08 November 2007
Location
Mt Ruapehu, Central Plateau, North Island, New Zealand
Information
Mt Ruapehu has a summit plateau which consists of several craters covered under a central glacier. The active vent contains a crater lake. Is is about 400 m wide, 600 m deep and contains highly acidic water, up to 600C warm. The lake drains through an ice cave just off the tip of the wing. The temperature and color changes all the time. The color ranges from green to muddy grey, and earlier this century the water sometimes had frozen or even disappeared.
From time to time, steam explosions (phreatic eruptions) cause hot water to spill over the flanks. Note that the peak on the right (Pyramid Peak) has no snow on it. The water melts snow and ice and carries rocks with it. These so called lahars pose a danger on skiiers on a nearby skyfield. Early this century, a lahar carried away the train bridge at Tangiwai. Some minutes later the Express Wellington/Auckland plunged into the river, and 153 people were killed. Today, an automatic warning system has been installed which warns Skiiers on the Whakapapa Ski Field and stops trains on threatened routes.
In the background you see the single cone of Mt Ngauruhoe
Mt Ruapehu from the West
Zeinab Ahmed