The Dolomites: when the Alps were a tropical sea

The Dolomites are legendary name to both mountaineers and geologists. The pink and beige mountains, with the characteristic layers, the free-standing towers with flat tables on the top, are on the UNESCO heritage list, and give dreamy eyes to those who study mountains, and to those who just climb them up or ski down.

Last fall, the dream became true. Me and the better half flew to Venice, rented a car and hit the autostrada to the north. Four lanes, two lanes, one and a half lane on the winding road, and after two hours we reached San Vito de Cadore.

A hotel room with a view… San Vito de Cadore, our base in the Dolomites.

San Vito looks like it comes straight out of Sound of Music, except the language is Italian and the food is pizza and gelato. Half an hour south of famous Cortina d’Ampezzo, San Vito lives on skiers in the winter and mountain walkers in the summer. We came in late September, the very end of the season, and felt a bit guilty for being the only guests at the hotel. It was their last week of opening, before closing for the fall, to fix all that needed fixing before the winter tourists were coming.

Our guilt vapored when we looked out of the window. There they were, the pink mountains, towering over the town. They looked just like in the pictures. And when the sun set, the famous Alpenglow colored the mountains in orange and red.

We were in the Dolomites.

Alpen glow: When the sun sets and paints the Dolomites in purple and orange.

Our plan was to both walk in the mountains and enjoy Italian food. But, thanks to the weather being as unstable as Italian politics, we spent the first days driving around. We stopped often, for stunning views, or to look at villages which looked like they were designed by and for Heidi.

First stop Cortina. Rumours on the internet say that Cortina in the high season is like a huge catwalk for pretty people with the latest in mountain wear. Outside of season, Cortina is more like an elegant lady, relaxing between the seasons of hard work. Cortina is well maintained, clean, tidy, with sports shops enough to serve the Olympics, but also a bit old-fashioned. The odd closed-down hotel suggest that she may no more be the latest it-girl of skiing destinations.

Which fit us perfectly.

Corso Italia, the main street in Cortina. catwalk in the season, just nice in the fall.

Up we go! Cortina viewed from the cable car up to Rifugio Faloria.

After some elegant cakes and cappuccino at Hotel Ancora, we took the cable car, the funivia, up to Rifugio Faloria at 2123 meters altitude. From there, Cortina looked like a one of the pretty villages on model railroad layouts. Alpen-style buildings, the church, the green fields and the rugged dolomite peaks around.

Dolomite. Dolomites. Dolomiti, Dolomiten. Dolomitis. There is lots of geology and history in a name. – what does it mean?

Cortina from the cliff edge at Rifugio Faloria.

Dieudonné Sylvain Guy Tancrède de Gratet de Dolomieu was born 1750 as the son of a French marquis in the Alps. After a military career, he spent most of his life studying the natural world, particularly geology and women. Dolomieu was interested in everything: volcanoes, minerals, and how the landscape changed with time. He believed the world was shaped through a series of ancient catastrophes, where water shaped the surface of the Earth.

Dolomieu did not make any great scientific discoveries. Politically liberal, he supported Napoleon in the wake of the French revolution. When a ship with him on board sought refuge for a storm on Sicily, he was taken prisoner of war, because Sicily was at war with France. He was not released until Napoleon took all of Italy in 1801. His health had taken such blows, that he died later the same year.

But he did get something that few geologists do: He got both a mineral and whole mountain area named after him. During travels in what was then part of Austria, but now is part of northern Italy (more on that later!), he noted that the limestone in these mountains did not dissolve with bubbles and fizz when put into hydrochloric acid. He published a description of the mineral and the rock it made up, and in 1792 they were named after him. Later, the whole mountain area of dolomite also got the name; the Dolomites became a brand in tourism.

Before we leave Cortina, we will take a trip on the geological museum. Yes, Cortina has a geological museum. It hosts the collection of Rinaldo Zardini, a native of Cortina. Born in 1902, his day time job was as a photographer, but his heart and boots spent most of his time in the mountains. Zardini walked the steepest edges and climbed the peaks hunting for fossils. His large collection contributed immensely to understand the rocks in the dolomites, and the environments when they were laid down. In 1975, Cortina town honored Zardini with opening the museum, dedicated to his collection of fossils.

This museum also tells the story of the rocks – when they were laid down, and why. We will go back 230 million years to tell our story, to the time we call the middle Triassic.

No, these are not aliens from outer space. They are big clams, which lived in the dolomite sea.

