More destructive lava flows could soon hit Hawaii's Big Island as the Kilauea volcano erupts, posing a greater threat than oozing magma that has so far destroyed dozens of homes and forced thousands to flee.
As a lava lake at Kilauea's summit drains inside the volcano, magma is running underground. It could burst to the surface as large, fast-moving and intensely hot lava flows and produce higher levels of toxic gases, Hawaiian Volcano Observatory scientist-in-charge Tina Neal says.
"What will take a turn for the worse in terms of hazard is if hotter, fresher magma makes it to the surface, and that could be what is coming," Neal told a conference call on Friday.
"Once a new batch of hotter, gassier magma makes it to the surface we might see larger, higher eruption rates."
Fifteen large cracks or fissures have opened on the eastern flank of Kilauea since the volcano erupted eight days ago.
The volcanic vents have oozed relatively cool, sluggish magma left over from a similar event in 1955. Fresher magma could now emerge behind it.
Also, Kilauea threatens to begin a series of explosive eruptions within days or weeks that could form huge clouds of volcanic smog, or vog, and hurl boulders as big as small cars.
The national park around Kilauea was off-limits to visitors on Friday for fear the volcano would blow its top in the coming days and hurl ash and boulders kilometres into the air.
"If it goes up, it will come down," said Charles Mandeville, volcano hazards co-ordinator for the US Geological Survey.
"You don't want to be underneath anything that weighs 10 tons when it's coming out at 120 miles an hour (193km/h)."
Geologists expect new lava outbreaks in or around the hard-hit Leilani Estates area in the southeastern Puna district, about 32km south of Hilo, where 27 homes have been destroyed and all 1900 residents have been moved.
While locals contend with lava and gas on the ground, explosions at Kilauea's summit about 40km to the west were dusting communities with ash that irritated eyes and breathing.
Volcanic smog may be blowing hundreds of kilometres from Kilauea, with people on the streets of state capital Honolulu, about 340km northwest on the island of Oahu, complaining it was "very voggy" on Friday.