Iliwerung

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  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 8.53°S
  • 123.57°E

  • 1018 m
    3339 ft

  • 264250
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

28 August-3 September 2013

CVGHM reported that observers at a post 6 km away from Iliwerung reported that diffuse fumarolic emissions from the crater were visible during the mornings from 19 August to 1 September. Seismicity decreased on 19 August and remained at normal levels. On 2 September the Alert Level was lowered to 1 (on a scale of 0-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

Index of Weekly Reports


2013: August
2001: October

Weekly Reports


28 August-3 September 2013

CVGHM reported that observers at a post 6 km away from Iliwerung reported that diffuse fumarolic emissions from the crater were visible during the mornings from 19 August to 1 September. Seismicity decreased on 19 August and remained at normal levels. On 2 September the Alert Level was lowered to 1 (on a scale of 0-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


14 August-20 August 2013

CVGHM reported that observers at a post 590 m a.s.l. and 6 km away from Iliwerung reported that diffuse fumarolic emissions from the crater were visible during the mornings from 1 to 19 August. Seismicity fluctuated during the month, but 81 shallow volcanic earthquakes were detected between 1606 and 1741 on 19 August, compared to a total of 30 the previous 18 days. The Alert Level was raised to 2 (on a scale of 0-4).

At 0714 on 20 August an eruption from the submarine SE flank vent, Hobal, ejected dense white plumes 2 km a.s.l. that drifted S. Incandescence at sea level was observed at 0746, and the water around the eruption site turned yellow. Fishermen and tourists were not permitted within a 2-km-radius of Hobal.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


31 October-6 November 2001

An increase in tectonic earthquakes around Iliwerung during 17-26 October led VSI to raise the Alert Level from 1 to 2 (on a scale of 1-4). From 2 to 11 earthquakes were felt per day with Modified Mercalli intensities of I-II. Visual and instrumental monitoring did not show a significant change in volcanic activity.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


Index of Monthly Reports

Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

08/1983 (SEAN 08:08) Submarine explosions

08/1993 (BGVN 18:08) Submarine eruption produces 100-m-high water columns

10/1993 (BGVN 18:10) Follow-up on Hobal vent eruption and 1979 tsunami

06/2003 (BGVN 28:06) Increase in felt earthquakes during October 2001


Contents of Monthly Reports

All information contained in these reports is preliminary and subject to change.

All times are local (= UTC + 8 hours)

08/1983 (SEAN 08:08) Submarine explosions

Explosions occurred 17 and 18 August from a submarine vent (Gobal) S of Iliwerung. No casualties were reported.

Its previous eruption began with submarine activity in December 1973; by July 1974, there were two small islands at the eruption site and a third emerged in August. All have subsequently been eroded away. In July 1979, about 50 x 106 m3 of Iliwerung were removed by a landslide. About 1/3 of this material entered the sea, and (probably aided by additional submarine slumping) generated tsunami that killed hundreds of people.

Information Contacts: L. Pardyanto, VSI; AFP.

08/1993 (BGVN 18:08) Submarine eruption produces 100-m-high water columns

A submarine eruption in the Alor Strait was reported on 16 September by a Japanese cargo ship. Crew members felt three shocks at around 0630, and observed a rising steam cloud or plume soon after. Explosions occurred at 0656 and 0855. Each explosion produced a water column ~100 m high, followed by a cone of upwelling water; no other unusual phenomena were observed after the explosions. From ~6.5 km away, the ship located the explosion site at about 8.538°S, 123.592°E, SW of Iliwerung volcano. The VSI confirmed that an eruption had occurred from the submarine Hobal vent at Iliwerung. . . .

Information Contacts: JMA; M.A. Purvawinata, VSI.

10/1993 (BGVN 18:10) Follow-up on Hobal vent eruption and 1979 tsunami

In September, Hobal vent on the SE submarine flanks of Iliwerung volcano (figure 1) produced an eruption that broke the ocean surface (18:08). . . . During the eruption pyroclastic material sank within ~200 m of the point where it penetrated the ocean surface, consequently no samples were obtained. This suggests that the erupted material lacked sufficient closed vesicles to allow it to float.

Figure 1. Map showing Iliwerung volcano, Hobal vent, and the known extent of the 1979 landslide that triggered a tsunami. Note that N is to the upper right. Courtesy of VSI.

Depth to the Hobal vent has never been measured, though in 1979 the VSI estimated it at 50 m. The bathymetry of this region is also significant because of its relevance to tsunamis. A 1979 landslide NW of Iliwerung reached the sea (figure 1), and probably aided by additional submarine slumping, triggered a tsunami that killed hundreds of people. Several areas evacuated prior to the 1979 landslide and tsunami still remain evacuated. Relevant aspects of the tectonic setting, and the effects of a 1992 earthquake-triggered tsunami on the N side of Flores Island are discussed by Yeh and others (1993).

