WE know that the effects of the stupendous volcanic eruption in the Strait of Sunda extended through many months and were exerted over a large area of surface. From the newspapers of the day we learned much of the horrors that attended this unusual convulsion, and of the disasters which followed. But as information is gathered and collated, it is possible to present an interesting summary of this great effort of nature.
The eruption was at Krakatoa, an island in the fair-way of the Strait of Sunda, about midway between Java and Sumatra. Twenty-six miles to the southward and westward was the village of Anjer, where were a light-house and signal-station for the many vessels passing through the strait.
Krakatoa was but a small, uninhabited island, about five miles long and three miles wide. It had two elevations, of which the taller, called the Peak of Krakatoa, rose 2750 feet above the sea. On the adjacent land are volcanic cones; some active, some slumbering, and others dead.
It is recorded that Krakatoa itself was active in 1680, and that voyagers in the vicinity encountered in that year a great storm and an earthquake at sea, accompanied by most frightful thunders and cracklings. Mention was also made of a strong sulphur atmosphere and of large quantities of pumice floating on the sea. Since that time the island had been at rest, and was noted by travelers chiefly for the beauty of its tree-clad slopes, the first verdant spot to greet the eye after long weeks at sea.
So far as is known, the earliest indication of any subterranean disturbance was felt at Batavia, eighty miles distant, on the 20th of May, 1883; and it is a remarkable fact that while the commotion about to be described was taking place at Batavia, nothing unusual was noticed at Anjer, but twenty-five miles away, nor at Merak, thirty-five miles distant from Krakatoa, although from both places there is a clear outlook to that island.
In the forenoon of the 20th of May the inhabitants of Batavia were startled by a dull booming noise, followed by a violent rattling of doors and windows. Whether this proceeded from the air or from below was a matter of doubt, for unlike most earthquake shocks the quivering was only vertical. The director of the observatory in Batavia reported the next day that no increase of earth magnetism accompanied the tremblings, and that a suspended magnet with a registering apparatus gave no indications of the slightest horizontal oscillations. An instrument maker in the town stated that on a pendulum in his shop only vertical trillings were observable, at a time when the windows and glass doors were rattling in so violent a way as to render conversation a matter of no little difficulty. Nowhere do there seem to have been observed any shocks of a true or undulatory earthquake. Another curious circumstance was that at midday at some spots in the city no vibrations were perceived, while in the surrounding buildings they were distinctly experienced. It was a natural conclusion, however, that an alarming volcanic eruption had taken place; but it was impossible to localize the direction of the sounds, and at the observatory there were no instruments for making such determinations.
The tremblings continued throughout the day and during the forenoon of the 21st. A thin sprinkling of ashes fell at Telok Betong and at Semangko, in Sumatra; whence the ashes came, no one could tell. At Buiteuzorg, thirty miles south of Batavia, the same phenomena were observed; while in the mountains farther to the southwest they were even more pronounced. By this time general opinion had ascribed to the west or northwest the direction whence the movements were proceeding. Krakatoa itself was mentioned, but some of the mountains in Sumatra were considered more likely to be the seat of disturbance.
On the evening of May 21st smoke was seen issuing from Krakatoa, and on the 22d it was evident that the volcanic vent was at that place. Shortly afterward the vibrations in Batavia ceased. During the next eight or nine weeks the eruption continued with great vigor, ejecting masses of pumice and molten stone, and volumes of steam and smoke. Although the prevailing monsoon carried to the westward the greater part of the matter thrown out, a cloud of lighter particles rose higher, and, encountering an easterly current of air, some of the dust fell on the island of Timor, twelve hundred miles distant.
During these weeks vessels passed through extensive fields of pumice spread over the surface of the sea. Some of these pumice nodules, picked up about the 11th or 12th of July, in latitude 6° S. and longitude 94° E., were very large and considerably worn; several lumps were covered with barnacles an inch long, which represented at least four weeks' growth. On August 1st, in latitude 6° S., longitude 89° E., seven hundred miles from the coast of Sumatra, a steamer passed through a field of floating pumice; and here the current was running eastward fifteen to thirty miles a day. The soundings at the spot reached two thousand fathoms. It is known that a centre of volcanic disturbance exists in the Keeling Atoll, situated six hundred miles west by south from the mouth of the strait; and it is also known that pumice ejected from the sea bottom rises to the surface. The currents of the Indian Ocean will show that any flotsam in the region between west and south of Java Head in that longitude could be drifted to the locality in which it was observed in the month of July.
