1 - Stratigraphy and Me. I imagine stratigraphy as a large book to leaf through, with thousands of pages and millions of words, symbols, and traces of previous readings and of previous readers. Pages that can be read by people who speak different languages, who are interested in different concepts expressed by the author, and who have very different skills of interpretation and different levels of education, and who are interested in different topics that are dealt with in the book. It is a book for readers who have experience in a variety of disciplines and who use the most advanced reading and comprehension techniques possible.
This book is to be read from the bottom up – from the last page to the first – because the layers of the subsoil accumulate one on top of the other and each one tells us about the process that created it, about the time when it was deposited, and about the climate, the environment, the plants, and the communities that wrote it. The gradual sedimentation of a new layer conceals and covers the information contained in the previous one, even though much of it remains within the same layer. We can imagine these layers as the pages of the book and the information contained in each layer as the written words, with the folds of the pages, the smudges of ink, and the erasures. As we go down into the subsoil, we can see that the pages are written in increasingly ancient periods and that if we compare “books” from different places, we will see that many more pages were written in some particular areas over a given period: this is where the geological processes were far more intense and thus left more traces. Our ability to read all the pages and to work out the real meaning of all the words depends on many factors.
One of the methods used to “read” the layers is that of comparing the sediments created by today’s natural processes with similar ones that we can see between the layers of the subsoil. If we look at them very carefully, we can see that they contain a lot of information that might be different from what we find today. For example, in the sediments deposited on the seabed we find that the sea was populated by species other than those we find now, that the environment was warmer or colder, or that the remains of plants or pollens in the sediments came from species that were different from the ones we find in the area today. Or that where a city now stands was once a swamp and, before that, that the area was covered by the sea.
Yet another problem is that of establishing the period when the various layers were formed. Stratigraphy enables us to establish which ones were deposited before and which ones came after, and this gives us their relative age. If we want to establish their absolute age, we can make a number of measurements: one of these is the analysis on the fossil remains of animals that lived only in a certain period, such as dinosaurs, and that left their traces among the rocks. Another is that of analysing objects whose age we know (such as ancient coins or vases and other objects that were produced and used by particular communities) and that were then buried by the deposits of volcanic eruptions. In these cases, the age of the subsoils can be considered as contemporary with, or later than, that of the objects themselves. Since the 1950s, other methods have been developed that make use of the presence of some radioactive elements in the rocks: these have a very precise decay history that can be measured in the laboratory. This gives the absolute age of the rocks, which is becoming increasingly accurate as we acquire greater knowledge and more advanced technologies for such measurements.
Let us now assume that we have studied the exact stratigraphy of the subsoil in a given area and that we have listed the events recorded in the strata. If we wish to compare the geological history of this place with others that may be close or far, we need to correlate the geological events of the individual areas. We will find that the same events were recorded at the same time in different settings: sedimentation in the sea, in lakes, or in alluvial plains, or areas of erosion, where the processes do not cause sediments, but remove the materials, thus possibly erasing the traces of previous events. These events can be synchronised by dating the strata or by correlating the sequences of rocks by using some elements they have in common. We can thus correlate similar and coeval levels, but in many cases we will see that, even in the same place, the strata may have slightly different characteristics, caused by small variations in the rock itself or in the environment where it was deposited. One example is that of lava flows that run down valleys, changing their characteristics very rapidly depending on their speed, on the presence of obstacles, of surface cooling and many other factors, even though they are all generated by the same magma. We could say that a lava flow is a single, consistent event, and one that is very rapid in geological terms, but if we look closely at how it moves – and the many videos of the flows on Vesuvius, Etna, or in Hawaii come to mind – we can see that each portion of the flow has its own story to tell: it may have hit a tree, covered a road, destroyed a house, or set fire to a wood, and just next to it, in the places it did not reach, there will be no trace at all of lava. Another example can be seen in volcanic eruptions – and particularly in large explosive eruptions such as the Plinian type. These eruptions create ash deposits that are spread over thousands of square kilometres. Their traces enable us to date the sequences of rocks in areas that are extremely far apart in a very precise manner. These deposits, which very quickly become sedimented in lakes, in the sea, in the mountains, in ice, in caves, and so on, allow to correlate – in other words, to regulate the sedimentation clock – over vast areas.
Let’s imagine we are observing strata from different parts of the world. We will discover that there are areas where some deposits cover huge areas, such as those of ash caused by large explosive eruptions – some may be very deep, while others will be very close to the surface, and in yet others they might not appear at all. This is because the geological processes that lead to the formation of the strata and their size can vary considerably in different depositional environments. For example, in an alluvial plain there will be thick deposits produced by flood waters that come one after another, covering the ash deposit we are studying, while on the surrounding hills this ash, if it is preserved at all, would be very close to the surface. But then, if we carry out our surveys in the sediments of a nearby lake, we will find that the layer of ash has been very well preserved and covered by the thin sediments of the lake. This means that depth alone is not enough to correlate events that took place at the same time in the past, so we need to synchronise our “clocks” correctly.
