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Navassa is a small, isolated, tear-shaped oceanic island covering an area of approximately 5.2 km2 (2 mi2)or 1,344 acres, surrounded by nearly 570 square miles (364,800 acres) of submerged coral reef ecosystem waters. It lies at 18o 25’ N, 75o 02’ W in the Windward Passage, a channel between eastern Cuba and western Haiti that connects the Atlantic Ocean with the Caribbean Sea. Navassa is approximately 35 miles (50 km) southwest of the Tiburon Peninsula of Haiti, 137 miles (220 km)  north-east of Morant Point, Jamaica, and about 100 miles (161 km) south from the U.S. Naval Base at Guantanamo, Cuba. The Refuge includes a 12 mile radius of marine habitat around the island.

Map of Navassa Island
Map of Navassa Island (courtesy of the Perry-Castañeda Library Map Collection)
Navassa Island
Navassa Island - NASA NLT Landsat 7 (Visible Color) Satellite Image (Image: NASA)

Navassa may have formed as a small coral atoll. About 5 million years ago, these reefs began to emerge with an alteration of calcium carbonate sediments (aragonite) to calcium-magnesium carbonate rock (dolomite). Dolomite is a mineral which consists of calcium magnesium carbonate (CaMg(CO3)2) found in extensive beds as a compact limestone. Navassa is comprised of a raised dolomite plateau, surrounded by vertical cliffs nine to 15 meters high which extend downward 23-30 meters in depth to a gradually sloping submarine terrace. There are some shallower areas at the northwestern tip of the island (Collette et al., 2003), but most bottom depths adjacent to shore begin at 20 meters with a gradual depth increase to 40 meters. Depth increases are more pronounced beyond 40 meters, with depths up to 500 meters within 0.8 nautical miles of the north shore (Grace et al., 2001). Much of the nearshore substrate is coarse sand with broad areas of live bottom (corals, sponges, and algae), limestone rock, and rubble. The substrate on the eastern side of the island has a lot of cobble and hard bottom/pavement. In some areas, the cliffs are eroded to the point where large chunks, called "calves," have fallen off and rest on the terrace as large boulders.

the imposing cliffs of Navassa Island
The imposing cliffs of Navassa Island do not allow easy access to the Island (Photo: Keith Pamper/Shedd Aquarium)
The dock at Lulu Bay
The dock at Lulu Bay (Photo: U.S. Geological Survey)

The surface of Navassa is unsuitable for agricultural use. The land is mostly forested with exposed coral and limestone. There are patches of poisonwood trees and scattered cactus. About 10 percent of the island is covered with grasses. Mangroves and sandy beach habitats are completely lacking. Seagrass beds are extremely limited. There are no natural ports and landing is difficult and hazardous. The most common landing spot is Lulu Bay, a small cove on the southern side of the island.

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