Dance on the volcano

It is the most active volcano on earth: Kilauea in Hawaii. Since 1983, it has been spewing lava from craters and fissures, creating a magnificent natural spectacle. Kilauea measures 1247 metres, and its older siblings Mauna Loa and Mauna Kea even tower more than 4000 metres above the sea.

It is about 200,000 years since Kilauea broke through the earth’s crust, 50,000 years ago it emerged from the sea. It is constantly growing due to its lava flows. At the same time, it keeps losing some of its mass due to landslides.

Kilauea – like the entire Hawaiian island chain – owes its formation to a hotspot. This hot spot in the Earth’s mantle melts the rock and forms a magma chamber. From time to time, a volcano erupts from here. Because the hotspot always remains in the same place, but the Earth’s plate slides over it, entire chains of volcanoes or volcanic islands are formed over a period of millions of years.

Since Kilauea’s lava flows relatively slowly and steadily at no more than 10 km/h, it is not particularly dangerous to humans. Nevertheless, several villages have fallen victim to it in the past decades, and more than 100 houses have been destroyed.

The tears of Pele

Wreaths of flowers, gin and cigarettes lie on the rim of Kilauea’s crater. They are offerings to the goddess Pele, who is very revered by the Hawaiians. The name Pele means “molten lava”. She is the goddess of fire and volcanoes. And sometimes the Hawaiians dance the hula for her on the edge of the volcano.

According to legend, the effervescent Pele created volcanoes with a magical staff; she found her abode in the crater of Kilauea. When the volcano spits fire, Pele sometimes appears in the glowing lava.

Volcano researchers also seem to be impressed by Pele and named lava rocks after the goddess: they use the term “hair of Pele” to describe long, hair-shaped volcanic glass. It forms when the volcano ejects lava fountains, which the wind pulls far apart before they get cold. “Tears of Pele”, on the other hand, are formed when lava drips down and solidifies into tiny, shiny black balls.

What do volcanoes look like?

A steep mountain, flames shooting into the sky, a dark cloud of ash above: this is what a volcano looks like in a picture book. But there are also very different volcanoes. The shape they have depends mainly on the lava that seeps out of the earth’s interior.

Thin lava flows quietly and evenly out of the crater. It cools only slowly and flows far apart. This creates extensive surfaces or flat mountains that look like large shields. This is how these volcanoes got their name: Shield volcanoes. Typical examples are the Hawaii volcanoes with their glowing lava lakes and diameters of up to 400 kilometres.

Viscous lava, on the other hand, does not get far – it sometimes gets stuck in the volcano’s interior and clogs it. Underneath, magma continues to push upwards. The pressure increases until the lava plug is blown out of the volcano like a cork out of a champagne bottle in a huge explosion. Scraps of lava and rock fly into the air and crash down on the volcano. A layer of ash descends onto the surrounding area. In the course of time, a pointed mountain of ash and rock debris piles up, growing higher layer by layer with each eruption. Well-known examples of these stratovolcanoes are Mount Etna in Sicily or Mount St. Helens in the USA. Because of their explosive eruptions, stratovolcanoes are particularly dangerous.

In addition, there are also volcanic explosions that take place underground. When hot magma meets groundwater at depth, the water vaporises abruptly. The resulting pressure is so high that the earth above is blown up. What remains is a hole in the earth’s surface shaped like a bowl or funnel, a maar. Water often collects in this crater, creating a maar lake, such as Lake Laach in the Eifel.

When the magma chamber is empty after a volcanic eruption, the volcano above can collapse. This creates a depression in the landscape, a caldera. The size of the caldera gives an idea of the dimensions of the collapsed magma chamber. Some are huge, like the caldera of the Ngorongoro in Tanzania with a diameter of about 20 kilometres. When magma rises again from the depths and emerges as lava, a new volcano is formed in the caldera; this is called a daughter volcano. Mount Vesuvius, for example, is such a daughter volcano: it was formed in the caldera of Mount Somma.

Where on earth are there volcanoes?

There are not volcanoes everywhere on Earth; they are distributed quite unevenly. The vast majority of them are located along the plate boundaries – where the Earth’s plates rub against each other, where one plate dips below the other or where they drift apart. At these fractures, hot magma from the Earth’s interior can rise to the surface.

A particularly large number of active volcanoes can be found around the Pacific Ocean, for example Mount St. Helens in the USA, Popocatepetl in Mexico and Bezymianny in Russia. They are all part of a chain of volcanoes about 40,000 kilometres long, the Pacific Ring of Fire. This is because all around the Pacific Ocean, the Pacific plate is sliding under other plates. As the Pacific plate descends, the earth’s crust is melted. Magma collects in these places and volcanoes form above it.

Volcanoes exist not only above but also below sea level – and most of them are still completely unknown to us. These underwater volcanoes are called “seamounts”. They include the volcanoes of the Mid-Atlantic Ridge, a huge underwater mountain range in the Atlantic. There, plates are drifting apart and therefore magma is constantly rising up there. Sometimes the volcanoes also reach the surface of the sea: in 1963, south of Iceland, a new volcanic island – Surtsey – grew out of the sea within a few months. Iceland itself was also formed by volcanism on the Mid-Atlantic Ridge.

