it than just ‘snake stone.’ The serpentinite is mingled with mixed beds of lava and sedimentary rock, the whole area seeming to early geologists, to be a confused jumble, one that required unpicking.

So, imagine the existence of volcanic islands at the time of the disappearance of the Iapetus Ocean. As hot lava pours into the sea, it rapidly cools, forming stone ‘pillows’ that come to lie on the ocean floor. As Laurentia/Scotland collides with Avalonia/England, these lava pillows are forced to the surface in much the same way as the serpentinite. Today, they can be seen at various points along the coast but the finest examples are at Downan Point, just south of Ballantrae.

When the sea returned and sediment accumulated, slopes began to fail. Underwater avalanches allowed for deposits of sand and mud to be laid down, one layered above the other, and eventually these layered deposits became stone. The layered stones have a name – turbidites, reflecting their origins, the rapid downhill flow of sediment-rich water.

Later still, under the pressures of tetctonic shift, these layers were forced upwards and rotated. In essence, this is the story of the formation of the Southern Uplands range, where the turbidite formations lie hidden below the expanse of rolling green hills. But at the coast, that layering is sometimes in clear view and at Ardwell Bay, south of Girvan, there is a striking example. The rock formation is striped with the depositions. It is a cross-section of what was once horizontal, now turned through ninety degrees to the vertical.

A few miles down the coast from Ardwell Bay and we’re back at Lendalfoot where, on the landward side of the road, can be seen small, remnant sea stacks in the middle of fields. The fields are backed by cliffs and above these cliffs are more fields. These are raised beaches. It’s not hard to visualise the higher fields terminating at the cliff and the lower fields being the seafloor. The sea stacks would have once stood tall but over time, they have been much eroded by the elements. And the underlying reason for this present-day appearance? The ice age, or rather the ice-ages, and the subsequent melts.

This process started 2-3 million years ago. At times, the ice was estimated to be 5,000 feet thick. Think of that. Think of Ben Nevis (4,400 feet). Think of the weight of that volume of ice. Think that land masses essentially float on a core of liquid rock. Think of all of that and it’s easy to imagine the land sinking under the weight of the ice, and easy to see that it would rise again when the ice melted, thus creating those raised beaches and exposing those sea stacks. Even today, the land is rising by about 0.5mm per year.

Of course, I am relating a simplified, forward chronology. But if you were a geologist of the late eighteenth century, you’d be looking at the stones and working back to their formation. Academic rigour would be a given but we also need to credit the imaginative capacity of these early geologists. They would have concluded that these rocks were millions of years old and that the world was billions of years in the making; revolutionary thinking at a time when the establishment churches still held to the Bible’s six-day creation story.

On clear days you can see the gap between The Mull of Kintyre and Northern Ireland. Beyond that is the seeming vast and timeless ocean. Now consider the serpentinite at the edge of our patio. Timeless though the ocean to our west may seem, this stone is more than twice the age of that Atlantic Ocean.