ABSTRACT
A debris flow consisting primarily of volcanic ash and lava boulders. Heavy rain, and melting snow and ice during a volcanic eruption mix with the loose deposits and form fast-moving tongues of slurry, commonly in existing channels. Lahars are one of the most serious hazards associated with ice-covered volcanoes (Figure L.1). Lahar features on the volcano, Ruapehu on North Island, New Zealand. (a) The channels, along which a devastating lahar flowed on 24 December 1953, following an eruption and partial melting of a glacier in the summit crater. (b) The railway bridge at Tangiwai, which was demolished by the lahar, resulting in destruction of a train and a loss of 151 lives. Both images show the aftermath of a more recent, smaller lahar in March 2007. An early warning system installed after the 1953 disaster led to temporary closure of the railway and adjacent road, thus preventing a further accident. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315373157/95d5ad9e-a71d-4f11-a609-2c025b95638b/content/figl_1.jpg"/>
