http://aroundjogja.blogspot.com/2010/11/merapi-volcano-2010-eruption.htmlMerapi volcano is one of the world's most active and dangerous volcanoes. It contains an active lava dome which regularly produces pyroclastic flows. Eruptions occur at intervals of 1-5 years and are of low gas pressure. Merapi is one of the most active volcanoes in Indonesia and has produced more pyroclastic flows than any other volcano in the world. It has been active for 10,000 years.
Most eruptions of Merapi involve a collapse of the lava dome creating pyroclastic flows which travel 6 to 7 km from the summit. Some 'awan panas' have traveled as far as 13 km from the summit, such as the deposit generated during the 1969 eruption. Velocity of pyroclastic flows can reach up to 110 km/hour. A slow up flow of andesitic magma leads to an extrusion of viscous magma, which accumulate and construct a dome in the crater.
Violent Eruptions at Merapi volcano
There is evidence that the current low level of activity may be interrupted by larger explosive eruptions. Eruptions of Merapi volcano during the 7–19th centuries A.D. were more violent than the past hundred years, and produced explosion pyroclastic flows. Widespread pyroclastic flows and surges traveled up to 25 km down the flanks of Merapi.
2010 Eruption
Merapi volcano began erupting on 26th October 2010. The eruption was the was the largest at the volcano in 100 years. Ash emissions reached an altitude of 40,000 ft, and 370,000 people were evacuated from a 20 km radius danger zone. Over 190 people were killed by pyroclastic flows and ashfall.
Eruptive background
In late October 2010 the Center for Volcanology and Geological Hazard Mitigation, Geological Agency (CVGHM), (Indonesian language—Pusat Vulkanologi & Mitigasi Bencana Geologi - PVMBG), reported that a pattern of increasing seismicity from Merapi had begun to emerge in early September.
Observers at Babadan 7 kilometres (4.3 mi) west and Kaliurang 8 kilometres (5.0 mi) south of the mountain reported hearing an avalanche on 12 September 2010.
On 13 September 2010 white plumes were observed rising 800 metres (2,600 ft) above the crater. Lava dome inflation, detected since March, increased from background levels of 0.1 millimetres (0.0039 in) to 0.3 millimetres (0.012 in) per day to a rate of 11 millimetres (0.43 in) per day on 16 September.
On 19 September 2010 earthquakes continued to be numerous, and the next day CVGHM raised the Alert Level to 2 (on a scale of 1–4). Lava from Mount Merapi in Central Javaeruption began flowing down the Gendol River on 23–24 October signalling the likelihood of an imminent.
On 25 October 2010 the Indonesian government raised the alert for Mount Merapi to its highest level (4) and warned villagers in threatened areas to move to safer ground. People living within a 10 kilometres (6.2 mi) zone were told to evacuate. The evacuation orders affected at least 19,000 people; however, the number that complied at the time remained unclear to authorities. Officials said about 500 volcanic earthquakes had been recorded on the mountain over the weekend of 23–24 October, and that the magma had risen to about 1 kilometre (3,300 ft) below the surface due to the seismic activity
After a period of multiple eruptions considered to exceed the intensity and duration of those in 1872 on 10 November 2010 the intensity and frequency of eruptions was noticed to subside. By this time 153 people had been reported to have been killed and 320,000 were displaced. Later the eruptive activities again increased requiring a continuation of the Level 4 alert and continued provision of exclusion zones around the volcano. By 18 November the death toll had increased to 275.
Eruptive events
On Monday afternoon 25 October 2010 Merapi erupted three times, spewing lava down its southern and southeastern slopes. Three major eruptions were recorded at 14:04, 14:24 and 15:15. On 25 October 222 volcanic seismic events and 454 avalanche seismic events were recorded by Center for Volcanology and Geological Hazard Mitigation monitoring staff at Merapi.
The eruptions on 26 October started at 17:02. By 18:54 pyroclastic activity had begun to subside following 12 eruption associated events being recorded by CVGHM monitors. In the 24 hours of 26 October 232 volcanic seismic events, 269 avalanche seismic events, 4 lava flow seismic events and 6 heat clouds were recorded by Center for Volcanology and Geological Hazard Mitigation monitoring staff at Merapi. The eruptive events of 26 October were classified as an explosive event with volcanic bursts of ejected material, visible flame and pyroclastic hot air flows. A column of smoke rose from the top to a vertical distance of 1.5 kilometres (0.93 mi) from the summit of the Mount Merapi.
