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A passion for trekking in the mountains is probably what made you discover the stunning Pale di San Martino, the beautiful Palaronda tours, and the Dolomites in general. But have you ever wondered what makes the Dolomite landscape so unique and what geological processes have shaped these extraordinary mountains, so much so that in 2009 they earned the prestigious UNESCO World Heritage Site status?
This page is dedicated to exploring the geology of the Pale di San Martino and the Dolomites. You can find here some basic information to help you imagine and better understand the geomorphological processes that shaped these natural wonders. Thanks to these insights, your Palaronda tours will be more complete, allowing you to observe the landscape of the Pale di San Martino from a new perspective, appreciating the geological and landscape features that make it unique in the world.
The Pale di San Martino Massif with its 240 km² is the largest mountain group of all the Dolomites, and is part of the geological sector of the Western Dolomites. Among its most famous peaks appear Cimon della Pala, known as the “Matterhorn of the Dolomites”, Vezzana, which at 3192 m is the highest peak in the Group, Rosetta, Pala di San Martino, Sass Maor, and Cima della Madonna, among others. The complex geologic history of the Pale di San Martino reveals a long succession of rocks, from the oldest to the most recent, emerging at the base of the white dolomite walls of the Pale, brought to light during long geologic time by the action of erosion.
Before we dive into the depths of the history of the rock layers that prelude the formation of the Pale di San Martino, let us pause briefly to talk about the most famous rock in this area, namely dolomite. Or should we more accurately speak of dolomites, plural? Well yes, because the rock that forms the majestic walls of the Dolomites is not all the same, and it has different characteristics depending on how it was formed. Click on the two tabs below to learn about the main differences between the two types of dolomites: the solid dolomites and stratified dolomites.
These are dolomites that are characterized by their massive appearance and lack of horizontal layering, resulting from massive coral reefs of the Ladinic (242-237 m.a.) and Carnic (228-216 m.a.) periods. These rock formations have developed in the shallows of a Caribbean-type sea, growing to thicknesses of more than 1,000 meters due to a constant lowering of the seafloor (subsidence). The resulting reefs gave rise to the majestic walls of the Pale di San Martino and other Dolomite groups, including the Catinaccio, Latemar, Sciliar, Marmolada, and Puez-Odle groups. In the first phase (Ladinic), the reefs grew mainly vertically (aggradation), and the resulting rocks are known as Schlern Dolomite. In the later Carnic phase, however, we see horizontal reef accretion (progradation), with reef development from the core toward the outer edges, giving rise to the Cassian Dolomite. Examples of these rock formations include the lower and massive part of the Sella, the Sassolungo group with the Sassopiatto that corresponds to the edge of the cliff and preserves its inclination, but also Lagazuoi, Nuvolau, Cadini di Misurina, and Monte Piana.
This dolomite system originated after the formation of the Ladino-Carnic coral reefs, along the extensive tidal flats at the edge of the Tethys Ocean. This sedimentary environment, different from the previously mentioned Caribbean-type sea, is characterized by sedimentation influenced by the ebb and flow of the tides (we have to imagine tides much larger than those in the Mediterranean Sea). This rock system is known as Main Dolomite, and is characterized by well-stratified rocks and a laminar structure. The formation of these rocks occurred in cycles known as peritidal cycles, characterized by alternating periods when the sea completely covered the reefs, with periods when the tide went from high to low. These rocks rise above 1,000 meters in the Eastern Dolomites (east of Rio Cordevole and Val Badia), giving rise to the famous walls of the Tofane, Cristallo, and Tre Cime di Lavaredo. In contrast, the Main Dolomite is less thick in the Western Dolomites. In addition, this formation is often characterized by the frequent presence of hematitic dispersions, which give reddish-brown hues to the rock.
