An extinct Hawaiian volcano called P奴h膩honu is the largest in the world, with a volume twice that of the next leading contender. What鈥檚 more, the lava that once erupted from P奴h膩honu is the hottest recorded in the past 66 million years.
鈥淧奴h膩honu is the most massive volcano on Earth,鈥� says Michael Garcia at the University of Hawai鈥檌 at M膩noa in Honolulu.
At the surface, P奴h膩honu doesn鈥檛 look like much: just a pair of barren, rocky outcrops hundreds of kilometres north-west of the main Hawaiian islands. Its Hawaiian name means 鈥渢urtle surfacing for breath鈥�.
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Garcia and his colleagues surveyed P奴h膩honu in 2014 using sonar and gravity sensors, which can measure mass. They found it has a volume of 148,000 cubic kilometres. That dwarfs Mauna Loa, another Hawaiian volcano generally though to be the largest, which is only 74,000 km3 鈥� although it is still taller than P奴h膩honu.
The gravity data also revealed that there is one central mass, confirming that P奴h膩honu is one volcano rather than the result of lavas from several volcanoes together.
The other serious contender for the title of world鈥檚 largest volcano was Tamu Massif, a submarine mountain off the coast of Japan that is the size of the British Isles. In 2013, a team of researchers claimed that it was a single, 4-kilometre tall volcano, but in 2019, . Tamu Massif is actually the product of magma rising up from seafloor and spreading, so it isn鈥檛 a single volcano at all.
There are also supervolcanoes like Yellowstone in the US and Campi Flegrei in Italy, but Garcia says these aren鈥檛 directly comparable. 鈥淭he eruptions [of supervolcanoes] are bigger in the total volume of material erupted鈥�, he says, and the Yellowstone crater is 鈥渆normous鈥�, but researchers aren鈥檛 sure of their total volume. 鈥淭hey鈥檙e known for their very large eruptions, but not necessarily for their total bulk. It鈥檚 kind of comparing apples and oranges.鈥�
Based on the chemical makeup of the rocks, P奴h膩honu also erupted unusually hot magma 鈥� hotter than any other known volcano from the past 66 million years. Like the rest of the Hawaiian volcanoes, it is powered by a plume of unusually hot molten rock in Earth鈥檚 mantle. Fortunately, P奴h膩honu has been extinct for at least 12 million years.
Earth and Planetary Science Letters
