Another giant disaster occurred in the Sunda archipelago in 1883: Volcano exploded Krakatau. Before the eruption it was a small archipelago of islands, the largest of which was the size of Krakatoa 9×5 km. It consisted of three conjoined craters: Rakata (800 m) – in the south, Dana (450 m) – in the center, Perbuatan (120 m) – in the northern part of the island. North-west there was another, smaller island, known Ferleyten (Desert), and to the east island Lang (Long) and a few very small islands. The entire archipelago to be remnants of a volcano a height of about two thousand meters, which was destroyed in prehistoric times.
About the beginning of a flurry of activity of the volcano we do not know – the island of Krakatoa were deserted, and only occasionally go out of town fishermen from the island of Sumatra. The first observations were made with the ship, sailing on the Sunda Strait, they date back to the time when there is a strong eruption. May 20 crew German war ship "Elizabeth" said mushroom-shaped cloud, coming out of the crater, it reached 11 thousand meters high. Despite the fact that up to Krakatau was still far away, the ash was falling on the deck of the ship. These effects lasted for several days, they have observed and from other vessels, as well as from the west coast of Java. On the whole space, up to Batavia (now Jakarta), felt the tremors were heard explosions. Went a little ash rain.
May 27 Krakatau visited some residents Batavia. It turned out that in the middle of an ancient circular crater Perbuatana every 5-10 minutes. repeated explosions, columns of vapor and ash rose to a height of 3.2 thousand meters of trees were sprinkled with a pumice stone, like snow.
In the following days the force of the eruption have eased. Until the accident, which occurred at the end of August, a time there was a violent explosion. In mid June, the trial resumed with terrible force. June 24 rock Perbuatana disappeared due to the expansion of the crater. August 11th captain of one of the ships had already found three large crater and the mass of small, well spewing fumes and ash. After that ash rain became intensified, and August 26-27 disaster. It can be observed only from vessels that were nearby, and from the shores of Java and Sumatra. If on Krakatoa and were residents, in that terrible day would not have survived a single person, as even on the island Sebesi lying at a distance of 20 km from the volcano, killing the entire population.
Morning of August 26 was clear. About an hour of the day was audible hum, which has spread to Batavia, at night it is so sore, that the city could not sleep. About two o'clock in the afternoon the ship "Medea", sailing on the Sunda Strait, saw a column of ash 27-33 km altitude. In the 17th hour. there was the first tsunami, probably caused by a collapse of the crater. In the evening in the village on the island of Sumatra Lampong went weak ash rain. In Angers, and in some villages close to it, located on the coast of the island of Java, just after sunset, the deep darkness reigned. Could hear the muffled sounds. Small vessels were filled with waves or dumped on the land and the water several times rushed to the banks and destroyed many villages. Thick clouds of ash covered the deck. Dash down huge boulders. By two o'clock in the morning the ashes on the deck, "Berben" formed a meter-thick layer of … Impenetrable darkness covered the land. On Mount Krakatoa was heard rumbling and continually shows vivid lightning. The atmosphere felt electricity, the rigging and masts were visible flames St. Elmo, writhing like a "fiery serpents." Steering to "Berbice" could barely stand in its place – touching the metal parts of steering, he felt a strong electric shock.
August 27 morning, the sky was clearer, but soon again all around was covered with thick darkness that lasted 18 hours. The huge mass of ash, pumice, slag and viscous, similar tests, mud went to Sunda Strait, to the islands of Java and Sumatra. At 6:00. AM waves rushed to the low-lying coast.
About 10 o'clock in the morning was the worst time: there was a huge explosion. Gas, vapor, ash and rock fragments have been raised to a height of 70-80 km and scattered over the area of 1 million km2.
Explosion caused monstrous waves rose like mountains, reaching up to 30 m in height, one by one, they dash down to the islands. Towns, villages, forests, railway embankment that runs along the coast of Java – everything was wiped out a terrible flood. Angers, Bentham, Merak and others were destroyed. All Islanders Sebesi Serami and was buried. Only a few managed to miraculously escape the sad fate: the first wave of flooding in the ground, was fascinated with the people at some later thrown ashore unharmed.
