Scientists visited Monday the crater lake of Mt Ruapehu where a dam of volcanic ash and debris collapsed, sending a four-metre (13-foot) high wall of water, ash, rocks and trees cascading into the countryside below.

No one was reported hurt and there was little damage from Sunday's deluge, known as a lahar.

Government scientists reported Monday that the lake was stable after the soft dam covering the rim of the crater lake had been swept away.

The unstable dam had been created by eruptions of the 2,797-metre Mt Ruapehu in 1995 and 1996 and an emergency plan had been in place for years to deal with the expected lahar.

The Department of Conservation said no further lahars were expected following Monday's examination of the crater lake.

DOC senior conservation officer Dave Wakelin said staff had been up to the crater and the dam of loosely compacted ash and volcanic rock had completely disappeared.

"It's great news from our point of view,' he said. "Now we have a crater lake back to what it was pre-1995. It's flowing down its natural outlet, rather than building up behind the dam."

The lahar had long been expected and an early warning system allowed authorities to close roads and a railway line in the path of the lahar.

The lack of casualties and damage was in contrast to a similar lahar on Christmas Eve 1953, which killed 151 train passengers when a rail bridge was swept away.

Sunday's lahar followed the path of the Whangaehu river, taking huge boulders and trees with it in a three to four-metre high wave.

The deluge lasted about three hours and the Department of Conservation said worse damage may have been avoided because the dam collapsed in stages.

related report
Indonesia Ups Alert Level On Sumatra Volcano Jakarta (AFP) Mar 20 - Indonesia has raised the alert level for Mount Talang on Sumatra island following increased smoke and tremors, a vulcanologist said Monday.

"The status was raised on March 17 at 7:00 pm," said Dalifa Marjusi from the local vulcanology office.

Marjusi said increased activity has been reported from the peak of the 2,597-metre (8,673 foot) high volcano in West Sumatra province, prompting the rise to three of four possible levels.

"The smoke is reaching heights of up to 800 metres (2,672 feet)," he told AFP.

He said local Solok district authorities were immediately notified of the rise. A coordination meeting was held on Sunday night with district authorities to prepare for a possible eruption should the alert level reach four.

The Solok district chief, Gusmal, told AFP some 41,000 people may need to be evacuated from the slope of the mountain should an eruption prove imminent.

"There is yet no plan to evacuate them, but we are now preparing in case the alert status is raised," Gusmal said.

More than 25,000 residents were evacuated in April 2005 from the slopes of Mount Talang as the volcano heightened its rumbling and spewed volcanic ash.

Indonesia sits on the so-called "Pacific Ring of Fire", where continental plates meet and cause frequent volcanic and seismic activity.

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