TDEM Aerial Geophysical Survey

Image: TDEM Aerial Geophysical Survey

Detailed Description

Suspended 100 feet below the helicopter, a hexagonal-shaped Time Domain Electromagnetic and Magnetic (TDEM) survey instrument collects and records geophysical measurements along the eastern flank of Mount St. Helens. TDEM is an exploration technique in which electric currents are induced in the Earth and the corresponding magnetic field response is measured. The data will be used to map the presence of hydrothermally-altered and water-saturated rocks within the volcano. This analysis is part of an ongoing research program to identify the slip surface of the massive landslide that triggered the historic 1980 eruption. The mapping may also provide information about water-bearing layers that increase the likelihood of future large landslides.


Image Dimensions: 500 x 393

Date Taken:

Location Taken: Mount St. Helens, WA, US