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  • Writer's pictureGeologX

Witnesses from the past: the earth "hairdressed" pyramids at Ritten

Columns of rocks - some of them wearing on top boulders likening hats of stone - are cropping out from the forested ravines of Northern Italy. The cone-shaped pillars were formed by the erosion of glacial moraine (here, a clay-like rock) during the last ice age period.

Earth pyramids formed from moraine clay soil left behind after the last Ice Age when the glaciers of the Valle d'Isarco covering the valley melted away. Rock fragments by different sizes, from fine loose particles to large hard boulders, were caught in the mass of the glaciers on the move. In dry conditions the clayey material is hard as stone, but, as soon as it rains, it turns into a soft muddy mass, starts sliding, and so forms 10 to 15-meter-steep slopes. Through additional rainfall, these slopes will erode. However, where there are rocks in the muddy mass, the clay soil underneath these rocks stays protected from the rain. So, while the surrounding material is continually carried off with the external factors, the protected pillars literally rise out of the ground to form majestic earth pyramids.

There are three groups of clay "hairdressed" pyramids on the Ritten (Renon) versant, risen in Isarco Valley. The columns are approx. 1000 m above sea level, emerge from the forest like sharp teeth and the highest are 40 m tall. They can be seen on the Renon in the Rio Fosco Valley between Longomoso and Monte di Mezzo, in the Katzenbachtal below Soprabolzano, in the Fosso di Castero near Auna di Sotto and near Gasserlahn at Auna di Sopra.

At a geological time scale, the earth pyramids are true miracles. The time-span of the columns is still a mystery, although it is known that some of them are modifying very little for decades. What it is certain is the fact that the biggest and prettiest ones develop over the timespan of thousands of years. Once the boulder falls from its peak, an earth pyramid quickly bites the dust. When this happens, the material below is naked, exposed to the rain, and the pillar shrinks with every rainfall. While one earth pyramid vanishes through this process, a bit further up the slope the next one comes to life - until all the material will be vanished from the area. Not far into the future, it is possible that pillars with hats from Northern Italy to be no more than a memory.


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