barren volcanobarren volcano---- a pictorial journey from recorded past ......

Open Access e-Journal

Earth Science India- www.earthscienceindia.info

Popular Issue, IV (III), July, 2011

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Barren VolcanoBarren VolcanoBarren VolcanoBarren Volcano---- A Pictorial Journey From Recorded Past To A Pictorial Journey From Recorded Past To A Pictorial Journey From Recorded Past To A Pictorial Journey From Recorded Past To Observed Recent Observed Recent Observed Recent Observed Recent PartPartPartPart----IIII

Sanjeev Raghav

Within a week, we set out for another expedition to witness the fury of Barren Within a week, we set out for another expedition to witness the fury of Barren Within a week, we set out for another expedition to witness the fury of Barren Within a week, we set out for another expedition to witness the fury of Barren on 13on 13on 13on 13thththth June, 2005 on ‘INS Teresa’………………. Fortunately, the wind was south June, 2005 on ‘INS Teresa’………………. Fortunately, the wind was south June, 2005 on ‘INS Teresa’………………. Fortunately, the wind was south June, 2005 on ‘INS Teresa’………………. Fortunately, the wind was south wewewewesterly and we could negotiate our track till the base of secondary (parasite) sterly and we could negotiate our track till the base of secondary (parasite) sterly and we could negotiate our track till the base of secondary (parasite) sterly and we could negotiate our track till the base of secondary (parasite) vent on the southvent on the southvent on the southvent on the south----western slope of the main cinder cone to collect the fresh lava western slope of the main cinder cone to collect the fresh lava western slope of the main cinder cone to collect the fresh lava western slope of the main cinder cone to collect the fresh lava samples where temperature of the gas was recorded as high as ~200samples where temperature of the gas was recorded as high as ~200samples where temperature of the gas was recorded as high as ~200samples where temperature of the gas was recorded as high as ~2000000C. Red hot C. Red hot C. Red hot C. Red hot lava was seen peepilava was seen peepilava was seen peepilava was seen peeping through the Devil’s eye. This was my fourth visit to ng through the Devil’s eye. This was my fourth visit to ng through the Devil’s eye. This was my fourth visit to ng through the Devil’s eye. This was my fourth visit to Barren Island since 2001. Barren Island since 2001. Barren Island since 2001. Barren Island since 2001.

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th February, 2005, I was right on the top of the northern edge of the main cinder cone of the

quiescent Barren Volcano (BV) and watching the gaseous fumes emanating from its south western

periphery. Suddenly a dreadful thought flashed in my mind- If Barren Erupts Now!! That day I had

returned to the base with minor injuries negotiating the steep outer slope of the pyroclastic cinder

cone laden with loose ash, lapilli, and boulders ejected from previous explosions. Barely 100 days

had passed, when I learned from the media on 28th May, 2005 that Barren has erupted again. I was

shaken and my hair stood on its end. Within a week, we set out for another expedition to witness the

fury of Barren on 13th June, 2005 on ‘INS Teresa’. Light shades of gas and vapour column emanating

from the BV was visible from as far as 20 km. As we approached nearer, the fury of BV became more

visible. Periodic eruptions at 2-3 minute interval with the sound of exploding cannon could be heard

from as far as 7 to 8 km. The vent of this eruption was situated on the southern face of the cinder

cone. Possibly this was the same location from which I have seen increased emanation of gas and

vapour on 16th February, 2005. Our team landed on the Barren from the lone landing site on the NW

face and was greeted by light tremors on the island caused by the periodic violent eruptions.

Fortunately, the wind was south westerly and we could negotiate our track till the base of secondary

(parasite) vent on the south-western slope of the main cinder cone to collect the fresh lava samples

where temperature of the gas was recorded as high as ~2000C. Red hot lava was seen peeping through

the Devil’s eye. This was my fourth visit to Barren Island since 2001.

