Mount Merapi, Gunung Merapi (literally Mountain of Fire in Indonesian/Javanese), is an active stratovolcano located on the border between Central Java and Yogyakarta, Indonesia. It is the most active volcano in Indonesia and has erupted regularly since 1548. It is very close to the city of Yogyakarta, and thousands of people live on the flanks of the volcano, with villages as high as 1700 m above sea level.
The name Merapi could be loosely translated as 'Mountain of Fire' from the Javanese combined words; Meru means "mountain" and api means "fire". Smoke can be seen emerging from the mountaintop at least 300 days a year, and several eruptions have caused fatalities. Hot gas from a large explosion killed 27 people on November 22 in 1994, mostly in the town of Muntilan, west of the volcano. Another large eruption occurred in 2006, shortly before the Yogyakarta earthquake. In light of the hazards that Merapi poses to populated areas, it has been designated as one of the Decade Volcanoes.
On 25 October 2010 the Indonesian government raised the alert for Mount Merapi to its highest level and warned villagers in threatened areas to move to safer ground. People living within a 20 km (12.5 mile) zone were told to evacuate. 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 a kilometre below the surface due to the seismic activity. On the afternoon of 25 October 2010 Mount Merapi erupted lava from its southern and southeastern slopes.
Geological History
Merapi is the youngest in a group of volcanoes in southern Java. It is situated at a subduction zone, where the Indo-Australian Plate is sliding beneath the Eurasian Plate. It is one of at least 129 active volcanoes in Indonesia, part of the Pacific Ring of Fire – a section of fault lines stretching from the Western Hemisphere through Japan and South East Asia. Stratigraphic analysis reveals that eruptions in the Merapi area began about 400,000 years ago, and from then until about 10,073 years ago, eruptions were typically effusive, and the outflowing lava emitted was basaltic. Since then, eruptions have become more explosive, with viscous andesitic lavas often generating lava domes. Dome collapse has often generated pyroclastic flows, and larger explosions, which have resulted in eruption columns, have also generated pyroclastic flows through column collapse.
Merapi in 1930There has been no late eruption. Typically, small eruptions occur every two to three years, and larger ones every 10–15 years or so. Notable eruptions, often causing many deaths, have occurred in 1006, 1786, 1822, 1872, and 1930—when thirteen villages were destroyed and 1400 people killed by pyroclastic flows.
A very large eruption in 1006 is claimed to have covered all of central Java with ash. The volcanic devastation is claimed to have led to the collapse of the Hindu Kingdom of Mataram, however there is insufficient evidence from that era for this to be substantiated.
2010 Eruption
Eruptive background
In late October 2010 the Center for Volcanology and Geological Hazard Mitigation, Geological Agency (CVGHM), (Indonesian language—Pusat Vulkanologi & Mitigasi Bencana Geologi, Badan 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).[13] Lava from Mount Merapi in Central Java began flowing down the Gendol River on 23–24 October signalling the likelihood of an imminent eruption.
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 a 1 kilometre (3,300 ft) below the surface due to the seismic activity
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 activity including lava ejection and hot ash clouds were reported to be increasing again.
By early on the morning of Saturday 30 October the volcano was erupting again. Sri Sumarti, head of the Merapi section at the Volcano Investigation and Technology Development Board (BPPTK), reported 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. The morning eruptions lasted for 22 minutes and heat clouds flowed into the Krasak and Boyong Rivers also rising 3.5 kilometres (2.2 mi) into the air, westward toward Magelang. Yogyakarta’s Adisucipto Airport was temporarily closed from 5AM. to 7AM. On 30 October, Subandrio, head of the Volcano Investigation and Technology Development Institution (BPPTK) suggested there would be further eruptions as lava continued to push its way up into the volcano's lava dome. The eruption caused a temporary panic on the ash covered streets of Sleman district in Yogyakarta early on the morning of 30 October. The district was however well outside the immediate disaster zone.
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 (3.1 mi) 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 vulcanology 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.[22] 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.” From 2 November several airlines including Garuda, AirAsia and Silkair international flights to both Yogyakarta and Solo were either suspended or re-routed due to the eruptive activity.
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 5:55AM on the 4 November was reported as being five times stronger that 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. At least one Hajj flight from Solo to Batam is known to have had engine trouble related to volanic ash.
