Understanding the science behind Hawaii’s erupting Kilauea volcano

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When most people think of Hawaii, they envision swaying palm trees, sandy beaches and turquoise surf. But people are now being made aware of just how that tropical paradise was created.

The Big Island of Hawaii is being rocked by an eruption from the massive Kilauea volcano — one of the world’s most active and one of five on the island. It’s eruptions such as these, playing out over thousands of years, that gave rise to the more than 130 islands that make up the Hawaiian archipelago. 

The most recent eruption, which occurred on May 3, has destroyed more than 35 structures to date and forced some 1,700 people to be evacuated from their homes as magma and toxic gases make their way to the surface.

Not your typical volcano

Talk of an erupting volcano typically brings forth a vision of a cloud of ash reaching kilometres into the sky and raining down on the ground below. But that doesn’t apply to Hawaii’s shield volcanoes, which experience “effusive” eruptions. 

A lava flow from the Kilauea volcano moves along a street in Leilani Estates on Sunday. (U.S. Geological Survey handout/Reuters )

Rather than spewing lava and ash explosively and suddenly upward — as Mount St. Helens did in 1980 — effusive eruptions slowly and steadily pour material outward, resulting in the formation of a flattened dome, or shield-like shape, with broad, gently sloping sides.

Decades-long eruption

While the recent activity at Kilauea — the youngest volcano on the island — has grabbed a lot of headlines, it’s actually been erupting off and on for more than 30 years. 

The Pu’u’O’o volcanic vent, located in the Kilauea east rift zone, began erupting in January 1983. Most recently, activity in the crater picked back up in early 2013, with flows continuing until March 2015. 

 In 2014, residents of the town of Pahoa were forced to evacuate as lava advanced from another eruption, causing concern it would cover the community’s main road and cut it off from the rest of the island.

A new fissure erupted Saturday evening, beginning with small lava spattering at about 8:44 p.m. local time. By 9 p.m., lava fountains as high as about 70 metres were erupting from the fissure. (USGS)

With this latest eruption, there are two rift zones — or areas where the volcano is splitting apart — which provide the easiest path for magma to make its way to the surface, when it is then called lava. 

According to the United States Geological Survey (USGS), lava flows from the volcano over the years have covered 125 square kilometres.

Earthquakes

In the weeks leading up to Kilauea’s latest eruption, the region experienced hundreds of earthquakes. Last Friday, a 6.9-magnitude earthquake rocked the Big Island — the strongest since 1975.

According to Tina Neal, the scientist-in-charge of the USGS Hawaiian Volcano Observatory, the earthquakes occur as a result of magma moving along these rift zones, stressing the volcano.

“All of that stress is relieved in large earthquakes,” Neal said during an update last Friday. “In some ways, these are not unexpected.”

She said more earthquakes are expected in the coming days, and could possibly continue for weeks to come.

Fissures and fires

As of Monday, there were at least 10 fissures — linear areas where volcanic activity opens a crack or vent —in the east rift zone, though not all are currently active.

In particular, Kilauea’s eruption opened up a fissure in a subdivision known as Leilani Estates, less than 20 kilometres from the volcano, forcing local residents to flee the 770 homes located there.

Because some of the fissures are new, volcanologists are trying to determine whether this recent activity could lead to a new lava field, which could permanently displace people from their homes.

Fissures, where volcanic activity opens up along a linear crack, can be seen here as the Kilauea volcano erupts on the Big Island of Hawaii. (USGS)

The fissures release steam and gases, like toxic sulfur dioxide. Neal noted these releases are a precursor to magma making its way to the surface.

On the plus side, because there isn’t currently a significant amount of magma, these fissures are only active for hours at a time.

As lava begins to spew out of these fissures, much of what it touches catches fire. The temperature of lava can be more than 1,000 C, though once it begins to flow, it can cool by as fast as hundreds of degrees per second.

But scientists say it is nearly impossible to predict how long the eruption will last; it could be days or months.

http://www.cbc.ca/news/technology/kilauea-volcano-hawaii-1.4651710?cmp=rss

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