By Malia Mattoch McManus

HONOLULU (Reuters) - A volcanic lava flow that threatens a subdivision on Hawaii's Big Island has shifted slightly, potentially sparing some homes but increasing the number of residents who may be "lava-locked" if the flow overtakes a highway, a civil defense official said on Tuesday.

The lava flow from the continuously erupting Kilauea volcano is moving through forested terrain toward the Kaohe Homesteads subdivision, and after a recent tack northward could reach nearby Highway 130 within 16 to 18 days, according to Hawaiian Volcano Observatory projections.

"The flow is continuing moving parallel to the subdivision," said Darryl Oliveira, director of Big Island Civil Defense. "There are inconsistencies in the terrain, lots of cracks and features that could influence the flow, so it's difficult to say what will be the progression." 

Scientists had issued a warning to residents last week after lava crept to within a mile (1.6 km) of the outer edge of a forest reserve that sits a tenth of a mile (160 meters) from some of the estimated 30 to 50 homes in the subdivision, and said lava could reach the subdivision within roughly a week.

But more current projections show that slow-moving lava could flow either through the north part of the subdivision, or to the north of it depending on the impact of the terrain, scientists said.

Big Island Mayor Billy Kenoi declared a state of emergency for the area last Thursday, citing potential harm to residents and homes as well as risks posed to roads.

While officials have not ordered an evacuation, authorities have begun restricting subdivision access to residents to ease congestion for those wishing to evacuate voluntarily.

Big Island resident Jerry Konanui, who has been removing equipment and materials from his Kaohe farm, said the projection of a more northerly lava route could mean the flow may bypass his farm, "but we really don't know for sure." 

He worried the new projected path would cut Highway 130 off for even more residents of the Puna area, where Mayor Kenoi said more than 8,000 people would be affected if lava overtakes portions of Highway 130.

Authorities say the further north the lava hits the highway, the more residents would be affected.

The Kilauea volcano has continuously erupted from its Pu’u O’o vent since 1983. The latest lava flow began on June 27.

The last home destroyed by lava on the Big Island was at the Royal Gardens subdivision in Kalapana in 2012, Oliveira said.


(Editing by Cynthia Johnston and Eric Walsh)