Diamond Head Hiking Tour

How The Crater Was Formed
     The pronounced seaward summit, deeply eroded ridges, and ovoid-shaped crater as evidence of Leahi's very dynamic geological history. The creation of Oahu began around 2.5 to 4 million years ago with volcanic eruptions from 2 shield volcanoes. A period of extensive erosion followed, leaving the Koolau and Waianae Mountain Ranges as the remnants of these volcanoes.

     After about 1.3 million years of volcanic inactivity, the southeastern end of the Koolau Range erupted. These eruptions occurred under the ocean, where the magma was broken down into ash and fine particles by the water and steam. Blown into the air, these particles were cemented together into a rock called tuff which created tuff cones, such as Leahi.

     Leahi is believed to have been formed about 300,000 years ago during a single, brief eruption. The broad crater covers 350 acres with its width being greater than its height. The southwestern rim is highest because winds were blowing ash in this direction during the eruption. Since the eruption, the slopes of the crater have been eroded and weathered by rain, wind, and the pounding of the sea. A coral reef now protects the seaward slopes of the crater.

     Today, Leahi (Diamond Head) is the most recognized landmark in Hawaii. It was designated a National Natural Landmark in 1968 as an excellent example of a tuff cone.

Environment
     The semi-arid climate, the steep rocky slopes, and the shallow soil of Diamond Head support mostly low shrubs and herbs. Botanists believe that the crater was once covered by a dryland forest, but only a few native Hawaiian species remain. Rainwater collects on the crater floor in the winter, creating a small lake that was frequented by native ducks, coots, and gallinules until the early 1900s.

     Most of the plants and animals you see in the crater today were introduced to Hawaii after the 1800s. Dominant plants are the kiawe, a relative of the mesquite, and koa haole. Both of these plants were brought in as cattle feed and have adapted well to the hot, dry conditions. You may see some of the common introduced birds, such as cardinals, doves, and sparrows.

The Early History
     It is said that Hiiaka, sister of the fire goddess Pele, gave Leahi its name because the summit resembles the forehead (lae) of the ahi fish. Another translation is "fire headland" and refers to the navigational fires that were lit at the summit to assist canoes traveling along the shoreline. The heiau (temple) built on the summit was dedicated to the god of wind as protection against strong updrafts that could put out these navigational fires. Today, the Diamond Head Light, built in 1917, provides a visual aid for navigation.

     In the late 1700s, Western explorers and traders visited Leahi and mistook the calcite crystals in the rocks on the slope of the crater for diamonds. Thus, the name Diamond Head came into common useage.



Military History
     With its panoramic view from Koko Head to Waianae, the summit of Diamond Head was an ideal site for the coastal defense of Oahu. In 1904, Diamond Head was purchased by the Federal government and designated for military use. Fortification began in 1908 with the construction of gun emplacements and an entry tunnel through the north wall of the crater from Fort Ruger known as the Kapahulu Tunnel.

     Batteries were built to house the coastal artillery. A total of 5 batteries were built at Diamond Head Crater: Harlow (1910) on the northern exterior, Dodge and Hulings (1913) which tunnel through the eastern crater wall, Birkhimer (1916) which is largely below ground inside the crater, and Battery 407 (1943) which tunnels through the southern wall.

     Fire Control Station Diamond Head was built at the summit between 1908-1910 and housed instruments and plottings rooms to direct artillery fire from several batteries.

     Additional coastal defense was provided by long range guns installed on the outer slopes and rim of the crater around 1915. Diamond Head was prepared to defend Oahu from attack but no artillery was ever fired during a war.

     The military features of Diamond Head are part of the Fort Ruger Historic District.

1. The trailhead at the parking lot is located on the crater floor at an elevation of about 200 feet (61 m).
2. The concrete portion of the trail was recently installed to reduce trail erosion. The former pistol ranges are marked by earthen berms visible along the lower section of the trail.
3. The dirt trail conforms to the 1908 trail alignment and consists of numerous switchbacks up the steep interior slope.
4. Concrete Landing/Lookout. This foundation held a winch and cable to lift materials from the crater floor to this point.
5. Steep stairway of 74 concrete steps leading into the first tunnel.
6. Passage through a lighted 225-foot long, narrow tunnel.
7. Second stairway consisting of 99 steep steps. The cross-beams above the stairway supported camoflaging.
8. At the top of the stairs is the entry to the lowest level of Fire Control Station Diamond Head which housed the observation equipment for Fort DeRussy at Waikiki.
9. The lighted spiral staircase accesses the 4 levels of the Fire Control Station. Go up the 52 stairs to the third level where the mounts for the observation equipment are still present.
10. Exit to the exterior of the crater through slits once covered with metal shutters. Note the rock and concrete that camouflage the structure on the seaward side.
11. The 54 metal stairs replaced the ladder to the summit in the 1970s for hiker safety.
12. The summit of the crater and the uppermost level of the Fire Control Station are at an elevation of 761 feet (232 m). Bunkers along the crater rim were built in 1915.