On Friday 29 October eruptive activity included lava ejection with hot ash clouds reported to be flowing 3 kilometres (1.9 mi) down the slopes of the mountain and lasting four to nine minutes. Ash falls reached as far as the Central Java town of Magelang. Scientists monitoring the volcano including Surono, chief of the Volcanology and Geological Disaster Mitigation Center (PVMBG) were optimistic that the volcanic activity should decrease following the release of lava. Safari Dwiyono, a scientist monitoring Mt. Merapi for 15 years, said the volcanic activity appeared to be easing pressure behind a lava dome that had formed in the crater.
By early on the morning of Saturday 30 October the volcano was erupting again. The eruptions were louder and stronger than the eruptions of the 26 October. Those earlier eruptions on the previous Tuesday killed 34 people. Ash from the eruptions on 30 October fell more than 30 kilometres (19 mi) away and now included ash falls upon the city of Yogyakarta. Soldiers and police posted nearest the volcano were seen fleeing along with hundreds of residents quickly clogging roads with cars and motorcycles. Black soot fell across a vast area. The morning eruptions lasted for 22 minutes and heat clouds flowed into the Krasak and Boyong Rivers also rising 3.5 kilometres (11,000 ft) into the air, westward toward Magelang. Yogyakarta’s Adisucipto Airport was temporarily closed from 05:00 to 07:00. On 30 October, Subandrio, head of the BPPTK, suggested there would be further eruptions as lava continued to push its way up into the volcano's lava dome.
On 3 November heat clouds travelled up to 10 kilometres (6.2 mi) away from the eruption forcing the government to evacuate people from within the refugee camps set up to accommodate those already dislocated by the volcano. Eruptions on the afternoon of Wednesday 3 November followed a morning eruption that sent hot gas clouds down the volcano's slopes. The volcano spewed clouds of ash and gas 5 kilometres (16,000 ft) into the sky for more than an hour on 3 November. The eruptions of that day were reported as being the largest since the eruptions commenced.
Surono, head of Indonesia's volcanology agency announced on 3 November that he was moving the shelters to 15 kilometres (9.3 mi) away from the summit. Speaking on Indonesia's Metro TV network he said, "this is the first time that the eruption has continued for more than an hour, so I decided to move the shelters to 15 km away from the summit". The shelters had previously been set up 10 kilometres (6.2 mi) away. Surono added that the energy from the eruption on 3 November was three times greater than that of the first eruption in the previous week. Bambang Ervan, a spokesman from the Transportation Ministry, said an official warning had been issued to all airlines to “use alternative routes for safety reasons due to the volcanic ash.”
Heavy rain during the night of 3–4 November triggered lahars with mixtures of water and rock debris cascading down the Kuning, Gendol, Woro, Boyong, Krasak and Opak rivers on the slopes of the volcano. A bridge was destroyed and riverbanks damaged. The eruption at 05:55 on the morning of 4 November was reported as being five times stronger than the initial eruption on 26 October 2010. On 4 November Merapi had been erupting for 24 hours without stopping. Heat clouds of 600 to 800 degrees Celsius spread as far as 11.5 kilometers from the crater reaching toward the edge of the then 15 kilometres (9.3 mi) exclusion zone, and lava flowed into the mountain’s rivers.
Merapi erupted early on Friday 5 November 2010. Volcanic ash fell at Cangkringan village and its surroundings 10 kilometres (6.2 mi). Due to continuous large eruptions, the government extended the safety zone to 20 kilometres (12 mi) radius and Yogyakarta's airport was closed again for 3 hours in the morning. Volcanologists reported the eruptions of Friday 5 November to be the biggest since the 1870s and officials announced by loudspeaker that the mountain's danger zone had been expanded to 20 kilometers from the crater. Bronggang, a village 15 kilometers from the crater, had streets blanketed by ash up to 30-centimeters deep. By 5 November more than 100,000 people had been evacuated and the scientists monitoring the events were withdrawn from their posts to a safer distance.
