The scene of destruction at Tangiwai 1953

It was Christmas Eve and 285 people were aboard the Wellington-Auckland express travelling home for Christmas. The train was keeping good time as it passed through Waiouru and approached the bridge that carried the line over the Whangaehu river at Tangiwai, 10km from Waiouru.

In the distance was Mount Ruapehu, an active volcano of some 9000 feet. Of those travelling that night, few would have given it a second thought for it had not erupted since 1948. However deep within the mountain, the forces of nature were at work. A lake had formed in its crater creating a huge weight of water. Forces created within the mountain caused the water to find a sudden exit in cave beneath the Whangaehu glacier. As the massive flow of water left the mountain it gathered volcanic ash and lumps of ice. As it proceeded along the river valley it collapsed the valley sides and collected silt and boulders and other debris forming a massively destructive lahar.

It swept down the valley and completely overwhelmed the bridge ahead of the train. The fourth pier was demolished and the fifth damaged. The postmaster from the town of Taihape saw the damage to the bridge and attempted to warn the approaching train by running along the track waving a torch. It is probable that the driver saw his frantic efforts to avert disaster as subsequent examination of the locomotive showed that the brakes had been applied.

The locomotive and six coaches plunged through the gap in the bridge and into the raging torrent below. Such was the force of the lahar that one of the carriages was carried for a distance of 5 miles and some bodies were found 30 miles away. A total of 151 people, including the driver died.

As a consequence of this disaster and in an attempt to avoid a similar disaster in the future detection equipment was installed some way upstream of the Tangiwai bridge in the bed of the Wangaehu river.

In 1957 the Tangiwai National Memorial was erected in Karori Cemetry. In 1989 another memorial was erected at the site of the disaster.

Lahar: A torrential flow of water-saturated volcanic debris down the slope of a volcano in response to gravity. A type of mudflow.
from Volcano World