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Tricia Abrizenski 11.05.10 Natural Disasters 1750-91 Fall 2010.

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Presentation on theme: "Tricia Abrizenski 11.05.10 Natural Disasters 1750-91 Fall 2010."— Presentation transcript:

1 Tricia Abrizenski Natural Disasters Fall 2010

2 What Krakatoa was How Krakatoa was created The preliminary eruption investigation The devastation caused Why Krakatoa erupted so forcefully Krakatoa today In this presentation we will discuss: Its Location Events leading up to the eruption The result of the eruption The effects of the Krakatoa eruption Sound and pressure waves from the eruption Anak Krakatau in the future

3 What was Krakatoa? Krakatoa was a chain of three stratovolcano islands with five identified evolutionary periods. Over time it grew to become one giant island volcano with 3 peaks. It was located in the most volcanically active region on earth (Indonesia) south of Sumatra (approximately 25 miles from Ketimbang) and west of Java in the Sunda Strait. It is also one of the deadliest volcanoes in history. After remaining dormant for more than 200 years, it would erupt in a cataclysmic explosion during the summer of 1883 after months of geologic activity signifying the reawakening of the island. The pyroclastic flows and ensuing tsunamis that it produced would claim the lives of 36,417 people and injure thousands more in the region; it would become known as one of (if not the) most important eruptions in the fields of science and volcanology. Slide 23 – 1 Slide

4 It has been confirmed through the reading of sulfuric acid deposits contained within Antarctic ice core samples that Krakatoa erupted with paroxysmal force in 535AD. The entire island was wiped from the surface of the earth forming a large undersea caldera, thus ending the first evolutionary period of Krakatoa and beginning the second. During its 3 rd period Krakatoa would rebuild itself with a series of regular, violent, undersea eruptions forming three volcanic peaks. The volcanoes Rakata (798m), Danan (500m), and Perbuwaten also known as Perboewetan (130m) would grow together, from the original caldera of the ancestral Krakatau, to create the larger island of Krakatoa. Slide

5 Krakatoa was formed through the process of undersea subduction between the Indo-Australian plate and the Burmese continental plate. As one tectonic plate subducts under another, magma can find its way to the surface and form volcanoes. As the older, cooler oceanic plate was pushed below the warmer, more buoyant continental plate the cooler rock was reabsorbed into the core of the planet. As that rock melted it found its way to the surface through cracks and fissures in the earths crust erupting violently to create Krakatoa. Slide 23 – 3 Slide

6 In Ketimbang (23miles NW) and Batavia (83 miles E of Krakatoa) there were precursors to the events that would take place only a short time later. Small indiscernible tremors were taking place below the earths crust at that time. Batavia was the capital of the Dutch East Indies; it was also home to a meteorological observatory. The chief Dr. and Director there was Dr. Vanderstock. He was responsible for monitoring the seismic activity in the region and it is widely believed that through his initial observations in the early stages of the eruption of Krakatoa, he helped modern volcanologists understand why the volcano erupted with such paroxysmal force. There was also a young geologist stationed at the observatory by the name of Sherman. Slide

7 On May 9 th in Ketimbang, four months before the eruption that would destroy Krakatoa, there was a great tremor felt throughout the region. At the time, it was unknown as to where it had come from or what the cause was but is now believed to be the first discernable sign that intensely pressurized magma had broken through a fault underneath the volcano and was making its way to the surface of the earths crust. Eleven days later on May 20 th, fisherman hunting off of the coast of Krakatoa and foraging in the jungle for timber to build boats witnessed the first eruption. Perbuwaten, the smallest volcano on the island, had erupted throwing ash and pumice miles from its peak in a vulcanian eruption. The eruption was also witnessed by Captain Johan Lindeman of the Governor General Loudon. The Governor General Loudon was a Dutch steamship that often passed through the Sunda Strait and within close range of Krakatoa. Slide

