Tracking Subsurface Water

Jeff Wynn, Herb Pierce and Chris Lockett (R to L) observe the incoming data used to measure water conductivity in the deep (900+ m) subsurface at Mount St. Helens. Water, from rain, melting snow and ice, seeps into the rubble of the crater floor. The water fills the pore spaces and interacts with still hot lava to become strongly acidic. This study uses Controlled-Source-Audio-Magnetotellurics (CSAMT) to follow the trail of the highly conductive subsurface water. These types of baseline measurements are invaluable for determining how rock can be weakened by water saturation and hydrothermal alteration.