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KRAKATOA (KRAKATAO, KRAKATAU)
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See also:KRAKATOA (KRAKATAO, KRAKATAU) , a small volcanic See also:island in Sunda Strait, between the islands of See also:Java and See also:Sumatra, celebrated for its eruption in 1883, one of the most stupendous ever recorded. At some See also:early See also:period a large See also:volcano See also:rose in the centre of the See also:tract where the Sunda Strait now runs. See also:Long before any See also:European had visited these See also:waters an See also:explosion took See also:place by which the See also:mountain was so completely blown away that only the See also:outer portions of its See also:base were See also:left as a broken See also:ring of islands. Subsequent eruptions gradually built up a new See also:series of small cones within the See also:great See also:crater ring. Of these the most important rose to a height of 2623 ft. above the See also:sea and formed the See also:peak of the volcanic island of Krakatoa. But compared with the great neighbouring volcanoes of Java and Sumatra, the islets of the Sunda Strait were comparatively unknown. Krakatoa-was uninhabited, and no satisfactory See also:map or See also:chart of it had been made. In 168o it appears to have been in eruption, when great earthquakes took place and large quantities of See also:pumice were ejected. But the effects of this disturbance had been so concealed by the subsequent spread of tropical vegetation that the very occurrence of the eruption had sometimes been called in question. At last, about 1877, earthquakes began to occur frequently in the Sunda Strait and continued for the next few years. In 1883 the manifestations of subterranean commotion became more decided, for in May Krakatoa See also:broke out in eruption. For some See also:time the efforts of the volcano appear to have consisted mainly in the See also:discharge of pumice and dust, with the usual See also:accompaniment of detonations and earthquakes. But on the 26th of See also:August a See also:succession of paroxysmal explosions began which lasted till the See also:morning of the 28th. The four most violent took place on the morning of the 27th. The whole of the See also:northern and See also:lower portion of the island of Krakatoa,.lying within the See also:original crater ring of prehistoric times, was blown away; the northern See also:part of the See also:cone of Rakata almost entirely disappeared, leaving a See also:vertical cliff which laid See also:bare the inner structure of that volcano. Instead of the volcanic island which had previously existed, and rose from 300 to 1400 ft. above the sea, there was now left a submarine cavity, the bottom of which was here and there more than See also:I000 ft. below the sea-level. This prodigious evisceration was the result of successive violent explosions of the superheated vapour absorbed in the molten magma within the crust of the See also:earth. The vigour and repetition of these explosions, it has been suggested, may have been caused by sudden inrushes of the See also:water of the ocean as the See also:throat of the volcano was cleared and the crater ring was lowered and ruptured. The See also:access of large bodies of See also:cold water to the See also:top of the See also:column of molten See also:lava would probably give rise at once to some See also:minor explosions, and then to a chilling of the See also:surface of the lava and a consequent temporary diminution or even cessation of the volcanic eructations. But until the pent-up water-vapour in the lava below had found See also:relief it would only gather strength until it was able to burst through the chilled crust and overlying water, and to hurl a vast See also:mass of cooled lava, pumice and dust into the See also:air. The amount of material discharged during the two days of paroxysmal See also:energy was enormous, though there are no satisfactory data for even approximately estimating it. A large cavity was formed where the island had previously stood, and the sea-bottom around this crater was covered with a wide and thick See also:sheet of fragmentary materials. Some of the surrounding islands received such a thick See also:accumulation of ejected stones and dust as to See also:bury their forests and greatly to increase the See also:area of the See also:land. So much was the sea filled up that a number of new islands rose above its level. But a vast See also:body of the See also:fine dust was carried far and wide by aerial currents, while the floating pumice was transported for many hundreds of See also:miles on the surface of the ocean. At See also:Batavia, See also:loo m. from the centre of eruption, the See also:sky was darkened by the quantity of ashes See also:borne across it, and lamps had to be used in the houses at midday. The darkness even reached as far as Bandong, a distance of nearly 15o miles. It was computed that the column of stones, dust and ashes projected from the volcano shot up into the air for a height of 17 in. or more. The finer particles coming into the higher layers of the See also:atmosphere were diffused over a large part of the surface of the earth, and showed their presence by the brilliant sunset glows to which they gave rise. Within the tropics they were at first borne along by air-currents at an estimated See also:rate of about 73 M. an See also:hour from See also:east to See also:west, until within a period of six See also:weeks they were diffused over nearly the whole space between the latitudes 30° N. and 45° S. Eventually they spread northwards and southwards and were carried over See also:North and See also:South See also:America, See also:Europe, See also:Asia, South See also:Africa and See also:Australasia. In the Old See also:World they spread from the north of Scandinavia to the Cape of See also:Good See also:Hope. Another remarkable result of this eruption was the world-wide disturbance of the atmosphere. The culminating See also:paroxysm on the morning of the 27th of August gave rise to an atmospheric See also:wave or oscillation, which, travelling outwards from the volcano as a centre, became a great circle at 18o° from its point of origin, whence it continued travelling onwards and contracting till it reached a See also:node at the See also:antipodes to Krakatoa. It was then reflected or reproduced, travelling backwards again to the volcano, whence it once more returned in its original direction. " In this manner its repetition was observed not fewer than seven times at many of the stations, four passages having been those of the wave travelling from Krakatoa, and three those • of the wave travelling from its antipodes, subsequently to which its traces were lost " (See also:Sir R. See also:Strachey). The actual sounds of the volcanic explosions were heard over a vast area, especially towards the west. Thus they were noticed at See also:Rodriguez, nearly 3000 See also:English miles away, at See also:Bangkok (1413 M.), in the Philippine Islands (about 1450 m.), in See also:Ceylon (2058 m.) and in West and South See also:Australia (from 1300 to 2250 m.). On no other occasion have See also:sound-waves ever been perceived at anything like the extreme distances to which the detonations of Krakatoa reached. Not less See also:manifest and far more serious were the effects of the successive explosions of the volcano upon the waters of the ocean. A succession of waves was generated which appear to have been of two kinds, long waves with periods of more than an hour, and shorter but higher waves, with irregular and much briefer intervals. The greatest disturbance, probably resulting from a See also:combination of both kinds of waves, reached a height of about 50 ft. The destruction caused by the See also:rush of such a body of sea-water along the coasts and See also:low islands was enormous. All vessels lying in See also:harbour or near the See also:shore were stranded, the towns, villages and settlements See also:close to the sea were either at once, or by successive inundations, entirely destroyed, and more than 36,000 human beings perished. The sea-waves travelled to vast distances from the centre of See also:propagation. The long wave reached Cape See also:Horn (7818 See also:geographical miles) and possibly the English Channel (11,040 M.). The shorter waves reached Ceylon and perhaps See also:Mauritius (2900 m.). See R. D. M. Verbeek, Krakatau (I3atavia, 1886) ; " The Eruption of Krakatoa and Subsequent Phenomena," See also:Report of the Krakatoa See also:Committee of the Royal Society (See also:London, 1888). Additional information and CommentsThere are no comments yet for this article.
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