Breakthrough at the Gotthard: The longest tunnel in the world

Switzerland celebrates the breakthrough of its new record holder with great jubilation: On 15 October 2010 at 2.18 pm, the last centimetres of rock of the planned Gotthard Base Tunnel were broken through. The 57-kilometre-long tube runs deep through the rock of the Swiss Gotthard massif. Once completed, the tunnel is expected to cut travel time through the Alps by almost an hour.

Huge drill heads almost 10 metres in diameter have dug the tunnel into the mountain from two sides. At 57 kilometres, it will be the longest in the world. Its northern entrance is in Erstfeld in the canton of Uri, its southern portal in Bodio in the canton of Ticino. It will be supported by up to two and a half kilometres of rock. When the tunnel is opened to traffic in 2017, it will have cost a good nine billion euros.

What repeatedly complicates the construction work: different types of rock lie close together, from hard granite to soft slate. On 31 March 1996, disaster struck one of the tunnels: Thousands of cubic metres of soggy rock slurry shot out of a borehole into the exploration gallery and flooded it. Six workers who were nearby were unimaginably lucky: they survived without injuries.

The goal of the record-breaking tunnel is to reduce the number of lorries crossing the Alps in the future and to transport more goods by train. Because the journey time between Zurich and Milan will be about an hour shorter thanks to the railway tunnel. And because traffic across the Alps continues to increase, the next projects are already being planned: a 53-kilometre tunnel is to be built at Mont-Cenis between France and Italy, and another with a length of 55 kilometres at the Brenner Pass in Austria.

Tunnel records

The world’s longest railway tunnel to date is located in the north of Japan: with a length of almost 54 kilometres, the Seikan Tunnel connects the islands of Hokkaido and Honshu. Half of the route runs under the sea. The third longest tunnel is also under water: trains run between England and France through the almost 50-kilometre-long Eurotunnel under the English Channel. The world’s longest road tunnel is currently the Lærdal Tunnel in Norway with 24.5 kilometres. To ensure that drivers don’t get tired when driving through it, it is illuminated in a particularly colourful way.

Folded and reshaped – the formation of the Alps

Every year, Munich and Venice come half a centimetre closer to each other. That’s not much, but it is measurable. The fact that the German and Italian cities are very slowly moving closer together has to do with the formation of the Alps.

Compared to other mountains, the Alps are relatively young. Their history “only” began around 250 million years ago when a shallow sea formed between the continents of Eurasia and Africa: the Tethys. Rock debris and remains of living creatures settle on the seabed over a long period of time and become limestone.

About 100 million years ago, the African plate set off on its journey: It drifted northwards and pushed hard against the Eurasian continent. The pressure compresses the rock, causing it to fold up in waves. The individual folds can be as small as a few millimetres or as large as hundreds of metres. In some places, the folded layers push over each other like roof tiles and form so-called rock ceilings. Finally, magma also rises; namely at the moment when the African plate dives under the Eurasian plate. The rock is melted in the earth’s interior and rises upwards, but still cools below the earth’s surface. For this reason, the Central Alps consist, among other things, of the magmatic rock granite – in contrast to the limestone of the Northern and Southern Alps.

The folded area eventually rises above sea level under the great pressure. At first, the folded ridges still appear as elongated islands in the sea. But the archipelago is pressed further upwards and slowly pushes up into a high mountain range into which the rivers cut deep valleys. Large amounts of erosion debris are piled up in the Alpine foreland. During the cold periods, huge glaciers carve deep trough valleys and steep mountain flanks into the rock. It is only now that the typical high mountain landscape of the Alps is formed, which attracts us for hiking or climbing in summer and skiing in winter.

Until today, the African Plate is drifting northwards. That’s why the Alps are still being vigorously uplifted and compressed. This compression is the reason why Venice and the whole area beyond the Alps move a tiny bit closer to us every year.

Mountains on the move

Mighty and rigid mountains rise up into the sky. It seems as if nothing and no one can move them from the spot. But this is not true: mountains are constantly moving – but so slowly that we cannot see the change with the naked eye.

The reason for this: the plates of the earth’s crust move. And when two of these plates collide, the rock is compressed, pushed and piled up. Similar to a car accident, mountains fold up at the edges of the plates when they collide. Mountains and valleys are therefore a “crumple zone” of the colliding plates. However, this does not happen abruptly like in a car accident, but much more slowly than in slow motion. The result is folded mountains like the Andes in South America. There, the oceanic Nazca plate slides under the South American plate and squeezes the rock together with incredible force. In the process, the elongated mountains of the Andes pile up, stretching over a distance of 7500 kilometres. This makes the Andes the longest overground mountain range in the world.

