Roberto Luciani
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Come, discover eruptions and lavas, ashes and plumes, dangers and hazards of the terrible and terrific volcanoes, with the help of peppy Prof. Pof and his comical assistants.
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Te s t s Quizzes Games F
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C.M. 92889M This edition is not for sale
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Roberto Luciani
s e o n a c l Vo us and
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ENOUGH IS ENOUGH 2
C’mon Trumpet, don’t you see there’s still some room?
I hate the seasonal wardrobe swap!
Done, guys! Till next spring we’re OK!
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Uh, uh... It looks like it’s going to...
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Hmmmppfff!!!
Quarrk?
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... blow up!!!
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Did anyone mention volcanoes? WOW, that was a regular volcanic eruption! Well, it was to be expected. I’ll have to buy a bigger wardrobe. But at least it was fun, and no one was hurt. Just think how dangerous it would have been if it had been full of magma like a real volcano! Better not to think of it. Or rather, let’s think of it! You know, volcanoes are really intriguing, and I’m sure that by the next page I’ll start to feel like learning more about them. But first let me introduce myself:
I’m Prof. Pof, Inventor and Genius!
Quark, quarrrrk!*
Perepe pepe!**
* Anna, assistant goose. ** Trumpet, assistant-in-chief.
Speaking of hard-boiled eggs... Would anyone like one?
ACNE PROBLEMS
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•The Earth’s inner core is tremendously hot, but it never melts. Why is this?
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Just like a hardboiled egg
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Mantle 2.900 kilometres thick! The hotter parts move outward, keeping the whole mantle in motion.
Crust seas and continents lie on it.
Core or Nucleus hard and very hot.
Outer nucleus liquid.
The Earth’s crust is not a single layer covering the entire Earth, but is broken up into very large isolated pieces, like the shell of my hardboiled egg. Each of these large pieces is called a plate. The enormous power of the up-and-down motions of the mantle, pushes the plates of the crust around. So the Earth under our feet is not standing still, but is moving very slowly! It also moves at the bottom of the sea, because the sea lies on top of the Earth’s crust. At some places, adjacent pieces of the crust pull away from each other; at other places they push against each other, crashing against or sliding under one another.
And now pay attention: sometimes, around the edge of the plates, the rock of the mantle or the crust begins to melt into magma. Magma is hot and light and tends to rise, filling any cracks and fissures that it finds on its way. Sometimes it finds a way up to the surface and then a new volcano is born.
Hello, baby!
At a snail’s pace Once upon a time the world looked like this:
And this is how it looks now:
At speeds between 1 and 15 centimetres per year, the continents broke off from each other, and went their own ways! Guess how many years it took for them to do it? Five hundred thousand years Five hundred million years Two hundred million years (Even now, while you are thinking, the plates keep on moving and there’s no knowing where they are going to end in the far off-future.) It took two hundred million years.
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And now here’s the best bit
C’mon, I’m not going to hurt you!
At the centre of the Earth, just as in a hardboiled egg, there is a hard hot core (the nucleus) surrounded by a liquid layer (the outer nucleus). Outside the nucleus is a very thick layer of dense rock, called the mantle, which behaves just like boiling putty. Around the mantle is a cooler crust; you are standing on it just now. Close to the nucleus the mantle is much hotter than near the crust: the whole mass is in perpetual motion, simmering slowly up and down, just like boiling water in a cooking pot.
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Things are usually less dense when they are hot and more dense when they are cold. The “putty” at the bottom of the mantle, and the water at the bottom of a pot are very hot, and so they tend to rise until they float near the surface. At that point they get colder and so they plunge again to the bottom, in a never-ending cycle of ups and downs.
The reason is that at the depth of the core the pressure is enormous. At these pressures the metal forming the nucleus becomes solid. It is a bit like squeezing a foam rubber ball in your fist: the harder you squeeze, the smaller and tougher the ball becomes.
Our old planet Earth is not a teenager any more, but it does still suffer from acne. Its pimples are the volcanoes. Mother Earth’s face is full of them, thousands in fact, even though most of them are under the sea. Now, how can it be that the Earth is covered with pimples? To discover why, I’m going to cut it in half.
A fiery iceberg
We’ll have to find a name for it!
What we see rising above the ground is only the tip of the volcano: just as the biggest part of an iceberg lies under the water, most of the volcano is hidden under the surface of the Earth. Volcanoes, like trees, have subterranean roots. It all starts underground. The molten rock (magma) comes up from the mantle (beneath the Earth’s crust) and piles up in a magma chamber: this is the volcano’s reservoir, which is connected to the Earth’s surface by a main conduit and often by other minor ones. The conduit leads to the crater of the volcano.
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I was just kidding! I’ll make a model instead, OK?
A volcano is an open window through which we can take a peek at Earth’s huge underground depths. We could never explore such a hole in person, because of the frightful heat: down there the temperature reaches thousands of degrees Celsius (°C). But, thanks to the volcano, the white-hot matter that has been locked up in the bowels of the Earth for millions of years rises towards us. And that comes in handy, at least for the time being! Now, you’ll want to know exactly what a volcano really looks like? To show you, I’ll cut it in half.
Smoke holes Openings through which vapour escapes.
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C’mon Anna, we need more tomatoes.
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Magma chamber Magma gathers in it before starting to flow out.
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Lava Lava is magma after it reaches the surface, both in its liquid state and after it has cooled down and solidified into rock.
Gas bubbles As magma rises towards the surface, the gases that are dissolved in it join together forming larger and larger bubbles.
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• Do we call it lava only when it’s hot? Yes Hot or cold, it’s always called lava No, the stuff is called magma when it’s hot and lava when it’s cold N° 2.
OVER AND UNDER THE VOLCANO
The Erupting Can A volcano is a very complex structure but a volcanic eruption is just like opening a fizzy drink can. If you take care not to shake the can, and open it gently, you’ll hear only a faint “psst” as the gas inside escapes quietly.