By Saturday, 6 November the eruptions and ash falls in the surrounding area of Central Java had led to the increase in prices of many vegetables, such as potatoes and water spinach . Schools were reported closed up to 120 kilometres (75 mi) west of Yogyakarta. The Center for Volcanology and Geological Hazard Mitigation observation outposts reported high intensity ash falls on the slopes of Mt Merapi. At 23:51 a flash of smoke, hot air winds and flames as high as 3 kilometres (1.9 mi) occurred to the west, north and to the east. The Center for Volcanology and Geological Hazard Mitigation observation outposts reported high intensity ash falls on the slopes of Mt Merapi.
On Sunday, 7 November at 03:02 hot ash clouds flowed in the direction Gendol and Woro rivers. Volcanic earthquake and hot ash cloud events were reported to have increased from the previous day.
The eruptive events continued into Monday and on Tuesday, 9 November BNPB announced that they considered the eruptive activities of 2010 to have exceeded the activities of the mountains eruption in 1872. Based on historical records, the eruption of Merapi in 1872 was recorded for 120 hours, while the eruption of 2010 had already presented five days of relentless activity since Thursday 4 November and up until the 8 November had erupted for more than 120 hours or more without pause. Subandriyo, head of the Volcano Investigation and Technology Development Institution (Balai Penyelidikan dan Pengembangan Teknologi Kegunungapian/BPPTK) in Yogyakarta revealed that hot ash clouds during the eruptions of 138 years ago had a maximum reach of only 11–12 km, whilst the current eruptions were reaching 14.5 km. The Center for Volcanology and Geological Hazard Mitigation (PVMBG) Geological Agency, head officer, Dr Surono announced on 9 November that during the hours of 06:00 to 12:00 eruptive events were continuing with sequential volcanic earthquakes, tremors, avalanches fast moving clouds were still travelling as far as 4 km toward the southwest. Yogyakarta residents and evacuees were reminded that the threat of pyroclastic as clouds and lahar floods remained. The people of Yogyakarta were also reminded to observe the instructions to remain outside a radius of 20 km from the peak of Merapi.
On the night of 9 November there was a burst of ash reaching up to 1.8 kilometres (1.1 mi) vertically,
On 10 November 2010 the eruptive intensity was noticed to subside, however the volcano's activity remained high and it was still emiting heat clouds. The exclusion zone remained at 20 kilometres (12 mi)
Observations on 11 November by CVGHM (PVMPG) indicated the eruptive activities continued but at a level of decreased intensity. 17 Avalanches were recorded, 1 hot ash eruption and 1 volcanic earthquake. The volcano remained a level 4 alert but with a recommendation of "Caution" level being adopted with refugees to remain at a distance of greater than 20 kilometres (12 mi).
Reports by CVGHM (PVMPG) of eruptive activity including hot air clouds, smoke columns, avalanches and volcanic earthquakes continued throughout 16, 17 and 18 November. White and grey smoke was reported emerging from Merapi with smoke columns rising to 1,500 metres (4,900 ft). Smoke emissions continued to drift south and southwest of the mountain. Based on monitoring and assessment by CVGHM (PVMPG) the activity Mount Merapi was still considered to be remain at a high level on 18 November. The activity status of the volcano remained at Caution level (Level 4). The threat of immediate danger of eruption continued to be attributed to hot air and ash clouds (awanpanas) with indirect threats attributed to lava ejections.
Casualties
On 26 October at least 113 people, including one 2-month old baby, were found dead due to burns and respiratory failure caused by hot ashes from the eruption. Thousands were evacuated within a radius of 10 kilometres (6.2 mi) around the slopes of the volcano.
By Wednesday 27 October the death toll had risen to at least 25. The death toll included an elder, Mbah Maridjan (grandfather Marijan), known as the volcano's spiritual guardian who was found dead at his home approximately 4 kilometres (2.5 mi) from the peak. The Yogyakarta Palace subsequently confirmed his death. The 10 kilometres (6.2 mi) exclusion zone remained in place at the volcano with evacuation and ongoing search and rescue activities continuing at the site in an attempt to locate further victims of the previous days eruptions.