However, there are also huge mountains below sea level. They run through the middle of the oceans. They, too, owe their existence to the moving plates. Where two plates move away from each other at the bottom of the ocean, magma from the mantle seeps through the oceanic crust. The hot rock cools on the seabed and piles up into mountains thousands of metres long: the mid-ocean ridges. Where the lava reaches sea level and rises above it, islands like Iceland are formed. These mountains, born in the sea, are the longest on earth. The Mid-Atlantic Ridge runs from north to south through the entire Antlantic – about 20,000 kilometres long.

What is rock?

In some places it peeps out from under a thin cover of plants, elsewhere it rises up as a steep rock face: the bare rock. It is the building material that makes up the earth’s crust and mantle. Rock, however, is not a uniform mass. Similar to a cake dough – only much harder – it is a mixture of different ingredients: the minerals.

Rock therefore consists of different minerals. Depending on their composition, the minerals combine to form certain types of rock. Granite, for example, is a rock that consists of the minerals feldspar, quartz and mica. The fact that granite is made up of different minerals is evident from the fact that it is speckled: it contains lighter and darker parts that owe their different colours to three different minerals. The darker parts come from the mineral mica. The quartz mineral often appears whitish to grey. The third mineral, feldspar, can take on all kinds of colours, even pink. Unlike the hard granite rock, the softer sandstone consists almost entirely of quartz. For this reason, sandstone looks more uniform than the speckled granite.

Almost all minerals arrange themselves according to a certain lattice pattern into uniform shapes, the crystals. For example, the mineral rock salt grows into a cube. However, the regular arrangement also results in other shapes with smooth surfaces, as can be clearly seen in a rock crystal. This consists of particularly pure and therefore transparent quartz. If, on the other hand, liquid is enclosed in the quartz, it turns a milky, cloudy colour. Geologists then speak of milky quartz.

High mountains and low mountains

The Feldberg in the Black Forest is particularly popular with winter sports enthusiasts. Because of its height of 1493 metres, it is a good place to ski. But the Black Forest, although it has high mountains, belongs to the German low mountain ranges. The Alps, on the other hand, are high mountains. But what is actually the difference between low and high mountains?

The simplest answer is obvious: they are distinguished by their altitude. High mountains start at 1500 – some say 2000 – metres above sea level. They are therefore mountains whose peaks rise far above the tree line. Another typical feature of high mountains is that they are formed by glaciers and have steep mountain faces.

Low mountain ranges, on the other hand, have neither glaciers nor steep flanks. Their landscape is rather hilly and rounded. This is because their formation goes back much further than that of the Alps. Originally, they too were piled up into high mountains – more than 300 million years ago. But unlike the Alps, the low mountain ranges have not been uplifted for a long time. They are only being eroded, their shapes ground round. Some of them have already been weathered and eroded to such an extent that only the hull remains of the former high mountains: the hull mountains. The Erzgebirge and the Fichtelgebirge, for example, belong to them.

During their long history, the low mountain ranges were constantly reshaped. Even the uplift of the Alps did not leave them unscathed. The forces of the colliding plates put the old hulls of the low mountain ranges under considerable pressure. Because of their great age, however, the rock had become so solid and rigid that it could not be folded any further. Instead, like a gigantic sheet of ice, it broke into huge floes. Some sank into the depths, others began to rise. Sinking floes became deep trenches, rising floes developed into plateaus. The landscape that emerged from this are fractured clod mountains like the Harz Mountains. Its highest mountain, the Brocken, is 1141 metres high. This is not enough to make it a high mountain range, so the Harz clearly belongs to the low mountain range.

Magmatic rocks

Granite is formed when molten magma solidifies as it cools. The dark mottled gabbro or monzonite are also formed from slowly cooling magma. When this process takes place deep inside the earth, geologists speak of deep rock, also called plutonite.

If, on the other hand, the hot rock mush penetrates outwards during a volcanic eruption and pours over the earth’s surface, it is called effusive rock or volcanite. Volcanites include light pumice, porous tuff or rhyolite, which was formed from the same material as granite but has a different structure and is less hard because it cools more quickly at the earth’s surface than granite at depth. Basalt is also a volcanic rock. Sometimes it solidifies into hexagonal, closely spaced columns that look as if they have been cast into shape. Basalt forms on the earth’s surface from the same mass as the gabbro in the depths.

Volcanites weather immediately after their formation, plutonites only when the overlying rock layers have been removed. Because both volcanites and plutonites became rock from cooled magma, they both count as igneous rocks.

