 CHAPTER 22 VOLCANIC REGION On a scale which equals or surpasses that of the Andes is another line of volcanic action which commences on the north with the Aleutian Isles in Russian America, and extends first in a westerly direction for nearly 200 geographical miles, and then southwards with few interruptions throughout a space of between 60 and 70 degrees. This is the first line of volcanic action where it sends off a branch to the southeast, while the principal train continues westerly through Tsumbawa and Java to Sumatra, and then in a northwesterly direction to the Bay of Bengal. This volcanic line, observes Von Buk, may be said to follow throughout its course the external border of the continent of Asia, while the branch which has been alluded to as striking southeast from the Moluccas passes from New Guinea to New Zealand, conforming though somewhat rudely to the outline of Australia. The connection, however, of the New Guinea volcanoes with the line in Java, as laid down in Von Buk's map, is not clearly made out. By consulting Darwin's map of coral reefs and active volcanoes, the reader will see that we might almost with equal propriety include the Mariana and Bonin volcanoes in a band with New Guinea. Or if we allow so much latitude in framing zones of volcanic action, we must also suppose the new Hebrides, Solomon Isles, and New Ireland to constitute one line. The northern extremity of the volcanic region of Asia, as described by Von Buk, is on the borders of Cook's Inlet, northeast of the peninsula of Alaska, where one volcano in about the 60th degree of latitude is said to be 14,000 feet high. In Alaska itself are cones of vast height, which have been seen in eruption, and which are covered for two-thirds of their height downwards with perpetual snow. The summit of the loftiest peak is truncated, and is said to have fallen in during an eruption in 1786. From Alaska the line is continued through the Aleutian or Fox Islands to Kamptschatka. In the Aleutian archipelago eruptions are frequent and about 30 miles to the north of Unalaska, near the Isle of Umnak, a new island was formed in 1796. It was first observed after a storm, at a point in the sea from which a column of smoke had been seen to rise. Flames then issued from the new Islet, which illuminated the country for ten miles round. A frightful earthquake shook the new formed cone, and showers of stones were thrown as far as Umnak. The eruption continued for several months, and eight years afterwards, in 1804, when it was explored by some hunters, the soil was so hot in some places that they could not walk on it. According to Langsdorf and others, this new island, which is now several thousand feet high, and two or three miles in circumference, has been continually found to have increased in size when successively visited by different travelers. But we have no accurate means of determining how much of its growth, if any, has been due to upheaval, or how far it has been exclusively formed by the ejection of ashes and streams of lava. It seems, however, to be well attested that earthquakes of the most terrific description agitate and alter the bed of the sea and surface of the land throughout this tract. The line is continued in the southern extremity of the peninsula of Kamschatka, where there are many active volcanoes, which, in some eruptions, have scattered ashes to immense distances. The largest and most active of these is Klutschew, latitude 56 degrees, three minutes north, which rises at once from the sea to the prodigious height of 15,000 feet. Within 700 feet of the summit, Hermann saw, in 1829, a current of lava, emitting a vivid light, flow down the northwest side to the foot of the Cone. A flow of lava from the summit of Mont Blanc to its base in the valley of Chamuny would afford but an inadequate idea of the declivity down which this current descended. Large quantities of ice and snow opposed for a time a barrier to the lava, until at length the fiery torrent overcame by its heat and pressure this obstacle, and poured down the mountainside with a frightful noise which was heard for a distance of more than 50 miles. The curial chain of islands constitutes the prolongation of the Kamschatka Range, where a train of volcanic mountains, nine of which are known to have been in eruption, trends in a southerly direction. The line is then continued to the southwest in the great island of Gesso and again in Nippon, the principal of the Japanese group. It then extends by Luchu and Formosa to the Philippine islands and thence by Sangir and the northeastern extremity of Celebes to the Maluccas. Afterwards it passes westward through Sumbawa to Java. There are said to be 38 considerable volcanoes in Java, some of which are more than 10,000 feet high. They are remarkable for the quantity of sulfur and sulfurous vapors which they discharge. They rarely emit lava, but rivers of mud issue from them like the moya of the Andes of Quito. The memorable eruption of Galangun in 1822 will be described in the 25th chapter. The crater of Tashem at the eastern extremity of Java contains a lake strongly impregnated with sulfuric acid a quarter of a mile long, from which a river of acid water issues which supports no living creature nor can fish live in the sea near its confluence. There is an extinct crater near Batur called Guevo Uppas or the Valley of Poison about half a mile in circumference which is justly an object of terror to the inhabitants of the country. Every living being which penetrates into this valley falls down dead and the soil is covered with the carcasses of tigers, deer, birds and even the bones of men. All killed by the abundant emanations of carbonic acid gas by which the bottom of the valley is spilled. In another crater in this land of wonders near the volcano of Talaga Bodas we learn from Monsieur Reinhart that the sulfurous exhalations have killed tigers, birds and innumerable insects and the soft parts of these animals such as the fibers, muscles, nails, hair and skin are very well preserved while the bones are corroded and entirely destroyed. We learn from observations made in 1844 by Mr. Jukes that a recent tertiary formation composed of limestone and resembling the coral rock of a fringing reef clings to the flanks of all the volcanic islands from the east end of Timor to the west end of Java. These modern calcareous strata are often white and chalk-like, sometimes 1,000 feet and upwards above the sea, regularly stratified in thick horizontal beds, and they show that there has been a general elevation of these islands at a comparatively modern period. The same linear arrangement which is observed in Java holds good in the volcanoes of Sumatra, some of which are of great height as Berapi, which is more than 12,000 feet above the sea and is continually smoking. Hot springs are abundant at its base. The volcanic line then inclines slightly to the northwest and points to Barron Island, latitude 12 degrees 15 minutes north, in the Bay of Bengal. This volcano was in eruption in 1792 and will be described in the 26th chapter. The volcanic train then extends, according to Dr. McClelland, to the island of Narcandam, latitude 13 degrees 22 minutes north, which is a cone, 7 or 800 feet high, rising from deep water and said to present signs of lava currents descending from the crater to the base. Afterwards, the train stretches in the same direction to the volcanic island of Ramri, about latitude 19 degrees north, and the adjoining island of Cheduba, which is represented in old charts as a burning mountain. Thus we arrive at the Chittagong Coast, which, in 1762, was convulsed by a tremendous earthquake. To enumerate all the volcanic regions of the Indian and Pacific oceans would lead me far beyond the proper limits of this treatise, but it will appear in the last chapter of this volume, when coral reefs are treated of, that the islands of the Pacific consist alternately of linear groups of two classes, the one lofty and containing active volcanoes, and marine strata above the sea level, and which have been undergoing upheaval in modern times, the other very low, consisting of reefs of coral, usually with lagoons in their centers, and in which there is evidence of a gradual subsidence of the ground. The extent and direction of these parallel volcanic bands have been depicted with great care by Darwin in his map before sighted. The most remarkable theater of volcanic activity in the northern Pacific, or perhaps in the whole world, occurs in the Sandwich Islands, which have been admirably treated of, in a recent work by Mr. Dana. Volcanic region from Central Asia to the Azores Another great region of subterranean disturbance is that which has been imagined to extend through a large part of Central Asia to the Azores. That is to say, from China and Tartary, through Lake Aral and the Caspian, to the Caucasus, and the countries bordering the Black Sea, then again through part of Asia Minor to Syria, and westward to the Grecian Islands, Greece, Naples, Sicily, the southern part of Spain, Portugal, and the Azores. Respecting the eastern extremity of this line in China, we have little information, but many violent earthquakes are known to have occurred there. The volcano said to have been interruption in the 7th century in Central Tartary is situated on the northern declivity of the celestial mountains, not far distant from the large lake called Isikul, and Humboldt mentions other vents and sulfotaras in the same quarter, which are all worthy of notice, as being far more distant from the ocean, 260 geographical miles than any other known points of eruption. We find on the western shores of the Caspian, in the country round Baku, a tract called the Field of Fire, which continually emits inflammable gas, while springs of naphtha and petroleum occur in the same vicinity as also mud volcanoes. Syria and Palestine abound in volcanic appearances, and very extensive areas have been shaken at different periods with great destruction of cities and loss of lives. Continual mention is made in history of the ravages committed by earthquakes in Sidon, Tyre, Beritus, Laudicia and Antioch, and in the island of Cyprus. The country around the Dead Sea appears evidently, from the accounts of modern travelers, to be volcanic. A district near Smyrna in Asia Minor was termed by the Greeks, Katase Kaumine, or the burnt up, where there is a large arid territory without trees and with a cindery soil. This country was visited in 1841 by Mr. W. J. Hamilton, who found in the valley of the Hermos perfect cones of scoriae with lava