Friday 18 October, 2019

Devil's Woodyard mud volcano quiet, but for how long?

The recent eruption at Devil’s Woodyard, New Grant, has left residents shaken with many wondering when the next eruption will occur.

Following a series of three eruptions on February 12-13, 2018, the Geological Society of Trinidad and Tobago (GSTT), the Princes Town Regional Corporation, and the Ministry of Rural Development and Local Government have been monitoring the site, which has since been quiet.

The Ministry and Princes Town Regional Corporation are responsible for enacting safety measures and monitoring the event.

The University of the West Indies (UWI) Seismic Research Centre, although not responsible for providing information on mud volcanoes, has expressed an interest in the activity and recently held a Facebook live session to answer questions from the public.

The GSTT has also been monitoring the event and produced initial assessments.

(Photo: GSTT)

Seismic activity and mud volcanoes, are they linked?

Director of the UWI Seismic Research Centre, Professor Richard Robertson and Education Officer Mrs Stacey Edwards discussed the possible connection between seismic activity and mud volcanoes saying that although there may be a connection, much more research must be done before making a conclusion.

Speaking during a Facebook live session on February 14, Professor Robertson said further analysis is needed. 

“We don’t know that (earthquakes cause mud volcano eruptions, but) there have been studies in other parts of the world which suggest there’s a correlation between seismic activity and mud volcano activity.”

“The same fractures (cracking in the earth’s surface caused by seismic activity) that might be affected by earthquakes are the same pathways that mud volcanoes and mud gets to the surface,” he said.

“If you have earthquakes shaking the ground, they could cause these cracks to form along which mud could come through, but to say you could detect a signal…that’s difficult. We need to study it a lot more before we can say that conclusively,” he said.

However, GSTT president Stefon Harrypersad said the activity of mud volcanoes is more likely linked to the presence of oil and/or natural gas reserves.

“These mud volcanoes have more to do with the petroleum system and nothing to do with igneous/volcanic activity thus gases being emitted would be more predictable,” he said.

 

Living near mud volcanoes not wise, says Professor Robertson

Professor Robertson said instead of simply monitoring these sites, a comprehensive response comprising a set of protocols should be created to respond to future events.

We understand how earthquakes operate and so our best response is to plan…what we need is a set of protocols to respond to what happens.”

He said that living near to these sites is therefore unwise.

"They have been studied, we know what they are and what they can do and it's just a matter of how we respond to that...the reponse can be that as we have a mud volcano here and it has erupted in the past, maybe we would ensure that people don't live too close to it, because of damage to property."

"We cannot tell exactly when it is about to erupt. It doesn't give off very many signals."

If it is that the people are not doing that then that’s why we have authorities, governments, to guide our development in terms of long-term management of these mud volcanoes,” he said.

 

 

Over 174,000 barrels of mud deposited

Reports from the Geological Society of Trinidad and Tobago (GSTT) said the eruption reached a maximum height of 16 feet while the area of mudflow was estimated to be 2.738 acres with a volume of mud of 27,738 cubic metres or the equivalent of 174,472 barrels of mud.

The group said after an assessment on February 17, that activity at Devil’s Woodyard has since subsided.

Since Wednesday (February 14), the site has been relativity quiet and will continue to be monitored. Microfault displacements with the same general orientations were observed to the west of the structure and GPS points and measurements were taken to further add to data set. Folks at the Regional Corporation and the ODPM were also on site to share a discussion on the way forward,” the group said last Saturday.

GSTT Director Stefon Harrypersad and Lecturers from the Petroleum Studies Unit (UWI) Avinash Rambaran and Xavier Moonan conducted an assessment of Devil's Woodyard Mud Volcano, noting several characteristics.

Summarized here are some of our initial observations and assessments based on mapping trends of surface disturbances, faults/fractures and through use of drone mapping.”

“Most of the fractures show a left lateral sense of motion base on slickensides and the resulting local uplifts at right bends. No gas or mud emissions were noted in or along any of the fractures despite being water filled in parts.”

“The mudflow appears to have attained a height of at least 16ft above the former ground surface. Officials from the Princes Town Regional Corporation did note to us that the height was a bit greater yesterday, and as we expected it has begun to subside.”

The group added that there were trace emissions of gases such as thermogenic methane along with minute amounts of CO2, NO2 and H2S, however, these were in small quantities and were not harmful to the public.

The group said they intended to carry out a biostrat analysis on the clays seen in the erupted material.

 

What exactly are mud volcanoes?

According to the GSTT, a mud volcano is a violent eruption of watery mud or clay which is usually accompanied by methane gas and which tends to build up a solid mud or clay deposit around its orifice which may have a conical or volcano-life shape. 

Mud from volcanoes is usually a mixture of clay and salt water which is kept in a slurry-like state by the boiling or churning activity of escaping methane gas. 

The GSTT says there have previously been "highly explosive eruptions" where large masses of rock was blown violently out hundreds of feet into the air and scattered into the countryside. 

 

(Diagram: GSTT)

32 mud volcanoes in Trinidad

The GSTT listed a total of 32 known volcanoes throughout South Trinidad at the following locations:

1. Columbus/Galfa

2. Islote

3. Chatham

4. Erin

5. Anglais Point

6. Palo Seco

7. Chagonaray

8. Coora

9. Morne Diablo

10. Morne Diablo Beach

11. Landorf

12. L’eau Michel

13. Karamat

14. Rock Dome

15. Marac

16. Moruga Bouffe

17. Lagoon Bouffe

18. Digity

19. Devil’s Woodyard

20. Central Balata

21. Navette

22. Cascadoux

23. Piparo

24. Tabaquite

25. Colenso

26. Bois Neuf

27. Mayaro Bay

28. Challenger Shoal

29. Forest Reserve

30. Vessigny

31. Grande-Ravine

32. Point Fortin

For more information visit the Geological Society of Trinidad and Tobago online at www.thegstt.com or on Facebook at www.facebook.com/groups/THE.GSTT

 

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