What was going on with the survivors, it is difficult to describe. Terrified residents exert all their strength, seeking salvation. Darkness shrouded everything. In 10 hours. 54 min. there was a second explosion, about the same giant, like an hour before, but not accompanied by a tsunami. The next burst of weak tsunami occurred in 16 hours. 35 min. Ashy rain, explosions, storm and tempest in the sea did not stop all night, but their strength is waning. August 28 morning, the sky was brighter again, eruption weakened, but it is not over. Small explosions occurred in September and October, and February 20, 1884, it was noted last eruption.
Coast of Sumatra and Java have changed beyond recognition. Familiar places can be found except on the situation, but not in appearance. Rich tropical vegetation has disappeared without a trace wherever the waves appeared. The land was completely bare; gray dirt and eruptions, uprooted trees, the remains of buildings, bodies of people and animals littered it. On the surface of the Sunda Strait surfaced mass of pumice. According to official figures, the death toll was approximately 40 thousand people. At the site of the island of Krakatoa spilled sea, and the water comes to the surface just an old volcanic cone, which is cracked in half, one half fell into the sea, and the other opened striking, terrifying underground lab forces (Fig. 11).
Wave in the sea (tsunami), caused by the explosion of Krakatoa, was so powerful that it bypassed the entire planet. On the coast of the Indian Ocean waves were observed, more or less severe depending on the distance from Krakatoa. The excitement has spread well throughout the Pacific and reached the western coast of America. In the Atlantic Ocean tsunami, caused by the explosion of the Sunda archipelago, seen off the coast of France and on the Isthmus of Panama.
The roar of Krakatoa explosion was heard at a great distance. In Baydenzorge, on the island of Java, about 150 km from the volcano, the blow was so strong that the windows and doors of many houses off its hinges, and with the power to crumble plaster. The roar of the eruption was heard in the city of Manila, spaced at two thousand miles from Krakatau, as well as in Central Australia, a distance of 3,600 km, and the island of Madagascar in 4775 km from Krakatoa (Fig. 12).
In the atmosphere, as there is a rapid change. Near Krakatau severe storms raged. In Europe, North America and other parts of the world air movement was observed meteorological instruments, and everywhere seen to severe wobble barometer. Air wave, caused by the eruption of Krakatoa, went around the globe three times, it has been proved barometric observations at different locations.
In Berlin, the first air wave was observed after 10 h. after the disaster. If it is assumed that it came on the shortest path, its velocity was about 1000 km / h After 16 hours. Again there was hesitation barometer. It caused the same air wave, but came from the other side of the world, by way of the United States. Going further, the wave again and circled the globe in 36 hours. returned to Berlin. Wave makes its way across America, again appeared in Europe in 34-35 hours. Its acceleration is attributed to the fact that in the upper atmosphere, the air currents are directed predominantly from west to east. The third time is the movement of air came to Berlin in 37 hours. Then the force of air vibrations gradually decreased.
In the entire history of mankind is not mentioned about any eruption, which would be just as strong sound phenomena.
Since the eruption of the volcano Krakatoa connected another remarkable phenomenon. Shortly after the accident, in late August, the sun took a kind of green. First, this phenomenon has been seen only near Krakatoa, and then at a considerable distance from it. It has been observed in Ceylon, a little later on the island of Mauritius, then to the west coast of Africa, and finally, in Brazil, Central America and many other places. Original color of the sun to explain the accumulation of tiny particles of volcanic ash, which were worn in the upper atmosphere.
In late November 1883 in Europe, it was noted a strange phenomenon. At sunset the sun's rays were given purple glow in the sky that does not disappear for a long time, after which there is complete darkness. Soon everywhere began to receive such news. In some places, this phenomenon is seen before in Europe, but before the eruption of Krakatoa is not observed anywhere.
Around the same time, in many parts of Europe was a rain of dust covered the ground like snow. The study showed that the dust consists of tiny crystals, like the ashes of Krakatoa.