streams like those of Auverne conforming to the existing river channels and with their surface undecomposed. Grecian Archipelago Proceeding westwards, we reach the Grecian Archipelago, where Santorin, afterwards to be described, is the grand center of volcanic action. It was von Buick's opinion that the volcanoes of Greece were arranged in a line running north-northwest and south-southeast, and that they afforded the only example in Europe of active volcanoes having a linear direction. But Monsieur Verlet, on the contrary, announces as the result of his investigations, made during the French expedition to the Moria in 1829, that there is no one determinate line of direction for the volcanic phenomena in Greece, whether we follow the points of eruptions or the earthquakes or any other signs of igneous agency. Macedonia, Thrace, and Epirus have always been subject to earthquakes, and the Ionian Isles are continually convulsed. Respecting southern Italy, Sicily, and the Lapari Isles, it is unnecessary to enlarge here as I shall have occasion again to allude to them. I may mention, however, that a band of volcanic action has been traced by Dr. Dabini across the Italian peninsula, from Ischia to Mount Vultur in Apulia, the commencement of the line being found in the hot springs of Ischia, after which it is prolonged through Vesuvius to the Lago d'Ansanto, where gases similar to those of Vesuvius are evolved. Its farther extension strikes Mount Vultur, a lofty cone composed of tuft and lava, from one side of which carbonic acid and sulfur-retted hydrogen are emitted. Traditions of deluges The traditions which have come down to us from remote ages of great inundations said to have happened in Greece and on the confines of the Grecian settlements had doubtless their origin in a series of local catastrophes caused principally by earthquakes. The frequent migrations of the earlier inhabitants and the total want of written annals long after the first settlement of each country make it impossible for us at this distance of time to fix either the true localities or probable dates of these events. The first philosophical writers of Greece were, therefore, as much at a loss as ourselves to offer a reasonable conjecture on these points or to decide how many catastrophes might sometimes have become confounded in one tale or how much this tale may have been amplified in aftertimes or obscured by mythological fiction. The floods of Ogidjis and Dukalian are commonly said to have happened before the Trojan War, that of Ogidjis more than 17 and that of Dukalian more than 15 centuries before our era. As to the Ogidjian flood it is generally described as having laid waste Attica and was referred by some writers to a great overflowing of rivers to which cause Aristotle also attributed the deluge of Dukalian which he says affected Hellas only or the central part of Thessaly. Others imagined the same event to have been due to an earthquake which drew down masses of rock and stopped up the course of the Peneos in the narrow defile between Mounts Ossa and Olympus. As to the deluge of Samothrace which is generally referred to a distinct date it appears that the shores of that small island and the adjoining mainland of Asia were inundated by the sea. Diodorus Siculus says that the inhabitants had time to take refuge in the mountains and save themselves by flight. He also relates that long after the event the fishermen of the island drew up in their nets the capitals of columns which were the remains of cities submerged by that terrible catastrophe. These statements scarcely leave any doubt that there occurred at the period alluded to a subsidence of the coast accompanied by earthquakes and inroads of the sea. It is not impossible that the story of the bursting of the Black Sea through the Thracian Bosphorus into the Grecian Archipelago which accompanied and as some say caused the Samothracian deluge may have reference to a wave or succession of waves raised in the Yukseen by the same convulsion. We know that subterranean movements and volcanic eruptions are often attended not only by incursions of the sea but also by violent rains and the complete derangement of the river drainage of the inland country and by the damming up of the outlets of lakes by landslips or obstructions in the courses of subterranean rivers such as a bound in Thessaly and the Moria. We need not therefore be surprised at the variety of causes assigned for the traditional floods of Greece by Herodotus, Aristotle, Diodorus, Strabo and others. As to the area embraced had all the Grecian deluges occurred simultaneously instead of being spread over many centuries and had they instead of being extremely local reached at once from the Yukseen to the southwestern limit of the Peloponnes and from Macedonia to Rhodes the devastation would still have been more limited than that which visited Chile in 1835 when a volcanic eruption broke out in the Andes opposite Chiloé and another at Juan Fernández distant 720 geographical miles at the same time that several lofty cones in the Cordillera 400 miles to the eastward of that island throughout vapor and ignited matter. Throughout a great part of the space thus recently shaken in South America cities were laid in ruins or the land was permanently upheaved or mountainous waves rolled inland from the Pacific periodical alternation of earthquakes in Syria and southern Italy It has been remarked by von Hoff that from the commencement of the 13th to the latter half of the 17th century there was an almost entire cessation of earthquakes in Syria and Judea and during this interval of quiescent the archipelago together with part of the adjacent coast of lesser Asia as also southern Italy and Sicily suffered greatly from earthquakes while volcanic eruptions were unusually frequent in the same regions A more extended comparison also of the history of the subterranean convulsions of these tracks seems to confirm the opinion that a violent crisis of commotion never visits both at the same time It is impossible for us to declare as yet whether this phenomenon is constant in this and other regions because we can rarely trace back a connected series of events farther than a few centuries But it is well known that where numerous vents are clustered together within a small area as in many archipelagos for instance two of them are never in violent eruption at once If the action of one becomes very great for a century or more the others assume the appearance of spent volcanoes It is therefore not improbable that separate provinces of the same great range of volcanic fires may hold a relation to one deep-seated focus analogous to that which the apertures of a small group bear to some more superficial rent or cavity Thus for example we may conjecture that at a comparatively small distance from the surface Ischia and Vesuvius mutually communicate with certain fissures and that each affords relief alternately to elastic fluids and lava they are generated So we may suppose southern Italy and Syria to be connected at a much greater depth with a lower part of the very same system of fissures In which case any obstruction occurring in one duct may have the effect of causing almost all the vapor and melted matter to be forced up the other and if they cannot get vent they may be the cause of violent earthquakes Some objections advanced against this doctrine that volcanoes act as safety valves will be considered in the sequel The northeastern portion of Africa including Egypt which lies six or seven degrees south of the volcanic line already traced has been almost always exempt from earthquakes but the northwestern portion especially Fez and Morocco which fall within the line suffer greatly from time to time The southern part of Spain also and Portugal have generally been exposed to the same scourge simultaneously with northern Africa The provinces of Malaga, Murcia and Granada and in Portugal the country round Lisbon are recorded at several periods to have been devastated by great earthquakes It will be seen from Michel's account of the great Lisbon shock in 1755 that the first movement proceeded from the bed of the ocean ten or fifteen leagues from the coast So late as February 2 1816 when Lisbon was vehemently shaken two ships felt a shock in the ocean west from Lisbon one of them at the distance of 120 and the other 262 French leagues from the coast A fact which is more interesting because a line drawn through the Grecian archipelago the volcanic region of southern Italy, Sicily, southern Spain and Portugal will if prolonged westward through the ocean strike the volcanic group of the azures which may possibly therefore have a submarine connection with the European line In regard to the volcanic system of southern Europe it may be observed that there is a central tract where the greatest earthquakes prevail in which rocks are shattered, mountains rent, the surface elevated or depressed and cities lead in ruins On each side of this line of greatest commotion there are parallel bands of country where the shocks are less violent At a still greater distance as in northern Italy for example extending to the foot of the Alps there are spaces where the shocks are much rarer and more feeble yet possibly of sufficient force to cause by continued repetition some appreciable alteration in the external form of the earth's crust Beyond these limits again all countries are liable to slight tremors at distant intervals of time when some great crisis of subterranean movement agitates an adjoining volcanic region but these may be considered as mere vibrations propagated mechanically through the external covering of the globe as the islands travel almost two indefinite distances through the air Shocks of this kind have been felt in England, Scotland, northern France and Germany particularly during the Lisbon earthquake but these countries cannot on this account be supposed to constitute parts of the southern volcanic region any more than the Shetland and Orkney islands can be considered as belonging to the Icelandic circle which is ejected from Hekla have been wafted thither by the winds besides the continuous spaces of subterranean disturbance of which we have merely sketched the outline there are other disconnected volcanic groups of which several will be mentioned hereafter lines of active and extinct volcanoes not to be confounded we must always be careful to distinguish between lines of extinct and active volcanoes even where they appear to run in the same direction for ancient and modern systems may interfere with each other