Crater
If you shake the can a bit, the gas will rise up inside the can, pressing against the cap. Then, when the can is opened, the gas spurts out, together with some liquid.
If you give the can a good shake, all the gas inside it will accumulate in big bubbles against the cap, straining to come out. When you open the can, there will be a regular explosive eruption: the gas will come out all at once and the liquid will gush out like a fountain. That’s pressure at work.
CONES, SHIELDS & DOMES
And that’s not all The world of volcanoes is extremely varied. There are exploding volcanoes, collapsing volcanoes, volcanoes growing inside other volcanoes (Vesuvius is, once again, an example), undersea volcanoes, and even volcanoes under the polar ice packs.
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A volcano is not a normal mountain that suddenly starts spouting fire because some magma has risen from the deep, boring a hole in it. A volcano is generally the result of an earlier initial eruption, followed later by many others. So they grow into hills or even mountains of varying height, according to how much lava, ashes and rocks these past eruptions have spat out. Each of these materials has particular characteristics, which pile up in a special way. That is why volcanoes can have many shapes.
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Small cones They are not very tall because they grew from the accumulated debris of a single eruption. They have a wide mouth (crater) and sloping sides.
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Layered Their other name is stratovolcanoes, because they grew from the lava and ashes accumulated in layers (strata) during several eruptions. Cone-shaped, with very steep sides, they can reach a great height; Mt Vesuvius in Italy is one of them.
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Shield volcanoes They are gently rounded and look like a flattened pudding or the shield of an ancient warrior. Volcanoes grow like that if the lava is very runny and flows away easily.
Dome-shaped Sometimes lava is slightly colder and becomes so thick and sticky that it barely runs; then it tends to pile up in a very narrow space, forming a sort of high, narrow, steep-sided cake called a dome.
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Calderas That’s the Spanish word for cauldron. Sometimes an eruption is so fierce that the magma chamber is completely emptied. Then the volcano above it isn’t supported any more and sinks down, creating a large cauldron-shaped depression. Some calderas are more than 20 km wide.
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Submarine Some islands, such as the Aeolians, are in fact volcanoes that grew from the bottom of the sea a very long time ago. To measure their true height you have to dive deep down to the bottom of the sea!
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•Are volcanoes to be found only on Earth?
No, there are volcanoes on other planets too! The tallest known, giant Mt Olympus, is on planet Mars. It is a shield 26 km-tall, higher than three Everests on top of each other! And its diameter is 500 km.
Wow, aren’t you a swell!
Lava puzzle Quick, before the volcano blows up! Help the lava to find the right way out.
Many kinds of eruptions
Oh no, he’s done another mess on the carpet!
Eruptions are classified as effusive or explosive according to their style, which can easily be recognised – even a very long time after the end of the eruption – from the kind of deposits left on the ground.
When volcanoes sleep peacefully, they all seem similar. But when they awaken and get down to work, well... that’s when you can appreciate the particular style of each. But what is the style of a volcano, exactly? In my opinion, its own unique way of erupting: fiercely, quietly, sluggishly, angrily… If you have to deal with one of these rock-and-fire giants, you’d better get to know its particular style as thoroughly as you can, because your own safety could depend on how well you know it. No matter how intriguing they seem, volcanoes are very dangerous creatures nonetheless. Hey you, listen to me, I don’t like your style, get it?
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Lava sprays are burning hot, of course, but normally they do not reach very far. At times you can even watch them as if they were a magnificent fireworks show... from a prudent distance, naturally! A river of lava will devour everything on its path, but usually it flows slowly enough to give you the time to run to safety.
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When magma is viscous and swollen with gases, the eruption becomes an explosive one. As they rise through the conduit, gases combine to form a kind of foam made of fast-swelling bubbles; the explosion of some of the bubbles makes the whole mass rise even faster. When finally this compound of gases and scraps of magma is ejected from the volcano, a column shoots up that may reach a height of tens of kilometres. As the column falls back over the volcano, it will form an all-engulfing pyroclastic flow. These mammoth grey clouds can seem harmless enough at first. But take care! They are extremely swift, heavy, frightfully hot and therefore incredibly dangerous.
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•Why do volcanoes erupt?
A matter of style Eruptions don’t always follow the same pattern! Sometimes lava is flung up in fountains or spewed down in flows running along the sides of the volcano. Sometimes the volcano ejects a mixture of ashes, gases, fragments of magma, chunks of rock, that form a tall column rising into the sky. A volcano can be hundreds of thousands of years old, and during this long life it can have eruptions of different shapes and sizes.
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Effusive eruptions When lava is very liquid and there is very little gas mixed with it, it flows down easily, following the
slope of the ground. Odd as it may seem, effusive eruptions are far less dangerous than explosive ones.
Explosive eruptions When small gas bubbles are trapped within the magma, their explosion can cause lava jets to gush up in fountains hundreds of metres high, or throw up bombs and ash sprays that will rain down all round the crater. Fiercer explosions can form an umbrella-shaped cloud of gas and ashes that first rises towards the sky to a height of many kilometres, then spreads out into the atmosphere until it becomes heavier than the air and falls down again in a “rain of ash” that will cover everything in a huge surrounding area, many kilometres in extent. Sometimes this rain is so thick that it darkens the sun; the weight of fallen ash can even shatter the roofs of houses. If the eruption column collapses, folding over itself, pyroclastic flows will be formed. Danger!
In any case, it’s always best to keep a safe distance away.
Because the pressure of the magma inside the magma chamber breaks the surrounding rocks Because the hot magma tends to rise to the surface Because the magma is swollen up by the gases trapped inside it
Congratulations! All these answers are correct.
