The Transforming Tide

I have been reading James Millar's fascinating book, A Wild and Open Sea : The Story of the Pentland Firth, which details both the history and the marine geology of this turbulent body of water. I was particularly interested in the detailing of the action of the waves upon the coastline- the process, over centuries, of the swell pounding and continually eating away at the cliff-edge. Interestingly, the terminology used locally to describe cliff erosion gives a tantalising hint of the old Norn language once used in Caithness: Gloups, Geos, Cletts, Thirl doors, Skerries. Some of the Norn bird names survive in usage to this day : gulls are still referred to as scorries (skári, N. ) cormorants, scarf (skarfr, N.) (http://nornlanguage.x10.mx)

 It was the continual transformation from one  rock formation to another that I found intriguing: the sea carves an opening into the side of the cliff (Thirl Door): this can continue through to the interior , creating an upwards surge which creates a blowhole (Gloup) on the interior of the cliff: this can then wear away further to form an arch: this, in turn, can collapse into a freestanding stack, or clett: this eventually disintegrates or is worn down into a small islet, a skerry.

Thirl Door, Holborn Head, Scrabster.  

I love the linear shapes of the rock in this shot: the promontory itself has an old slate quarry nearby, and it is easy to see the slabs lurking within the geology.

The swell at the foot of the cliff created a fantastic sonic boom as it echoed around the inside of the door.

Gloup on the interior surface of the thirl door - the inlet at the back drops right down to the sea ( this was as near to the edge as I was prepared to get!)

The top surface of the same cliff : the opening to the gloup is in the centre

Cliff edge, looking Northwest

Another  Holborn Head gloup , this time the sea is clearly visible

Geo: a very common feature of the Caithness coastline. The sea below (1) and water flow from the surface (2) combine to carve a narrow inlet into the cliff. These vary in scale and size- some are very narrow: others, like the one at Whaligoe (https://en.wikipedia.org/wiki/Whaligoe) on the East Coast of the county, are substantial enough to have been used as small natural harbours. Geos provide a perfect, "high rise" habitat for nesting seabirds : the shags and cormorants lay a single egg on the bare rock ledges at the bottom, guillemots live up a level, fulmars and kittiwakes on the higher shelves and puffins burrow in the sandy topsoil . (http://caithnessbirds.co.uk/wp-content/uploads/2013/11/Caithness-map-21.jpg)
                           
(1)

(2)

Man-made activity on the clifftop- slate cairn and names graffitti'd on to the surface of the rock

More slate formations, in a geo and on the clifftop.

Holborn Head lighthouse and the terminal for the Orkney ferry, with Thurso in the background.

Duncansby Head, John O'Groats
 Possibly one of the most well-known sights in Caithness - the stacks at Duncansby head, on the most northeasterly point of the county.

This shot illustrates perfectly the continual process of erosion and transformation: the arch in the foreground still attached to the cliffside, the needle-sharp "stacks" (cletts) in the background, with the remains of smaller cletts being worn down into skerries. Eventually there will be no trace left.

Two smaller cletts, Duncansby. The larger clett is already in the process of disintegration (although not visible in this shot) - the jagged upper portion nearest the cliff-edge is teetering precariously, and could well disappear in a suitably violent storm.

Thirl door transforming into an arch near the Stacks- at the sea edge of the picture below- note the red sandstone here, in contrast to the black slate of Holborn Head

A wider shot, showing the Geo. Unfortunately a little early in the year, but during the nesting season it is filled with birds from the sea ledge to the topsoil. A few fulmars are visible near the top.

This process of erosion and transformation inspired the following poem; Firth - the words mimic the actions of the sea and the shapes carved into the coastline. It will also form the basis of a transformative musical composition- work is still in process.

Firth

Corrosion

              Corrasion

Geo carves into stone:

Birds' haven, fishers' landing.
Thirl Door

Sonic boom

 Walls echo an ominous percussion.

                        Hydraulic action

       land.

                Gloup within

                    punches Sea

                              through.

                                                 

                   

 Corrosion

      Corrasion

       arch

       clings on

by umbilical gneiss.

Corrosion corrasion

Waves a relentless quernstone.

Arch succumbs to

Clett

Clett stands defiant but

Cannot resist

Attrition

to skerry

Sker

rry

to

.