2 - Is stratigraphy an exact science? No! This negative answer is confirmed by my own experience, as well as by the advances in geological and volcanological studies that have been made in recent decades. Our ability to reconstruct geological history as indicated by the stratigraphy depends on:
- personal expertise,
- the complexity of the geological situation,
- advances in knowledge,
- the availability of new technologies,
- an understanding of past and present processes that form some deposits and similarities between modern and ancient strata, in their relative settings.
This means that our model – the history we read into the strata – will be the best summary possible today, making use of the knowledge and technologies we have at our disposal right now. If we analyse a rock, or a sequence of rocks and find a hypothetical process that has never been seen before by man, we may be led to adopt different interpretations about the stratum. We can, of course, apply new technologies or introduce new analyses that were not available before in order to increase our ability to interpret the strata correctly. Especially in the recent past, our interpretations have benefited from a multidisciplinary approach to sector studies. Different experts can read the same book and together grasp all the nuances of its content – just as different people looking at the same painting might be attracted by different aspects and be able to identify different elements: the painting technique, the style, the subject depicted, the context, the skill of the artist, and the materials used. All of this in a single image, which is the result of a complex, often unrepeatable process.
3 - An imaginary journey into the stratigraphy of a volcano. Also the history of a volcano is a book to leaf through. It contains traces of great eruptions, long periods of quiescence, low-energy eruptions, the interaction of the volcano with its surrounding area and, often, with the communities that have chosen the area around the volcano as a place to live and cultivate, and to build their villages and their cities, even though this may seem quite incomprehensible. But the reason is actually easy to understand, for most of the life of a volcano (such as Vesuvius) is one of long periods of inactivity that are often longer than a human lifespan. The great benefits of living in a volcanic area near the sea, however, have always been of great appeal to communities.
I leave Naples behind me and go up Mount Vesuvius. On my way, I come across many types of volcanic rocks: lava flows, banks of ash, layers of light-coloured pumice and dark scoria, and various types of tuff. And yet I can never work out when they were produced by the volcano and in what sequence. I would like to know the history of the volcano and imagine its eruptions. As I go up the slope, I find the road is becoming increasingly steep: I started out on the flat and now I’m climbing up a volcanic cone. I go all the way to the huge chasm of the crater. I look inside and recognise some of the rocks I saw on the way up. I see a sequence of banks of dark lava and layers of reddish scoria. In various places the volcano is emitting hot, acrid-smelling steam. I measure its temperature and find it is over 100 degrees Centigrade. I look at my geological map and I realise that the rocks I have seen are very young, just a few hundred years old. They were produced by eruptions of low explosive power, like those of Etna: lava flows, lava fountains, and Strombolian explosions. The last one was in March 1944. The explosions that came in the most intense phases of the eruption formed the large crater I see before me, which is more than 300 metres deep and 700 wide (Fig. 1). I’m intrigued by a little building on the opposite side of the crater rim, and from a distance I can see it has a sign, but I can’t read it. I go up closer and then I read: ascensore stratigrafico – macchina del tempo(“stratigraphic lift – time machine”). That’s curious – I didn’t know about this new invention. I cross the threshold of the little building and find I’m on the top floor. The indicator light says 1944: we are on the layers produced by the eruption. The doors open and I see a push-button panel that has dates in place of floor numbers. I recognise them – they are the dates of the eruptions of Vesuvius.
Fig. 1. Crater of Vesuvius, with the rim of the caldera of Monte Somma behind.
In the lift cabin I see buttons with the dates 1906, 1631, 472, 79, 1900 BC…, with the bottom floor at 40,000 years ago. That must be the date when the volcanic cone of Monte Somma, the oldest part of the volcano, started to rise up.
I press the 22,000 button and enter a succession of lava and scoria flows. It seems to me that the volcano is much higher than it is now and there is considerable activity all around me. Something huge and catastrophic is happening: a Plinian eruption, but this is the first – the oldest. I can see an eruptive column rising to a height of at least 30 kilometres from the volcano, scattering ash and pumice over a really vast area. The eruption goes on for a few days and the quantity of material ejected is in the order of cubic kilometres – so much so that the magma chamber, which can’t be reached by the lift because its temperature has reached almost a thousand degrees, is almost completely emptied. A piece of the volcano – the highest part of the cone – collapses on itself and forms a caldera (Fig. 2). There are powerful seismic shocks, the ground never stops shaking, the air is unbreathable, there’s ash everywhere and it’s burning hot, but I’m curious, so I resist. I want to get to the end. I see that the highest part of the volcano has collapsed and disappeared. The volcano now has a large elliptical depression at its centre, with a steep escarpment all around. I recognise it – I was looking at that escarpment from the edge of the crater, before entering the lift (Fig. 3).
Fig. 2. A tentative reconstruction (in red) of the shape of the Somma before the caldera collapse 22,000 years ago. In the box, a bird’s eye view.