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TELL ME HOW YOU ERUPT AND I’LL TELL YOU WHO YOU ARE
Milk or porridge? If magma is liquid, the gas bubbles inside it can easily reach the surface and the eruption takes the shape of a smooth flow of lava or lava sprays of middling height. Just what happens when a saucepan of milk boils over.
If magma is very sticky, the gas bubbles trapped within it can’t escape to the surface; they swell and swell until they explode, shattering the magma into pieces and causing matter to fly around. More or less as it happens in a pot full of bubbling-hot porridge.
OUT OF THE MOUTH OF THE VOLCANO 12
Volcanic rocks Don’t you dare do that again. Do you hear me?
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Scoria Dark-coloured, denser than pumice with only a few holes in it. Like pumice, it is produced by explosive eruptions. Unlike pumice, it does not float.
Obsidian A glassy stone, produced when magma congeals very quickly, after having lost most of its gases, and without having time to crystallize.
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There are so many kinds of lavas
Pumice A floating substance, with more air than stone in it, produced when magma congeals while still full of gas bubbles; the gas escapes, leaving lots of tiny holes in the pumice stone.
In their molten state, lava temperatures can rise to between 700 and 1200 °C (the oven in your kitchen at home does 250°C at most...). When they have cooled down, they mostly turn into basalt, a dark rock often found on volcano slopes. The Hawaiian people, who should know, divide lavas in two species, according to their... feet!
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Lava The product of effusive eruptions. The common kind comes from not very viscous magmas welling out in lava fountains or lava flows.
Eruptions suddenly throw open treasure chests buried within the depths of the Earth. Stupendous heaps of terribly hot molten substances that, once they have come to the light, cool down quickly into rocks of every description. But what exactly is the stuff that comes out of a volcano’s mouth?
Pahoehoe Can you say it? I’m not so sure; I believe this word means, more or less, “that-kind-of-lava-that-when-you-walk-on-it-barefoot-does-not-cut-your-feet”. Lava flows of this kind are smooth and slick, even if they sometimes congeal into folds or puckers resembling twisted cloths or knotted ropes.
Aa Try walking on this kind of lava with bare feet and you’ll soon understand why the Hawaiians call it that. This kind of lava is stickier than pahoehoe, and it advances slowly, block after block, propelled by new lava that has come out behind it. It solidifies into sharp-edged, spiky masses. Pahoehoes and aas can be produced by the same volcano and within a single lava flow.
There are many things that can be spewed out by a volcano. Let’s shrink down to their size with my Pof-shrinker and we’ll take a closer look at them!
Under Pof’s magnifying
When the material erupted by the volcano as incandescent magma cools down, it becomes rock. Magmas of the same composition can congeal into very different kinds of rock, such as obsidian and pumice stone.
Tuff Material borne along pyroclastic flows that sometimes compacts into porous stone, used as building material.
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A do-it-yourself volcano This is the recipe for creating your own volcano (but ask your parents’ permission first). You’ll need: 1 small plastic bottle, 1 funnel, baking soda, flour, sand, red food colouring and a plastic tray. Mix together the baking soda and flour in a dry cup.
Pour the mixture into the bottle with the help of the funnel. Place the bottle in the tray, pour some sand round it and dampen it with water.
Volcanic missiles Do you remember the explosive eruptions? Just like cannons, they shoot out ashes and stones of every size. Ashes The explosion of the gas bubbles enclosed within the magma pulverizes this magma into tiny particles (less than 2 mm long). These particles form volcanic ash, which the wind can carry away for thousands of kilometres. These ashes can even darken the sun. The plumes that are seen during eruptions are made of ashes too. Lapilli (“Little stones”) Larger fragments, measuring up to 6 cm. They shoot out high into the air and later fall down again in a wide area all around the volcano, and sometimes even very far from it. Bombs Fragments of magma that cool down into several shapes and sizes (they can be from 6 centimetres to several metres long). Cauliflower bomb Spindle bomb Bread-crust bomb
Cow-dung bomb (I’m not kidding!)
Mould the damp sand into a volcano shape around the bottle. Cover it up to its mouth.
Pour a few drops of red food colouring into a cup of vinegar.
Insert the funnel into the covered-up bottle, pour the red vinegar into it; remove the funnel. Have a good eruption! Vinegar and baking soda mixed together produce carbon dioxide that forces the flour to flow out just like lava.
FIRE UNDER THE WATER
A hot spot… even too hot maybe!
Hold on! I just discovered something absolutely unbelievable: most of the lava on Earth is produced... under the sea! Honestly, that’s how it is, but it’s not easy to understand. So let’s board the latest invention, the Pof-submarine, and we’ll see for ourselves!
Submarine eruptions Now I think I’m beginning to understand how it all goes... Do you remember the cracks on Earth’s crust? For most of their length, some 75.000 kilometres, they run on the bottom of the oceans! Magma leaks out endlessly from them, but it cools down as soon as it meets the water and hardens into stony heaps. The oceanic dorsal, the longest mountain chain in the whole world, was born like that.
Stay here, Trumpet, and keep an eye on the little Fire Spitter!
Magma brims out from around the edges of the crustal plates, slowly congealing into magnificent underwater ranges, up to 2.500 meters tall, and dreamlike sub-aquatic landscapes.
These black chimney stacks are really made by water at 350 °C; the water is dark-coloured because of the mineral substances dissolved in it, and piping hot from its closeness to the magma. In time the melted minerals compact into “chimneys” up to 10 meters tall. A nice warm haunt for many odd beasties, such as whole colonies of... tube-dwelling worms!
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Time passes, the plate moves taking the volcano away, the hot spot remains in place.
The old volcano dies from lack of fuel; over the hot spot a new volcano is born.
This volcano grew so tall that it rose above sea level, forming an island. In the far-off future, it may sink down, however, and leave an atoll behind.
When magma pours out from the volcano into the sea, its surface cools down suddenly, but inside it stays bubbling hot. It takes on the characteristic form of big pillow-shaped magma rocks.
