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Subject: Fw: New eruption-Kavachi volcano,Solomon Islands
From: "Erich Kern" ekern@.........
Date: Fri, 26 May 2000 17:14:28 -0700

Speaking of volcanoes, here's a forward of an item on the volcano mail list.
Erich Kern

New eruption at Kavachi volcano, Solomon Islands
From: Dan Shackelford 

Observations in late May 2000 by NZ geologists showed that the famous
Kavachi submarine volcano in the Solomon Islands is once again erupting,
with spectacular bomb ejections and possible island formation.


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 its 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 peak of the volcano was forming a sandy ashen beach two metres below
sea level with regular violent bomb-like eruptions.

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

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.

John Callan
Communications Co-ordinator
Institute of Geological & Nuclear Sciences Limited
Ph: 04-570-1444 (reception), 04-570-4732 (direct)


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