RADHICA DE SILVA
radhica.sookraj@guardian.co.tt
Three years ago during deep sea exploration, a land mass believed to be a sunken magmatic volcanic island, was discovered off the coast of Tobago.
Buried under 10,000 feet of sand and clay beneath the seabed, the volcanic island was dubbed Tobago's long lost sister by geoscientists. This volcanic island, which is about the size of Tobago, is one of T&T's wonders which average citizens know nothing about.
In this series, the Guardian will explore some of the geological wonders of the islands, both on and offshore, including our volcanoes.
Senior geoscientist at Touchstone Exploration Xavier Moonan, who has been working on exploration drilling prospects within the Ortoire Block (onshore southeastern Trinidad), has done extensive geological research across T&T including our mud volcanoes.
Having served as a mudlogging geologist for Schlumberger (Geoservices), an exploration geologist at Petrotrin and later at Centrica, Moonan was part of the team which discovered T&T's only saltwater volcano in 2017, located 15 miles deep in the forests of Guayaguayare.
At Moruga, the Marac volcano is known by villagers as T&T's second pitch lake; the colourful Anglais Point mud volcano of Erin, which is flowing into the sea; as well as the popular Piparo, Digity and Devil's Woodyard volcanoes will all be explored, along with many more.
The Digity volcano is the only one with a tall, distinct conical shape. The stories surrounding the historic eruptions of Piparo volcano and the Devils Woodyard volcanoes remain part of T&T's unique folklore and these will be explored as well.
The volcanoes, Moonan believes, are hidden treasures which could bring foreign exchange to T&T if properly marketed as part of T&T's tourism thrust.
Buried volcanic island
Trinidad and Tobago are not volcanic islands. Unlike the islands of the Eastern Caribbean such as Grenada, St Vincent, St Lucia, Martinique, Dominica, Guadeloupe, Montserrat, Nevis, St Kitts, St Eustatius and Saba, T&T does not have live volcanic centres. However, Moonan said this does not mean that the islands do not have rare and fascinating geological formations.
In an interview, Moonan said in 2016 the buried volcanic island off the coast of Englishman's Bay in Tobago was discovered by geoscientists.
"A former operator of the Block-22 and North Coast Marine Area (NCMA-4) presented a paper at the Society of Petroleum Engineers T&T Energy Conference held at the Hyatt Regency in 2016 in which they were able to map and positively identify a buried, former volcanic island, the long lost sister of Tobago," Moonan disclosed.
He said the operator coined the island Isla de la Asumpción, after one of the original names Christopher Columbus had for the island of Tobago.
"The ancient island basically was pulled downwards constantly over millions of years and it is now buried beneath 10,000 feet of sand and clay below the seabed. The area continues to move relatively downward with respect to the Tobago northern coast, with the seabed in that area ranging between 1,500 to 3,000 feet below sea level, so the area is currently in very deep water," Moonan said.
He said about five million years ago the area was relatively shallow water and the tops of the volcano peaks, may have appeared as stacks just about to go below the water level.
"About eight million years ago, Isla de la Asumpción occurred a mere 10km immediately north of Tobago. The island shared many similarities to that of Tobago. It was approximately the same length, width, and orientation, and its highest mountain peaks are virtually the same," Moonan said.
"Pigeon Peak in Speyside Tobago is located on the northeastern part of the island and measures some 550 metres. Mt Karuna on Isla de la Asumpción is also located on the northeastern part of the island and measured some 524 metres above sea level."
Through using high-resolution 3D seismic data, Moonan said maps were generated on the top of the volcanic rocks or basement.
"These rocks are very similar in nature to those onshore Tobago, and are currently buried beneath 10,000 feet of sediment below the seabed. Upon close examination, this map revealed strong evidence of dendritic drainage—a telltale sign of riverine erosion," he said.
So what happened to Isla del la Asumpción and why did she sink beneath the waves?
Moonan said earthquakes and by extension, movement along the North Tobago Fault over the last eight million years have resulted in the drowning and subsequent burial of Isla de la Asumpcion.
"So just imagine that if you were able to be on Englishman's Bay some eight million years ago, staring offshore you would not have been able to see Grenada, because an island as big as Tobago itself lay right in front of you," he said.