My journey to the Barren Volcano started from 18th

April, 2001, when I first stepped on

the Barren Island (being part of a multi-disciplinary scientific team of Geological Survey of India)

to study the Barren Volcano. Since then, I have visited Barren Island several times for various

scientific expeditions by GSI with the latest encounter being on 6th January, 2011 and have witnessed

its transformation from a sleeping giant to a roaring and fuming demon. So, when I received a request

for a popular article on geology for the e-journal of the Society of Earth Sciences, immediately I

thought of sharing my decade old association with Barren Volcano with everyone. In the following

chapters, I will take the readers on a pictorial journey of the Barren volcano which is divided into two

parts. Part- I deals with various heads like, location and approach, Tectonic and geomorphic set up,

Pre-historic and historical records of volcanic history of BI. Part– II deals with the various expeditions

carried out by the Geological survey of India during the eruptive 1991-1995 phase, quiescent 1996 to

February 2005 phase and the latest but most active phase from May 2005 to 2011, which has

superimposed all the earlier morphology of this lone active volcanic island of India.




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(a)

(b)

(c)

Fig.1a,1b,1c: Quiescent Barren Volcano (BV) in the Andaman Sea: Observed on 18th

April

2001 (Top), Resurgent BV on 13th

June 2005 (Middle) and 11th

March 2006 BV (Lower)

with massive lava flow meeting the sea and superimposing all the previous deposits on the

western side.




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Fig.2: An aerial view of the top of the main cider cone probably taken in 2004 showing

remains of 1991 and 1994 - 95 vent. This was exactly the shape of the top of the cinder cone

which the author observed when he climbed atop in February, 2005. Brown arrow shows the

path of ascend from northern side and mark 2005 shows the location where he climbed on

16th

February, 2005. Note the dangerously steep slope of the cone top laden with white pasty

material which was overlying the loose pyroclastic cone and ground temperature was warmer

than air temperature of ~350C.

Fig. 3a & 3b: Author (standing on the left) at the top of main cinder cone of Barren Volcano

on 16th

February, 2005. (A: Inner slope of the 1994 - 1995 cinder cone; B: Outer slope of the

cinder cone; C: Inner side of southern prehistoric caldera wall; D: 1994 - 1995 eruption lava

flow towards the western valley, E: Inner slope of northern wall of prehistoric volcanics

covered by thick ash flow from successive historical eruptions till February, 2005. Photo on

the right, taken from the top of the cone, showing tracking path from the northern slope.




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Introducing Barren Volcano

How to approach Barren Volcano: Barren Island (Fig.4) can be approached through special tourist

cruises arranged by Andaman administration but tourists are not allowed to set their foot on the island.

Indian Navy and Coast Guard ships deployed for safeguarding the islands and Indian waters regularly

ferry around this island. A third category of visitors on these islands are geoscientists who visit these

islands occasionally for various scientific expeditions either on the Navy and Coast Guard ships or

with the help of institutional research vessels like R. V. Samudra Manthan (RVSM) of Geological

Survey of India. Some tour operators also provide fishing opportunity around the BI on small boats;

however, they can’t land on the BI. Hence, apart from scientists, administration and navy personnel,

Barren Island are not approachable by common man or tourists because of cost factor and

administrative restrictions due to security reasons.

Fig. 4: Location of Barren Island in the Andaman Sea. BI image not to the scale.

Location and Tectonic set up of Barren Volcano: Barren Island (12° 17’ N : 93° 51’ 30” E) is

located in the Andaman Sea within the exclusive economic zone (EEZ) of India as one of the most

easterly of the Andaman group of Islands. It is situated 135 Km north east of Port Blair (capital of the

Indian Union Territory of Andaman and Nicobar Islands). This volcanic island is the lone confirmed

active volcano of the Indian sub-continent on one of the most mobile zones of earth. Geologically,

this volcanic island stands in the midst of a volcanic belt on the edge of the Indian and Burmese

tectonic plates. Narcondum Island is another aerially exposed extinct volcano on the northern

extension of this volcanic belt, besides many under-water volcanoes like Alcock and Sewell sea

mounds in the Andaman Sea. Tectonically, Barren Island (BI) is a subduction - related volcanic island

lying in the Andaman Sea (north-eastern Indian Ocean). The Barren Island volcano represents an unit

of Indo-Indonesian volcanic chain, the origin of which is believed to be due to the east and north-

eastward oblique subduction of Indian ocean lithosphere below SE Asian plate with an easterly




