Mount Merapi

Mount Merapi, Gunung Merapi (literally Fire Mountain 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 located approximately 28 kilometres (17 mi) north of Yogyakarta city, and thousands of people live on the flanks of the volcano, with villages as high as 1,700 metres (5,600 ft) above sea level.

The name Merapi could be loosely translated as 'Mountain of Fire'. The etymology of the name came from Meru-Api; from the Javanese combined words; Meru means "mountain" refer to mythical mountain of Gods in Hinduism, 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.[3] 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 1 kilometre (3,300 ft) below the surface due to the seismic activity.[4] On the afternoon of 25 October 2010 Mount Merapi erupted lava from its southern and southeastern slopes.

Geological history
Merapi before 2007 eruption.

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.[6] Stratigraphic analysis reveals that eruptions in the Merapi area began about 400,000 years ago, and from then until about 10,000 years ago, eruptions were typically effusive, and the out flowing 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 1930

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.
[edit] 2006 eruption
Pyroclastic flows (2006)

In April 2006, increased seismicity at more regular intervals and a detected bulge in the volcano's cone indicated that fresh eruptions were imminent. Authorities put the volcano's neighboring villages on high alert and local residents prepared for a likely evacuation. On April 19 smoke from the crater reached a height of 400 metres (1,300 ft), compared to 75 metres (246 ft) the previous day. On April 23, after nine surface tremors and some 156 multifaced quakes signalled movements of magma, some 600 elderly and infant residents of the slopes were evacuated.[7]

By early May, active lava flows had begun. On May 11, with lava flow beginning to be constant, some 17,000 people were ordered to be evacuated from the area[8] and on May 13, Indonesian authorities raised the alert status to the highest level, ordering the immediate evacuation of all residents on the mountain.[9] Many villagers defied the dangers posed by the volcano and returned to their villages, fearing that their livestock and crops would be vulnerable to theft.[6] Activity calmed by the middle of May.[10]

On May 27, a 6.3 magnitude earthquake struck roughly 50 km (30 miles) southwest of Merapi, killing at least 5,000 and leaving at least 200,000 people homeless in the Yogyakarta region, heightening fears that Merapi would "blow".[11] The quake did not appear to be a long-period oscillation, a seismic disturbance class that is increasingly associated with major volcanic eruptions. A further 11,000 villagers were evacuated on June 6 as lava and superheated clouds of gas poured repeatedly down its upper slopes towards Kaliadem, a location that was located southeast of Mt. Merapi.[12] The pyroclastic flows are known locally as "wedhus gembel" (Javanese for "shaggy goat"). There were two fatalities as the result of the eruption.
[edit] 2010 eruption
Main article: 2010 eruptions of Mount Merapi
Recentism.svg
This section may be slanted towards recent events. Please try to keep recent events in historical perspective. (November 2010)
[edit] 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.[14]

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.[15] 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[16]

After a period of multiple eruptions considered to exceed the intensity and duration of those in 1872[17] on 10 November 2010 the intensity and frequency of eruptions was noticed to subside.[18] By this time 153 people had been reported to have been killed and 320,000 were displaced.[19] Later the eruptive activities again increased requiring a continuation of the Level 4 alert and continued provision of exclusion zones around the volcano.[20][21] By 18 November the death toll had increased to 275.[22] The toll had risen to 324 by 24 November and Syamsul Maarif, head of the National Disaster Mitigation Agency (BNPB) explained that the death toll had risen after a number of victims succumbed to severe burns and more bodies were found on the volcano’s slopes.[23]
[edit] 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.[5] 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.[24]

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.[24]

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.[25][26]

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 Institution (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. 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.[27][28]

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.[29]

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.[30] 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.[31]

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.[32]

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.[33][34] 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.[35]

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.[36] 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.[37] 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.[38]

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.[17]

On 9 November a 5.6 magnitude earthquake was felt in Yogyakarta at 14:03:27. The epicenter was 125 kilometers southwest of Bantul, precisely at 8.98 south latitude coordinates (LS) and 110.08 east longitude (BT) at a depth of 10 kilometers.[39][40] The quake's epicenter was at sea and had no tsunami potential. This type of tectonic earthquake was not sourced from the volcanic activity of Mount Merapi.[17] 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).[41]

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.[20]
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.[42] Thousands were evacuated within a radius of 10 kilometres (6.2 mi) around the slopes of the volcano.[43][44]

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.[15][45] 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.[46]

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.[47][48][49] As of 1 November 2010, the death toll from Mount Merapi's blasts had climbed to 38.[50] As of 5 November 2010, the death toll had climbed over 120.[51]

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.[52] 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.[35] 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.[53]

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.[54]

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.[55] 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.[38] 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.[56]

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.[56] 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.[57]

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.[58][59]

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.[60]

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.[22]

By 22nd November, the death toll had risen to 304[61] and by 24 November the toll had risen to 324. Syamsul Maarif, head of the National Disaster Mitigation Agency (BNPB) explained that the death toll had risen after a number of victims succumbed to severe burns and more bodies were found on the volcano’s slopes. In the aftermath of the more intensive eruptive activities Yogyakarta’s Disaster Management Agency reported in late November that there were about 500 reported cases of eruption survivors in Sleman district suffering from minor to severe psychological problems, and about 300 cases in Magelang.[62]
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) per day. 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.[24] 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.[24]

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.[35]

Dr Surono, head of the 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.” [21]
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 pilgrimage from 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.

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.[63][64] 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.[65] 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. Sulfur dioxide, is a colorless gas that can harm human health and cool earth's climate. 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.[66]

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.[67]

For more detailed information on the ash cloud from Mount Merapi and effects upon aviation and health please see the main article on the 2010 eruptions of Mount Merapi
Monitoring
Merapi Volcano January 27, 2007.
Merapi next to Merbabu January 9, 2008.

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.[68]

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.[69] 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.[70]
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.[71] 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.

Source : http://en.wikipedia.org/wiki/Mount_Merapi