LOS ANGELES - Fountains of lava and rivers of molten rock were spewing from the world's biggest volcano as the first eruption there in almost four decades showed no signs of abating.
Two fissures on Mauna Loa were venting huge volumes of viscous rock and gases from deep within the Earth, in a thunderous display of the power of nature.
Vulcanologists said they were watching lava flows heading towards a highway on Hawaii's largest island, though they still believe the eruption, which began Sunday, posed no immediate threat to humans.
"The Northeast Rift Zone eruption of Mauna Loa continues, with two active fissures feeding lava flows downslope," the United States Geological Survey (USGS) said.
"Fissure 3 remains the dominant source of the largest lava flow. The fissure 3 lava flows are travelling to the north toward the Daniel K. Inouye Highway (Saddle Road) but have reached relatively flatter ground and have slowed down significantly as expected."
The molten rock was travelling at around 40 metres per hour and was still a few kilometres from the road.
"Advance rates may be highly variable over the coming days and weeks due to the way lava is emplaced on flat ground," the USGS said.
"At the rate observed over the past 24 hours, the earliest the lava flow might be expected to reach the Daniel K. Inouye Highway (Saddle Road) is one week."
But, the agency warned, volcanoes can be unpredictable and these calculations could change.
The other fissure still producing lava is sending it northeast, while plumes of volcanic gas were lofting high into the air and Pele's Hair was falling to earth.
Pele's Hair is fine strands of volcanic glass formed when lava skeins cool quickly in the air.
Scientists say their seismic monitoring equipment was detecting a large number of earthquakes around the two active fissures.
"This indicates that magma is still being supplied, and activity is likely to continue as long as we see this signal," the USGS said.
Pressure has been building at Mauna Loa for years, but it has not erupted since 1984.