A stream of lava is blocking a Hawaii highway serving as an escape route for coastal residents, while the first known serious injury has been reported from fresh explosive eruptions from the Kilauea volcano.

A home owner on a third-floor balcony had his leg shattered from shin to foot when hit by lava spatter, said Janet Snyder, a spokesperson for the Office of the Mayor, County of Hawaii.

As magma destroyed four more homes, molten rock from two huge cracks merged into a single stream, threatening to block other escape routes and touching off brush fires.

The erupting lava, which can reach a blistering 1100 C, crossed Highway 137 shortly before midnight local time, Hawaii’s Civil Defense Agency said, and sent lava flowing into the ocean.

That prompted warnings of laze – clouds of hydrochloric acid and steam embedded with fine glass particles formed when hot lava hits ocean water.
Authorities were trying on Sunday to open up a road blocked by lava in 2014 to serve as an alternative escape route, Jessica Ferracane of the National Park Service said.

Converging rivers of molten rock roll irresistibly towards the doomed home in the lower right corner. Photo: EPA

The park service is working to bulldoze almost a mile of hardened lava out of the way on nearby Highway 11, which has been impassable, she added.

The Hawaii National Guard has warned of mandatory evacuations if more roads become blocked.

But officials went house-to-house in the area to urge more residents to flee, Ms Snyder said, though no head count of the new evacuation was available early Sunday.

For weeks, geologists have warned that hotter, fresher magma from Kilauea’s summit would run underground and emerge some 40 kilometres east in the lower Puna district, where older, cooler lava has already destroyed 44 homes and other structures.

“Summit magma has arrived,” US Geological Survey scientist Wendy Stovall said on a conference call with reporters.

“There is much more stuff coming out of the ground and its going to produce flows that will move much further away.”

Fountains of bright orange lava were seen spouting at least 6 metres high and spewing rivers of molten rock on Saturday.

Carolyn Pearcheta, operational geologist at the Hawaii Volcano Authority, told reporters hotter and more viscous lava could be on the way, with fountains spurting as high as 180 metres, as seen in a 1955 eruption.

-AAP