Imaging fluids in the Lesser Antilles subduction zone
.We all know about Earth’s water cycle of evaporation, condensation and precipitation between the surface and atmosphere. In 2017, an offshore scientific expedition is trying to find out about a less well known type of water cycle. Huge amounts of seawater soak and seep into Earth’s crust when it is made in the middle of the oceans, but what happens to all this water when crust sinks and ‘dies’ along subduction zones in places like the Caribbean? Here, water may reach down to depths of tens to hundreds of kilometres into the solid Earth.
Water is known to be a key component that causes the mantle to melt, which eventually forms magma at shallower depths, causing potentially hazardous volcanoes. Water may also lubricate or increase the pressure along titanic faults that have the potential to cause huge earthquakes. It is possible that the Caribbean plate boundary may generate earthquakes as large as the magnitude 9 Japan earthquake in 2011. This is not unprecedented. In 1843, a magnitude 8 earthquake and tsunami devastated the Caribbean islands. The region suffers also from damaging eruptions – the 1995 eruption on Montserrat was one of the most devastating eruptions in recent times.
If we can track the movement of water as it descends into the Earth, then we may be able to understand better what causes the build-up of magma in certain locations. We could also try to estimate the earthquake potential of the Caribbean subduction zone.
Since Spring 2016, we have had incredibly sensitive instruments called ocean bottom seismometers (or OBS for short) sitting on the seafloor in waters around the Caribbean islands. These instruments have been listening out for any tiny crackles that may be caused by the ‘squeezing’ of water as it descends into the subsurface. Also, by detecting more distant earthquakes, we will carry out a 3-D ‘x-ray’ of the region to find out areas where water may be ‘ponding’ and how it affects the surrounding geology.
The experiment will be the first to make a detailed study of the Atlantic ocean’s tectonic ‘demise’.
The project has been funded £3.2m by the UK Natural Environment Research Council
The project is a large multi-disciplinary research consortium involving seismologists, geologists, chemists and numerical modellers from multiple institutions around the UK (e.g. Imperial College, U. Southampton, U. Bristol, U. Durham, Oxford Uni).
Collaborators on the seismology component of the project: Dr Catherine Rychert (U. Southampton), Dr Nick Harmon (U. Southampton), Mr Ben Chichester (U. Southampton), Prof Andreas Rietbrock (U. Liverpool), Dr Lidong Bie (U. Liverpool), Dr Jenny Collier (Imperial College), Dr Saskia Goes (Imperial College), Mr Robert Allen (Imperial College).
For more information, please visit the VOiLA website.