The United States Geological Survey (USGS) posted an aviation red alert for the first time for the Kilauea volcano in Hawaii as explosions intensified on Tuesday. The volcano spewed ash and volcano smog, or vog, as it is known, in the latest activity since the eruption began 12 days ago.

An aviation red alert from the USGS means a volcanic eruption is under way that could spew ash along aircraft routes.

The red alert as defined by the USGS means that an eruption is considered to be "imminent, underway or suspected, with hazardous activity on the ground and in the air.”

Ash and smoke rose to 12,000 feet (3,657 meters) above Kilauea's crater and floated southwest, showering cars on Highway 11 with gray dust and prompting an "unhealthy air" advisory in the community of Pahala, 18 miles (29 km) from the summit.

Ash was also a new hazard for residents of Hawaii's Big Island, who were already grappling with volcanic gas and lava that has destroyed 37 homes and other structures and forced the evacuation of about 2,000 residents.

"We're observing more or less continuous emission of ash now with intermittent, more energetic ash bursts or plumes," Steve Brantley, a deputy scientist in charge at the Hawaiian Volcano Observatory (HVO), said while on a conference call with reporters.

The 2010 eruptions at Icelandic volcano Eyjafjallajökull caused a major volcanic ash cloud that grounded a vast proportion of air travel, especially to and from Europe, in April and May of that year.

A shift in winds was expected to bring ash and fog inland on Wednesday and make them more concentrated said another official with the USGS. The observatory also warned that the eruption could become more violent.

"At any time, activity may become more explosive, increasing the intensity of ash production and producing ballistic projectiles near the vent," the HVO said in a statement on the change in aviation alert level to red from orange.

New fissure reported

Authorities on Tuesday reported a new fissure opened up in the adjoining Lanipuna Gardens subdivision, near Leilani Estates subdivision, bringing the number of cracks in the ground spitting out lava and toxic gas to nearly 20 since the eruption began May 3.

Another fissure that opened up last weekend was sending molten rock crawling toward the ocean at about 20 yards (18 meters) per hour.

A new eruption will cause more havoc to the already belieagured tourism industry

The Hawaiian Volcano Observatory reported that fissures opened just east of the Puna Geothermal Venture energy conversion plant. The plant brings steam and hot liquid up through underground wells and the steam feeds a turbine generator to produce electricity.

Geologists have warned that Kilauea's summit could have an explosive steam eruption that would hurl boulders and ash miles into the sky.

Tourism industry hit

According to Rob Birch, the executive director of the Island of Hawaii Visitor Bureau, island summer hotel bookings have dropped by almost half from last year. He noted that cancellations from May through July have hit at least $5 million.

Tourism is one of Hawaii's major industries and counts for a big part of the local economy and tourism to the Big Island, the site of the volcano grew the fastest last year compared to the other islands.

Most of the Hawaii Volcanoes National Park remains closed due to ongoing seismic activity and the possibility of an explosion at the summit.

So far, no major injuries or deaths have been reported from the eruption.

av/msh (Reuters, AP)

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