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Mauna Loa: What Brews Beneath the Surface?

(KHNL) It's like a giant powder keg poised to explode. And the question isn't a matter of if Mauna Loa will erupt again, but when. And many Hawaii island residents are living in fear.

Kilauea volcano has captured the attention of millions across the world with its on-going eruption. But when it comes to active volcanoes, Hawaii's Mauna Loa poses a big threat because of it's sheer size and huge eruptions. It is a hazard many aren't fully prepared for.

It looked like the creation of the world millions of years ago, as lava poured from the earth. But it was the scene at Mauna Loa just 22 years ago. Already scientists say this volcano is overdue for another eruption.

"The long term average is one eruption every decade" said Frank Trusdell, one of the many geologists who work at the Hawaii Volcanoes Observatory , monitoring and measuring this mountain which looks tranquil and quiet now. But looks can be deceiving.

While Kilauea is visibly active - with steam vents and surface flows - Mauna Loa is most active underground where magma is being injected into this massive volcano. That injection of magma is needed before an eruption, which scientists say is not imminent. But Mauna Loa will erupt again.

"It is building toward another eruption" says Trusdell.

The question is when. Vulcanologists hope to answer that by monitoring and measuring earthquakes underneath the volcano.

"We know that just before large eruptive events we see 2-3 earthquakes per minute" said Jim Kauakikaua of the USGS Hawaiian Volcano Observatory.

Geologists are also keeping an eye on gas emissions and ground swelling.

"As magma is being injected into the volcano, it will have to expand to accommodate that."

Scientists also know that historically Mauna Loa eruptions follow the same pattern.

"The initial part of the eruption will be lava fountains, usually several tens of meters high. They will feed very large lava flows, very fast moving lava flows" said Kauakikaua.

Scientists don't know where that lava will go during an eruption, leaving many on the big island with big worries as they live with an active volcano.

"What's going to happen?" asks Kaumana resident Michelle Icari.

"Is it going to follow the same path?  How much faster is it going to get there? Will my house be taken away? Are we going to lose everything?"

Volcano footage copyright Jay Harada, available from volcanovideo.com