Later reports on the 27 October revised the toll upward to 30 persons recorded at Yogyakarta's Dr. Sardjito Hospital with 17 hospitalized, mostly with burns, respiratory problems and other injuries. Earlier on 27 October two of the 28 bodies at the hospital had been identified. Yuniawan Nugroho, an editor with the vivanews.com news portal, was reported to have been killed while conducting reportage on the night of Tuesday 26 October, the other was later identified as Tutur Priyanto Indonesian, a 36 year man working for the Red Cross as a volunteer on the mountain. Tutur Priyanto had been retrieving and escorting residents from the slopes of the mountain. After making many trips he returned for a further ascent at 15:00 to assist others to come off the mountain and died during one of the subsequent eruptive events. As of 1 November 2010, the death toll from Mount Merapi's blasts had climbed to 38. As of 5 November 2010, the death toll had climbed over 120.
By 5 November at 15:00 the Indonesian National Disaster Management Agency was reporting 122 deaths attributable to the Merapi eruptions, primarily from the area of residents from Sleman Daerah Istimewa Yogyakarta with an additional 151 injured people admitted to four Yogyakarta hospitals. Soldiers joined rescue operations in Bronggang to assist in recovering bodies from the village. At least 78 bodies were removed. They were killed when hot ash clouds from the crater had travelled down the mountain in pyroclastic flows at speeds of up to 100 kilometres per hour (62 mph) and engulfed their village. Many of the dead on Friday 5 November were children from Argomulyo village, 18 kilometres (11 mi) from the crater, according to emergency response officials and witnesses.
On the morning of 6 November BNPB provided a victim report. At that time there were 198,488 refugees, 218 people were injured, and 114 people had been recorded as having died. All the victims came from the districts of Sleman, Magelang, Klaten and Boyolaliin.
On Saturday, 7 November President Yudhoyono opened a limited cabinet meeting at the Presidential Palace, the Great House of Yogyakarta, to address the emergency response to the eruptions of Mount Merapi. At the meeting he reaffirmed his support of the Badan Koordinasi Nasional Penanganan Bencana-(Indonesian Disaster Management Office) and their administration and control of the disaster response. At 03:02 hot ash clouds flowed in the direction of the Gendol and Woro rivers. Volcanic earthquake and hot ash cloud events were reported to have increased from the previous day. Police stationed on the slopes complained that they were having considerable difficulties stopping people entering the exclusion zone and putting their lives at risk on the mountains slopes.
The JakartaGlobe reported on 8 November that that at least 135 people had died on Merapi's slopes over the previous two weeks, and that authorities were still struggling on Sunday to help those injured from Friday’s massive eruption. The bodies of four members of the Indonesian Disaster Response Team were recovered from the slopes of Mount Merapi on Monday, 8 November. However rescue officials had to retreat as eruptive activity made their further presence on the slopes too dangerous. State news agency Antara reported that a total of six bodies were recovered from the village of Glagaharjo in Sleman, Yogyakarta. The bodies of another two members of the response team, known as Tagana, are yet to be found or recovered. They have been missing since Thursday and are presumed dead.
The death toll was reported to be over 153 by 9 November with at least 320,000 people reported to have been evacuated to emergency shelters. One hospital recorded 12 more bodies brought its morgue on 9 November, including seven pulled from a destroyed village. Another five people who were being treated for burns died.
The National Disaster Management Agency announced on 11 November that the death toll since the first eruption on October 26 had climbed to 194, three quarters of those from searing heat blasts during the biggest eruptions and included deaths from respiratory problems, heart attacks and other illnesses related to the eruptions.
The number of people killed by the ongoing eruptions had risen to 275 by 18 November. The National Disaster Management Agency announced the death toll had climbed after more than a dozen victims succumbed to their injuries, the majority of those being from severe burns. Most of the 275 people were reported as being killed by searing gas clouds and from respiratory complications, burns and other illnesses related to the eruptions. Some victims died in road and other accidents during the panicked exodus from the mountain.
Lava Dome deformation
During the 4th week of October 2010 deformation measurements were performed by Electric Distance Measurement (EDM), utilising reflectors mounted around the summit of Mount Merapi. The measurement results indicated a rapidly increasing rate of growth of the lava dome in the build up to the eruptive events of 25–26 October 2010.
At the end of September 2010, the peak inflation rate of the lava dome at Mount Merapi was measured by EDM at an average growth rate of 6 millimetres (0.24 in). The subsequent rate of inflation up until October 21, 2010 reached 105 millimetres (4.1 in) per day. The inflation rate then increased very sharply, reaching 420 millimetres (17 in) per day by 24 October 2010. By the 25 October the average grow rate, measured from 6 EDM points over 24–25 October had risen to 500 millimetres (20 in) per day.
