Marine Atlas: Maximizing Benefits for Solomon Islands

SMOKE UNDER WATER, FIRE IN THE SEA: TECTONIC ACTIVITY Solomon Islands is located on the Pacific Ring of Fire, a highly active tectonic zone. Above water, this tectonic activity means that Solomon Islands 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 contribute to Solomon Islands’ rich marine biodiversity. These features also deposit minerals, making them an attractive, if conflicting, target for deep-sea mining exploration and extraction.

The Solomon Islands are relatively young in geological terms and began forming when the south-west boundary of the Pacific plate came into contact with the Australian plate around 55–40 million years ago (Ma). The islands were formed through three main ge- ological processes. The north coasts of San- ta Isabel, Malaita and Ulawa were formed around 4 Ma through obduction (a process in which the sea floor is forced upward) and is geochemically similar to the Ontong Java Plateau (Petterson et al., 1999). Choiseul and Guadalcanal have characteristics typical of islands originating from a mid-ocean spreading centre process, whereas the island of Makira has a mix of characteristics from both types (Petterson et al., 1999). Volcanic activity also formed many of the islands and occurred in two distinct phases: first, from 62 to 24 Ma and second, from 7 Ma to present day (Petterson et al., 1999). These volcanic processes helped shape the island arc seen today. This tectonic activity shapes not only the islands of Solomon Islands but also its undersea landscape. In these tectonically active areas of sea floor, features known as hydrothermal vents are often found. These are fissures in the Earth’s surface from which geothermally heated water (up to 450°C) escapes. 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 dis- solved in the vent fluid. The black and white smokers and their mineral-rich warm water attract many organisms and have unique biodiversity. Chemosynthetic bacteria and archaea,

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

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

The Pacific region is one of the most tecton- ically active regions in the world. The Pacific Ring of Fire, stretching clockwise from New Zealand all the way around to South Amer- ica, is home to around 90 per cent of the world’s earthquakes. Pacific Island coun- tries such as Solomon Islands, which lay between the Pacific and Australian tectonic plates, are subject to volcanic and seis- mic activity. The activity affecting Solomon Islands is primarily centred on the southern side of its islands at the edge of the large ocean trenches—the New Britain, South Solomon and North New Hebrides Trenches. This means that many earthquakes are fo- cused either near or directly on the main is- lands of Solomon Islands. Numerous magni- tude 6 earthquakes or above have occurred in this region, with several of the larger ones measuring over magnitude 8. Earthquakes can, under certain circumstances, gener- ate tsunamis. For example, in 2015 an 8 magnitude earthquake hit Solomon Islands, generating a small tsunami that killed nine people and caused major damage to coastal

infrastructure (see also chapter “Voyage to the bottom of the sea”).

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As the map shows, Solomon Islands’ wa- ters harbour not only numerous deep-sea hydrothermal vents, but also nine volca- noes. At least four of these (Kavachi, Savo, Simbo and Tinakula) are still active. Tinakula is highly active and erupts andesitic ash almost every week. Its last large eruption was in 1985. Kavachi is a shallow submarine volcano, which forms a temporary island during its eruptive phase, an event that oc- curs every 4–8 years according to the World Organization of Volcano Observatories. Savo and Simbo have not had any major erup- tions in recent years, but still remain active. Tectonic activity is a key to the creation of the Pacific Islands and atolls, many of which sit upon active or inactive volcanoes (see also chapter “Underwater mountains”).

When a team of scientists from the University of Rhode Island explored the sea floor north-west of the Galap- agos Islands in 2015, they made an unexpected discovery. At a hydrother- mal vent they found large numbers of perfectly fine eggs very close to the boiling water. The eggs were those of deep-sea skate (relatives of sharks and rays), which use the hot water from vents to accelerate the develop- ment of the embryos. While this may seem strange, it is not uncommon. Several species of shark swim straight through the bubbling hot water in the crater of the submarine Kavachi vol- cano (see also chapter “Underwater mountains”). This impressively shows that the presumably toxic environ- ment around vents in fact supports a whole community of life.

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both single-celled organisms, form the base of a food chain supporting diverse organisms, including giant tube worms, clams, limpets and shrimp. Some scien- tists even suggest 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 cop- per), cobalt and rare earth metals occur in high concentrations in vent systems, which are increasingly being explored for their mineral resources (see also chapter “Underwater Wild West”).

MAXIMIZING BENEFITS FOR SOLOMON ISLANDS

SUPPORTING VALUES

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