Where will Hawaii’s largest volcano erupt from?

HONOLULU (AP) – The ground shakes and swells at Mauna Loa, the largest active volcano in the world, indicating it may erupt. Scientists say they don’t expect it to happen right away, but officials on the Big Island of Hawaii are telling residents to be prepared in case it erupts soon. Here are some things to know about the volcano.


Mauna Loa is one of the five volcanoes that together make up the Big Island of Hawaii, which is the southernmost island of the Hawaiian archipelago. It is not the tallest (this title goes to Mauna Kea) but it is the largest and makes up about half of the island’s land mass.

It is located immediately north of the Kilauea volcano, which is currently erupting from its summit crater. Kilauea is known for a 2018 eruption that destroyed 700 homes and sent rivers of lava that spread across farms and into the ocean.

The Mauna Loa last erupted 38 years ago. In written history, dating back to 1843, it has erupted 33 times.

The Big Island is predominantly rural and is home to cattle ranches, coffee farms, and beach clubs. It is located approximately 200 miles (320 kilometers) south of Hawaii’s most populous island, Oahu, where the state capital Honolulu and the beach resort Waikiki are located.


The eruptions of Mauna Loa differ from those of Kilauea in part because it is higher. Its greater height gives it steeper slopes, which allow lava to rush down its hills faster than that of Kilauea.

Its huge size could allow it to store more magma, leading to larger lava flows when an eruption occurs.

Frank Trusdell, a research geologist at the Hawaiian Volcano Observatory, which is part of the US Geological Survey, said the data indicates that Mauna Loa has a much larger magma reservoir than Kilauea, which could allow it to hold more lava and rest. longer between eruptions than in Kilauea.


Scientists won’t know until the eruption begins. Every eruption since 1843 began at the summit. Half the time, the volcano later also began to erupt from the vents at lower elevations. The other half of the time it erupted only in the summit caldera.

Scientists can’t say much in advance when and where Mauna Loa will open new vents and explode.

Vents generally form along the volcano’s rift zone. This is where the mountain is cracking, the rock is cracked and relatively weak, and magma is more likely to emerge.

An eruption from the vents in the southwestern rift zone could affect residential communities, coffee plantations, or coastal villages on the western side of the island. Lava could reach homes in hours or days.

The most populous city on the west side would be protected from any Mauna Loa eruption by the presence of another active volcano. The wide flanks of that volcano, Hualalai, lie between the southwestern rift zone of Mauna Loa and Kailua-Kona and would block any lava heading towards the coastal community.

An eruption from the northeastern rift zone could send lava towards the county seat of Hilo or other cities in eastern Hawaii. It may take weeks or months to reach the populated areas on this side of the mountain.

Scott Rowland, a geologist at the University of Hawaii at Manoa, said there are no patterns when it comes to where an eruption will occur.

“Just because the last one was in the northeast rift zone doesn’t mean the next one will be along the southwest rift zone,” he said.


Fifty-seven people died when Mount St. Helens, Washington state erupted in 1980 and detonated more than 1,300 feet (400 meters) from the mountain’s summit. Steam, rocks and volcanic gases explode upwards and outwards. A plume of volcanic ash rose over 80,000 feet (24,384 meters) and rained up to 250 miles (400 kilometers) away.

Hawaii’s volcanoes like Mauna Loa tend not to have explosive eruptions like this one.

This is because their magma is hotter, drier, and more fluid, said Hannah Dietterich, a research geophysicist at the Alaska Volcano Observatory of the US Geological Survey.

The magma in Mount St. Helens tends to be more viscous and traps more gas, making it much more likely to explode as it rises.

Gas in the magma of Hawaii’s volcanoes tends to escape, and therefore lava flows down the side of their mountains when they erupt.

The volcanoes of Hawaii are called shield volcanoes because successive lava flows over the course of hundreds of thousands of years create large mountains that resemble the shape of a warrior’s shield.

Shield volcanoes are also found in California and Idaho, as well as Iceland and the Galapagos Islands. Wrangell-St. Elias National Park has eight shield volcanoes, including Mount Wrangell.

Volcanoes such as Monte Sant’Elena are called composites or stratovolcanoes. Their steep conical slopes are built by the eruption of viscous lava flows and rock, ash and gas. Mount Fuji in Japan is another example of a composite volcano.


The Hawaiian Volcano Observatory has more than 60 GPS stations on Mauna Loa that take measurements to estimate the location and amount of magma that builds up beneath the surface.

Scientists use incline meters to track long-term changes in terrain inclination, helping them identify when terrain is swelling or deflating. A rapid change in inclination can indicate when a rash will occur.

There is also a thermal webcam on the summit of Mauna Loa which will identify the presence of heat. And satellite radar can track swelling and deflation of the terrain.


Associated Press writer Mark Thiessen contributed to this report from Anchorage, Alaska.

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