 After hundreds of thousands of years of dormancy, Koolau volcano began to erupt again.Some thirty eruptions over the past 500,000 years or so have created many of the landmarks around eastern Oahu, such as Diamond Head, Koko Head (Hanauma Bay), Koko Crater, Punchbowl Crater, Tantalus, and Āliapaakai, and are collectively known as the Honolulu Volcanic Series, or simply Honolulu Volcanics.According to the US Geological Survey, the most recent eruptions in this series of activity occurred between about 70,000 to 100,000 years ago.