Herry Bakti Gumay, Director General of air transportation, stated on 4 November that the warning released to all airlines operating flights into Yogyakarta would not withdraw it until conditions returned to normal.
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 was 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. On 5 November at 11:07(UTC) the Australian government Bureau of Meteorology (VAAC) issued an ongoing code red Aviation Volcanic Ash Advisory and reported satellite image (MTSAT-2) derived information indicating a volcanic ash plume to FL550 OBS extending 190 nautical miles to the west and southwest of the mountain.
Casualties
On 26 October at least 18 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 3:00PM 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 the Indonesian National Disaster Management Agency was reporting 122 deaths attributable to the Merapi eruptions. Soldiers joined rescue operations in Bronggang, 15 kilometers from the crater to assist in recovering bodies from the village. At least 78 bodies were removed from homes and streets blanketed by ash up to 30-centimeters deep. They had been killed when hot ash clouds from the crater had travelled down the mountain in pyroclastic flows at speeds of up to 100km per hour and engulfed their village. Many of the dead on Friday 5 November were children from Argomulyo village, 18 kilometers from the crater, according to emergency response officials and witnesses.
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.
Monitoring
Mount Merapi is the site of a very active volcano monitoring program. Seismic monitoring began in 1924, with some of the volcano monitoring stations lasting until the present. The Babadan (northwest location), Selo (in the saddle between Merbabu and Merapi), and Plawangan monitoring stations have been updated with equipment over the decades since establishment. During the 1950s and early 1960s some of the stations were starved of equipment and funds, but after the 1970s considerable improvement occurred with the supply of new equipment. Some of the pre-1930 observation posts were destroyed by the 1930 eruption, and newer posts were re-located. Similarly after the 1994 eruption, the Plawangan post and equipment were moved into Kaliurang as a response to the threat of danger to the volcanological personnel at the higher point.
The eruption of 1930 was found to have been preceded by a large earthquake swarm. The network of 8 seismographs currently around the volcano allow volcanologists to accurately pinpoint the hypocentres of tremors and quakes.
A zone in which no quakes originate is found about 1.5 km below the summit, and is thought to be the location of the magma reservoir which feeds the eruptions.
Other measurements taken on the volcano include magnetic measurements and tilt measurements. Small changes in the local magnetic field have been found to coincide with eruptions, and tilt measurements reveal the inflation of the volcano caused when the magma chambers beneath it is filling up.
Lahars (a type of mudflow of pyroclastic material and water) are an important hazard on the mountain, and are caused by rain remobilizing pyroclastic flow deposits. Lahars can be detected seismically, as they cause a high-frequency seismic signal. Observations have found that about 50 mm of rain per hour is the threshold above which lahars are often generated.
Culture
Merapi continues to hold particular significance for the Javanese beliefs: it is one of four places where officials from the royal palaces of Yogyakarta and Solo make annual offerings to placate the ancient Javanese spirits.
To keep the volcano quiet and to appease the spirits of the mountain, the Javanese regularly bring offerings on the anniversary of the sultan of Yogyakarta's coronation. For Yogyakarta Sultanate, Merapi holds significant cosmological symbolism, because it is forming a sacred north-south axis line between Merapi peak and Southern Ocean (Indian Ocean). The sacred axis is signified by Merapi peak in the north, the Tugu monument near Yogyakarta main train station, the axis runs along Malioboro street to Northern Alun-alun (square) across Keraton Yogyakarta (sultan palace), Southern Alun-alun, all the way to Bantul and finally reach Samas and Parangkusumo beach on the estuary of Opak river and Southern Ocean. This sacred axis connected the hyangs or spirits of mountain revered since ancient times—often identified as "Mbah Petruk" by Javanese people—The Sultan of Yogyakarta as the leader of the Javanese kingdom, and Nyi Roro Kidul as the queen of the Southern Ocean, the female ocean deity revered by Javanese people and also mythical consort of Javanese kings.
National park
In 2004 an area of 6,410 hectares around Mount Merapi was established as a national park. The decision of the Ministry of Forestry to declare the park has been subsequently challenged in court by The Indonesian Forum for Environment, on grounds of lack of consultation with local residents.[46] During the 2006 eruption of the volcano it was reported that many residents were reluctant to leave because they feared their residences would be confiscated for expanding the national park.
Museums
Merapi Museum Center, Kaliurang Street Kilometer 25.7
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