Underwater Fire: Studying the Submarine Volcanoes of Tonga

Robot Discoveries

West Mata and the volcanoes around it offer a rare opportunity to examine active volcanic processes and this multidisciplinary study will be there to document them with several tools for exploration. The scientists will get an in-depth look at the products of volcanic eruptions, including lava flows, broken fragments, and hydrothermal chimneys.

The first step will be to create high resolution bathymetric and backscatter maps to identify dive targets. Backscatter is the amount of acoustic energy being received by the sonar, which gives insight into the seafloor composition. Falkor’s multi-beam mapping capabilities will uncover details of volcanic, tectonic and hydrothermal structures. The maps will be used to guide underwater robotic vehicles on the bottom of the ocean and in the water column, and to compile information to examine hydrothermal plumes.

Using an Autonomous Underwater Vehicle (AUV), geophysical and water chemistry data will be collected as well as higher resolution imagery so that the team can target selected chimneys. Fluid temperature and chemistry play a major role in determining which organisms, both microbes and macro-fauna, live in certain areas. Measuring water properties such as temperature, pH, and oxygen concentration provides critical insight into the tectonics, magma geochemistry, and fluid chemistry.

Following the AUV leg, scientists will go back and dive on selected vents with Remotely Operated Vehicle (ROV) SuBastian. Taking high 4K video and samples of lava and pyrocalsts (volcanic fragments) will allow the team to reconstruct eruption conditions and magma properties. Biological and chemical samples will provide a better look at the microbiology of the vent fluids and biota. Expedition scientists will use the chimney and biota sampling to understand geographic, tectonic, and rock chemistry influences on the various vents and their associated fauna.

Underwater Surprises

What makes this expedition extra special is the chance of seeing an erupting underwater volcano in real time. There is a small chance that West Mata will be going off during the expedition, and so far is the only place globally where scientists have seen lava flowing across the sea bed. Regardless of the volcanic activity, this research will make important strides in building an integrated ecosystem level history of several volcanoes. Five weeks might seem like a long time, but scientists and crew will need every second to follow the volcanic clues that the Tongan Sea has scattered along Falkor’s route.

Partial support for this expedition comes from the NOAA Ocean Exploration and Research Program and the NOAA Pacific Marine Environmental Laboratory.