Merapi (Java)

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Merapi
The Merapi in July 2005

The Merapi in July 2005

height 2914  m (varies)
location Java ( Indonesia )
Coordinates 7 ° 32 ′ 31 ″  S , 110 ° 26 ′ 42 ″  E Coordinates: 7 ° 32 ′ 31 ″  S , 110 ° 26 ′ 42 ″  E
Merapi (Java) (Java)
Merapi (Java)
Type Stratovolcano
Age of the rock 400,000 years
Last eruption 2020

The Merapi (from Sanskrit meru 'mountain', Indonesian api 'fire': 'fire mountain') is a stratovolcano on the island of Java in Indonesia . It is one of the most active volcanoes in the country and is considered one of the most dangerous volcanoes in the world.

The Merapi is not to be confused with the Marapi volcano on the island of Sumatra and also not with the extinct Merapi, one half of the twin volcano Ijen-Merapi in the Ijen volcano complex on the east end of the island of Java. The word gunung means "mountain" and is always prefixed to the proper names of mountains in Indonesian, which is why all mountains listed are called Gunung Merapi in Indonesian .

mythology

"Situation plan" by Merapi from November 1836, from: Franz Wilhelm Junghuhn : Topographische Reisen
Dump on the Merapi in 1836. From: Franz Wilhelm Junghuhn : Java album on the Java work , its shape, plant cover and internal construction .

The volcano has a special meaning for the people of Java: It is one of four places where officials of the royal palaces of Yogyakarta and Surakarta (Solo) make offerings to appease the ancient spirits of Java. In the Javanese belief there is an invisible kingdom on the Merapi , whose king protects the inhabitants around the volcano.

The spiritual guardian of the volcano, Ki Surakso Hargo, known as Mbah Marijan, lived at high altitude on Merapi until the volcano erupted in 2010. He served the imagination of both the spirits and demons of Merapi and the Sultan of Yogyakarta, by whose predecessor (Sri Sultan Hamengkubuwono IX ) he had been appointed guardian of the volcano. In the opinion of the locals, including the sultan, he was able to predict the behavior of the mountain. The residents were more likely to listen to his advice than to the advice of the scientists. Especially in rural areas, where the majority of Javanese live, belief in spirits and ancestral cults has persisted to this day , which is partly due to the fact that some Javanese were only superficially Islamized. Mbah Marijan was killed along with 15 other people when the volcano erupted on October 26, 2010.

geography

The Borobodur stupa with the smoking Merapi in the background

The Merapi is located about in the middle of Java about 35 km north of the city of Yogyakarta . With its highly explosive activity as a result of its viscous magma, which piles up into dunnage and results in devastating lahars in eruptions , it is considered the most dangerous volcano in Java.

Tens of thousands of people live on the flanks of the volcano; some places are up to 1700  m altitude. Nearby are the historic temples of Prambanan and the stupa of Borobudur ; both are part of the world cultural heritage . Borobudur was buried by a layer of ash and rock when the Merapi erupted in 1006 and was covered by a 3 cm thick acidic ash layer which attacked the building blocks during the eruption in 2010 until the beginning of November.

geology

Map of the volcanoes in Indonesia

Indonesia has the highest density of volcanoes in the world and is part of the so-called “ Pacific Ring of Fire ”, to which the Gunung Merapi also belongs.

Because of Merapi, a stratovolcano , he alternates between Ash eruptions and lava -Ausflüssen. These different eruptions contribute to its typical appearance: the stratification of the volcano consists alternately of ash, lava, ash, etc.

Gunung Merapi is the youngest and southernmost of a group of volcanoes in southern Java. It is located in a subduction zone where the Australian plate slides under the Eurasian plate . Stratological analyzes revealed that the eruptions in the area of ​​the volcano began about 400,000 years ago in the Pleistocene . From that time until around 10,000 years ago, the eruptions increased in the usual way. The outflowing lava was basaltic at this time . Later the eruptions became more explosive and viscous andesitic lava often formed lava domes . The collapse of these lava domes often resulted in pyroclastic currents and larger explosions. The explosions in turn led to eruption columns which, when they collapsed, generated further pyroclastic currents.

In 2006 a large object was discovered under the Merapi, which is presumably an enormous magma chamber . Seismic waves are clearly slowed down below Java by them; it contains about three times as much magma as the Tambora spewed out during the largest volcanic eruption in the last 10,000 years.

ecology

The uppermost part of the volcano is without vegetation due to the regular eruptions. Extensive casuarina forests , which are under nature protection, lie below this zone .

Volcanic activity

Merapi, 1930

The Merapi is currently considered a so-called open system - this reduces its explosive power because less pressure can build up; however, any closure of the chimney harbors great risks.

The population of Yogyakarta trusts that the main direction of the eruptions is away from the big city, also due to the fact that offerings are regularly made every year; this has been the case for the past few decades. During the eruptions in 2010, however, some also took place in the direction of the agglomeration ; Deposits from previous eruptions have been found in its center.