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dipping Benioff zone in the Burma–Java subduction complex (Fig.5). This Miocene-Recent volcanic

arc developed due to this subduction extends from the presently active volcano in Indonesia through

BI and Narcondam volcano in the Andaman sea to the late Tertiary extinct volcanoes of Myanmar

(Haldar and Luhr, 2003). The Andaman-Java Benioff zone dips eastward down to a depth of about

180 km below the Andaman Arc. Analysis of teleseismic data in this region suggest that an

intermediate seismic gap exists between depth range of 90 and 110 km in this Benioff zone. This

seismic gap is interpreted to indicate the partial melting zone. An east dipping benioff zone exists

below the BI (Dasgupta and Mukhopadhyaa, 1997). Deep crustal tectonism which is presently very

active in the region might have manifested itself in the form of BI volcanism.

Fig.5: Location and tectonic set up of Barren volcanic island with respect to convergence

boundary (white line) between Indian Plate and the Eurasian Plate. Labeled volcanoes are

Barren Island, Narcondam (N), Popa (P) and the Singu Plateau (SP) in the Myanmar. Other

abbreviations are the Burma Sub-Plate (BP) of the Eurasian Plate, Irrawaddy Delta (ID),

Andaman Island (AI), Grand Nicobar Island (GNI), Andaman Ridge (AR), Ninety East Ridge

(NER). The location of the 26 December 2004 Sumatran earthquake (Mw 9.3) is marked by a

white dot. The large white arrow shows the NNE relative-motion vector of ~60mm/yr for the

Indian Plate and the Eurasian Plate west of Sumatra. White triangles denote active volcanoes

along Indonesia-Sumatra subduction zone. (Image Source: Luhr and Haldar, 2006)




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Barren Volcano with respect to other volcanoes on Earth: Presently there are about 500 active

volcanoes distributed over the surface of the earth of which about 50 show submarine eruptions.

Seventy-five percent of these lie on the ring of fire - a band running around the periphery of the

Pacific Ocean, along the coast of North and South America and down to the coast of Asia through

Kamchatka, Japan up to New Zealand. Another twenty five percent is located in southeast Asia,

mostly in the Philippines, Indonesia and Papua-New Guinea including the Barren Island volcano in

the Andaman Sea (Fig.6).

Fig. 6: Map showing the geographical location of the major active volcanoes on the Earth

with location of the Barren Island (BI) volcano and ‘Ring of Fire’ .

Flora and Fauna on the Barren Island: True to its name, it is a barren area uninhabited by humans,

though it has a small population of feral goats (Fig.7a). These animals were left in 1891 by the station

steamer from Port Blair (Kloss, 1902) and they are so free from fear and unsuspecting that when we

land on Barren Island, they stare at us as if we have come from another planet. Other mammals, apart

from goats, were variety of rats with range of colours, resembling various shades of volcanic dust and

lava flow, from brown to black. Amongst birds, Indian cuckoo (Koel), parrots and fruit bats are

common. Sea creatures like crabs are found roaming on the small beaches and rocky outcrops meeting

the sea water. Outer and inner slopes of the caldera wall are full of lush green vegetation with tall

trees and shrubs which are regularly destroyed during successive eruptions and thick ash fall (Fig.7b)

Geomorphology of Barren Island: Geologically, Barren volcano can be classified as startovolcano

with pyroclastic cone. All the historical and recent eruptions (1787 and after) are confined within and

around an active polygenetic cinder cone in a 2-km wide caldera that is formed by the collapse of a

primitive cone of a stratovolcano. The remnant of the primitive volcanic cone forms a precipitous

cliff around the island (commonly referred to as caldera wall), with a break towards the west (Fig.8).




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Fig.7a & 7b: Feral goats encountered on Barren Island on 04-01-2011. Thick vegetation on

the outer slope of the northern caldera rim submerged during 2010 lava flow (white arrow).