The information gathered at the site indicated that the distension of the mountain’s slopes was much more rapid this during the current event than that observed during the 2006 event.
On 26 October the head of the Indonesian Center for Volcanology and Geological Hazard Mitigation, Surono, repeated his earlier statements that the greatest concern was the pressure building behind a massive lava dome that has formed near the tip of the crater. "The energy is building up. ... We hope it will release slowly," he said. "Otherwise we're looking at a potentially huge eruption, bigger than anything we've seen in years". Surono also said that said the distension of the mountain’s slopes was much more rapid this time around, indicating a higher-pressure build-up of gas and hence a much more explosive eruption and speculated that Merapi may erupt explosively, as it did in 1930, and not just eject gas as in 2006 eruptions.
By 5 November following a week of ongoing explosive eruptions experts monitoring Merapi were reported as being "baffled" as despite earlier predictions that the eruptions following the initial blast in the prior week would ease pressure building up behind a magma dome instead the eruptions intensified. An estimated 50 million cubic meters of volcanic material had been released by 5 November, "it was the biggest in at least a century", said Gede Swantika, a state volcanologist, commenting on the eruptions of 5 November as plumes of smoke rose up more than 10,000 meters.
Dr Surono, head of the Volcanology and Geological Disaster Management Agency CVGHM (PVMBG) reported on 17 November that Merapi was still spewing ash and rock. “Most of the initial eruptions threw the ash south toward Sleman in Yogyakarta, but now it’s blowing west toward Magelang in Central Java,” Surono said. The later eruptions had not been as powerful because of the formation of three new lava vents in addition to the main one in the crater. This helped lessen the intensity of the eruptions. “If you look at the mountain’s peak at night, you’ll notice three small glowing points,” Surono said. “That’s actually a good sign because it means the volcano is releasing all its pent-up energy more quickly.”
Volcanic ash plume
The eruptions and subsequent volcanic ash plumes caused disruption to aviation movements across central and western Java in early November. Some flights to and from Bandung, Jakarta and Solo were effected and some international and domestic airlines suspended operations into and from those cities. Yogyakarta's Adisucipto International Airport was closed to flight operations on many occasions in early November due to limited visibility and ash falls upon the runway, taxiway and terminal aprons. Adisucipto International Airport is the third busiest airport on the island of Java. An Airbus A300-300 flight operated for Garuda Airlines as a Hajj Solo to Jeddah (Saudi Arabia) was reported to have suffered from ash related engine damage on 28 October. It was however later reported to have suffered from blade tip rubbing and was not apparently damaged by volcanic ash ingestion. pilgrimage from.
On Thursday 11 November, ash continued to spread over western Java and was falling just short of Jakarta according to the Volcanic Ash Advisory Center in Darwin, Australia. Flight activity at Jakarta's airport was normal and Yogyakarta's airport was closed until Monday 15 November. On the morning of 11 November the volcano was ejecting ash 1,000 metres (3,300 ft) into the air. High level clouds were observed over the Indian ocean and were thought to be volcanic ash bearing. A code red aviation alert was continued and at 16:41 a volcanic ash plume was seem to be extending to 25,000 feet (7,600 m) -FL250 extending to 150 nautical miles 240 kilometres (2.4×1011 ml) to the west. It had been observed earlier that day travelling 150 nautical miles 240 kilometres (2.4×1011 ml) to the north west as it had the day prior. The volcano was observed on 4–8 November by the Ozone Monitoring Instrument (OMI) on NASA’s Aura spacecraft and imagery indicated that a sulfur dioxide plume had been released into the upper troposphere. Besides elevating the risk of acid rain, the ions can also react to form particles that reflect sunlight. On November 9, 2010, the Volcanic Ash Advisory Centre in Darwin, Australia, also reported a sulfur dioxide cloud over the Indian Ocean between 12,000 and 15,000 meters (40,000 and 50,000 feet), in the upper troposphere.
On 19 November the Aviation Ash Advisory based upon information derived from MSTAT imagery and issued by VAAC, Darwin notified of and ash plume observed at a height of (15,000 feet (4,600 m) - F150), extending 40 nautical miles (75 kilometres (47 mi)) to the west of the mountain.
Souces : en.wikipedia.org | volcanolive.com
