The Geological Trail at Dos Capel
The texts that follow are taken from the boards along circular geological trail at Dos Capel, one of the best locations in the Dolomites where to find out about the region's complex geology.
In 1800, Predazzo's unique geology made it a mecca for geologists: everyone wanted to study the rocks around here. Two scientific theories collided: neptunism vs. plutonism; the second prevailed. It paved the way for a modern understanding of the origin of rocks and the evolution of our planet.
All rocks were formed in a primordial ocean that covered the earth. Rocks accumulated into the seabed in a pre-established, unalterable order. Granites and schists, the oldest rocks, were formed earlier. Then basalts and some sedimentary rocks followed; lastly, sedimentary rocks with fossils, such as limestone were formed. Granites are always found under the limestones, and they are always older.
The Earth's motor is underground heat released by periodic volcanic eruptions. Granites and basalts are formed as magma rising from the bowels of the earth and seeping into pre-existing rocks solidifies. Granites can lie above the limestones and can therefore be younger.
The Origin of the Dolomites
How were the Dolomites formed? In the sea, of course! That's right: 250-242 million years ago, instead of walking along these paths, you would have been sitting with your feet immersed in a sandy seabed. How do we know? Well, the rocks told us... .
The thin layers are a kind of certification of sedimentary rocks of marine origin: undulations on the surface of some layers, imprinted on the sand by waves are fossil snapshots from a beach that no longer exists.
If you look carefully, you'll see these rocks are nothing but billions of grains of sand from ancient beaches, cemented together.
Fossil shells, encrusted in the Dolomite rocks, are irrefutable evidence of an ancient marine population.
4. Every Shape has its Rock
The regular shape of the Pala di Santa slopes gently towards Passo Pampeago, beyond which rises the truncated limestone pyramid of Latemar: every characteristic shape in the Dolomites' landscape corresponds to a particular type of rock. Sommon common types of rock include:
Porphyry: derives from volcanic eruptions; 280 million years ago. It is a hard, compact, resistant rock. Morphology: flat, regular shape.
Sandstones, limestones and clays: 262-240 million years ago; from river plains and coastal sea. They are soft rocks prone to erosion. Morphology: gentle hills covered in vegetation.
Reef limestone: 240 million years ago; atoll surrounded by the sea. Compact but friable rock. Morphology: cliffs, spires and pinnacles.
5. Everything Upside Down
Fractures, folds, vertical layers: the geological landscape here is complete chaos. It's all down to the Stava fault, a crack in the rock that turned the whole environment upside down when it was formed. Latemar was raised several hundred meters above Monte Agnello, and the rock layers, once horizontal, are now vertical.
Fancy a dip? Yes, right here, 2000 meters above sea level: a special dip to discover the submerged world of the sea depths, 240 milion years old. Imagine this rock wall is the glass of a big aquarium, and you're looking through it, onto a sea hundreds of metres deep. The light is dim; there is little oxygen. With a bit of luck, you'll be able to make to make out the shape of an ichthyosaurus, a fearsome predatory reptile, or a few ammonites. Thin layers of silt accumulate, one on top of the other, to form the seabed, where worms, molluscs and other strange animals live. Get closer to the rock wall to continue your discovery of this ancient submerged world.
In the eyes of a geologist, Latemar is a large, submerged tropical atoll. Notice the horizontal strata in the upper central part, and the slanting strata to the sides: they mark the shape of what was once the island of Latemar.
The horizontal layers that you see on the top of the Latemar tell us that the waters that filled the inner part of the former island were calm and shallow. The sides of Latemar are carved out of huge, badly stratified rocks, formed out of limestone blocks that rolled down from the island summit to the depths along the steep underwater scarp slopes, which are now the flanks of the mountain.