The Ritten Earth Pillars, Italy

These extraordinary structures can be seen in northern Italy, in wooded ravines on the Ritten plateau, which is near the city of Bolzano. There are three groups of these pillars, in separate valleys. They are at a height of around 3250 feet (1000 metres) above sea level.

Jagged, tapering clay spires, some of them coloured in shades of red or violet, stand up to 130 feet (40 metres) high, most of them being crowned by a block of stone.

These pillars were created at the end of the last Ice Age, about 10,000 years ago. As glaciers moved across the land they carried rocks of various sizes hundreds of miles from their original locations, as well as vast quanties of softer "boulder clay". When the glaciers stopped and melted, the rocks were left in place on a thick layer of boulder clay. Rainwater then carved gullies in the clay, but where there was a rock, the clay beneath it was protected. The pillars seen today are the result.

One factor that could have accelerated the formation of the pillars was the development of agriculture in the region in the 13th century. Clearing the forests to create pastures and vineyards could have laid the land open to the erosive power of rain.

Not surprisingly, pillars like these - and they are found in a few other places around the world apart from here - have gathered a certain amount of folklore and superstition around them. They are known in north Italy as "little men" and "earth mushrooms". In France there is a group known as "young ladies with their hats on".

The pillars have been there for thousands of years, but they will not last for ever. If a rock falls from the top, the rate of erosion of the pillar will increase considerably until there is nothing left. This will eventually be the fate of all the pillars.

However, a fallen rock may then serve to protect the boulder clay on to which it has fallen and a new pillar will form. This process could continue until the base of the boulder clay layer is reached.

© John Welford