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Types and Processes Gallery - Volcano Monitoring

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.

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).

The seismogram for 15 June 1991 shows the intense seismicity accompanying the catastrophic eruption of Mount Pinatubo in the Philippines. This seismic record shows earthquakes over a two-hour period beginning at 0508 hours. The arrow points to the earthquake accompanying a major explosion at 0555, which was preceded by long-period earthquakes. At about 0640 continuous overlapping long-period earthquakes or tremor began, and much of the following record was saturated so that individual earthquakes could not be distinguished.

Photo by Ed Wolfe, 1991 (U.S. Geological Survey).

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 Klyuchevskoy volcano in 1983. Geochemical analysis of lava samples is used to understand the eruption dynamics and the magmatic history of the volcano. Eruptions of flank and summit lava flows are common here. Protective clothing is always needed when working on active volcanoes, but sampling at lava flows such as this is rare.

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

An Alaska Volcano Observatory geologist uses a laser-surveying instrument to measure precise distances to targets installed on the flanks of Redoubt. Minute changes in distances to the targets can reflect ground deformation that may indicate magma movement or other processes. Steam rises above a lava dome in the crater of Redoubt in this photo taken on 5 May 1990, near the end of an eruption that had begun the previous December.

Photo by Game McGimsey, 1990 (Alaska Volcano Observatory, U.S. Geological Survey).

An Alaska Volcano Observatory geologist sets up GPS (Global Positioning System) instrumentation on the N flank of Redoubt volcano. The GPS receiver calculates an extremely accurate location through satellite-based triangulation. This helps pinpoint locations for electronic distance measurements that detect deformation that may be related to eruptive activity. The Drift River valley extending away from the volcano to the NE was covered with pyroclastic-flow and mudflow deposits from the 1989-90 eruption.

Photo by Game McGimsey, 1991 (Alaska Volcano Observatory, U.S. Geological Survey).

Seismometers such as this one installed near Mount Spurr volcano (on skyline in background) provide the Alaska Volcano Observatory with a continuous, telemetered record of volcanic earthquakes. Scientists use this data to monitor earthquake types, locations, and magnitudes to decipher different processes under and within a volcano.

Photo by Christina Neal, 1993 (Alaska Volcano Observatory, U.S. Geological Survey).

St. Helens
U.S. Geological Survey scientists make precision leveling measurements in the crater of Mount St. Helens in February 1982 with the steaming lava dome in the background. Repeated measurements of deformation was one of several methods used by scientists to successfully forecast later eruptions from the crater.

Photo by Terry Leighley, 1982 (U.S. Geological Survey).

Scientists from the U.S. Geological Survey take gas samples at Devils Kitchen near the Crater Rock lava dome on the upper SW flank of Mount Hood. The Crater Rock area produces vigorous gas emission and results in extensive hydrothermal alteration of rock masses over broad areas.

Photo by Bill Chadwick, 1982 (U.S. Geological Survey).

Three Sisters
Electronic Distance Measurements (EDM) by the U.S. Geological Survey at South Sister volcano, with Middle Sister to the left, are conducted routinely to monitor these Cascades volcanoes for potential eruptive activity. By measuring the distance between two fixed points, these instruments can detect minor changes in the surface of the volcanic edifice that can occur prior to eruptions.

Photo by Lyn Topinka, 1985 (U.S. Geological Survey).

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 penetrated to 60 m depth 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 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).

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 distance between the two points is made by a small computer in the EDM instrument. These measurements allow scientists to detect inflation or deflation of the volcano due to changes in the magmatic or hydrothermal systems.

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

Scientists use a COSPEC (Correlation Spectrometer) instrument to measure the sulfur dioxide (SO2) content of a volcanic plume from Fuego volcano in Guatemala. Measuring the amount 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).