When I recover from the fright, I look at the push-button panel again and see that many of the buttons are lit up in green. They seem reassuring. I press one that doesn’t contain a date but a whole period, 6000-1950 BC. The lift takes me to the slopes of the volcano, and I look out over its lush green slopes. It’s not active now. There are cultivated fields all around me, with lots of animals, hunters, and farmers with ploughs being pulled by animals, while others are taking their flocks out to graze. Everything has changed since the devastation I witnessed earlier on: the volcano is giving back life, fertilising the soil, attracting communities. I take a closer look and discover that there are also streets and clusters of huts made of wood and straw (Fig. 4). I consult my geological map and leaf through the pages of the book, only to discover that all this won’t last much longer. The volcano is preparing for another Plinian eruption – the one that will take place at the end of the Early Bronze Age and that will devastate the entire area around the volcano for thousands of square kilometres, sealing everything I’ve seen underground for ever. Archaeologists and volcanologists will find traces of these ancient civilisations only 4,000 years later.
Fig. 3. The escarpment of the caldera on Monte Somma. The light grey lava flow of the 1944 eruption can be seen at the foot of the escarpment. The rocks produced during the ancient activity of Monte Somma, consisting of lava flows and scoria from low-energy explosive activity, can be seen in the escarpment, which formed as a result of the calderic collapse. At the centre is Punta Nasone, which is also visible in Fig. 1.
The eruption in the Early Bronze Age intrigues me. I’ve studied it, and now I want to see it live. I press the 1950 BC button with decision. The eruption doesn’t look that different from the one of 22,000 years ago: a high eruption column, only this time the ash and pumice fall towards the northeast, towards the area where Avellino will be built. Thick blankets of ash and lapilli are piling up on the ground. Many villages have already been destroyed, and the landscape is unrecognisable, the sky invisible. The eruption has already been going on for several hours: huge blasts, earthquakes, unbreathable air. But then suddenly it all becomes even more intense. I look towards the northeast, where things appear to be calmer, and I find there are whole communities fleeing, with their herds, small supplies of food and some valuables, many of them in bronze. They are moving northwest, going away from the volcano. They’re walking on the hot ash that’s just fallen, leaving their footprints behind. They move in groups, with adults, children, and animals. Many are dragging objects. Looking closer, I see they’re going past a village of huts that’s partially destroyed. Someone goes into a hut. Today, that village is just next to what is now the high-speed railway line and the holes for the hut poles, and traces of their escape and of the devastation can all now be seen, preserved in the stratigraphy of the eruption deposit (Fig. 5). The entire area around the volcano will remain almost uninhabited for a few hundred years.
Tired, but increasingly curious, I press the AD 472 button. The Roman Empire is almost coming to an end. The area is in decline and many of the sumptuous villas around the volcano are in a state of partial disrepair. There are a lot of seismic shocks, and there is no water in the Roman aqueduct leading down from the nearby Apennines. The walls of the houses, some of which have been abandoned, are beginning to collapse. The volcano is swelling, with magma welling up from the depths, and eruption is imminent. Massive explosions begin, and a mixture of fragments of magma and gas is ejected from the volcano conduit at supersonic speed, rising tens of kilometres into the atmosphere. Giant volcanic blocks and bombs are hurled from the mouth of the volcano, raining down like projectiles, smashing through roofs and penetrating the ground. The cloud fed by the column heads northeast, like that of the eruption thousands of years earlier, and it covers a vast area, with its centre over Nola. The amphitheatre, the basilicas, and the entire city are covered with a thick layer of lapilli. Suddenly the explosions no longer support the eruption column and it collapses on itself, generating scorching pyroclastic flows that run down the sides of the volcano all the way to the surrounding plain, submerging everything they encounter. Their temperature is extremely high – over 300 °C. A huge amount of ash and pumice ends up on the volcano, on the plain, and in the Apennines. The volcano has pushed out an enormous amount of steam, which condenses, creating heavy rainfall. The ash that has piled up turns into mud and begins to flow, flooding the plain. This muddy mass fills everything – valleys, streets, houses and monuments. The phenomena go on for many months, making a vast area around the volcano uninhabitable.
Fig. 4. Reconstruction of life in an Early Bronze Age village at the moment of the Early Bronze Age eruption of Vesuvius (modified from the cover of Il villaggio del Bronzo Antico di Nola, Litografia Sicignano, Pompeii, 2005).
I’m exhausted, so I press the 0 button, and come back out from the depths. I’ve come back to the present year. I meet my fellow volcanologists, who are surveying the volcano. They are installing stations to measure the gas that feeds the fumaroles, to record earthquakes, and to see if the volcano is changing shape, so that they can monitor its state. I look out at the volcano again. The traces of the last eruption, the one that came in 1944, are fading away. Vegetation is covering over the slopes of the volcano. I’ve already seen a landscape like this on my trip. The volcano is not extinct, but just sleeping right now. I’d love to have a lift that could take me up into the future, all the way to the next eruption, but I know that, at least for the moment, that part of the lift hasn’t yet been built.
Fig. 5. Footprints of people fleeing, left in the ash during the eruption of Vesuvius in 1950 BC.
