Big Island hotel bookings for summer months are off almost 50 percent from last year, Rob Birch, executive director of the Island of Hawaii Visitor Bureau, told journalists on a conference call. (Photo: AP) Pahoa, Hawaii: Explosions intensified on Hawaii&OIL SEAL Manufacturers39;s Kilauea volcano on Tuesday, spewing ash and sparking a red alert for aviation for the first time since the latest eruption began 12 days ago.An aviation red alert means a volcanic eruption is under way that could affect aviation by spewing ash into air routes, according to the US Geological Survey (USGS) website. Lava has burst from the ground and torn through housing developments and farmland, threatening one of the last exit routes from coastal areas, state Highway 132. It can make roads slippery and if emitted in large quantities could cause electrical power lines to fail, said USGS chemist David Damby.Road crews put metal plates over steaming cracks on nearby Highway 130 and reopened it to provide coastal residents an escape route in case a lava flow reaches the ocean and blocks another exit artery, Highway 137, Civil Defense said.

New FissureThe eruption has taken its toll on the island's tourism industry.Ash was also a new hazard for residents of Hawaii's Big Island already dealing with volcanic gas and lava that has destroyed 37 homes and other structures and forced around 2,000 residents to evacuate."We're observing more or less continuous emission of ash now with intermittent, more energetic ash bursts or plumes," said Hawaiian Volcano Observatory (HVO) Deputy Scientist-In-Charge Steve Brantley on a conference call with reporters."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.A looming menace remains the possibility of an "explosive eruption" of Kilauea, an event last seen in 1924.The latest tear in the earth or fissure opened on Tuesday, spewing lava and toxic gases that made air quality "condition red" around Lanipuna Gardens and nearby farms, causing "choking and inability to breathe," the Hawaiian Volcano Observatory and Hawaii County Civil Defense said.