Types and Processes Gallery

Volcano Monitoring
Volcanologists use a variety of monitoring techniques to keep tabs on the "health" of a volcano in order to forecast future eruptions and provide warning to those living in proximity to volcanoes. Traditional monitoring techniques involving seismic instrumentation, ground-deformation measurements, gas monitoring, and gravity and magnetic measurements have been applied for many years. Recent advances in modeling and laboratory experiments have improved interpretation of monitoring data, and recent technological advances have incorporated data from satellite observations, global positioning system (GPS) measurements, and synthetic apeture radar (SAR) interferometry. Successful eruption forecasts have been possible when officials decide to commit resources to scientific study and monitoring, but many of the world's volcanoes lack adequate funding and monitoring.

Scientists use a COSPEC (Correlation Spectraphotometer) instrument to measure the sulfur dioxide (SO2) content of a volcanic plume from Fuego volcano in Guatemala. Measurements of the concentrations of SO2 and other gases in volcanic plumes are useful tools for eruption monitoring. This photo of Dick Stoiber (left) and Gary Malone (standing) was taken by Tom Crafford from Finca Capetillo NE of Fuego during its October 1974 eruption.

Copyrighted photo by Dick Stoiber, 1974 (Dartmouth College).

A Hawaiian Volcano Observatory team uses a drilling rig to extract drill core from the cooling lava lake in Kilauea Iki crater. At the time of this 1968 project, nearly a decade after a lava lake filled Kilauea Iki during the 1959 eruption, the crust had solidified to a depth of about 30 m. The drill core reached down to 60 m without reaching the bottom of the still partially molten lava lake. This project, the first to use a drill rig to sample a lava lake, allowed study of vertical variations in chemistry, mineralogy, and temperature within a cooling lava lake.

Photo by Jean Tobin, 1968.

Among the many monitoring techniques used by Hawaiian Volcano Observatory staff at Kilauea volcano is precision leveling. Millimeter-scale variations in the elevation of two fixed points can be detected with an optical-level instrument by measuring the precise difference in elevation on leveling rods placed above them. Slight inflation of a volcanic edifice commonly occurs prior to eruptions. Measurements such as these in 1968, with the Puu O'o cinder cone in the background, are one of several techniques used to help forecast eruptive events.

Photo by Richard Fiske, 1986 (Smithsonian Institution).

A volcanologist from the Institute of Volcanology in Petropavlovsk, shielded from the intense heat in a reflective suit, extracts a glowing sample of lava from a flank vent of Kliuchevskoi volcano in 1983. Geochemical analysis of lava samples is used to characterize the eruption and understand the magmatic history of the volcano. Eruptions of flank and summit lava flows are common at this basaltic stratovolcano.

Photo by A. Ozerov, 1983 (courtesy of Yuri Doubik, Institute of Volcanology, Petropavlovsk).

Mauna Loa
Hawaiian Volcano Observatory scientists conduct an electronic-distance measurement (EDM) survey on the rim of Kilauea caldera in 1988, with snow-capped Mauna Loa in the background. The procedure uses a laser beam, which is reflected back to the EDM instrument from a distant cluster of reflectors. A precise determination of the horizontal distance between the two points is made by a small computer in the EDM instrument. These measurements allow scientists to detect inflation of the volcano as magma rises to the surface prior to an eruption.

Photo by J.D. Griggs, 1988 (U.S. Geological Survey).