8 Only a fraction of a moment after the eruption the shockwaves reached Ketimbang and minutes after that, the shockwave was recorded within Dr. Vanderstocks observatory in Batavia. Dr. Vanderstock read the recording, much like we would a readout from a seismometer today, and came to the conclusion that the shockwave had come not through the ground, but through the air from some 100 miles away. It was Sherman who deduced that the shockwave must have then come from a volcano. Dr. Vanderstock was notified of the eruption definitively by the controller of Ketimbang, Willem Beijerinck. Vanderstock then notified the Governor General who subsequently ordered an investigatory expedition to the island. Slide 23 – 6,7

9 The expedition was led by Sherman and began on May 27 th Upon their arrival they found that the entire forest on the Perbuwaten side of the island had been flattened and charred by what we now know are pyroclastic flows. Pyroclastic flows are superheated fluid masses of rock, gas, and ash that move in a rapid gravitational manner across land and water. The expedition yielded volcanic and geologic samples of great importance such as water, ash, acids, and large pumices that had been strewn across the beaches and riddled with small holes formed from the gaseous content of the lava. Shermans report to the Governor General offered information such as there were no obstacles to hinder their investigation other than loose ash and foul smelling smoke that caused them to gag. Slide

10 Over the preceding months the island had returned to a relatively calm state; then on August 26 th at 1:06 PM, the Island volcano of Krakatoa began to erupt in true plinian fashion. All three craters on the island began to erupt and with the ejection of magma, pumice, and ash, day became night and the clouds blocked out the sun so that you may not see your hand in front of your face. Gas, ash, and pumice were ejected so high into the atmosphere that it joined with the jet stream and was carried around the globe for years to come affecting everything from the global climate and weather patterns to the colorations of the sunrise and sunset. It is even thought that the famous Scream painting was inspired by the colors seen in the sky half way around the world soon after the eruption. Slide

11 The following morning, at 5:30 AM, began another series of eruptions on Krakatoa that inevitably ripped the island volcano apart with paroxysmal force, completely destroying it and leaving only remnants of Rakata behind after collapsing back into the ocean. The actual force of the explosion is somewhat debatable; some reports say that it was equivalent to 200 megatons of TNT, some report that it was equal to 1,000 atomic bombs, and others yet say that it was a force near 21,000 megatons of nuclear explosion. The one thing that is not debatable is the level of destruction left in the wake of the volcanic eruptions and pyroclastic flows that burned thousands, were approximately 2,800 ft. high in their origination and stretched more than 25 miles from the island of Krakatoa to the mainland in Ketimbang as well as the following tsunamis that claimed more than 36,000 lives. The eruption scattered debris across the Indian Ocean as far away as Madagascar. It was loud enough to be heard over more than 8% of the earths surface And the air borne shock waves reverberated around the entire planet 7 times Slide 23 – 9, 10, 11

12 Pyroclastic Flows As the flow cascades down the mountainside and comes into contact with the water, the heavier debris moves outward and sinks; however the forward momentum of the flow causes a large wave to form. In addition, the superheated ash on the surface comes into contact with the water and creates a cloud of steam for the lighter debris to flow on top of enabling it to move greater distances and at an even more rapid pace than it would have on land. Some investigation as to the interaction of pyroclastic flows and water can be viewed in this excerpt from the Discovery Channel documentary regarding Krakatoa. Click for 3:17 Video In this video we can see one of the possible results of a pyroclastic flow and its interaction with the surrounding water. Slide 23 – 12 Slide

13 The tsunamis that followed the eruption were reported to be more than 40 meters high. Slide

14 As the tsunami continued to move inland, it lost speed but gained in height. As it hit the Sumatran coastline it was then funneled up Lampong Bay destroying everything in its path. It carried the Dutch steamer Berouw 1.8 miles inland of Telok Betong before finally depositing it across a river bed. Slide 23 – 13 Slide

15 Slide 25 – 7S

16 The Destruction of Fourth Point Lighthouse The tsunami that hit the coastline at Java even tore up large chunks of sea bed and coral reported to have weighed some 600 tons. Same coral responsible for the destruction of Fourth Point lighthouse today 600 Ton coral that destroyed Fourth Point Lighthouse One of these chunks of coral was responsible for the destruction of the Fourth Point Lighthouse. The new lighthouse that was built is 40 meters in height and is about the same height as the tallest tsunami wave that hit the coastline there. An estimated 19.6 thousand Javanese died in the tsunami Slide 23 – 13 Slide

