Even though there are twenty-six known mud volcanic areas in the onshore of Trinidad, eruptive activity has been documented only at six of these . Three, along the crest of the Southern Anticline and three just south of the central range near the centre of the island.
A graph illustrating the timing and frequency of documented mud volcano eruptions between 1852 – 2022 shows some clustering of activity.
A similar plot for six mud volcanoes over the same time period shows that the south coast mud volcanoes were fairly active between 1891 and 1911, 1960 – 1965 and 1998-2001.
The sudden and rapid creation of shallow banks and islands (Plate 4) can create navigational hazards especially in areas with high levels of marine traffic. Offshore Chatham on the south coast is an area on identified as Despatch Reef, which marks the location of the 1911 and 1928 mud volcano eruptions. Over time these were eroded by waves and currents below sea level, no new bathymetric surveys have been done in this area and such changes in water depth due to mud volcanic activity is unknown. There is a possibility that vessels may run aground due to inaccurate maps.
Gas and Liquid Hazards
Analysis of the gasses at selected sites by Higgins & Saunders (1974) and DeVille et al (2003), revealed that it is primarily methane (93%) and Carbon Dioxide (6.54%), minor amounts of Ethane (0.33%) and no Hydrogen Sulphide. Thus, the only danger posed is the methane igniting, Carbon Dioxide levels are too low to be a concern especially in open areas.
Where does the water contained in the mud come from? Research by Dia et al (1998) and Castrec-Rouelle et al. (2002) on concentrations of trace elements, isotopes of 10Be, 9 Be, Oxygen, Hydrogen and Strontium, revealed revealed that they were due to mixing from meteoric shallow aquifers from deeper than 3km. This deep source is the reason why even during the driest periods mud pools and fluids are present. Higgins & Saunders (1974) analysed water from selected mud volcanoes and found that the pH averages 8.9 which is basic, salinity averages 18,439 ppm. Piparo has the lowest salinity, this suggests that meteoric water recharge is important here.
Disruption of the ground surface
The Google Earth image with mud flow overlay reveals that most of the village of Piparo is built on old mud flows.
This video of the 1997 eruption shows one of the dangers to residents, burial by mud flow, here men, women and children are seen casually walking towards the eruption. It was only when the euption became more violent that they started to run away.
Photos taken in 1997 showing the left lateral motion of the land with the house to the west, the 2019 photo shows an addition to this house that has separated from the structure. It was claimed that this was due to the mud volcano, however the author believed it was due to downslope soil creep and poor construction methods.
Tabaquite mud volcano, also locally known as Brickfield mud volcano, has legacy mudflows that cover 80 acres . The mud has built up a low ridge near the main vent, towards the SW, the flows seem to follow the river valleys. Most of the settlement and roads are found on these flows. The 2019 eruption only covered 1.6 acres completely burying all the vegetation within that area. No vent, bubbling gas or fluids were observed on the 10th August 2019.
At Devil’s Woodyard legacy mudflows cover 146 acres , while the 1995 eruption covered 3.1 acres and the 2018 eruption covered 2.9 acres. Similar to Piparo, the modern eruptions were only 2% of the legacy flows, and occurred in close proximity to houses. None of the infrastructure was destroyed or damaged, on the south western side large pressure ridges of displaced grass covered soil and faults were seen. The 2018 eruption occurred slightly west of the 1995 eruption
The Erin group of mud volcanoes , including the Erin Bouffe has legacy mudflows that cover 350 acres. There are currently three areas of activity, the largest being Erin Bouffe or as is now being called, the Los Iros mud volcano. The area is primarily agricultural, with farmers avoiding the areas with active mud vents, cultivating tomatoes and hot peppers.