T&T's north-west coast going down
Kristy Ramnarine kramnarine@trinidadexpress.com
Trinidad Express
Sunday, June 3rd 2007 gulf of paria: A close-up view of the north-west coast of Trinidad in Westmoorings recently.
The north-west coast of Trinidad along the Gulf of Paria is sinking because of movement in the earth's faults.
Dr John Webber of Grand Valley State University Allendale in Michigan, who has been scientifically studying Trinidad and Tobago's landscape, said the movement of the active faults around Trinidad causes stretching in the Gulf of Paria.
"Our work deals with looking at the landscapes in Trinidad (both qualitatively and quantitatively) and from it trying to read the signal of vertical ground motion," he told the Express yesterday.
"The landscape shows that north-west Trinidad is going down relative to north-east Trinidad. We're not sure how far south past the Central Range we can take this. And we don't have any rates yet."
Recently Dr John Agard, Chairman of the Environmental Management Authority, said the south-west coast of Trinidad in the area of Cedros is sinking. He attributed his statement to the rise in sea levels around Trinidad.
Dr Webber's initial qualitative "read" was presented in, Occasional Papers of the Geological Institute of Hungary, volume 204 entitled: "Neotectonics in the Trinidad and Tobago, West Indies segments of the Caribbean-South American plate boundary." He has done quantitative work that supports the initial model with Professor John Ritter of Wittenberg University Ohio.
"There is a cause for the relative ground motion that we infer that makes good geologic sense," Webber explained.
"This gives us confidence that we may be onto something reasonable. The active sliding fault in Venezuela is north of where the Global Positioning System (GPS) tells us the active sliding fault in Trinidad is. These two faults must connect so that the Caribbean plate can slide eastward past the South American plate at the 2cm/yr we measure using GPS.
"We and others propose that this connection occurs across the Gulf of Paria, which is low-lying and filled with a thick pile of young sediments. And can be thought of in a simple way as a hole in the ground that keeps widening and deepening as the plates move by one another. Geologists call this sort of geometric configuration/connection a pull-apart basin."
He added Death Valley in California is a well-known example of what is taking place in Trinidad.
"You can make a model of this by cutting a piece of paper along the two active faults and one edge of the Gulf of Paria and sliding the top half of the paper (the Caribbean plate) to the right (eastward). You will see the Gulf pull-apart open up and widen.
"Our work shows that the landscapes on both the Trinidad and Venezuelan sides look like they are sinking as mirror images into the Gulf. We will present this work and lead a field trip showing people these features at the upcoming Geological Society of Trinidad and Tobago's Fourth Geological Conference from June 17-22. Interested parties should come along and see what we see and hear what we think it means," he said.
At the opening ceremony of third EMA workshop, which dealt with climate change issues, Dr Agard said: "Sea levels is likely to continue to rise on average during the century around the islands in the Caribbean Sea.
"For Trinidad it is rising about 1.3 mm per year in the north coast and on average about 1.6 mm in the South West Coast which seems impossible for a small island. How can be have different sea level rise on different coasts?
"Well, it suggests that the South West Coast is sinking. Of course you know down on the Cedros end there is a lot of erosion and of course we have a large petroleum industry, so extraction of oil and gas from underground will have some subsidence."
As scientists continue their research into the matter, it is left to be seen whether movement in the earth's plates is also the cause for the sinking of south-west Trinidad.
