Increased seismicity and whitish vapor emissions

Deep volcanic earthquakes, seismic tremor, and five small explosions with corresponding ash emission were reported from Kaba in August 2000 (BGVN 25:11). Since then, Kaba has been quiet, but even in its normal state it almost always emits whitish plumes 25-100 m high.

On 20 October 2009, the Center of Volcanology and Geological Hazard Mitigation (CVGHM) reported that seismic activity from Kaba increased in August and remained elevated into September and October. Inflation was also detected. When weather permitted, diffuse white plumes were seen rising ~ 25-50 m above the summit crater complex and drifting E. Based on the deformation and increased seismicity, CVGHM raised the Alert Level to 2 (on a scale of 1-4).

From January through August 2009, the frequency of deep volcanic earthquakes averaged 85 events per month, but in August the number of events rose to 257 per month. During August-September, whitish plumes remained similar to September-October. In September seismicity fluctuated but tended to increase. Earthquakes and total tremors recorded at Kaba's monitoring post are shown in table 2.

Table 2. Summary of Kaba seismic data recorded during 12 September-20 October 2009. Courtesy of CVGHM.

Deformation measurements taken using an EDM (electronic distance measurement) method were as follows: Biring station, shorter by 10 cm; Voelsang station, longer by 0.4 cm; and Kaba station, shorter by 2 cm.

Measurements of the crater water temperature on 15 October showed a reading of 72°C, with a pH of 3.24. The sulfurous and associated solfatara areas recorded a temperature of around 106-107°C. There was no other activity in the area of the crater.

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://vsi.esdm.go.id/).

Information is preliminary and subject to change. All times are local (unless otherwise noted)

December 1979 (SEAN 04:12) Cite this Report

Only solfataric activity accompanies 17 December earthquake

Some press reports indicated that increased activity from Kaba and neighboring Bukit Daun volcanoes preceded a destructive 17 December earthquake. Adjat Sudradjat and Suparto Siswowidjoyo report that no unusual volcanic activity took place. Thick white solfataric vapor was emitted from two craters (Kaba Lama and Kaba Besar) on Kaba, which last erupted in 1956. Temperatures of solfataras and a crater lake at Kaba were measured on several occasions in the past nine years (table 1). Active fumaroles are present on Bukit Daun, but the volcano has not erupted in historic time.

Table 1. Temperatures of solfataras and a crater lake at Kaba, 1971, 1976, and 1978. Courtesy of VSI.

Information Contacts: A. Sudradjat, VSI; Suparto S., Java and Sumatra Observatory, VSI.

November 2000 (BGVN 25:11) Cite this Report

Explosions and light gray ash

This report covers activity at Kaba documented by the Volcanological Survey of Indonesia (VSI) during August 2000. Deep volcanic earthquakes dominated seismicity during the second week of August. On 17 August seismographs recorded harmonic tremor with a maximum amplitude of 14 mm. Visual observations were hindered by clouds around the summit until the third week of the month. During 22-28 August, conditions were clear and a light gray ash plume rose 200 m above the summit. Five small explosion earthquakes were registered on 26-27 August, corresponding to the same number of observed ash emissions. By the end of August, the number of deep volcanic earthquakes decreased. Kaba remained at a hazard status of 2 (on a scale of 1-4) throughout the month.

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

September 2009 (BGVN 34:09) Cite this Report

Increased seismicity and whitish vapor emissions

Deep volcanic earthquakes, seismic tremor, and five small explosions with corresponding ash emission were reported from Kaba in August 2000 (BGVN 25:11). Since then, Kaba has been quiet, but even in its normal state it almost always emits whitish plumes 25-100 m high.

On 20 October 2009, the Center of Volcanology and Geological Hazard Mitigation (CVGHM) reported that seismic activity from Kaba increased in August and remained elevated into September and October. Inflation was also detected. When weather permitted, diffuse white plumes were seen rising ~ 25-50 m above the summit crater complex and drifting E. Based on the deformation and increased seismicity, CVGHM raised the Alert Level to 2 (on a scale of 1-4).

From January through August 2009, the frequency of deep volcanic earthquakes averaged 85 events per month, but in August the number of events rose to 257 per month. During August-September, whitish plumes remained similar to September-October. In September seismicity fluctuated but tended to increase. Earthquakes and total tremors recorded at Kaba's monitoring post are shown in table 2.

Table 2. Summary of Kaba seismic data recorded during 12 September-20 October 2009. Courtesy of CVGHM.

Deformation measurements taken using an EDM (electronic distance measurement) method were as follows: Biring station, shorter by 10 cm; Voelsang station, longer by 0.4 cm; and Kaba station, shorter by 2 cm.

Measurements of the crater water temperature on 15 October showed a reading of 72°C, with a pH of 3.24. The sulfurous and associated solfatara areas recorded a temperature of around 106-107°C. There was no other activity in the area of the crater.

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://vsi.esdm.go.id/).