Mountains on the moveGeology and Geography
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.
Hillary and Norgay conquer Everest!
For years they dreamed of it, for weeks they climbed: On 29 May 1953 at 11.30 a.m., the New Zealander Edmund Hillary and the Sherpa Tenzing Norgay reach their ambitious goal: they are the very first to stand on the summit of Mount Everest!
Since the beginning of May, a British expedition has been preparing for the summit attempt on the highest mountain on earth. A dozen experienced climbers, 35 guides and 350 porters with 18 tonnes of equipment have been on their way from Kathmandu to the foot of Everest since spring. A first assault on the summit will take place on 26 May. But the climbers Tom Bourdillon and Charles Evans fail due to a defective oxygen device: Shortly before reaching their goal, the two have to turn back.
This is the moment for Edmund Hillary and Tenzing Norgay, who wait for their chance at base camp. They are the second team to begin the dangerous ascent. On 28 May, they spend an icy night at an altitude of 8500 metres. The next morning at 4 a.m. they start their last stage: 350 metres of altitude and a vertical rock step still lie ahead of them – hardly manageable at this altitude. But at 11.30 a.m. they have actually made it: they are standing on the highest point on earth, the world is at their feet! Tenzing wraps his arms around Hillary. The New Zealander pulls out his camera to capture the situation: The “third pole” has been reached! After 15 minutes on the summit, the two heroes start the dangerous descent.
For a long time, the 8848-metre-high Mount Everest was considered impregnable. Many expeditions have failed on this notorious giant in the Himalayas over the past decades. The British George Mallory and Andrew Irvine might even have made it before Hillary and Tenzing. However, they died on the descent and remained lost. To this day, no one knows whether they actually stood on the “mountain of mountains”.
The stormy night before the summit storm
Before Edmund Hillary and Tenzing Norgay reached the summit of Everest, they spent a terrible, freezing night. Hillary described their incredible ordeal like this:
“The night was terrible. An icy storm swept over the highest peak on earth. Tenzing called it the roar of a thousand tigers. Incessantly and mercilessly the storm swept over us, howling and shrieking, with such force that the canvas of our pyramid tent rattled like rifle volleys. We were on the South Col, a godforsaken place between the peaks of Everest and Lhotse. Instead of abating, the storm was still gathering force, and I was beginning to fear that our flapping and creaking shelter might be torn from its moorings and leave us defenceless against the elements. To save weight, we had left the inserts of our sleeping bags behind, which now proved to be a grave mistake. Although I was wearing all my down clothing, the icy cold penetrated to my bones. A feeling of extreme fear and loneliness overcame me. What was the point of it all? You had to be crazy to do such a thing to yourself!”
After surviving the stormy night, the summit attempt was imminent: “We had no time to lose. I hit steps again and gradually kept a somewhat anxious lookout for the summit. It seemed to go on forever, and we were tired and already moving more slowly. In the distance, the bare plateau of Tibet spread out. I looked up to the right and saw a snowy bulge. That had to be the summit! We moved closer together as Tenzing tightened the rope between us. Again I hit a step in the ice. And the next moment I had arrived on a snowy expanse with nothing but air – in every direction. Tenzing quickly followed me and we looked around in amazement. With immense satisfaction we realised that we were standing on the highest point on earth. It was 11.30 a.m. on 29 May 1953.”
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 added to 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 scenery 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.
Birth of an island
30 kilometres south of Iceland, an island has been born from the sea. Since 14 November, a young volcano has been spewing fire and ash here. Its lava masses have already grown an island 40 metres high and a good 500 metres long.
White-grey ash clouds hang in the sky and darken it. Fine volcanic rock pelts the surroundings, each lava eruption is accompanied by thunder. The column of smoke caused by the volcanic eruption rises 10 kilometres into the air. And an island off Iceland’s south coast continues to grow in the process.
The eruption of the underwater volcano came unexpectedly, but not without precursors. Seismologists had already measured smaller earthquakes in the capital Reykjavik a week earlier – signs that something was happening at the plate boundary of the Mid-Atlantic Ridge. In addition, a research vessel had noticed that the sea was warmer than usual. And residents of the nearby coastal region thought they smelled hydrogen sulphide. When the volcano erupted on the seabed at a depth of 130 metres, it initially went unnoticed. Its explosions were attenuated by the water pressure. But as it grew, it approached the sea level and finally broke through it, spewing wildly. That was the birth of an island in Iceland.
The new island off the south coast already has a name: “Surtsey” after Surt, the fire giant. According to a Nordic legend, Surt hurls fire and destroys all life with his glowing sword.
How Iceland came into being
Iceland is actually nothing more than the culmination of a huge mountain range in the Atlantic: almost 20,000 kilometres long is the Mid-Atlantic Ridge, which stretches from north to south through the entire Atlantic. At the height of Iceland, the North American and Eurasian plates drift apart, by about two centimetres every year. Where they straddle, hot magma from the Earth’s interior rises to the surface. These volcanic eruptions have been piling up mountains under water for millions of years and caused Iceland to rise above sea level 17 to 20 million years ago. These volcanoes are still active today. And now they have once again given birth to an island: Surtsey.
