What kind of volcano is Krakatoa


Krakatau - Chronicle of the 1883 disaster

On August 27, 1883, the Krakatau volcano destroyed itself in a huge explosion. The crack of the detonation could be heard thousands of kilometers away. Inaudible pressure waves traveled around the globe seven times. Tide meters recorded level fluctuations of several centimeters in the English Channel between France and Great Britain. In the months that followed, people raved about beautiful sunsets and at the same time complained about falling global temperatures. The worst, however, were the huge tsunamis that were triggered by the eruption of the Krakatau volcano - on the island of the same name between Java and Sumatra. At least four of these gigantic waves struck the coasts and devastated 165 villages and towns. Waves up to 40 meters high rolled several kilometers into the hinterland. They captured the coastal steamship "Berouw" and set it down - almost undamaged - three and a half kilometers further inland in a stream.
What the tidal waves spared, the pyroclastic currents destroyed. These raced over the sea at 800 km / h and were only stopped in the coastal mountains of Sumatra. Huge amounts of volcanic ash and rocks were blown into the atmosphere. Eyewitnesses reported whole pumice islands that turned the waters of the Sunda Strait into a thick paste. More than 36,400 people died in the most powerful eruption in modern times.
But what triggered the greatest volcanic catastrophe of modern times? And: Was it the greatest catastrophe at all? The second question can be answered immediately with "no". The eruption of Tambora on Sumbawa in 1815 was far stronger than that of Krakatau. The difference in the level of awareness of the two volcanoes is due to the fact that shortly before the Krakatau catastrophe a submarine cable was laid, with the help of which the latest news could be telegraphed worldwide and practically in real time. For the first time the whole world took part in the events in Indonesia, because after a short time you could read about them in newspapers in Europe. It is thanks to this fact that the Krakatau eruption burned itself into the collective memory of mankind and became a synonym for the volcanic catastrophe.
Although one always speaks of the island of Krakatau, Krakatau was part of an island archipelago even before the disaster. The 800 meter high main island consisted of the volcanoes Rakata, Danan and Perbowatan and was flanked by the islands of Verlaten Island and Lang Island.

Pictures from Anak Krakatau

Outline of Krakatoa before the great eruption.

The young island of Anak Krakatau.

Anak Krakatau eruption in June 2009.

The first indications of the impending catastrophe appeared as early as May of 1883. It began with a tremor that a lighthouse keeper registered on May 10th. A slight earthquake shook its tower. The sea foamed up and then became very calm before the normal swell set in again. Five days later, a similar but more powerful event followed, reported by a Dutch inspector in Ketimbang. Even then, the Sunda Strait between Sumatra and Java was a busy shipping route through which goods traffic between the Dutch East India Company and Europe was handled. At least ten ships were cruising near Krakatau when the volcano erupted on May 20th. The captain of the German warship "Elisabeth" reported a white, umbrella-shaped cloud that rose about eleven kilometers and caused a light rain of ash to fall on the deck.
Europe first learned of the events in the Sunda Strait three days later in a brief telegraphic message. A Lloyd's agent reported from Jakarta that the Krakatau volcano had erupted violently. His brief statement was based on a detailed report by a Mr. Schuit. This reported long-lasting eruptions, the rumble and tremors of which bridged the 50 kilometers as the crow flies that separated the coastal town of Anyer from Krakatau. The first eruptions lasted for over 24 hours, and from the coast the residents saw Krakatau shrouded in smoke. At night a red glow came over to them. A skipper who passed the island on May 22nd told of flames that broke from the summit and of burning vegetation.
The last phase in the life of Krakatau began on Sunday, August 26th, 1883. At 13:06, the rumble of an explosion tore the Sunday idyll in the Dutch colonial towns on the coasts of Java and Sumatra. The residents startled from their lunch tables and looked confused at the sea, from where the roar was coming. Disaster survivors later described the sound of the massive explosion as the loudest they had ever heard. Those who looked across the sea through the haze saw a huge white cloud that was spreading rapidly. It darkened noticeably as the afternoon wore on, and some eyewitnesses reported a dark gray cloud. Around 2 p.m. it was so dark in the coastal towns on Java that the lanterns had to be lit. By late afternoon, the eruption column had reached a height of about 27 kilometers. The first boats in the port of Anyer broke loose and cut the telegraph connection to the capital Batavia, today's Jakarta.
Around 8 p.m. the detonations of the eruption increased again. The sea foamed and boiled in a wild swell, and the breakers crashed on the coasts. The explosions could still be heard in Jakarta, 150 kilometers away, and gas lamps went out due to the fluctuations in air pressure. There followed a few quieter hours in which Krakatau gathered his strength for the final blow.
At 5:30 am, the first of four gigantic explosions occurred; the second at 6.44 a.m. The cities of Telukbetung and Anyer disappeared in the tsunamis caused by the explosions.
At 8:20 a.m. there was another detonation. The entire coast was now shrouded in absolute darkness and it was unusually cool. Presumably seawater penetrated through cracks in the flank of the Krakatau volcano and triggered the disaster. The water evaporated suddenly and increased its volume by 1500 times. Phreatomagmatic eruptions followed, which are among the most powerful eruptions in the world of volcanoes. The tremendous pressure of the eruptions emptied the magma chamber.
At 10.02 a.m. the last and worst explosion occurred, as a result of which the empty magma chamber collapsed and the Krakatau sank. Tremendous amounts of rock and lava were blown far into the stratosphere in this final spasm of the volcano. The eruption cloud rose 38,000 meters before collapsing, producing the worst pyroclastic current ever reported. What remained was a large hole, a caldera, and the Rakata stump. When the magma chamber collapsed, the cavity suddenly filled with water. This process - comparable to an implosion - is likely to have triggered the last and largest tidal wave of the catastrophe. The bang of this last explosion could still be heard on the island of Rodriguez, 4,700 kilometers away.
As if by a miracle, most of the ship's crews survived the giant waves, as the tsunamis only develop their force when they hit flat shore zones. There was no trace of the crew of the "Berouw", which was stranded three and a half kilometers inland in a creek bed. Even months after the sinking of the Krakatau, huge rafts of pumice stones were washed ashore on the coasts of East Africa. Some of them contained gruesome cargo.
In the devastated stretches of coast, the survivors fought for their livelihood. There was a lack of drinking water, food and medicine. Aid deliveries started very slowly. The Dutch colonial rulers were bitterly reproached. This climate was the breeding ground for Islamists who instigated uprisings. More and more Indonesians converted to Islam. The unrest that began after the Krakatau disaster did not culminate until 57 years later in the Indonesian War of Independence. Six weeks after the disaster, an expedition visited the remains of Krakatau for the first time. She found a completely lifeless wasteland. But only six months later, biologists discovered the first new life that repopulated the scorched earth of the Rakata. After a few more years, trees were already growing on the steep slopes and animals had returned to the island.

In 1927 Krakatau was reborn. After a series of violent eruptions, Anak Krakatau - "the child of Krakatau" - appeared in the middle of the caldera. The island was created exactly where the central cone of the Danan had previously risen. Shortly after the birth of the small island, the young island fell victim to the forces of the ocean again. The surf quickly carried away the loose sands and cinders. The cycle of birth and decline was repeated four more times until a stable island finally grew up in 1930. Since then, Anak Krakatau has been one of the most active volcanoes in the world. Here, too, life gained a foothold surprisingly quickly. The most recent series of eruptions to date occurred between October 2007 and June 2008. On the southwest flank, a new crater opened below the summit and produced a series of strombolian eruptions.

As of 2009

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