Nz Scientists See Fiery Birth Of New Pacific Island
Two New Zealand scientists were part of an international team who this week witnessed the dramatic birth of a new
volcanic island near the Solomon Islands. The rare observation was made during an investigation of seafloor volcanic
activity and associated mineral formation in the Bismark and Solomon seas north of Australia.
Marine geochemist Gary Massoth and mineral geologist Cornel de Ronde, both of the Institute of Geological & Nuclear Sciences Limited (GNS), were part of an international team on the CSIRO research ship Franklin who made a
comprehensive study of the island-building eruptive activity.
The scientists found the shallow Kavachi seamount, which had been dormant for nine years, had started a new phase of
eruptive activity. Kavachi, in the Solomon Island chain of volcanoes, is only 30km from the boundary of the Indian and
Australian tectonic plates.
A roughly conical feature rising from a seafloor depth of 1100m, Kavachi is about eight kilometres in diameter at the
base and has produced ephemeral islands at least twice in the past century.
“ When we arrived at Kavachi, we found violent eruptions taking place every five minutes,’’ Mr Massoth said from Darwin
today. “ The eruptions were ejecting molten lava up to 70 metres above sea level, and sulphurous steam plumes rose to
about 500 metres. At night we were treated to a spectacular fireworks display with the red glow of eruptions
continuing.”
The ship approached to within 750 metres of the eruption centre and found that the volcano had grown substantially since
it was last surveyed in 1984. The scientists were able to sample freshly formed volcanic rocks from the flanks of the
erupting volcano.
“ This was an unprecedented opportunity and has given us valuable geological information. We also systematically sampled
gases and seawater at various depths around the perimeter of the volcano – something that has not been achieved before
with an erupting submarine volcano.
“ We detected particle and chemical plumes from the eruption at least 5 kilometres from the centre of the volcano. This
has provided valuable information about the impact of active volcanoes on ocean chemistry.”
Mr Massoth said Kavachi differed from Brothers volcano, the largest and most active submarine volcano north east of
White Island, in that Brothers was deeper and hydrothermally active while Kavachi was shallow and volcanically active.
“ Hot rock, or lava, predominates at Kavachi while hot water predominates at Brothers.” Hydrothermal fluids were venting
from Brothers volcano at about 300oC against 100oC at Kavachi. Hotter fluids react with the volcano host rocks more
efficiently and are more heavily laden with dissolved minerals.”
Observations at Kavachi showed that lava being quickly quenched in seawater did not produce a strong chemical plume in
the ocean, unlike the active volcanoes northeast of White Island which vent large volumes of hydrothermal fluids and
heat into the ocean.
“ Kavachi has confirmed our observations that forearc volcano chains, such as the Kermadec chain north east of White
Island, contribute significantly to the global inventory of heat and chemical emissions entering the oceans.
“ The work we have been doing in New Zealand waters is effectively re-writing the textbook on submarine volcanism.”
About 80 percent of the world’s volcanism occurred in the ocean and only a small proportion of all submarine volcanoes
had been systematically surveyed with scientific equipment, Mr Massoth said.
At another location, the scientists dredged up what they believe is a world-record size “black smoker” – a 2.7m-high
chimney prised from an active volcanic vent at a depth of 1700m. Black smoker chimneys are packed with minerals –
typically 1000 to 10,000 more concentrated than background levels in seawater. The chimney was expected to be rich in
silver, zinc and gold, Mr Massoth said.
ENDS