Volcanologists could hardly contain their excitement after Mauna Loa in Hawaii, the world’s largest active volcano, reawakened this week after lying dormant for nearly four decades, sending lava fountains high into the air and down the mountain.
“It’s fabulous, really fantastic,” said Carmen Solana, an expert on lava flows at the University of Portsmouth in the UK. “We’ve been waiting for a long time for this. All my career I’ve been hearing ‘Mauna Loa is going to erupt — Oh no it isn’t’. Now it really is.”
Diana Roman, a volcanologist at the Carnegie Institution for Science in Washington DC, said: “The eruption [is] really important for our understanding of this type of volcanism.”
Mauna Loa, which looms 4,170 metres over Hawaii’s Big Island, is one of the world’s most studied volcanoes, with more instruments on its slopes than any other. The eruption — the first for 38 years — offers scientists a unique opportunity to examine the factors that trigger the flow of magma — molten rock with a temperature of around 1,000C — through the volcano’s underground channels and on to the surface as lava. They also hope to improve their ability to forecast the timing and strength of eruptions.
So far, the excitement occasioned by the spectacle and scientific opportunity has not been tempered by any significant damage or danger. Hawaiian volcanoes are generally what volcanologists call “effusive”, producing extensive lava flows but not the violent explosions that characterise the most dangerous and unpredictable eruptions elsewhere.
The most significant casualty since the eruption started on November 27 is data collection for one of climate science’s most famous records, the Keeling Curve. This 60-year record of rising carbon dioxide levels in the atmosphere is generated by instruments at Mauna Loa Observatory, but lava flows have cut power and access to the site.
Ralph Keeling, a geoscientist at Scripps Institution in San Diego, whose late father Charles created the curve, said the outlook for future carbon dioxide readings was “very troubling . . . It’s a big eruption and it’s in a bad place.”
However, the island’s 200,000 residents and visiting tourists have so far been largely unscathed. Mauna Loa’s lava front is moving slowly, at 24 metres per hour, across uninhabited ground with little vegetation.
The quantities of sulphurous gases, ash and the evocatively named but potentially hazardous Pele’s hair — long, glassy strands carried downwind when bubbles burst from molten lava — have been relatively limited and diluted by the wind.
Scientists say Mauna Loa is also not likely to shoot vast quantities of disruptive material high into the atmosphere, in contrast to the 2010 eruption of Eyjafjallajökull in Iceland. That sent an ash plume 9km into the atmosphere and eventually across Europe, throwing aviation into chaos for almost a month.
According to volcanologists, there is also no chance of an event on the scale of the two great Indonesian eruptions of the 19th century — Tambora in 1815 and Krakatoa in 1883 — which killed tens of thousands of people and affected the global climate for years.
“Each volcano has its own personality,” said Roman. “On Hawaii we have two volcanoes side by side, Mauna Loa and Kilauea, that behave quite differently though they are connected to the same driving system at depth.”
Kilauea is one of the world’s most active volcanoes, erupting much more frequently and for longer than Mauna Loa.
However, a prolonged Mauna Loa eruption would cause significant damage, as Kilauea did when a 2018 eruption destroyed 700 homes. The lava flow could cut Saddle Road, the main highway between Big Island’s east and west coasts, within days if activity continues at its current rate.
Volcanologists are reluctant to predict how long the eruption will last. “If you look at the character of the volcano and its past eruptions, they mostly lasted for a few weeks, and that is the best general expectation this time,” said Roman. “We don’t have a good tool to predict the duration.”
At present lava is emerging from a fissure on the north-east side of the mountain near the summit. If it continues to flow at current rates without solidifying, it would reach Hilo, the island’s capital with a population of 45,000, within weeks.
“A worst-case scenario is that fissures open further down the slope, which could result in lava reaching Hilo more quickly,” said Solano.
Roman said, “Another worst-case scenario would be a large earthquake, perhaps magnitude seven, associated with the eruption.”
If all goes well, however, this eruption of Hawaii’s volcanic giant will provide more pleasure than pain — a spectacular demonstration of the power of Earth’s geophysical forces without human casualties or significant property destruction.