(CNN) – The now-extinct Pūhāhonu volcano on the Northwest Hawaiian Islands doesn’t appear to be one: It has two arid peaks that rise only about 51.8 meters above sea level. And this is especially true when in the same archipelago, the Mauna Kea and Mauna Loa volcanoes rise above each other more than 3,962 meters above sea level.
But, scientists at the University of Hawaii at Mānoa have shown that the appearance of the Pūhāhonu can be misleading.
A new study published in the journal Earth and Planetary Science Letters notes that the Pūhāhonu is the largest shield volcano in the world, taking the title from Mauna Loa.
Scientists surveyed the ocean floor and used quantitative models to determine that the volcano, which is approximately 442 kilometers long and 90 kilometers wide, is twice the size of Mauna Loa.
“The Pūhāhonu is huge,” the study noted. And so much so that it is causing the earth’s crust to sink.
“Rapid loading of bark causes it to sink,” Michael Garcia, lead author of the study, told CNN. “When a giant volcano forms, the hot mantle moves away from the weight allowing the volcano to sink.”
Located about 1,000 kilometers northwest of Honolulu, the name Pūhāhonu translates to “tortoise surface exit” in Hawaiian. The small peaks above sea level are also known as “Gardner Pinnacles”.
The American whaler Maro first observed the Pūhāhonu in 1820, and in 1828 the crew of a Russian ship landed on it for the first time. The volcano is now part of the Papahānaumokuākea National Marine Monument, established in 2006.
The island is home to a single plant species, to succulents, but is an ideal habitat for a wide range of fish, corals and insects.
Initially, a 1974 study considered Pūhāhonu to be the largest volcano in the Hawaii-Emperor Seamount Chain, based on limited data. Later studies, which examined both what is above and below the sea surface, concluded that Mauna Loa was the largest volcano. The recent study updates that conclusion.
Pūhāhonu is not only the largest volcano in the world, it is also the hottest. These two conditions are interconnected, explained García.
“Volume and temperature go hand in hand. A large volume comes from the hot magma. It is more likely to erupt if it is hot, “Garcia told CNN.
An analysis of volcano rock samples was used to determine the temperature of the magma, and it was found to be approximately 1,700 degrees Celsius.
“Finding the largest shield volcano on Earth in the 21st century is a surprising discovery, but then we know more about the surface of Mars than what is under the ocean on Earth,” Garcia told CNN.
“We are still discovering things about our physical planet that we did not know. There is still a lot to learn about planet Earth, “he insisted.