Typical smaller eruptions occur every two or three years. Larger outbreaks occur on average every ten to fifteen years. Considerable eruptions often caused the death of many people and took place mainly in the years 1006, 1786, 1822, 1872 (the most violent eruption in recent times, numerous villages were destroyed here) and 1930; here 13 villages were destroyed and 1,400 people were killed by pyroclastic currents.

Typical for the Merapi is this discharge of hot ash clouds (so-called pyroclastic currents or nuée ardente ), which reach a temperature of over 700 ° C and fall down the volcanic slopes at breakneck speed, forming a kind of air cushion as a sliding cushion.

In the past, there have been several violent eruptions that resulted in gas or mud avalanches. There have been 68 eruptions since 1548 ().

In 1006 a very large eruption covered the entire central part of Java with volcanic ash . It is believed that this devastation resulted in the collapse of the Hindu civilization of the Kingdom of Mataram . In the subsequent power vacuum , the Muslims took control of Java. During this outbreak, u. a. the nearby Buddhist temple Borobudur buried under hot ashes and stones.

1992 to 2002

Satellite image of the Merapi. Recorded in August 2003 by NASA

One of the more recent eruptions of the Merapi began in 1992 and lasted ten years. During this time, a lava dome formed that rose up to half a meter per day. In 1994 the lava dome reached the edge of the volcanic crater . Since then, rockfalls from the lava dome have led to regular pyroclastic flows. Towards the end of 1994 , almost the entire lava dome collapsed, creating a very large pyroclastic current that went several kilometers from the summit and killed 43 people. A total of 66 people were killed in 1994 as a result of volcanic activity.

After a major eruption in November 1994, a new lava dome formed in the volcano's crater. In the years that followed, many small eruptions followed, causing numerous lava avalanches and pyroclastic flows every day . The eruptions ended in late 2002.

2006

Increased seismic activity of the Merapi has been observed again since summer 2005. These seismic activities occurred at increasingly regular intervals and the volcanic cone swelled. In April 2006, the neighboring locations on the volcano were put back into the highest alarm state for the first time so that they could be evacuated at any time. On April 19, 2006, the smoke from the crater reached a height of 400 meters. The day before, the smoke only reached a height of 75 meters.

After nine quakes and noticeable magma movements, around 600 elderly people and children were evacuated from the slopes of the volcano on April 23, 2006. At the beginning of May 2006, the volcano increasingly emitted clouds of ash, smoke and lava. At that time, more than 5,000 people left their homes. In the southern area of ​​the summit, a new ten meter high lava dome formed within a few days. It had an estimated volume of around 2.4 million m³ and was comparable to the situation in 1992. Contrary to expectations, the Gunung Merapi initially calmed down on May 16, 2006. Lava continued to flow out of the volcano, but the ashes, gas and stone emissions decreased. Nevertheless, the Gunung Merapi continued to be in the highest alarm state.

Pyroclastic flow at Merapi, June 2006

On May 27, 2006, a 6.3 magnitude earthquake struck the Yogyakarta region, killing thousands and causing severe damage. Although the earthquake was not associated with a major eruption of Gunung Merapi, the volcano subsequently emitted a three-kilometer-high ash cloud and was classified by scientists as even more dangerous. It is believed that the earthquake loosened a rock that closes the volcano's embers chimney and that the pressure conditions in the volcano may have changed. On June 6, 2006 parts of Gunung Merapi dissolved into liquid rock, which now threatens the west and south-west slopes of the volcano from lava and hot gas clouds. In addition, the volcano spewed out large amounts of hot gas and ash clouds in the following days, which fell up to five kilometers away on the mountain slopes and severely impaired the vegetation there . Tens of thousands of people had now fled the area around the volcano.

2010

Pyroclastic Current as seen from space on October 30, 2010; earthobservatory.nasa.gov, NASA Terra satellite

In September of that year, the Center of Volcanology and Geological Hazard Mitigation (CVGHM) detected a significant increase in the volcano's seismic activity. On September 13, 2010, billows of white smoke were sighted 800 m above the volcano. In addition, as of September 16, 2010, surface swelling increased from 0.1 to 0.3 mm to a rate of 11 mm per day. Countless earthquakes were recorded over September 19, so the next day the CVGHM raised the alert level to 2 (on a scale from 1 (lowest) to 4 (highest)).

On October 26, 2010, the Indonesian government declared the highest warning level for the area around Merapi and called on the population to evacuate . About 19,000 people live in the densely populated evacuation area 10 km around the crater. On October 26, 2010, the volcano erupted and threw smoke and volcanic ash up to a height of 1.5 kilometers three times. This outbreak killed 38 people and injured many more, particularly from burns.

