French Frigate Shoals
- ISS006-E-37912
- 12 March 2003
- 20:07 UTC
The French Frigate Shoals are located at roughly the center of the entire Hawaiian Archipelago — situated around 1,300 km northwest from Honolulu and 160 km northwest from Necker Island. They are the largely submerged remains of a former crescent-shaped atoll, enclosing a 727 km² shallow lagoon that is up to 34 km across.
The lagoon contains two exposed volcanic rocks and 12 low sandy islets, with a total land area of 0.25 km². Dominated by algae, rubble and sand deposits, the lagoon also contains numerous pinnacles, mounds, and platforms. Islets around the outer perimeter include: Shark Island, Tern Island, Trig Island, Skate Island, Whale Island, and Disappearing Island. Islands emerging from the central ridges include: Round Island, Mullet Island, Bare Island, East Island, Gin Island and Little Gin Island. Located southwest of the lagoon centre stands the striking feature of La Perouse Pinnacle, a 36 m tall lava tube — all that remains of the volcano that formed the Shoals some 13 million years ago. La Perouse Pinnacle is just discernable in the above image.
Tern Island, at 12 ha in area, is the largest of the islands. Its appearance is somewhat like that of an aircraft carrier, with a runway built over and extending beyond the natural boundaries of the island. The 945 m runway was constructed in 1942, as an emergency landing strip and refueling stop, by erecting a sea-wall and then back-filling with material from coral dredging (areas where dredging was carried out around Tern Island can be seen in the high-resolution image). Currently, the US Fish & Wildlife Service maintains a field station on the island.
Coral reef development at the shoals is influenced by strong Pacific swells from the north and northwest, resulting in large areas being devoid of coral cover. However, in more protected areas coral cover is abundant and diverse, representing some of the richest coral reefs to be found in the Hawaiian archipelago.
The French Frigate Shoals are the most important breeding and nesting area for the Green Turtle (Chelonia mydas) in the entire Hawaiian archipelago — with as much as 80-90 percent of all Green Turtles to be found in Hawaiian waters returning to the French Frigate Shoals to nest. The small sandy islets provide habitat for millions of seabirds. On Tern Island alone, an estimated 1.5 million Sooty Terns (Sterna fuscata) nest and breed. Also found at the shoals is the largest breeding colony of the highly endangered Hawaiian Monk Seal (Monachus schauinslandi).
image: earth sciences and image analysis laboratory, nasa johnson space center