already indeed we have proof that this is the case so that it is not by geographical position but by reference to the species of organic beings alone whether aquatic or terrestrial whose remains occur in beds inter stratified with lavas that we can clearly distinguish the relative age of volcanoes of which no eruptions are recorded had southern Italy been known to civilized nations for as short a period as America we should have had no record of eruptions in Ischia yet we might have assured ourselves that the lavas of that isle had flowed since the Mediterranean was inhabited by the species of testesia now living in the Neapolitan seas with this assurance it would not have been rash to include the numerous vents of that island in the modern volcanic group of Campania on similar grounds we may infer without much hesitation that the eruptions of Etna and the modern earthquakes of Calabria are a continuation of that action which at a somewhat earlier period produced the submarine lavas of the Val di Notto in Sicily but on the other hand the lavas of the Eugenian hills and the Vicentin although not wholly beyond the range of earthquakes in northern Italy must not be confounded with any existing volcanic system for when they flowed the seas were inhabited by animals almost all of them distinct from those now known to live whether in the Mediterranean or other parts of the globe end of chapter 22 part 2 recording by Linda Johnson chapter 23 part 1 of principles of geology this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org principles of geology by Charles Liel chapter 23 part 1 volcanic district of Naples history of the volcanic eruptions in the district round Naples early convulsions in the island of Ischia numerous cones thrown up there Lake Avernus the Sulphatara renewal of the eruptions of Vesuvius AD 79 Pliny's description of the phenomena his silence respecting the destruction of Herculaneum and Pompeii subsequent history of Vesuvius lava discharged in Ischia in 1302 pause in the eruptions of Vesuvius Montenuovo thrown up uniformity of the volcanic operations of Vesuvius and flagrayan fields in ancient and modern times I shall next give a sketch of the history of some of the volcanic vents dispersed throughout the great regions before described and consider the composition and arrangement of their lavas and ejected matter the only volcanic region known to the ancients was that of the Mediterranean and even of this they have transmitted to us very imperfect records relating to the eruptions of the three principal districts namely that round Naples that of Sicily and its Isles and to that of the Grecian Archipelago by far the most connected series of records throughout a long period relates to the first of these provinces and these cannot be too attentively considered as much historical information is indispensable in order to enable us to obtain a clear view of the connection and alternate mode of action of the different vents in a single volcanic group early convulsions in the island of Ischia the Neapolitan volcanoes extend from Vesuvius through the flagrayan fields to Proceda and Ischia in a somewhat linear arrangement ranging from the northeast to the southwest as will be seen in the annexed map of the volcanic district of Naples within the space above limited the volcanic forces sometimes developed in single eruptions from a considerable number of irregularly scattered points but a great part of its action has been confined to the principal and habitual vent Vesuvius or Somma before the Christian era from the remotest periods of which we have any tradition this principal vent was in a state of inactivity but terrific convulsions then took place from time to time in Ischia, Pithacusa and seem to have extended to the neighboring isle of Proceda Prochita for Strabo mentions a story of Proceda having been torn asunder from Ischia and Pliny derives its name from its having been poured forth by an eruption from Ischia the present circumference of Ischia along the water's edge is 18 miles its length from west to east about 5 and its breadth from north to south 3 miles several Greek colonies which settled there before the Christian era were compelled to abandon it in consequence of the violence of the eruptions first the Erythrians and afterwards the Chassidians are mentioned as having been driven out by earthquakes and igneous exhalations a colony was afterwards established by Hiero king of Syracuse about 380 years before the Christian era but when they had built a fortress they were compelled by an eruption to fly and never again returned Strabo tells us that Timaeus recorded a tradition that a little before his time Epomias the principal mountain in the center of the island vomited fire during great earthquakes that the land between it and the coast had ejected much fiery matter which flowed into the sea and that the sea receded for the distance of 3 stadia and then returning overflowed the island this eruption is supposed by some to have been that which formed the crater of Monte Corvo on one of the higher flanks of Epomio above Foria the lava current of which may still be traced by aid of the scoriae on its surface from the crater to the sea to one of the subsequent eruptions in the lower parts of the isle which caused the expulsion of the first Greek colony Monte Rotaro has been attributed and it bears every mark of recent origin the cone which I examined in 1828 is remarkably perfect and has a crater on its summit precisely resembling that of Monte Nuovo near Naples but the hill is larger and resembles some of the more considerable cones of single eruption near Clermont in Auvern and like some of them it has given vent to a lava stream at its base instead of its summit a small ravine swept out by a torrent exposes the structure of the cone which is composed of innumerable inclined and slightly undulating layers of pumice, scoriae, quite lapili and enormous angular blocks of trachite these last have evidently been thrown out by violent explosions like those which in 1822 launched from Vesuvius a mass of ogitic lava of many tons weight to the distance of three miles which fell in the garden of Prince Ottagiano the cone of Rotaro is covered with the arbitus and other beautiful evergreens such is the strength of the virgin soil that the shrubs have become almost arborescent and the growth of some of the smaller wild plants has been so vigorous that botanists have scarcely been able to recognize the species the eruption which dislodged the Syracusian colony is supposed to have given rise to that mighty current which forms the promontory of Zaro and Caruso the surface of these lavas is still very arid and bristling and is covered with black scoriae so that it is not without great labor that human industry has redeemed some small spots and converted them into vineyards upon the produce of these vineyards the population of the island is almost entirely supported it amounted when I was there in 1828 to about 25,000 and was on the increase from the date of the great eruption last alluded to down to our own time Ischia has enjoyed tranquility with the exception of one emission of lava hereafter to be described which, although it occasioned much local damage does not appear to have devastated the whole country in the manner of more ancient explosions there are upon the whole, on different parts of Epomio or scattered through the lower tracts of Ischia twelve considerable volcanic cones which have been thrown up since the island was raised above the surface of the deep and many streams of lava may have flowed like that of Arso in 1302 without cones having been produced so that this island may, for ages before the period of the remotest traditions have served as a safety valve to the whole Terra della Voro while the fires of Vesuvius were dormant Lake Avernus it seems also clear that Avernus a circular lake near Puzzuoli about half a mile in diameter which is now a salubrious and cheerful spot once exhaled mephitic vapors such as are often emitted by craters after eruptions there is no reason for discrediting the account of Lucretius that birds could not fly over it without being stifled although they may now frequent it uninjured there must have been a time when this crater was in action and for many centuries afterwards it may have deserved the appellation of atrigiounaditis emitting perhaps gases as destructive of animal life as those suffocating vapors given out by Lake Killotoa in Chito in 1797 by which whole herds of cattle on its shores were killed or as those deleterious emanations which annihilated all the cattle in the island of Lancerote one of the canaries in 1730 Bore St. Vincent mentions that in the same isle birds fell lifeless to the ground and Sir William Hamilton informs us that he picked up dead birds on Vesuvius during interruption Solphatara the Solphatara near Puzzuoli which may be considered as a nearly extinguished crater appears by the accounts of Strabo and others to have been before the Christian era in very much the same state as at present giving vent continually to aqueous vapor together with sulfurous and muriatic acid gases like those evolved by Vesuvius ancient history of Vesuvius such then were the points where the subterranean fires obtained vent from the earliest period to which tradition reaches back down to the first century of the Christian era but we then arrive at a crisis in the volcanic action of this district one of the most interesting events witnessed by man during the brief period throughout which he has observed the physical changes on the earth's surface from the first colonization of southern Italy by the Greeks Vesuvius afforded no other indications of its volcanic character than such as the naturalist might infer from the analogy of its structure to other volcanoes these were recognized by Strabo but Pliny did not include the mountain in his list of active vents the ancient cone was of a very regular form terminating not as at present in two peaks but with a summit which presented when seen from a distance the even outline of an abruptly truncated cone on the summit as we learn from Plutarch there was a crater with steep cliffs and having its interior overgrown with wild vines and with a sterile plain at the bottom on the exterior the flanks of the mountain were clothed with fertile fields richly cultivated and at its base were the populous cities of Herculaneum and Pompeii but the scene of repose was at length doomed to cease and the volcanic fire was recalled to the main channel which at some former unknown