On October 29, 2010 at 8 p.m. ( CEST , local time : October 30, 2010, 1 a.m.), a new strong eruption occurred. The area was evacuated within a radius of 10 km from the volcano. South of the volcano, fields and trees up to a distance of 4 km were burned by the hot ash cloud.

On November 5, 2010, the volcano erupted again at night (local time) and hurled rubble and ash 4 km into the air. In this new eruption, over 70 people lost their lives; some of the corpses were burned beyond recognition as a result of a pyroclastic flow. The authorities had recently expanded the security zone from 15 to 20 km, but many residents of the nearby villages had resisted the evacuation. The Yogyakarta airport has been closed.

In the following days, more and more severe eruptions followed with the emission of ash clouds up to a height of 6 km; therefore numerous flights to and from the capital Jakarta have been canceled.

In mid-November, the authorities gave a slight all-clear. Thereupon, about 35,000 of the evacuated or refugee people started their way home from their emergency shelters to their villages covered by a thick layer of ash. At the end of November, the protection zone was reduced again and Yogyakarta Airport was reopened.

Up to November 29th of the year, the preliminary damage balance of this outbreak included u. a. 324 dead, more than 400 injured, numerous missing, 26 destroyed villages, more than 390,000 people in emergency shelters; the outbreak has been described as the worst in 100 years.

On November 29th, several lahars came off the Merapi . A particularly large stream of mud flowed through the Kali Code River and flooded several houses on its bank; again over 400 people had to flee.

2018

On the morning of May 11, 2018, a phreatic explosion occurred on the volcano. As a result, evacuations were called in an area of ​​five kilometers. The Adisucipto International Airport was closed because of the ash cloud.

On June 1, 2018, there was a two-minute violent eruption at 8:20 am local time. As a result, ash was thrown up to a distance of 6 km around the crater and the height of the ash cloud reached about 9 km. On May 24th there was a similar but smaller eruption late in the evening. Volcanic researchers on site explained that chambers in the volcano refill with magma, but it is unknown when this reaches the surface. An immediate eruption with lava was not expected.

2020

On February 13, 2020, a column of ash rose about 2 km during a two and a half minute eruption.

On March 3, 2020, a pillar of ash rose about 6 km during a seven-minute eruption.

On March 27, 2020, an ash column rose about 5 km in the course of an eruption.

There were 2 outbreaks on June 21, 2020. Ash particles rose several kilometers with the warmed air.

monitoring

The Gunung Merapi is part of a very active volcano monitoring program. Seismic monitoring began in 1924. Some of these monitoring stations still exist today. Equipment in the Babadan (northwest), Selo (between Merbabu and Gunung Merapi) and Plawangan monitoring stations has been renewed for decades since they were built. However, in the 1950s and early 1960s, some surveillance stations lacked equipment and funds. It wasn't until after the 1970s that there was an improvement when new equipment was made available. Some of the earlier monitoring stations were destroyed in the 1930 eruption. Newer monitoring stations were subsequently relocated.

The same procedure was followed after the eruption in 1994, as a result of which the Plawangan monitoring station and its equipment were relocated to Kaliurang. This was a response to the threat to the personnel at the monitoring station at high altitudes. The eruption in 1930 was found to be preceded by a number of major earthquakes. There is currently a network of eight seismographs around the volcano . This network allows researchers the exact determination of the herd of the quake. 1.5 km below the summit is a zone in which no earthquake sources have been detected so far. It is believed that there is the magma reservoir from which the eruptions are fed. In addition, magnetic measurements and measurements of the inclination of the volcanic cone are made. It was discovered that small changes in the local magnetic field can be measured during eruptions. By measuring the inclination, the volcano can be determined to expand, which is caused by the filling of the magma chamber . So-called lahars can also be detected through seismic monitoring . A lahar poses a great danger to the volcano and is caused by rain, which sets the pyroclastic current deposits in motion again. It can be tracked because it creates a high frequency seismic signal. Observations have shown that precipitation of around 50 mm per hour is the threshold value for the occurrence of lahars.

See also

Web links

Photos and videos

Commons : Merapi  - collection of images, videos and audio files

Scientific contributions

Individual evidence

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  2. ↑ a b TVNZ Television - OneNews, "Volcano grows 10 meters in three days" , May 2, 2006 .
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  8. ↑ a b newspaper Der Sonntag , November 7, 2010, news , AFP: As from the horror film .
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  29. ↑ "Merapi volcano erupted again". ORF online, accessed on October 29, 2010 .
  30. ^ Glowing volcanic ash: More than 70 dead , derStandard.at, November 5, 2010.
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  33. ↑ spiegel.de, November 10, 2010, Panorama, Moment : Unter dem Vulkan (November 12, 2010).
  34. ↑ News from Deutschlandfunk from November 13, 8:30 a.m. CEWT.
  35. ^ Indonesia evacuates residents, shuts airport after Java volcano erupts. Retrieved May 11, 2018 .
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