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5 Big Questions About Hawaii's Volcanoes

The Mauna Loa (MOW-nah LOH-uh) volcano erupted last fall for the first time in nearly 40 years. Here’s what you need to know about Hawaii’s volcanoes. 

As You Read, Think About: How do volcanoes affect people in Hawaii? 

1. What happened at Mauna Loa?

On November 27, lava began spewing like a fountain from the volcano on what is known as the Big Island of Hawaii. The fiery liquid shot up to 200 feet into the air, giving the sky an eerie red glow. For about two weeks, streams of lava as hot as 2,000 degrees Fahrenheit oozed down the volcano’s northeast side. 

The world’s biggest active volcano, Mauna Loa covers more than half of the Big Island. It has erupted 34 times since 1843. The most recent was in 1984, though there’s been a lot of volcanic activity on the island since then. The nearby Kilauea (kee-lah-WAY-ah) volcano has erupted on and off for decades. 

2. Why are there so many eruptions in Hawaii? 

It may sound surprising, but Hawaii’s eight main islands are actually the tops of giant undersea volcanoes. Tens of millions of years ago, began to burst through an area on the ocean floor called a hot spot. As the lava cooled, it hardened into rock. The eruptions continued, creating mountains that eventually rose above the surface of the ocean to form the Hawaiian Islands. 

Map showing the locations of different volcanoes in Hawaii

Jim McMahon/Mapman®

Hawaii is the name of both the state and the biggest of the state’s eight main islands.

3. What do Hawaii’s volcanoes look like? 

When you picture a volcano, you might imagine a cone-shaped mountain that sends a huge cloud of ash and lava towering into the sky. Hawaii’s volcanoes are different. They’re wider and flatter, with gentle slopes that formed as lava built up and spread out over time. They’re called shield volcanoes because they resemble a warrior’s shield lying flat on the ground. When shield volcanoes erupt, lava tends to flow out slowly. During last fall’s eruption, lava from Mauna Loa crawled at a rate of about 40 to 20 feet per hour.

4. Does that mean Hawaii’s volcanoes aren’t dangerous?

Not necessarily. Lava from Mauna Loa’s recent eruption wasn’t a threat to any of the Big Island’s 200,000 residents. But past eruptions in Hawaii have caused major destruction. In 2018, for example, lava flows from Kilauea destroyed more than 700 homes and caused about $800 million in damage. The volcano spewed enough lava to fill 320,000 Olympic-sized swimming pools.

In addition, eruptions often blanket nearby communities in a haze of volcanic smog—called “vog” for short. Vog can cause headaches and sore throats and make it hard for some people to breathe.

5. How can scientists keep Hawaiians safe? 

Scientists monitor Hawaii’s active volcanoes around the clock, looking for signs that they might roar back to life. For example, experts expected Mauna Loa to erupt last fall. For months, they had noticed more earthquakes within the volcano. That was one of the signs that magma deep underground was rising toward the surface. 

Wendy Stovall is a at the U.S. Geological Survey. She says scientists get up close to erupting volcanoes—and even scoop up lava samples to analyze. “That can help us understand more about how volcanoes behave,” she explains, “so we can forecast eruptions in a better way in the future.”

Photo of a scientist monitoring a volcano

USGS

A scientist monitors the Kilauea eruption in 2021. 

1. What are shield volcanoes, and why did they get this name?

2. Did the fall 2022 eruption of Mauna Loa surprise scientists? Explain.

3. What dangers can Hawaii’s volcanoes present?

Image of a person who studies volcanoes wearing a special protection suit
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volcanologist

noun

a scientist who studies volcanoes

 

The volcanologist traveled through Africa to study different volcanoes.

Illustrated diagram showing the different parts of a volcano
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magma

noun

molten (melted) rock beneath Earth’s surface; it flows out of volcanoes as lava

 

Magma rises from deep within Earth through the vents, or openings, of a volcano.

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