Orange flashes are lighting up Bay of Plenty skies tonight as White Island continues to erupt.
Ash from the volcano has drifted as far as Tauranga's coastline, and has coated homes and cars along Papamoa beach.
GNS Science volcanologist Mike Rosenberg told the Herald the crater lake on White Island was drying out, which was causing less water to be pulled into the ash cloud. That was creating static which was being discharged as lightening.
"We're getting reports of big orange plumes and all sorts. It's a natural, typical phenomenon in ash cloud. It is not a sign of increasing activity, it doesn't mean there's been a big eruption ... it's blowing at the same intensity as it has been over the last few days.''
Authorities had been monitoring the volcano, which is about 51km north of Opotiki, since a series of eruptions began this week.
Scientists flew over the island for the first time today and confirmed it was erupting.
Black ash was rising up to 3000m above the active vent on the southwest corner of the crater.
It was the first ash emission from White Island since February 2001 and represented the start of a new phase of volcanic activity at White Island, GNS said.
Volcanologist Brad Scott said visitors to the uninhabited island were now at the highest level of risk since the end of the 2001 eruptions. Explosive eruptions could happen at any time with little or no warning.
Robyn Keereweer, a shop assistant at Papamoa Four Square and Lotto shop, said she would have to wash her car when she got home, as it had been sprinkled with ash.
"There's a very light bit of ash on my car bonnet. It's sort of whitey-grey. But when I put my finger on it, it disintegrates.''
Meanwhile, a potentially toxic chemical has been detected in ash from Monday night's hydrothermal eruption of Mt Tongariro.
Seismic activity in the area has been low since the blast, with only a few small volcanic earthquakes recorded.
Analysis of the ashfall by Massey University has found moderate levels of potentially toxic fluorine.
Professor Shane Cronin said because of the restricted distribution and very thin ashfall it posed no threat to human health or agriculture beyond the immediate vicinity of the volcano.
However, if larger eruptions of Mt Tongariro occurred, a significant agricultural hazard could be expected, he said.
"Ashfall can impact pastoral grazing systems by covering pasture, meaning that it is ingested by grazing sheep, cattle and deer.
Drinking water in open troughs, used by livestock, may be contaminated, he said.
The soluble fluorine in the ash was similar to ash from Mt Ruapehu when it erupted in 1995 and 1996.
Mr Rosenberg said analysis of the ash also found there was very little, or no, new magma in it.
"This suggests that the [Tongariro] eruption was predominantly steam driven, but the involvement of magma in the future cannot be ruled out,'' he said.
- APNZ, NZ HeraldBy Hana Garrett-Walker Email Hana