period had given passage to repeated streams of melted lava sand and scoriae renewal of its eruptions the first symptom of the revival of the energies of this volcano was the occurrence of an earthquake in the year 63 after Christ which did considerable injury to the cities in its vicinity from that time to the year 79 slight shocks were frequent and in the month of August of that year they became more numerous and violent in an eruption the elder Pliny who commanded the Roman fleet was then stationed at Misenum and in his anxiety to obtain a near view of the phenomena he lost his life being suffocated by sulfurous vapors his nephew the younger Pliny remained at Misenum and has given us in his letters a lively description of the awful scene a dense column of vapor was first seen rising vertically from Vesuvius and then spreading itself out laterally so that its upper portion resembled the head and its lower the trunk of the pine which characterizes the Italian landscape this black cloud was pierced occasionally by flashes of fire as vivid as lightning succeeded by darkness more profound than night ashes fell even upon the ships at Misenum and caused a shoal in one part of the sea the ground rocked and the sea receded from the shores so that many marine animals were seen on the dry sand the appearances above described agree perfectly with those witnessed in more recent eruptions especially those of Montenuovo in 1538 and of Vesuvius in 1822 the younger Pliny although giving a circumstantial detail of so many physical facts and describing the eruption and earthquake and the shower of ashes which fell at Stébier makes no allusion to the sudden overwhelming of two large and populous cities Herculaneum and Pompeii in explanation of this omission he suggested that his chief object was simply to give Tacitus a full account of the particulars of his uncle's death it is worthy however of remark that had the buried cities never been discovered the accounts transmitted to us of their tragical end might well have been discredited by the majority so vague and general are the narratives or so long subsequent to the event Tacitus the friend and contemporary of Pliny when adverting in general terms to the convulsions says merely that cities were consumed or buried Suetonius although he alludes to the eruption incidentally is silent as to the cities they are mentioned by Marshall in an epigram as immersed in cinders but the first historian who alludes to them by name is Dion Cassius who flourished about a century and a half after Pliny he appears to have derived his information from the traditions of the inhabitants and to have recorded without discrimination all the facts and fables which he could collect he tells us that during the eruption a multitude of men of superhuman stature resembling giants appeared sometimes on the mountain and sometimes in the environs that stones and smoke were thrown out the sun was hidden and then the giants seemed to rise again while the sounds of trumpets were heard et cetera et cetera and finally he relates two entire cities Herculaneum and Pompeii were buried under showers of ashes while all the people were sitting in the theater that many of these circumstances were invented would have been obvious even without the aid of Pliny's letters and the examination of Herculaneum and Pompeii enables us to prove that none of the people were destroyed in the theaters and indeed that there were very few of the inhabitants who did not escape from both cities yet some lives were lost and there was ample foundation for the tale in its most essential particulars it did not appear that in the year 79 any lava flowed from Vesuvius the ejected substances perhaps consisted entirely of lapili, sand and fragments of older lava as when Montenuovo was thrown up in 1538 the first era at which we have authentic accounts of the flowing of a stream of lava is the year 1036 which is the seventh eruption from the revival of the fires of the volcano a few years afterwards in 1049 another eruption is mentioned and another in 1138 or 1139 after which a great pause ensued of 168 years during this long interval of repose two minor vents opened at distant points first it is on tradition that an eruption took place from the Sulfatara in the year 1198 during the reign of Frederick II emperor of Germany and although no circumstantial detail of the event has reached us from those dark ages we may receive the fact without hesitation nothing more however can be attributed to this eruption as Mr. Scrope observes then the discharge of a light and scora form trachitic lava of recent aspect resting upon the strata of loose tough which covers the principal mass of trachite volcanic eruption in Ischia 1302 the other recurrence is well authenticated the eruption in the year 1302 of a lava stream from a new vent on the southeast end of the island of Ischia during part of 1301 earthquakes had succeeded one another with fearful rapidity and they terminated at last with the discharge of a lava stream from a point named the Campo del Arso not far from the town of Ischia this lava ran quite down to the sea a distance of about two miles in color it varies from iron gray to reddish black and is remarkable for the glassy felspar which it contains its surface is almost as sterile after a period of five centuries as if it had cooled down yesterday a few scantlings of wild time and two or three other dwarfish plants alone appear in the interstices of the Scoriae while the Visuvian lava of 1767 is already covered with a luxuriant vegetation Pontanus whose country house was burnt and overwhelmed describes the dreadful scene as having lasted two months many houses were swallowed up and a partial emigration of the inhabitants followed this eruption produced no cone but only a slight depression hardly deserving the name of a crater where heaps of black and red Scoriae lie scattered around until this eruption Ischia is generally believed to have enjoyed an interval of rest for about 17 centuries but Julius Obsequenz who flourished AD 214 refers to some volcanic convulsions in the year 662 after the building of Rome 91 BC as Pliny who lived a century before Obsequenz does not enumerate this among other volcanic eruptions the statement of the latter author is supposed to have been erroneous that it would be more consistent for reasons before stated to disregard the silence of Pliny and to conclude that some kind of subterranean commotion probably of no great violence happened at the period alluded to History of Visuvius to return to Visuvius the next eruption occurred in 1306 between which era and 1631 there was only one other in 1500 and that a slight one it has been remarked that throughout this period Etna was in a state of such unusual activity as to lend countenance to the idea that the great Sicilian volcano may sometimes serve as a channel of discharge to elastic fluids and lava that would otherwise rise to the vents in Campania End of Chapter 23 Part 1 Recording by Linda Johnson Chapter 23 Part 2 of Principles of Geology This is a LibriVox recording All LibriVox recordings are in the public domain For more information or to volunteer please visit LibriVox.org Principles of Geology by Charles Lyell Chapter 23 Part 2 Formation of Montenuovo 1538 The great pause was also marked by a memorable event in the Phlegrean Fields the sudden formation of a new mountain in 1538 of which we have received authentic accounts from contemporary writers The height of this mountain, called ever since Montenuovo, has been determined by the Italian mineralogist Pimi to be 440 English feet above the level of the bay its base is about 8000 feet or more than a mile and a half in circumference According to Pimi the depth of the crater is 421 English feet of the hill, so that its bottom is only 19 feet above the level of the sea the cone is declared by the best authorities to stand partly on the site of the Lucrine Lake which was nothing more than the crater of a pre-existent volcano and was almost entirely filled during the explosion of 1538 Nothing now remains but a shallow pool separated from the sea by an elevated beach raised artificially Sir William Hamilton has given us two original letters describing this eruption The first by Falcone, dated 1538 contains the following passages Quote It is now two years since there have been frequent earthquakes at Puzzuoli, Naples, and the neighboring parts On the day and in the night before the eruption of Montenuovo above 20 shocks, great and small, were felt The eruption began on the 29th of September 1538 It was on a Sunday, about one o'clock in the night, when flames of fire were seen between the hot baths and Tripergola In a short time the fire increased to such a degree that it burst open the earth in this place and threw up so great a quantity of ashes and pumice stones mixed with water as covered the whole country The next morning, after the formation of Montenuovo, the poor inhabitants of Puzzuoli quitted their habitations in terror, covered with the muddy and black shower which continued the whole day in that country, flying from death but with death painted in their countenances Some with their children in their arms with sex full of their goods Others leading an ass loaded with their frightened family towards Naples Others carrying quantities of birds of various sorts that had fallen dead at the beginning of the eruption Others again with fish which they had found and which were to be met with in plenty on the shore the sea having left them dry for a considerable time they accompanied Signor Moramaldo to behold the wonderful effects of the eruption The sea had retired on the side of Baye abandoning a considerable tract and the shore appeared almost entirely dry from the quantity of ashes and broken pumice stones thrown up by the eruption I saw two springs in the newly discovered ruins one before the house that was the queens of hot and salt water, etc. So far Falcone The other account is by Pietro Giacomo di Toledo which begins thus Quote It is now two years since this province of Campania has been afflicted with earthquakes the country about Puzzuoli much more so than any other parts but the 27th and the 28th of the month of September last the earthquakes did not cease day or night in the town of Puzzuoli that plain which lies between Lake Avernus the Monte Barbaro and the sea was raised a little and many cracks were made in it from some of which issued water at the same time the sea immediately joining the plain dried up about 200 paces so that the fish were left on