In the Triassic, northern Italy was tropical. Both because it was further south, and because the overall climate was warmer. The Earth was still in recovery from the great catastrophe twenty million years earlier, when around 85% of all animal species died out. The catastrophe marked the transition from the Paleozoic to the Mesozoic – from the “old time” to the “middle time” in Earth’s age. It probably happened because enormous volcanic eruptions in what is now Siberia burned through layers of coal and limestone, and released methane to the atmosphere, which in turn heated the Earth and almost shut down the circulation in the oceans.

At the dawn of the Triassic, Earth was a wasteland. Thirty million years later, recovery was on the way. The area around Cortina was a shallow sea, reclaimed by ammonites, fish and mussels. The sea was dotted with volcanoes, and these volcanoes created islands where trees grew. Today, we find their leaves as fossils, preserved by the fine volcanic ash. These rocks are called the Wengen group by geologists.

Intervals or groups of rocks usually get their name from places. As far as yours truly can find out, the Wengen Group comes not from the famous ski destination in Switzerland, but from the town La Val northwest of Cortina, in the province of Alto Adige – better known among apple lovers as Süd-Tirol, and which belonged to Austria before World War I. More on that later (teaser!).

229 million years ago, the volcanoes died out in the Cortina area. The sea rose, and Cortina ended up at the bottom of a five hundred meters deep tropical sea. The bottom of this sea was mainly boring mud, but life thrived around its rim: Corals, sea urchins, mussels, octopuses and the famous ammonites; the octopuses with spiral shaped shells. These rocks are soft, and today they are mostly hidden behind the scree and loose masses in the mountain sides. Their geological name is the San Cassiano Formation, after a village in Alto Adige, a.k.a. Sankt Kassian in Süd-Tirol.

Ammonites: The spiraled shells of octopuses from far back in time…

Four million years later, the sea fell again. The land emerged and forests of conifer trees conquered it. We know from fossil tree remains and pieces of coal – and some of the world’s oldest amber. Amber is hardened resin from coniferous trees, and famous as honey-golden jewellery, often with remains of insects and small animals inside. This old amber is far from that impressing: Brown and fractured dots in the rock. But, nevertheless, a greeting from a forest long gone.

Jewels from old trees: The brown spots in these rocks are some of the world’s oldest amber.

The forests lasted only a million years or so, before the sea once again rose and flooded the Cortina area. For the next ten million years, the sea laid down what was to become the signature rock of the Dolomites: the hard, layered dolomite, which makes up the magnificent cliff faces, which tower above the valleys. The dolomite is more than one kilometer thick, and its geological name is simply The Main Dolomite.

Limestones like this deposit in very shallow seas, where the tides may lay the land bare. Lots of light gives energy to the algae, which make fine particles of the mineral calcite, calcium carbonate. This limestone mud reacts with magnesium in the sea water, swaps half of its calcium atoms with magnesium and becomes dolomite.

How could the dolomite become so thick in a very shallow sea? It happened because the sea bottom sank in slowly, at the same pace the algae created rocks. By this lucky coincidence, the sea remained at around the same shallow depth for ten million years, building layer upon layer of rock.

Up close, the dolomite changes between thick layers of pure dolomite mud, often with large mussels called megalodonts, and layers with densely laminated mats of algae. It is the changes between these layers, which give the dolomites their characteristic cliff faces.

More than 200 million years ago, dinosaurs walked the shores in the Cortina area.

After nearly fifteen million years, the sea suddenly rose and drowned the Cortina area. At the same time, the climate went from dry to wet. The Main Dolomite deposited in a setting and climate like along the shore of today’s Arabian Emirates. The new climate was more more like Bahamas. Limestone continued to settle, real pure limestone this time. Waves washed across the sea bottom, making the sediments much more varied, and life flourished in the rich sea.

Further up in age and in altitude, the dolomites also have younger rocks, all through the Mesozoic. But for now, you know why the Dolomites are the Dolomites. Much later, the African plate with Italy as a ram buck in front, clashed into Europe, and pushed the Dolomites up, as part of the Alps.

The Zardini museum opened in 1975, and, although well maintained, it feels a bit dated and museum-ish. Nevertheless, it tells the story of the Dolomites very well. Interesting for us geo-geeks, and the nice fossils got admiration also from the muggle, a.k.a the better half.

How to get there:

The fastest way to get to the Dolomites is to fly to Venice, and drive straight northwards. The drive is around 1 hr 40 mins from Venice airport to San Vito, and allow for a short half an hour more to Cortina. Alternatives are to fly to Verona, or to Innsbruck in Austria.

One response to “The Dolomites: when the Alps were a tropical sea

  1. Pingback: Tre Cime de Lavaredo: The landmark of the Dolomites | Adventures in geology - Karsten Eig·

Leave a Reply

Your email address will not be published. Required fields are marked *