Explore the Deep Sea
Expeditions
Hot facts
- The underlying rocks become more acidic from north to south of the basin, changing from basalt to andesite, to rhyolite.
Map of the Lau Basin seafloor from 18S° to 23°S and from 179°W to 175°W, showing the approximate locations of sites containing hot vents (red dots). Click for a larger map.
In pictures
- Discovering a new vent site makes up for bad weather.
- The lure of Lau: researchers want to understand why these sites differ — in the type of rock, in the chemistry of the fluids emitted by vents, and in the abundance of living creatures
Lau Basin study sites
A series of five expeditions is exploring the seafloor of the Lau Basin in the South Pacific. The first two expeditions concentrated on mapping the seafloor and identifying areas containing deep-sea hot (hydrothermal) vents. Later expeditions explored some of these areas in detail, and kept an eye out for other new vent fields.
From north to south
The major vent fields that have been found so far include the following.
- Site 1, Kilo Moana. This northern site was named after the ship used for the first two expeditions. The rocks here are basaltic. Three distinct areas contain active vents, including black smokers. Animals — such as seastars and anemones — are abundant.
- Site 2, Towcam. This site was named after a towed underwater camera. There are some vigorous vents at the northern end of the site, and a somewhat less active area to the south. Many animals have been seen in areas of diffuse flow (where vent fluid seeps out of cracks in the seafloor, rather than shooting out in a focused jet).
- Site 3, ABE. Another site named after a piece of equipment, in this case, a submersible vehicle. This site sits on andesitic (not basaltic) rocks. It has three separate venting areas, each lying more than 100m from the others. One is in an underwater valley, one along a steep slope, and the third on top of a small plateau. This site will be the primary focus for a lot of future research by scientists associated with the Ridge 2000 research program.
- Site 4, Tui Malila. Named for Tonga's late, great royal tortoise, this site was discovered in 2005. The largest site found in the area to date, it contains active smokers, areas of diffuse flow, and — unlike the sites further south — abundant life.
- Site 5, Mariner. A Japanese expedition located this site in late 2004 and noted that there weren't many animals here. When the remotely operated submersible Jason II visited in mid 2005, it too failed to find many signs of life. There are large columns (some over 20m tall) and active smokers, but almost none of the snails, worms or mussels found at the sites further north.
- Site 6, Vai Lili. No active smokers have been found at this site, though there are some areas of focused flow, where vent fluid up to 120°C is jetting out of the seafloor. Like the nearby Mariner site, there are very few animals.
What's in a name?
The expedition that finds a vent site gets to name it. This is the chain of reasoning that led to the naming of the Tui Malila site (pronounced two-ee-ma-LEE-la) by the third of five expeditions to the Lau Basin:
- Everyone felt lucky finding the site
- According to a Tongan on board, tortoises are considered lucky in Tonga
- A tortoise given to the King of Tonga by Captain Cook in the 1770s (it lived until 1965!) was called Tui Malila
Some of the other sites were named after some of the tools that helped scientists locate them.