The highest elevation on the island was that of the southern side of the caldera wall measuring 354

meters. The active cinder cone measured 265m when I climbed atop in 2005. Since then, it is

increasing in height with successive explosion and has reached almost 500m as observed in January,

2011. The island is 3 km in diameter with a total surface area of 10 km² and has a subaerial volume of

only ~1.3 km3.

Most of the primitive volcano is underwater. Rising from a depth of ~2300 m on the

Andaman Sea floor, BI has a submarine volume estimated at ~400 km3. At present, the main cinder

cone of the erupting Barren volcano can only be approached from the western flank of the Barren

Island because all other sides are occupied by thickly vegetated high (> 200m) caldera wall which

gives the conical shape to this island and reaches a maximum elevation of 355 m on its southern

flank. The main cinder cone which was recorded to be ~ 235m in height in 2005 has gained height

post- 2005 eruptions and was estimated to be around ~500m in January, 2011. Lava flows and

pyroclasts fill much of the caldera floor and have reached the sea along the western coast during

eruptions in the 19th century, 20th century and 21st century and also on the northern side during 2010.

The diameter of the base of the volcano on the sea floor is 16-19 km. The slope of the underwater part

of the volcanic mount varies from 1 in 3 to 1 in 23 in different directions. In general, northern and

eastern slope is steeper and smoother as compared to the western and southern slopes. Signatures of

subsidiary cone and under water lava flow have also been recorded on the south-western slope of the

underwater Barren Island mound

Eruption history of Barren Volcano: After the first recorded eruption in 1787, further eruptions

were recorded in 1789, 1795, 1803–04 and 1852. After nearly one and half century of dormancy, the

island had another eruption in 1991 that lasted six months and caused considerable damage. There

were eruptions in 1994–95 and 2005–07, the latter being considered to be linked to the 2004 Indian

Ocean earthquake.




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Fig.8: Aerial view from the NW side (left image) of the active Barren volcano and front view

from the west side (right) of the quiescent Barren volcano depicting the geomorphology of

volcanic island. Present main pyroclastic cinder cone is occupying the centre of caldera

formed due to the collapse of prehistoric volcano, exposed aerially during late Pleistocene

(?). The caldera rim is breached on the western side through which lava flow from successive

eruption flows down (black colour) to the water front.

The most recent eruption started in May 2008 and still continues with episodes of increased eruption.

This Pictorial journey, showing various faces of Barren Volcano has been compiled from Kloss,

1902, Ravi Shanker et al. (2001) and references therein like Hobday and Mallet (1885), Ball (1893),

Mallet (1895), Washington (1924), Raina (1987) and Haldar et al. (1992a,b, 1999), Haldar and Luhr

(2003), Luhr and Haldar (2006), Shrivastava (2002), Raghav (2005), Bandyopadhyaya et al. (2006),

Pal et al. (2006, 2010), various reports from the Bulletin of the Global Volcanism Network

(Smithsonian Institution, 1991, 1992, 1993,1995, 2011), various web sites, aerial photographs

courtesy Indian Navy’s Coast Guard station at Port Blair and personal collection of photographs by

the author collected during various expeditions from 2001 to 2011.

Pre-Historic Eruption Records

The present Barren Island came into existence through a submarine volcanic eruption during

Pliocene-Pleistocene (assumed, not exactly dated). A reconstruction of the most of the caldera rim

which has an average slope of 30-350 and a diameter of 3.5 km suggests that the height of the

primitive cone was about 1100 m. It is assumed that some time during late Pleistocene or early

Holocene (?), upper part of this volcanic cone was blown off by some high intensity paroxysmal




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eruption leaving behind a big relict cauldron (Shankar et al., 2001). This submarine eruption produced

major landform of Barren Volcano with an estimated submarine volume of 390 sq km and the sub

aerial volume of 1.3 sq km (Luhr and Haldar, 2006). The culmination of this eruption was marked by

a sub-aerial eruption producing a caldera (Fig.8) 2km diameter in the central part (Shanker et al.,

2001). The interstratified beds of the pyroclastics of basaltic to andesitic composition are now

preserved as the caldera wall. Agglomerate, massive beds, current bedding, graded bedding and

penecontemporaneous structures from this bedded sequence suggest that the bedded sequence was the

product of subaqueous pyroclastic flow deposit. These deposits have recently also been described as

the products of waves, pyroclastic fall and surge deposits (Sheth et al., 2009).