the sand prey to the inhabitants of Puzzuoli at last on the 29th of the same month about two o'clock in the night the earth opened near the lake and discovered a horrid mouth from which were vomited furiously smoke, fire, stones and mud composed of ashes making at the time of its opening a noise like the loudest thunder the stones which followed were by the flames converted to pumice and some of these were larger than an ox the stones went about as high as a crossbow can carry and then fell down sometimes on the edge and sometimes into the mouth itself the mud was of the color of ashes and at first very liquid then by degrees less so and in such quantities that in less than 12 hours with the help of the above mentioned stones a mountain was raised of 1,000 paces in height not only Puzzuoli and the neighboring country was full of this mud but the city of Naples also so that many of its palaces were defaced by it now this eruption lasted two nights and two days without intermission though it is true not always with the same force the third day the eruption ceased and I went up with many people to the top of the new hill and saw down into its mouth which was a round cavity about a quarter of a mile in circumference in the middle of which the stones which had fallen were boiling up just as a cauldron of water boils on the fire the fourth day it began to throw up again and the seventh much more but still with less violence than the first night at this time many persons who were on the hill were knocked down by the stones and killed or smothered with the smoke in the day the smoke still continues and you often see fire in the midst of it in the night time end quote it will be seen that both these accounts written immediately after the birth of Montenuovo agree in stating that the sea retired and one mentions that its bottom was upraised but they attribute the origin of the new hill exclusively to the jets of mud the towers of Scoriae and large fragments of rock cast out from a central orifice for several days and nights Baron von Buke however in his excellent work on the Canary Islands and volcanic phenomena in general has declared his opinion that the cone and crater of Montenuovo were formed not in the manner above described but by the upheaval of solid beds of white tough which were previously horizontal but which were pushed up in 1538 so as to dip away in all directions from the center with the same inclination as the sloping surface of the cone itself it is an error he says to imagine that this hill was formed by eruption or by the ejection of Pommes Scoriae and other incoherent matter for the solid beds of upraised tough are visible all round the crater and it is merely the superficial covering of the cone which is made up of ejected Scoriae in confirmation of this view Monsieur de Rénoy has cited a passage from the works of Porteo a celebrated physician of that period to prove that in 1538 the ground where Montenuovo stands was pushed up in the form of a great bubble or blister which on bursting gave origin to the present deep crater Porteo says that after two days and nights of violent earthquakes the sea retired for nearly 200 yards so that the inhabitants could collect great numbers of fish on this part of the shore and see some springs of fresh water which rose up there at length on the third day of the calends of October September 29 they saw a large tract of ground intervening between the foot of Monte Barbaro near the Lake Avernus rise and suddenly assume the form of an incipient hill and at two o'clock at night this heap of earth opening as it were its mouth vomited with a loud noise flames, pumice stones and ashes end quote so late as the year 1846 a fourth manuscript written immediately after the eruption was discovered and published in Germany it was written in 1538 by Francesco Del Nero who mentions the drying up of the bed of the sea near Puzzuoli which enabled the inhabitants of the town to carry off loads of fish about eight o'clock in the morning of the 29th September the earth sunk down about 14 feet in that place where the volcanic orifice now appears and there issued forth a small stream of water at first cold at noon on the same day the earth began to swell up in the same spot where it had sunk down 14 feet so as to form a hill about this time fire issued forth and gave rise to the great gulf quote with such a force noise and shining light that I who was standing in my garden was seized with terror 40 minutes afterwards although unwell I got upon a neighbouring height from which I saw all that took place and by my trove it was a splendid fire that threw up for a long time much earth and many stones which fell back again all round the gulf in a semicircle of from one to three bow shots in diameter and filling up part of the sea formed a hill nearly of the height Monte Morello masses of earth and stones as large as an ox were shot up from the fiery gulf into the air to a height which I estimate at a mile and a half when they descended some were dry others in a soft muddy state end quote he concludes by alluding again to the sinking of the ground and the elevation of it which followed and says that to him the stones and ashes could have been poured forth from the gulf he also refers to the account which Porzio was to draw up for the viceroy on comparing these four accounts recorded by eyewitnesses there appears to be no real discrepancy between them it seems clear that the ground first sunk down 14 feet on the site of the future volcano and after having subsided it was again propelled upwards to the lava mingled with steam and gases which were about to burst forth jets of red hot lava fragments of fractured rock and occasionally mud composed of a mixture of pumice tough and seawater were hurled into the air some of the blocks of stone were very large leading us to infer that the ground which sank and rose again was much shattered the hill was not formed at once but by an intermittent action extending over a week or more it seems that the chasm opened between Tripergola and the baths in its suburbs and that the ejected materials fell and buried that small town a considerable part however of the hill was formed in less than 24 hours and in the same manner as on a smaller scale the mud cones of the air were in the middle there is no difficulty in conceiving that the pumice's mud if so thrown out may have set into a kind of stone on drying just as some cements composed of volcanic ashes are known to consolidate with facility I am informed that Baron von Buick discovered some marine shells of existing species such as a curfossil in the tough of the neighbourhood these may have been ejected in the mud mixed with seawater which was cast out of the boiling gulf or a senior Arcangelo Scacci has suggested they may have been derived from the older tough which contains marine shells of recent species the same observer remarks that Portio's account upon the hole corroborates the doctrine of the cone having been formed by eruption of the passage quote but what was truly astonishing a hill of pumice stones and ashes was heaped up round the gulf to the height of a mile in a single night end quote senior Scacci also adds that the ancient temple of Apollo now at the foot of Montenuovo and the walls of which still retain their perfect perpendicularity could not possibly have maintained that position had the cone of Montenuovo really been the result of upheaval Tripergola was much frequented as a watering place and contained a hospital for those who resorted there for the benefit of the thermal springs and it appears that there were no fewer than three inns in the principal street had Portio stated that any of these buildings or the ruins of them were seen by himself on the plain a short time before the first eruption so as to stand on the summit or slope of a newly raised hillock we might have been compelled by so circumstantial a narrative to adapt Monsieur de Fraenoise's interpretation but in the absence of such evidence we must appeal to the crater itself where we behold a section of the whole mountain without being able to detect any original nucleus distinct from the rest on the contrary the whole mass is similar throughout in composition and the cone very symmetrical in form nor are there any clefts such as might be looked for as the effect of the sudden up throw of stony masses MC provost has well remarked that if beds of solid and non-elastic materials had yielded to a violent pressure directed from below upward we should find not simply a deep empty cavity but an irregular opening where many rents converged and these rents would be now seen breaking through the walls of the crater widening as they approach the center not a single fissure of this kind is observable in the interior of Montenuovo where the walls of the crater are continuous and entire nor are there any dykes implying that rents had existed afterwards filled with lava or other matter it has moreover been often urged by von Buick de Beaumont and others who ascribe the conical form of volcanoes chiefly to upheaval from below that in such mountains there are a great number of deep rents and ravines which diverge on all sides like the spokes of a wheel from near the central axis or base of the cone as in the case of Palma Cantal and Tenerife yet the entire absence of such divergent fissures or ravines in such cases as Montenuovo Somma or Etna is passed by unnoticed and appears to have raised in their minds no objection to their favorite theory it is indeed admitted by Monsieur de Freynoy there are some facts which it is very difficult to reconcile with his own view of Porteo's record thus for example there are certain Roman monuments at the base of Montenuovo and on the borders of Lake Avernus such as the temples of Apollo before mentioned and Pluto which do not seem to have suffered in the least degree by the supposed upheaval of their vertical position and the vaults are in the same state as other monuments on the shores of the Bay of Baye the long gallery which led to the Sibyl's cave on the other side of Lake Avernus has in like manner escaped injury the roof of the gallery remaining perfectly horizontal the only change being that the soil of the chamber in which the Sibyl gave out her oracles creates a slight alteration in the level of Lake Avernus end quote on the supposition then that pre-existing beds of pumiceous tuft were upraised in 1538 so as to form Montenuovo it is acknowledged that the perfectly undisturbed state of the contiguous soil on which these ancient monuments stand is