Lava oozing out of cracks for two weeks in rural Hawaii neighborhoods took on new characteristics as fresher magma mixed with decades-old magma, sending a flow toward the ocean Saturday.
By Saturday morning, two of 22 fissures had merged, creating a wide flow advancing at rates of up to 300 yards (274 metres) per hour.
The flow was 1.5 miles (2.4 kilometres) from the ocean, scientists said.
According to Wendy Stovall, a US Geological Survey volcanologist, the fountains are created by vents closing, forcing magma to burst through a single outpoint.
Since a first fissure opened in a community on May 3, lava was mostly spattering up and collecting at the edges of the cracks in the ground.
Two neighborhoods with nearly 2,000 people were forced to evacuate as lava claimed 40 structures.
On Friday afternoon, the lava changed dramatically with one fissure ramping up and sending a flow across a road, destroying four more homes and isolating residents, some of whom had to be air-lifted to safety.
If lava threatens main highways, more people will be told to prepare for voluntary evacuation.