Bigger Than ’95, Smaller Than Tangiwai

Yesterday’s lahar on Mt Ruapehu has been described as bigger than the lahar that followed Ruapehu’s 1995 eruption but smaller than the destructive Tangiwai lahar of 1953 that claimed 151 lives.

Scientists who visited the crater lake at the summit of Mt Ruapehu this morning have confirmed that the tephra dam did completely collapse, and the normal lake outlet has been eroded down to the rock rim. This seems to have occurred in at least two stages yesterday.

The lahar passing down the Whangaehu River was captured at regular intervals by a webcam operated by Horizons Regional Council. Quick thinking by a New Zealand weather enthusiast who runs the Hamilton Weather website meant that a lengthy series of images from the camera were captured allowing them to be assembled as an animated gif (graphic interchage format) file.

The sequence of images shows the lahar flow rising up and riding over the Railway Lahar Sensor Tower north of Tangiwai as the 5.3 metre lahar passed through between 12:39 and 13:40 on Sunday the 18th of March 2007.

Dial-up users should note that the file is large (about 4.5 MByte) and could take 20 or more minutes to download, depending on your connection speed.

Thanks to “Foggy Hamilton” for agreeing to the link and congratulations to Horizons Regional Council for the foresight in placing the camera.

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