Diamond Head is a volcanic tuff cone on the Hawaiian island of Oahu and known to Hawaiians as Lēahi. The Hawaiian name is most likely derived from lae plus ahi 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 on the adjacent beach for diamonds.
Geology
Diamond Head is part of the system of cones, vents, and their associated eruption flows that are collectively known to geologists as the Honolulu Volcanic Series, eruptions from the Koolau Volcano that took place long after the volcano formed and had gone dormant. These eruptive events created many of Oahu's well-known landmarks, including Punchbowl Crater, Hanauma Bay, Koko Head, and Mānana Island in addition to Diamond Head. Diamond Head, like the rest of the Honolulu Volcanic Series, is much younger than the main mass of the Koolau Mountain Range. While the Koolau Range is about 2.6 million years old, Diamond Head is estimated to be about 500,000 to 400,000 years old.
History
Known as Lēʻahi in Hawaiian, the mountain in 1825 was given the name Diamond Hill by British sailors who discovered sparkling volcanic calcite crystals in the sand and mistook them for diamonds. This is reflected in another local name, Kaimana Hila. The name later became Diamond Head, with head being shortened from headland. The interior and adjacent exterior areas were the home to Fort Ruger, the first United States military reservation on Hawaii. Only Battery 407, a National Guardemergency operations center, and Birkhimer Tunnel, the Hawaii State Civil Defense Headquarters, remain in use in the crater. An FAAair traffic control center was in operation from 1963 to 2007.
Tourism
Diamond Head is a defining feature of the view known to residents and tourists of Waikīkī, and also a U.S. National Natural Monument. The volcanic tuff cone is a State Monument. While part of it is closed to the public and serves as a platform for antennas used by the U.S. government, the crater's proximity to Honolulu's resort hotels and beaches makes the rest of it a popular destination.
In 1968, Diamond Head was declared a National Natural Landmark. The crater, also called Diamond Head Lookout, was used as a strategic military lookout in the early 1900s. Spanning over 475 acres , it served as an effective defensive lookout because it provides panoramic views of Waikīkī and the south shore of Oahu. The Diamond Head Lighthouse, a navigational lighthouse built in 1917 is directly adjacent to the crater's slopes. In addition, a few pillboxes are located on Diamond Head's summit.