formed. The Tonga-Kermadec Island arc would seem to be the result of such
phenomena, and in fact, there are hundreds of islands.
On October 18, 2002 we stopped the SONNE near the island of Ota where a
team of scientists landed to pick up some samples from the island’s recently active
volcano. Before we arrived, it was also on this island that about 50 young Tongans
had been isolated from the rest of the World during a period of a month for bad
behavior in the capital city of the Tongan kingdom.
During the FS SONNE cruise, about 20 submarine volcanoes (seamounts) were
sampled. Based on the samples recovered from the twenty edifices, six undersea
volcanoes were selected for further detailed investigations with deep-towed
vehicles to take video films and bottom photos. It was found that most of the
seamounts surveyed along the Tonga-Kermadec volcanic chain showed multiple
cones and variable (1–3 km in diameter) sized caldera that were usually a few
hundred meters deep. Only a small amount of these calderas were deeper, going up
800 m depth.
The composition of the volcanic rocks forming the Tonga-Kermadec volcanoes
ranges from basalt and dolerite to silica-enriched lava (diorite, tonalite, rhyodacite). However, most of the seamounts erupted felsic lava consisting of pumice and
andesite. Most of the caldera walls revealed an abundance of volcaniclastic
deposits composed of black and light colored scoria debris of pumice that had been
mixed with occasional sub-rounded sand to boulder-sized rock fragments. The
blocks are accidental, fragmented material that had been released during explosive
eruptions.
Another cooperative program was planned for June 2005, between the
Hawaiian Undersea Research Laboratory (HURL) of the University of Hawaii and
the University of Kiel (Germany) to carry out a diving expedition on several active
volcanoes in the northern part of the Tonga-Kermadec volcanic chain, between
25°S–177°W and 20°S–175°W. Thirteen submersible dives using Pisces IV and
Pisces V were scheduled to take place using the support vessel R.V. KA’ IMIKAIO-KAMALOA (called KOK for short).
The ship Ka’imikai-O-Kanaloa (meaning in Polynesian ‘‘searcher of the sea of
Kanaloaé and called K-O-K for short) was launched in July 1992 for SOEST
(School of Ocean Earth Science and Technology) in Honolulu and was operated by
the Hawaii Undersea Research Laboratory (HURL). KOK is the mother ship for
the submersibles Pisces 4 and 5. It is 224 feet long and has an ‘‘A’’ frame with a
30-ton hydraulic crane for launching the submersible. The ship carries a crew of
about 13 and has facilities for 15–20 visiting scientists and technicians. In addition,
the ship carried an ROV with a depth capability of 900 m.
We left Auckland, New Zealand on Sunday June 6, 2005 at 16 h and headed
north towards the Tonga-Kermadec volcanic arc. The wintery weather was calm
but cold during the first 2 days then it started to change so it became rough and
windy. The sea state varied between 4 and went up to 7, with winds of 25–70 km/
h. This type of weather lasted until June 16. At this point, the weather started to
ameliorate so normal diving could take place every day from June 16–22.
354
10 Subduction Zones
phenomena, and in fact, there are hundreds of islands.
On October 18, 2002 we stopped the SONNE near the island of Ota where a
team of scientists landed to pick up some samples from the island’s recently active
volcano. Before we arrived, it was also on this island that about 50 young Tongans
had been isolated from the rest of the World during a period of a month for bad
behavior in the capital city of the Tongan kingdom.
During the FS SONNE cruise, about 20 submarine volcanoes (seamounts) were
sampled. Based on the samples recovered from the twenty edifices, six undersea
volcanoes were selected for further detailed investigations with deep-towed
vehicles to take video films and bottom photos. It was found that most of the
seamounts surveyed along the Tonga-Kermadec volcanic chain showed multiple
cones and variable (1–3 km in diameter) sized caldera that were usually a few
hundred meters deep. Only a small amount of these calderas were deeper, going up
800 m depth.
The composition of the volcanic rocks forming the Tonga-Kermadec volcanoes
ranges from basalt and dolerite to silica-enriched lava (diorite, tonalite, rhyodacite). However, most of the seamounts erupted felsic lava consisting of pumice and
andesite. Most of the caldera walls revealed an abundance of volcaniclastic
deposits composed of black and light colored scoria debris of pumice that had been
mixed with occasional sub-rounded sand to boulder-sized rock fragments. The
blocks are accidental, fragmented material that had been released during explosive
eruptions.
Another cooperative program was planned for June 2005, between the
Hawaiian Undersea Research Laboratory (HURL) of the University of Hawaii and
the University of Kiel (Germany) to carry out a diving expedition on several active
volcanoes in the northern part of the Tonga-Kermadec volcanic chain, between
25°S–177°W and 20°S–175°W. Thirteen submersible dives using Pisces IV and
Pisces V were scheduled to take place using the support vessel R.V. KA’ IMIKAIO-KAMALOA (called KOK for short).
The ship Ka’imikai-O-Kanaloa (meaning in Polynesian ‘‘searcher of the sea of
Kanaloaé and called K-O-K for short) was launched in July 1992 for SOEST
(School of Ocean Earth Science and Technology) in Honolulu and was operated by
the Hawaii Undersea Research Laboratory (HURL). KOK is the mother ship for
the submersibles Pisces 4 and 5. It is 224 feet long and has an ‘‘A’’ frame with a
30-ton hydraulic crane for launching the submersible. The ship carries a crew of
about 13 and has facilities for 15–20 visiting scientists and technicians. In addition,
the ship carried an ROV with a depth capability of 900 m.
We left Auckland, New Zealand on Sunday June 6, 2005 at 16 h and headed
north towards the Tonga-Kermadec volcanic arc. The wintery weather was calm
but cold during the first 2 days then it started to change so it became rough and
windy. The sea state varied between 4 and went up to 7, with winds of 25–70 km/
h. This type of weather lasted until June 16. At this point, the weather started to
ameliorate so normal diving could take place every day from June 16–22.
354
10 Subduction Zones