Seismic data were acquired by VSI prior to the September Hobal eruption. The data were received at Lamaheku seismic station, at ~75 -m elevation on the W flank of Iliwerung, 4.5 km from the Hobal vent. The seismic record is incomplete, but for July to September 1992, the number of volcanic B-type earthquakes averaged >70/month, reaching ~96 in September 1992. A gap in the record occurred in early 1993, but later in the year, B-type earthquakes progressively increased from ~30 in May to 60 in September. Thus, the B-type events increased prior to the September eruption, but at least one interval with more B-type events passed without reports of concurrent eruptions.

VSI has informed local governments about the hazards of future eruptions, and has established a volcanic danger area that includes at least four communities on Iliwerung. Local VSI staff continue to monitor the region, and as of 1 November, were in the process of installing a new seismic station.

Reference. Yeh, H., Imamura, F., Synolakis, C., Yoshinobu T., Liu, P., and Shi, S., 1993, The Flores Island tsunamis: Eos, Transactions of the American Geophysical Union, v. 74, no. 33.

Information Contacts: W. Tjetjep, VSI.

06/2003 (BGVN 28:06) Increase in felt earthquakes during October 2001

During 17-26 October 2001 the Volcanological Survey of Indonesia reported an increase in felt earthquakes. A total of 2-11 events occurred per day, with Mercalli magnitudes of I-II. The earthquakes S and P wave arrival times differed by between 1 and 35 seconds. Visual and instrumental monitoring revealed a lack of significant changes. The Alert Level was increased from 1 to 2 (on a scale of 1-4). No further reports were issued through at least May 2003.

Information Contact: Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (Email: dali@vsi.esdm.go.id, URL: http://www.vsi.esdm.go.id/).

Constructed on the southern rim of the Lerek caldera, Iliwerung forms a prominent south-facing peninsula on Lembata (formerly Lomblen) Island. Craters and lava domes have formed along N-S and NW-SE lines on the complex volcano; during historical time vents from the summit to the submarine SE flank have been active. The Iliwerung summit lava dome was formed during an eruption in 1870. In 1948 Iligripe lava dome grew on the eastern flank at 120 m altitude. Beginning in 1973-74, when three ephemeral islands were formed, submarine eruptions began on the lower SE flank at a vent named Hobal; several other eruptions took place from this vent before the end of the century.

Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
2013 Aug 20 2013 Aug 20 Confirmed 0 Historical Observations Hobal (submarine vent on SE flank)
1999 May 22 1999 Sep (in or after) Confirmed 0 Historical Observations Hobal (submarine vent on SE flank)
1993 Sep 15 1993 Sep 19 Confirmed 2 Historical Observations Hobal (submarine vent on SE flank)
1983 Aug 17 1983 Aug 18 Confirmed 1 Historical Observations Hobal (submarine vent on SE flank)
[ 1976 Mar 8 ] [ Unknown ] Uncertain 0   Hobal (submarine vent on SE flank)
1973 Dec 5 1974 Aug 22 Confirmed 2 Historical Observations Hobal (submarine vent on SE flank)
1952 Mar 24 Unknown Confirmed 1 Historical Observations
1951 Nov 12 1951 Nov 16 Confirmed 2 Historical Observations
1950 Sep 10 1950 Oct 2 Confirmed 2 Historical Observations
1949 Apr 9 1949 Apr 29 Confirmed 2 Historical Observations
1948 Apr 7 1948 Nov 26 Confirmed 2 Historical Observations East flank (Iligripe)
[ 1941 Jun 5 ] [ Unknown ] Uncertain    
1928 Unknown Confirmed 2 Historical Observations Iliwerung
1910 Unknown Confirmed 2 Historical Observations Iliwerung
1870 Unknown Confirmed 3 Historical Observations Iliwerung (Iliadowajo)

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.



Synonyms
Iliweroeng | Hiro | Lama Heru | Ilipoegora | Penoetoen


Craters
Feature Name Feature Type Elevation Latitude Longitude
Ado Wajung
    Ado Wadjung
Crater 1018 m
Lerek Caldera
Lusitobe North Crater 300 m
Lusitobe South Crater 247 m


Domes
Feature Name Feature Type Elevation Latitude Longitude
Iligripe
    Ilipetrus
Dome - Crater 190 m
Ilimonjet Dome 592 m
Ilipenutun Dome 172 m
A landslide in 1979, not associated with an eruption, originated from the northern end of the Iliwerung volcanic massif. The resulting debris avalanche swept into the Indian Ocean at a high velocity and produced a tsunami that scoured the shoreline of Lembata (Lomblen) Island, killing more than 500 persons. The extent of the runup of the tsunami can be seen forming the flat barren area in the center of the photo, which was taken from the SW on July 27, 1979, shortly after the tsunami.

