Winter storms scrape a lot of sand and debris from our foreshore uncovering a mysterious treasure of drowned forests and legendary 'palaces' or 'Llysoedd' in Welsh.

At Splash Point, Rhyl (the right-angled bend at the end of the Sun-Centre road), at some low tides you can see ancient, sodden tree stumps. They are thought to date from the Mesolithic or 'Middle-Stone Age', between 10,000 and 6,000 years ago, or early Neolithic (New Stone Age). This would tie in with the end of the last Ice Age. The amount of water frozen in the ice sheet left the sea level much lower than today, much of the Irish Sea was dry land. When the vast ice sheet melted, probably over hundreds of years, the sea level rose, and all along our North Wales shore there must have been drowned forests.

Since then the land has actually been slowly rebounding, like a dense foam mattress when you rise from it. The weight of one mile thickness of ice being released has caused this 'isostatic rejuvenation', and you can often see the evidence on seaside rock faces as a darker coloured band to about 25 feet up the cliffs. And this land-rise re-exposed the forests that were buried by sediment for millennia.

The first evidence we have for people in Wales comes from the site of Pontnewydd Cave near St Asaph. Here excavations have identified the remains of an early form of Neanderthal that lived around 230,000 years ago, in the Palaeolithic or 'Old Stone Age'. This was probably in one of the warmer periods between Ice Ages. Other caves occupied in the later Palaeolithic include two near Tremeirchion.

Encroaching ice drove these people out. Then about 10,000 years ago the climate in Britain became warmer and wetter than it is today. This led to changes in the vegetation of Wales with the development of a wooded landscape, and people came from the south again as hunter-gatherers, only staying in local caves as 'hunting lodges'. This Mesolithic period lasted until the introduction of farming around 6,000 years ago. Stone tools and an antler pick have also been found on the beach at Rhyl.

You can find out more about local natural history and archaeology in 'A Country Diary for North Wales', a compilation of my Denbigh Free Press columns over two years.