Fig.9: Pre–historic volcanics (pyroclastic and lava flow) exposed on the NW side of the

caldera wall is gently dipping towards NE. The lone landing site from historic time till 2005

is seen on the NW corner of the image. Lava flow during historical times (?) is seen exposed

directly against the sea water along the entire western face of the breached caldera wall. The

1991-1995 flow (dark flow towards the sea but not reaching the water front) and 1995 vent is

also shown. The prehistoric caldera wall is also covered with shrubs and long grass. Semi-

consolidated and southerly dipping pyroclasts (ash + boulders) deposited aerially during the

historic times is unconfirmably overlying the NE dipping Pre-historic caldera rim.




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Fig. 10a & 10b: Inter-bedded agglomerate bed, finely laminated tuff and lava flow of

varying thickness and colour suggesting episodic nature of pyroclastic and lava flow

deposited under water and sub - aerial conditions during the Plio-Piestocene (?) evolution of

Barren Volcano, now exposed above water as volcanic island. Left image is from inner side

of southern caldera wall and right image is from the inner side of northern caldera wall. Also

seen is the recent ash flow abutting against the vertical scarp face of the collapsed caldera.

The Pre-historic thick massive lava flow interbedded with agglomeratic flows (Fig. 10a, 10b)

of different thickness ranging from 50 cm to 5 m are result of both Hawaiian type and

Strombolian eruptions in succession. Nine such eruptive pulses were identified by Shankar et

al. (2001) during 1991–1995 expeditions.

Historical Eruption Records

On the basis of tephrochronology, it is suggested that Barren volcano became active during 8010 ±

100 BC. The first historical record indicate that BI erupted on 12th May 1787 with Volcanic

Explosivity Index (VEI) of magnitude ~2 with an explosive eruption

(http://dsc.nrsc.gov.in/DSC/Others/ODEventsTable.jsp#) from the central cone in the middle of the

pre-historic caldera. The historical records of explosive eruption from central vent with an VEI

magnitude of ~ 2 were recorded on 24th March 1789, 20-21

st December 1795 and with eruption and

lava flow from November 1803 – 1804 (Colebrook (1787) give the earliest report of columns of

smoke, gas and steam rising from the crater.




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Fig. 11a & 11b: Moderately dipping caldera wall of finely laminated tuff beds (left) and

thick inter-bedded pyroclasts and lava flow (right) suggests underwater/sub aerial deposition

through successive eruption during Pleistocene (?). The very thin to thickly-laminated ash

bed, overlying the pre-historic flow indicate aeolian deposition during historical times which

continues till date.

Fig.12: About 100 m thick section of pyroclasts exposed on the inner side of prehistoric

northern caldera wall.




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Fig.13: Pre-historical pyroclastic and lava flow showing guarded bedding and

penecontemporaneous deformation developed due to gravity collapse of ejected pyroclastic

bombs from the explosive cinder cone.

Fig. 14: Pyroclast flow showing cross bedding structure in the pre – historic volcanics

exposed on the inner side of the southern crater wall.




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Fig.15: Flow and slump structures of the pre – historic volcanic deposits suggestive of under-

water deposition of pyroclasts and lava flow.

Followed by Capt. Blair (after whom the capital of Andaman and Nicobar Island is named as ‘Port

Blair’) in 1789 and 1795 when he passed near the island and found enormous volumes of smoke

with frequent showers of red-hot stones as big as three to four tons and which had been thrown some

hundred yards past the foot of the cone and also recorded two or three such eruptions while grazing

through the BI. The distant parts of the island were thinly covered with withered shrubs and blasted

trees. A few years letter Horsburgh recorded an explosion every ten minutes and a fire of considerable

extent burning on the eastern side of the crater. Records of eruption have been also recorded by Von

Buch (1825), Capt. Miller (1834).

