The island of O‘ahu has two majestic mountain ranges, Ko‘olau and Wai‘anae. And for nearly as long as island geology has been taught in schools, the conventional wisdom was that O‘ahu was formed by two volcanoes. But last year, scientists announced that they'd discovered a third, long-lost volcano off the westernmost tip of the island.

Named Ka‘ena, like the nearest rocky point of O‘ahu, this third volcano is thought to be a missing link in the long Hawaiian Island chain. And the scientist that led the groundbreaking research that discovered it will share his research and insights at Chaminade University on Thursday.

John Sinton is Professor Emeritus of Vulconology, Geochemistry and Petrology at the University of Hawaii's School of Ocean and Earth Science and Technology (SOEST). He and several colleagues published a paper last summer that used new undersea observations, geochemical samples and geophysical surveys to identify "a volcanic structure that is independent of Wai‘anae Volcano."

"We thought we knew where all the Hawaiian volcanoes were, and here's one we didn't really know about," Sinton told Reuters at the time. "It explains a lot of things about Oahu."

One of those things is evident to anyone who looks at a map of the main Hawaiian islands: the large gap between Oahu and Kauai. Kaua‘i and O‘ahu. The two islands are more than 70 miles apart (the Kaʻieʻie Waho Channel), more than twice the distance between Maui and Hawaii Island (the ʻAlenuihāhā Channel, at 30 miles wide).

Ka‘ena Volcano was the older brother to Waianae and Ko‘olau, but never rose more than 3,200 or so feet above sea level. But now that it's been found, scientists have a rare opportunity to study a Hawaiian volcano that formed in isolation on the deep ocean floor.

Sinton specializes in using volcanic rocks as a tool for investigating magmatic processes, and his research revolves around "the rock cycle," or the formation, motion and recycling of the Earth's crust. He is a major contributor to digital mapping projects and is also co-editor of the seminal 1979 book, "Field Trip Guide to the Hawaiian Islands."

The free pau hana talk is presented by ARCS Honolulu, the local chapter of the Achievement Rewards for College Scientists Foundation. The national non-profit organization was founded and is run entirely by women, and is dedicated to advancing science in America through student sponsorships. In Honolulu, the organization annually supports UH doctoral students in STEM and health disciplines with unrestricted grants.

"Ka‘ena: Discover O‘ahu’s 3rd Volcano" will be held in Henry Hall on the Chaminade University campus on Thursday, Nov. 5 beginning with drinks and pupus on the lanai at 5:30 p.m. followed by Sinton's talk at 6 p.m. For more information and to RSVP, please email ARCS Honolulu historian Sui-Lan Ellsworth at meisuilan@yahoo.com. For more information on the organization, visit the ARCS Honolulu website.

Hat tip: Cheryl Ernst/CTAHR via Gareth Wynn-Williams of Honolulu Science Cafe.