Photo by Ruska Hadian, 1979 (Volcanological Survey of Indonesia).
The Watuwawer fumarole field at Iliwerung volcano provides a permanent heat source for cooking utilized by people living on the flanks of the volcano.

Photo by Ruska Hadian, 1979 (Volcanological Survey of Indonesia).
A lava dome, formed during the first historical eruption of Iliwerung volcano in 1870, occupies the summit crater of the volcano, seen here in 1979 from the western rim of Ado Wajung crater. Iliwerung forms one of the south-facing peninsulas on Lembata (Lomblen) Island, and has a series of lava domes and craters along N-S and NW-SE lines. Many of these vents, including submarine vents offshore, have erupted in historical time.

Photo by Ruska Hadian, 1979 (Volcanological Survey of Indonesia).
A composite photo taken in 1979 shows the crater at summit of Iliwerung lava dome. The summit lava dome was formed during an eruption in 1870, the first historical eruption of Iliwerung volcano.

Photo by Ruska Hadian, 1979 (Volcanological Survey of Indonesia).
Iligripe lava dome on the SE flank of Iliwerung volcano on Lembata (formerly Lomblen) Island formed during an eruption from April 7 to November 26, 1948. Growth of the 190-m-high lava dome, seen here at the center of this 1979 photo, was accompanied by explosive eruptions and pyroclastic flows.

Photo by Ruska Hadian, 1979 (Volcanological Survey of Indonesia).
A lava dome, formed during the first historical eruption of Iliwerung volcano in 1870, occupies the summit crater of the volcano, seen here in 1979 from the rim of Ado Wajung crater. Iliwerung forms one of the south-facing peninsulas on Lembata (formerly Lomblen) Island, and has a series of lava domes and craters along N-S and NW-SE lines. Many of these vents, including submarine vents offshore, have erupted in historical time.

Photo by Volcanological Survey of Indonesia.
Four volcanoes are seen in this NASA Space Shuttle image (with north to the upper left) of Solor (lower left), Adonara (upper left), and Lembata (right) Islands. Ililabalekan volcano on SW Lembata (formerly Lomblen) Island is the only one of these without historical eruptions, although fumaroles are found near its summit. A satellitic cone was constructed on the SE flank of the steep-sided volcano, and four craters, one of which contains a lava dome and two small explosion pits, occur at the summit of Mount Labalekan.

NASA Space Shuttle image ISS009-E-7480, 2004 (http://eol.jsc.nasa.gov/).

The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title.

Kusumadinata K, 1979. Data Dasar Gunungapi Indonesia. Bandung: Volc Surv Indonesia, 820 p.

Neumann van Padang M, 1951. Indonesia. Catalog of Active Volcanoes of the World and Solfatara Fields, Rome: IAVCEI, 1: 1-271.

Sudradjat A, 1977. . (pers. comm.).

Volcano Types

Complex

Tectonic Setting

Subduction zone
Crustal thickness unknown

Rock Types

Major
Basalt / Picro-Basalt
Andesite / Basaltic Andesite

Population

Within 5 km
Within 10 km
Within 30 km
Within 100 km
968
4,318
79,569
665,081

Affiliated Databases

Large Eruptions of Iliwerung Information about large Quaternary eruptions (VEI >= 4) is cataloged in the Large Magnitude Explosive Volcanic Eruptions (LaMEVE) database of the Volcano Global Risk Identification and Analysis Project (VOGRIPA).
WOVOdat WOVOdat is a database of volcanic unrest; instrumentally and visually recorded changes in seismicity, ground deformation, gas emission, and other parameters from their normal baselines. It is sponsored by the World Organization of Volcano Observatories (WOVO) and presently hosted at the Earth Observatory of Singapore.
EarthChem EarthChem develops and maintains databases, software, and services that support the preservation, discovery, access and analysis of geochemical data, and facilitate their integration with the broad array of other available earth science parameters. EarthChem is operated by a joint team of disciplinary scientists, data scientists, data managers and information technology developers who are part of the NSF-funded data facility Integrated Earth Data Applications (IEDA). IEDA is a collaborative effort of EarthChem and the Marine Geoscience Data System (MGDS).
Smithsonian Collections Search the Smithsonian's NMNH Department of Mineral Sciences collections database. Go to the "Search Rocks and Ores" tab and use the Volcano Name drop-down to find samples.