An extraordinary aspect of how the Pale di San Martino and the Dolomites were formed is the fortunate combination of conditions that allowed the coral reefs to develop so impressively. Corals, the main builders of reefs, require not only clean water and tropical temperatures, but especially sunlight in order to thrive. To be reached by the sun’s rays, the seabed on which corals grow must be relatively shallow. How, then, is it possible to explain the enormous thickness reached by Ladinian reefs, which in some cases exceed 1,500 meters in height, as in the walls of the Agner? This was made possible by a steady process of seafloor lowering, known as subsidence, which has occurred slowly but continuously for about 5 million years. This phenomenon forced corals and other organisms to grow upward to reach sunlight, expanding “above” the remnants of their predecessors and contributing to the vertical growth of reefs (process of aggradation).
During this vast time span, we see the formation of the Southalpine Crystalline Basement, a very ancient rock substrate formed by metamorphic rocks. These rocks result from the transformation of preexisting rocks, known as parent rocks, which, through intense metamorphic processes, undergo significant changes in their structure. These transformations occurred during the ancient Hercynian orogeny, an intense geological event that caused the formation of major mountain ranges such as the Appalachians and the Ural Mountains. The reliefs of Cima d’Arzon and Scanaiol (feldspathic gneisses) and the Tognola-Tognazza ridges (quartz phyllites) are formed from rocks dating from this period.
During this period, the area was characterized by major explosive volcanic events , most of which occurred in a circular area 70 km in diameter called the Bolzano caldera. A layer of quartz porphyries is formed that reaches thicknesses of up to 2,000 m, such as those that make up the Lagorai Range, Cima Bocche and Col Margherita. This major layer of hard rocks is important because it will partially preserve the Western Dolomites from later tectonic deformation. Also dating from this period are the Val Gardena sandstones, reddish stratified rocks derived from the disintegration of preexisting porphyries, outcropping in the vicinity of San Martino and, ascending toward Passo Rolle, at the foot of the Tognazza porphyry wall.
In the terminal phase of the Permian, the region undergoes a gradual lowering, allowing the sea to penetrate, initially forming extensive lagoons, and then encroaching more and more into the region. The hot, dry climate causes intense evaporation in these lagoons, resulting in the deposition of layers of clay marls, limestones, and carious dolomites, which will form what is now known as Bellerophon Formation. Its characteristic chalk intercalations, visible along the Rio Marmor north of San Martino, at Malga Fosse and Valles Pass, are the result of this evaporitic environment. Here, water rich in calcium sulfate evaporated, causing gypsum to precipitate on the bottom. The formation is named after the gastropod Bellerophon, a widely distributed mollusk that inhabited the seafloor and whose remains can be found in the upper part of the formation.
Wiping out more than 90 percent of marine species and about 75 percent of terrestrial species, it was the most devastating mass extinction ever on the face of the Earth. The exact causes of this event are still debated among scientists today.
Dating from this period is the Werfen Formation, recognizable by its distinctive Crode Rosse (Red Rocks). These reddish-colored rock layers are visible below the “Pala Monda,” near Malga Pala, at the foot of Cimon della Pala, on the Venegia and Venegiota peaks, and around the Castellazzo. These are rocks resulting from the deposition of gray and reddish sediments of terrigenous origin by the action of the sea, which completely invaded the region during this period. Werfenian rocks are characterized by being densely layered, with numerous folds, even twisted folds, and are very landslide-like. In these formations, it is common to find so-called “ripple-marks,” or bottom prints left by wave movement, which give us a 250-million-year-old snapshot of the beach.
After the vertical uplift of the Western Dolomites that occurred during the Anisian, the early part of the Middle Triassic, which led to the erosion of the werphenian rocks and the formation of the Richthofen Conglomerates, another major change affected the region about 240 million years ago. At this time, the area lowers again, allowing the sea to return and create a Caribbean island-like environment. The warm, shallow waters of this tropical sea favor the growth of calcareous algae and organisms that build calcareous skeletons. The accumulation of this limestone contributes to the formation of the carbonate rocks of the Contrin Formation and Morbiach Limestones, which form the Castellazzo, the summit part of Cima Venegia and Venegiota, and outcrop at the base of Cimon della Pala above the Crode Rosse.
