A Bay of Plenty resident has described her fear after waking to the sound of a "geyser" of water shooting 20m to 30m in the air from Lake Rotorua.
Ohinemutu resident Lani Kereopa was woken by the loud noise about 4am today and said it sounded like "a big thump and spraying sound afterwards".
Ms Kereopa said growing up in the pa she was used to geothermal activity, but had never experienced something "on this scale".
"Twenty-five metres from my house a geyser was erupting out of the lake. I stood up, looked out the window...it was pitch black and I was thinking nothing much looks different even though it was dark.
"Then another one happened and I saw water spraying up out of the lake.
"I panicked and ran downstairs to wake everyone up to say get out of the house, the village is erupting."
Ms Kereopa said she woke her family and they all drove up a nearby hill to shine the lights down on the lake to try to see what was going on. She said she wasn't sure what to do, or whether to wake up the rest of the village.
"It looked like Pohutu Geyser but with a lot more water."
GNS today confirmed the hydrothermal eruption, with duty volcanologist Brad Scott describing it as unusual.
Mr Scott said the last significant steam eruptions in Rotorua were about 15 years ago, and they were not sure why it had happened again.
There had been several reports of the eruption from people living in the village. Mr Scott had been down to Ohinemutu this morning, but was unable to identify the site, and said conditions weren't favourable for taking a boat out.
The hydrothermal eruptions were common during the time the geothermal system was exploited heavily, but this was "much more of a natural event", he believed.
Rotorua Lakes Council geothermal inspector Peter Brownbridge said the eruption was nothing to worry about, although it was noisy and spectacular because of the geyser effect.
"Hydrothermal eruptions happen reasonably regularly in that area of the lake edge but they more often than not just cause a bit of bubbling up of water and mud from the lake bottom, rather than creating a geyser like this morning's one did.
"We don't see many bigger ones these days although eruptions like this were quite common about eight years ago," Mr Brownbridge said.
The eruption was reported initially to Bay of Plenty Regional Council and, when contacted, Mr Brownbridge reported it to GNS, as is routine.
"There's nothing we can do, but we'll keep an eye on things and people can contact us if they have any concerns."