In a paper read before the Royal Geographical Society, Mr. Forbes suggested that the sounds heard in Batavia on the 20th of May, which were unnoticed at places so near Krakatoa as Anjer and Merak, and which would be inexplicable if they really originated there, were the result of a submarine eruption in the Indian Ocean, somewhere southwesterly from Java Head; and that the tremors were propagated thither, perhaps, by continuous strata connecting the locale of the outburst with Batavia, Buitenzorg, and more especially with the hills to the southwest, where the manifestations were so distinctly perceived.
If such a submarine outburst did take place, Mr. Forbes suggested that somehow the orifice very soon became blocked after a great inrush of water had taken place, which, becoming transformed into steam under enormous pressure, shaped its course for the nearest old earth scar, and found vent in Krakatoa by an offshoot, probably, of the funnel of the eruption of 1680.
That such large lumps of pumice should he carried westward seven hundred miles into the Indian Ocean does not seem probable, especially as the earlier outbursts were not of very unusual vigor, for no pieces of any size are reported to have fallen on the neighboring coasts of Java and Sumatra; even after those of August, no ship farther off than one hundred miles speaks of the fall of any but the finest dust and sand.
On the 21st of August the volcano increased in activity. A ship reported being unable to venture into the strait on account of the great shower of pumice and ashes. On the afternoon of the 26th there were violent explosions at Krakatoa, which were heard as far as Batavia. High waves first retreated, and then rolled upon both sides of the strait. During a night of pitchy darkness these horrors continued with increasing violence, augmented at midnight by electrical phenomena on a terrifying scale, which not only enveloped the ships in the vicinity, but embraced those at a distance of ten to twelve miles. The lurid gleam that played on the gigantic column of smoke and ashes was seen in Batava, eighty miles away. Some of the debris fell as fine ashes in Cheribon, five hundred miles to the eastward.
On the morning of the 27th there was a still more gigantic explosion, heard in the Andaman Islands and in India, which produced along both shores of the strait an immense tidal movement, occasioning that great loss of life recounted in the daily press. The matter expelled rose to an elevation so tremendous that, on spreading itself out, it covered the whole western end of Java and the south of Sumatra for hundreds of square miles with a pall of impenetrable darkness. Abnormal atmospheric and magnetic displays were observed, compass needles rotated violently, and the barometer rose and fell many tenths of an inch in a minute. Between ten and twelve o'clock in the forenoon of that day the subterranean powers burst their prison walls with a terrific detonation, which spread consternation and alarm among the dwellers within a circle whose diameter lay across nearly three thousand miles.
The description given at the San Francisco Hydrographic Office by Captain Watson, of the British ship Charles Bal, who was in the near vicinity at that time, is especially graphic and thrilling. He says that at "about seven P.M. on the 22d of August, in latitude 15° 30' S. and longitude 105° E., the sea suddenly assumed a milky-white appearance, beginning to the eastward, but soon spreading all around, and lasting until about eight P.M. There were some cumulus clouds in the sky, but many stars were shining, and from E. to N. N. E. a strong white haze, or silvery glare; this occurred again between nine and ten P.M., but disappeared when the moon rose. The clouds appeared to be edged with a pinkish-colored light; the sky also seeming to have extra light in it, as when the Aurora is showing faintly.
"On the 24th, in latitude 90° 30' S., longitude 105° E., this was repeated, showing when the sky was overcast, but disappearing when the moon rose.
"On the night of the 25th, standing in for Java Head, the land was covered with thick dark clouds, and heavy lightning was frequent. On the morning of the 26th made Java Head light; ahout nine A.M. passed Prince's Island, and had a sharp squall from W. S. W., with torrents of rain.
"At noon Krakatoa was N. E. of us; but only the lower portion of the east point was to he seen, the rest of the island being enveloped in heavy blackness.
"At 2.30 P.M. we noticed some agitation about the point of Krakatoa, clouds or something being propelled from the N. E. point with great velocity. At 3.30 we heard above us and about the island a strange sound, as of a mighty crackling fire, or the discharge of heavy artillery at one or two seconds' interval. At 4.15 Krakatoa bore N. one half E., ten miles distant. We observed a repetition of the noise noted at 3.30, only much more furious and alarming; the matter, whatever it was, being propelled with amazing velocity to the N. E. To us it looked like blinding rain, and had the appearance of a furious squall, of ashen hue. At once shortened sail, to topsails and foresail. At five the roaring noise continued and was increasing; darkness spread over the sky, and a hail of pumice stone fell on us, of which many pieces were of considerable size and quite warm. We were obliged to cover up the skylights to save the glass, while our feet and heads had to be protected with boots and sou-westers. About six the fall of larger stones ceased, but there continued a steady downpour of a smaller kind, most blinding to the eyes, and covering the deck to a depth of three or four inches very speedily. While an intense blackness covered the sky and land and sea, we sailed on our course, until at seven P.M. we got what we thought was a sight of Fourth Point light; then brought ship to the wind, S. W., as we could not see to any distance, and knew not what might be in the strait.
