The infrared portion of the spectrum is one of the most useful for identifying what a surface is made of because both reflected and emitted energy can be studied. Reflected infrared energy tells us a lot about rocks and minerals. Measuring the differences in ground temperatures by using infrared satellites shows the distribution of rocks and minerals .
Minerals absorb and emit thermal infrared radiation.
The spectra produced by this infrared radiation acts as fingerprints, identifying minerals and their proportion in an area. Thermal infrared data is used to study volcanoes and predict eruptions by mapping ground temperatures, the composition of lava flows, and the sulfur dioxide in volcanic plumes. This data is very useful when monitoring volcanoes for activity. Infrared detectors onboard satellites and aircraft are used to study the distribution of vegetation and soil and to detect diseased plants before problems become visually apparent. Infrared mapping is also used to evaluate vegetation soil moisture and patterns, for irrigation studies, and for detecting diseased fruit and vegetable crops.