Hence, it can be safely assumed that the second cycle of eruption was sub-aerial explosive with

Strombolian style during 1787-1832 period. In the central part of the relict cauldron, a cinder cone of

305 m height with a 60m diameter crater was produced. From the crater and vents, initially a huge

amount of blocks, and scoria (cinder and ash) of basaltic composition had been ejected and deposited

as lava debris at initial stage. Subsequently, during the 1803-1832 period, the ‘aa’ basaltic lava was

pouring out from the vents.

Thereafter, for thirty years the volcanic activity seems to have decreased, when only volumes of white

smoke and no flames were seen. Dr. Mount and Dr. Leibig, who visited the island within a few

months of each other in 1857, write respectively of volumes of dark smoke and clouds of hot , watery

vapour. In 1866, a whitish vapour was emitted from several deep fissures (Boscowitz, 1866). Around

1890, steam was seen to be issuing at the top from a sulphur- bed, which was liquid and pasty and a

new jet was coming from a lump on the sloping side of the cone. While recounting all the above

observations in his memoir in 1902, Capt. Kloss mentions that in the 2nd

week of January 1901, when

he landed on the island, the sole evidence of activity observed was deposition of sulphur and escape

of steam which often condensed on the surface rocks.




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Fig.16: Alternate bands of pyroclast and lava flow in the pre– historic crater wall with tree

root penetrating through cracks. Section from the inner slope of the southern caldera wall.




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Fig.17: Earliest drawing of BI volcano from the west showing the start of the 1787–1832

activity, after Colebrooke (1787). Fig. 1.16 from Shanker et al. (2001).

Fig.18: Capt. Blair’s view of Barren Volcano, 1789 Fig. 1.17 from Shanker et al. (2001). The

ash flow direction suggest that ship observations were taken during summer and rainy

seasons (March to September) when south westerly winds blow over the Andaman Sea.

Kloss (1902) in his memoir further writes that “ a rough wall of lava about a dozen feet high stretches

across the landing site, among the stones and boulders of the shore, was found, below high water

mark, a little stream of fresh water trickling to the sea; it is the only water on the island and at that

time was at a temperature of 97.50F*” (and also mentions with an asterix* from earlier records that the

temperature in 1891 was 103.50F, 1400F in 1873, 158-1630F in 1806 and recounts that Dr. Adam’s in

1831 found that 100 yards from shore water was nearly boiling, the stones and rocks on shore exposed

at low tide were smoking and hissing and the water was boiling all around them. Dr. Mount who

landed on BI in 1857 found ‘a natural boiling spring, the waters so extremely hot that they rendered

the sea in the immediate neighbourhood warm enough to roast crabs in their shells’. All these records

suggest that there was an active phase of volcanism between 1787 to 1857. The explosive activity

stared diminishing after 1860 with pyroclast and lava flow being replaced by an increase in fumerolic

activity till 1890.




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Fig.19: Sketch of Barren Volcano, 1886 (Arnold Boscowitz) Fig. 1.19 from Shanker et al.

(2001). The sketch suggest the wind direction was north to south indicating that ship

observations were taken during winter season (November-February) when north easterly

wind blows over the Andaman Sea.

When Capt. Kloss landed on the island in January 1901, he found a cessation in all these activities

and writes “From the landing place (the lone landing site in the NW corner of the island till June 2005

which was destroyed by the 2005-06 eruption) the ground slopes gently upward to the floor of the

crater, which is about 50 feet above sea level (observed by the author till June, 2005). In the centre of

this rises the little cone of slightly truncated form. Symmetrical in outline, 1000 feet high and perhaps

2000 feet in diameter at the base, there is nothing to remind one of more closely than a huge heap of

purplish – black coal – dust, with patches and streaks of brown on the top. To the right and left of the

base , and thence towards the sea, flows a broad black steam of clinker lava, the masses of which it is

composed varying in dimension from rugged block of scoriae a ton or more in weight to pieces the

size of one’s fist”.

