The “Geological Museum of the Dolomites”
“This (area) is the key to the Alps… home of the most diverse and wonderful geological phenomena”.
This is what Leopold von Buch – one of the scholars who explored the valleys of Fiemme and Fassa – wrote in 1827. In 1819 a sensational discovery (made right here, near Predazzo, in the Fiemme valley) had revolutionised the theory about the origin of these mountains; since then, the Dolomites have become famous all over the world.
The Geology Museum in Predazzo was founded in 1899; its collections consist of fossils, minerals and rocks coming mainly from the Fiemme and Fassa valleys: on the ground floor are displayed samples that synthetize the importance of this area, and its relevance for the development of modern geology. Here one can be introduced to the most significant finds; i.e. the typical minerals of the Dolomites, and the ancient volcanoes of the area (most notably, the Monzoni group, 2,641 m asl). An exhibition area illustrates the local ancient mining sites, as well as the evolution of the extraction techniques. The Museum’s numerous cultural offers include guided tours, workshops and conferences on geological and naturalistic topics. A brand new layout to the Museum has just been finished after refurbishment.
Short Museum Guide to the Minerals, Stones & Fossils of the Dolomites
Section 1. Geological Research in the Fiemme and Fassa Valleys
1A). Geological specimens, minerals and mining tools are shown in this section together with some historical documents that highlight the ancient and prolonged interest that scholars have devoted to this area of the Dolomites; the Museum itself stems in fact from this long-lasting relationship. 1B). The exhibition and historical excursus continue through the most important events and characters who, for over a century, have shaped Predazzo’s link with the geologic disciplines. 1C). At the end of this section are displayed some of the main scientific papers describing fossils collected in the nearby valleys.
Section 2. Geology of the Dolomites
2A). Key geological events that took place from the end of the Paleozoic (about 260 million years ago) and that have shaped the territory of the Dolomites – in particular the area now occupied by the Western Dolomites, and most notably the Fiemme and Fassa valleys – are summerized in this section. In the Paleozoic this area was part of a large emerged landmass, which was inhabited by various plants and terrestrial reptiles. 2B). Between the end of the Permian and the early Triassic (ca. 250 million years ago), a vast marine ingression occurred: the species and geological finds shown are among the very few which survived the largest mass extinction documented in the whole of the Earth’s history, which took place at about this time. 2C). Soon after, however, a great explosion of life in the middle Triassic repopulated the seas, and contributed to the building of the gigantic submarine carbonate platforms that we still admire today petrified in the Dolomite peaks, and that are the result of an intense reef-building activity by organisms such as algae, molluscs and corals.
Section 3. A Volcano and its Minerals
3A). While carbonate platforms were growing all around, the area comprised between Predazzo and the mid-part of the Fassa valley was the centre of a massive volcanic event that involved also – at least partly – the most ancient rocks. Limestone and Dolomite were deeply transformed by a prolonged contact with the incandescent magma; traces of these events are still visible today in the area around Predazzo. 3B). The interaction between sedimentary rocks, incandescent magma and the hot fluids produced by the volcanic apparatuses originated a large variety of minerals that have attracted collectors and enthusiasts in these valleys for centuries.
Section 4. Mines and Miners
4A). Besides those of exclusive collective value, mineral deposits and ores originated by volcanic events also had an industrial value: near Predazzo, the deposits appear of little size and yielded small quantities of ore; this was nonetheless sufficient to give rise to a long and diversified history in the extraction activity of the local mines. Exploitation of the ores began in the Middle Ages and ended only in the middle of the last century.
The Geological Trail at Doss Capel
The texts that follow are taken from boards along circular geological trail at Doss Capel, one of the best locations to explore in the Dolomites, where to find out about the region's complex geology. The trail is best approaced by cable car (Passo Feudo cable car), otherwise there are trails from Predazzo and the valley floor, but the trek is long. An alternative is to drive to the Alpe di Pampeago, and approach the Dos Capel trail from there; the height difference is thus shortened. The trail is circular, but it can be made in sections too.
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 versus plutonism; the second prevailed. It paved the way for a modern understanding of the origin of rocks and the evolution of our planet. This is what the two theories, in a nutshell, said:
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.
3. The Origin of the Dolomites
But 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 tell 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 the Latemar (2,846 m; described below): every characteristic shape in the Dolomites’ landscape corresponds to a particular type of rock. 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. The 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 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, the Latemar (2,846 m) 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.
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