USGS Multimedia Gallery for Set: Mt. Saint Helens

Volcanic Gas Sampling

cwerner - at - usgs.gov (Cynthia Werner) — Fri, 14 Oct 2011 00:00:00 EDT

Christoph Kern acquires ultraviolet images of volcanic gas over the dome and crater of Mount St. Helens. Although practically invisible to the human eye, sulfur dioxide absorbs ultraviolet light and appears dark in images captured by the equipment. Sulfur dioxide is typically emitted from magma as it approaches the surface, so surveys are conducted on a regular basis at Mount St. Helens and other Cascades volcanoes to determine if magma is on the move. Sulfur dioxide was not detectable during this particular measurement.

Tracking Subsurface Water

lwestby - at - usgs.gov (Liz Westby) — Fri, 14 Oct 2011 00:00:00 EDT

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.

Mapping Glacial Advance

A.T. Barsotti — Fri, 14 Oct 2011 00:00:00 EDT

A geologist finishes field notes after mapping the extent of Crater Glacier at Mount St. Helens. Crater Glacier, formed by the accumulation of snow and rocks falling from the inside of the crater rim and walls, began to deform and flow in 1996. Over the past five years, Crater Glacier's terminus has been advancing at about 30 cm per day. Mapping the glacier's extent and volume are important for assessing lahar hazards. Should the glacial ice and snow be melted swiftly by a future dome-building eruption, a torrent of glacial meltwater could produce a fast-moving flood of water and debris that pours onto the Pumice Plain and possibly down the North Fork Toutle River.

TDEM Aerial Geophysical Survey

lwestby - at - usgs.gov (Liz Westby) — Fri, 14 Oct 2011 00:00:00 EDT

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.