Krakatoa eruption products consisted mainly of fine ash and pumice. It is believed that the amount of their income to 18 km3. 6 km radius of the volcano in igneous rocks piled thick layers 20-40 m to the north of Krakatoa, the island Sebesi, water depth before eruption was 36 meters after the accident were exposed stranded here and it all became non-navigational space for large ships. As a result of explosions kept only the southern half of Rakata cone, and the place the rest of it was formed on the sea floor depression, consisting of two basins: one, to a depth of 120 m, is located between the islands of Ferleyten Lang and, the other, a depth of 300 m, with even down – to the south.
Not only was a change of the seabed, but also created new islands, and the former increased in size. The ruins of the Krakatoa eruption products formed an area of 5 km2. Island Lang increased 0.3 km2 Ferleyten – more than 8 km2, one island had disappeared – was probably washed away by waves. It also appeared Islands Streera area of 3 km2 and Kalmeyera – 4 km2. Both are above the surface of the sea is only a few meters, but soon disappeared under the water again.
From a distance, it seemed that the island's smoke. In fact it was the steam rising from the high piles of igneous masses. Weight pumice covered the surface of the sea like these floating islands, which stood at 2 m above the sea surface. In Sumatra, at the entrance to the bays and Lampong Semanka, floating layers of pumice had such power that the highest court could hardly cut it. Ashes took area of 750 km2.
The study of the geological structure of the volcano Krakatoa, conducted in the last century, can adequately reconstruct the history of its development. A contemporary caldera – a ring-shaped strip of rocks left over after the explosion, shown in Fig. 13. In the history of the formation of the caldera of Krakatau distinguish four periods (Fig. 14). Originally on the site of today's caldera originated volcanic cone rising above the level of the ocean by about 2 thousand meters It was built so-called "ancient andesite."
This period of development over the caldera collapse of the central part of the cone of the volcano, from which there were three small islands on the periphery of the caldera.
During the second period in the southeast of the caldera, a new Rakata cone height of 800 m, composed mainly of basalt.
In the third period, formed two small andesitic cone – Dan and Perbuatan. All three of the cone formed a relatively large island. In 1670, from the crater lava flow poured Perbuatana andesite composition, followed by 200 years of Krakatoa was silent.
The fourth period in the life of Krakatau – a disaster in 1883
The last stage of the caldera of Krakatau (after 1883) associated with the growth of a new volcanic cone of Anak Krakatau, beginning in late 1927 its eruptions have occurred in the early 50's and later. So, in 1960, Anak Krakatau, threw thin ash material and debris up to 2 m in diameter at intervals of 5 to 10 minutes. Three years later, it was noticed the disappearance of the crater lake and the growth of the inner cone.
Although in a weaker form, the volcano Krakatau continues to live in the present. Above the crater a few hundred meters column of smoke rises, and at night visible emissions of hot gases.
Emerged after the explosion caldera Krakatau has two pools. The smaller of them is located between the islands of Lang and Ferleyten and reaches a depth of 70 m with two indentations on 120 m second, larger, located south of the basin. Its maximum depth is 279 m
Krakatoa caldera explained differently. Some scholars have suggested that caldera is the result of a giant explosion, and is not nothing but a crater resembling somewhat funnel blast fragmentation bombs. But now, most researchers are inclined to conclude that the caldera of Krakatau arose due to the volcanic chamber roof collapse caused by the removal of this camera is the huge amount of volcanic material. In this regard, the formation of the caldera is somewhat reminiscent of the collapse of the earth's surface at a mine workings, of which the removed rock.
Confirmation of the latter view are repeated measurements of the caldera of Krakatau. Measurements taken in 1923, that is, 40 years after the accident, showed that in two places, has the greatest depth, bottom deepened with 162 and 210 to 179 and 274 m depth in other places has increased from 80 to 250 m, etc. The analysis of the longitudinal profile of a caldera has shown that lowering the bottom was not as tapered sliding surfaces, and almost vertical. The reason for these moves are the reduction of the amount due to the underground chambers of magma crystallization rest or moving it to a new mouth of the volcano, Anak Krakatau erupted in 1927, is also possible that this is the result of "adaptation" to the new unit of surface topography emptied underground volcanic chamber.