The U.S. Geological Survey (USGS) issued a new orange "watch" alert for Hawaii's Kilauea volcano on Sunday, warning that the lava flows were increasing in duration and that "another fountaining episode is close" amid an ongoing eruption.

Kilauea is one of the world's most active volcanoes.

"Periodic overflows continue from the south vent. Overnight flows were longer in duration than those seen during the daytime and included low dome fountains," the USGS said in its alert.

"Continued inflation, tremor, glow, and precursory overflows from the vents all indicate that another fountaining episode is close. Overflows from both vents show that magma is standing high in the conduits."

The alert added: "The current eruption has been characterized by episodic lava fountaining not seen in any er

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