Part of White Terraces discovered

The Pink and White Terraces were submerged after the eruption of Mount Tarawera in 1886. Photo / Supplied

Scientists who found part of the famed Pink Terraces in Lake Rotomahana in January have also found remnants of the White Terraces on the lake floor.

The find comes from side-scan sonar data of the lake floor collected on the last day of the 10-day project at Lake Rotomahana last summer.

Using new software the scientists found the sonar data contained images of hard, crescent-shaped structures in a similar location to where the White Terraces were before Mt Tarawera erupted on 10 June 1886, burying both the Pink and White Terraces.

The structures are at roughly 60m depth - a similar depth to the remnants of the Pink Terraces, which were found in January. Project leader Cornel de Ronde, of GNS Science, said the sonar images from Lake Rotomahana showed the lake floor was covered overwhelmingly by soft sediment and mud.

"The sonar image that appears to show part of the White Terraces came to light after the project had finished. It shows a horizontal segment of terraces over 100 meters long, although we don't know which part of the terraces it is.

"The rounded terrace edges are standing up from the lake floor by about a metre in some places. The sonar images of both sets of terraces are strikingly similar."

Scientists managed to capture several colour photographs of part of the Pink Terraces in January, but they did not lower an underwater camera over the White Terraces location during the project as they were unaware of what the sonar data was showing at the time.

The fate of the remaining sections of the Pink and White Terraces is unclear. They might have been destroyed in the eruption or could be lying under thick sediment.

Dr de Ronde said finding remnants of both sets of terraces was a remarkable outcome for the project. Before the eruption the two sets of cascading silica terraces, several hundred metres apart, were New Zealand's premier tourist attraction.

"Finding part of what we believe is the White Terraces as well has been surprising and very satisfying."

The original aim of the Lake Rotomahana project was to map the lake floor and investigate the extensive geothermal system under the lake. Anything else was a bonus, he said.

"It's gratifying to be part of a science project that can answer a century-old mystery about the fate of the Pink and White Terraces."

Dr de Ronde said the announcement of the find was timed to coincide with the 125th anniversary of Mt Tarawera's eruption. An hour-long television documentary about the project at Lake Rotomahana is scheduled to screen on Prime at 8.30pm this Sunday.

- NZPA