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Largest and hottest shield volcano on Earth discovered

Its size is not related to the thin lithosphere, slow plate motion, or a fertile source.

A team of volcanologists and ocean explorers from the University of Hawaiʻi at Mānoa School of Ocean and Earth Science and Technology (SOEST) have discovered the largest and hottest shield volcano on Earth. They utilized a few lines of evidence to determine Pūhāhonu, a volcano within the Papahānaumokuākea Marine National Monument, holds this distinction.

Until now, Mauna Loa, a culturally-significant and active shield volcano were thought to be the largest volcano in the world. It is one of five volcanoes that form the Island of Hawaii in the U.S. state of Hawaiʻi in the Pacific Ocean. 

Before coming to this conclusion, scientists studied the ocean floor along the mostly submarine Hawaiian leeward volcano chain. They chemically examined the rocks in the UH Mānoa rock collection and modeled the results of these studies. They found that Pūhāhonu is nearly twice as big as Mauna Loa.

Pūhāhonu means “turtle rising for breath” in Hawaiian.

Michael Garcia, a lead author of the study and retired professor of earth sciences at SOEST, said“It has been proposed that hotspots that produce volcano chains like Hawaiʻi undergo progressive cooling over 1-2 million years and then die. However, we have learned from this study that hotspots can undergo pulses of melt production. A small pulse created the Midway cluster of now extinct volcanoes and another, much bigger one created Pūhāhonu. This will rewrite the textbooks on how mantle plumes work.”

In 1974, Pūhāhonu was suspected as the largest Hawaiian volcano based on minimal data. Ensuing investigations of the Hawaiian Islands reasoned that Mauna Loa was the largest volcano. However, they included the root of the volcano that is beneath the seafloor that was not considered in the 1974 study. The new comprehensive surveying and modeling, using methods similar to those used for Mauna Loa, show that Pūhāhonu is the largest.

Journal Reference:
  1. Michael O.Garcia et al, Pūhāhonu: Earth’s biggest and hottest shield volcano. DOI: 10.1016/j.epsl.2020.116296

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