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Seismic Research Unit investigates sea disturbance near Radix Point
From: Richie Robertson <richie.robertson@xxxxxxxxxxxxxx>
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News Release
Contact: Stacey Edwards <staceyedwards@xxxxxxxxxxxxxx>
St. Augustine, Trinidad & Tobago W.I. - July 26th, 2007 – The Seismic
Research Unit have confirmed reports of a disturbance at sea, about five
miles east of Radix Point on the east coast of Trinidad. This is
probably caused by an underwater mud volcano, similar to that at Chatham
Island and several on-shore mud volcanoes in Trinidad.
Staff of Repsol YPF, who regularly fly over the area, reported a
"bubbling of the sea" and extensive brown discoloration of the sea water
since about July 11. The location was given as 10 22.498'N, 60 55.322'W.
Dr Richard Robertson, Director of the SRU, viewed the site from a
helicopter on 24 July. The sea was calm. The disturbance consisted of a
region of breaking waves, about seven to ten metres in diameter. This
was partially surrounded by a region of light-brown discoloured
seawater. The waves were breaking east to west over an underwater
feature. The feature could not be seen but could have only been, at
most, a few feet below the surface. There was also a circular pattern of
small waves, centred on the disturbance. There was no evidence of any
bubbling or gas emissions that might drive such waves, and the circular
pattern was probably generated by waves that are reflected and refracted
by the source region.
The discoloration was being carried to the north-northeast by the
prevailing currents, disappearing completely at a range of about 100
metres (350 feet).
Close examination revealed a number of discrete brown plumes of material
which appeared to be coming from shallow vents. These could be seen on
the south and west margins of the disturbed area, although other sources
might have been be obscured by the muddy water.
SRU also received reports from people who were diving in the area about
two months ago. They observed brown material coming from what appeared
to be a single vent on the sea floor, about 15 metres (50 feet) below
the surface.
Bathymetric charts, last updated in 1931, show water depths of about 15
metres (50 feet) in this area.
All the observations suggest the source is an underwater mud volcano.
The extrusion of mud over a period of about two months appears to have
built up a 15 metre (50 feet) high mount which is now just below the
water surface. This is very similar to the activity at Chatham Island,
which produced short-lived islands in 1964 and 2001.
It is not possible to say how long the activity will continue and
whether it will result in the creation of an island like Chatham Island.
The edifice is subject to much greater erosion nearer the sea surface,
so may never break the surface.
The hazards generated by this activity are very localised. There is a
real danger to any boats that approach the disturbed area and sailors
are encouraged to adopt a cautious approach and stay more than one mile
from the disturbance.
More information about mud volcanoes in Trinidad and Tobago can be found
at the Geological Society of Trinidad and Tobago’s website
(http://www.gstt.org/teaching/mud%20volcanoes.htm).
For information on geologic events in the Eastern Caribbean, visit
www.uwiseismic.com
REPORT ON DISTURBANCE IN THE SEA SURFACE OFFSHORE RADIX POINT, TRINIDAD
http://www.uwiseismic.com/News/advisories.html
Background
A report was received at the Seismic Research Unit on Wednesday 18th
July 2007 regarding a disturbance in the sea surface approximately 5
miles east of Radix Point, off the east coast of Trinidad. Repsol YPF
indicated that, during a helicopter flight to oil platforms offshore
they had observed what appeared to be ‘bubbling of the sea’ in the
vicinity of the areas located at 10 22.498 degrees N, 60 55.322 degrees
W during the previous week. The disturbance of the sea surface was
accompanied by a brown discoloration of the sea water. The SRU informed
the CEO of the ODPM about an hour later and advised that the report
should be investigated. The SRU indicated its willingness to assist with
the investigation and gave a preliminary opinion that the disturbance
may be activity associated with a mud volcano .
On Monday 24th July, 2007 the SRU was asked by the ODPM to assist with a
site visit to the area. Arrangements were made later that day for Dr.
Richard Robertson to accompany officers of the SAUTT in a helicopter
reconnaissance of the area. This report provides an account of the
observations made during the site visit and presents some preliminary
conclusions and recommendations for further action to be taken.
Observations
The area of disturbance is located approximately 4 miles east of Radix
Point on the east coast of Trinidad (see Figure 1) and essentially
consists of a 7-10 region of breaking waves (‘white water’) partially
surrounded by a region of light brown discoloured sea water that trails
off towards the north-northeast. The ‘core’ area of ‘white water’
consists of waves that break from east to west and which appear to be
refracted in a circular pattern (see Photo 1). This ‘core’ area is
partially surrounded by light brown discoloured sea water which forms a
tail that extends for approximately 25 meters towards the
north-northeast eventually dispersing completely by about 100 metres.
There are a number of discrete features to the south and west of the
amorphous, brown discoloured mass that surrounds the ‘core’ area, which
appears to be brown plumes emanating from the sea floor. There was no
direct evidence of bubbling or gas emission and the observations did not
allow an estimate of temperatures to be obtained or direct sampling of
the water or brown dispersion. The brown deposits in the sea also
prevented any observation of any features beneath the sea surface.
Conclusions
Bathymetric charts for the area suggests that the water depth should be
8-10 fathoms (~14-16 metres) in the vicinity of the ‘core’ area. The
fact that breaking waves were observed in an otherwise calm sea suggests
that the water depth shallows significantly in this area. Reports of
this feature has only been quite recent and therefore suggests that the
reduction in ocean depth has occurred within the past week. The
observation of brown plumes beneath the sea surface suggest the presence
of discrete vents (possibly gaseous) which are emitting fine brown silt
or mud. The circular pattern observed in the breaking waves suggest the
presence of a central vent emitting brown silt or mud that is pushing
the breaking water beyond the wave crests.
