How Mauna Loa Went From a Hot Blob to the Biggest Volcano in the World

The largest volcano in the world, Hawaii's Mauna Loa, has been erupting for 48 hours. The USGS announced the eruption at 11:30 p.m. HST on November 27 and lava is now flowing towards the northeast side of the island.

The United States has more volcanoes than any other country in the world, although only 42 of them have been active in the last 70 years. Of these active volcanoes, six are located in Hawaii.

The Hawaiian islands sit at the southeast end of a linear chain of more than 129 volcanoes, situated above and below sea level, that stretches about 3,800 miles across the north Pacific. But, unlike most active volcanoes, Hawaii is not located at the boundary between Earth's tectonic plates. Rather, it sits right in the middle of one.

"In the 1960s scientists developed the idea that Hawaii's volcanoes lie above a very large, hot blob, or plume, of rock that is rising very slowly deep inside the Earth's mantle," University of Oxford volcanologist David Pyle, told Newsweek.

"About 100 kilometers below the Earth's surface, some of the rock in this rising plume becomes hot enough to melt, and it is this melt that eventually rises up through the tectonic plate, to erupt and build the volcanoes," he said.

"These geological processes operate very slowly, over many thousands to millions of years."

As the Pacific plate moves over this plume, new volcanoes continue to form. "Each of the Hawaiian volcanoes is at a different stage of its 'life history,' reflecting their location above the plume," Pyle said.

The Big Island is the newest of the eight major Hawaiian islands. It is also the largest, boasting four active volcanoes, including the youngest and most active volcano on the archipelago: Kilauea.

Kilauea lies just 21 miles from the summit crater of Mauna Loa and has been erupting continuously since September 2021. However, the eruption is contained in the volcano's crater, unlike the eruption at Mauna Loa, which has extended outside the volcano's summit crater.

Mauna Loa towers over the Big Island of Hawaii at an elevation of 13,000 feet above sea level and accounts for over half of the land area on the island. The volcano also extends far below the sea's surface to a depth of about 19,700 feet, making its total height nearer to 33,500 feet.

So far, the USGS has said that Mauna Loa's eruption does not pose a threat to local communities or infrastructure. However, warnings have been issued about high levels of volcanic gas, volcanic smog, and the risk of airborne strands of volcanic glass, known as Pele's hair, which can damage lungs and cause skin and eye irritation.

The situation is being carefully monitored by the Hawaii Volcano Observatory and emergency management partners in case the risk level changes.

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