Marine Atlas: Maximizing Benefits for Fiji


Fiji is located on the Pacific Ring of Fire, a highly active tectonic zone. Above water, this tectonic activity means that Fiji is under threat from possible earthquakes and tsunamis. Underwater, the tectonic activity produces magnificent underwater volcanoes and hydrothermal vents which, in turn, spawn unique complex but fragile ecosystems that con- tribute to Fiji’s rich marine biodiversity. These features also deposit minerals, making them an attractive, if conflicting, target for deep-sea mining exploration and extraction.

There are still many mysteries around sea-floor hydrothermal vent systems, with their complicated biological, chemical and geological relationships. Only by exploring, recording and monitoring deep- sea hydrothermal systems is there a chance to protect them and the benefits they provide. Hydrothermal vents are fissures in the Earth’s surface from which geothermally heated water (up to 450°C) escapes. Vents are commonly found in volcanically active areas, such as areas between tectonic plates. Under the sea, hydrothermal vents may develop black or white smokers. These roughly cylindrical chimney structures can reach heights of 60 metres, forming from either black or white minerals that are dissolved in the vent fluid. The black and white smokers and their miner- al-rich warm water attract many organisms and have unique biodiversity. Chemosynthetic bac- teria and archaea, both single-celled organisms, form the base of a food chain supporting diverse organisms, including giant tube worms, clams, limpets and shrimp. Some scientists even sug- gest that life on Earth may have originated around hydrothermal vents. Along with their unique biodiversity, these vents are also a hotspot of minerals. Massive sulfides (including gold and copper), cobalt and rare earth metals occur in high concentrations in vent sys- tems, which are increasingly being explored for their mineral resources (see also chapter “Under- water Wild West”). As the map shows, Fiji’s waters harbour not only numerous deep-sea hydrothermal vents, but also three inactive volcanoes: Nabukelevu on Kadavu Island, Koro Island and Taveuni Island. These volca- noes have been dormant for several hundred years, with the last known eruption (Nabukelevu) occurring in 1660. The island of Rotuma does not have an active volcano, but is also volcanic in origin.

The Sully Vent in the north-eastern Pacific Ocean provides an example of the diverse communities around hydrothermal vents.

3D vents

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R i n g

In 2016, 16,000 online viewers from around the world watched a unique event in Fiji. It wasn’t the rugby finals at the Rio Olympics or the World Rugby Sevens Series—both won by Fiji! Nevertheless, it was an important event for Fiji. It took place in the Northern Lau Basin, at the bottom of the ocean, filmed by a robot for spectators’ viewing pleasure. The robot live-streamed a visit to the hydro- thermal vent field at the Niua volcano, which lasted more than 48 hours. This way, viewers could witness the exploration of this unique underwater world first-hand. At the same time, the exploration team reconstructed the vent site in 3D using virtual reality tech- nology, allowing scientists all over the world to study this unknown environment without having to leave their labs (Schmidt, 2016).

E q u a t o r

Tectonic activity is key to the creation of the Pacific Islands and atolls, many of which sit upon active or inactive volcanoes (see also chapter “Underwater mountains”). But where does all the heat fuelling vents and vol- canoes come from? The Pacific region is one of the most tectonically active regions in the world. The Pacific Ring of Fire, which stretches clockwise from New Zealand all the way around to South Ameri- ca, experiences around 90 per cent of the world’s earthquakes. Pacific Island countries such as Fiji are on the south-western edge of the Pacific tec- tonic plate and are therefore subject to volcanic and seismic activity. The activity affecting Fiji is primarily centred on and around the Lau Ridge to the south- east of the main islands. Numerous earthquakes of magnitude 6 and above have occurred in this region, with several of the larger ones measuring above magnitude 8. A smaller number of earth- quakes happen to the immediate north, west and south of the islands. Earthquakes can, under certain circumstances, generate tsunamis. The most de- structive of these occurred in 1953, when an earth- quake south-east of Suva generated a tsunami that caused particular damage to areas not protected by barrier reefs (see also chapters “Still waters run deep” and “Voyage to the bottom of the sea”).

Who would have thought deep-sea geology could be a spectator sport too!

Many Anomuran crabs attached to a hydrothermal chimney at 2,397 metres depth.




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