Mount Merapi

Mount Merapi, Gunung Merapi (literally Mountain of Fire in Indonesian/Javanese), is a conical volcano 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, 

Merapi, July 2005,

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 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 64 people on November 22 in 1994, mostly in the town of Muntilan, west of the volcano.[citation needed] 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 10km (6 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 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. 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 1930.

There 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.

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 meters, compared to 75 metres 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.

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 and on May 13, Indonesian authorities raised the alert status to the highest level, ordering the immediate evacuation of all residents on the mountain.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. Activity calmed by the middle of May.

On May 27, a 5.6 magnitude earthquake struck roughly 50km (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". 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.The pyroclastic flows are known locally as "wedhus gembel" (Javanese for "shaggy goat"). There were two fatalities as the result of the eruption.

 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). 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 effected 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 Merapi erupted three times on Monday afternoon 25 October 2010, spewing lava down its southern and southeastern slopes. Three major eruptions were recorded at 2:04PM, 2:24PM and 3:15PM. 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 5:02PM. By 6:54PM 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, visable 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.

By early on the morning of Saturday 30 October the volcano was erupting again. The eruptions were reported to be louder and stronger than the eruptions that killed 34 people on the previous Tuesday and ash was falling more than 12 kilometres (7.5 mi) away.

 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 belonging to a yet un-named Indonesian Red Cross worker.

 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 top of dome having by then reached a height of 6,858.635 metres (22,502.08 ft).

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.

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.

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 signify 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