Diamond Head is probably the most iconic landmark of Oahu. You see it everywhere – from the beach, from your hotel room, on post cards, on travel brochures, in movies and television shows. It is 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 (Diamond Head) came from British sailors in the 19th century who mistook calcite crystals embedded in the rock for diamonds. It is a product of the Honolulu Volcano Series.
Diamond Head was built by hydromagmatic explosions that ripped through 200,000 year old coral reefs and Ko‘olau basalt. As a result, large pieces of coral and basalt are mixed in the tuff and magmatic debris of the cone. The eruption that built up Diamond Head was probably very brief, lasting a few days to a month. The eruption’s relatively brief length is thought to explain why the cone today is so symmetrical. Although Diamond Head is listed as a dormant volcano, it is considered monogenic, meaning it was a one-blast wonder and will probably never awaken again. It was designated a National Natural Landmark in 1968 as an excellent example of a tuff cone.
Diamond Head has quite an interesting military history. The early Hawaiians lit navigational fires at the summit to guide canoes traveling along the shoreline. But when Hawaii became a U. S. territory in 1898, the government had a different kind of “fires” in mind. Because of its height and proximity to the ocean, it is a perfect defense position from possible land and/or sea invasion. The U. S. federal government purchased Diamond Head along with some of the surrounding area for military development in 1904 for $3,300. A fort was established in 1906 called Diamond Head Reservation. In 1909 it was renamed Fort Ruger after General Thomas H. Ruger, a union general in the Civil War. He served from 1871 to 1876 as the superintendent of the United States Military Academy at West Point. The first battery at Fort Ruger was named Battery Harlow, and was armed with eight 12-inch mortars. A network of tunnels was carved into the mountain, and cannon emplacements were placed atop the crater rim along with observation posts and bunkers.
Fort Ruger eventually included these batteries:
Battery Harlow (1910-1943); Battery Birkhimer (1916-1943); Battery Granger Adams (1935-1946); Battery Dodge (1915-1925); Battery Mills (1916-1925); Battery 407 (1944); Battery Hulings (1915-1925); and Battery Ruger (1937-1943).
A list of armaments in place at Fort Ruger in 1941 shows:
- Battery Harlow – 8 x 12″ M1890M1 Mortars
- Battery Birkhimer – 4 x 12″ M1890M1 Mortars
- Battery Granger Adams – 2 x 8″ on railway barbette carriages, fixed (Black Point)
- Battery Ruger – 2 pairs of Panama Mounts
- 4 AA Gun Batteries
Fort Ruger was reinforced during World War II, though the guns were never fired during the duration of the war. After the war they were dismantled. Today few of the original buildings survive. The most striking are three sets of stone structures that mark former gates to the fort.Despite being listed on the National Register of Historic Places, portions of the site are still used for training by the Hawaii National Guard.
Today Diamond Head is used mostly as a hiking trail. The trail to the top is 1.3 km (.8 mile) and takes 1 ½ – 2 hours for a safe and leisurely round-trip hike. It is steep terrain and stairs though, so not for everyone. This trail not only has fantastic views, you can see the bunkers and infrastructure from the military fortification. This brochure gives more history and a detailed map of the hike. It is very interesting.
Here is a zoom in/out 360 degree rotation showing the Diamond Head Lighthouse on the “other” side of the volcano. I would like to live there!
I tried to find more information on what the native Hawaiians might have used Diamond Head for besides navigational fires, but came up empty handed.
For those of you interested in military history this website is very interesting and has several really good pictures. It is one of my credits for this post.
For Friday night entertainment and challenge, here come the riddles. We are looking for four volcanoes and one geology term.
1) Titaness + image. Answer: Theia Mons on Venus. Theia, also called Euryphaessa “wide-shining”, is a Titaness and was said to be the mother of Helios, the Sun, Selene, the Moon, and Eos, the Dawn. Sissel, 2 points.
2) This field lies on an island of exiles that was once fortified against the French. Clue: It’s not in Vietnam. Answer: The Hainan Dao volcanic field. Hainan was a place that many Chinese dynasties sent their political exiles. China fortified it against France during the Sino-French war. Sissel, 1 point.
3) They couldn’t get a three-way going, so they just split up. Answer: Aulacogen, a failed rift at a triple junction. inannamoon667, 2 points.
4) High tides, super novas, and warring Frenchmen… look North! Answer: North Mountan was an ancient fissure volcano that formed during the opening of the Atlantic, and now forms the East bank of the Bay of Fundy, in Nova Scotia. The Bay of Fundy has the biggest tides in the world, and the Acadian Civil War was fought between two French governors of the colony. Inannamoon667, 2 points.
5) Just skip this one… You’ll come back to it! Answer: Boomerang Seamount located northeast of Amsterdam Island, France. Bobbi, 2 points.
6 Shérine France
6 Evan Chugg
2 Stephanie Alice Halford
1 Diana Barnes