very different from what might have been expected Mr. Darwin in his Volcanic Islands has described several crater form hills in the Galapagos Archipelago as composed of tuft which has evidently flowed like mud and yet on consolidating has preserved an inclination of 20 and even 30 degrees the tuft does not fold in continuous sheets round the hills as would have happened if they had been formed in a heap of horizontal layers the author describes the composition of the tuft as very similar to that of Montenuovo and the high angles at which the beds slope both those which have flowed and those which have fallen in the form of ashes entirely removes the difficulty supposed by Monsieur de Freynoy to exist in regard to the slope of Montenuovo where it exceeds an angle from 30 degrees to 20 degrees Mr. Dana also in his account of the Sandwich Islands shows that in the cinder cones of that region the strata have an original inclination of between 35 degrees and 40 degrees while in the tuft cones formed near the sea the beds slope at about an angle of 30 degrees the same naturalist also observed in the Samoan or navigator islands in Polynesia that fragments of fresh coral had been thrown up together with volcanic matter to the height of 200 feet above the level of the sea in cones of tufa I shall again revert to the doctrine of the origin of volcanic cones by upheaval when speaking of Vesuvius Etna and Santorin and shall now merely add that in 1538 the whole coast from Montenuovo to beyond Puzzoli was upraised to the height of many feet above the bed of the Mediterranean and has since retained the greater part of the elevation then acquired the proofs of these remarkable changes of level will be considered at length when the phenomena of the temple of Serapis are described immediately adjoining Montenuovo is the larger volcanic cone of Monte Barbaro the Gorus Inanus of Juvenal an appellation given to it probably from its deep circular crater which is about a mile in diameter large as is this cone it was probably produced by a single eruption and it does not perhaps exceed in magnitude some of the largest of those formed in Ischia within the historical era it is composed chiefly of indurated tufa like Montenuovo stratified conformably to its conical surface this hill was once very celebrated for its wines and is still covered with vineyards but when the vine is not in leaf it has a sterile appearance and late in the year when seen from the beautiful so strongly in Virger with Montenuovo which is always clothed with Arbitis, Myrtle and other wild evergreens that a stranger might well imagine the cone of older date to be that thrown up in the 16th century there is nothing indeed so calculated to instruct the geologist as the striking manner in which the recent volcanic hills of Ischia blend with the surrounding landscape nothing seems wanting or redundant every part of the picture is in such perfect harmony with the rest that the whole has the appearance of having been called into existence by a single effort of creative power yet what other result could we have anticipated if nature has ever been governed by the same laws each new mountain thrown up each new tract of land that is pressed by earthquakes should be in perfect accordance with those previously formed if the entire configuration of the surface has been due to a long series of similar disturbances were it true that the greater part of the dry land originated simultaneously in its present state at some era of paroxysmal convulsion and that additions were afterwards made slowly and successively during a period of time indeed there might be reason to expect a strong line of demarcation between the signs of the ancient and modern changes but the very continuity of the plan and the perfect identity of the causes are to many a source of deception since by producing a unity of effect they lead them to exaggerate the energy of the agents which operated in the earlier ages in the absence they are as unable to separate the dates of the origin of different portions of our continents as the stranger is to determine by their physical features alone the distinct ages of Monte Nuovo, Monte Barbara, Astroni and the Sol Fattara the vast scale and violence of the volcanic operations in Campania in the olden time has been a theme of declamation and contrasted with the comparative state of quiescence of this delightful region in the modern era instead of inferring from analogy that the ancient Vesuvius was always at rest when the craters of the flagrayan fields were burning that each cone rose in succession and that many years and often centuries of repose intervened between different eruptions geologists seem to have generally conjectured that the whole group sprung up from the ground at once like the soldiers of Cadmus when he sewed the dragon's teeth as well might they endeavor to persuade us that on these flagrayan fields as the poets feigned the giants warred with a jove ere yet the puny race of mortals were in being modern eruptions of Vesuvius for nearly a century after the birth of Monte Nuovo Vesuvius continued in a state of tranquility there had been no violent eruption for 492 years and it appears that the crater was then exactly in the condition of the present extinct volcano of Astroni near Naples Braccini who visited Vesuvius not long before the eruption of 1631 gives the following interesting description of the interior quote the crater was five miles in circumference and about a thousand paces deep its sides were covered with brushwood and at the bottom there was a plane on which cattle grazed in the woody parts wild boars frequently harbored in one part of the plane covered with ashes were three small pools one filled with hot and bitter water another salter than the sea and a third hot but tasteless end quote but at length these forests and grassy plains were consumed being suddenly blown into the air and their ashes scattered to the winds in December 1631 seven streams of lava poured at once from the crater and overflowed several villages on the flanks and at the foot of the mountain Resina partly built over the ancient site of Herculaneum was consumed by the fiery torrent great floods of mud were as destructive as the lava itself no uncommon occurrence during these catastrophes for such is the violence of rains produced by the evolutions of aqueous vapor that torrents of water descend the cone and becoming charged with impalpable volcanic dust and rolling along loose ashes acquire sufficient consistency to deserve their ordinary appellation of aqueous lavas a brief period of repose ensued which lasted only until the year 1666 from which time to the present there has been a constant series of eruptions with rarely an interval of rest exceeding ten years during these three centuries no irregular volcanic agency has convulsed other points in this district Breeslach remarked that such irregular convulsions had occurred in the Bay of Naples in every second century as for example the eruption of the Sol Fattara in the 12th of the lava of Arso in Ischia in the 14th and of Montenuovo in the 16th but the 18th has formed an exception to this rule and this seems accounted for by the unprecedented number of eruptions of Vesuvius during that period whereas when the new vents opened there had always been as we have seen a long intermittence of activity in the principal volcano end of chapter 23 part 2 recording by Linda Johnson chapter 24 part 1 of principles of geology this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org principles of geology by Charles Lyell chapter 24 part 1 volcanic district of Naples continued dimensions and structure fluidity and motion of lava dikes alluviums called aquiaslavas origin and composition of the matter enveloping herculaneum and Pompeii condition and contents of the buried cities small number of skeletons state of preservation of animal and vegetable substances rolls of papyrus torre del greco concluding remarks on the campanile and volcanoes structure of the cone of Vesuvius between the end of the 18th century and the year 1822 the great crater of Vesuvius had been gradually filled by lava boiling up from below and by scoriae falling from the explosions of minor mouths which were formed on both sides bottom and sides in place of a regular cavity therefore there was a rough and rocky plain covered with blocks of lava and scoriae and cut by numerous fissures from which clouds of vapor were evolved but this state of things was totally changed by the eruption of October 1822 when violent explosions during the space of more than half the mass so as to leave an immense gulf or chasm of an irregular but somewhat elliptical shape about three miles in circumference when measured along the very sinuous and irregular line of its extreme margin but somewhat less than three quarters of a mile in its longest diameter which was directed from northeast to southwest the depth of this tremendous abyss has been variously estimated but from the hour of its formation it increased daily by the dilapidation of its sides it measured at first according to the account of some authors 2,000 feet in depth from the extreme part of the existing summit but Mr. Scrope when he saw it soon after the eruption estimated its depth at less than half that amount more than 800 feet of the cone was carried away by the explosions so that the mountain from about 4,200 to 3,400 feet as we ascend the sloping sides the volcano appears a mass of loose materials a mere heap of rubbish thrown together without the slightest order but on arriving at the brim of the crater and obtaining a view of the interior we are agreeably surprised to discover that the conformation of the hole displays in every part the most perfect symmetry and arrangement the materials are disposed in regular strata slightly undulating appearing when viewed in front to be disposed in horizontal planes but as we make the circuit of the edge of the crater and observe the cliffs by which it is encircled projecting or receding in salient or retiring angles we behold transverse sections of the currents of lava of sand and scoriae and recognize their true dip we then discover that they incline outwards from the axis of the cone at angles varying from 30 degrees to 40 degrees the whole cone in fact is composed of a number of concentric coatings of alternating lavas, sand and scoriae every shower of ashes which has fallen from above and every stream of lava on the lips of the crater have conformed to the outward surface of the hill so that one conical envelope may be