Mount Merapi

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This article is about Mount Merapi in Central Java. For
Mount Merapi in West Sumatra, see Mount Marapi.

Mount Merapi

Merapi

Elevation

2,914 metres
(9,616 ft)

Location

Central Java (Indonesia)

Coordinates

7°32′S,
110°26′E

Type

Stratovolcano

Age of rock

400,000
years

Last
eruption

2006

Mount Merapi, Gunung Merapi in Indonesian language,
is a conical volcano in Central
Java, Indonesia. It is the most
active volcano in Indonesia and has erupted regularly since 1548. Its name means Mountain of
Fire. 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.

Several of its eruptions have caused fatalities. It was erupting from 1992 to
2002, and a particularly large explosion killed 43 people in 1994. It began
erupting again in 2006, and scientists believe a large eruption is imminent. In
light of the hazards it poses to populated areas, it has been designated a Decade
Volcano.

Contents

1 Geological
history

2 1992 eruption

3 2006 eruption

4 Monitoring

5 See also

6 References

7 Further reading

8 External links

[edit]
Geological history

Merapi before 2006 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.[1]
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 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.

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 (the most violent eruption in
recent history), 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.

Merapi continues hold particular significance for the Javanese: 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. [2]

[edit]
1992 eruption

Mount Merapi in August 2003 showing steam venting from the
crater.

1992 saw an
eruption begin at Mount Merapi which continued for the next ten years. During
this time, a lava dome was extruded,
growing by up to half a metre per day. In 1994, the dome reached the edge of
the crater, and from then
on, rockfall from the dome produced frequent pyroclastic flows. In late 1994
almost the entire dome collapsed, generating very large pyroclastic flows, which
travelled several kilometres from the summit and killed 43 people.

Following the large eruption of November 1994, a new dome formed in the
crater, and small explosive eruptions continued for several years, generating
scores of lava avalanches and pyroclastic flows every day. Eruptions ended in
late 2002.

Overloading and unstable lava caused landslides. Photo taken
in 2006.

[edit]
2006 eruption

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, 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.[3]

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[4]
and on May 13,
Indonesian authorities raised the alert status to the highest level, ordering
the immediate evacuation of all residents on the mountain.[5]
Eruptions at the volcano are increasing in intensity, and some reports indicate
that large explosions have begun.[6][7]
Should pyroclastic flows
occur, nearby villages will be at very high risk, but many villagers have defied
the dangers posed by the volcano and returned to their villages, saying that
they needed to tend their live-stock and crops.[8]
On May 16
activity has calmed down but scientists are warning it still poses a threat.[9]

On May 27, a
6.2 magnitude
earthquake struck roughly 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 will "blow".[10]
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.[11]

Merapi Volcano January 27, 2007.

[edit]
Monitoring

Pyroclastic flows (2006)

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
(north west 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.

[edit]
See also

Indonesia
Portal

List of
volcanoes in Indonesia

[edit]
References

^
Merapi villagers defy orders to leave homes: The Straits Times

^
Radio New Zealand news report, 23 April 2006

^
Mail & Guardian online, 23 April 2006

^
Lava
flows from Indonesia volcano. BBC News, May 4, 2006 URL Accessed 2006-05-13

^
Red
alert for Indonesia volcano. BBC News, May 13, 2006 URL Accessed 2006-05-13

^
Mount Merapi
Erupts, ANTARA News, 15 May 2006

^
Indonesia's Merapi volcano spews steam, hot ash, Reuters, 15 May 2006

^
Merapi villages defy orders to leave homes: The Straits Times

^
Java volcano activity quietens - BBC News, 16 May 2006

^
Earthquake Leaves Thousands Dead in Indonesia, NY Times, 27 May 2006 URL Accessed
2006-05-27

^
[1], BreakingNews.ie, 6 June 2006 URL Accessed 2006-06-06

[edit]
Further reading

Triyoga, Lucas Sasongko. 1991 Manusia Jawa dan Gunung Merapi - Persepsi
dan Sistem Kepercayaannya Yogyakarta, Gadjah Mada Universsity Press. ISBN
979-420-211-8

Decker, R. and Decker, B. (1997) Volcanoes, 3rd edition, WH
Freeman, New York.

[edit]
External links

Wikimedia Commons has
media related to:

Mount
Merapi

Wikinews has news related to:

Merapi
roars, compulsory evacuation ordered

Mount Merapi's
activity continues to slow down (July 4, 2006)

Live (30
minute) IR Satellite

Live
Volcanic Ash Advisories

Map of Indonesian volcanoes active since 1900

Global Volcanism Program entry

Volcanological Survey of
Indonesia

Info and pictures

Info and
pictures

A lot of sources concerning the
Merapi-eruption in May 2006

Map
of population centers near Merapi (May, 2006)

Merapi
(and other Indonesian Volcanoes)overview and photos (June 06)

The
Independent Mount Merapi Observatory Balerante 149070-Info and Pictures of
Merapi Activities

Retrieved from "http://en.wikipedia.org/wiki/Mount_Merapi"

Categories: Stratovolcanoes
| Subduction
volcanoes | Volcanoes of
Java | Mountains of
Indonesia | Decade
Volcanoes | Active
volcanoes | Volcanoes
between 2,000 and 2,999 meters

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This page was last modified 01:28, 20 May 2007.

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