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Diamond Head

Diamond Head is the name of a volcanic cone just east of Honolulu, and and for my money is one of the most famous visages in the world.  Hawaiians know the mountatin as Lēʻahi, most likely from “lae” meaning brown-ridged promontory plus ʻahi ‘tuna’ because the shape of the ridgeline resembles the shape of a tuna’s dorsal fin. Its English name was given by British sailors in the 19th century, who mistook calcite crystals embedded in the rock for diamonds.

As noted above, Diamond Head is part of the complex of cones, vents, and their associated eruption flows that are collectively known to geologists as the Honolulu Volcanic Series, eruptions from the Koʻolau Volcano that took place long after the volcano formed and had gone dormant. The Honolulu Volcanic Series is a series of volcanic eruption events that created many of Oʻahu’s well-known landmarks, including Punchbowl Crater, Hanauma Bay, Koko Head, and Manana Island in addition to Diamond Head.

Diamond Head, like the rest of the Honolulu Volcanics, is much younger than the main mass of the Koʻolau Mountain Range. While the Koʻolau Range is about 2.6 million years old, Diamond Head is estimated to be about 150,000 years old. The eruption that built up Diamond Head may well have been very brief, possibly as brief as days or weeks.   It was probably explosive, since when the cinder cone was originally formed, the sea level is thought to have been higher and the vent burst erupted over a coral reef. Another factor probably contributing to the eruption’s explosive nature was that rising magma would have come into contact with the water table. The eruption’s relatively brief length is thought to explain why the cone today is so symmetrical.

Diamond Head is a defining feature of the view known to residents and tourists of Waikīkī alike. The volcanic cinder cone is a United States State Monument. While part of it serves as a platform for antennas used by the U.S. government and is closed to the public, the crater’s proximity to Honolulu’s resort hotels and beaches makes the rest of it a popular destination.

The Hike

A 0.75 mile hike leads to the edge of the crater’s rim. Signs at the trailhead say that the hike takes 1.5–2 hours round-trip, and recommends that hikers bring water and flashlights. Although not difficult, the signs also say that the hike is not a casual one: the mostly unpaved trail winds over uneven rock, ascends 74 steps, then through a tunnel and up another steep 99 steps. Next is a small tunnel (hence the flashlight) to a narrow spiral staircase (about 30 steps) inside a coastal artillery observation platform built in 1908. From the summit above the observation platform both Waikīkī and the Pacific Ocean can be seen in detail.




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