We have finally arrived at the period that interests us most, the Ladinian, during which the geological formation of the Pale di San Martino in the strictest sense, i.e., of the Schlern Dolomite. Keep in mind that at this stage, the dolomite area is located on the seafloor of a tropical marine environment, similar to that of today’s Maldives or Bahamas: a shallow sea floor with warm, clear, well-oxygenated waters and a tropical climate. In short, a perfect environment to encourage the proliferation of a wide range of organisms, such as calcareous algae, mollusks, corals, and sponges. Over the course of about 4-5 million years, the gradual accumulation of coral constructions, organism shells, shells, and calcareous algae gave rise to a set of massive coral reefs. It sounds unbelievable, but the most impressive of these reefs is the one you can see today along the Palaronda treks, namely the immense Pale Plateau and the majestic peaks that surround it. Now let’s see in detail, how the Pale di San Martino were formed.
An extraordinary aspect of how the Pale di San Martino and the Dolomites were formed is the fortunate combination of conditions that allowed the coral reefs to develop so impressively. Corals, the main builders of reefs, require not only clean water and tropical temperatures, but especially sunlight in order to thrive. To be reached by the sun’s rays, the seabed on which corals grow must be relatively shallow. How, then, is it possible to explain the enormous thickness reached by Ladinian reefs, which in some cases exceed 1,500 meters in height, as in the walls of the Agner? This was made possible by a steady process of seafloor lowering, known as subsidence, which has occurred slowly but continuously for about 5 million years. This phenomenon forced corals and other organisms to grow upward to reach sunlight, expanding “above” the remnants of their predecessors and contributing to the vertical growth of reefs (process of aggradation).
Remember the Bolzano caldera that gave origin to the Lagorai porphyries? Well, this is not the only volcanic phenomenon that has affected the geological history of the Dolomites. In fact, while coral reefs grew in the tropical seas, deeper down a huge fluid magmatic cluster formed. As the pressure increases, this magma slowly begins to push upward, injecting itself into the cracks in the overlying dolomitic rocks. These lavas, once solidified, gave rise to numerous strands of dark rocks, known as porphyritic strands, which you can observe along the Palaronda trails that pass near the Mulaz and Focobòn groups in the northern part of the Pale. It is at this stage that the two volcanoes of Predazzo and Monzoni are formed, whose million-year activity has produced large quantities of volcanic rocks, which lay on the slopes of the Ladinian coral reefs, sometimes even to the point of covering them. This phenomenon had the incredible effect of preserving them from erosion.
In the initial stage, the reefs were formed by limestone rocks. The dolomites we can admire today in the Pale di San Martino result from a process of chemical transformation of limestones, called dolomitization, made possible by the circulation of magnesium-rich waters, which allowed an exchange between dissolved magnesium salts and calcium carbonate in seafloor rocks, changing their chemical composition.. The Dolomites owe their name to the Frenchman Déodat de Dolomieu, who, more than two centuries ago, fascinated by the beauty of these mountains, collected several rock samples and noticed that they did not react to hydrochloric acid, unlike limestones. The analysis of his teacher, the Swiss De Saussure, made it possible to discover that this was an unknown rock composed of a double carbonate of calcium and magnesium, which was named “dolomite” in honor of its discoverer. On the Pale di San Martino we do not find more recent rocks, whereas this is not the case in other areas of the Dolomites, as illustrated in the two fact sheets on Dolomite types at the top of this page.
You have reached the final chapter of this long story, congratulations! You now possess all the information you need to be able to recognize the various rocks in the Pale di San Martino area as you hike along the Palaronda routes. However, there is one final missing piece, represented by a crucial event in Italian geological history, without which these rocks would not have become mountains: the Alpine orogeny. This process occurs as an effect of the convergent movement, to the point of collision, between the African plate, which included the dolomitic area, and the Eurasian plate. The enormous compressive forces generated by this event caused uplifts between three and five kilometers, giving us the breathtaking spectacle we can admire today. In the next part, you can learn more about the aspects related to the shaping of the diverse dolomitic landscape, which was created by the combination of orogenic and erosion forces. The latter, played an important role in carving the Dolomites into their hard, vertical morphologies as we can observe them today.
