Volcaniclastic Sediments from Snow/Ice-Capped Volcanoes: Mount St. Helens and Mount Hood

Volcaniclastic Sediments

Pre-meeting field trip, August 10–13; max/min participants, 45/15

As most field volcanologists already recognize, fragmental deposits emplaced subaerially by primary volcanic processes (pyroclastic density currents and tephra fall), those emplaced by secondary volcano-hydrologic processes (debris avalanches, lahars, and muddy floods), and even those emplaced by alpine glaciers on the flanks of volcanoes, can all look frustratingly similar in outcrop.  This field trip is organized to provide an unusual opportunity for physical volcanologists and volcanic sedimentologists and stratigraphers to visit outcrops spanning nearly the full spectrum of volcaniclastic deposit types, so that the critical and often subtle physical differences among these deposits can be examined, contrasted, and discussed in detail.   Recent eruptions from Mount St. Helens and Mount Hood have provided us an exceptionally large variety of fresh and well-exposed primary and secondary volcaniclastic sediments to examine and photograph.  This field trip should be especially beneficial to those working in terrains where classification and interpretation of volcaniclastic deposits is important for hazard assessment.

We will start at 7:30 am on August 10 from the Oregon Convention Center in Portland, ending at about 4 pm on August 13 at the same location.  A moderate amount of scrambling down river banks is necessary to access outcrops, but no strenuous hiking will be required.  The weather is likely to be warm and sunny, although several stops (and one overnight are at higher elevations, where some warm clothing will be needed).  Be sure to bring sun protection, rain gear (though unlikely to be needed), and sturdy hiking shoes or boots.

Estimated cost: 
Cost is $600.00 USD per person.  This includes transport (by motor coach), accommodation for 3 nights (double or more occupancy per room) with complementary breakfasts in the morning at two of the three hotels, refreshments and lunches en route, all permits and entry fees, and a printed copy of the field trip guide (an online version will be available earlier).  If single occupancy accommodation is desired, this can be arranged at higher cost. 

Tom Pierson, U.S. Geological Survey
Lee Siebert, Smithsonian Institution
Kevin Scott, U.S. Geological Survey
Chris Harpel, U.S. Geological Survey