Diamondhead is a huge volcanic tuft cone on O'ahu. It was created half a million years ago when O'ahu was still over the hot spot in the pacific plate that feed our islands. O'ahu is thought to be made from two large shield volcanoes, Wai'anae and Ko'olau. Ko'olau is the volcano that fed this tuft cone. The Hawaiian name for Diamondhead is Le'ahi, which means the brow of the Ahi tuna.