Geology
Laysan is the second largest single landmass in the Northwestern Hawaiian Islands, after Sand Island at Midway Atoll. Laysan was created by coral growth and geologic upshift. The fringing reefs surrounding the island cover about 735 acres (2.97 km2). Lake Laysan, the 100-acre (0.40 km2), brown, hypersaline lake in the island's interior, has varied in depth over the decades. In the 1860s, the lake was at most 30 feet (9.1 m) deep, but by the 1920s it averaged 3–5 feet (0.91–1.5 m) deep, because of the buildup of sand that had been blown away in sandstorms. The best way to find fresh water on Laysan is to observe where the finches are drinking; the fresh water floats on the saltier water and accumulates around the shore. The tallest point on the island is at 50 feet (15 m) above sea level, on a large dune that covers much of the northern portion of the island.
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