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•What do the coral atolls of the Pacific Ocean indicate?
They mark the place where there is going to be a volcano They mark the place where there once was a volcano They mark the place of a hot spot
N° 2: atolls are coral colonies that have grown round the slopes of an ancient volcano. The volcano died and sank down under the eroding sea waves, but it left behind the coral reef which once encircled it.
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You can find volcanoes (and earthquakes, their close relatives) both above and below the sea. They are mostly grouped near the edges of the big continental plates which form the Earth’s crust. But it’s not always like that. There are a few places on Earth very far from any plate edge, but which have volcanoes in them just the same. They are called hot spots because they mark a place where the underlying magma found a way to bore a hole in the crust, spill out to the surface and build up a volcano. Now, this volcano stands over a plate that is in motion; the hot spot, on the contrary, stays still. What’s going to happen in a few million years? Let’s take a look.
Hot spots Red stars mark the hot spots that are the places in which volcanoes are born not because there the edge of a plate is nearby, but because there the magma is able to pierce the Earth’s crust. Point with a marker the hot spots of the following islands: Hawaii Galapagos Azores Reunion
Simmer down, I didn’t really mean to spank you!
A MOUNTAIN OF TROUBLES Ah, these volcanoes! As long as they remain asleep, they look as majestic as mythological giants; when they start sputtering lava jets around they are as good as a fireworks display; but when they really get going, they definitely become scary, and there’s no fooling around Yes, well, with them any more. Lots of dangers can arise from where are you a volcanic eruption, both directly and indirectly. Let’s hidden?! take a look at them.
This is something you must never forget: when a volcano gets going in earnest, it’s like the end of the world, quite literally. The forces unleashed by a volcanic eruption are enormous and uncontrollable. Their energy can be far greater than that produced by a nuclear explosion. What’s more, even if volcanoes can keep quiet as mice for thousands of years, when they suddenly wake up they can act with such speed that they leave no escape route for anyone unlucky enough to be nearby.
This is one danger I hadn’t thought of!
Lava flows As they proceed, they destroy everything along their way, but they leave you time to escape. They rarely go farther than the volcano slopes, at least in Europe!
200 to 500 km/h
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Bombs and ashes Volcanic bombs, sometimes very big, can hurt or even kill people and damage or destroy property around the crater. The ashes can interfere with your breathing, damage plants and cultivated land and even crush the roofs of buildings. If they reach the higher strata of the atmosphere they can influence the climate, by hiding the sun and causing the temperature to fall.
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Pyroclastic flows They usually travel very fast and can cover great distances in a short time, devouring, asphyxiating and burning down everything in their path. They are among the most dangerous of all volcanic phenomena.
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A fearsome force
Landslides Volcano slopes are often unstable, since they consist of rocks that are fractured and only loosely consolidated. The turbulence of the gases and magma circulating inside the volcano can also contribute to the formation of landslides, enormous masses of earth that bury everything standing in their way.
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Mudflows If it rains heavily after the volcanic ashes have piled up on mountain slopes, a fastflowing mixture of water saturated with debris can sweep down with destructive consequences. This can happen not only during an eruption, but even a long time afterwards, if there is heavy rain.
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Great eruptions There have been many awesome eruptions in the past. Some were so appallingly fierce that they altered the world climate for years; some destroyed islands or towns, killing thousands of people. Just think, the amount of stuff shot up in the air by each of these eruptions is measured in cubic kilometres (km3); that is, cubes one kilometre high, one kilometre wide, and one kilometre long. Trumpet was in a mischievous mood and has switched the clouds of some historical eruptions. Now try and put back each cloud on the right volcano.
79 AD, Vesuvius (Italy) 3 km3
1980, Mount St. Helens (USA) 1 km3
1815, Tambora (Indonesia) 150 km3
Tsunamis or seaquakes If great quantities of volcanic material tumble down into the sea during an eruption, they can give rise to gigantic waves that spread out at great speed. These can reach nearby and even far-distant coastlines and cause terrible devastation. The same thing can happen if there is a strong earthquake originating on the bottom of the ocean floor.
1991, Pinatubo (Philippines) 8 km3 Vesuvius 3), Mount St. Helens 4), Tambora 1), Pinatubo 2).
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Under Pof’s magnifying
Volcanoes do not use the same clock as we do. What I mean is, they aren’t pressed for time as we are. They have a much longer lifespan than us. A volcano can take very little time to be born, and even less to die; for instance, it can destroy itself in a catastrophic eruption. However, from its birth to its death there can be an interval of tens, hundreds, hundreds of thousands or even millions of years. During this time there will be periods in which the volcano is sound asleep, others in which it will doze, and every now and then it will wake up with an eruption; each eruption will make it grow and change shape.
Many millennia ago, there was no one to make a record of all these things. What can we do, today, to reconstruct the history of a volcano? What did Vesuvius or Etna look like in their youth? We have no pictures of them then! Luckily, however, we do have the volcanoes themselves. Volcanologists know that the volcano itself can tell us a great deal about its past. How can it do that? With its own language: the language of the rocks.
Reconstructing history To sum up, then, a volcano’s history is shaped by its eruptions. Nowadays, we can film eruptions and follow how a volcano changes shape by comparing pictures of how it looked before and after an eruption. But before the invention of photography, it was up to the ancient chroniclers and scholars to observe and describe volcanic eruptions as best they could, and leave a record of them for posterity. The earliest of these chroniclers was Pliny the Younger, who left us a fascinating report of the catastrophic eruption of Vesuvius in 79 AD that buried Pompeii and Herculaneum under a layer many metres deep of ash and lapilli, killing thousands of people.
Hot ash, burning lapilli, and that bloke down there looks rather like a pyroclastic flow. I’m really afraid this means...
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... quick, get a helicopter!!!