1 - Stratigraphy na Mimi. "Ninafikiria ""stratigraphy"" kama kitabu kikubwa cha kurasa, na maelfu ya kurasa na mamilioni ya maneno, alama, na alama za usomaji wa awali na wasomaji wa awali." Kurasa ambazo zinaweza kusomwa na watu wanaozungumza lugha tofauti, ambao wanavutiwa na dhana tofauti zilizotajwa na mwandishi, na ambao wana ujuzi tofauti sana wa tafsiri na viwango tofauti vya elimu, na ambao wanavutiwa na mada tofauti zinazozungumziwa katika kitabu. Kitabu hiki ni kwa ajili ya wasomaji ambao wana uzoefu katika taaluma mbalimbali na ambao hutumia mbinu za juu zaidi za kusoma na kuelewa. Kitabu hiki kinapaswa kusomwa kutoka chini hadi juu - kutoka ukurasa wa mwisho hadi wa kwanza - kwa sababu tabaka za chini ya ardhi hukusanyika moja juu ya nyingine na kila moja inatuambia juu ya mchakato ulioiunda, juu ya wakati ambapo iliwekwa, na juu ya hali ya hewa, mazingira, mimea, na jamii ambazo ziliandika. Kujipinda kwa tabaka jipya huficha na kufunika habari zilizomo katika tabaka la awali, ingawa sehemu kubwa ya habari hiyo hubaki ndani ya tabaka hilo. Tunaweza kuwazia tabaka hizi kama kurasa za kitabu na habari iliyo katika kila tabaka kama maneno yaliyoandikwa, na folds ya kurasa, stains ya wino, na erases. "Kama tunavyoingia chini ya ardhi, tunaweza kuona kwamba kurasa zimeandikwa katika vipindi vya kale zaidi na kwamba ikiwa tunalinganisha ""vitabu"" kutoka maeneo tofauti, tutaona kwamba kurasa nyingi zaidi ziliandikwa katika maeneo fulani maalum katika kipindi fulani: hapa ndipo michakato ya kijiolojia ilikuwa na nguvu zaidi na hivyo iliacha alama zaidi. """ Uwezo wetu wa kusoma kurasa zote na kuelewa maana halisi ya maneno yote hutegemea mambo mengi. Moja ya mbinu zinazotumiwa "kusoma" tabaka ni ile ya kulinganisha sediments iliyoundwa na michakato ya asili ya leo na wale sawa ambayo tunaweza kuona kati ya tabaka za chini ya ardhi. Kama tutaangalia kwa makini, tutaona kwamba kuna habari nyingi ambazo zinaweza kuwa tofauti na zile tunazopata leo. Kwa mfano, katika matope yaliyowekwa kwenye sakafu ya bahari, tunaona kwamba bahari ilikuwa na spishi nyingine kuliko zile tunazopata sasa, kwamba mazingira yalikuwa ya joto au baridi, au kwamba mabaki ya mimea au chavua katika matope yalitoka kwa spishi ambazo zilikuwa tofauti na zile tunazopata katika eneo hilo leo. Pia, mahali ambapo jiji hilo liko sasa palikuwa na mabwawa, na kabla ya hapo, eneo hilo lilikuwa na bahari. Tatizo jingine ni kujua ni wakati gani tabaka mbalimbali zilifanyizwa. Utafiti wa stratigraphy unaonyesha ni aina gani za miamba iliyopotea na ni ipi iliyopotea baada ya miamba hiyo, na pia ni umri gani uliopo. Ili kujua umri wa wanyama, tunaweza kufanya uchunguzi wa aina mbalimbali, na mojawapo ni kuchunguza mabaki ya wanyama waliokaa katika kipindi fulani tu, kama vile dinosaurs, na ambao waliacha alama zao katika miamba. "Kama vile ""kuchunguza vitu ambavyo umri wake tunajua (kama vile sarafu za kale au vyombo na vitu vingine vilivyotengenezwa na kutumiwa na jamii fulani) na kisha kuzikwa na madini ya milipuko ya volkano.""" Katika visa hivi, umri wa subsoils inaweza kuchukuliwa kama kisasa na, au baadaye kuliko, kwamba ya vitu wenyewe. Tangu miaka ya 1950, mbinu nyingine zimetengenezwa ambazo zinatumia uwepo wa baadhi ya vitu vya mnururisho katika miamba: hizi zina historia sahihi sana ya uharibifu ambayo inaweza kupimwa katika maabara. Hii inatoa umri kamili wa miamba, ambayo inakuwa sahihi zaidi na zaidi tunapopata maarifa zaidi na teknolojia za hali ya juu zaidi kwa vipimo kama hivyo. Sasa hebu tufikirie kwamba tumechunguza stratigraphy sahihi ya chini ya ardhi katika eneo fulani na kwamba tumeorodhesha matukio yaliyoandikwa katika tabaka. Ili kulinganisha historia ya kijiolojia ya eneo hili na nyingine zilizo karibu au mbali, ni lazima tuunganishe matukio ya kijiolojia ya maeneo ya mtu mmoja-mmoja. "Tutaona kwamba matukio yaleyale yalirekodiwa wakati uleule katika mazingira tofauti: