The Volcanic Landmarks of Oahu, Hawaii – Part 1, Diamond Head

Waikiki twilight with Diamond Peak in the background. Photo by Christopher Chappelear via Flickr (CC-BY).

Waikiki twilight with Diamond Head in the background. Photo by Christopher Chappelear via Flickr (CC-BY).

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. Image by ProveIt (Wikipedia, CC-BY-SA).

Diamond Head. Image by ProveIt (Wikipedia, CC-BY-SA).

This picture is from Fort Desoto but is the same mortar as was installed on Diamond Head although the gun mounts were a little different (Mikereichold, Wikipedia, CC-BY-SA).

This picture is from Fort Desoto but is the same mortar as was installed on Diamond Head although the gun mounts were a little different (Mikereichold, Wikipedia, CC-BY-SA).

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.




Old gatehouse and current signpost, Fort Ruger, Honolulu, Hawaii. Photo by Joel Bradshaw (Wikimedia Commons).

Old gatehouse and current signpost, Fort Ruger, Honolulu, Hawaii. Photo by Joel Bradshaw (Wikimedia Commons).

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.


Tunnel into Diamond Head Crater, Ft. Ruger, Honolulu, Hawaii. Photo by Joel Bradshaw (Wikimedia Commons).

Section of Battery Harlow. Image and copyright by

Section of Battery Harlow. Image and copyright by

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.


Other credits:,_Hawaii



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. 

Score board
22 Sissel
13 KarenZ
10 Inannamoon667
8 Kelda
6 Shérine France
5 Dinojura44
6 Evan Chugg
2 Alison
2 Bobbi
2 Stephanie Alice Halford
2 Agimarc
1 Diana Barnes
1 Edward
1 mikegrimsvotn


221 thoughts on “The Volcanic Landmarks of Oahu, Hawaii – Part 1, Diamond Head

      • Of late, I have been playing a post zombie appocolypse game that we had given up on before. At the time we abandoned it, it was filled by snot nosed wannabe uuber kids who were dead set on PVP. It was pretty frustrating spending hours lurking around the town dodging zombies only to have some punk assed wannabe sniper take you out. Now that we can lease a server its pretty cool dinking around against the AI zombies as a group. One of the things they added was a “super zombie”. Two of my cohorts ran into him by accident. Bugger stands about 9 feet tall and regens health as fast as you shoot it. Brim unloaded on it with a PKM while Git was hitting it with consecutive 12 guage rounds. It ate them. This evening we went to find the one at the airport since I had yet to see one. Git was spotting from the treeline as I was tearassing up and down the runway in a truck. I passed it about three times, but dared not stop since I had about 60 to 80 zombies in tow, shambing after me.

        • All games have a background “engine” that drive the events inside the game. In First Person Shooters, (aka “Ego Shooters”) the entire dynamics for the environment are handled by the game engine. The engine deals out the damage to the items in the game, and handles the physics and dynamics of how the stuff reacts to different forces. Some players take delight in fiddling around with this inside the game environment. One thing we discovered in one of the Battlefield series is that forklifts reacted to explosives, but once destroyed, the model of the forklift did not turn into a collection of broken parts and remained relatively intact, and still retained it’s mass. We spent many hours seeing how far we could launch the forklifts with concise placement of the in-game C4 sticks.

          There are some videos of other players using the quirks of different game dynamics out on youtube. In one I saw a player ricochet through a city by bouncing off of the buildings after using a rather forceful hitbox iteration. (Hit Boxes are a simplified model of an item/player in the game. The simplified model is used to lessen the calculation load on the engine and to make the game have smoother play. When you get to low framerates most players get very frustrated and give up on a game)

          In that zombie game I have been playing, the drivable vehicles have a pretty screwed up hitbox and you can not jump up on top of them. I had one parked on the side of a hill and tried to jump up on it and the diagonal hitbox launched me up into a tree. Luckily, the game client and server detected an error and I got disconnected. Previous implementations of the game have just lofted you above the tree line and then drop you to your death, loosing all of the gear that you had accumulated. (which is the basis of the game, you initially spawn in with nothing and have to survive by dodging/killing zombies and finding food and weapons by rummaging around the abandoned towns and buildings.)