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Eruptions can happen very often or very rarely. Sometimes thousands of years may pass before there is one. Every time there is an eruption, however, the shape of the volcano will change a little. After a number of eruptions its shape may have changed a lot!
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Reconstruction of the original profile of the volcano: in the past an explosive eruption destroyed the original crater; later on the present volcano grew inside it!
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•Magma that is very viscous is less dangerous than magma that is very liquid. True or false?
Layers on layers Just like onions, many volcanoes are made up of layers. This one has six layers, one for each of its past eruptions. Paint each layer in the correct colour, starting from the oldest one upwards!
900 BC
1208 AD
1570 AD
Layers of rocks erupted at different epochs Analysis of the samples
Scientists examine the layers forming the volcanic cone. Those at the bottom are the oldest ones. Each layer of volcanic rock can tell many things about the eruption that produced it. For instance, a deposit of fine ash can only have been produced by an explosive eruption; a lava flow, on the other hand, hints at a quieter effusive eruption. By carefully and painstakingly comparing the information on the volcano’s past activity with its present one, scientists are able to reconstruct the volcano’s history and, so to speak, fill in its family album!
2006 AD
1814 AD 1200 AD
1 Yellow, 2 Red, 3 Pink, 4 Blue, 5 Green, 6 Brown.
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Rock language
Cheeeese!
False: the eruptions caused by viscous magma are more explosive, that is more dangerous for people.
FAMILY SNAPSHOTS
Please doctor, come quick! I think he’s got bradyseism!
LOCAL HEROES
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You know what? I inspected the continental plates into which the Earth’s crust is divided closely, and discovered that most volcanoes are placed either on the edges of plates, or very close to them. Of course that’s hardly surprising! After all, the spaces between plates are where magma can most easily rise to the surface. Now, Italy happens to be placed very close to an area where two major plates meet.
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Ischia
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Stromboli In olden times, this volcano was nicknamed the “beacon of the Mediterranean”, because it has Pantelleria never stopped erupting for centuries. Its activity is moderate, however, and rarely dangerous. With its red-hot lava fountains and the showers of incandescent lapilli it hurls towards the skies, Stromboli always offers a spectacular show, especially at night.
Lipari
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Vulcano Just like Stromboli, Lipari and the other Eolian islands, Vulcano is a volcanic island too. It last erupted in 1890 and it’s hard to say when the next eruption will occur: for the time being it is busy emitting gases and vapours from its many smoke holes. All the volcanoes in the world are named after it.
Etna The biggest volcano in all of Europe and one of the most active in the world. It has a complex structure, with many craters and cones, and a long and interesting history. It often spits out lava flows that pose a severe threat to the buildings on its slopes. Explosive eruptions are less frequent. Etna’s last eruption began in 2006.
The Phlegraean Fields caldera, near Naples, is especially renowned for an odd phenomenon, called bradyseism. Every now and then, the ground rises and subsides, “inflating” and “deflating” cyclically, according to what is going on below the Earth’s surface. Between 1982 and 1984, for instance, the ground rose 1.80 metres! After that, it gradually subsided again, though there have been a few periods during which it uplifted slightly: the last time this happened was in 2000, when it rose 4 centimetres.
The holes were made by shellfish, and they remind us that once upon a time the land dipped at least 7 metres under the level of the sea. The columns remained submerged long enough for the shellfish to dig their homes in them; then the ground rose again and gave us a true measure of past bradyseism.
3.012 m 3.350 m 4.011 m
The correct answer is 3.350 m.
Vesuvius This volcano has been formed within the caldera left by an older volcano called Mt Somma, whose crater collapsed long, long ago. Vesuvius is one of the most famous volcanoes in the whole world, because of its connection with the ancient Roman towns of Pompeii and Herculaneum. These towns remained buried under the Vesuvius eruption of 79 AD, and this preserved them almost intact for archaeologists to study many centuries later. Vesuvius is surrounded by densely inhabited towns and villages, which makes it the most dangerous volcano in Italy. It last erupted in 1944.
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An unsettled ground
No matter whether they are awake or asleep, all Italian volcanoes are to be found near the Tyrrhenian coastline. The active ones are coloured in red.
Italy is situated near the place where the Eurasian plate meets the African plate. These plates are converging (moving towards one another).
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•Mt Etna is the highest volcano in the whole of Europe. But how high is it?
Volcanoes Italian-style
Phlegraean Fields This is the name of a huge caldera filled with craters. Catastrophic eruptions followed by a series of minor explosive events were responsible for its creation in the very remote past. During the last Phlegraean Fields eruption, in 1538, a small new volcano called the Monte Nuovo (New Mountain) grew out of the ground in a single week. Nowadays there is no eruptive activity going on at this site. The caldera seems to be asleep but the ground moves frequently and it emits large quantities of gases.
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The fiery boot Italian volcanoes, like Italian pizza, are famous worldwide. Do you know where to find them? Colour the Italian regions where you can find the volcanoes described in the previous page.
If you visit the ruins of the Serapeum, a Roman temple within the ancient market of the town of Pozzuoli, you’ll see marble columns whose history demonstrates the meaning of bradyseism. These columns are full of little holes to a height of 7 metres. And yet it does move
Er… there is a risk? As you’ll have understood, volcanoes are here to stay. And some of them are very much alive! Scientists claim they represent a “great hazard”. Now, what I would really like to know is: isn’t it highly hazardous to live in the vicinity of these colossal flamethrowers?
Not only in name The name of the volcano on the island of Vulcano is… Vulcano! It was named after the Roman god of fire, Vulcan, the blacksmith whose forge the Romans believed was placed under the island. In their opinion, the eruptions, rumblings and sparks coming out of the volcano’s mouth meant that deep down in the bowels of earth, the blacksmith god and the Cyclops, his one-eyed helpers, were busy forging thunderbolts for Jupiter, the king of the gods.