sedimentation katika bahari, katika maziwa, au katika nyanda za alluvial, au maeneo ya mmomonyoko, ambapo michakato haisababishi sediments, lakini kuondoa vifaa, hivyo uwezekano wa kufuta alama ya matukio ya awali. """ Matukio haya yanaweza kusawazishwa kwa kuchunguza tarehe ya tabaka au kwa kuhusianisha mfululizo wa miamba kwa kutumia baadhi ya vipengele wanavyokuwa na pamoja. Kwa hivyo tunaweza kuhusisha viwango sawa na vya wakati mmoja, lakini katika kesi nyingi tutaona kwamba, hata katika mahali sawa, tabaka zinaweza kuwa na sifa tofauti kidogo, zinazosababishwa na tofauti ndogo katika mwamba yenyewe au katika mazingira ambapo ilichukuliwa. Mtiririko wa lava unaoingia kwenye mabonde, unabadilika kwa kasi sana kulingana na mwendo wake, uwepo wa vizuizi, baridi ya uso na mambo mengine mengi, ingawa yote yanatokana na magma moja. "Tunaweza kusema kwamba mtiririko wa lava ni tukio moja, thabiti, na moja ambayo ni ya haraka sana katika suala la kijiolojia, lakini ikiwa tutaangalia kwa karibu jinsi inavyohamia - na video nyingi za mtiririko kwenye Vesuvius, Etna, au Hawaii zinakuja akilini - tunaweza kuona kwamba kila sehemu ya mtiririko ina hadithi yake mwenyewe ya kusema: inaweza kuwa iligonga mti, ilifunika barabara, iliharibu nyumba, au kuwasha moto kwenye mbao, na karibu na hiyo, katika maeneo ambayo haikufikia.""" Mfano mwingine unaweza kuonekana katika milipuko ya volkano <unk> na hasa katika milipuko mikubwa ya mlipuko kama vile aina ya Plinian. Mlipuko huo hutokeza majivu yanayoenea kwa maelfu ya kilometa za mraba. "Mafanisi yao yanatuwezesha kuchunguza mfuatano wa miamba katika maeneo yaliyo mbali sana kwa njia sahihi sana.""" Hizi amana, ambayo haraka sana kuwa sedimented katika maziwa, katika bahari, katika milima, katika barafu, katika mapango, na kadhalika, kuruhusu kulinganisha <unk> kwa maneno mengine, kudhibiti sedimentation saa <unk> juu ya maeneo makubwa. Hebu kufikiria sisi ni kuchunguza tabaka kutoka sehemu mbalimbali za dunia. "Tutagundua kwamba kuna maeneo ambapo baadhi ya amana kufunika maeneo makubwa, kama vile wale ya majivu husababishwa na milipuko kubwa ya mlipuko, baadhi inaweza kuwa ya kina sana, wakati wengine itakuwa karibu sana na uso, na katika wengine wanaweza si kuonekana wakati wote. """ Hii ni kwa sababu michakato ya kijiolojia ambayo husababisha malezi ya tabaka na ukubwa wao inaweza kutofautiana sana katika mazingira tofauti ya amana. Kwa mfano, katika tambarare ya alluvial kutakuwa na amana nzito zinazozalishwa na maji ya mafuriko ambayo huja moja baada ya nyingine, kufunika amana ya majivu tunayojifunza, wakati kwenye vilima vya karibu majivu haya, ikiwa yamehifadhiwa kabisa, yangekuwa karibu sana na uso. Lakini ikiwa tutafanya uchunguzi wetu katika matope ya ziwa lililo karibu, tutapata kwamba safu ya majivu imehifadhiwa vizuri sana na kufunikwa na matope nyembamba ya ziwa. Hii inamaanisha kwamba kina peke yake haitoshi kuunganisha matukio ambayo yalifanyika wakati huo huo katika siku za nyuma, kwa hivyo tunahitaji kusawazisha "masaa" yetu kwa usahihi. 2 Je, stratigraphy ni sayansi halisi? La, sivyo! Jibu hili la kukataa linathibitishwa na uzoefu wangu mwenyewe, na pia na maendeleo katika masomo ya kijiolojia na volkano ambayo yamefanywa katika miongo ya hivi karibuni. Uwezo wetu wa kurekebisha historia ya kijiolojia kama inavyoonyeshwa na stratigraphy inategemea: - utaalam wa kibinafsi, - utata wa hali ya kijiolojia, - maendeleo katika maarifa, - upatikanaji wa teknolojia mpya, - uelewa wa mchakato wa zamani na wa sasa ambao huunda baadhi ya amana na kufanana kati ya tabaka za kisasa na za kale, katika mazingira yao ya jamaa. Hii inamaanisha kwamba mfano wetu - historia tunayoisoma katika tabaka - itakuwa muhtasari bora iwezekanavyo leo, tukitumia maarifa na teknolojia tunayo kwa matumizi yetu sasa hivi. Kama sisi kuchambua mwamba, au mfululizo wa miamba na kupata mchakato hypothetical kwamba haijawahi kuonekana kabla na