Most of the volcanoes on Earth are under the sea, yet scientists know far less about them than about volcanoes on land. A new expedition near Tonga set out to close part of that gap.
The research vessel Falkor, operated by the Schmidt Ocean Institute, has finished a 41-day voyage in the area. The crew used advanced technology to map, view and sample underwater volcanoes. Much of the work was shared with the public in real time through video streams and chat.
The team came back with a long list of results. They found widespread evidence of explosive volcanism in the deep sea. They also saw one of the rarest volcanic rock types on Earth and explored the largest known dacite lava flow on the planet. On top of that, they discovered three new hydrothermal vent sites.
The volcanoes sit close together, since their bases are only about 0.6 km apart on average. Even so, they differ a great deal. Four of them have active hydrothermal systems, and another has an inactive site. The style of venting, the shape, spacing and height of the chimneys and the communities of animals living among them all vary from site to site.
The scientists studied each volcano’s geological and magmatic history on its own and then as part of the group. That approach is meant to show how submarine volcanoes grow over time and how their eruption styles change.
Ken Rubin, the principal investigator, said submarine volcanism is a basic process that has shaped the makeup of the oceans and the seafloor. In his view, it has also influenced the development of life on Earth. He named four top discoveries. The first was the number of recent eruptions in the area. Then came the amount of explosive volcanic deposits in the deep sea. He also listed the wide range of eruption styles on small, closely spaced volcanoes, as well as the number and variety of hydrothermal systems and habitats.