17 But WHY? WHY did Krakatoa erupt so forcefully? That question has puzzled scientists for decades. Numerous scientists, both volcanologists as well as geologists, have made repeat visits to Rakata (all that remains of Krakatoa) to find answers to this very question. It seems as though there are a number of factors that come to play in the violent eruption of Krakatoa. Krakatoa is situated atop a subduction plate within the Ring of Fire. Its construction was that of a stratovolcano whos chamber contained thick, viscous, silica rich, andesitic magma. Krakatoa was not comprised of solid rock but made up of fairly loose debris formed over time from layers of pumice and pyroclastic activity topped with lava flows of a high viscosity. The alternating layers would make it easier for the volcano to crumble and collapse after an exceptionally explosive eruption. The high viscosity lava that formed the cap of the volcano was what held in the pressure over hundreds of years. Slide

18 After the initial eruption the magma chamber of the volcano was partially emptied and the thick viscous magma formed over the cap again allowing for the lull in activity for a few months. When the magma chamber emptied the fissure that had opened previously underneath the volcano allowed for superheated magma to flow into the volcano and mix with the cooler magma in the chamber, as is evident from the examination of larger pumices on Rakata. The cooler magma that had been sitting in the chamber for an extended period is lighter in color than the hotter magma that entered the chamber later after the initial eruption. When examining the pumices it has a marbled effect of lighter and darker (or cooler and hotter) magma types. Slide 23 – 15 Slide

19 May 9 th violent tremors are felt in the region. It is believed that a fissure opened under the volcano at this time. May 20 th Perbuwaten erupts as a result of the open fissure and partially empties the magma chamber. A new plug forms over the volcano due to the viscous nature of the lava allowing for a lull in activity and time for the magma chamber refill. Superheated magma enters the chamber mixing with cooler magma already in the chamber and melting surrounding rock releasing more gasses and building pressure inside of the volcano. This eruption process has been likened to shaking up a bottle of champagne until the cork blows off. The superheated magma directly caused the pressure inside of the volcano to rise until the structural integrity of the volcano failed and erupted with cataclysmic force blowing the island apart. The island then collapsed into the magma chamber creating an undersea caldera approximately 3X5 miles across.

20 Sound & Pressure Waves The explosion of Krakatoa at 10:02 AM August 27 th 1883 has been renowned as the loudest sound ever heard by modern humans. It was heard over more than 1/12 th of the earths surface; 2,000 miles away in Perth Australia, as well as 3,000 miles away at Rodriguez Island in the Indian Ocean. It is the longest distance traveled by any airborne sound in recorded history. It also produces pressure waves that reverberated around the globe seven times and were recorded over a period of 12 days. The Fourth and final explosion at 10:45 AM tore Krakatoa apart and the volcanic island collapsed back into the sea. Map of atmospheric pressure waves from the Krakatoa eruption. Slide 23 – 16 Slide

21 The news of the eruption of Krakatoa and subsequent disappearance was transmitted around the globe in a matter of hours through the use of fairly newly installed transoceanic telegraph cables. People around the world would soon (and for years thereafter) take note of the effects of the 11 cubic miles of ash and debris that had joined with the atmosphere. Evidence that the explosion affected the atmosphere for 4-5 years afterwards is documented in detail at The Royal Society in London Sunset Oil Pastels drawn after the eruption. Slide 23 – 17 Slide 25 – 9, 10

22 Now, nearly 130 years later, Krakatoa is in its 5 th evolutionary stage. In June of 1927 a new volcano called Anak-Krakatau was born from the undersea caldera that remains from earlier explosions. It is regularly active, as well as continually and rapidly growing at a rate of 12+ feet per year. It first developed through a number of submarine eruptions and now stands at a height of more than 1,033 feet. It covers 1.25 square miles and in less than 10 years ejected more than 50 million tons of material. Slide 23 – 18 Slide

23 The investigation of Krakatoa and Anak-Krakatau continues today and also continues to influence volcanism as the first ever widely studied eruption in history. Anak-Krakatau will continue to grow and it WILL erupt again… whether or not it will be as destructive a force as its parent, still remains to be seen but is almost a certainty. Slide