mtu, tunaweza kuwa na kuongoza kupitisha tafsiri tofauti kuhusu stratum. Tunaweza, bila shaka, kutumia teknolojia mpya au kuanzisha uchambuzi mpya ambao haukuwa inapatikana kabla ili kuongeza uwezo wetu wa kutafsiri strata kwa usahihi. Hasa katika siku za karibuni, tafsiri zetu zimenufaika na mbinu ya taaluma mbalimbali kwa masomo ya sekta. Wataalamu tofauti wanaweza kusoma kitabu kimoja na pamoja kuelewa nuances zote za maudhui yake - kama vile watu tofauti kuangalia mchoro huo inaweza kuvutia kwa mambo tofauti na kuwa na uwezo wa kutambua vipengele tofauti: uchoraji mbinu, mtindo, mada iliyoonyeshwa, muktadha, ustadi wa msanii, na vifaa kutumika. Yote haya katika picha moja, ambayo ni matokeo ya mchakato tata, mara nyingi unrepeatable. 3 - Safari ya kuwazia katika tabaka la volkano. Pia historia ya volkano ni kitabu cha kutafakari. Ina alama za milipuko mikubwa, vipindi virefu vya utulivu, milipuko ya nishati ya chini, mwingiliano wa volkano na eneo lake la karibu na, mara nyingi, na jamii ambazo zimechagua eneo la karibu na volkano kama mahali pa kuishi na kulima, na kujenga vijiji na miji yao, hata ingawa hii inaweza kuonekana kuwa isiyoeleweka. Lakini kwa kweli ni rahisi kuelewa sababu, kwa kuwa sehemu kubwa ya maisha ya volkano (kama vile Vesuvius) ni moja ya vipindi virefu vya kutofanya kazi ambavyo mara nyingi ni virefu kuliko maisha ya binadamu. Hata hivyo, faida kubwa za kuishi katika eneo lenye volkano karibu na bahari zimekuwa zenye kuvutia sana kwa jamii. Napenda kufurahia safari ya safari ya Naples na kupanda mlima wa Vesuvius. Katika njia yangu, mimi hukutana na aina nyingi za miamba ya volkano: mtiririko wa lava, mabaki ya majivu, tabaka za mawe ya rangi nyepesi na scoria nyeusi, na aina mbalimbali za tuff. Hata hivyo, siwezi kujua ni lini volkano hiyo iliwatokeza na kwa mfuatano gani. Ningependa kujua historia ya volkano hiyo na kuwazia milipuko yake. Ninapopanda mteremko, ninagundua kwamba barabara inazidi kuwa ya mteremko: Nilianza kwenye eneo tambarare na sasa ninapanda kwenye koni ya volkano. Nilikwenda hadi kwenye shimo kubwa la kreta. Ninaangalia ndani na kutambua baadhi ya miamba niliyoona njiani kwenda juu. Ninaona mfululizo wa mabwawa ya lava nyeusi na tabaka za scoria nyekundu. Katika sehemu mbalimbali volkano hiyo hutokeza mvuke moto wenye harufu mbaya. Kwa mfano, unaweza kupima joto la mwili na kuona kwamba ni zaidi ya digrii 100. "Nilipoangalia ramani yangu ya kijiolojia, niliona kwamba miamba niliyoiona ni ya vijana sana, na ina umri wa mamia machache tu.""" Zilitokezwa na milipuko yenye nguvu ndogo ya mlipuko, kama ile ya Etna: mtiririko wa lava, chemchemi za lava, na milipuko ya Strombolian. Mfano wa mwisho ulikuwa Machi 1944. Mlipuko huo ulifanyika katika kipindi cha nguvu zaidi na kuunda kreta kubwa ambayo ina kina cha mita 300 na upana wa mita 700. 1) Mimi ni intrigued na jengo kidogo katika upande kinyume cha makali ya kreta, na kutoka mbali naweza kuona ina ishara, lakini siwezi kusoma. Mimi kwenda juu zaidi na kisha kusoma: ascensore stratigrafico <unk> macchina del tempo(<unk> stratigraphic lift <unk> mashine ya wakati<unk>). Hiyo ni curious <unk> Sikujua kuhusu uvumbuzi huu mpya. Mimi kuvuka kizingiti cha jengo ndogo na kupata mimi ni katika ghorofa ya juu. "Nyota ya ""1944"" inaonyesha kwamba tunaishi katika safu ya ardhi iliyotokezwa na mlipuko huo." Milango inafunguliwa na naona ubao wa kubonyeza-bonyeza ambao una tarehe badala ya nambari za ghorofa. Mimi kutambua yao <unk> wao ni tarehe ya milipuko ya Vesuvius. Mchoro. 