Question

scientists can use infrared waves to monitor volcanoes! they use a device called a spectrometer. heres how it works.
infrared waves emitted from lava are absorbed by volcanic gases. each type of gas absorbs unique wavelengths of infrared waves. a spectrometer positioned above the volcano measures these wavelengths. then, these measurements are used to identify the types of gases emitted by a volcano. monitoring volcanic gases helps scientists predict the likelihood of a volcanic eruption.
spectrometer above the overlook vent in halemaumau crater in hawaii
complete the sentences.
volcanic gases infrared waves that are from lava. a spectrometer measures the of these infrared waves to determine the types of gases emitted by the volcano.

Explanation:

The text states that "Infrared waves emitted from lava are absorbed by volcanic gases" and "A spectrometer...measures these wavelengths". So for the first blank, the action of the volcanic gases is to absorb the infrared waves. For the second blank, the source of the infrared waves is that they are emitted from lava. And for the third blank, the spectrometer measures the wavelengths.

Answer:

Volcanic gases absorb infrared waves that are emitted from lava. A spectrometer measures the wavelengths of these infrared waves to determine the types of gases emitted by the volcano.