Mauna Loa — the world’s largest active volcano — is erupting in Hawaii for the first time since 1984.
Lava is flowing down the side of the volcano at a temperature of 1,000°C, but experts say this is not yet a major threat to local residents.
How big is Mauna Loa?
Mauna Loa, which means “long mountain” in Hawaiian, is the largest active volcano in the world.
It covers 5,271 square kilometers and is part of a chain of five volcanoes that form the Big Island, the largest in the Hawaiian archipelago.
This volcano alone covers half of the entire island.
The summit of Mauna Loa is 4,170 meters above sea level, but its base is at the bottom of the ocean. From there to the summit, it is 9,170 meters, which makes it higher than Mount Everest.
Why is Mauna Loa erupting?
Plumes of superheated material called magma have been bubbling up under Mauna Loa and neighboring volcanoes from a “hot spot” deep in the Earth.
“No one knows exactly why these hot spots exist,” says Carmen Solana, a volcanologist at the University of Portsmouth in the UK.
“But they could be caused by the decay of radioactive material in the Earth’s mantle.”
“These magma plumes formed all of the Hawaiian islands.”
When Mauna Loa erupts, Solana explains, the magma spurts first into the caldera—the bowl-shaped depression at the summit of the volcano. Called Mokuaweoweo, it covers an area of 15 square kilometers and is 180 meters deep.
The magma then oozes out of “crevices,” or fissures in the rock, on the side of the volcano and down the mountainside as a liquid called lava. It has a temperature of 1,000°C and burns everything in its path.
When volcanoes erupt, they also release matter that cools down to form strands of glass called Fur Hair.
“Pele was the name of the goddess believed to live on Mauna Loa, and the fragments are thin and golden brown in color,” says Solana. “She was a moody blonde.”
Why is the eruption of Mauna Loa important?
Mauna Loa has erupted 33 times since 1843, the first recorded year. On average, there is an eruption every five and a half years.
However, the last eruption was almost 40 years ago.
“There have been some signs of magma budding over the last 10 years,” says Andrew Hooper, professor of geophysics at the University of Leeds in the UK. “But there had been no eruptions until now.”
Mauna Loa’s current eruption is offering a new generation of scientists the opportunity to study how the volcano works, says Hooper.
“It will be interesting for us to see where the magma is stored within Mauna Loa — where it is between bubbling up from the Earth’s mantle and coming out of the volcano’s surface,” he adds.
Is the Mauna Loa eruption dangerous?
Unlike many volcanoes, Mauna Loa does not usually produce truly explosive eruptions, in which lava is spewed into the air along with clouds of ash and gas.
Instead, lava flows at a rather slow pace down the side of the volcano.
“Lava flows are not life threatening,” says Hooper, “because you can get out of their way.”
“Also, the lava isn’t flowing west of the volcano towards the nearest towns — it’s going northeast. It would have to travel a long way in that direction before it does serious damage to property.”
But the gases that Mauna Loa is releasing could pose a greater risk to the local population.
“Volcanic gases, including sulfur dioxide and chlorine, react with the humidity in the air, producing ‘vog’, which is volcanic fog”, explains Solana.
“It can cause problems for people because of the wind. It can irritate the eyes and cause breathing problems for some people.”
Hawaii health officials say air quality is still good, but could deteriorate at any time.
If this happens, residents are advised to avoid outdoor activities and stay indoors with doors and windows closed.