Diamond Head

Diamond Head is the name of a volcanic tuff cone on the Hawaiian island of Oʻahu and known to Hawaiians as Lēʻahi, most likely from lae 'browridge, 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 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 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 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 Koʻolau Mountain Range. While the Koʻolau Range is about 2.6 million years old, Diamond Head is estimated to be about 200,000 years old and inactive for 150,000 years.

The eruption that built up Diamond Head was probably very brief, lasting no more than a few days. 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.

A nearby eruption that took place at about the same time as the Diamond Head eruption was the eruption that built the Black Point lava shield. Since the type of eruptions that built Diamond Head tend to be monogenetic, geologists don't believe that Diamond Head will erupt again.

History

The interior and adjacent exterior areas were the home to Fort Ruger, the first United States military reservation on Hawaii. Only a National Guard facility and Hawaii State Civil Defense remain in the crater. An FAA air traffic control center was in operation from 1963 to 2001.

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 United States 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.

A 0.75-mile (1.1-km) 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. 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 lighted tunnel to a narrow spiral staircase (43 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. It is a short but steep hike – it is a 560 ft. elevation gain for a total elevation of 762 ft. There is a water fountain near the bathrooms at the foot of the trail in case you want to hydrate before the hike or fill an empty bottle. The park closes at 6pm and signs posted indicate that you are not allowed to head up the trail after 4:30pm.

National Natural Landmark

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 (including the crater’s interior and outer slopes), 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.

Popular hiking destination

When vegetation and birds were introduced in the area in the later part of the 1800s, the trail going to Diamond Head soon became popular.

In 1908, the trail to the summit was built as part of the island’s coastal defense system. The 0.8 mile hike is considerably a moderate climb to seasoned hikers but could be a strenuous and steep climb to those who aren’t. It usually takes an hour to get to the summit where you will have a view of the entire Oahu leeward coast.

• Various views of Diamond Head

• Diamond Head cone seen from the coast off Waikīkī

• View from Rocky Hill, which resides over Punahou School

• Diamond Head peak from Kapiolani Park

• Diamond Head seen from Waikīkī in the 1800s

• Waikiki Beach facing Diamond Head, 1958

• Aerial view of the cone, and the Kahala and Kaimuki neighborhoods

In popular culture

Diamond Head is widely used for commercial purposes. Many souvenirs from Hawaii and surf shop logos around the world bear the volcano's distinctive silhouette.

A 1975 televised game show, The Diamond Head Game was set at Diamond Head. Several episodes of the 1980s television drama Magnum, P.I. featured the volcano. The volcano features in various screenshots in Hawaii Five-0.