The most likely conclusion for the observations and reports received is
that an eruption of a mud volcano (see bibliography for detailed
descriptions) has occurred in the area. Extrusion of mud over the past
week has resulted in the construction of an undersea mount which has
resulted in a significant reduction in the depth to offshore platform in
the area. The activity is not ‘volcanic’ senso stricto since it does not
involve the extrusion of magma.
Recommendations
1. A program of regular monitoring of the area should be instituted.
2. The public should be alerted to the activity and an advisory given in
terms of the possible dangers which may be posed by the activity.
3. Contingency plans should be made for the possibility that the
activity may continue for some time, may at times be explosive and may
result in the creation of new island.
4. The assistance of the GSTT and/or IMA should be sought to continue
investigations of the phenomena to better understand its origin and make
projections regarding its further development. In this regard a sample
should be obtained of the brown deposit and analysis done to determine
the composition and possible origin of the material.
Bibliography (taken from the GSTT website <http://www.gstt.org/>)
Anderson R. 1911 A new gas volcano in Trinidad Science Vol.34 p 834 - 835.
Arnold R. 1912 Note on mud island appearing off Chatam coast,
31/10/1911. Petroleum World. March.
Arnold R. & Macready G.A. 1956 Island forming mud volcano in Trinidad,
British West Indies. Bull. AAPG Vol 40 No 11 p 2748 - 2758.
Barr K.W. 1953 The mud volcanoes of Trinidad. Caribbean Quarterly Vol.3
No.2 p 80 - 85.
Birchwood K.M. 1965 Mud volcanoes in Trinidad. Inst. Petrol. Review
Vol.19 No.221 p 164 - 167.
Drew I.M., Kerr P.F. & Richardson D.S. 1970 Mud volcano clay, Trinidad,
West Indies. Bull AAPG V. 54 N.11 p 2101-2110.
Herring A.T. & Nettleton L.L. 1979 Quantitative analysis of a mud
volcano gravity anomaly. Geophysics V.44 N.9 p 1518-1524.
Higgins G.E. & Saunders J. 1974 Mud volcanoes - their nature and origin.
Verhandl Nature. Ges Base Vol.84 No.1 p 101–152.
Higgins G.E. & Saunders J.B. 1967 Report on the 1964 Chatam mud island,
Erin Bay, Trinidad, West Indies. Bull. AAPG Vol. 51 No.1 p 55- 64.
Higgins G.E. & Saunders J.B. 1974 Mud volcanoes - their nature and
origin. Contributions to the geology and paleobiology of the Caribbean
and adjacent areas. Verhandl naturf. Ges. Basel, Band 84, Nr.1, 520pp.
Kugler H.G. 1932 Contributions to the knowledge of sedimentary volcanism
in Trinidad. Jour. Inst. petrol. technol. Vol.19 No.119 p 743-760.
Kugler H.G. 1936 Nature and significance of sedimentary volcanism. Sci.
Petroleum 1 p 297 - 299 (Oxford University Press).
Kugler H.G. 1968 Sedimentary Volcanism. Trans. 4th Caribbean Geological
Conference, Trinidad p 11 - 13.
Weeks W.G. 1929 Notes on a new mud volcano in the sea off the south
coast of Trinidad. Jour. Petrol. Tech. Vol.15 No.74 p 385 - 391.
Wilson C.C & Birchwood K.M. 1965 The Trinidad mud volcano island of
1964. Proc. Geol. Soc. London No. 1626 p 169 - 174.
Wilson C.C. 1930 Mud Flow. Jour. Inst. Petrol. Vol.10 p 578 - 580.
Yassir N.A. 1987 Mud Volcanoes : Evidence of neotectonic activity. Mem.
Geol. Soc. China N.9 p 513-524.
Wharton, S.R. & Hudson, D. 1995 Report on a recent eruption of the mud
volcano, Devil's Woodyard, south Trinidad Abstracts 3rd GSTT Conference
and 14th Caribbean Geological Conference and 14th Caribbean Geological
conference, Trinidad, p. 85.
Dia, A.N. , Casterec-Rouelle, M. , Boulegue, J & Comeau, P. 1999
Trinidad mud volcanoes : Where do the expelled fluids come from?
Geochima et Cosmochima Acta, Vol. 63, No. 7/8, p 1023 – 1038.
Kerr, P. , Drew, I.M. & Richardson, D.S. 1970 Mud volcano clay,
Trinidad, West Indies. Bull AAPG V. 54, No 11, p 2101 – 2110.
Prinzhoffer,A., Battani,A. , Ballentine,C.,Deville,D. , Herbin, J.P.,
Houzay,J.P. 2000 Gas geochemistry from mud volcanoes of Trinidad:
Surface evidence of deep gas reservoirs, modified by vertical migration
Journal of Conference Abstracts, Volume 5(2), p. 819.
Deville,E. et al 2002 The origins and processes of mud volcanism:
Insight from Trinidad Abstracts 16th Caribbean Geological Conference, p.
75 – 76.
Burke, K., Casey, J.; Robertson, P. 1984 Deformation of Orinoco Delta
mud diapirs in the South Caribbean strike-slip plate boundary zone Eos,
Transactions, American Geophysical Union, April 17, 1984, Vol. 65, Issue
16, pp. 190.
Nettleton, L. L. & Herring, A. T. 1979 Quantitative analysis of a mud
volcano gravity anomaly Geophysics, September 1979, Vol. 44, Issue 9,
pp. 1518-1524.
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