Mapping Glacial Advance

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.