HONOLULU (AP) — Lava shoots 100 feet to 200 feet (30 to 60 meters) into the air as Hawaii’s Mauna Loa, the world’s largest active volcano, erupts for the first time in nearly 40 years.
At this time, lava is not threatening homes or communities, and no evacuation orders have been issued. Lava could eventually reach neighborhoods as it flows downhill, although it could take a week or more for molten rock to reach populated areas.
Mauna Loa emits sulfur dioxide and other volcanic gases. They form volcanic smog, or vog, when they mix with vapor, oxygen, and dust in sunlight. As a result, state health officials are asking people to limit outdoor exercise and other activities that cause heavy breathing.
Mauna Loa last erupted in 1984. Its smaller, more active neighbor, Kilauea Volcano, has been erupting continuously for more than a year since September 2021.
WHERE IS MAUNA LOA?
Mauna Loa is one of five volcanoes that together make up the Big Island of Hawaii, which is the southernmost island in the Hawaiian archipelago. It’s not the tallest (that title goes to Mauna Kea), but it’s the tallest, making up about half of the island’s landmass.
It is just north of the Kilauea volcano, known for a 2018 eruption that destroyed 700 homes and spread lava flows across farms and into the ocean.
Mauna Loa last erupted 38 years ago. The current eruption is the 34th since recorded history began in 1843.
Mostly rural, the Big Island is home to cattle ranches and coffee farms, but is also home to a few small towns, including the county seat of Hilo, which has a population of 45,000.
It is about 200 miles (320 kilometers) south of Hawaii’s most populous island of Oahu, home to both the state capital Honolulu and the beach resort town of Waikiki.
Mauna Loa’s volume is estimated to be at least 75,000 square kilometers, making it the largest volcano in the world measured from the sea floor to its summit.
WHERE DOES MAUNA LOA COME FROM?
The eruption began at its summit on Sunday evening after a series of large earthquakes. It then propagated to vents formed in a rift zone where the mountain splits open and magma can escape more easily.
These vents are on the northeast side of the mountain, and the lava that emanates from them could flow towards Hilo, which is on the east side of the island.
Ken Hon, senior scientist at the Hawaiian Volcano Observatory, said he doesn’t expect additional vents to form in the volcano’s southwest rift zone during this eruption. That means communities to the west would be spared from lava flows this time.
Mauna Loa also erupted from the northeast in 1984. Back then, lava was moving toward Hilo, but stopped a few miles from the city.
Historically, each Mauna Loa eruption has lasted a few weeks. Hon expects the current eruption to follow this pattern.
EXPLODES MAUNA LOA LIKE MOUNT ST. HELEN?
Mauna Loa does not explode like Mount St. Helens, Washington, did in 1980, which killed 57 people. This eruption caused ash to rise over 80,000 feet (24,384 meters) and rain as far as 250 miles (400 kilometers) away.
The magma in Mount St. Helens tends to be stickier and traps more gas, making it much more likely to explode as it rises. They are a type of composite volcanoes that form concave cones.
Mauna Loa’s magma tends to be hotter, drier, and more fluid. This allows the gas from the magma to escape and allows lava to flow down the side of the volcano as it is now beginning. Mauna Loa is a shield volcano, so named because the long, broad flanks formed by repeated lava flows give it the appearance of a warrior’s shield.
In 1989, Alaska’s Redoubt Volcano, another composite volcano, belched an 8-mile ash plume that plugged all four engines of a KLM Royal Dutch Airlines jet. The plane fell 13,000 feet before all engines restarted and the plane landed without injuring the 245 people on board.
Mauna Loa released some ash this time, but on a far smaller scale than these examples of composite volcanoes.
WHAT ARE THE HAZARDS OF THE MAUNA LOA OUTBREAK?
-Lava: Molten rock could cover homes, farms, or neighborhoods depending on where it flows. But lava from the northeast rift zone will likely take at least a week to reach settled areas, giving people time to evacuate if necessary.
-Volcano Gas: Mauna Loa releases volcanic gases, primarily sulfur dioxide. The gases are present in their highest concentration in the immediate vicinity of the summit crater or vents. But they also combine with other particles to form Vog, which can spread across the Big Island and even cross to the other islands in the state.
Vog can cause burning eyes, headaches and sore throats in healthy people. It can send people to the hospital with asthma or other breathing problems.
-Glass Particles: When hot lava erupts from a fissure and cools rapidly, it forms glass particles called Pele’s Hair and Pele’s Tears, after the Hawaiian goddess of volcanoes.
The particles typically don’t travel far from volcanic eruptions — maybe just a few hundred meters or a mile, and don’t threaten many people, said Aaron Pietruszka, an associate specialist in the University of Hawaii’s Department of Earth Sciences.
“It literally looks like strands of hair. And there the liquid lava is stretched by the wind into long, thin strands,” says Pietruszka.
The pieces of glass – as short as a few millimeters or as long as a few centimeters – can be sharp.
“You don’t want to bury your hands in it because you could cut yourself,” Pietruszka said.
An N95 or KF94 mask would protect against these glass particles but not volcanic gas, said Dr. Libby Char, the director of the state health department.
Specimens of “Peles Hair” from the Kilauea Volcano eruption can be seen in Hawaii Volcanoes National Park.
HOW IMPORTANT ARE MAUNA LOA’S GREENHOUSE GAS EMISSIONS?
Mauna Loa released about 15,000 tons of carbon dioxide per day during its 1984 eruption, according to USGS data.
That corresponds to the annual emissions of 2,400 sport utility vehicles.
Scientists say that all of the world’s volcanoes combined emit less than 1 percent of the carbon dioxide that humans produce each year.
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