Eruption of Merapi in 2010

Background

The Merapi is a stratovolcano rising to 2911 ³ or 2968 meters above sea level in the center of the island of Java in Indonesia ⁴ . It is located in one of the most densely populated regions in the world, with values ​​of up to 1,000 inhabitants / km ^2 5 , particularly with the city of Yogyakarta in the south, whose urban area had 723,210 inhabitants in 1990 ⁶ , and the plain from Kedu to the west ⁴. The feet of the volcano and its slopes to a relatively high altitude are inhabited by many farmers , attracted by the fertility of the soil ⁷ which allow several harvests per year, including rice . These lands are fertilized by the volcanic ash released by the Merapi and fall back in the vicinity with the winds . These ashes are emitted during frequent volcanic eruptions , 49 between that of 1548 , the first observed by Europeans , and that started on October 26th. In 2010 , including 23 during the xx ^th century is one every four years about ⁸ . These eruptions usually result in the growth of a lava dome in the summit crater ⁸ . By the pressure in the magma chamber , this lava dome collapses or explodes producing pyroclastic which deposit significant layers of ash ⁸ . In case of heavy rains , frequent under the tropical climate of Java, these ashes can form lahars, mudslides that can travel for tens of kilometers by doing extensive destruction on their way ⁸ .

If we dismiss a suspicion of eruption on May 19 , 2008, the previous eruption of Merapi unfolded March 2006 the August 9 , 2007⁸ . Typical of Pelean eruptions , it resulted in the formation of a lava dome, which gave rise to a flow of lava pasty escaping crater ⁸ . Nevertheless, fiery clouds occurred during explosions of volcanic explosive index of 1 when the internal pressure of the volcano became too great ⁸ . The volume of lava emitted is greater than 4 10 ⁶ m ^3 8 . Despite the evacuation of threatened populations, the eruption caused several deaths and damage ⁸ .

After two and a half years of rest, the Merapi shows signs of awakening from March 2010, with a volcano swelling from 0.1 to 0.3 millimeters per day ⁹ . This phenomenon is accelerating at the end of the summer to 11 millimeters dailies on 16 September , 0.6 centimeters end of September , 10.5 centimeters 21 October and 42 centimeters 24 October ⁹. At the same time, a seismic crisis appears at the beginning of September and the lava dome warms up from the end of October ⁹ . In addition to these measures, there are phenomena such as an avalanche of debris on September 12 and the formation of a white volcanic plume rising 800 meters above the summit of Merapi.⁹ . The authorities are then convinced of the imminence of an eruption and raise the alert level to level 2 on September 19th , level 3 on October 21st and level 4, the highest on October 25th ⁹ . The same day they launch a recommendation to people located within ten kilometers around the summit, between 11,000 and 19,000 people , to immediately evacuate their villages ⁹ .

Procedure

The rash starts on 26 October at 17 pm local time by explosions producing pyroclastic flows running down the west-southwest and southeast flanks ⁹ . This series of pyroclastic flows, which last for most between two and nine minutes apart two of them that are developed during 33 minutes , ends at 18 pm 54 ⁹ . These fiery clouds are accompanied by muffled sounds, a volcanic plume rising to about 4,500 meters of altitude ⁷ and the reddening of the lava domeis visible from the north ⁹ .

After this first eruptive episode, the activity gets more sustained on the night of 29 at 30 October to 1 pm ^10 , 11 . The volcanic ash falling to ten kilometers from the volcano and explosions are more noisy, thousands of people still living in the evacuation zone fled in the night, bringing the number of refugees at 50,000 ^11 , 12 . On November 3 , in the face of the intensification of the explosions, the authorities carry the radius of the evacuation zone to fifteen kilometers around the summit of the volcano ¹³. The next day, the explosions are continuing even earning power ¹³ . The volcanic plume reached an altitude of eight kilometers and numerous pyroclastic flows that cascade down the south side are up to nine kilometers in length ¹³ .

From November 18 , the eruption diminished in intensity with a drop in seismic activity , the number of hot clouds and the altitude of the volcanic plume reaching between 4.5 and 6 kilometers ¹⁴ . Of lahars begin to form on the slopes of the volcano during the month of November 2010 ¹⁴ . Those of 3 and January 9 , 2011cause destruction, one dead, one wounded and outlets ¹⁵ . The volcanic risk scale is lowered to 3 on a scale of 4 on December 4 , 2011¹⁶ and at 2 the January 9 , 2011¹⁷ , which reflects the end of this eruption ¹⁸ .

Consequences

The burning clouds of the first day of the eruption killed 34 people ^11 , 12 including Mbah Maridjan, the juru kunci of Merapi ¹⁹ . The latter refused to evacuate his village of Kinahrejo despite repeated requests to the authorities and many of those present with him in his house ¹⁹ . Thirteen of them were killed on the spot with him by gas and volcanic ash at 1000 ° C of a pyroclastic flow that destroyed the village ¹⁹ . The body of Mbah Maridjan was found the next morning in the position ofprayer , fulfilling its spiritual role, by a team of rescuers ¹⁹ . Before the power of the eruption, the evacuation order is rather well respected, but especially women, children and the elderly, men preferring to stay to look after their fields or their beasts ⁷ . The 1 ^st November , the death toll rises to 38 dead ²⁰ . On November 4 , the rejection of volcanic ash in the atmosphere is such that the authorities require airlines not to approach more than twelve kilometers from the volcano ¹³. Although remaining open, the two closest airports to Merapi see some companies cancel flights ¹³ .

In total, the number of victims was 353 on 3 December ²¹ , more than 150 injured and the number of displaced more than 320,000 on 8 November ^{22 , 13 , 23} . The authorities estimate the cost of damage to 5500 billion of rupees or 500 million of euros , in early February 2011 and this amount is increasing due lahars ¹⁸ .

For the only sector of agriculture , the losses exceed 100 million of US dollars , affecting local livelihoods ²⁴ . Most of the crops destroyed by the eruption are volcanic ash rains : over 2,500 hectares of crops in the Sleman kabupaten , 5,000 hectares of salak and 100 hectares of rice lost in the Magelang kabupaten , several thousand of hectares of crops in Boyolali kabupatenand Klaten ²⁴ . 1,961 heads of cattle died during the eruption ²⁴ .

Since the eruption ended in early February 2011, the destroyed villages are under a black tourism which particularly benefits the residents of the affected areas, some of which are converted into small sellers ¹⁸ .

During the expansion of the exclusion zone on 3 November, the crisis management plans usually used are overwhelmed by the extent of the evacuation: no refugee camp was planned to accommodate the one million people leaving the country. area threatened by intensification of the eruption ²⁵ . Makeshift solutions are implemented, such as the home of more than 21,900 refugees at the stadium Maguwoharjo in the regency of Sleman ²⁵ ; other smaller camps are open around ²⁵ . The eruption of 2010 has thus highlighted the need to review evacuation plans and measures to be taken at the next alert ²⁵ .

Notes and references