Continents on the move
For a long time, it was thought that the earth’s land masses stood rigidly in place. Later it turned out: the opposite is the case. The continents of our planet are moving! Like huge ice floes, they drift in different directions, albeit not very fast. Their speed is about the same as the growth of a fingernail. But why are the continents constantly on the move?
The earth’s crust that envelops our planet is brittle and cracked. It resembles a cracked eggshell and is composed of seven large plates and many smaller ones. Some of them form the continents, others the ocean floor. These plates of the Earth’s crust drift around on a hot, viscously flowing rock mush and are driven by movements in the Earth’s interior, or more precisely: by currents in the Earth’s mantle. Experts also say: they drift. All these processes surrounding the movement of the Earth’s plates are called plate tectonics, and the movement itself is also called plate drift.
Where the individual plates border on each other, the Earth is particularly active. At some of these plate boundaries, hot rock from the Earth’s mantle penetrates upwards and cools down. New crust forms here: the two plates grow and are pushed apart as a result. In contrast, where two plates collide, the lighter of the two – the continental crust – is crumpled and folded into mountains. The heavier of the two – the oceanic crust – slowly disappears into the depths. The heat in the Earth’s interior melts its rock again. While the edge of the plate sinks into the depths, it pulls the rest of the plate behind it and thus additionally drives the plate movement.
Volcanic eruptions, earthquakes, long mountain ranges and deep ocean trenches accumulate along such plate margins. Most of the turmoil on the Earth’s surface is caused by the largest of its plates: it is the Pacific Plate, which is moving northwest at a rate of about 10 centimetres per year. Most of the earth’s active volcanoes are found at its edges, and violent earthquakes shake the region. Because of the frequent volcanic eruptions and quakes, this plate boundary is also called the “Pacific Ring of Fire”.
Where plates collide
When two vehicles collide, their sheet metal is crumpled together. Something similar happens when two plates of the earth’s crust collide. Then their rock is pushed together and very slowly folded into enormous creases – this is how fold mountains are formed. What the crumple zone is in a car accident, the mountain range is in a plate collision – except that a car accident takes place in a fraction of a second, whereas a plate collision takes many millions of years.
The Alps were formed in exactly the same way: Africa pressed against the Eurasian continent and folded up the mountains. The Himalayas in Asia and the Andes in South America also owe their origin to the collision of moving crustal plates.
In such a crash, the rock of the lighter plate pushes upwards, the heavier one sinks into the depths. This process is called subduction, and the area where the plate dives is called a subduction zone. Along these zones there are often deep gullies, which is why they are easy to recognise. The deepest of these is the Mariana Trench in the Pacific Ocean. This deep ocean channel is located where the Pacific Plate dips below the Philippine Plate.
The further the earth’s crustal plate disappears into the earth’s interior, the hotter it gets. The rock melts and magma forms in the depths. The growing pressure can force it upwards again. Where it reaches the earth’s surface, volcanoes spew lava and ash. There are whole chains of such volcanoes around the Pacific Plate, for example in Indonesia. Because one volcano follows another here, this plate boundary is also called the “Pacific Ring of Fire”.
Not only do volcanoes erupt at such plate edges. Often, the earth also shakes because the plate movement causes enormous pressure and growing tensions. As soon as these are discharged, quakes shake the earth’s surface. In Japan, for example, three plates meet at once: the Pacific, the Philippine and the Eurasian. This is why Japan is so often hit by violent earthquakes.
Where slabs diverge
A long deep crack gapes in the earth and grows wider and wider. Huge forces are tearing the earth’s surface into pieces: The East African Rift runs through the continent along this fracture. Africa began to break apart here 20 million years ago. Hot magma from the earth’s interior pushed upwards and tore the earth’s crust apart. Since then, the pieces of crust have been drifting apart, by about a centimetre every year. The fact that the earth is very active here can also be seen from the many volcanoes that rise along the trench. Should seawater penetrate at some point, the East African Rift will become an ocean. Something similar happened at the Red Sea. There, the African and Asian continental plates have been separating for 25 million years. The resulting rift was flooded by seawater.
Where continental crust breaks apart, a rift valley forms. In contrast, where oceanic crust pieces move away from each other, mountains grow on the sea floor: the mid-ocean ridges. They consist of magma that penetrates upwards from the Earth’s mantle through the oceanic crust. New plate material is formed here. It squeezes between two oceanic plates, so to speak, and solidifies into basalt rock that continues to pile up.
In some places, the mid-ocean ridges rise above sea level as islands. Iceland, for example, and the still young Icelandic island of Surtsey are nothing other than parts of the Mid-Atlantic Ridge. Due to the supply of solidified rock, the oceanic crust here is constantly growing. It not only grows upwards, but also to the sides. The two oceanic plates are pushed outwards. Because they spread apart in the process, this is also called a divergence zone.
