Global Volcanism Program | Image GVP-01623
New Zealand volcanologist Brad Scott conducts theodolite (detecting height changes) measurements at Ruapehu’s Crater Lake in 1988. Measurements of the lake height, temperature, and chemistry are made routinely, and along with seismic instrumentation, are used to help forecast future activity of the volcano. Intermittent steam explosions from beneath the lake have produced lahars, which have damaged ski facilities on the upper flanks and structures in valleys below the volcano.
Photo by Don Swanson, 1984 (U.S. Geological Survey).