Stones in every imaginable size and shape can be found in the Bletterbach gorge. They have been on the move for millions of years.
What can they tell us?

	Bozen quartz porphyry 280 to 260 million years ago, hot ash and lava was thrown out as a result of violent eruptions following major volcanic events. In this way a mighty mountain range was created on the North African continental plate – the Bozen quartz porphyry plate. At that time, the porphyry zone was located near the equator. Nowadays, Bozen quartz porphyry – reddish grey to dark grey in colour – forms the basis of the Bletterbach gorge.
	Gröden sandstone Deposited and hardened … Heat, water and wind began their work. Over millions of years, large parts of the porphyry mountains were carried away. Torrential streams and rivers transported the fine sand to coastal areas and deposited layer upon layer. Finally, consolidated by chalky and siliceous materials, and under the enormous pressure of the chalk layers above it, a new rock was created – sandstone. The strata are of different colours because they contained different dissolved minerals. Traces of animals and the remains of plants were embedded in the sand or mud and preserved. They provide insight into the history of life on earth.
	Bellerophon strata Towards the end of the Permian era, 250 million years ago, the land sank and the sea advanced a long way westwards. Shallow coastal waters and lagoons characterised the coastal plains, comparable with the Adriatic nowadays, in the area of Venice. The climate was hotter and drier, however. (The shallow lagoon area repeatedly dried out in the course of periodic tidal movements, only to be flooded again. Under the tropical sun, clumps of gypsum built up in the mud of the lagoon, which can be found in the strata today. The gypsum deposits in the gorge, ranging from white to red in colour, are an indication of the proximity of maritime habitats.) The upper layers of the Bellerophon formation mark the Permian-Triassic border, the transition from the Palaeozoic to the early Mesozoic era. As a result of a catastrophic event, the majority of the flora and fauna of the time died out. New species arose – they can be found as fossils in the Werfen strata which lie above. The precise cause of the mass extinctions is not known (possibly a meteorite collision, a change in the earth’s climate or a change in the maritime currents)
	Werfen strata At the beginning of the early Mesozoic era, 248 million years ago, the sea spread out in a westerly direction. About 400 m of major strata was deposited. They are of varying construction, and provide evidence of the alternation between advancing and receding phases of the sea. Some parts of the Werfen strata are very rich in fossils.
	Sarl dolomite The summit of the Weisshorn mountain is made of sarl dolomite. The rock was formed from algae containing calcium carbonate in a shallow sea.

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