Scientists have found an ancient underwater volcano just off the island of Oahu in Hawaii. Geologists say that the volcano helped Oahu be raised from the seafloor resulting in the formation of the third largest island in Hawaii.
The new find was made by scientists from the University of Hawai'i at Mānoa (UHM). With the help of other scientists from the California based Monterey Bay Aquarium Research Institute and the French research center Laboratoire des Sciences du Climat et de L'Environnement, the team was able to uncover a third volcano that may have been responsible for the formation of Oahu.
"Both of these assumptions can now be revised: Wai'anae is not as large as previously thought and Ka'ena Volcano formed in the region between Kauai and Wai'anae," said UHM School of Coean and Earth Science and Technology Emeritus Professor of Geology John Sinton.
Sinton is also the lead author of a study on the subject published in the Geological Society of America Bulletin.
Prior to finding the newly discovered underwater volcano, geologists used to think that only two volcanoes were responsible for lifting Oahu up from the depths of the ocean. In modern times, Oahu is the third largest island in the state of Hawaii. In the entirety of the US, Oahu is the 20th largest island. While the islands of Hawaii and Maui are larger than Oahu, Oahu is the most populous island in the state. Today, close to a million people call Oahu their home, which is partly why the island is also known as "The Gathering Place."
"We previously knew that they formed by partial melting of the crust beneath Wai'anae, but we didn't understand why they have the isotopic composition that they do," said Sinton. "Now, we realize that the deep crust that melted under Waianae is actually part of the earlier Ka'ena Volcano."
The new conclusions are the result of years of hard work building on new as well as previously known information about the geology of Oahu. The fact that three volcanoes were responsible for the formation, Oahu was uncovered using high quality bathymetric data of the ocean floor off the island of Oahu. To get the necessary bathymetric data, the scientists relied in part on the Kilo Moana research vessel, which used its onboard high-resolution underwater mapping system to scan the seafloor.
"What is particularly interesting is that Ka'ena appears to have had an unusually prolonged history as a submarine volcano, only breaching the ocean surface very late in its history," Sinton said.
The newfound volcano has been named Ka'ena. Geologists believe that it became geologically active around 5 million years ago. Of the three volcanoes that formed Oahu, Ka'ena is the oldest. However, the Waianae was the first of the three to break through to the ocean's surface almost 4 million years ago. Around 3.5 million years ago, Ka'ena followed poking through the ocean waves. The last of the Oahu volcanoes to surface was the Koolau volcano, which followed suit 3 million years ago. Today, Ka'ena has receded back into the ocean depths.