The situation is quite different with the volcanoes on Hawaii: these lie far away from plate boundaries, in the middle of the Pacific Plate. But below Hawaii, the Earth’s mantle is particularly hot; this is called a “hotspot”, a hot spot in the Earth’s mantle. Here, hot magma rises upwards and can easily break through the crust – then a volcano is formed. When a plate of the Earth’s crust slides over a solid hotspot, a new volcano always bores through the crust. This is how a whole chain of volcanoes is formed, such as the island chain of Hawaii. There, the Kilauea volcano is active at the moment because it currently lies over the hotspot.

Useful volcanoes

Volcanic eruptions can kill people and devastate land. Despite these dangers, around one fifth of all people live near volcanoes.

There is a reason for this: the soils that form on lava rock and volcanic ash are often very fertile. Plants find many nutrients here. In the mild climate zones, fruit and vegetables grow particularly well on volcanoes. On the slopes of Mount Etna, for example, citrus fruits, figs, olives and wine thrive perfectly.

Volcanoes are also suitable as sources of heat and energy. In Iceland and New Zealand, people generate electricity and energy from the volcanically heated earth. And Icelanders use hot volcanic springs as thermal baths.

What is the difference between lava and magma?

Magma and lava actually refer to the same thing, only in different places: magma is located inside the earth, lava on the earth’s surface.

Magma is formed where the heat and pressure inside the earth are very high. There, the rock melts and a viscous rock mush is formed, the magma. The magma collects in underground cavities and flows upwards to the earth’s surface as the pressure rises. As soon as the magma starts to flow out of the earth during a volcanic eruption, it is called lava. Gases that were trapped in the magma can then escape into the air. Therefore, lava and magma differ in their chemical composition.

As long as the lava is hot, it is soft and malleable. At the earth’s surface, the lava slowly cools down and becomes solid. Afterwards, it can look very different, depending on where and how it flowed out of the earth: For example, when a volcano erupts under water, the lava cools down very quickly. It forms into shapes that look like lumps or pillows. This is why it is called pillow lava. Other lava flows look like long balls of wool and are therefore called knitted lava.

In the course of time, various rocks form from lava. Particularly thin-bodied lava becomes dark grey basalt after cooling. This rock is often used as paving stones for roads and paths. When lava is thrown into the air during a volcanic eruption and inflates like foam, pumice is formed. The trapped air makes pumice so light that a piece of it can float on water. Volcanic ash and volcanic dust that solidify become tuff. Many houses in the volcanic Eifel, for example, are built of tuff.

Volcanic Mountains

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. The mighty Kilimanjaro massif grew out of the lava masses. 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.

Buried alive!

At midday on 24 August 79 AD, the summit of the volcano Vesuvius explodes. The terrible volcanic eruption claims thousands of lives. Hail of rock, lava flows and ash rain bury the inhabitants of Pompeii beneath them. The two cities on the Gulf of Naples are completely destroyed.

Until 24 August, Pompeii is a flourishing trading city. The day begins sunny, crowds and noise reign in the alleys, merchant ships dock at the harbour. The inhabitants have no idea of the approaching disaster. They know nothing of the lava plug that has been blocking the exit of Vesuvius for centuries like a cork in a champagne bottle. A violent earthquake 17 years earlier had loosened this plug dangerously. When it came loose around noon on 24 August, it shot up into the air along with the top of the volcano with a tremendous bang – the beginning of Pompeii’s downfall.

Soon there is a hail of stones, a layer several centimetres thick forms on the roofs of the city. The boulders grow larger and with them the horror of the inhabitants. Fist-sized and red-hot pumice stones fall from the sky, smashing windows and roofs. The first fatalities occur. Violent earth tremors shake houses and streets. Many of the 20,000 Pompeians try to flee, others take refuge in the cellars. But their houses become a trap: the following night, Vesuvius spews out deadly gases that descend on the city. Anyone who inhales them suffocates in agony. In the course of the following day, three lava flows burn and bury everything that is left of the city. Finally, Vesuvius spreads a thick layer of ash over the already completely devastated city.

The neighbouring town of Herculaneum with 4000 inhabitants is also razed to the ground by the eruption.

Witness to the downfall

From Misenum, a harbour town 30 kilometres from Pompeii, the 17-year-old Pliny followed the volcanic eruption and the sinking of Pompeii. In a letter, he describes the course of the catastrophe and the death of his uncle. He was a Roman fleet commander and set off by ship to rescue people from Pompeii …

He hurried to where others were fleeing from and headed straight for danger […] Ash was already falling on the ships, hotter and denser the closer they came, and soon pumice and black, half-charred stones cracked by the fire. The sea suddenly receded and the shore became impassable due to a landslide. For a moment he was undecided whether to turn back, then he called out to the helmsman who had advised him to do so: “Fortune favours the brave, go to Pomponianus!”

Pomponianus is a friend of the uncle who lives in Stabiae. There too there is panic and people want to flee. Pliny’s uncle tries to calm them down.