Metamorphic rocks

It happens inside the earth: strong pressure and high temperatures cause the components of the rock, the minerals, to react with each other and transform. In this way, new rock is formed. Because the Greek word for transformation is “metamorphosis”, geologists also speak of metamorphic rocks.

A correspondingly high pressure occurs when two earth plates collide and one plate dives under the other. The rock is then squeezed together, as if in a huge press. A frequent result of such rock metamorphosis is blue slate. Its source rock is basalt or a rock with a similar composition to basalt.

Great heat also causes rocks to transform. For example, in the vicinity of a magma earth, it is baked like in an oven. Marble, for example, is nothing other than limestone that has been heated very strongly in the earth’s interior; during this process, new minerals form and the rock becomes harder. Sandstone also transforms at high temperatures, because its quartz grains then stick together: the original sedimentary rock becomes the harder quartzite.

Sedimentary rocks

Some rocks look as if they are striped. In the Dolomites, for example, such transverse bands are often clearly visible. Sandstone or limestone quarries also sometimes have similarly pretty patterns.

The “stripe design” is already created during the formation of the rock. The starting material is weathering debris that is carried away by water or wind. Rivers, glaciers and dust storms lose their power at some point: river courses slow down towards their mouths and eventually flow into the sea or a lake. Glaciers advance into warmer regions and melt. Dust storms also weaken at some point. Then they can no longer carry dust, sand and debris. The crushed rock that is dragged along settles. Over time, the deposited material forms an ever higher layer – the sediment. Especially on the seabed and on the bottom of lakes, where rivers wash up a lot of material, such sediments accumulate, including remains of dead animals or calcareous shells.

Gradually, different sediments are layered on top of each other. One layer may consist of sandstone, for example: In dry times, the wind has blown desert sand onto it. When the sea level rises again, this layer is covered by water: calcareous shells of marine animals sink to the seabed and deposit another layer on top of the sand. Over millions of years, the climate changed again and again, causing the sea level to fluctuate. This allowed different layers to be deposited.

Over time, the sediment cover becomes thicker and thicker. Under the weight of their own weight, the initially loose sediments are compressed more and more, small cavities disappear, the mass thickens. Further layers are deposited on top, the sediment becomes increasingly solid and finally, under pressure, sedimentary rock. In geology, this process is also called diagenesis. If, for example, the shells of tiny marine animals are pressed into stone, limestone is formed. Fine grains of quartz sand cement together under high pressure to form sandstone.

In addition to debris, dead animals, for example fish, also settle on the seabed. Sealed airtight, their bones and scales were preserved and fossilised. Such fossils have immortalised themselves in the stone. Millions of years later, they still reveal a lot about the time when the sediment was formed. This is why geologists can read the rock layers like a history book.

Dolomites declared World Natural Heritage

The Three Peaks, the Catinaccio and the Geisler Peaks – the steep rock formations of the Dolomites rise mightily above the otherwise gently undulating landscape. Because of their “unique monumental beauty”, the Dolomites have now been included in the UNESCO World Heritage List.

Their peaks rise into the sky like pointed teeth. Whoever visits the Dolomites walks over ancient coral reefs and scrambles right through the history of the earth. Like the entire Alps, the Dolomites began to rise and fold up from the seabed millions of years ago. Over time, wind and weather formed gentle slopes at the foot of their peaks. Today, cows graze here in summer.

Every year, thousands of tourists come to marvel at the fabulous landscape. Extreme climbers perform circus-like feats on the steep walls. The fairytale setting attracts not only hikers and mountaineers, but also celebrities: Hollywood stars like George Clooney and Tom Cruise have already descended here. And Reinhold Messner, himself born in Brixen, began his career as an extreme climber on the walls of the Dolomites.

The World Heritage Committee was also impressed by the grandiose nature: on 26 June, parts of the Dolomites were designated a World Heritage Site by UNESCO. This means that from now on the Dolomites are under special protection.

How the “pale mountains” became the Dolomites

The Dolomites are also called “pale mountains” because of their colour. The Ladins, the oldest inhabitants of the area, tell many stories about their mysterious mountains: there is talk of the dwarf king Laurin and his enchanted rose garden and of a dwarf people who have spun the peaks with threads of moonlight. This mountain landscape has always inspired the imagination.

The French geologist Déodat de Dolomieu, on the other hand, took a more sober view of its light-coloured rock. On closer examination, he found out that they did not consist of pure limestone, as had been assumed. The salt magnesium oxide also had a large share. The newly discovered rock of the mountain range was named after its discoverer Dolomieu: the dolomite. And the “pale mountains” turned – simsalabim – into the Dolomites.