While describing vegetation inside the crater, Capt. Kloss (1902), observed that the ground at the base

of the cone widest on the southern side was covered with tall bamboo grass and various kinds of low

bushes. On the inner slope of the crater, the south and east side (which are of rocky formation

composed of prehistoric volcanic), support certain amount of small forest. In 1789, only withered

shrubs and blasted trees were to be seen on parts remote from the cone (Blair); while as late as 1866

there were no trees of any height, but on the slopes and ridges abundance of bushes, some rising 20

feet was found (Report of the Andaman Committee). Thus, records of vegetation also confirms that as

late as 1860, the Barren Volcano witnessed an intensified explosive activity which slowly ceased by

1901 when Capt. Kloss visited the Island.

Not much published data on Barren Volcano is found between 1903 to 1959.

Karunakaran and Raina (1960, Unpublished GSI reports) records that western and northern slopes of

the crater rim was traversed by a number of cracks, an inch to one-foot wide and up to 20-feet long,

through which steam and sulphurous gases were issuing out spasmodically. Inside the crater, steam




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was issuing out from an area of 100 square feet on the slope of the crater, as well as through several

cracks in the floor of the crater. The top section of the cone from the rim down to about 50 feet,

showed thick encrustation of sulphur.

Powde and Raina (1961, Unpublished GSI report) observed super-heated steam and gas oozing out

from the north face of the crater. Ground temperature at the crater varied between 450

C to 850 C

with

deposition of sulphur, plastic clay, gypsum and anhydrite. NE subsidiary vent showed similar

deposition with ground temperature of 650 C. (Author observed no such activity at the base of the

cone but observed issuing of vapour from the southern and eastern periphery of the rim and sulphur

encrustation down to 25 feet on both sides of the cone, when he climbed on the top of the main cinder

cone in 2005).

Fig.20: Fumerolic activity observed on the inner wall of the main cinder cone down to 25m

inside the cone on 16th

February 2005. Northern, eastern and southern sides of both outer and

inner wall of the rim of the pyroclastic cone (at a height of 235m) was covered with white to

light brown coloured pasty material (plastic clay, gypsum and anhydrite ) making the surface

very slippery. White vapour was emanating from NSE of rim with ground temperature higher

than air temp of ~350C. However, no smell was observed suggesting a sulphuric emission as

observed by Powde and Raina (1961).

No records are available about the activity of the volcanoes for another 25 years.

Haldar (1988) paid two visits to the island in April, 1986 and March, 1987 and observed deposition of

sulphur and red plastic clay and emission of superheated steam at the northern part of the crater.

Ground temperature in the western and northern valley-face was comparatively higher than normal.

Interestingly, they observed high population of rats near the landing site.

In 1989, Banerjee et al., while studying the magnetic signatures across the island detected presence

of heated mass at shallow depth with 10 to 12 times higher heat flow as compared to the adjacent




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terrain. The calculated Curie Isotherm surface was located about one km below the sea bed near the

island and did not rule out the resurgence of volcanism.

Haldar et al. (1990) noted continuous emission of super heated steam through cracks at the northern

floor of the crater with deposition of sulphur, Kaolinite and Natroalunite. Ground temperature at the

outer flank of the existing cone and also at the northern valley was abnormally high compared to that

recorded by them during 1986 and 1987 investigations. Surprisingly, they noted the absence of rats at

the landing site which were found to be abundant in April, 1986. Possibly these were the pre-

cursors of a new eruption which was confirmed on 29-30th

March, 1991 when Commander Coast

Guard, Port Bair confirmed that “thick jet of gas spewing off the top of the existing cone” has been

observed by a mercantile ship and also by a team from the Directorate of Light House and Light

Ship, Port Bair ( Shankar et al, 2001).

Thus began the most active phase of Barren Volcano which is well

documented and published. The Recent Eruptive record from 1991 till 2011

will be compiled in Part-II of the Pictorial Journey of Barren Volcano.

Fig.21: Thick column of the Pre-historic caldera wall (PH) exposed on the northern side of

the rim is dipping NE. The pyroclasts deposited during the historical (H) times (1787-1990)

is dipping southerly and lies unconfirmably over the PH. The Recent (R) deposits (1991-

2011) are mainly volcanic ash with some boulders and covers both PH and H increasing the

height of caldera rim. In the foreground is also seen the latest (2010) lava flowing westerly

towards the sea and filling the valley between main cinder cone and caldera rim consisting

PH, H and R.