said to have been successfully folded round another until the aggregation of the whole mountain was completed the marked separation into distinct beds results from the different colors and degrees of coarseness in the sands, scoriae and lava and the alternation of these with each other each difficulty on the first view is to conceive how so much regularity can be produced not withstanding the unequal distribution of sand and scoriae driven by prevailing winds in particular eruptions and the small breadth of each sheet of lava as it first flows out from the crater but on a closer examination we find that the appearance of extreme uniformity is delusive for when a number of beds are at different points the eye does not without difficulty recognize the termination of any one stratum but usually supposes it continuous with some other which at a short distance may lie precisely in the same plane the slight undulations moreover produced by inequalities on the sides of the hill on which the successive layers were molded assist the deception as countless beds of sand these may sometimes mantle continuously round the whole cone and even lava streams may be of considerable breadth when first today overflow and since in some eruptions a considerable part of the upper portion of the cone breaks down at once may form a sheet extending as far as the space which the eye usually takes in in a single section the high inclination of the beds and the firm union of the particles even where there is evidently no cement is another striking feature in the volcanic tufts and bretchas which seems at first not very easy of explanation but the last great eruption afforded ample illustration of the manner in which these strata are formed fragments of lava scoriae, pumice and sand when they fall at slight distances down from a state of fusion and are afterwards acted upon by the heat from within and by fumaroles or small crevices in the cone through which hot vapors are disengaged thus heated the ejected fragments cohere together strongly and the whole mass acquires such consistency in a few days that fragments cannot be detached without a smart blow of the hammer sand and scoriae ejected to a greater distance remain incoherent Sir William Hamilton in his description of the eruption of 1779 says that jets of liquid lava mixed with stones and scoriae were thrown up to the height of at least 10,000 feet having the appearance of a column of fire some of these were directed by the winds falling almost perpendicularly still red hot and liquid on Vesuvius covered its whole cone part of the mountain of Soma and the valley between them the falling matter being nearly as vividly inflamed as that which was continually issuing fresh from the crater formed with it one complete body of fire which could not be less than 2 miles and a half in breadth and of the extraordinary height above mentioned of at least 6 miles around it Dr. Clark also in his account of the eruption of 1793 says that millions of red hot stones were shot into the air full half the height of the cone itself and then bending fell all round in a fine arch on another occasion he says that as they fell they covered nearly half the cone with fire the same author had a different appearance of the lava at its source and at some distance from it when it had descended into the plains below at the point where it issued in 1793 from an arched chasm in the side of the mountain the vivid torrent rushed with the velocity of a flood it was in perfect fusion unattended with any scoriae on its surface or any gross materials not in a state of complete solution the translucency of honey quote in regular channels cut finer than art can imitate and glowing with all the splendor of the sun end quote quote Sir William Hamilton he continues had conceived that no stones thrown upon a current of lava would make any impression I was soon convinced of the contrary light bodies indeed of 5, 10 and 15 pounds but bodies of 60, 70 and 80 pounds were seen to form a kind of bed on the surface of the lava and float away with it a stone of 300 weight that had been thrown out by the crater lay near the source of the current of lava I raised it upon one end and then let it fall in upon the liquid lava when it gradually sunk beneath the surface and disappeared if I wished to describe the manner in which it acted upon the lava I should say that it was like a loaf of bread thrown into a bowl of very thick honey which gradually involves itself in the heavy liquid and then slowly sinks to the bottom the lava at a small distance from its source acquires a darker tint upon its surface is less easily acted upon and as the stream widens the surface having lost its state of perfect solution grows harder and harder and cracks into innumerable fragments of very porous matter to which they give the name of Scorier and the appearance of which has led many to suppose that it proceeded thus from the mountain there is however no truth in this all lava at its first exit from its native volcano flows out in a liquid state and all equally in fusion the appearance of the Scorier is to be attributed only to the action of the external air and not to any difference in the materials which compose it since any lava whatever separated from its channel and exposed to the action of the external air immediately cracks becomes porous and alters its form as we proceeded downwards this became more and more evident and the same lava at its original source flowed in perfect solution undivided and free from encumbrances of any kind a little farther down had its surface loaded with Scorier in such a manner that upon its arrival at the bottom of the mountain the whole current resembled nothing so much as a heap of unconnected cinders from an iron foundry end quote in another place he says that quote the rivers of lava in the plane resembled a vast heap of cinders or the Scorier of an iron foundry rolling slowly along and falling with a rattling noise over one another end quote Von Buick who was in company with Messieurs de Humboldt and Gaye Lussac describes the lava of 1805 the most fluid on record as shooting suddenly before their eyes in a single instant Professor J. D. Forbes remarks that the length of the slope of the cone proper being about 1300 feet this motion must correspond to a velocity of many hundred feet in a few seconds without interpreting Von Buick's expression literally the same lava when it reached the level road at Torre del Greco moved at the rate of only 18 inches per minute or 3 tenths of an inch per second although common lava observes Professor Forbes is nearly as liquid as melted iron when it issues from the orifice of the crater its fluidity rapidly diminishes and as it becomes more and more burdened by the consolidated slag through which it has to force its way its velocity of motion diminishes in an almost inconceivable degree and at length when it ceases to present the slightest external trace of fluidity its movement can only be ascertained by careful and repeated observations just as in the case of a glacier end quote it appears that the intensity of the light and heat of the lava varies considerably at different periods of the same eruption as in that of Vesuvius in 1819 and 1820 when Sir H. Davy remarked to different degrees of vividness in the white heat at the point where the lava originated when the expressions flame and smoke are used in describing volcanic appearances they must generally be understood in a figurative sense we are informed indeed by Monsieur Abish that he distinctly saw in the eruption of Vesuvius in 1834 the flame of burning hydrogen but what is usually mistaken for flame consists of vapor or scoriae and impalpable dust illuminated by that vivid light which is emitted from the crater below where the lava is said to glow with the splendor of the sun the clouds of apparent smoke are formed either of aqueous and other vapor or a finely comminuted scoriae dikes in the recent cone how formed the inclined strata before mentioned which dip outwards in all directions Vesuvius are intersected by veins or dikes of compact lava for the most part in a vertical position in 1828 these were seen to be about 7 in number some of them not less than 4 or 500 feet in height and thinning out before they reach to the uppermost part of the cone being harder than the beds through which they pass they have decomposed less rapidly and therefore stand out in relief Vesuvius in November 1828 I was prevented from descending into the crater by the constant ejections then thrown out so that I got sight of 3 only of the dikes but Senor Monticelli had previously had drawings made of the hole which he showed me the dikes which I saw were on that side of the cone which is encircled by soma the eruption before mentioned of 1828 in March and in the November following the ejected matter had filled up nearly one third of the deep abyss formed at the close of the eruption of 1822 in November I found a single black cone at the bottom of the crater continually throwing out scoriae while on the exterior of the cone I observed the lava of 1822 which had flowed out 6 years before not yet cool and still evolving much heat and vapor from crevices Hoffman in 1832 saw on the north side of Vesuvius near the peak called Palo a great many parallel bands of lava some from 6 to 8 feet thick alternating with scoriae and conglomerate these beds he says were cut through by many dikes some of them 5 feet broad they resemble those of soma the stone being composed of grains of lusite and augite there can be no doubt that the dikes above mentioned have been produced by the filling up of open fissures with liquid lava but of the date of their formation we know nothing farther than that they are all subsequent to the year 79 and relatively speaking that they are more modern than the lava's in scoriae which they intersect a considerable number of the upper strata are not traversed by them that the earthquakes which almost invariably precede eruptions occasion rents in the mass is well known and in 1822 3 months before the lava flowed out open fissures evolving hot vapors were numerous it is clear that such rents must be ejected with melted matter which is the origin of the dikes is easily explained as also the great solidity and crystalline nature of the rock composing them which has been formed by lava cooling slowly under great pressure it has been suggested that the frequent rending of the volcanic cones during eruptions may be connected with the gradual and successive upheaval of the whole mass in such a manner