In the meantime, from Vesuvius, in several places, wide hearths of flame and high columns of fire were shining, their radiant brightness intensified by the dark night.Together they discussed whether they should stay indoors or go outdoors, for as a result of frequent, strong earth tremors, the buildings swayed and seemed to sway back and forth as if they had been loosened from their foundations. In the open air, the raining down of glowing, but only light, pieces of pumice was a cause for concern.They put pillows over their heads and tied them with cloths; this offered protection against the falling rocks.

It was already daytime elsewhere, but there it was night, blacker and denser than any other night […] They decided to go to the beach and see for themselves from close up whether the sea was already permitting them to go out. But it still remained rough and hostile. There my uncle lay down on a spread blanket, asked for a sip of cold water now and then and took it. Then flames and, as their harbinger, the smell of sulphur chased the others into flight and startled him. Leaning on two slaves, he rose and immediately collapsed dead, presumably because the dense smoke took his breath away and closed his gullet […].

Chaos in the airspace over Europe

Following the eruption of Eyjafjallajökull on 20 March 2010, air traffic has been suspended in large parts of Europe. The eruption of the Icelandic glacial volcano had thrown a huge ash cloud kilometres high into the atmosphere. The volcanic eruption led to the longest-ever traffic ban in European airspace from 15 April 2010.

Tens of thousands of flights were cancelled, cargo containers remained on the ground, hundreds of thousands of passengers were stranded. Mattress camps were set up and calm returned to the airports. All of Europe seemed paralysed after the eruption of Eyjafjallajökull. Airlines suffered billions in losses due to the cancellations. Weeks before, slight tremors indicated that the volcano would soon become active. Until then, volcano researchers had classified Eyjafjallajökull as rather harmless. Its eruptions were rare and not particularly violent, but when the thousand-degree magma shot upwards, it hit the 200-metre-thick glacier. The ice evaporated abruptly, the magma from the Earth’s interior was atomised into powder and a cloud of ash was hurled seven kilometres into the air. At this moment, of all times, the wind shifted over Iceland: dust and sharp-edged rock grains contained in the air drifted towards Europe. This made them particularly dangerous for aviation. If an aircraft flies through such a cloud, the dust and grains of rock act like sandpaper. In the worst case, the engines are so badly damaged that they fail and the plane crashes. To avoid such a catastrophe, air traffic in Europe was suspended. After five days, the amount of ash in the air had decreased so much that most planes could take off again.

Sleeping brother

Eyjafjallajökull seems to have calmed down, but nearby its big brother is slumbering. The Katla volcano is only thirty kilometres away and has erupted much more violently than Eyjafjallajökull in the past. Experts warn of an approaching eruption of Katla.

The last one happened in 1918, when the volcano threw ice chunks the size of multi-storey houses into the air, leaving huge holes in the ground on impact. A wave of meltwater flooded an area of 200 square kilometres – the size of a small German town.

In the past, Katla used to spit fire about every 50 years, so it would be long past time for another eruption. Moreover, volcano researchers have found out that both volcanoes are connected: During its last two eruptions, Eyjafjallajökull “fired up” Katla underground, causing it to erupt.

However, there is no need to worry too much. The Katla volcano is more explosive than its little brother. But fortunately no people live in its immediate vicinity.

Explosion in the Eifel

Lake Laach glistens quietly in the sunlight. But the idyllic tranquillity is deceptive: 13,000 years ago, hell raged here on earth – this landscape is the result of a volcanic eruption. And scientists expect the Eifel volcanoes to erupt again. The only thing that is unclear is when …

The first volcanic eruptions occurred in the Eifel 600,000 years ago. The series began with the volcanoes in the Western Eifel: ash volcanoes, craters and maars formed here. Later, the volcanic area of the Eifel expanded to the southeast. After that, the volcanoes came to rest.

This calm ended, however, almost 13,000 years ago, with a bang: a huge explosion inside the earth tore a large hole in the landscape. Metre-high streams of mud rolled down into the valley. The Rhinelanders were taken completely by surprise by this catastrophe – this is shown by skeletons found in the layers of earth. Lake Laach was formed at the site of the volcanic explosion. The last volcanic eruption in the Eifel took place 11,000 years ago, when the Ulmener Maar was formed.

Smaller earthquakes between Lake Laach and Koblenz today indicate that the earth has not yet finally come to rest. The quiet bubbling in Lake Laach is also evidence of volcanic activity. The carbon dioxide bubbles that rise from the water here come from the hot volcanic underground. The Eifel is on the move – so will it soon surprise us with a new volcanic eruption? A question that even science cannot answer.

Ant alarm

Volcano researchers have observed the behaviour of ants and want to use it to develop an alarm system for volcanic eruptions. They believe that ants would notice an impending volcanic eruption at an early stage and leave their nests. They assume that the reason is that ants flee from the poisonous gases that escape during volcanic activity. Biologists, however, do not really believe in this idea: they have found that ants also move several times a year.

But the volcano experts continue their research and observe more than 2000 anthills in the Eifel. For although the Eifel is volcanic, there are only a few fixed measuring stations here that could warn of a volcanic eruption. And the volcanoes in the Eifel, the researchers suspect, will not sleep forever!

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 across 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.