In this way, new seabed is created and the ocean slowly widens – albeit only a few centimetres a year. But modern satellites can measure the continents with millimetre precision. From the movement, it can be calculated that the Atlantic has already become 25 metres wider since Columbus’ crossing in 1492.
But because the Earth as a whole is not getting any bigger, the increase in seabed must be compensated for elsewhere. This happens where oceanic crust submerges under continental crust: While the Atlantic continues to grow, the Pacific is slowly sinking under the plate margins of America and East Asia.
A constant race: Uplift versus erosion
The Matterhorn or Mont Blanc would actually be over 12,000 metres high today – if wind and weather hadn’t constantly been at their heels. For while the mountains are lifted by forces in the earth’s interior, they also shrink again at the same time: their rock is washed away and abraded by water, wind and frost. In the case of the Alps, uplift and erosion are currently in balance. They remain about the same height.
Unlike the Alps, the Himalayas grow about one centimetre in height every year. In this region, the Indian Plate pushes against the Eurasian Plate and continues to lift the Himalayas – so much so that ablation cannot keep up.
But there are also mountains where the folding is over – they are only shrinking. These mountains were formed over 300 million years ago, so they are much older than the Alps or the Himalayas. Many of our low mountain ranges belong to them, for example the Rhenish Slate Mountains or the Bavarian Forest. They were abraded over millions of years and are lower than 2000 metres today.
The “race” between growing and shrinking can also be observed in volcanic mountains: Extinct volcanoes are constantly losing height. The Kaiserstuhl on the eastern bank of the Rhine, for example, is highly weathered. Today, only ruins remain of the former volcano. Mount Etna in Sicily, Europe’s most active volcano, on the other hand, can suddenly grow several metres during an eruption. However, it also occasionally loses height again when the lava that has grown cold collapses.
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 pushed further upwards and slowly rises to form 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. Only now does the typical high mountain landscape of the Alps form, which attracts us to 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.
How do mussels and corals get into the Alps?
The Zugspitze, Germany’s highest mountain, is nothing other than a fossilised reef. If you climb it, you walk over ancient coral remains. Fossils like fossilised giant clams and ammonites can be found on the Dachstein in Austria or in the Dolomites. But: How did these remains of sea creatures get up to the highest peaks of the Alps?
Today’s Alps have risen from a shallow sea, the Tethys Sea. About 200 million years ago, this sea advanced northwards and covered parts of southern Germany. At that time, the climate here was tropical, much warmer than it is now. Today, the area would probably be a holiday paradise like the Maldives. At that time, however, no people lived here. Instead, the warm seawater was home to fish dinosaurs, shells, ammonites and corals. Their shells and carapaces were made of limestone and were deposited on the seabed after their death. Together with eroded rock debris, they formed a layer that became thicker and thicker over millions of years. Heat and pressure pressed the mighty limestone layers into solid sedimentary rock.
About a hundred million years ago, the African Plate began to move northwards. In the process, it pushed violently on the Eurasian Plate. This force caused the sea floor to unfold and be pushed higher and higher. From the bottom of the sea, the Alps gradually rose until they finally towered thousands of metres above the surrounding area. The reef remains and limestone layers from the sea floor became the Northern and Southern Limestone Alps. In the north they build up the Wetterstein limestone of the Zugspitze or the Dachstein limestone in Austria. In the Southern Limestone Alps, the steep cliffs of the Dolomites consist of ancient reefs. There, mountaineers and fossil hunters can still find countless ammonites and other fossilised sea creatures in the limestone. The Central Alps, on the other hand, consist of granite – a result of plate collision.
The snow-covered Kilimanjaro can still be marvelled at from afar. As a single mountain massif, it towers far above the African steppe – quite different from the typical fold mountains like the Alps or the Himalayas. This is because Kilimanjaro was not formed when the earth’s plates collided. About one and a half million years ago, several volcanoes erupted in the region in close proximity. From the lava masses, the mighty Kilimanjaro massif grew towards the sky. Today, its highest peak is Kibo at 5895 metres above sea level.
There are also volcanic mountains in Germany, for example the Siebengebirge near Bonn. 25 million years ago, several volcanoes became active here and hurled their hot rock masses to the earth’s surface. Today they are long extinct, but they are still clearly recognisable as mountains and hills of the low mountain range.
Incidentally, the longest mountain range on earth is also of volcanic origin – it lies submerged in the sea: the Mid-Atlantic Ridge stretches a full 20,000 kilometres through the middle of the Atlantic Ocean. The Mid-Atlantic Ridge is one of the mid-ocean ridges. These lie where two oceanic plates move away from each other. A fissure forms between the two plates at the bottom of the ocean, from which hot magma gushes. At such plate boundaries, long and high mountain ranges form under water. In some places, their peaks rise above sea level. This is where Iceland, the Galapagos Islands or the Azores see the light of day.
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