According to a 2020 report in Earth and Planetary Science Letters, Pūhāhonu contains approximately 150,000 cubic kilometers of rock, based on a 2014 sonar survey. This would make it Earth's largest single volcano. Only about one-third of that volume is exposed above the sea floor. The rest is buried beneath a ring of debris, broken coral, and other material that has eroded from the peak. By comparison, from sea floor to peak, Mauna Loa, on Hawaii's Big Island, is the tallest shield volcano on Earth. But it is nowhere near as massive as Pūhāhonu; a 2013 study estimates Mauna Loa's volume at 83,000 cubic kilometers. Pūhāhonu is so heavy, researchers note, that it has caused Earth's crust nearby—and thus the volcano itself—to sink hundreds of meters over millions of years.