as to increase the number of beds composing the cone and in accordance with the hypothesis before proposed for the origin of Montenuovo van Buuk supposes that the present cone of Vesuvius was formed in the year 79 not by eruption but by upheaval it was not produced by the repeated superposition of scoriae and lava cast out or flowing from a central source but by the uplifting of Montenuovo the entire cone rose at once such as we now see it from the interior and middle of Soma and has since received no accession of height but on the contrary has ever since been diminishing in elevation although I consider this hypothesis of van Buuk to be quite untenable I may mention some facts which may at first sight seem to favor it Abish in his account of the Vesuvian eruptions of 1833 and 1834 a work illustrated by excellent engravings of the volcanic phenomena which he witnessed it appears that in the year 1834 the great crater of Vesuvius had been filled up nearly to the top with lava which had consolidated and formed a level an unbroken plane except that a small cone in the area rose in the middle of it like an island in a lake at length this plane of lava was broken by a fissure which passed from northeast to southwest and along this line a great number of minute cones emitting vapor were formed the first act of formation of these minor cones is said to have consisted of a partial upheaval and tension of elastic fluids which rising from below escaped from the center of each new montycule there would be considerable analogy between this mode of origin and that ascribed by van Buuk to Vesuvius and Soma if the dimensions of the upraised masses were not on so different a scale and if it was safe to reason from the inflation of ladders of half fused lava from 15 to 25 feet in height mountains attaining an altitude of several thousand feet and having their component strata strengthened by intersecting dykes of solid lava at the same time that when in August 1834 a great subsidence took place in the platform of lava within the great crater so that the structure of the central cone was laid open it was seen to have been scoriae which had been thrown out during successive eruptions previous to the year 79 Vesuvius appears from the description of its figure given by Strabo to have been a truncated cone having a level and even outline a scene from a distance that it had a crater on its summit we may infer from a passage in Plutarch on which Dr. Dobbini was a first-class treetis on volcanoes the walls of the crater were evidently entire except on one side where there was a single narrow breach when Spartacus in the year 72 encamped his gladiators in this hollow Claudius the Praetor besieged him there keeping the single outlet carefully guarded and then let down his soldiers to keep precipices which surrounded the crater at the bottom of which the insurgents were encamped on the side towards the sea the walls of this original cavity which must have been three miles in diameter have been destroyed and Breslock was the first to announce the opinion that this destruction happened during the tremendous eruption which occurred in 79 when the new cone which stands encircled on three sides by the ruins of the ancient cone called Monte Somma in the annexed diagram it will be seen that on the side of Vesuvius opposite to that where a portion of the ancient cone of Somma still remains is a projection called the pedimentina which some have supposed to be part of the circumference of the ancient crater and over the edge of which the lavas of the modern Vesuvius have poured the axis of the present cone of Vesuvius being according to Visconti precisely equidistant from the escarpment of Somma and the pedimentina in the same diagram I have represented the slanting beds of the cone of Vesuvius as becoming horizontal in the atrio del cavallo the slava flows down to this point as happened in 1822 its descending course is arrested and it then runs in another direction along this small valley circling round the base of the cone sand and scoriae also blown by the winds collect at the base of the cone and are then swept away by torrents so that there is always here a flatish plane as represented in the same manner the small interior cone must be composed of sloping beds terminating in a horizontal plane for while this Monticule was gradually gaining height by successive ejections of lava and scoriae in 1828 it was always surrounded by a flat pool of semi-fluid lava into which scoriae and sand were thrown in the steep semi-circular of Soma which faces the modern Vesuvius we see a great number of sheets of lava inclined at an angle of about 26 degrees they alternate with scoriae and are intersected by numerous dykes which, like the sheets of lava are composed chiefly of augite with crystals of lusite but the rock in the dykes is more compact having cooled and consolidated under greater pressure the rocks cut through and shift others so that they have evidently been formed during successive eruptions while the higher region of Soma is made up of these igneous products there appear on its flanks for some depth from the surface as seen in a ravine called the fossa grande beds of white pumiceous tuft resembling the tuft which at Pausilippo and other places near Naples are living Mediterranean species it is supposed by Pilla Von Buuk and others that the tuftatius beds which rise in Soma to more than half the height of that mountain are in like manner of submarine origin because a few seashells have been found in them here and there together with circulae of recent species attached to included blocks of limestone it is contended therefore that as these strata were once accumulated beneath the sea they may have been subjected as they rose to such an upward movement as may have given rise to a conical hill and this hypothesis it is said acquires confirmation from the fact that the sheets of lava near the summit of Soma are so compact and crystalline and of such breadth individually as would not have been the case had they run down a steep slope they must therefore have consolidated on a nearly level surface and have been subsequently uplifted into their present inclined position unfortunately there are no sections of sufficient depth and continuity on the flanks of Soma to reveal to us clearly the relations of the lava scoriae and associated dikes forming the highest part of the mountain with the marine tufts observed on its declivity both may perhaps have been produced contemporaneously when Soma raised its head like stromboli above the sea its sides and base being then submerged such a state of things may be indicated by a fact noticed by von Buick namely that the pumiceous beds of Naples when they approach Soma contain fragments of the peculiar lucitic lava proper to that mountain which are not found at a greater distance portions therefore of this lava were either thrown out by explosions or torn off by the waves during the deposition of the pumiceous strata beneath the sea we have as yet but a scanty acquaintance with the laws which regulate the flow of lava beneath water or the arrangement of scoriae and volcanic dust on the sides of a submarine cone there can however be little doubt that showers of ejected matter may settle on a steep slope and may include shells and the remains of aquatic animals which flourish in the intervals between eruptions lava under the pressure of water would be less porous but as Dr. Dobaini suggests it may retain its fluidity longer than in the open air for the rapidity with which the streams are cooled by being plunged into water arises chiefly from the conversion of the lower portions of water into steam which steam absorbing much heat immediately ascends and is reconverted into water but under the pressure of a deep ocean the heat of the lava would be carried off more slowly and only by the circulation of ascending and descending currents of water those portions nearest would be light and consequently displacing the water above this kind of circulation would take place with much less rapidity than in the atmosphere in as much as the expansion of water by equal increments of heat is less considerable than that of air we learn from the valuable observations made by Mr. Dana on the active volcanoes of the Sandwich Islands that large sheets of rock craters at the top or near the summits of flattened domes higher than Etna as in the case of Mt. Loa for example where a copious stream two miles broad and 25 miles long proceeded from an opening 13,000 feet above the level of the sea the usual slope of these sheets of lava is between 5 degrees and 10 degrees with which they cool in the air some lavas may occasionally form on slopes equaling 25 degrees and still preserve a considerable compactness of texture it is even proved he says from what he saw in the great lateral crater of Kilauea on the flanks of Mt. Loa that a mass of such melted rock may consolidate at an inclination of 30 degrees and be continuous such masses are narrow he admits but if the source had been more generous they would have had a greater breadth and by a succession of ejections over spreading each cooled layer a considerable thickness might have been attained the same author has also shown as before mentioned that in the cinder cones of the Sandwich Islands the strata have an original inclination of between 35 degrees Mr. Scrope writing in 1827 attributed the formation of a volcanic cone chiefly to matter ejected from a central orifice but partly to the injection of lava into dykes and quote to that force of gaseous expansion the intensity of which in the central parts of the cone is attested by local earthquakes which so often accompany eruptions it is the opinion of Mr. Bonbuque de Beaumont and de Freynoy that the sheets of lava on Soma are so uniform and compact that their original inclination did not exceed four or five degrees and that four fifths therefore of their present slope is due to their having been subsequently tilted and upraised notwithstanding the light thrown by Mr. de Beaumont on the laws regulating the flow I do not conceive that these laws are as yet sufficiently determined to warrant us in assigning so much of the inclined position of the beds of Soma to the subsequent rending and dislocation of the cone even if this were admitted it is far more in harmony with the usual mode of development of volcanic forces to suppose the movement which modified the shape of the cone to have been intermittent and gradual in sudden and violent convulsion End of Chapter 24 Part 1 Recording by Linda Johnson