It is known for a long time that Mauna Loa on Hawaii’s Big Island is the largest volcano on the earth. It is an active shield volcano, consists of relatively gentle slopes. Its volume as estimated to be almost 18,000 cubic miles (or 75,000 cubic kilometers). From the base on seafloor to its summit, it is about 13,000 metres– making it technically taller than the Mount Everest, but basically the summit of Mauna Loa is 4,169 metres from mean sea level.


However, researchers recently claim that the Gardner Pinnacles or Pūhāhonu is the largest standalone volcano on the earth. It is tens of thousands of cubic miles large volcano situated beneath the ocean floor. In Hawaiian, ‘Pūhāhonu’ means ‘turtle rising for breath’.

The research was conducted by Michael O. Garcia, Jonathan P. Tree, Paul Wessel from the Department of Earth Sciences, and John R. Smith from the Department of Oceanography, University of Hawaii. The paper, entitled as ‘Pūhāhonu : Earth's biggest and hottest shield volcano’, was published in the journal Earth and Planetary Science Letters.

Discovery of Gardner Pinnacles

The American whaler Maro, a ship specialized for catching or processing whales, which was commanded by Captain Joshep Allen, discovered the Gradner Pinnacles, on 2nd June in the year 1820.

Where is it located?

The map of Northwest Hawaiian Ridge and Islands. Magenta box in it, shows the location of Pūhāhonu
Image Courtesy : Earth and Planetary Science Letters

Pūhāhonu is located 511 nautical miles (or 588 miles; 946 kilometres) north-west of Honolulu, and 94 nautical miles (or 108 miles; 174 kilometres) from French Frigate Shoals. The coordinate of the two barren peak’s outcrop is 24°59’56”N and 167°59’58”W.

What’s about Pūhāhonu?

The Gardner Pinnacles or Pūhāhonu is an outcrop of two barren peaks of a colossal volcanic mountain, beneath Pacific Ocean. It extends from Hawaiian islands upto the eastern edge of Russia. Its highest peak is 52 metres (or 170 feet) above mean sea level.


Findings of the study

Researchers have used Sonar detector (full form: Sound navigation ranging, is a technology that uses propagation of sound to detect the distant objects under water) and gravity detectors to explore the entire topographic insignia of Pūhāhonu.

Bathymetric map of Pūhāhonu and West Pūhāhonu volcanoes in detail
Image Courtesy : Earth and Planetary Science Letters

The study reveals that the giant volcano contains nearly 36,000 cubic miles (or 1,50,000 cubic kilometres) of igneous rocks (based on a Sonar survey in 2014), which is almost more than twice than that of the volume of Mauna Loa.

Researcher mentioned in the paper,
The new volume calculation shows that Pūhāhonu is extremely large than any other Hawaiian volcano including Mauna Loa, which was assumed to be the largest volcano on Earth.

Not only biggest, but researchers also found it to be the hottest volcano on the earth. They examined olivine phenocryst composition from magma of different parts of the volcano. They presumed that Gardner Pinnacle’s magma might be about 1700°C (or 3100°F) during early flow.

Thus from an overall view, Mauna Loa volcano on Hawaii island might lose its distinction as the largest shield volcano of the earth, unless the mean sea level is considered.

Learn More

Wikipedia | Gardner Pinnacles

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