          BTW, here is the blue beastie that Brim and Git got wasted by. There is a normal zombie behind him for size comparison. The game map is a Colorado type landscape.

          As best I can tell, this critter fills the “Tank” role from Left for Dead. Ultra hard to kill and deals out enormous damage when it attacks. As I mentioned, Brim emptied his AKM into it while Git was dumping 12 gage round after round into it. There are no attachable explosives in this game, so doing a suicide buggy into it is impossible. Reportedly, some other player managed to kill one by dumping two C-mags into one. (akin to a squad assault weapon)

          • That’s about right. Much of the oddball stuff you see in that video actually do show up in games from a buggy implementation of reality. The full auto pump action shotgun with no reloading is a prime example.

            My tendency is to try and get up on roofs. This made a few of my clan-mates to refer to me as the “roof monkey” since I usually tossed the games version of explosive packets on the vehicles driving by as they came to capture a nearby zone. I woundn’t set them off until they actually got to the flag and were pretty confident that they had secured the area. Doing so sort of doubles the piss off.

            In the BF series of games, since I am not a “twitch kiddie” I usually tried to find ways to get the opponent to kill themselves. I found that the tank mines pretty closely matched the size of the hatches on the tank model and would place one there so that it blended in. Once the tank starts to move, the mine goes off. We called it “locking” vehicles. That way while you are over capturing a control point, an enemy can’t come in and hop into the nearby tank and wipe out your whole squad.

    • Before anyone gets on a rant about the sanctity of “Native Americans”, Clovis was here first. They had an unfortunate run-in with the Younger Dryas, and the later people who came via Beringia took advantage of that and decimated the survivors. From then on, they spent the rest of the time in a state of semi-constant war between the various tribes and family groups. Clovis culture just happened to be at the crossing of at least two Black Swan events. (Younger Dryas followed within a couple thousand years by new invaders)

      • I am just reading up on Clovis – it seems there is now strong enough evidence to support the theory that they have not been the first inhabitants of the Americas, but that different palaeo-indian peoples have lived there a few thousand years before Clovis migrated from Siberia into North America.

        GL, thanks to your ruminations I learn a lot about things I have not known before! Ruminate on! 🙂

        • Technologically, Clovis most closely resembles Solutrean culture from France. This is why the “Amerindians” get so frantic when it comes up. Ya can’t have a European being the first resident of the Americas, that might upset the applecart that they have set up for themselves as being victims of European expansion.

        • This is one reason that they got so vociferous over Kennewick Man. They sued to have the remains declared as being that of an ancestor and to be re-interned on Holy burial ground. The fact that Kennewick Man had distinctly European characteristics had nothing to do with it. (yeah, riiiight).

          Another aspect that is routinely attacked is the genetic marker that is exhibited by by the Algonquin peoples. (Iroquois etc…) Specifically, Haplogroup X. The greatest concentrations are in the northeast US and in Turkey/Europe.

          As for Kennewick Man, I don’t think he was a Clovis remnant. In my opinion, he was probably a somewhat off the beaten path Nordic person. Sami people are well known for being able to exist in pretty shitty cold assed environments.

          Before anyone gets dismissive of me because of my obvious European roots, a couple of hundred years ago, my family had a feud with itself. Half of them had a European Grand Mother, the other Half had a Choctaw Grand Mother. I’m from the Choctaw side, though not enough to be considered to be of Amerindian decent. Though much more than some politicians who claim to be so. My German/Irish/Scottish roots have overcome the alcohol intolerance aspect and I can drink quite freely without trying to kill someone or trying to ride something dangerous. Though I have on occasion, infiltrated the wrong country’s base in an effort to get back to the ship. If it hadn’t been for security laughing their asses off at my plight, I probably would have been shot or arrested.

