The largest volcano on Earth is no longer Mauna Loa , but another much larger and hotter volcano, also in Hawaii. A study from the University of Hawaii’s School of Earth and Ocean Science and Technology has shown that the Pūhāhonu, which means ‘tortoise that peeks out to breathe’ in Hawaiian, is the largest.
Scientists have long believed that Mauna Loa, on the Big Island, Hawaii, was the largest volcano in the world. The studies that established that Mauna Loa was the largest and hottest date back to 1974, at which time the root of the seabed volcano was not taken into consideration. In 2020, new comprehensive modeling and surveying, using methods similar to those used for Mauna Loa, now shows that the Pūhāhonu (structure known as the Gardner Pinnacles) is the largest; specifically, it has almost twice the size of the Mauna Loa.
Inspecting the ocean floor along the chain of mostly underwater Hawaiian leeward volcanoes and chemically analyzing the rocks allowed the scientists to reach the new conclusion.
It was previously believed that hot spots that produce volcano chains like the one in Hawaii progressively cool over a million or two million years and then ‘die’. But scientists have found that hot spots can occasionally experience melt pulses. One of these points created the now extinct Midway group of volcanoes and another, much larger, created the Pūhāhonu. “This discovery will rewrite the textbooks on how mantle feathers work,” the researchers write at a news conference.
Furthermore, Pūhāhonu has the highest forsterite (Fo) content ever reported for Hawaiian lava (91.8%). The high level of forsterite reflects the highest rock melting temperature for any Cenozoic basalt: “A lone wave within the Hawaiian plume is the most likely cause of Pūhāhonu’s high temperature and the resulting increased volume flow given the absence from a more fertile source for the Pūhāhonu basalts, as was found for many Hawaiian island basalts.
This work also draws attention to a rarely visited part of the state of Hawaii that is ecologically, historically, and culturally important.
References:
‘Pūhāhonu: Earth’s biggest and hottest shield volcano’. Michael O. Garcia, Jonathan P. Tree, Paul Wessel, John R. Smith. https://doi.org/10.1016/j.epsl.2020.116296
