Beneath the cyan and cerulean waters of the Northwestern Hawaiian Islands lurks a leviathan. Its true extent has been hidden for a few years, however no extra. What geologists have discovered is a marvel – the most important, hottest recognized volcano on the planet.

Startlingly, it is greater than twice the dimensions of the earlier file holder, Mauna Loa on the Island of Hawai’i. And it might change our understanding of the huge Hawaiian-Emperor seamount chain of volcanoes that span the North Pacific Ocean.

The brand new record-breaker spreads throughout round 148,000 cubic kilometres (35,507 cubic miles) beneath the waves of the Papahānaumokuākea Marine National Monument, in comparison with Mauna Loa’s 74,000.

Solely comparatively small rocky pinnacles referred to as the Gardner Pinnacles break the floor, giving the volcano its title – Pūhāhonu, the Hawai’ian phrase for ‘turtle rising for breath’.

“We’re sharing with the science group and the general public that we ought to be calling this volcano by the title the Hawaiians have given to it, slightly than the western title for the 2 rocky small islands which might be the one above sea stage remnants of this as soon as majestic volcano,” said geologist Michael Garcia of the University of Hawai’i at Manoa.

Again within the 1970s, low-resolution bathymetric information recommended Pūhāhonu was round 54,000 cubic kilometres in dimension, then regarded as the biggest volcano earlier than a extra intensive survey of Mauna Loa revealed its true dimension.

Pūhāhonu solely regains its crown after intensive surveys of the area added high-resolution bathymetric and multibeam sonar information to our present understanding of the northwest Hawaiian Ridge, from which the volcano rises.

Geologists mixed this with petrologic analyses of rock samples retrieved from the volcano, refining quantity calculations and modelling based mostly on these parameters.

“It has been proposed that hotspots that produce volcano chains like Hawai’i bear progressive cooling over 1-2 million years after which die,” Garcia said.

“Nonetheless, we’ve realized from this examine that hotspots can bear pulses of soften manufacturing. A small pulse created the Halfway cluster of now extinct volcanoes and one other, a lot greater one created Pūhāhonu. This can rewrite the textbooks on how mantle plumes work.”

(Garcia et al., EPSL, 2020)

Pūhāhonu is a shield volcano, between 12.5 and 14.1 million years previous, shaped by a single magma plume surging by the mantle. Over the millennia, this supply progressively constructed the volcano to a peak of 4,500 metres (14,764 toes) from its lowest level, spanning an space 275 kilometres (171 miles) lengthy and 90 kilometres (56 miles) large.

Chemical evaluation of rock collected from the volcano revealed a better focus of an olivine mineral referred to as forsterite than we have ever seen in a Hawaiian volcano. This mineral signifies magma on the upper finish of the temperature vary.

The calcium oxide content material within the forsterite allowed the group to deduce the depth at which it shaped, confirming that it did type in magma. Simulations allowed the group to calculate the stress at which the forsterite shaped, and the temperature.

In accordance with these calculations, the magma clocked in at 1,703 levels Celsius (3,097 levels Fahrenheit) – hotter than another Hawaiian basalt. This excessive temperature is mirrored within the volcano’s dimension, the researchers stated.

It is a powerful beast in its personal proper. However it additionally has necessary implications for our understanding of the processes that create these unbelievable formations.

“The Hawaiian-Emperor Chain is arguably the world’s finest studied floor expression of a mantle plume,” the researchers wrote in their paper.

“Nonetheless, new insights into its magmatic and thermal historical past proceed to be revealed as extra of the Hawaiian-Emperor Chain is mapped and sampled. These insights are offering a extra full understanding of the mechanics and thermal evolution of mantle plumes.”

The analysis has been revealed in Earth and Planetary Science Letters.