Maps and Imagery
Click on the links below to download shapefiles which correspond to the French
Frigate Shoals detailed habitat class and aggregated cover imagery. Each zipped
shapefile consists of 6 separate files, with the same root name and .dbf, .prj,
.sbn, .sbx, .shp, and .shx extensions.
French Frigate Shoals: Detailed habitat shapefile (137 MB)
French Frigate Shoals: Habitat cover shapefile (113 MB)
Download a .ZIP file which contains the Arc and PCI legend files (.avl and
.rst extension) for the NWHI maps. When added to your Arc or PCI project, these
files will cause the vector colors to match the geotiffs.
Description and History
Approximately 1500 km ESE of Midway Atoll and 700 km WNW of Kaua'i lies French
Frigate Shoals at longitude 166 degrees 10 minutes W and latitude 23 degrees
45 minutes N. French Frigate Shoals was formed approximately 13.8 million years
ago as the Pacific Plate crossed over a "hotspot" in the earth's
mantle. The Pacific Plate continues to move WNW at about 9 cm each year.
French Frigate Shoals appears to be the remnant portion of an approximately
27 km-long crescent-shaped atoll. This atoll protects a 727 sq.-km shallow
lagoon that is from 2 to 10 km wide. La Perouse Pinnacle, located at the southwest
corner of the lagoon, is the major visual landmark in the area at French Frigate
Shoals. La Perouse Pinnacle is the dense rock remnant of the central lava tube
that formed the volcano. Everything else surrounding this central tube has
been eroded. Numerous sand islets dot the lagoon area of French Frigate Shoals.
Waves and currents constantly change the size and shape of these sandy islets.
French Frigate Shoals is the most important breeding and nesting area for
the Hawaiian green sea turtle in the entire Hawaiian archipelago. As much as
80 percent of all green sea turtles in the entire Hawaiian archipelago return
to French Frigate Shoals to nest and breed. The numerous shoals and sand bars
offer perfect habitat in which these ancient creatures can reproduce. French
Frigate Shoals also is home to millions of birds. On Tern Island alone, an
estimated 1.5 million Sooty Terns nest and breed.
French Frigate Shoals presents a contrast in seabed habitats. Vast areas of
many square kilometers are devoid of reef coral development, while other areas
are among the richest reefs observed in the Hawaiian archepelago. Sand, rubble,
uncolonized hardbottom and crustose coralline algae dominate the lagoon and
the windward reef. It appears that severe North Pacific Swells and NW Trade
Wind Swells suppress reef coral development in major areas of the atoll. Large
amounts of sand constantly move with shift ing wave patterns and currents along
the lagoon floor, periodically burying and uncovering large areas. As a result,
the sand islands constantly change size and shape. In addition, the NE trade
winds prevail throughout the year and drive lagoon circulation. The average
wind velocity is 12 knots.