24 1.Carter, S. (Producer), Hall, J. (Writer), & Hall, J. (Director). (2005). Krakatoa [Motion Picture]. USA: PBS Carter, S., Marsh, S. (Producers), & Strange, R. (Director). (2009). How the Earth was Made: Krakatoa [Motion Picture]. USA / UK: A&E Television Networks 2.How the Earth was made: Krakatoa, History Channel Documentary, Global Volcanism Program of the Smithsonian Institute 3.Abbott, P. L. (2009). Natural Disasters (7th ed.). New York, NY, USA: McGraw Hill. Krakatoa Documentary, PBS, Krakatau. Retrieved 10 27, 2010, from Smithsonian Institution - Global Volcanism Program: Worldwide Holocene Volcano and Eruption Information: 4.Krakatoa Documentary, PBS, How the Earth was made: Krakatoa, History Channel Documentary, Krakatoa Documentary, PBS, How the Earth was made: Krakatoa, History Channel Documentary, Abbott, Natural Disasters, 195, 199, 203. Krakatoa Documentary, PBS, How the Earth was made: Krakatoa, History Channel Documentary, Krakatoa Documentary, PBS, How the Earth was made: Krakatoa, History Channel Documentary, Abbott, Natural Disasters, 203. Krakatoa Documentary, PBS, How the Earth was made: Krakatoa, History Channel Documentary, How the Earth was made: Krakatoa, History Channel Documentary, Krakatoa Documentary, PBS, Abbott, Natural Disasters, 234. How the Earth was made: Krakatoa, History Channel Documentary, Beijerinck, J. (2010, 10 25). Discovery Channel Krakatoa Survivor Diary Johanna Beyerinck. Retrieved 10 25, 2010, from Discovery Channel: 12.Discovery Channel (with BBC) Documentary Krakatoa: Volcano of Destruction Krakatoa Documentary, PBS, How the Earth was made: Krakatoa, History Channel Documentary, Abbott, Natural Disasters, Krakatoa Documentary, PBS, Krakatoa: Volcano of Destruction, Discovery (BBC), Krakatoa Documentary, PBS, How the Earth was made: Krakatoa, History Channel Documentary, Robert McNamara, Krakatoa Volcano Eruption Was a Worldwide Weather and Media Event (Article). Krakatoa Documentary, PBS, How the Earth was made: Krakatoa, History Channel Documentary, 2009

25 Abbott, P. L. (2009). Natural Disasters (7th ed.). New York, NY, USA: McGraw Hill. Beijerinck, J. (2010, 10 25). Discovery Channel :: Krakatoa :: Survivor Diary :: Johanna Beyerinck. Retrieved 10 25, 2010, from Discovery Channel: Carter, S. (Producer), Hall, J. (Writer), & Hall, J. (Director). (2005). Krakatoa [Motion Picture]. USA: PBS. Evans, G., Mosley, M. J. (Producers), Heber-Percy, C., Olmert, M. (Writers), & Miller, S. (Director). (2006). Krakatoa: Volcano of Destruction [Motion Picture]. UK: Discovery Channel. Carter, S., Marsh, S. (Producers), & Strange, R. (Director). (2009). How the Earth was Made: Krakatoa [Motion Picture]. USA / UK: A&E Television Networks. Unk. (2010, 10 27). Krakatau. Retrieved 10 27, 2010, from Smithsonian Institution - Global Volcanism Program: Worldwide Holocene Volcano and Eruption Information:

26 Evans, G., Mosley, M. J. (Producers), Heber-Percy, C., Olmert, M. (Writers), & Miller, S. (Director). (2006). Krakatoa: Volcano of Destruction [Motion Picture]. UK: Discovery Channel 5. AN_Krakatoa_Map.jpg AN_Krakatoa_Map.jpg Evans, G., Mosley, M. J. (Producers), Heber-Percy, C., Olmert, M. (Writers), & Miller, S. (Director). (2006). Krakatoa: Volcano of Destruction [Motion Picture]. UK: Discovery Channel


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