Diamond Head Volcanic Crater


    • Type: Volcanic Crater
    • Diameter: ~1.17 Km
    • Depth: 171 m
    • Age: ~300,000 years
    • Location: Oahu, Hawaii, USA – N 21° 15.7’ W 157° 48.3’
The name of Diamond Head became famous in the 1820’s when crews from British ships discovered calcite crystals on the crater. Because they believed they were diamonds, they named the famous volcano what it’s currently known as. Later, the British found that the crystals were, in fact, not diamonds.
Geology. Diamond Head (a Fort Rae analog) 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 huge crater was formed about 300,000 years ago during a single, explosive eruption that sent ash and other fine particles in the air. As these materials settled, they cemented together into a rock called tuff, creating the huge crater (geologyin.com).

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 (Volcano Cafe).

Yours truly at Diamond Head, Oahu. This dormant volcano is part of a system of cones, vents, and flows. These events are collectively known to geologists as the Honolulu Volcanic Series that created many of Oʻahu’s well-known landmarks, including Punchbowl Crater, Hanauma Bay, Koko Head, and Mānana Island in addition to Diamond Head.


The Fort Rae structure (a Diamond Head analog) – south west (looking north east) from GOZooM.