Mount St. Helens---Recent and ancient volcaniclastic processes and deposits

Mt St Helens

Pre-meeting field trip, August 7–12 August; max/min participants, 20/10

This field trip circumnavigates Mount St. Helens to examine superb exposures of eruption deposits from throughout the volcano’s history. On this trip, we emphasize eruptive processes and deposits from the cataclysmic 1980 eruption (debris avalanche, ‘lateral blast’, lahar, tephra fall), but also examine deposits from eruptions as old as 20 ka (tephra falls, lahars, pyroclastic flows). We touch upon the Oligocene–Miocene rocks underlying the region and several Pleistocene glaciations that shaped nearby valleys. The trip focuses on deposit character and depositional process, how the modern 1980 deposits are linked to specific volcanic processes, and how well we can infer details of volcanic process in ancient deposits. We also delve into socioeconomic and management aspects of prolonged landscape response to a large and devastating eruption. The trip begins on the northeast side of the volcano and works clockwise, concluding with a visit to Johnston Ridge, with spectacular views, directly north of the volcano. Most stops will be along roads, but each day there will be a moderate hike along trails and minor scrambling off trails. Each hike could be a couple of hours duration, cover round trip distances to a few km, and entail elevation gains of a couple hundred meters. We return each evening to a hotel.

The trip will depart from Portland International Airport or a nearby hotel (a list will be sent to participants) by 1:00 p.m. on Monday, 7 August, and end at the Oregon Convention Center by evening of Saturday, 12 August.

Estimated cost:
$900, includes transportation, double-occupancy lodging, breakfast, lunch, snacks, 2 to 3 dinners, and entrance fee to the Mount St. Helens National Volcanic Monument. Participants must cover their own dinner costs the other nights as well as incidentals.

Richard Waitt, U.S. Geological Survey
Jon Major, U.S. Geological Survey
Alexa Van Eaton, U.S. Geological Survey
Richard Hoblitt, U.S. Geological Survey