Batu Tara Volcano


Batu Tara volcano forms the Island of Komba which lies about 50km off the north coast of Lembata Island, one of the Lesser Sunda Islands belonging to Indonesia. The volcano is the most northeasterly volcano in the Flores-Pantar sector of the Sunda Arc which also includes the active Paluweh volcano. The associated Sunda Trench, where the Indian-Australian plate subducts under the southeastern extension of the Eurasian plate, lies south of the Arc.

Historical activity has been reported for the periods 1847-1852 and 2006-2012 (continuing). The volcano generally erupts explosively from a central vent perched near the top of what appears to be an eastward-oriented collapse feature similar to the Sciara del Fuoco at Stromboli volcano. The vent lies about 100 meters below the summit of the volcano which is 748 meters high. If the underwater part of the ediface is included, the volcano is about 2500 meters high. The lava from Batu Tara is leucite-rich and contains a high content of potassium oxide (3-9% by weight), so that the volcano is classified as ultrapotassic. The silicate content of 45-54%, so that the rocks can be classified as basaltic / trachybasaltic to andesitic. A detailed analysis of the lithology of Batu Tara is found in two scientific publications (Bergen et al. 1992. Lithos 28, p.261-282; Stolz et al., 1988. Contrib. Mineral. Petrol. 98, p.374-389).

The potassic nature of the lavas is considered derived from mixing of several different source components, including potassium-enriched mantle and subducted crustal material. Interestingly, it has been shown that three sectors within the Arc show eastward trends of increasing potassium-content, stopping abruptly at leucite-bearing volcanoes at the eastern end of the sector (Wheller et al. 1987. J. Volc. Geotherm. Res. 32, p.137-160). These are Muriah (W. Java Sector), Sangenges / Soromundi (Bali Sector) and Batu Tara (Flores Sector).

Explosive eruption producing dense ash cloud and volcanic bombs, Batu Tara volcano, Indonesia Nighttime explosive eruption producing dense hail of volcanic bombs, Batu Tara volcano, Indonesia

Eruption with dense ash cloud

Nighttime eruption

Lava flows have been reported, yet the reliability of these reports is questionable since sustained incandescent rockfalls were described as lava flows by the guides. At one stage during our observations, rockfall activity was almost continuous and appeared to be the result of sustained extrusion from the plug sitting on the active vent(s). This activity was accompanied by increasingly violent eruptions.
Most eruptions during the observation period involved propulsion of volcanic bombs from the crater associated with the formation of relatively light-coloured plumes with little ash content. Several eruptions were however observed associated with much darker and more dense ash clouds. It is not clear if these come from the same vent as the other eruption type. None of the eruptions during the observation period propelled volcanic bombs directly into the sea although bombs were regularly thrown out of the scarp onto the higher flanks of the volcano to either side.
Batu Tara erupts basaltic lavas with high potassium contents. These differ substantially from the more silicic lavas produced by the volcanoes of Flores and Lembata islands to the south which constitute part of the main volcanic arc in the region associated with the subduction zone to the south of these islands.
Due to its remote location, the current activity of the volcano presents no hazard to local populations, however ash clouds from a larger eruption may interfere with major air traffic routes passing through the area. The potential for flank failures of the steep-sided ediface, as have evidently occurred in the past does however entail the risk of tsunamigenesis. The exact level of risk to nearby coastlines does not appear to have been modelled.

Structure of Island

Komba Island, Batu Tara volcano Dyke in flank of Batu Tara volcano Rocks coast and dyke in flank of Batu Tara volcano

Approaching Island from SW

Dyke feature in cliff

Further Dyke structure

Coastline of Batu Tara volcano with eruption Rocky beach at foot of Batu Tara volcano with eruption Rock units, Batu Tara volcano

View of crater area from nearby beach

View showing rocky coastline at beach

Massive rock structure overlying slightly coloured weathered rocks of older age (right of crater)

Active vent of Batu Tara volcano View of small eruption of Batu Tara from boat View of small ash-rich eruption of Batu Tara from boat

View of crater from boat with and without eruptions


Daytime Eruptions

Explosive eruption producing dense ash cloud and volcanic bombs, Batu Tara volcano, Indonesia Explosive eruption producing dense ash cloud and volcanic bombs, Batu Tara volcano, Indonesia, portrait orientation Explosive eruption producing dense ash cloud and volcanic bombs, Batu Tara volcano, Indonesia

Powerful ash-rich explosive eruption


Explosive eruption producing dark grey ash cloud and volcanic bombs, Batu Tara volcano, Indonesia Explosive eruption, Batu Tara volcano, Indonesia Explosive eruption of Batu Tara volcano, Indonesia

Powerful ash-rich explosive eruption


Gas eruption with low ash content, Batu Tara volcano Bidirectional gas eruption with low ash content, Batu Tara volcano

Gas eruption with low ash content

Bidirectional gas eruption with little ash

Gas eruption with low ash content, Batu Tara volcano Evening eruption against light, Batu Tara volcano

Eruption

Evening eruption


Eruption of ash cloud, Batu Tara Volcano Eruption of ash cloud, Batu Tara Volcano, Vertical orientation Eruption of wide ash cloud, Batu Tara Volcano

