The low altitude and tight line spacing results in a high resolution survey. This means that smaller areal extent magnetic anomalies can be seen in the resulting grid. Instead of picking up general patterns of magnetic anomalies, we can resolve variable magnetization within the edifice. In particular, magnetic lows associated with alteration can be observed. We reduced the observed magnetic data to the pole, a technique that attempts to account for the inclination of the Earth's magnetic field.
Blue colors represent lows caused by topography and demagnetized volcanic rock.
The transmitter and receiver coils in the EM bird measure the electromagnetic response of the ground at different frequencies to obtain information from different depths. The raw data is processed to produce apparent resistivity maps. The deepest that the lowest frequency EM data can penetrate the surface at Mt. Rainier is about 150 m beneath the ice. Unlike the magnetic data, the EM is not very influenced by topography. Altered volcanic rocks produce lows on resistivity maps, whereas fresh volcanic rocks produce highs.