· Scientists measure and record four main types of data when monitoring volcanoes. Trends and variations in these data are key in understanding what a volcano is doing, when a volcano may erupt and how dangerous an eruption may be. These for data sets, and the instruments used to collect them are as follows:
o Temperature: Temperature measurements tell scientists which areas on a volcano are warmer than others which give an idea of where magma may be concentrated within and, therefore, areas susceptible to risk of eruption. Thermal images can be generated from special thermal imaging cameras which can be used from the ground, aircraft or, more recently, from satellites.
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| FLIR thermal image from Santiaguito volcano, Guatemala |
o Gas Emissions: Scientists can measure the composition of gas emitted from volcanoes both directly (by putting instruments into fumaroles) or indirectly using a tool known as COSPEC (Correlation Spectraphotometer) to measure the light refraction properties of gases as they exit a volcano. The emission of SO2 (Sulfur Dioxide gas) as well as CO2 can give indications of where magma may be and if it is rising. This process can be done from light aircraft circling the volcano, from the ground, or from satellite and does not require that scientists take samples on or within the volcano crater itself.
o Deformation: Volcano deformation is useful in telling which parts of a volcano are expanding, signifying the buildup of pressure from fluids, gasses or magma, or contracting, signifying the release of those pressures. This data is collected using myriad instruments. Tiltmeters are ultra-accurate devices which are sensitive to changes is slope, roughly similar to a bubble level. Laser rangefinders fired to previously placed mirrors on a volcano as well as surveying equipment are also ways of measuring volcanic deformation. However, as is the trend, much deformation data is collected using remote sensing, especially ultra-accurate GPS data and satellite generated topography profiles.
o Deformation: Volcano deformation is useful in telling which parts of a volcano are expanding, signifying the buildup of pressure from fluids, gasses or magma, or contracting, signifying the release of those pressures. This data is collected using myriad instruments. Tiltmeters are ultra-accurate devices which are sensitive to changes is slope, roughly similar to a bubble level. Laser rangefinders fired to previously placed mirrors on a volcano as well as surveying equipment are also ways of measuring volcanic deformation. However, as is the trend, much deformation data is collected using remote sensing, especially ultra-accurate GPS data and satellite generated topography profiles.
o Seismic Signals: Seismometers record earthquake events from anywhere on earth. When set up in a pattern surrounding a volcano, seismic readings can indicate whether or not magma is moving beneath the volcano, where it is and the shape of the magma pathways and chamber. Trained volcanologists are able to distinguish certain types of earthquakes with distinct signals to tell whether they were generated by the movement of magma or from a rupture of a fault.
o Direct sampling is sometimes an option for data collection, albeit a dangerous one. Given that such sampling has meant the deaths of many volcanologists over the years, though, direct sampling is becoming less prevalent, being replaced by the many remote sensing options now available.
You can find more detailed explanations here.
You can find more detailed explanations here.