Further eruptions


Eruption of wide ash cloud with little ash content, Batu Tara Volcano Eruption of ash cloud accompanied by jet-like noise, Batu Tara Volcano Eruption of light ash cloud, Batu Tara Volcano

Further eruptions


Eruption of ash cloud with ash-rich and ash-poor components, Batu Tara Volcano Eruption of ash clouds with different grey shades, Batu Tara Volcano Eruption of ash cloud in reddish morning light, Batu Tara Volcano

Bidirectional eruption with differing ash contents

Eruption with ash-rich and less ash-rich clouds

Eruption in morning light

Nighttime Eruptions

Glowing volcanic bombs at dusk, Batu Tara volcano Glowing volcanic bombs, Batu Tara volcano

As light levels fall, incandescence of bombs becomes visible

Longer exposures start to show paths of glowing bombs

Ash cloud lit up by eruption below, Batu Tara volcano View of flank of Batu Tara in moonlight with eruption

Small nightime eruption

Small nighttime eruption with rockfalls to sea

Small Strombolian eruption, Batu Tara Small Strombolian eruption, Batu Tara

Small explosive eruption frequently observed during visit

Small eruption directing bombs to one side of crater

Powerful nighttime explosion blasts volcanic bombs out of vent of Batu Tara volcano Nighttime explosive eruption producing dense hail of volcanic bombs, Batu Tara volcano, Indonesia

Start of powerful explosive eruption

Larger eruption

Eruption with dense hail of small volcanic bombs, Batu Tara volcano, Indonesia Nighttime explosive eruption producing dense hail of volcanic bombs, Batu Tara volcano, Indonesia

Eruption with dense hail of small volcanic bombs

Powerful eruption throwing bombs of various sizes

Ash cloud illuminated by lava, Batu Tara Volcano Nighttime strombolian eruption of Batu Tara volcano

Image showing impact of bombs from larger eruption

Eruption with dense hail of small volcanic bombs

Nighttime explosive eruption producing dense hail of volcanic bombs, Batu Tara volcano, Indonesia Nighttime explosive eruption producing dense hail of volcanic bombs, Batu Tara volcano, Indonesia

Larger eruption

Larger eruption

Close-up of strombolian eruption, Batu Tara volcano, Indonesia Close-up of strombolian eruption, Batu Tara volcano, Indonesia

Close-up of smaller eruption

Close-up of smaller eruption

Nighttime eruption producing ash cloud, Batu Tara volcano, Indonesia Extrusive activity, Batu Tara volcano, Indonesia

Glowing rocks cascading down to sea

Extrusion episode from plug on top of conduit

Close-up of extrusive activity producing continuous incandescent rockfalls, Batu Tara volcano, Indonesia Close-up of extrusive activity producing continuous incandescent rockfalls, Batu Tara volcano, Komba Island, Indonesia

Close-up of extrusion phase from plug on conduit

Close-up of extrusion phase from plug on conduit


Spectacular Nighttime Eruption Video


The video shows a powerful explosive eruption at Batu Tara, filmed only using the light from the full moon. The video captures the extrusion phase where incandescent material squeezed up through the conduit breaks out of the side of the dome, leading to glowing rocks descending the flank of the volcano. The ash thrown up by these rockfalls is illuminated by the glowing fragments. The glowing intensified and after about 27 seconds the main eruption starts. The powerful blast throws glowing material high in the air, after which it can be seen impacting and breaking up into hundreds of glowing fragments on the flanks of the volcano.




SCREENSHOTS:


Detailed View of Crater Structure


Wide-angle view of eruption, Batu Tara volcano, Indonesia Upper part of Batu Tara volcano, Indonesia

Flank below crater with debris apron

Upper part of ediface

Close-up of crater and surrounding flanks, Batu Tara volcano, Indonesia Close-up of crater and flank below, Batu Tara volcano, Indonesia

Crater region

Crater and remnants of viscous lava flows below

Close-up of crater, Batu Tara volcano, Indonesia Close-up of vent, Batu Tara volcano, Indonesia

Crater and remnants of viscous lava flows below (closer)

Close-up of vent

Visitor Information


Komba Island is remote and provides few beaches suitable for landing. The beaches offering a view of the active crater are rocky and can only be safely landed on when sea conditions allow. The island is steep-sided and densely vegetated, making climbing to the summit area almost impossible.

Tuna boat in Larantuka harbour Sailing towards batu tara volcano

Tuna boat picking up group in Larantuka harbour

Approaching Batu Tara

Camp on Komba island with tuna fishing boat Camp on Komba island

Beach camp on Batu Tara (Komba Island)

Canoe for landing with camp behind

Tuna fishing boats may be chartered from Larantuka at the eastern tip of Flores, yet the crew may be reluctant to approach the volcano and prefer to concentrate on fishing, which may cause conflicts with visitors. The fishing boats are single-engined. A satellite phone should be taken for additional safety in case of engine failure, since other maritime traffic is scarce in the area.

Rockfalls may occur at any point on the island. A large rock tumbled into the sea less than 50 meters from our viewing position. Debris fans at the end of gulleys should be particularly avoided, especially during rainfall.


Photovolcanica Full Index