It seems odd to stand on a beach and tilt your head up for a view of the ocean floor, but that remarkable feat can be achieved on West Shore Beach at Llandudno. The cliffs and slopes that terminate each end of Ormes Bay are the petrified remains of a former sea floor - the bottom of a shallow sea, now long gone, that existed over 325 million years ago. This is not unusual; most mountains are made from sediments laid down in the ocean. What is special about limestone uplands like the Great and Little Orme, is that they were originally made a long way offshore. The sediment that created them did not come from the erosion of an earlier landmass; it was left by living organisms.

The uplands around Llandudno were laid down in a shallow tropical sea during the Carboniferous, a period of deep time that teemed with life. The southern shore of this ocean continually moved, with the sea periodically inundating and then receding over dense lowland rainforest where ancient dragonflies reached the size of seagulls and millipedes grew to one and a half metres long. Continual flooding of the forest floor left layers of dead plants collecting and compressing over millions of years to eventually form the coal seams of South Wales. Carboniferous means coal-bearing.

Like the coal seams to the south, the Carboniferous limestone around Llandudno is made of life itself. The Orme limestones were formed from the shells and exoskeletons of billions of brachiopods, crinoids and corals. When the limestones were first laid down, Wales was located along the equator and the climate was similar to the modern Bahamas. Britain also lay at the centre of a super-continent of all the world's land called Pangaea. In Pangaea, a walk from Llandudno to New York would have taken about a month, followed by a wait of around 330 million years.

As the continents crushed into one another for Pangaea's assembly, the Caledonides - a mountain range of Himalayan proportions - formed to the north eventually eroding down to the Scottish Highlands. It was during this period of mountain building that the Orme was uplifted. From the Promenade, you can even see the fold of the rock beds above the Grand Hotel and under the pylons of the cable car.

Mineral-rich water seeped into the fissures created as land was uplifted and rucked like a rug. Dissolved copper crystallised into ore known as malachite and enough of it would be extracted from the Great Orme mine during the Bronze Age to make at least ten million axe heads. The Orme was one of the largest industrial sites of the Bronze Age world.

In the shadow of the past's industry on West Shore Beach, pails of sand are temporarily installed in the form of five of the world's highest peaks, one for each inhabited continent. Next to the seeming permanence of the Great Orme, they are fragile structures against the sea, but every mountain eventually dissolves to an incessant and unfaltering tide - erosion now hastened and catalysed by acid rain, habitat loss, walking boots, tyres and over-grazing. Our mountains are fragile too.

In other parts of the world, mountains stand aloof. Wood smoke fills the valley floors, agriculture, industry and the material needs of people predominate below, while the mountain is the home of spirit, the mark of permanence, the symbol of calm. On the seaboard of Wales, it was reversed. The mountains were places of industry - of mines and quarries - while, in the valleys that met the shore, buckets and spades beside the seaside had an altogether different purpose to their mountain counterparts.

Much of that has been upended and usurped by technology, by modernity, by the blunt forces of economics and politics. The industrial mountain has become silent, even in the hubbub of its new appeal to tourism. But, within the projected spectacle of visitor centres and heritage attractions, we should take a longer view, not only at our own lives, but at the lives that made the mountain and the lives it created, enhanced and to which it added the illusion of permanence.

First commissioned for the artwork First There is a Mountain, by Katie Paterson