According to scientists at the US Geological Survey’s Hawaiian Volcano Observatory in Hilo, the eruption began just before midnight on Sunday. Webcams mounted on the summit caldera of Mokuaweoweo showed a vast fissure had opened in the crater, from which fountains of lava were pouring forth.
Later, lava and noxious sulfur dioxide gas began pouring out of vents along the volcano’s northeastern slope and flowing in rivers down the mountain’s gentle slopes.
While authorities on the Big Island have said the lava poses no danger to communities at present, they have issued warnings for ashfall and Pele’s hair, a type of fibrous glass formed when lava is stretched thinly as it cools. Roughly 200,000 people live on the Big Island.
A shield-type volcano, Mauna Loa doesn’t explode like Italy’s Mount Etna or the Philippines’ Mount Pinatubo; instead, its low-silica lava oozes out in effusive eruptions that build a broad mountain. That process is responsible for raising the Hawaiian archipelago above the Pacific seafloor.
Last month, authorities on Hawaii’s Big Island advised residents to prepare a “go bag” in case they needed to evacuate quickly, since there were increasing signs that Mauna Loa would soon erupt. It hasn’t erupted since 1984 and previous eruptions haven’t posed much of a threat to human settlement, but the largest city, Hilo, is partly built on a lava flow from a 19th century eruption.
By comparison, Mauna Loa’s smaller neighbor of Kilauea has persistently erupted for years at a time and posed a much greater danger to human settlement.
According to local news reports, more than 300 flights have been delayed because of the eruption.