Recent Undersea Eruption in the Kermadec Ridge

A recent eruption at an undersea volcano on the Kermadec Ridge has caused the crater to be filled with debris and reduced the summit of Rumble III volcano by 100 metres.

An expedition to study three volcanoes in the southern part of the Kermadec Ridge has yielded unexpected evidence of a large undersea eruption within 400 kilometres of the Bay of Plenty coast. The eruption, which occurred at a volcano known as Rumble III, occurred within the last two years.

The ten-day expedition was carried out aboard a research vessel owned and operated by the University of Washington in the United States of America, and included scientists from the university, the U.S. Woods Hole Oceanographic Institute and New Zealand’s GNS Science. The primary purpose of the expedition was to allow thirteen final-year students from the University of Washington and four students from Britain’s Southampton University to complete their theses in geology, chemistry, physics and biology.

While providing guidance and advice to the students, the scientists also intended to gather more information on the submarine volcanoes in the area. This included obtaining a high-resolution map of the volcano known as Rumble II West following a mining company report of a large mineral deposit there. At Brothers, another active site, the hydrothermal system was analysed to detect any changes since the last visit by scientists.

The expedition set off from Lyttelton on March 2nd 2009, returning to Auckland on March 12th. It travelled to the Kermadec Ridge, a chain of 90 volcanoes stretching from the Bay of Plenty to Tonga. The volcanoes are mostly conical, some as large as the central North Island’s Mt. Ruapehu, but rising from the ocean floor. White Island lies at the southern end of the undersea chain, with Rumbles III, Rumble II West and then Brothers lying within 400 kilometres of the coast.

Several of the volcanoes have been intensively studied in recent years; by scientists interested in sea-life existing in hot and chemically complex waters, geologists studying volcanism, and others interested in discovering mineral wealth. When last visited in 2007, the summit of Rumbles III was only 220 metres below sea level, and it was thought to be ideal for studying the interaction of sunlight, hydrothermal plumes and plankton.

However, on arrival at Brothers III, the latest expedition found evidence of a large eruption having taken place. The summit was found to be 100 metres lower and the 800 metre-wide crater had been filled. Rumbles III sits in 1400 metres of water about 350 km north-east of the Bay of Plenty. Further examination showed that its summit was strewn with lava boulders covered in black volcanic ash.

Travelling on to Brothers volcano, the expedition studied dense accumulations of long-neck barnacles thriving in the extreme environment where acidic fluids were venting into the ocean. Mineral-rich plumes were discovered at vigorous high-temperature vents nearby.

A media release at the GNS website shows a map of the southern part of the Kermadec Ridge, but note that the three-dimensional map image is of Rumbles II, and not Rumbles III where the eruption occurred.

[ Compiled from media releases by GNS Science. ]

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