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Reducing risk
Stay there and don’t move !
Let’s say you are at the zoo, in front of the lion’s cage. You know perfectly well that the lion is not a kitten, but a dangerous beast. However, as long as there are cage bars between you and it, you don’t run any risk from the lion. It would be quite another thing if you climbed over the bars and got into the cage. Don’t you think you’d be running some risk then? True, the lion could ignore you, or even give you a lick with its tongue, but... how can you be sure that it wouldn’t tear you to pieces?
Hazard relates to the likelihood that a volcano may erupt. It is higher for an active volcano than for a sleeping one. And if that active volcano is known to have had explosive eruptions in its past history, the hazard is even greater.
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Hazardous maths First of all, danger and risk are two different things. Even when we are speaking of volcanoes. Volcanoes are beautiful and dangerous, and it would be best to give them a lot of room in which to unburden themselves when they feel like it, without endangering anyone. In fact, however, many people choose to live right under a volcano, to build their homes and even their towns there, and to farm the land made fertile by the volcano’s ashes. Then there really is risk!
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What’s the problem? You can’t make head or tail of what I say? Come on now, this is easy as ABC, if you just follow me!
Exposure is a difficult word, but its meaning is plain: it counts the people, the houses, the fields and all the property situated close to the volcano, which for this reason are exposed to danger.
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Vulnerability is a really difficult word, but it means counting how many people, houses, fields etc. could be damaged by a possible eruption.
Do you want to know the result of all this maths? The result is that danger does not depend on us, but risk does. Against an erupting volcano, we can do practically nothing, because its force is immeasurably greater than ours. But we can do our best to reduce the risk. How? For instance, by keeping at a safe distance from volcanoes and trying to understand what may happen when they do erupt. To prepare for this eventuality we need, first of all, to know the volcano in our vicinity very, very well.
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•In case of an eruption, which volcano would cause the highest risk, Mt Etna or Mt Vesuvius?
Mt Vesuvius because huge numbers of people live close to it, which means both their exposure and vulnerability are extremely high.
THE RISK IS… MATHEMATICAL!
Who’s more at risk? There’s no doubt: this ancient volcano is going to wake up! As far as we know, it never had an explosive eruption before, but it often spewed huge rivers of lava. Which of the towns round it is going to run the greatest risk, in your opinion?
Cuddly-wuddly! A goo-goo-goo! Daddy’s little sweetie!
No, I’ve not gone raving mad, no matter what my cocky assistants think. A scientist never goes mad, he simply gets passionate about his studies. I’ve studied volcanoes for so long that I must have an attack of volcanitis. This is a common disease among volcanologists, the volcano experts. No matter how demanding and difficult their studies can be, they kindle a burning passion, that’s the proper word. Because let’s say it: volcanoes are maddeningly fascinating things. I know, I know you didn’t mean any harm!
The volcanologist’s job is an outdoor one. Volcanoes have to be watched closely: they are living beings, with phases of sleeping and of waking; they have calm spells, fits of anger and unpredictable whimsies. Eruptions are a godsend for volcanologists, because it is during an eruption that a volcano shows its real nature. An important part of the volcanologist’s job is looking out for the signals that predict an upcoming eruption and estimating if and when it’s likely to start. In this way it may be possible to reduce the risks to people and property.
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Collecting samples of gases to be analysed. Gases can be toxic and even deadly, so you must wear a gas mask.
Gathering lava samples and taking their temperature is hot work and requires special protective helmets and overalls.
Interpreting the seismic waves produced by artificial explosions, to find out at what depth there is magma and how much there is.
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•A volcanologist is:
An absorbing job
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Measuring the displacements of fractures. Volcanoes do not stand still; their movements provide very important clues for volcanologists.
Studying the pictures and other data transmitted by satellites that constantly monitor the volcanic zones, their movements and temperatures.
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Studying and classifying all the samples collected, just as doctors do for patients, helps volcanologists understand the present state of a volcano.
A volcano researcher A volcano scholar A volcano fan
Attention please: there’s a splendid eruption on volcano Poffelius. We shouldn’t miss this chance to study it from close up! But what a clutter in my workshop! Help me find at least eight things we’re going to need.
A little imagination helps volcanologists overcome obstacles! Remote-controlled machines or robots can carry out tasks too hazardous or even impossible for people – collecting hot ash samples, for instance, or measuring very high temperatures. That’s not only useful, it can be fun, too!
Drawing accurate maps of volcanoes and of the material that they expelled, then comparing these with older maps of the same area can show how volcanic activity has changed over the years.
Trying to understand the workings of volcanic eruptions. Computers can simulate certain kinds of eruptions, rather like forecasting weather by simulating the movements of hot and cold air masses.
Overalls, helmet, boots, geologist’s hammer, notebook, tape-measure, camera, compass and binoculars.
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Collecting samples of rocks and ashes: once analysed they will tell us when magma formed, at which depth and at which temperature.
Usually all these things at once!
I ❤ VOLCANOES
KEEPING WATCH
ALL IS WELL CONCERN
Be careful, As we already know, living near an active volcano, I’m keeping an eye on you! especially one with explosive habits like Vesuvius, is extremely hazardous. And yet, there are a great many towns flourishing round the feet of this “frisky fellow” that has, more than once in the past, laid waste everything within its reach. When will it wake up again? No one knows, but sooner or later it will happen. So, it is essential to keep a vigilant watch. In fact, Vesuvius, just like many other volcanoes on Earth, is under special surveillance, 24 hours a day.
ALARM
What is the volcano’s check-system telling us? Can we stay calm today or should we start worrying? The colour code will tell us what to do.
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In the control-room of the observatory these parameters are monitored constantly.
Another telltale sign is the changes in the gases emitted by the volcano. If they increase, or become hotter, or their chemical composition changes, then it’s worth watching out for danger. Smokehole emissions are checked frequently, so that any change is noticed as soon as possible.
