About 600 miles northwest of Honolulu, in the middle of the Pacific Ocean, two small peaks protrude from the sea. Apparently there is something enormous beneath this emerging peak, the largest single volcano in the world!
Recent seabed mapping from the Papahānaumokuākea Marine National Monument, reveals the full size of the Pūhāhonu, a 5-hectare rocky rock surrounding two peaks poking out of the sea.
Michael Garcia, a volcanologist at the University of Hawai'i at Mānoa, and his colleagues, found that the largely submerged volcano contains at least 35 cubic miles of rock, according to a study published in 2020 in Earth & Planetary Science Letters. .
That's roughly double the volume of Hawaii's Mauna Loa, the previous record holder for the largest shield volcano on Earth. At its widest point, Pūhāhonu, which means turtle to surface in Hawaiian, stretches for more than 170 miles.
Quoted from Discover Magazine, this long-defunct volcano is located along the Hawaiian-Emperor Chain, a chain of more than 120 volcanoes that stretches for more than 3,700 miles across the Pacific Ocean.
Large, expansive volcanoes such as Pūhāhonu and Mauna Loa produce hot basalt lava flows. Typically, the volcano erupts at temperatures around 2,100 degrees Fahrenheit. But by examining the minerals erupting from Pūhāhonu, Garcia found that the lava was close to 3,000˚F. The temperature will record the hottest volcanic lava that erupted on Earth in the last 65 million years.
The waves in the "fur coat" that feed the volcano likely contributed to Pūhāhonu's massive size and temperature extremes. Nearly 2,000 miles below our feet, hot material rises from the boundary between Earth's mantle and core, melting as it approaches the surface.
The study's authors point out that a wave of hotter material in the plume that reached the surface about 12 million years ago, melted more of the mantle, producing more hotter lava.
These tremors from the Hawaiian Plume, recorded through measurements of Pūhāhonu's size and composition, may provide important clues to what happens at the boundary with Earth's core as our planet cools internally.