"The night was a fearful one: the blinding fall of sand and stones, the intense blackness above and around us, broken only by the incessant glare of varied kinds of lightning, and the continued explosive roars of Krakatoa made our situation a truly awful one.
"At eleven P.M., having stood off from the Java shore, with the wind strong from the S. W., the island, being W. N. W. distant eleven miles, became visible. Chains of fire appeared to ascend and descend between it and the sky, while on the S. W. end there seemed to be a continued roll of balls of white fire. The wind, though strong, was hot and choking, sulphurous, with a smell as of burning cinders, some of the pieces falling on us being like iron cinders. The lead came up from the bottom at thirty fathoms quite warm.
"From midnight to four A. M. of the 27th, the wind was strong but unsteady between S. S. W. and W. S. W. The same impenetrable darkness continued, while the roaring of Krakatoa was less continuous but more explosive in sound; the sky one second intensely black, the next a blaze of light. The mast-heads and yard-arms were studded with corposants, and a peculiar pink flame came from fleecy clouds which seemed to touch the mast-heads and yard-arms.
"At six A. M., being able to make out the Java shore, set sail and passed Fourth Point light-house. At eight hoisted our signal letter, but got no answer. At 8.30 passed Anjer with our name still hoisted, and close enough in to make out the houses, but could see no movement of any kind; in fact, through the whole strait we did not see a single moving thing of any kind on sea or land.
"At 10.15 passed the Button island one half to three fourths of a mile off, the sea being like glass all around it, and the weather much finer looking, with no ashes or cinders falling; wind light at S. E.
"At 11.15 there was a fearful explosion in the direction of Krakatoa, then over thirty miles distant. We saw a wave rush right on to the Button island, apparently sweeping entirely over the southern part, and rising half-way up the north and east sides, fifty or sixty feet, and then continuing on to the Java shore. This was evidently a wave of translation, and not of progression, for it was not felt at the ship. This we saw repeated twice, but the helmsman said he saw it once before we looked. At the same time the sky rapidly covered in; the wind came out strong from S. W. to S., and by 11.30 A. M. we were inclosed in a darkness that might almost be felt; and then commenced a downpour of mud, sand, and I know not what, the ship going N. E. by N. seven knots per hour under three lower topsails. We set the side lights, placed two men on the lookout forward, the mate and second mate on either quarter, and one man washing the mud from the binnacle glass. We had seen two vessels to the N. and N. W. of us before the sky closed in, which added not a little to the anxiety of our position.
"At noon the darkness was so intense that we had to grope our way about the decks, and although speaking to each other on the poop, yet we could not see each other. This horrible state and downpour of mud and debris continued until 1.30 P.M., the roaring and lightning from the volcano being something fearful. By two P.M. we could see some of the yards aloft, and the fall of mud ceased; by five P.M. the horizon showed out to the northward aud eastward, and we saw West Island bearing E. by N., just visible. Up to midnight the sky hung dark and heavy, a little sand falling at times, and the roaring of the volcano very distinct, although we were fully seventy-five miles from Krakatoa. Such darkness and such a time in general, few would conceive, and many, I dare say, would disbelieve. The ship from truck to water-line was as if cemented; spars, sails, blocks, and ropes were in a horrible state; but, thank God, no one was hurt, nor was the ship damaged. But think of Anjer, Merak, and other little villages on the Java coast!"
At sunrise on the 28th of May the darkness began gradually to clear away, and then was seen the result of this paroxysm of nature. The northwestern part of Krakatoa Island had disappeared. The line of fracture began at a point south of Lang Island, and formed an arc of a circle passing through the peak to the western side of the island. Boats from the U. S. S. Juniata entered the crater-like area, concave to the northward, and sounded along the face of the heights; but no bottom could be found with twenty fathoms of line. Prior to the eruption, Verlaten and Lang islands were green with trees and foliage; they are now covered with scoria. Eastward of Verlaten a small island had formed; small necks of land had been thrown out from the eastern side of Verlaten and the western point of Krakatoa. The Polish Hat had disappeared, but a new rock, about twenty feet in height and as many in diameter, now existed in Krakatoa channel, near to the southern point of Lang Island. Within ten yards of this rock there were eight fathoms of water. At the place occupied by the Polish Hat the boats found no bottom with twenty fathoms of line, while at the spot where the volcano had been so active later soundings showed no bottom at one hundred and sixty-four fathoms, nearly one thousand feet. To the northward and eastward two new islands, Steers and Calmeyer, had formed, where before the eruption were thirty to forty fathoms of water.
