Image: Theodolite measurement on Ruapehu volcano

Description: New Zealand Geological Survey volcanologist Brad Scott conducts theodolite measurements at the Crater Lake vent in 1988 at the summit of Ruapehu volcano. 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 river valleys below the volcano.
Title: Theodolite measurement on Ruapehu volcano
Credit: http://www.volcano.si.edu/world/tpgallery.cfm
Author: Don Swanson, U.S. Geological Survey
Permission: This image is in the public domain in the United States because it only contains materials that originally came from the United States Geological Survey, an agency of the United States Department of the Interior. For more information, see the official USGS copyright policy.
Usage Terms: Public domain
License: Public domain
Attribution Required?: No