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Fig.22: Underwater/sub- aerially deposited NE dipping ~ 100 m thick pre-historic pyroclastic

caldera wall (light yellow colour) is unconfirmably overlain by ~20m thick loosely packed

and unasserted southerly sloping pyroclasts (light gray and covered by shrubs) ejected

during historical time (H).

Fig.23: Light gray, thick and loosely consolidated pyroclasts deposited aerially during

historical times is partially covered with shrubs. Recent clinkery lava flow with thinly-

covered ash is seen in the foreground.

Suggested Readings:




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Ball, V., 1893, The volcanoes of Barren and Narcondum islands in the Bay of Bengal, Geol. Mag., P. 289.

Hodbay, J. R. And Mallet, F. R., 1885. The volcanoes of Barren and Narcondum islands in the Bay of Bengal,

Mem. GSI, v..21(4), pp. 252-286.

Karunakaran, C. and Raina, V. K., 1961. Report on the Preliminary investigations of the Barren Island,

Unpublished GSI Report, FS, 1959-60.

Kloss, C. K., 1902. Barren Island and the Archipelago, In Andaman and Nicobar. Unknown Publisher, pp. 9-17.

Luhr, J. F. and Halder, D., 2006, Barren Island Volcano (NE Indian Ocean): Island- arc high-alumina basalts

produced by troctolite contamination. Jour. of Volcanology and Geothermal Research, v.149, pp. 177-

212.

Mallet, P. R., 1895. Some early allusions to Barren island: with a few remarks thereon, Rec. GSI, v. 28(1), pp.

23-34.

Powde, M. B. And raina, V. K., 1962. Investigation for sulphur, in Barren and Narcondum Islands, Unpub. GSI

Report FS 1960-61.

Raina, V. K., 1987. A note on the sulphur occurrences in the volcanoes of Bay of Bengal, Indian Mineral, v.

41(3), pp. 110-125.

Raghav, S., 2005. Barren Erupts Again, Samudrika, v.12, pp. 59-60.

Shankar, R., Haldar, D., Absar, A. Chakraborty, 2001; Pictorial Monograph of the Barren Island Volcano-The

lone active volcano in the Indian Subcontinent. Spl. Publ. No.67, GSI Published by Director General,

GSI, 27, J L N Road, Kolkata-16. (References of earlier records from this book has been quoted in the

text which are otherwise not mentioned here)

http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=46047

http://www.indianetzone.com/40/barren_islands.htm

http://www.volcanolive.com/barrenisland.html

http://volcano.oregonstate.edu/barren-island

http://dsc.nrsc.gov.in/DSC/Others/ODEventsTable.jsp#

http://visibleearth.nasa.gov/view_rec.php?id=20825

http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=16388

About the author

Mr. Sanjeev Raghav is Senior Geologist, Paleontology Laboratory, Marine Wing, Geological Survey of India,

Kolkata and has participated in over 25 cruises on board coastal and deep sea survey vessel of GSI namely R. V.

Samudra Kaustubh and R. V. Samudra Manthan and has graduated from the youngest participant in 1988 to the

Chief Scientist in 2010. During his 24 years of profession as marine geologist Mr. Raghav has worked in various

spheres of marine studies like near shore and deep sea survey of the Bay of Bengal and Andaman Sea, Placer

mineral investigation along the east coast of India, Construction sand investigation off Andaman group of

Islands, Mud Volcano studies of Andaman Islands and Barren Volcano expedition since 2001. However, his

thrust area had been the foraminifer study of sea bed sediments collected during various cruise. He has co-

authored over 25 articles in national and international journals. He was the editor of Hindi Journal on Marine

Studies “SAMUDRIKA” published by the GSI. He is principal investigator of the projects on “high resolution

late Quaternary climate changes and monsoonal evolution of the Bay of Bengal with the help of palnktonic

forminifera”. Email: [email protected]

barren volcanobarren volcano---- a pictorial journey from recorded past ......

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