1. Uwe na mtazamo wa kweli Mlipuko wa Vesuvius, na ukingo wa caldera ya Monte Somma nyuma. Katika kabati la lifti kuna vifungo vilivyoandikwa tarehe 1906, 1631, 472, 79 na 1900 KK, na chini ya lifti kuna alama ya miaka 40,000 iliyopita. Ni wakati huo tu ambapo sehemu ya kale zaidi ya volkano ya Monte Somma ilianza kuibuka. "Kama unavyoona, ""22000"" ni kifungo cha kuingiza lava na scoria." Inaonekana kwangu kwamba volkano hiyo ni ya juu zaidi kuliko ilivyo sasa na kuna utendaji mwingi kuzunguka mimi. Kitu kikubwa na cha maafa kinatokea: mlipuko wa Plinian, lakini hii ni ya kwanza <unk> ya zamani zaidi. "Ninaona safu ya milipuko ikiinuka hadi urefu wa angalau kilomita 30 kutoka volkano, ikitawanya majivu na pumice juu ya eneo kubwa sana. """ Mlipuko huo unaendelea kwa siku chache na kiasi cha vifaa vilivyotupwa ni wa kilometa za kiunzi, kiasi kwamba chumba cha magma, ambacho hakiwezi kufikiwa na lifti kwa sababu joto lake limefikia karibu digrii elfu, ni karibu kabisa tupu. Sehemu ya volkano - sehemu ya juu zaidi ya koni - huanguka juu yake mwenyewe na kufanyiza caldera (Sura. 2) Kuna mshtuko mkubwa wa tetemeko la ardhi, ardhi haiachi kutetemeka, hewa haiwezi kupumua, kuna majivu kila mahali na ni moto mkali, lakini nina hamu ya kujua, kwa hiyo ninapinga. Nataka kufika mwisho. Ndio maana sehemu ya juu ya volkano hiyo imeharibika. Sasa volkano hiyo ina eneo kubwa la chini la mviringo katikati yake, likiwa na mteremko mkali kuzunguka. Mimi kutambua ni <unk> Nilikuwa kuangalia kwamba escarpment kutoka ukingo wa crater, kabla ya kuingia lifti (Fig. 3) Mchoro. 2. Uwezekano wa kupata Mfano wa mto Somme kabla ya kuanguka miaka 22,000 iliyopita. Katika sanduku, mtazamo wa ndege. Ninapopona kutokana na hofu, mimi kuangalia kwenye bodi ya kifungo tena na kuona kwamba wengi wa vifungo ni mwanga katika kijani. Wanaonekana kuwa wenye kutuliza. "Hii ni kwa sababu ya kuwa hakuna tarehe ya ""mwaka"" lakini ni kipindi cha miaka 6000 - 1950 KK." Lifti inanipeleka kwenye mteremko wa volkano hiyo, nami huangalia mteremko wake wenye kijani kibichi. Si kazi sasa. Kuna mashamba yaliyofunikwa karibu nami, na wanyama wengi, wawindaji, na wakulima wenye mashamba yanayovutwa na wanyama, huku wengine wakipeleka makundi yao malisho. Kila kitu kimebadilika tangu uharibifu nilioushuhudia mapema: volkano inatoa maisha tena, inazaisha udongo, kuvutia jamii. Nilipotazama kwa makini, niliona pia barabara na makundi ya vibanda vilivyotengenezwa kwa mbao na nyasi. 4) Mimi kuchunguza ramani yangu ya kijiolojia na jani kupitia kurasa za kitabu, tu kugundua kwamba yote haya si kudumu kwa muda mrefu. Mlima huo wa volkano unatarajia mlipuko mwingine wa Pliny, ambao utafanyika mwishoni mwa Enzi ya Mapema ya Shaba na ambao utaharibu eneo lote karibu na volkano kwa maelfu ya kilomita za mraba, ukifunga kila kitu ambacho nimeona chini ya ardhi milele. Wataalamu wa vitu vya kale na wa volkano wataona alama za ustaarabu huu wa kale miaka 4,000 baadaye tu. Mchoro. 3. Uwe na mtazamo wa kweli Mteremko wa caldera kwenye Monte Somma. Mtiririko wa lava ya rangi ya kijivu-nyeupe uliotokea wakati wa milipuko ya mwaka wa 1944 unaweza kuonekana chini ya mwamba huo. Miamba iliyotokezwa wakati wa shughuli za kale za Monte Somma, inayojumuisha mtiririko wa lava na scoria kutoka kwa shughuli za mlipuko wa nishati ya chini, inaweza kuonekana katika mwinuko, ambao ulijengwa kama matokeo ya kuanguka kwa calderic. Katikati ni Punta Nasone, ambayo pia inaonekana katika Fig. 1. Uwe na mtazamo wa kweli Mlipuko huo katika Enzi ya Mapema ya Shaba unanivutia sana. Nimeisoma, na sasa nataka kuiona moja kwa moja. "Kama unavyoona, ""Kufikia 1950 BC"" ni kitufe cha kuamua." Mlipuko huo haujatofautiana sana na ule wa miaka 22,000 iliyopita: safu ya mlipuko wa juu, tu wakati huu majivu na pumice huanguka kuelekea kaskazini mashariki, kuelekea eneo ambapo Avellino itajengwa. Vitambaa virefu vya majivu na lapilli vinakusanyika ardhini. Vijiji vingi vimeharibiwa tayari, na mandhari haijulikani, anga halionekani. Mlipuko huo umekuwa ukiendelea kwa muda wa saa kadhaa: milipuko mikubwa, matetemeko ya ardhi, hewa isiyoweza kupumua. Lakini kisha ghafula yote inakuwa kali zaidi. "Ninaangalia upande wa kaskazini mashariki, ambapo mambo yanaonekana kuwa ya utulivu zaidi, na naona jamii nzima zikikimbia, na makundi yao, na ugavi mdogo wa chakula na vitu vya