Why the volcano is still a mystery to researchers

Mauna Loa in Hawaii is one of the largest active volcanoes on earth. It has been spitting fire for days now, masses of lava are pouring over the main island of the archipelago. There is currently little risk to humans. But the event is significant for science: To this day, the volcanic activity on the Hawaiian Islands poses many puzzles for researchers. And it is only during an outbreak that important data can be collected that can help to understand it better.

The volcanoes in Hawaii are different from those in many other places. Volcanoes are usually located where the plates of the earth’s crust meet. When the plates rub together or move apart, fissures can form in the earth, allowing lava to flow upwards. But Mauna Loa and Hawaii’s other volcanoes are thousands of miles from such zones. So how is it that the fire finds its way to the surface here as well?

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According to Hawaiian mythology, Pele, the goddess of fire, causes volcanoes to erupt. After a fight with her sister, the goddess of the sea, Pele is said to have fled into a crevasse. In revenge, she lets the mountains spit their hot embers, according to legend. A scientific explanation was not found until the 1960s. Back then, Canadian geophysicist and geologist John Tuzo Wilson theorized that Hawaii is located over a seething hotspot. Magma, hot and liquid rock from the depths, reaches higher layers of the earth through a narrow tunnel. There the canal widens like a mushroom and forms a reservoir. The technical term for such a magma channel is mantle plume.

Hawaii formed by volcanic eruptions

During an eruption, the layers of earth above the magma column melt and the glowing mass escapes – from that moment on it is called lava. While the magma source has always been in the same place beneath the Hawaiian archipelago, the top layers of the earth have slowly moved across it over the millennia. As a result, new volcanoes formed elsewhere on the surface during subsequent eruptions. This is how the island chain of Hawaii is said to have originated.

The results of seismic measurements also fit the theory of a lava hotspot under Hawaii. They can be used to record tiny tremors in the Earth’s interior, from which information on the flow of magma can be derived. Together with the satellite technology, which measures minute changes in the height of the earth’s surface, the method helps to predict volcanic eruptions. Weeks before the current eruption, a warning level was declared in Hawaii because tremors from magma flows had been measured.

Last Sunday, the measuring stations on the summit of the volcano indicated particularly strong underground activity: “When we tried to determine where the tremors were coming from, we noticed that they were getting closer and closer to the surface of the earth, and that is unmistakable Signs that the magma is moving upwards,” Gabi Laske, a geophysicist at the University of California, told the New York Times (“NYT”). After the outbreak actually began on Sunday, no one really knows how long it will last, says Laske.

Mauna Loa eruptions less explosive

There are also limits to the accuracy of predictions. So before the eruption it was not foreseeable where exactly the lava would pour. There are settlements on the southwest side of Mauna Loa that would have been threatened. Only when the lava began to flow was it seen that this time it was moving in a northeasterly direction, towards a part of the island that is uninhabited.

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Mauna Loa erupts less violently than many other volcanoes. Because its lava consists mainly of molten basalt rock, which makes it more liquid and binds less explosive gases. Even if red embers are bubbling up at the exit point – clearly visible on video recordings – the majority of the lava mass simply flows down the mountain and is not thrown up.

However, the movements of low-viscosity magma in the Earth’s interior are also more difficult to determine using seismic measurements. To this day, researchers don’t have an accurate picture of the currents under Hawaiian volcanoes, and Mauna Loa still puzzles them. Further data are still missing to substantiate the theory of the mantle plume, about which there are always doubts. In addition, satellite technology can only identify a reservoir of magma relatively close to the earth’s surface. However, it is not yet clear whether there is another reservoir in deeper layers, Helge Gonnermann, a volcanologist at Rice University, told the New York Times.

Eruption offers opportunity for measurements

Now that Mauna Loa is erupting, the situation is changing: there is so much movement underground that it is easy to measure. The devices can then measure vibrations in deeper layers of rock and researchers can analyze what minerals the lava is made of. All of this makes it possible to get a better picture of what is going on at depth.

Mauna Loa last erupted some 38 years ago, so its renewed activity is a rare chance for volcanologists to learn more about this special volcano. It may then be possible to predict the time, place or extent of future outbreaks more accurately in the future. In any case, further outbreaks are to be expected. This was confirmed by John Orcutt, who as a geophysicist himself was involved in measurements on Mauna Loa, to the “NYT”: “It’s something that’s been happening for thousands to millions of years and that won’t just stop,” says Orcutt. “The magma cannot be held back forever.”

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