Global Volcanism Program | Image GVP-03435
Among the many monitoring techniques used by Hawaiian Volcano Observatory staff at Kilauea volcano is precision leveling. Millimeter-scale changes can be detected with an optical-level instrument by measuring the precise difference in elevation on leveling rods placed above two fixed points. Slight changes in the shape of a volcanic edifice commonly occurs prior to eruptions. Measurements such as these in 1968, with the Puʻu ʻŌʻō scoria cone in the background, are one of several techniques used to help forecast eruptive events.
Photo by Richard Fiske, 1986 (Smithsonian Institution).
This image is made available under the Public Domain Dedication CC0 license, but proper attribution is appreciated.