This geology field guide provides an easy to understand overview of the most relevant and up to date information on how the island of O'ahu formed. It is a rich and engaging tour through the geological story of O'ahu while exploring many off the beaten path important regions. It connects hikers and geology lovers alike with the natural and cultural history of the island by describing the volcanic landforms. It includes a short intro on how Hawaiian hotspot volcanoes form and emerge from the sea floor and provides the most current understanding of how O'ahu formed during the past 5 million years. The guidebook is a travel companion for residents and visitors alike. It can easily be carried while you visit and see first-hand some of the mysteries geologists have uncovered during more than 90 years of studying this magical island. You will see world-class exposures of many different volcanic landforms present at our most informative stops. Following the introduction and description of the volcanic rock types present, the author provides a brief overview of the typical life and demise of a Hawaiian hotspot volcano and how O'ahu’s three main shield volcanoes formed.