According to the data the volcanologists have collected, the Civil Defence Department will issue an alert level. When the data point to a normal situation, all is well and there is nothing to worry about. If there is a slight change in the signals, a yellow level of alert is issued: there’s still no need to worry too much, as the situation could well go back to normal, but has to be closely watched in case of further developments. If the anomalies keep growing, the alert level turns to orange: now is the time to start worrying and the population has to be warned of possible dangers. But the real alarm is sounded only when the alert level turns to red: this means that unmistakable precursors have been detected and both seismologists and volcanologists agree that an eruption is likely to occur within weeks.
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Slight tremors can be the forerunners of an eruption. For this reason a network of strategically placed seismographs constantly monitors the movements underground.
The slightest changes in the shape of the volcano or deformations of the ground can indicate that something is happening inside the volcano itself. They are constantly and painstakingly monitored, not only at ground level but by satellites as well, via the Osservatorio surveillance centre.
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Watch out for the colour code!
Watch out for the signs! Vesuvius and the volcanic zones nearby, such as the Phlegraean Fields and the island of Ischia, are closely watched over by the personnel of the oldest volcanic observatory in the whole world. This is the Osservatorio Vesuviano, founded in 1841. True, not even the highly-skilled technicians and scientists of Osservatorio Vesuviano are able to foresee the future eruptions; but, thanks to a dense network of sophisticated instruments, they can catch the first hints that something is going to happen. It all depends on signals sent out by Vesuvius itself, the so-called precursors or forerunners.
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WARNING
Evacuation!
When the red level of alert is reached, the Civil Defence puts its emergency plan into action. This is a carefully thought out programme, prepared well before the emergency starts and detailing all that must be done. When an eruption is in the offing, the only thing to do is to get away. If Vesuvius were to give signs of an impending eruption, all the people living in the high risk zone would have to leave before the eruption actually started, taking shelter in other regions of Italy. By acting in an orderly fashion, according to a preconceived plan without giving way to panic, we can save lives, if not property. All this thanks to the implementation of the most advanced technology and to the cooperation of everyone involved.
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•Who’s going to erupt? Which of these volcanoes do you think is sending out the most alarming signals? Choose three.
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Forethought is the best thing!
6 1, 4, 6.
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Underground electricity In the depths of the Earth, there are many things, except light. There’s water, for instance. Hot water even, if you are in a volcanic zone. Mother Nature provides all this heating power free of charge, so it shouldn’t be wasted, should it? What? You tried throwing hot water on a lamp, and it didn’t light? You should have used the steam produced by the water. If you channel the steam into pipes leading to a turbine, that steam can be turned into electrical energy.
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There are two sides to every coin, even where volcanoes are concerned. We’ve spoken of their beauty and how dangerous they are, but that’s not the whole story. By now you’re probably thinking that it would be better not to live near a volcano at all. However, there must be some reason why so many people all over the world persist in living just there. In fact there are quite a few good reasons for such a choice. You see, when all is said and done, volcanoes can prove to be quite good fellows, in their way, and capable of doing very good things too.
Power cables
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Even if you don’t think so at first, volcanic ashes make excellent fertilizer, chock-full of mineral salts made to order for growing vegetables. That’s the reason why our volcanoes, from Campania to Sicily, are surrounded by lush countryside!
Magma that is not ejected in an eruption remains underground and cools slowly there. In this cooling process valuable minerals dissolved in the magma will coalesce into veins and lodes, creating true... mines!
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In volcanic areas, the water carried by underground aquifers is hot and can be used for heating purposes. Sometimes hot water gushes up as a geyser.
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Many volcanic rocks make good building materials, as they’re both tough and water-resistant. In the distant past, prehistoric men often dug their shelters in volcanic rock, since they found these shelters to be particularly comfortable.
Thermal springs, whose water is a known cure for many ills, are often the result of volcanic activity.
And finally, electricity can be generated by turbines powered by the steam rising from hot underground water.
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Deep hot water aquifer
Turbine. An engine driven by steam or water; it spins round and transforms the energy of water or steam into electricity.
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Subterranean water, when it comes close to magma, heats up and produces many curious phenomena! Can you recognize them? Hot spring Steam vent Smoke hole Geyser Thermal mud
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Steam
Prof. Pof’s conclusions Volcanoes are neither good nor bad; they are simply one of nature’s marvels. When the Earth was young, volcanoes helped shape most of it into the Earth we know today. As long as the Earth exists, there will be volcanoes at work on its surface. We have to learn to live with them, how to make the most of the gifts they provide us with and how best to protect ourselves from the dangers they represent.
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We forgot to find a name for the little chap. Would you like to choose one? A – Hot spring B – Steam vent C – Smoke hole D – Geyser E – Thermal mud
ROUGH DIAMONDS
HOW VOLCANIC ARE YOU ?
H. It is possible to forecast an impending eruption 1. Ì No, it’s never possible 2. Ì No, but there are some warning signals that tell us to be on our guard 3. Ì Yes, but we cannot predict the exact time
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Did Anna and Trumpet learn anything from our trip around volcanoes, I wonder? To gauge their progress I invented this test for them. Would you like to try it too? Find the correct answer to all the following questions!
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I. An eruption can be heralded by 1. Ì The vapours escaping from the smoke holes 2. Ì The emission of poisonous gases 3. Ì A change in the shape of the volcano
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J. There is nothing we can do to protect ourselves from an eruption 1. Ì True, we just have to resign ourselves to die 2. Ì False, we can protect ourselves with modern technologies 3. Ì False, we can try and run away as fast as we can
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B. The magma of a volcano accumulates 1. Ì In the lateral conduits 2. Ì In the volcanic cone 3. Ì In the magma chamber
A-2 / B-3 / C-3 / D-2 / E-1 / F-1 / G-3 / H-2 / I-3 / J-3
A. A volcano is 1. Ì A mountain in which underground magma has bored a hole 2. Ì A spot on Earth’s crust where underground magma comes to the surface 3. Ì A spot in the mantle where gases and molten rocks are particularly plentiful
Tot up your marks and discover how... volcanic you are!
