How often have we heard people say "Coll has changed so much"? Time and again, I'm sure. But there is one respect in which they are wrong.

If the island were to be abandoned by man and his machines for a few millennia, there is every possibility that some future traveller, rounding the Cailliach from the sound of Mull would see the same forbidding grey sawtooth silhouette, which can so unaccountably warm the heart. Drawing nearer there would still be the same rocks, the same bays, the Meall..

Some things do not change, so far as mortals are concerned. As Gavin Maxwell said - "The Rocks Remain".

The craggy old face of Coll is made of rocks which are truly ancient, mostly known as Lewisian Gneiss (pronounced 'nice') as they are related to the rocks of Lewis. Maybe if Coll had been a more favoured place for geological study - in the olden days - it might have been "Collian Gneiss"?

Lewisian Gneiss is about the oldest surface rock in the world being around 3000 to 4000 million years old. Apart from Tiree, who is of the same crusty breeding, our neighbouring islands are mere children by comparison.

The Treshnish Isles, which are the solidified remains of layer upon layer of flowing lava, and the older rocks of Mull and Ardnamurchan through which the lava erupted, they are all barely out of their teens compared to the grand maturity of Coll.

The separation in age between us and them is the result of a gigantic movement along what is known as the "Moine Thrust Plane". This is a line which slices all the way down the west coast of Scotland, past the tip of Ardnamurchan, along under the sea bed between here and the Treshnish, and finally clips Iona off from the Ross of Mull. Along this fault line the land masses once moved past each other, just as they are moving now, on the San Andreas fault-line in California.

When the Almighty turned in his sleep in the morning of creation the great rock blankets slipped over and past one another, and up from the depths of the mantle of the earth came the ancient rocks of Coll.

Since these ancient times many less dramatic but still unbelievable forces have been at work. The great volcanic eruptions in Mull and Ardnamurchan started with mountainous globes of hot lava trying to burst through to the surface. The forces caused cracks in the rocks and up through these fissures for many miles around oozed the hot glowing liquor. But time passed, stresses eased, rock cooled, and trapped in the speckled grey Gneiss were new veins of rock, now cooled to a black smooth hardness.

Periods of climatic turbulence and aeons of calm (changes we would find hard to believe possible) all came and went, each adding or taking a little from the face of the earth. For example the Sandstone Tenements of Glasgow are built of rock quarried in Ayrshire, rock which was created in the sand dunes of a great hot barren desert!

Then recently, a few score millennia ago, came the ice ages when the seas fell and great sheets of ice swept down and out from the highlands of Mull to scrape and scour the surface of the land, picking up rocks and gravel as they went. Then the years grew warmer: the snow ceased, the ice melted, the seas rose, and the shape of land was 31 finally revealed much as we see it now- the great boulder on the shoulder of Ben Hogh comes from Mull, one of those left by the melting ice. There are gouges and scrapes near Feislum where ice-bound rocks were dragged across the surface.

Black slabs of basalt rock -the veins of lava I mentioned - are much softer than the native Gneiss and are visible in small inlets. for example at the west end of Cornaig Bay. The sea has already worn them down below the level of the surrounding rock. (In Mull they actually stand up, about three feet high and wide, and earn their geological name of "dykes").

The varying land and sea levels have also left their marks: for example there are the remains of a beach in the high ground behind Arinagour.

After such a turbulent past, some other geological curiosities must be around somewhere, as indeed they are: marble of all things, although of a rather crude quality can be found near Garden Cottage. Little dark red garnets, (semi-precious stones) can be detected in the rocks near Ben Feall by a dedicated seeker, though again they are sadly of rather low quality.

It's been said that the geology of Coll is rather dull but it has had rather an exciting past. So the next time you hear bemoaning about the sadness of change you can demur... "Och well, most of it hasn't changed... at least, not recently".