The lake on active Bay of Plenty volcano White Island has completely disappeared, a volcanologist has discovered.
The shallow lake was around 3m deep before the water level began dropping on September 24. Two days later it had completely disappeared, leaving only small ponds.
When volcanologist Agnes Mazot visited the island on Friday she also observed other changes.
Most of the gas was coming from only one joined vent at the back of the crater. The gas flow from this vent was stronger and noisier than it had been when it was flowing from more than one vent.
White Island's temperature had dropped from 300C to 250C.
During Friday's visit a team of volcanologists and electronic technicians from GNS Science, and a visiting volcanologist from Vanuatu, serviced some of the remote monitoring gear that had not been working properly. They cleaned ash from solar panels and replaced a camera.
Easterly gales prevented the scientists from reaching the volcano's summit. The wind hindered plans to replace the West Rim camera there or make detailed gas readings.
Last month the volcano had been emitting ash, prompting the volcanic alert to be lifted from level 1 to level 3, which meant there was a minor eruption . The alert was lowered back down to level 1 a few days later.
Friday's findings revealed White Island was no longer releasing ash, but Mazot warned it was "always capable of a new eruption at any time, without any useful warning".
She said the Volcanic Alert Level remained at Level 1 - indicating minor unrest.
GNS volcanologist Brad Scott said the changes observed on Friday were not a cause for concern.
The chance of an eruption was "as likely as normal or weakly stronger than normal".
"It's the status quo."
The lake had evaporated before because of increasing temperatures in the vent, Scott said.
But Friday's findings implied a different cause for its disappearance, because the temperature of the vent was not decreasing, it was likely the water had drained away.