C. Eruptions and earthquakes 1. Ì Never happen at the same time 2. Ì Always happen at the same time 3. Ì Can sometimes be related to each other D. The oceanic dorsal is 1. Ì An extremely long fault on the sea floor 2. Ì A submarine mountain chain created by the outflow of magma 3. Ì A range of Hawaiian volcanoes
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E. An effusive eruption is characterized by 1. Ì Lava flowing out and gushing up but no explosions 2. Ì Explosions and pyroclastic flows 3. Ì Explosions that throw up burning hot bombs and lapilli
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Active volcanoes • If you scored 8 to 10 points You have understood that volcanoes should not be taken lightly; in fact you know so much you should think of taking up volcanology as a full-time job.
Sleeping volcanoes • If you scored 4 to 7 points You know enough to show respect for these ancient lords of fire. Good for you!
F. Normally the eruptions of Mt Vesuvius are 1. Ì Either effusive or explosive 2. Ì Effusive 3. Ì Explosive G. Volcanic hazard is due to 1. Ì Volcanoes 2. Ì People 3. Ì Both
Extinct volcanoes • If you scored 1 to 3 points Lavas and craters are still a mystery for you. Are you quite sure you’re deaf to their fascination?
Sunken volcanoes • If you scored 0 points What a disaster, to recognize a volcano you’d need to stand on top of it when it starts erupting. But never mind: Trumpet’s score was the same as yours!
Books Violenti vulcani, Anita Ganeri, Salani, 2000 To have fun while you learn all there is to know about lavas and eruptions. I vulcani, Christine Gaudin, Larus, 2004 An illustrated volume with all the facts, with detailed chapters on the most famous volcanoes and their eruptions. Vulcani e terremoti, Robin Kerrod, White Star, 2006 Lots of amazing experiments to try out in school and at home. Catastrofi naturali, Vittorio Rioda, Giunti Junior, 2000 Catastrophic eruptions, destructive earthquakes and other spectacular disasters. Vulcani e terremoti, Susanna van Rose, De Agostini, 1993 All you need to know about volcanoes and their most intriguing features, with many informative pictures.
Websites
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www.ingv.it The Istituto Nazionale di Geofisica e Vulcanologia website; the pages of the Naples (Osservatorio Vesuviano, www.ov.ingv.it) and Catania (www.ct.ingv.it) branches offer a large selection of historical and geological information on Vesuvius, Etna and other Italian volcanoes, and an overview of the ongoing monitoring activities. This site is available in English and Italian.
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www.vulcanoetna.it Lots of pictures, videos and webcam introduce you to the biggest European volcano and its eruptions. This site is available in English, French, German, Italian. www.geologia.com/area_raga/raga_home.html Geology website for youngsters; includes a section on volcanoes. www.stromboli.net Pictures and videos of volcanoes from all over the world; includes an educational section, with a useful illustrated glossary. A five star site with a dozen or so references to volcanoes of the world! Has a glossary updated by the US Geological Survey Volcano Hazards Program. This site is available in English, German, Italian. www.protezionecivile.it The Italian Civil Defence Department website includes a section on natural hazards, addressed specially to children. This site also has a list of addresses for European Civil Defence Agencies (under “Links”).
Volcanoes are maddeningly fascinating things, as Prof. Pof says, and it’s not unusual if a volcanologist goes mad with an attack of acute “volcanitis”. We aren’t volcano-mad, however, but we decided to write this book because we wanted to know volcanoes better – and we wanted you to know them better too. The best way to protect yourself from the danger of volcanoes is to know them well. Volcanoes – just like earthquakes and other phenomena that are expressions of Planet Earth’s vitality – need to be studied very carefully and observed closely if we want to minimize the risks they represent for us. Volcanoes and earthquakes are really and truly an ever-present hazard, but we can find ways to reduce this hazard and protect ourselves from volcanic risk. And even this little book can help. R. Camassi, C. Nostro Coordinators EDURISK project, 2007 Editorial Project M. Cristina Zannoner, Rita Brugnara, Roberto Luciani
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Managing Editor Rita Brugnara Coordination and Supervision on behalf of the Istituto Nazionale di Geofisica e Vulcanologia INGV Romano Camassi, Rosella Nave, Micol Todesco Text and Pictures Roberto Luciani Graphics and page format Carlo Boschi Editing Fabio Leocata
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Scientific Committee Maria Luisa Carapezza, Lilli Freda, Roberto Isaia, Warner Marzocchi, Rosella Nave, Concetta Nostro, Caterina Piccione, Piergiorgio Scarlato, Micol Todesco Thanks to Federica La Longa, Massimo Crescimbene
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Translation Viviana Castelli, Moyra and Gaston Fischer
EDURISK means education in risk. Particularly seismic and volcanic risk, risks which people and things are exposed to because of earthquakes and volcanic eruptions. EDURISK is a pilot project for the preparation of educational tools and courses for use within school programmes aimed at lowering seismic and volcanic risks. Volcanoes and us is one of the educational tools created by EDURISK for use within the elementary school system.
INGV
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The EDURISK project is co-sponsored by the National Institute for Geophysics and Volcanology (INGV) and the Italian Department of Civil Defence.
www.giuntiprogettieducativi.it www.edurisk.it
© 2007 Giunti Progetti Educativi, Firenze / INGV, Napoli, Bologna First edition: January 2007, Original Title: Noi e i vulcani
Reprint Year 6 5 4 3 2 1 0 2012 2011 2010 2009 Printed by Giunti Industrie Grafiche S.p.A. – Prato
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