It has been thought that the first great waves on the evening of the 26th were caused by a portion of Krakatoa being shot out northwards for eight miles, and dropped where now is Steers Island; while the terrific detonation on the 27th, and the greater wave accompanying it, resulted perhaps from that still more titanic effort which lifted the greater portion of Krakatoa, hurled it through the air over Lang Island, and plunged it into the sea where Calmeyer Island now blocks the old East Passage.
The captain of the Juniata stated in his report that he anchored off the site of Anjer, and that "the buoys which mark the line of the submarine cable to Telok Betong, Sumatra, and the base of the light-house at Fourth Point are the only monuments of Anjer. The plain northward of Anjer peak was swept by the flood of waters, and nothing remains but the vine-like roots of the cocoa palm and some scattered and ghastly relics of the inhabitants.... Communication with Telok Betong is now interrupted by masses of floating pumice wedged in Lampong Bay."
A vessel which passed through Gaspar Strait as late as the 23d of November reported that at places in the Java Sea the floating pumice was so thick that headway was almost impossible with light breezes.
And yet another reported that on December 21, 1883, in the S. W. part of the Java Sea, quantities of pumice stone, large trees, bushes, and roots were encountered.
The tidal phenomena which followed this convulsion are particularly interesting. The waves formed in the narrow strait issued into the oceans east and west, and started on their journey around the globe. The undulations were registered at Mauritius, the Seychelles, in South Africa, and on the shores of the Pacific Islands on the same day that the Java villages were swept away. The waves continued their course, crossed each other at the antipodes of Krakatoa, and returned to the spot from which they had started. Four times did they go around the earth before the equilibrium of the sea was so far restored as to be insensible to instruments.
At the same time an atmospheric wave also started around the globe. These disturbances were noted wherever there were barographs, and the dates are thus fixed when these undulations passed various places on the surface of the earth.
For instance, at St. Petersburg, on August 27th, there was a rise of the mercury, and immediately afterwards a fall. At Valencia, in Ireland, and at Coimbra, in Portugal, similar phenomena were noticed, and shortly afterward the disturbance was observed all over Europe, wherever a barograph was at hand. At the western observatories the movement was more pronounced than at the eastern, but the general appearances of the curves at neighboring stations were about the same. This disturbance moved rapidly from east to west, requiring but two hours and twenty-five minutes to travel from St. Petersburg to Valencia, a distance of thirteen hundred and fifty miles. On the 28th there was a somewhat similar disturbance which moved from west to east, requiring a little less than two hours to pass from Valencia to St. Petersburg. On the 29th there were two well-defined movements: one early in the morning, from east to west, occupying two hours and eight minutes from St. Petersburg to Valencia; and the other in the afternoon, from west to east, reaching St. Petersburg one hour and twenty-five minutes after it was observed at Valencia. Similar phenomena, less defined, were noted on the 30th and 31st.
Coincident with these atmospheric fluctuations, magnificent sunlight effects, lurid skies, prolonged dawns, and lengthened twilights were observed. The captain whose experience has here been given at some length states that on September 9, 1883, in latitude 140° N., longitude 114° E., the sun rose perfectly green, and so continued for forty-eight hours; and that the moon and the stars gave a green light as well. He also reports that he noticed peculiar red sunsets in the South Atlantic several weeks before the Java eruption, and that he carried them through to Hong Kong, and from there nearly across to San Francisco. The volcanic cloud that caused these peculiar effects seems to have followed a straight path, for they appeared on the east coast of Africa on the second day, on the Gold Coast on the third, at Trinidad on the sixth, and at Honolulu on the ninth day. It is impossible to say how high the lighter matter was carried; it is certain that months have been required for it to descend. The places situated below the direct path of the cloud were the first to have those ominous displays, which varied in intensity according to their time distance to the westward; for the cloud was at first elevated as a comparatively narrow column. This column gradually spread out north and south, until the inhabitants of all lands obtained a view of the beautiful effects of broken and absorbed sunbeams, and a demonstration of the power of that steam which was imprisoned by the last convulsion of nature.
NOTE. The data from which this article is compiled has been taken from reports sent to the U. S. Hydrographic Office, from the preliminary survey of the U. S. S. Juniata, and from the Proceedings of the Royal Geographical Society.