Fast lava from Hawaii's erupting Kilauea volcano closes highway

Fast-moving lava from Hawaii's Kilauea volcano forced officials to close part of a highway on Tuesday, and they warned that sharp, thin strands of volcanic glass fibres carried by the wind could injure eyes and lungs.

As lava crossed Highway 132, officials shut a stretch of road from Lava Tree State Park to Four Corners and told residents who had not evacuated to leave the area immediately.

The lava flow destroyed a farm where Kevin Hopkins and partners raise tropical fish and the ornamental carp known as koi.

"It just came over and ate the farm, boiled the water out of the ponds," Hopkins said.

Earlier on Tuesday, a small explosion of ash erupted from the summit of the volcano in a vertical plume some 4,600 metres high, the U.S. Geological Survey said, the latest outburst in a month of volcanic activity.

The agency warned that ash was drifting northwest and liable to affect anyone in the summit area. Hundreds of people have been ordered to leave the vicinity of one of the world's most active volcanoes in its biggest eruption cycle in a century.

Kilauea entered its fourth week of what may be an unprecedented, simultaneous eruption at its summit crater and along a 9.7-kilometre string of fissures 40 kilometres down its east flank.

Lava flows from multiple fissures have blocked roads and damaged dozens of buildings on Hawaii's Big Island.

Lava has also destroyed more than 400 electric poles and other equipment, causing power outages, the Hawaii Electric Light utility reported. It is unclear how many homes and businesses were without power.

Occasional earthquakes

Officials are on high alert for occasional earthquakes, though most have been small.

Lava has engulfed the heads of two wells that tap into steam and gas deep into the earth at the 38-megawatt Puna Geothermal Venture electrical plant, which used to produce a quarter of the Big Island's electricity. Its operator, Israeli-controlled Ormat Technologies Inc., said it had not been able to assess the damage.

After weeks of scientific updates on the volcano, the U.S. Geological Survey took a lighter tone as it responded to a question on Twitter about whether it would be safe to roast marshmallows over volcanic vents.

"We're going to have to say no, that's not safe," the agency's volcanos account replied Monday, saying if the vent was belching volcanic gases, such as sulfur dioxide or hydrogen sulfide, the roasted marshmallows "would taste bad." The gases generally smell like rotten eggs.

So far no deaths have been blamed on the eruption, though a man's leg was shattered when he was hit by a plate-size chunk of lava rock.

Residents fear the electrical plant's deep geothermal wells may be explosive. Officials have said the power plant is safe but lava has never engulfed a geothermal plant anywhere in the world, creating a measure of uncertainty.

Contingency plans have been made for a possible helicopter evacuation of up to 1,000 residents in a coastal area south of the fissures should their last exit route, State Highway 130, become blocked by lava or become unsafe due to gaping cracks, County of Hawaii officials said.

At least 82 homes have been destroyed in the southeastern corner of the Big Island and about 2,000 people have been been forced to leave since Kilauea began erupting on May 3.