A mudflow on Mt Ruapehu is possible next autumn if the crater lake filled rapidly. The Conservation Department said the crater was 71 per cent full. "If it fills rapidly, however, a breach [there is a low probability] could occur in the autumn of 2003," it says in a paper.
But
it was more likely a spillover could occur in 2004-05.
Eruptions in 1995 and 1996 changed the mountain's crater, including rock blocking the lake's outlet, DoC said. After the lake refilled, it was possible a lahar, or mudflow, would occur. If the rock had not eroded before the lake levels rose, there was likely to be a sudden collapse.
An embankment was constructed in February to prevent overflow on to State Highway 1 and into the Tongariro River catchment, and an early warning system for a lahar had been installed.
