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| Kermadec arc - deepsea research |  |
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Scientists at GNS, together with their
colleagues from various New Zealand and overseas institutions, have been
on a quest to discover, and then physically locate and chemically
characterize, submarine hot springs related to arc volcanoes. |
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These arcs
are curved chains of volcanoes generally convex towards an oceanic basin
and separated from it by a deep submarine trench . They mark convergent plate
boundaries and are the surface expression of magmatic systems that develop
as a result of the subduction of oceanic lithosphere.
There are generally 3 types of volcanic arcs: 1. Intra-oceanic arcs that have oceanic crust on either side (e.g., the Tonga-Kermadec arc) and which are almost entirely submarine, 2. Transitional, or island arcs that have developed along the margins of island chains (e.g., the Sunda arc), of which parts are submarine but most are subaerial, and 3. Continental arcs that develop along the margins of continents (e.g., the Andean arc), which are entirely subaerial. There are about 22,000 km of intra-oceanic and island arcs covering the surface of the Earth, most of which are concentrated in the Western Pacific region. There is about 7,000 km of intra-oceanic arcs with the Tonga-Kermadec arc offshore New Zealand the longest at 2,500 km. It is this arc, and its submarine volcanoes and associated hot springs, that has been the focus of GNS scientists and their colleagues since 1999. They have also been involved with surveys to do likewise along arcs offshore PNG, the Solomon Islands, and the Mariana arc north of The Philippines. Many of these submarine volcanoes are host to hot springs which discharge enormous quantities of metal-rich "black smoker" plumes into the oceans [link to cartoon showing a plume over a volcano]. It is at these sites that large copper, zinc, lead and even gold deposits are forming, unusual animals live, and which supply many of the necessary trace metals as the 'lifeblood' to the oceans. |
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