Geological Survey of India
May 2015 record on Pulsative eruption of Barren Island Volcano
Barren Island volcano, the only active volcano in India, is related to subduction of Indian
plate beneath the overriding South East Asian plate. About sixty such potentially active
volcanoes lie along the SE Asian volcanic rim1. Barren Island volcano (120 17’ N: 930 51’ E),
covering an area of approximately 10 sq km is located in Andaman Sea. Barren Island
volcano has ejected lava and pyroclastic materials in four distinct phases with various
intensities in the past
. During 1991-2006, eruption was episodic in nature. Three
2,3,4,5
different phases of eruptions in 1991, 1994-95 and 2005-09 were recorded. These eruptions
have modified the crater morphology Barren Island volcano.
This note is prepared on the basis of observations made onboard Geological Survey of
India research vessel Samudra Ratnakar during Cruise SR-013, in the month of May, 2015.
The Survey lines were passing close to the Barren Island and on 14th May 2015 and 31st May
2015, the authors got an opportunity to observe the eruption. Distinct difference in the
volume of ejection, colour and height of volcanic material (gas, vapour and ash) was noticed
between 14th and 31st May 2015.
On 14th May 2015 (at 10:30am) Mushroom shaped volcanic cloud of around 200-300
m height with dark to light grey colour was observed (Figure 1). Eruption was pulsative in
nature with thick columns of ash, ejecting vertically to sub vertically. In eight minutes two
pulses of ash and other volcanic material were ejected to a height of around 300 to 400 m
with an interval of 1 minute 44 seconds were observed (Figure-2).
The eruption on 31st May 2015 was mostly light grey to grey in colour (Figure 3) and
the duration of eruption was 20-25 seconds only. Even though the pulse rate for both the
phases were same, the pulse interval for latter one was long, varying from 4 to 5 minutes
and height of volcanic ash eruption was around 50 to 100 m. The ash cover over north
eastern portion of the Island indicates the effect of south western monsoon linked with
atmospheric circulation pattern over Andaman Sea prevailed during the month of May
(Figure 4).
The increased intensity of eruption (both in volume and height) on 14 th of May 2015
might be related to 5.4 magnitude earthquake of 12th May 2015 that affected Nepal,
Afghanistan and Indonesia. This deep crustal earthquake along the subduction zone might
have generated the energy waves, which affected the magma main conduit of Barren Island
volcano, releasing higher amount of trapped ash, gas and vapour. This could be the possible
Sachin Kumar Tripathi*, M. Chaturvedi and R. K. Joshi
Marine and Coastal Survey Division, Eastern Region
*Corresponding email: [email protected]
Geological Survey of India
reason for the variation in height and duration. This note is a mere conjecture based on the
visual observation only, however detailed investigation in this regard is required.
Figure-1: Photographs were taken on 14th May 2015, just after the Major earthquake in Nepal, Afghanistan and
Indonesia.
Sachin Kumar Tripathi*, M. Chaturvedi and R. K. Joshi
Marine and Coastal Survey Division, Eastern Region
*Corresponding email: [email protected]
Geological Survey of India
Figure-2: Photographs illustrating the pulsation rate noticed during 14th May 2015; start of single pulse (a) and
end of the same (b).
Figure-3: Photographs were taken on 31st May 2015
Sachin Kumar Tripathi*, M. Chaturvedi and R. K. Joshi
Marine and Coastal Survey Division, Eastern Region
*Corresponding email: [email protected]
Geological Survey of India
Figure-4: Photographs showing the grey colour ash cover over the NE portion of the Barren Island due the
effect of SW monsoon wind.
Reference:
1. Shanker, R., Halder, D., Absar, A., Chakraborty, S.C., Pictorial monograph of the Barren Island
volcano, the lone active volcano in the Indian subcontinent. Geological Survey of India, 2001, 67,
87 (Special Publication).
2. Sanjeev, R. 2011, Barren Volcano- A Pictorial Journey From Recorded Past To Observed Recent
Part-I Earth Science India, Open Access e-Journal, Popular Issue, IV (III), July, 2011; (URL:
www.earthscienceindia.info)
3. [For history http://dx.doi.org/10.5479/si.GVP.BGVN201407-260010,
4.
http://www.volcanodiscovery.com/ volcano-activity/news /52756/Volcanic-activity-worldwide27-Apr-2015
5. Darwin Volcanic Ash Advisory Centre (VAAC)]
Sachin Kumar Tripathi*, M. Chaturvedi and R. K. Joshi
Marine and Coastal Survey Division, Eastern Region
*Corresponding email: [email protected]