5 Big Questions About Hawaii's Volcanoes

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. 

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

Mauna Loa is the world’s biggest active volcano. It covers more than half of the Big Island. It has erupted 34 times since 1843. The most recent event was in 1984. But 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. 

It may sound surprising, but Hawaii’s eight main islands are actually the tops of giant undersea volcanoes. Tens of millions of years ago, magma 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. 

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

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.

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. They also have gentle slopes that formed as lava built up and spread out over time. They’re called shield volcanoes. That’s 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.

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.

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. They also 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. This is called “vog” for short. Vog can cause headaches and sore throats. It can also make it hard for some people to breathe. 

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 volcanologist 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.”

Scientists monitor Hawaii’s active volcanoes around the clock. They look for signs that the volcanoes 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 volcanologist at the U.S. Geological Survey. She says scientists get up close to erupting volcanoes. They 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.”

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?

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?