  1. Small earthquake just popped up on the Hekla Seismicity meter. (Just a heads up – not saying it’s anything serious). 🙂

  2. I’ma gentleman of leisure for at least 2 more weeks, maybe the most kick ass schleep schong of alll time…

  3. With a fascinating video:

    Swim between two tectonic plates
    BBC, 25 June 2014, In Iceland Diving, By Talia Avakian
    Iceland’s Silfra fissure – a crack between continents formed by the constant pulling apart of two tectonic plates – is a geological wonder. Because of this, it’s become one of the world’s top diving destinations, where divers and snorkelers can literally float between the North American and Eurasian continents; in some of the narrower openings, you can touch both sides at once. …

  4. In today’s GVP weekly report ( “Sinabung dome growth continued and was accompanied by a lava flow that was frequently visibly incandescent. The PVMBG observatory noted that the lava flow (particularly avalanches from the flow front) presented a threat to areas S and SE within a 5 km radius from the summit. ” Is the Ndokum Siroga village (~8.5 km of the summit) the one we see on the webcam?.

    • Yes, the webcam is located in the Sinabung volcano observation post in the village of Ndokum Siroga (or “pos pengamatan gunung api Sinabung di Desa Ndokum Siroga” in Indonesian).

        • The last report from June 18 shows that small new lava tongues are developing parallel to the main one. I think if lava breaks off from the steep slope higher up Sinabung pyroclastic flows could still happen. Otherwise, volcanic earthquakes are fading out and the seismic amplitude is also on the decline. SO2, CO2, H2S are still elevated, but also slowly diminishing it seems.
          Sinabung is still on alert level III.

  5. Thanks Bobbi.A good detailed read about a place I would love to visit but never will (unless I have a . Big lottery win.)
    I,m still afflicting the citizens of Brighton with my presence. I. Met a very pleasant young man called Joe yesterday. The poor lad served me in a shop that was selling great toys like ” build your own volcano” and “crack open your own geode.” He expressed his fascination for volcanos……..twenty minutes later ,looking a little dazed he assured me he would look in to Volcanocafe. SO JOE, if you do pop in to have a look, welcome. The bar is open every Friday along with some impossible riddles which will warp your brain even more than I did.

    I am on my kindle which seems take over my writing. I have missed you all but I now have a lovely little granddaughter called Lily. Born last Thursday and crying well. Parents look suitably haggard and sleep deprived. Granny B will be happy to get back to normal ruminations after being severely toddlerised.
    I am surprised everything is quiet , I expected at least a rumble from one of the Icelandic ladies. I shall be in the bar tomorrow night and I am instructing Carl to give drinks all round to celebrate the new VC member……I can’t understand why they wouldn’t call her Etna or Hekla…..sigh!

  6. Hi, Diana. Wishing you that big lottery win 😀 Congratulations to you and your family on the new addition.
    I too have a granddaughter named Lilly. Small world.

  7. I feel so happy to have finally seen something significant. Checking on Sakurajima a few minutes ago, I saw lightning in the black clouds spewing out of the volcano.
    Congratulations, Diana. My boyfriend has a granddaughter named Lily also. Such a pretty name. I only hope I can have a little granddaughter someday before my grandson wears me completely out. He’s now 8.
    This post is awesome, Bobbi. Loved the photos.

  8. I am so looking forward to sitting down reading todays new post out on the balcony and do some riddling while I indulge in a glass of Rioja Alta and Montecristo no 2 cigarr…
    It has been the yearly bookend reporting week, and I have had to go through and prepare them for every single company in the company group. Sigh…
    So, now everybody knows why on earth I have been so quiet lately.

    • To set this into perspective.
      Last time there was activity at Campi Flegrei there was 210 centimeters of uplift in a month and no eruption happened. During the last 48 hours before the last eruption there was 700 centimeters of uplift.
      So, somewhere between 2 and 7 meters is the critical point.

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