Lifou
- ISS006-E-5822
- 07 December 2002
- 23:49 UTC
Running parallel to the island of Grande Terre, and located around 80 km to the east, is a submarine ridge known as the Loyalty Ridge — one of the major geological features of the sea floor in the Pacific southwest. Extending for over 1,000 km from northwest to southeast, the ridge is flanked by the deep waters of the South Loyalty Basin (up to 2,000 m deep) on the west and by the volcanic New-Hebrides subduction zone on the east. Formed by a series of emergent and submerged seamounts the Loyalty Ridge gives rise to the large islands of the Loyalty Islands group as well as to a number of smaller islands and reefs, including Beautemps-Beaupré Atoll, Ouvéa, Walpole Island, Récifs de l'Astrolabe, Petrie Reef, Durand Reef, and the Banc de L'Orne. The largest emergent feature of the Loyalty Ridge is the island of Lifou.
Lifou is the largest of the Loyalty Islands (Îles Loyauté), covering 1,207 km² in area and measuring 63 km in length (southwest to northeast) and up to 30 km across. The island is located 46 km northwest from Maré and some 90 km northeast from the outer barrier reefs of Grande Terre.
Lifou is a raised coral platform formation. The interior is flat throughout, meeting the shore in low cliffs, and represents the former lagoon floor that now stands at 30 m to 40 m above sea level. The uplift along the Loyalty Ridge is asymmetric, with greater uplift towards to the southeast — the island of Maré rises to 138 m above sea level, Ouvéa, farther to the northwest, is only raised on its eastern side, while reefs further north such as Beautemps-Beaupré and Astrolabe remain at, or below. sea level. Terraces, platforms and undercut cliffs are also in evidence around the shores of Lifou and are signs of major sea level changes in the past.
image: earth sciences and image analysis laboratory, nasa johnson space center
