Mayor Island (Tūhua) is the top of a large rhyolite volcano in the western Bay of Plenty. The central ring of cliffs marks the edge of a caldera formed by an explosive eruption about 7,000 years ago. The black volcanic glass known as obsidian is found in some lava flows on the island.
Te whakamahi i tēnei tūemi
Photograph by Lloyd Homer
Permission of GNS Science must be obtained before any use of this image.