Objects 
                that are hot emit a lot of energy, which a satellite's infrared 
                sensors can detect and record. The hotter the object the brighter 
                it appears on the image. Before a volcano erupts it usually has 
                increased thermal activity which appears as elevated surface temperatures 
                (hot spots) around the volcano's crater. Early detection of a 
                "hot spot" and monitoring is a key factor in predicting 
                possible volcanic eruptions.