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.
These eruptive events 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 500,000 to 400,000 years old.
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. These eruptive events 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 500,000 to 400,000 years old.
Diamond Head, Hawaii