In addition to geological features, the Dolomites are also included among UNESCO World Heritage Sites for the uniqueness and complexity of their landscape. Whether you are an experienced expert of the Dolomites or it is your first time visiting these areas, you have undoubtedly noticed how these rocks are characterized by distinctive shapes, in which each mountain has its own well-defined individuality, which makes it easy to recognize and distinguish it from the others. The profile outlined by the Cimon della Pala from Passo Rolle, the vertical walls that form each slope of the Pala di San Martino, the numerous Tower Bells of Val di Roda, Sass Maor with the Velo della Madonna: each of these peaks stands out for its extraordinary individuality thanks to its complex morphologies, which reflect a long and intricate geological history. But how did such a complex landscape develop? You can find out in this final part, where you will understand how different rock types, from the hardest to the softest, behave and react differently to erosion and tectonic compressive stresses.
The hard rocks found in the Dolomites, such as the Sciliar Formation (Sciliar Dolomite and Marmolada Limestone), Cassian Dolomite, and Main Dolomite, are characterized by considerable resistance to erosion. Despite being exposed to the action of atmospheric precipitation, wind and glaciers, their massive structure makes them less vulnerable to rapid erosion. This leads to the formation of the typical steep profiles, the sheer and jagged shapes that characterize the Pale di San Martino. Their vertical walls also make them prone to collapsing landslides, which, although contributing to erosion, still preserve the mountain’s verticality. These rocks have their own way of responding to the extraordinary compressive forces of the Alpine orogeny-the collision of the African and Eurasian plates that resulted in the formation of the Alps. Because of their compact structure and very thick layers, these rocks tend to behave rigidly, splitting into numerous faults and fractures.
The numerous faults and fractures in the northern peaks of the Pale di San Martino Mountains cause the jagged aspect of their skyline.
Hard rocks tend to behave rigidly, forming faults and fractures in response to the compressive forces of orogenesis.
For example, the soft rocks found in this area are those characterized by dense stratifications in which different rocks alternate, such as the Bellerophon Formation, the Werfen Formation, and the Livinallongo Formation. These rocks are more degradable, and therefore erosion affects them more powerfully, resulting in gentle morphologies with rounded profiles and landscapes characterized by mild slopes. During orogenesis these rocks react to tectonic forces by deforming plastically, giving rise to evident folds. An example of this phenomenon can be observed at Malga Fosse di Sopra or Passo Valles, or at the Rio Marmol along the road from San Martino to Passo Rolle, where spectacular examples of these folds can be seen.
Mountains composed of soft homogeneous rocks, thus easily degradable, have slopes with gentle slopes.
Thickly layered rocks tend to deform into folds when subjected to the compressive stresses of orogenesis.
Imagine in an environment such as the Dolomites, where the alternation between hard and soft rocks is very evident, the creative ways in which erosion has operated, attacking the more degradable rocks more strongly and leaving the more resistant rocks in morphological prominence instead. During the most intense phases of Alpine orogeny, stiffer rocks therefore created important fault and fracture systems: as we have seen, these rocks do not form folds, but tend to fracture. These fractures in turn have effects on the action of erosion: along them, in fact, especially if they are vertical fractures, erosion acts more powerfully (for example, through the action of water, falling debris, and the action of glaciers). It is along these fractures that the most important gullies and valleys of the Pale Plateau, such as Valle delle Comelle, Valle dei Cantoni, Valle delle Galline, Val Grande and Val Pradidali will form. The formation of these gullies makes the peaks of the Pale group, with their towers and vertical walls, stand out even more.
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Browse through the sections of the page about geology and discover interesting anecdotes and insights into how the Pale di San Martino Mountains originated