thamani, vingi vyao vikiwa vya shaba.""" Wanahamia kaskazini-magharibi, wakiondoka kwenye volkano. Wanatembea juu ya majivu moto ambayo yameanguka tu, wakiacha nyayo zao nyuma. Wao husafiri katika vikundi, pamoja na watu wazima, watoto, na wanyama. Wengi wao wanabeba vitu. Ninapotazama kwa karibu, naona kwamba wanapita karibu na kijiji cha vibanda ambacho kimeharibiwa kwa sehemu. Mtu fulani anaingia ndani ya kibanda. Leo, kijiji hicho kiko karibu na kile ambacho sasa ni reli ya kasi na mashimo kwa ajili ya nguzo za nyumba, na alama za kutoroka kwao na uharibifu wote sasa unaweza kuonekana, kuhifadhiwa katika stratigraphy ya amana ya mlipuko. 5) Eneo lote linalozunguka volkano hiyo litabaki likiwa na watu kwa mamia machache ya miaka. "Nikiwa nimechoka, lakini nikiwa na hamu ya kujua zaidi, ninachoma kitufe cha ""AD 472.""" Milki ya Roma inakaribia kuanguka. Eneo hilo linaharibika na nyumba nyingi za kifahari zinazozunguka volkano hiyo zimeharibiwa. Kuna mlipuko mkubwa wa tetemeko la ardhi, na hakuna maji katika mfereji wa maji wa Waroma unaotoka kwenye milima ya Apennine iliyo karibu. Kuta za nyumba, ambazo baadhi yake zimetelekezwa, zinaanza kuporomoka. Volkano hiyo inaongezeka, na magma inatiririka kutoka ndani ya mlima, na mlipuko unakaribia. Mlipuko mkubwa huanza, na mchanganyiko wa vipande vya magma na gesi hutolewa kutoka kwenye mfereji wa volkano kwa kasi ya juu ya sauti, na kupanda kwa maelfu ya kilomita ndani ya angahewa. Vipande vikubwa vya mawe na mabomu ya volkano yanatupwa kutoka kwenye mdomo wa volkano, yakinyesha kama makombora, yakivunja paa na kupenya chini. Wingu hilo linatokana na mhimili wa volkano, na linaelekea kaskazini-mashariki, kama lile lililotokea maelfu ya miaka iliyopita, na linafunika eneo kubwa, likiwa na kitovu chake juu ya Nola. Jumba la maonyesho, makanisa, na jiji lote limefunikwa kwa tabaka nene la lapilli. Kwa ghafula, milipuko hiyo haitegemezi tena safu ya milipuko na huanguka juu yake mwenyewe, ikitokeza mtiririko mkali wa pyroclastic ambao hupita kwenye pande za volkano hadi kwenye uwanda wa karibu, ukizamisha kila kitu wanachokutana nacho. Joto la joto ni juu sana, zaidi ya 300 ° C. Mengi sana ya majivu na mawe ya mawe ya mawe huishia kwenye volkano, kwenye uwanda, na katika Milima ya Apennine. Volkano hiyo imetoa mvuke mwingi sana, ambao hufinyangwa, na kusababisha mvua nyingi. Majivu yaliyokusanywa hubadilika kuwa matope na kuanza kutiririka, yakifurika uwanda. Mkusanyiko huu wa matope hujaza kila kitu - mabonde, barabara, nyumba, na makaburi. Matukio hayo huendelea kwa miezi mingi, yakifanya eneo kubwa kuzunguka volkano hiyo lisiloweza kukaliwa. Mchoro. 4. Uwe na uhakika "Kutoka kwa ""Mkubwa wa Bronze"" na ""Mkubwa wa Bronze"" na ""Mkubwa wa Bronze"" na ""Mkubwa wa Bronze"" na ""Mkubwa wa Bronze"" na ""Mkubwa wa Bronze"" na ""Mkubwa wa Bronze"" na ""Mkubwa wa Bronze"" na ""Mkubwa wa Bronze"" na ""Mkubwa wa Bronze"" na ""Mkubwa wa Bronze"" na ""Mkubwa wa Bronze"" na ""Mkubwa wa Bronze"" na ""Mkubwa wa Bronze"" na ""Mkubwa wa Bronze.""" Mimi ni uchovu, hivyo mimi bonyeza kifungo 0, na kuja nyuma nje ya kina. Nimerudi mwaka huu. Ninakutana na wataalamu wenzangu wa volkano, ambao wanachunguza volkano hiyo. Wanasema kuwa wanajenga vituo vya kupima gesi inayotumiwa kuchochea mvuke, kurekodi matetemeko ya ardhi, na kuona kama volkano hiyo inabadilika umbo ili waweze kuifahamu hali yake. Ninatazama volkano hiyo tena. Mawe ya mlipuko wa mwisho wa mwaka 1944 yanaonekana kupotea. Mimea inazunguka mteremko wa volkano hiyo. Tayari nimeona mandhari kama hii katika safari yangu. Volkano hiyo haijazimia, lakini inalala tu sasa hivi. Ningependa kuwa na lifti ambayo inaweza kunipeleka hadi wakati ujao, njia yote hadi mlipuko ujao, lakini najua kwamba, angalau kwa sasa, sehemu hiyo ya lifti bado haijajengwa. Mchoro. 5. Uwe na mtazamo mzuri. Macho ya watu waliokimbia, yaliyosalia katika majivu wakati wa mlipuko wa Vesuvius mwaka 1950 KK.